mcs/mcs/ecore.cs

   1 //
   2 // ecore.cs: Core of the Expression representation for the intermediate tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Copyright 2001, 2002, 2003 Ximian, Inc.
   9 // Copyright 2003-2008 Novell, Inc.
  10 // Copyright 2011-2012 Xamarin Inc.
  11 //
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16 using System.Text;
  17 using SLE = System.Linq.Expressions;
  18 using System.Linq;
  19
  20 #if STATIC
  21 using IKVM.Reflection;
  22 using IKVM.Reflection.Emit;
  23 #else
  24 using System.Reflection;
  25 using System.Reflection.Emit;
  26 #endif
  27
  28 namespace Mono.CSharp {
  29
  30         /// <remarks>
  31         ///   The ExprClass class contains the is used to pass the
  32         ///   classification of an expression (value, variable, namespace,
  33         ///   type, method group, property access, event access, indexer access,
  34         ///   nothing).
  35         /// </remarks>
  36         public enum ExprClass : byte {
  37                 Unresolved      = 0,
  38
  39                 Value,
  40                 Variable,
  41                 Namespace,
  42                 Type,
  43                 TypeParameter,
  44                 MethodGroup,
  45                 PropertyAccess,
  46                 EventAccess,
  47                 IndexerAccess,
  48                 Nothing,
  49         }
  50
  51         /// <remarks>
  52         ///   This is used to tell Resolve in which types of expressions we're
  53         ///   interested.
  54         /// </remarks>
  55         [Flags]
  56         public enum ResolveFlags {
  57                 // Returns Value, Variable, PropertyAccess, EventAccess or IndexerAccess.
  58                 VariableOrValue         = 1,
  59
  60                 // Returns a type expression.
  61                 Type                    = 1 << 1,
  62
  63                 // Returns a method group.
  64                 MethodGroup             = 1 << 2,
  65
  66                 TypeParameter   = 1 << 3,
  67
  68                 // Mask of all the expression class flags.
  69                 MaskExprClass = VariableOrValue | Type | MethodGroup | TypeParameter,
  70         }
  71
  72         //
  73         // This is just as a hint to AddressOf of what will be done with the
  74         // address.
  75         [Flags]
  76         public enum AddressOp {
  77                 Store = 1,
  78                 Load  = 2,
  79                 LoadStore = 3
  80         };
  81
  82         /// <summary>
  83         ///   This interface is implemented by variables
  84         /// </summary>
  85         public interface IMemoryLocation {
  86                 /// <summary>
  87                 ///   The AddressOf method should generate code that loads
  88                 ///   the address of the object and leaves it on the stack.
  89                 ///
  90                 ///   The `mode' argument is used to notify the expression
  91                 ///   of whether this will be used to read from the address or
  92                 ///   write to the address.
  93                 ///
  94                 ///   This is just a hint that can be used to provide good error
  95                 ///   reporting, and should have no other side effects.
  96                 /// </summary>
  97                 void AddressOf (EmitContext ec, AddressOp mode);
  98         }
  99
 100         //
 101         // An expressions resolved as a direct variable reference
 102         //
 103         public interface IVariableReference : IFixedExpression
 104         {
 105                 bool IsHoisted { get; }
 106                 string Name { get; }
 107                 VariableInfo VariableInfo { get; }
 108
 109                 void SetHasAddressTaken ();
 110         }
 111
 112         //
 113         // Implemented by an expression which could be or is always
 114         // fixed
 115         //
 116         public interface IFixedExpression
 117         {
 118                 bool IsFixed { get; }
 119         }
 120
 121         public interface IExpressionCleanup
 122         {
 123                 void EmitCleanup (EmitContext ec);
 124         }
 125
 126         /// <remarks>
 127         ///   Base class for expressions
 128         /// </remarks>
 129         public abstract class Expression
 130         {
 131                 public ExprClass eclass;
 132                 protected TypeSpec type;
 133                 protected Location loc;
 134
 135                 public TypeSpec Type {
 136                         get { return type; }
 137                         set { type = value; }
 138                 }
 139
 140                 public virtual bool IsSideEffectFree {
 141                         get {
 142                                 return false;
 143                         }
 144                 }
 145
 146                 public Location Location {
 147                         get { return loc; }
 148                 }
 149
 150                 public virtual bool IsNull {
 151                         get {
 152                                 return false;
 153                         }
 154                 }
 155
 156                 //
 157                 // Used to workaround parser limitation where we cannot get
 158                 // start of statement expression location
 159                 //
 160                 public virtual Location StartLocation {
 161                         get {
 162                                 return loc;
 163                         }
 164                 }
 165
 166                 public virtual MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
 167                 {
 168                         //
 169                         // Return method-group expression when the expression can be used as
 170                         // lambda replacement. A good example is array sorting where instead of
 171                         // code like
 172                         //
 173                         //  Array.Sort (s, (a, b) => String.Compare (a, b));
 174                         //
 175                         // we can use method group directly
 176                         //
 177                         //  Array.Sort (s, String.Compare);
 178                         //
 179                         // Correct overload will be used because we do the reduction after
 180                         // best candidate was found.
 181                         //
 182                         return null;
 183                 }
 184
 185                 //
 186                 // Returns true when the expression during Emit phase breaks stack
 187                 // by using await expression
 188                 //
 189                 public virtual bool ContainsEmitWithAwait ()
 190                 {
 191                         return false;
 192                 }
 193
 194                 /// <summary>
 195                 ///   Performs semantic analysis on the Expression
 196                 /// </summary>
 197                 ///
 198                 /// <remarks>
 199                 ///   The Resolve method is invoked to perform the semantic analysis
 200                 ///   on the node.
 201                 ///
 202                 ///   The return value is an expression (it can be the
 203                 ///   same expression in some cases) or a new
 204                 ///   expression that better represents this node.
 205                 ///
 206                 ///   For example, optimizations of Unary (LiteralInt)
 207                 ///   would return a new LiteralInt with a negated
 208                 ///   value.
 209                 ///
 210                 ///   If there is an error during semantic analysis,
 211                 ///   then an error should be reported (using Report)
 212                 ///   and a null value should be returned.
 213                 ///
 214                 ///   There are two side effects expected from calling
 215                 ///   Resolve(): the the field variable "eclass" should
 216                 ///   be set to any value of the enumeration
 217                 ///   `ExprClass' and the type variable should be set
 218                 ///   to a valid type (this is the type of the
 219                 ///   expression).
 220                 /// </remarks>
 221                 protected abstract Expression DoResolve (ResolveContext rc);
 222
 223                 public virtual Expression DoResolveLValue (ResolveContext rc, Expression right_side)
 224                 {
 225                         return null;
 226                 }
 227
 228                 //
 229                 // This is used if the expression should be resolved as a type or namespace name.
 230                 // the default implementation fails.
 231                 //
 232                 public virtual TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
 233                 {
 234                         var rc = mc as ResolveContext ?? new ResolveContext (mc);
 235                         Expression e = Resolve (rc);
 236                         if (e != null)
 237                                 e.Error_UnexpectedKind (rc, ResolveFlags.Type, loc);
 238
 239                         return null;
 240                 }
 241
 242                 public static void ErrorIsInaccesible (IMemberContext rc, string member, Location loc)
 243                 {
 244                         rc.Module.Compiler.Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", member);
 245                 }
 246
 247                 public void Error_ExpressionMustBeConstant (ResolveContext rc, Location loc, string e_name)
 248                 {
 249                         rc.Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
 250                 }
 251
 252                 public void Error_ConstantCanBeInitializedWithNullOnly (ResolveContext rc, TypeSpec type, Location loc, string name)
 253                 {
 254                         rc.Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
 255                                 name, type.GetSignatureForError ());
 256                 }
 257
 258                 protected virtual void Error_InvalidExpressionStatement (Report report, Location loc)
 259                 {
 260                         report.Error (201, loc, "Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement");
 261                 }
 262
 263                 public void Error_InvalidExpressionStatement (BlockContext bc)
 264                 {
 265                         Error_InvalidExpressionStatement (bc.Report, loc);
 266                 }
 267
 268                 public void Error_InvalidExpressionStatement (Report report)
 269                 {
 270                         Error_InvalidExpressionStatement (report, loc);
 271                 }
 272
 273                 public static void Error_VoidInvalidInTheContext (Location loc, Report Report)
 274                 {
 275                         Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
 276                 }
 277
 278                 public virtual void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
 279                 {
 280                         Error_ValueCannotBeConvertedCore (ec, loc, target, expl);
 281                 }
 282
 283                 protected void Error_ValueCannotBeConvertedCore (ResolveContext ec, Location loc, TypeSpec target, bool expl)
 284                 {
 285                         // The error was already reported as CS1660
 286                         if (type == InternalType.AnonymousMethod)
 287                                 return;
 288
 289                         if (type == InternalType.ErrorType || target == InternalType.ErrorType)
 290                                 return;
 291
 292                         if (type.MemberDefinition.DeclaringAssembly.IsMissing ||
 293                                 target.MemberDefinition.DeclaringAssembly.IsMissing)
 294                                 return;
 295
 296                         string from_type = type.GetSignatureForError ();
 297                         string to_type = target.GetSignatureForError ();
 298                         if (from_type == to_type) {
 299                                 from_type = type.GetSignatureForErrorIncludingAssemblyName ();
 300                                 to_type = target.GetSignatureForErrorIncludingAssemblyName ();
 301                         }
 302
 303                         if (expl) {
 304                                 ec.Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
 305                                         from_type, to_type);
 306                                 return;
 307                         }
 308
 309                         ec.Report.DisableReporting ();
 310                         bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
 311                         ec.Report.EnableReporting ();
 312
 313                         if (expl_exists) {
 314                                 ec.Report.Error (266, loc,
 315                                         "Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
 316                                         from_type, to_type);
 317                         } else {
 318                                 ec.Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
 319                                         from_type, to_type);
 320                         }
 321                 }
 322
 323                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, MemberSpec member, Location loc)
 324                 {
 325                         // Better message for possible generic expressions
 326                         if (member != null && (member.Kind & MemberKind.GenericMask) != 0) {
 327                                 var report = context.Module.Compiler.Report;
 328                                 report.SymbolRelatedToPreviousError (member);
 329                                 if (member is TypeSpec)
 330                                         member = ((TypeSpec) member).GetDefinition ();
 331                                 else
 332                                         member = ((MethodSpec) member).GetGenericMethodDefinition ();
 333
 334                                 string name = member.Kind == MemberKind.Method ? "method" : "type";
 335                                 if (member.IsGeneric) {
 336                                         report.Error (305, loc, "Using the generic {0} `{1}' requires `{2}' type argument(s)",
 337                                                 name, member.GetSignatureForError (), member.Arity.ToString ());
 338                                 } else {
 339                                         report.Error (308, loc, "The non-generic {0} `{1}' cannot be used with the type arguments",
 340                                                 name, member.GetSignatureForError ());
 341                                 }
 342                         } else {
 343                                 Error_TypeArgumentsCannotBeUsed (context, ExprClassName, GetSignatureForError (), loc);
 344                         }
 345                 }
 346
 347                 public static void Error_TypeArgumentsCannotBeUsed (IMemberContext context, string exprType, string name, Location loc)
 348                 {
 349                         context.Module.Compiler.Report.Error (307, loc, "The {0} `{1}' cannot be used with type arguments",
 350                                 exprType, name);
 351                 }
 352
 353                 public virtual void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
 354                 {
 355                         Error_TypeDoesNotContainDefinition (ec, loc, type, name);
 356                 }
 357
 358                 public static void Error_TypeDoesNotContainDefinition (ResolveContext ec, Location loc, TypeSpec type, string name)
 359                 {
 360                         ec.Report.SymbolRelatedToPreviousError (type);
 361                         ec.Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
 362                                 type.GetSignatureForError (), name);
 363                 }
 364
 365                 public virtual void Error_ValueAssignment (ResolveContext rc, Expression rhs)
 366                 {
 367                         if (rhs == EmptyExpression.LValueMemberAccess || rhs == EmptyExpression.LValueMemberOutAccess) {
 368                                 // Already reported as CS1612
 369                         } else if (rhs == EmptyExpression.OutAccess) {
 370                                 rc.Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
 371                         } else {
 372                                 rc.Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
 373                         }
 374                 }
 375
 376                 protected void Error_VoidPointerOperation (ResolveContext rc)
 377                 {
 378                         rc.Report.Error (242, loc, "The operation in question is undefined on void pointers");
 379                 }
 380
 381                 public static void Warning_UnreachableExpression (ResolveContext rc, Location loc)
 382                 {
 383                         rc.Report.Warning (429, 4, loc, "Unreachable expression code detected");
 384                 }
 385
 386                 public ResolveFlags ExprClassToResolveFlags {
 387                         get {
 388                                 switch (eclass) {
 389                                 case ExprClass.Type:
 390                                 case ExprClass.Namespace:
 391                                         return ResolveFlags.Type;
 392
 393                                 case ExprClass.MethodGroup:
 394                                         return ResolveFlags.MethodGroup;
 395
 396                                 case ExprClass.TypeParameter:
 397                                         return ResolveFlags.TypeParameter;
 398
 399                                 case ExprClass.Value:
 400                                 case ExprClass.Variable:
 401                                 case ExprClass.PropertyAccess:
 402                                 case ExprClass.EventAccess:
 403                                 case ExprClass.IndexerAccess:
 404                                         return ResolveFlags.VariableOrValue;
 405
 406                                 default:
 407                                         throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
 408                                 }
 409                         }
 410                 }
 411
 412                 //
 413                 // Implements identical simple name and type-name resolution
 414                 //
 415                 public Expression ProbeIdenticalTypeName (ResolveContext rc, Expression left, SimpleName name)
 416                 {
 417                         var t = left.Type;
 418                         if (t.Kind == MemberKind.InternalCompilerType || t is ElementTypeSpec || t.Arity > 0)
 419                                 return left;
 420
 421                         // In a member access of the form E.I, if E is a single identifier, and if the meaning of E as a simple-name is
 422                         // a constant, field, property, local variable, or parameter with the same type as the meaning of E as a type-name
 423
 424                         if (left is MemberExpr || left is VariableReference) {
 425                                 var identical_type = rc.LookupNamespaceOrType (name.Name, 0, LookupMode.Probing, loc) as TypeExpr;
 426                                 if (identical_type != null && identical_type.Type == left.Type)
 427                                         return identical_type;
 428                         }
 429
 430                         return left;
 431                 }
 432
 433                 public virtual string GetSignatureForError ()
 434                 {
 435                         return type.GetDefinition ().GetSignatureForError ();
 436                 }
 437
 438                 public static bool IsNeverNull (Expression expr)
 439                 {
 440                         if (expr is This || expr is New || expr is ArrayCreation || expr is DelegateCreation || expr is ConditionalMemberAccess)
 441                                 return true;
 442
 443                         var c = expr as Constant;
 444                         if (c != null)
 445                                 return !c.IsNull;
 446
 447                         var tc = expr as TypeCast;
 448                         if (tc != null)
 449                                 return IsNeverNull (tc.Child);
 450
 451                         return false;
 452                 }
 453
 454                 protected static bool IsNullPropagatingValid (TypeSpec type)
 455                 {
 456                         switch (type.Kind) {
 457                         case MemberKind.Struct:
 458                                 return type.IsNullableType;
 459                         case MemberKind.Enum:
 460                         case MemberKind.Void:
 461                         case MemberKind.PointerType:
 462                                 return false;
 463                         case MemberKind.InternalCompilerType:
 464                                 return type.BuiltinType == BuiltinTypeSpec.Type.Dynamic;
 465                         case MemberKind.TypeParameter:
 466                                 return !((TypeParameterSpec) type).IsValueType;
 467                         default:
 468                                 return true;
 469                         }
 470                 }
 471
 472                 public virtual bool HasConditionalAccess ()
 473                 {
 474                         return false;
 475                 }
 476
 477                 protected TypeSpec LiftMemberType (ResolveContext rc, TypeSpec type)
 478                 {
 479                         var tps = type as TypeParameterSpec;
 480                         if (tps != null && !(tps.IsReferenceType || tps.IsValueType)) {
 481                                 Error_OperatorCannotBeApplied (rc, loc, "?", type);
 482                         }
 483
 484                         return TypeSpec.IsValueType (type) && !type.IsNullableType ?
 485                                 Nullable.NullableInfo.MakeType (rc.Module, type) :
 486                                 type;
 487                 }
 488
 489                 /// <summary>
 490                 ///   Resolves an expression and performs semantic analysis on it.
 491                 /// </summary>
 492                 ///
 493                 /// <remarks>
 494                 ///   Currently Resolve wraps DoResolve to perform sanity
 495                 ///   checking and assertion checking on what we expect from Resolve.
 496                 /// </remarks>
 497                 public Expression Resolve (ResolveContext ec, ResolveFlags flags)
 498                 {
 499                         if (eclass != ExprClass.Unresolved) {
 500                                 if ((flags & ExprClassToResolveFlags) == 0) {
 501                                         Error_UnexpectedKind (ec, flags, loc);
 502                                         return null;
 503                                 }
 504
 505                                 return this;
 506                         }
 507
 508                         Expression e;
 509                         try {
 510                                 e = DoResolve (ec);
 511
 512                                 if (e == null)
 513                                         return null;
 514
 515                                 if ((flags & e.ExprClassToResolveFlags) == 0) {
 516                                         e.Error_UnexpectedKind (ec, flags, loc);
 517                                         return null;
 518                                 }
 519
 520                                 if (e.type == null)
 521                                         throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());
 522
 523                                 return e;
 524                         } catch (Exception ex) {
 525                                 if (loc.IsNull || ec.Module.Compiler.Settings.BreakOnInternalError || ex is CompletionResult || ec.Report.IsDisabled || ex is FatalException ||
 526                                         ec.Report.Printer is NullReportPrinter)
 527                                         throw;
 528
 529                                 ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
 530                                 return ErrorExpression.Instance;        // TODO: Add location
 531                         }
 532                 }
 533
 534                 /// <summary>
 535                 ///   Resolves an expression and performs semantic analysis on it.
 536                 /// </summary>
 537                 public Expression Resolve (ResolveContext rc)
 538                 {
 539                         return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
 540                 }
 541
 542                 /// <summary>
 543                 ///   Resolves an expression for LValue assignment
 544                 /// </summary>
 545                 ///
 546                 /// <remarks>
 547                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 548                 ///   checking and assertion checking on what we expect from Resolve
 549                 /// </remarks>
 550                 public Expression ResolveLValue (ResolveContext ec, Expression right_side)
 551                 {
 552                         int errors = ec.Report.Errors;
 553                         bool out_access = right_side == EmptyExpression.OutAccess;
 554
 555                         Expression e = DoResolveLValue (ec, right_side);
 556
 557                         if (e != null && out_access && !(e is IMemoryLocation)) {
 558                                 // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
 559                                 //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,
 560
 561                                 //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
 562                                 //                                e.GetType () + " " + e.GetSignatureForError ());
 563                                 e = null;
 564                         }
 565
 566                         if (e == null) {
 567                                 if (errors == ec.Report.Errors) {
 568                                         Error_ValueAssignment (ec, right_side);
 569                                 }
 570                                 return null;
 571                         }
 572
 573                         if (e.eclass == ExprClass.Unresolved)
 574                                 throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");
 575
 576                         if ((e.type == null) && !(e is GenericTypeExpr))
 577                                 throw new Exception ("Expression " + e + " did not set its type after Resolve");
 578
 579                         return e;
 580                 }
 581
 582                 public Constant ResolveLabelConstant (ResolveContext rc)
 583                 {
 584                         var expr = Resolve (rc);
 585                         if (expr == null)
 586                                 return null;
 587
 588                         Constant c = expr as Constant;
 589                         if (c == null) {
 590                                 if (expr.type != InternalType.ErrorType)
 591                                         rc.Report.Error (150, expr.StartLocation, "A constant value is expected");
 592
 593                                 return null;
 594                         }
 595
 596                         return c;
 597                 }
 598
 599                 public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
 600                 {
 601                         if (Attribute.IsValidArgumentType (parameterType)) {
 602                                 rc.Module.Compiler.Report.Error (182, loc,
 603                                         "An attribute argument must be a constant expression, typeof expression or array creation expression");
 604                         } else {
 605                                 rc.Module.Compiler.Report.Error (181, loc,
 606                                         "Attribute constructor parameter has type `{0}', which is not a valid attribute parameter type",
 607                                         targetType.GetSignatureForError ());
 608                         }
 609                 }
 610
 611                 /// <summary>
 612                 ///   Emits the code for the expression
 613                 /// </summary>
 614                 ///
 615                 /// <remarks>
 616                 ///   The Emit method is invoked to generate the code
 617                 ///   for the expression.
 618                 /// </remarks>
 619                 public abstract void Emit (EmitContext ec);
 620
 621
 622                 // Emit code to branch to @target if this expression is equivalent to @on_true.
 623                 // The default implementation is to emit the value, and then emit a brtrue or brfalse.
 624                 // Subclasses can provide more efficient implementations, but those MUST be equivalent,
 625                 // including the use of conditional branches.  Note also that a branch MUST be emitted
 626                 public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
 627                 {
 628                         Emit (ec);
 629                         ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
 630                 }
 631
 632                 // Emit this expression for its side effects, not for its value.
 633                 // The default implementation is to emit the value, and then throw it away.
 634                 // Subclasses can provide more efficient implementations, but those MUST be equivalent
 635                 public virtual void EmitSideEffect (EmitContext ec)
 636                 {
 637                         Emit (ec);
 638                         ec.Emit (OpCodes.Pop);
 639                 }
 640
 641                 //
 642                 // Emits the expression into temporary field variable. The method
 643                 // should be used for await expressions only
 644                 //
 645                 public virtual Expression EmitToField (EmitContext ec)
 646                 {
 647                         //
 648                         // This is the await prepare Emit method. When emitting code like
 649                         // a + b we emit code like
 650                         //
 651                         // a.Emit ()
 652                         // b.Emit ()
 653                         // Opcodes.Add
 654                         //
 655                         // For await a + await b we have to interfere the flow to keep the
 656                         // stack clean because await yields from the expression. The emit
 657                         // then changes to
 658                         //
 659                         // a = a.EmitToField () // a is changed to temporary field access
 660                         // b = b.EmitToField ()
 661                         // a.Emit ()
 662                         // b.Emit ()
 663                         // Opcodes.Add
 664                         //
 665                         //
 666                         // The idea is to emit expression and leave the stack empty with
 667                         // result value still available.
 668                         //
 669                         // Expressions should override this default implementation when
 670                         // optimized version can be provided (e.g. FieldExpr)
 671                         //
 672                         //
 673                         // We can optimize for side-effect free expressions, they can be
 674                         // emitted out of order
 675                         //
 676                         if (IsSideEffectFree)
 677                                 return this;
 678
 679                         bool needs_temporary = ContainsEmitWithAwait ();
 680                         if (!needs_temporary)
 681                                 ec.EmitThis ();
 682
 683                         // Emit original code
 684                         var field = EmitToFieldSource (ec);
 685                         if (field == null) {
 686                                 //
 687                                 // Store the result to temporary field when we
 688                                 // cannot load `this' directly
 689                                 //
 690                                 field = ec.GetTemporaryField (type);
 691                                 if (needs_temporary) {
 692                                         //
 693                                         // Create temporary local (we cannot load `this' before Emit)
 694                                         //
 695                                         var temp = ec.GetTemporaryLocal (type);
 696                                         ec.Emit (OpCodes.Stloc, temp);
 697
 698                                         ec.EmitThis ();
 699                                         ec.Emit (OpCodes.Ldloc, temp);
 700                                         field.EmitAssignFromStack (ec);
 701
 702                                         ec.FreeTemporaryLocal (temp, type);
 703                                 } else {
 704                                         field.EmitAssignFromStack (ec);
 705                                 }
 706                         }
 707
 708                         return field;
 709                 }
 710
 711                 protected virtual FieldExpr EmitToFieldSource (EmitContext ec)
 712                 {
 713                         //
 714                         // Default implementation calls Emit method
 715                         //
 716                         Emit (ec);
 717                         return null;
 718                 }
 719
 720                 protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
 721                 {
 722                         if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
 723                                 bool contains_await = false;
 724
 725                                 for (int i = 1; i < expressions.Count; ++i) {
 726                                         if (expressions[i].ContainsEmitWithAwait ()) {
 727                                                 contains_await = true;
 728                                                 break;
 729                                         }
 730                                 }
 731
 732                                 if (contains_await) {
 733                                         for (int i = 0; i < expressions.Count; ++i) {
 734                                                 expressions[i] = expressions[i].EmitToField (ec);
 735                                         }
 736                                 }
 737                         }
 738
 739                         for (int i = 0; i < expressions.Count; ++i) {
 740                                 expressions[i].Emit (ec);
 741                         }
 742                 }
 743
 744                 /// <summary>
 745                 ///   Protected constructor.  Only derivate types should
 746                 ///   be able to be created
 747                 /// </summary>
 748
 749                 protected Expression ()
 750                 {
 751                 }
 752
 753                 /// <summary>
 754                 ///   Returns a fully formed expression after a MemberLookup
 755                 /// </summary>
 756                 ///
 757                 static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
 758                 {
 759                         if (spec is EventSpec)
 760                                 return new EventExpr ((EventSpec) spec, loc);
 761                         if (spec is ConstSpec)
 762                                 return new ConstantExpr ((ConstSpec) spec, loc);
 763                         if (spec is FieldSpec)
 764                                 return new FieldExpr ((FieldSpec) spec, loc);
 765                         if (spec is PropertySpec)
 766                                 return new PropertyExpr ((PropertySpec) spec, loc);
 767                         if (spec is TypeSpec)
 768                                 return new TypeExpression (((TypeSpec) spec), loc);
 769
 770                         return null;
 771                 }
 772
 773                 public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
 774                 {
 775                         var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
 776                         if (ctors == null) {
 777                                 switch (type.Kind) {
 778                                 case MemberKind.Struct:
 779                                         // Every struct has implicit default constructor if not provided by user
 780                                         if (args == null)
 781                                                 return null;
 782
 783                                         rc.Report.SymbolRelatedToPreviousError (type);
 784                                         // Report meaningful error for struct as they always have default ctor in C# context
 785                                         OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
 786                                         break;
 787                                 case MemberKind.MissingType:
 788                                 case MemberKind.InternalCompilerType:
 789 // LAMESPEC: dynamic is not really object
 790 //                                      if (type.BuiltinType == BuiltinTypeSpec.Type.Object)
 791 //                                              goto default;
 792                                         break;
 793                                 default:
 794                                         rc.Report.SymbolRelatedToPreviousError (type);
 795                                         rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
 796                                                 type.GetSignatureForError ());
 797                                         break;
 798                                 }
 799
 800                                 return null;
 801                         }
 802
 803                         if (args == null && type.IsStruct) {
 804                                 bool includes_empty = false;
 805                                 foreach (MethodSpec ctor in ctors) {
 806                                         if (ctor.Parameters.IsEmpty) {
 807                                                 includes_empty = true;
 808                                         }
 809                                 }
 810
 811                                 if (!includes_empty)
 812                                         return null;
 813                         }
 814
 815                         var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
 816                         if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
 817                                 r.InstanceQualifier = new ConstructorInstanceQualifier (type);
 818                         }
 819
 820                         return r.ResolveMember<MethodSpec> (rc, ref args);
 821                 }
 822
 823                 [Flags]
 824                 public enum MemberLookupRestrictions
 825                 {
 826                         None = 0,
 827                         InvocableOnly = 1,
 828                         ExactArity = 1 << 2,
 829                         ReadAccess = 1 << 3,
 830                         EmptyArguments = 1 << 4,
 831                         IgnoreArity = 1 << 5,
 832                         IgnoreAmbiguity = 1 << 6,
 833                         NameOfExcluded = 1 << 7,
 834                         DontSetConditionalAccess = 1 << 8
 835                 }
 836
 837                 //
 838                 // Lookup type `queried_type' for code in class `container_type' with a qualifier of
 839                 // `qualifier_type' or null to lookup members in the current class.
 840                 //
 841                 public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 842                 {
 843                         var members = MemberCache.FindMembers (queried_type, name, false);
 844
 845                         if (members != null) {
 846                                 Expression expr;
 847                                 do {
 848                                         expr = MemberLookupToExpression (rc, members, errorMode, queried_type, name, arity, restrictions, loc);
 849                                         if (expr != null)
 850                                                 return expr;
 851
 852                                         if (members [0].DeclaringType.BaseType == null)
 853                                                 members = null;
 854                                         else
 855                                                 members = MemberCache.FindMembers (members [0].DeclaringType.BaseType, name, false);
 856                                 } while (members != null);
 857                         }
 858
 859                         var tps = queried_type as TypeParameterSpec;
 860                         if (tps != null) {
 861                                 members = MemberCache.FindInterfaceMembers (tps, name);
 862                                 if (members != null)
 863                                         return MemberLookupToExpression (rc, members, errorMode, queried_type, name, arity, restrictions, loc);
 864                         }
 865
 866                         return null;
 867                 }
 868
 869                 public static Expression MemberLookupToExpression (IMemberContext rc, IList<MemberSpec> members, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 870                 {
 871                         MemberSpec non_method = null;
 872                         MemberSpec ambig_non_method = null;
 873
 874                         for (int i = 0; i < members.Count; ++i) {
 875                                 var member = members [i];
 876
 877                                 // HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
 878                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
 879                                         continue;
 880
 881                                 if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0 || member.Kind == MemberKind.Operator)
 882                                         continue;
 883
 884                                 if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
 885                                         continue;
 886
 887                                 if (!errorMode) {
 888                                         if (!member.IsAccessible (rc))
 889                                                 continue;
 890
 891                                         //
 892                                         // With runtime binder we can have a situation where queried type is inaccessible
 893                                         // because it came via dynamic object, the check about inconsisted accessibility
 894                                         // had no effect as the type was unknown during compilation
 895                                         //
 896                                         // class A {
 897                                         //              private class N { }
 898                                         //
 899                                         //              public dynamic Foo ()
 900                                         //              {
 901                                         //                      return new N ();
 902                                         //              }
 903                                         //      }
 904                                         //
 905                                         if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
 906                                                 continue;
 907                                 }
 908
 909                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
 910                                         if (member is MethodSpec) {
 911                                                 return new MethodGroupExpr (members, queried_type, loc);
 912                                         }
 913
 914                                         if (!Invocation.IsMemberInvocable (member))
 915                                                 continue;
 916                                 }
 917
 918                                 if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
 919                                         non_method = member;
 920                                 } else if (!errorMode && !member.IsNotCSharpCompatible) {
 921                                         //
 922                                         // Interface members that are hidden by class members are removed from the set when T is a type parameter and
 923                                         // T has both an effective base class other than object and a non-empty effective interface set.
 924                                         //
 925                                         // The spec has more complex rules but we simply remove all members declared in an interface declaration.
 926                                         //
 927                                         var tps = queried_type as TypeParameterSpec;
 928                                         if (tps != null && tps.HasTypeConstraint) {
 929                                                 if (non_method.DeclaringType.IsClass && member.DeclaringType.IsInterface)
 930                                                         continue;
 931
 932                                                 if (non_method.DeclaringType.IsInterface && member.DeclaringType.IsInterface) {
 933                                                         non_method = member;
 934                                                         continue;
 935                                                 }
 936                                         }
 937
 938                                         ambig_non_method = member;
 939                                 }
 940                         }
 941
 942                         if (non_method != null) {
 943                                 if (ambig_non_method != null && rc != null && (restrictions & MemberLookupRestrictions.IgnoreAmbiguity) == 0) {
 944                                         var report = rc.Module.Compiler.Report;
 945                                         report.SymbolRelatedToPreviousError (non_method);
 946                                         report.SymbolRelatedToPreviousError (ambig_non_method);
 947                                         report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
 948                                                 non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
 949                                 }
 950
 951                                 if (non_method is MethodSpec)
 952                                         return new MethodGroupExpr (members, queried_type, loc);
 953
 954                                 return ExprClassFromMemberInfo (non_method, loc);
 955                         }
 956
 957                         return null;
 958                 }
 959
 960                 protected static void Error_NamedArgument (NamedArgument na, Report Report)
 961                 {
 962                         Report.Error (1742, na.Location, "An element access expression cannot use named argument");
 963                 }
 964
 965                 protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
 966                 {
 967                         throw new NotImplementedException ();
 968                 }
 969
 970                 public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
 971                 {
 972                         if (t == InternalType.ErrorType)
 973                                 return;
 974
 975                         rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
 976                                 oper, t.GetSignatureForError ());
 977                 }
 978
 979                 protected void Error_PointerInsideExpressionTree (ResolveContext ec)
 980                 {
 981                         ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
 982                 }
 983
 984                 protected void Error_NullShortCircuitInsideExpressionTree (ResolveContext rc)
 985                 {
 986                         rc.Report.Error (8072, loc, "An expression tree cannot contain a null propagating operator");
 987                 }
 988
 989                 protected void Error_NullPropagatingLValue (ResolveContext rc)
 990                 {
 991                         rc.Report.Error (-1030, loc, "The left-hand side of an assignment cannot contain a null propagating operator");
 992                 }
 993
 994                 public virtual void FlowAnalysis (FlowAnalysisContext fc)
 995                 {
 996                 }
 997
 998                 //
 999                 // Special version of flow analysis for expressions which can return different
1000                 // on-true and on-false result. Used by &&, ||, ?: expressions
1001                 //
1002                 public virtual void FlowAnalysisConditional (FlowAnalysisContext fc)
1003                 {
1004                         FlowAnalysis (fc);
1005                         fc.DefiniteAssignmentOnTrue = fc.DefiniteAssignmentOnFalse = fc.DefiniteAssignment;
1006                 }
1007
1008                 /// <summary>
1009                 ///   Returns an expression that can be used to invoke operator true
1010                 ///   on the expression if it exists.
1011                 /// </summary>
1012                 protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
1013                 {
1014                         return GetOperatorTrueOrFalse (ec, e, true, loc);
1015                 }
1016
1017                 /// <summary>
1018                 ///   Returns an expression that can be used to invoke operator false
1019                 ///   on the expression if it exists.
1020                 /// </summary>
1021                 protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
1022                 {
1023                         return GetOperatorTrueOrFalse (ec, e, false, loc);
1024                 }
1025
1026                 static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
1027                 {
1028                         var op = is_true ? Operator.OpType.True : Operator.OpType.False;
1029                         var type = e.type;
1030                         if (type.IsNullableType)
1031                                 type = Nullable.NullableInfo.GetUnderlyingType (type);
1032
1033                         var methods = MemberCache.GetUserOperator (type, op, false);
1034                         if (methods == null)
1035                                 return null;
1036
1037                         Arguments arguments = new Arguments (1);
1038                         arguments.Add (new Argument (e));
1039
1040                         var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
1041                         var oper = res.ResolveOperator (ec, ref arguments);
1042
1043                         if (oper == null)
1044                                 return null;
1045
1046                         return new UserOperatorCall (oper, arguments, null, loc);
1047                 }
1048
1049                 public virtual string ExprClassName
1050                 {
1051                         get {
1052                                 switch (eclass){
1053                                 case ExprClass.Unresolved:
1054                                         return "Unresolved";
1055                                 case ExprClass.Value:
1056                                         return "value";
1057                                 case ExprClass.Variable:
1058                                         return "variable";
1059                                 case ExprClass.Namespace:
1060                                         return "namespace";
1061                                 case ExprClass.Type:
1062                                         return "type";
1063                                 case ExprClass.MethodGroup:
1064                                         return "method group";
1065                                 case ExprClass.PropertyAccess:
1066                                         return "property access";
1067                                 case ExprClass.EventAccess:
1068                                         return "event access";
1069                                 case ExprClass.IndexerAccess:
1070                                         return "indexer access";
1071                                 case ExprClass.Nothing:
1072                                         return "null";
1073                                 case ExprClass.TypeParameter:
1074                                         return "type parameter";
1075                                 }
1076                                 throw new Exception ("Should not happen");
1077                         }
1078                 }
1079
1080                 /// <summary>
1081                 ///   Reports that we were expecting `expr' to be of class `expected'
1082                 /// </summary>
1083                 public static void Error_UnexpectedKind (IMemberContext ctx, Expression memberExpr, string expected, string was, Location loc)
1084                 {
1085                         var name = memberExpr.GetSignatureForError ();
1086
1087                         ctx.Module.Compiler.Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected", name, was, expected);
1088                 }
1089
1090                 public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
1091                 {
1092                         string [] valid = new string [4];
1093                         int count = 0;
1094
1095                         if ((flags & ResolveFlags.VariableOrValue) != 0) {
1096                                 valid [count++] = "variable";
1097                                 valid [count++] = "value";
1098                         }
1099
1100                         if ((flags & ResolveFlags.Type) != 0)
1101                                 valid [count++] = "type";
1102
1103                         if ((flags & ResolveFlags.MethodGroup) != 0)
1104                                 valid [count++] = "method group";
1105
1106                         if (count == 0)
1107                                 valid [count++] = "unknown";
1108
1109                         StringBuilder sb = new StringBuilder (valid [0]);
1110                         for (int i = 1; i < count - 1; i++) {
1111                                 sb.Append ("', `");
1112                                 sb.Append (valid [i]);
1113                         }
1114                         if (count > 1) {
1115                                 sb.Append ("' or `");
1116                                 sb.Append (valid [count - 1]);
1117                         }
1118
1119                         ec.Report.Error (119, loc,
1120                                 "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
1121                 }
1122
1123                 public static void UnsafeError (ResolveContext ec, Location loc)
1124                 {
1125                         UnsafeError (ec.Report, loc);
1126                 }
1127
1128                 public static void UnsafeError (Report Report, Location loc)
1129                 {
1130                         Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
1131                 }
1132
1133                 public static void UnsafeInsideIteratorError (ResolveContext rc, Location loc)
1134                 {
1135                         UnsafeInsideIteratorError (rc.Report, loc);
1136                 }
1137
1138                 public static void UnsafeInsideIteratorError (Report report, Location loc)
1139                 {
1140                         report.Error (1629, loc, "Unsafe code may not appear in iterators");
1141                 }
1142
1143                 //
1144                 // Converts `source' to an int, uint, long or ulong.
1145                 //
1146                 protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source, bool pointerArray = false)
1147                 {
1148                         var btypes = ec.BuiltinTypes;
1149
1150                         if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
1151                                 Arguments args = new Arguments (1);
1152                                 args.Add (new Argument (source));
1153                                 return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, source.loc).Resolve (ec);
1154                         }
1155
1156                         Expression converted;
1157
1158                         using (ec.Set (ResolveContext.Options.CheckedScope)) {
1159                                 converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
1160                                 if (converted == null)
1161                                         converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
1162                                 if (converted == null)
1163                                         converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
1164                                 if (converted == null)
1165                                         converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);
1166
1167                                 if (converted == null) {
1168                                         source.Error_ValueCannotBeConverted (ec, btypes.Int, false);
1169                                         return null;
1170                                 }
1171                         }
1172
1173                         if (pointerArray)
1174                                 return converted;
1175
1176                         //
1177                         // Only positive constants are allowed at compile time
1178                         //
1179                         Constant c = converted as Constant;
1180                         if (c != null && c.IsNegative)
1181                                 Error_NegativeArrayIndex (ec, source.loc);
1182
1183                         // No conversion needed to array index
1184                         if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
1185                                 return converted;
1186
1187                         return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
1188                 }
1189
1190                 public Expression MakePointerAccess (ResolveContext rc, TypeSpec type, Arguments args)
1191                 {
1192                         if (args.Count != 1){
1193                                 rc.Report.Error (196, loc, "A pointer must be indexed by only one value");
1194                                 return null;
1195                         }
1196
1197                         var arg = args [0];
1198                         if (arg is NamedArgument)
1199                                 Error_NamedArgument ((NamedArgument) arg, rc.Report);
1200
1201                         var index = arg.Expr.Resolve (rc);
1202                         if (index == null)
1203                                 return null;
1204
1205                         index = ConvertExpressionToArrayIndex (rc, index, true);
1206
1207                         Expression p = new PointerArithmetic (Binary.Operator.Addition, this, index, type, loc);
1208                         return new Indirection (p, loc);
1209                 }
1210
1211                 //
1212                 // Derived classes implement this method by cloning the fields that
1213                 // could become altered during the Resolve stage
1214                 //
1215                 // Only expressions that are created for the parser need to implement
1216                 // this.
1217                 //
1218                 protected virtual void CloneTo (CloneContext clonectx, Expression target)
1219                 {
1220                         throw new NotImplementedException (
1221                                 String.Format (
1222                                         "CloneTo not implemented for expression {0}", this.GetType ()));
1223                 }
1224
1225                 //
1226                 // Clones an expression created by the parser.
1227                 //
1228                 // We only support expressions created by the parser so far, not
1229                 // expressions that have been resolved (many more classes would need
1230                 // to implement CloneTo).
1231                 //
1232                 // This infrastructure is here merely for Lambda expressions which
1233                 // compile the same code using different type values for the same
1234                 // arguments to find the correct overload
1235                 //
1236                 public virtual Expression Clone (CloneContext clonectx)
1237                 {
1238                         Expression cloned = (Expression) MemberwiseClone ();
1239                         CloneTo (clonectx, cloned);
1240
1241                         return cloned;
1242                 }
1243
1244                 //
1245                 // Implementation of expression to expression tree conversion
1246                 //
1247                 public abstract Expression CreateExpressionTree (ResolveContext ec);
1248
1249                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
1250                 {
1251                         return CreateExpressionFactoryCall (ec, name, null, args, loc);
1252                 }
1253
1254                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
1255                 {
1256                         return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
1257                 }
1258
1259                 public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
1260                 {
1261                         return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
1262                 }
1263
1264                 protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
1265                 {
1266                         var t = ec.Module.PredefinedTypes.Expression.Resolve ();
1267                         if (t == null)
1268                                 return null;
1269
1270                         return new TypeExpression (t, loc);
1271                 }
1272
1273                 //
1274                 // Implemented by all expressions which support conversion from
1275                 // compiler expression to invokable runtime expression. Used by
1276                 // dynamic C# binder.
1277                 //
1278                 public virtual SLE.Expression MakeExpression (BuilderContext ctx)
1279                 {
1280                         throw new NotImplementedException ("MakeExpression for " + GetType ());
1281                 }
1282
1283                 public virtual object Accept (StructuralVisitor visitor)
1284                 {
1285                         return visitor.Visit (this);
1286                 }
1287         }
1288
1289         /// <summary>
1290         ///   This is just a base class for expressions that can
1291         ///   appear on statements (invocations, object creation,
1292         ///   assignments, post/pre increment and decrement).  The idea
1293         ///   being that they would support an extra Emition interface that
1294         ///   does not leave a result on the stack.
1295         /// </summary>
1296         public abstract class ExpressionStatement : Expression
1297         {
1298                 public virtual void MarkReachable (Reachability rc)
1299                 {
1300                 }
1301
1302                 public virtual ExpressionStatement ResolveStatement (BlockContext ec)
1303                 {
1304                         Expression e = Resolve (ec);
1305                         if (e == null)
1306                                 return null;
1307
1308                         ExpressionStatement es = e as ExpressionStatement;
1309                         if (es == null || e is AnonymousMethodBody) {
1310                                 var reduced = e as IReducedExpressionStatement;
1311                                 if (reduced != null) {
1312                                         return EmptyExpressionStatement.Instance;
1313                                 }
1314
1315                                 Error_InvalidExpressionStatement (ec);
1316                         }
1317
1318                         //
1319                         // This is quite expensive warning, try to limit the damage
1320                         //
1321                         if (MemberAccess.IsValidDotExpression (e.Type) && !(e is Assign || e is Await)) {
1322                                 WarningAsyncWithoutWait (ec, e);
1323                         }
1324
1325                         return es;
1326                 }
1327
1328                 static void WarningAsyncWithoutWait (BlockContext bc, Expression e)
1329                 {
1330                         if (bc.CurrentAnonymousMethod is AsyncInitializer) {
1331                                 var awaiter = new AwaitStatement.AwaitableMemberAccess (e) {
1332                                         ProbingMode = true
1333                                 };
1334
1335                                 //
1336                                 // Need to do full resolve because GetAwaiter can be extension method
1337                                 // available only in this context
1338                                 //
1339                                 var mg = awaiter.Resolve (bc) as MethodGroupExpr;
1340                                 if (mg == null)
1341                                         return;
1342
1343                                 var arguments = new Arguments (0);
1344                                 mg = mg.OverloadResolve (bc, ref arguments, null, OverloadResolver.Restrictions.ProbingOnly);
1345                                 if (mg == null)
1346                                         return;
1347
1348                                 //
1349                                 // Use same check rules as for real await
1350                                 //
1351                                 var awaiter_definition = bc.Module.GetAwaiter (mg.BestCandidateReturnType);
1352                                 if (!awaiter_definition.IsValidPattern || !awaiter_definition.INotifyCompletion)
1353                                         return;
1354
1355                                 bc.Report.Warning (4014, 1, e.Location,
1356                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator");
1357                                 return;
1358                         }
1359
1360                         var inv = e as Invocation;
1361                         if (inv != null && inv.MethodGroup != null && inv.MethodGroup.BestCandidate.IsAsync) {
1362                                 // The warning won't be reported for imported methods to maintain warning compatiblity with csc
1363                                 bc.Report.Warning (4014, 1, e.Location,
1364                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator or calling `Wait' method");
1365                                 return;
1366                         }
1367                 }
1368
1369                 /// <summary>
1370                 ///   Requests the expression to be emitted in a `statement'
1371                 ///   context.  This means that no new value is left on the
1372                 ///   stack after invoking this method (constrasted with
1373                 ///   Emit that will always leave a value on the stack).
1374                 /// </summary>
1375                 public abstract void EmitStatement (EmitContext ec);
1376
1377                 public override void EmitSideEffect (EmitContext ec)
1378                 {
1379                         EmitStatement (ec);
1380                 }
1381         }
1382
1383         interface IReducedExpressionStatement
1384         {
1385         }
1386
1387         /// <summary>
1388         ///   This kind of cast is used to encapsulate the child
1389         ///   whose type is child.Type into an expression that is
1390         ///   reported to return "return_type".  This is used to encapsulate
1391         ///   expressions which have compatible types, but need to be dealt
1392         ///   at higher levels with.
1393         ///
1394         ///   For example, a "byte" expression could be encapsulated in one
1395         ///   of these as an "unsigned int".  The type for the expression
1396         ///   would be "unsigned int".
1397         ///
1398         /// </summary>
1399         public abstract class TypeCast : Expression
1400         {
1401                 protected readonly Expression child;
1402
1403                 protected TypeCast (Expression child, TypeSpec return_type)
1404                 {
1405                         eclass = child.eclass;
1406                         loc = child.Location;
1407                         type = return_type;
1408                         this.child = child;
1409                 }
1410
1411                 public Expression Child {
1412                         get {
1413                                 return child;
1414                         }
1415                 }
1416
1417                 public override bool ContainsEmitWithAwait ()
1418                 {
1419                         return child.ContainsEmitWithAwait ();
1420                 }
1421
1422                 public override Expression CreateExpressionTree (ResolveContext ec)
1423                 {
1424                         Arguments args = new Arguments (2);
1425                         args.Add (new Argument (child.CreateExpressionTree (ec)));
1426                         args.Add (new Argument (new TypeOf (type, loc)));
1427
1428                         if (type.IsPointer || child.Type.IsPointer)
1429                                 Error_PointerInsideExpressionTree (ec);
1430
1431                         return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
1432                 }
1433
1434                 protected override Expression DoResolve (ResolveContext ec)
1435                 {
1436                         // This should never be invoked, we are born in fully
1437                         // initialized state.
1438
1439                         return this;
1440                 }
1441
1442                 public override void Emit (EmitContext ec)
1443                 {
1444                         child.Emit (ec);
1445                 }
1446
1447                 public override void FlowAnalysis (FlowAnalysisContext fc)
1448                 {
1449                         child.FlowAnalysis (fc);
1450                 }
1451
1452                 public override SLE.Expression MakeExpression (BuilderContext ctx)
1453                 {
1454 #if STATIC
1455                         return base.MakeExpression (ctx);
1456 #else
1457                         return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
1458                                 SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
1459                                 SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
1460 #endif
1461                 }
1462
1463                 protected override void CloneTo (CloneContext clonectx, Expression t)
1464                 {
1465                         // Nothing to clone
1466                 }
1467
1468                 public override bool IsNull {
1469                         get { return child.IsNull; }
1470                 }
1471         }
1472
1473         public class EmptyCast : TypeCast {
1474                 EmptyCast (Expression child, TypeSpec target_type)
1475                         : base (child, target_type)
1476                 {
1477                 }
1478
1479                 public static Expression Create (Expression child, TypeSpec type)
1480                 {
1481                         Constant c = child as Constant;
1482                         if (c != null) {
1483                                 var enum_constant = c as EnumConstant;
1484                                 if (enum_constant != null)
1485                                         c = enum_constant.Child;
1486
1487                                 if (!(c is ReducedExpression.ReducedConstantExpression)) {
1488                                         if (c.Type == type)
1489                                                 return c;
1490
1491                                         var res = c.ConvertImplicitly (type);
1492                                         if (res != null)
1493                                                 return res;
1494                                 }
1495                         }
1496
1497                         EmptyCast e = child as EmptyCast;
1498                         if (e != null)
1499                                 return new EmptyCast (e.child, type);
1500
1501                         return new EmptyCast (child, type);
1502                 }
1503
1504                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1505                 {
1506                         child.EmitBranchable (ec, label, on_true);
1507                 }
1508
1509                 public override void EmitSideEffect (EmitContext ec)
1510                 {
1511                         child.EmitSideEffect (ec);
1512                 }
1513         }
1514
1515         //
1516         // Used for predefined type user operator (no obsolete check, etc.)
1517         //
1518         public class OperatorCast : TypeCast
1519         {
1520                 readonly MethodSpec conversion_operator;
1521
1522                 public OperatorCast (Expression expr, TypeSpec target_type)
1523                         : this (expr, target_type, target_type, false)
1524                 {
1525                 }
1526
1527                 public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
1528                         : this (expr, target_type, target_type, find_explicit)
1529                 {
1530                 }
1531
1532                 public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
1533                         : base (expr, returnType)
1534                 {
1535                         var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
1536                         var mi = MemberCache.GetUserOperator (declaringType, op, true);
1537
1538                         if (mi != null) {
1539                                 foreach (MethodSpec oper in mi) {
1540                                         if (oper.ReturnType != returnType)
1541                                                 continue;
1542
1543                                         if (oper.Parameters.Types[0] == expr.Type) {
1544                                                 conversion_operator = oper;
1545                                                 return;
1546                                         }
1547                                 }
1548                         }
1549
1550                         throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
1551                                 returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
1552                 }
1553
1554                 public override void Emit (EmitContext ec)
1555                 {
1556                         child.Emit (ec);
1557                         ec.Emit (OpCodes.Call, conversion_operator);
1558                 }
1559         }
1560
1561         //
1562         // Constant specialization of EmptyCast.
1563         // We need to special case this since an empty cast of
1564         // a constant is still a constant.
1565         //
1566         public class EmptyConstantCast : Constant
1567         {
1568                 public readonly Constant child;
1569
1570                 public EmptyConstantCast (Constant child, TypeSpec type)
1571                         : base (child.Location)
1572                 {
1573                         if (child == null)
1574                                 throw new ArgumentNullException ("child");
1575
1576                         this.child = child;
1577                         this.eclass = child.eclass;
1578                         this.type = type;
1579                 }
1580
1581                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1582                 {
1583                         if (child.Type == target_type)
1584                                 return child;
1585
1586                         // FIXME: check that 'type' can be converted to 'target_type' first
1587                         return child.ConvertExplicitly (in_checked_context, target_type);
1588                 }
1589
1590                 public override Expression CreateExpressionTree (ResolveContext ec)
1591                 {
1592                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
1593                                 child.CreateExpressionTree (ec),
1594                                 new TypeOf (type, loc));
1595
1596                         if (type.IsPointer)
1597                                 Error_PointerInsideExpressionTree (ec);
1598
1599                         return CreateExpressionFactoryCall (ec, "Convert", args);
1600                 }
1601
1602                 public override bool IsDefaultValue {
1603                         get { return child.IsDefaultValue; }
1604                 }
1605
1606                 public override bool IsNegative {
1607                         get { return child.IsNegative; }
1608                 }
1609
1610                 public override bool IsNull {
1611                         get { return child.IsNull; }
1612                 }
1613
1614                 public override bool IsOneInteger {
1615                         get { return child.IsOneInteger; }
1616                 }
1617
1618                 public override bool IsSideEffectFree {
1619                         get {
1620                                 return child.IsSideEffectFree;
1621                         }
1622                 }
1623
1624                 public override bool IsZeroInteger {
1625                         get { return child.IsZeroInteger; }
1626                 }
1627
1628                 public override void Emit (EmitContext ec)
1629                 {
1630                         child.Emit (ec);
1631                 }
1632
1633                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1634                 {
1635                         child.EmitBranchable (ec, label, on_true);
1636
1637                         // Only to make verifier happy
1638                         if (TypeManager.IsGenericParameter (type) && child.IsNull)
1639                                 ec.Emit (OpCodes.Unbox_Any, type);
1640                 }
1641
1642                 public override void EmitSideEffect (EmitContext ec)
1643                 {
1644                         child.EmitSideEffect (ec);
1645                 }
1646
1647                 public override object GetValue ()
1648                 {
1649                         return child.GetValue ();
1650                 }
1651
1652                 public override string GetValueAsLiteral ()
1653                 {
1654                         return child.GetValueAsLiteral ();
1655                 }
1656
1657                 public override long GetValueAsLong ()
1658                 {
1659                         return child.GetValueAsLong ();
1660                 }
1661
1662                 public override Constant ConvertImplicitly (TypeSpec target_type)
1663                 {
1664                         if (type == target_type)
1665                                 return this;
1666
1667                         // FIXME: Do we need to check user conversions?
1668                         if (!Convert.ImplicitStandardConversionExists (this, target_type))
1669                                 return null;
1670
1671                         return child.ConvertImplicitly (target_type);
1672                 }
1673         }
1674
1675         /// <summary>
1676         ///  This class is used to wrap literals which belong inside Enums
1677         /// </summary>
1678         public class EnumConstant : Constant
1679         {
1680                 public Constant Child;
1681
1682                 public EnumConstant (Constant child, TypeSpec enum_type)
1683                         : base (child.Location)
1684                 {
1685                         this.Child = child;
1686
1687                         this.eclass = ExprClass.Value;
1688                         this.type = enum_type;
1689                 }
1690
1691                 protected EnumConstant (Location loc)
1692                         : base (loc)
1693                 {
1694                 }
1695
1696                 public override void Emit (EmitContext ec)
1697                 {
1698                         Child.Emit (ec);
1699                 }
1700
1701                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
1702                 {
1703                         Child.EncodeAttributeValue (rc, enc, Child.Type, parameterType);
1704                 }
1705
1706                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1707                 {
1708                         Child.EmitBranchable (ec, label, on_true);
1709                 }
1710
1711                 public override void EmitSideEffect (EmitContext ec)
1712                 {
1713                         Child.EmitSideEffect (ec);
1714                 }
1715
1716                 public override string GetSignatureForError()
1717                 {
1718                         return Type.GetSignatureForError ();
1719                 }
1720
1721                 public override object GetValue ()
1722                 {
1723                         return Child.GetValue ();
1724                 }
1725
1726 #if !STATIC
1727                 public override object GetTypedValue ()
1728                 {
1729                         //
1730                         // The method can be used in dynamic context only (on closed types)
1731                         //
1732                         // System.Enum.ToObject cannot be called on dynamic types
1733                         // EnumBuilder has to be used, but we cannot use EnumBuilder
1734                         // because it does not properly support generics
1735                         //
1736                         return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
1737                 }
1738 #endif
1739
1740                 public override string GetValueAsLiteral ()
1741                 {
1742                         return Child.GetValueAsLiteral ();
1743                 }
1744
1745                 public override long GetValueAsLong ()
1746                 {
1747                         return Child.GetValueAsLong ();
1748                 }
1749
1750                 public EnumConstant Increment()
1751                 {
1752                         return new EnumConstant (((IntegralConstant) Child).Increment (), type);
1753                 }
1754
1755                 public override bool IsDefaultValue {
1756                         get {
1757                                 return Child.IsDefaultValue;
1758                         }
1759                 }
1760
1761                 public override bool IsSideEffectFree {
1762                         get {
1763                                 return Child.IsSideEffectFree;
1764                         }
1765                 }
1766
1767                 public override bool IsZeroInteger {
1768                         get { return Child.IsZeroInteger; }
1769                 }
1770
1771                 public override bool IsNegative {
1772                         get {
1773                                 return Child.IsNegative;
1774                         }
1775                 }
1776
1777                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1778                 {
1779                         if (Child.Type == target_type)
1780                                 return Child;
1781
1782                         return Child.ConvertExplicitly (in_checked_context, target_type);
1783                 }
1784
1785                 public override Constant ConvertImplicitly (TypeSpec type)
1786                 {
1787                         if (this.type == type) {
1788                                 return this;
1789                         }
1790
1791                         if (!Convert.ImplicitStandardConversionExists (this, type)){
1792                                 return null;
1793                         }
1794
1795                         return Child.ConvertImplicitly (type);
1796                 }
1797         }
1798
1799         /// <summary>
1800         ///   This kind of cast is used to encapsulate Value Types in objects.
1801         ///
1802         ///   The effect of it is to box the value type emitted by the previous
1803         ///   operation.
1804         /// </summary>
1805         public class BoxedCast : TypeCast {
1806
1807                 public BoxedCast (Expression expr, TypeSpec target_type)
1808                         : base (expr, target_type)
1809                 {
1810                         eclass = ExprClass.Value;
1811                 }
1812
1813                 protected override Expression DoResolve (ResolveContext ec)
1814                 {
1815                         // This should never be invoked, we are born in fully
1816                         // initialized state.
1817
1818                         return this;
1819                 }
1820
1821                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
1822                 {
1823                         // Only boxing to object type is supported
1824                         if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
1825                                 base.EncodeAttributeValue (rc, enc, targetType, parameterType);
1826                                 return;
1827                         }
1828
1829                         enc.Encode (child.Type);
1830                         child.EncodeAttributeValue (rc, enc, child.Type, parameterType);
1831                 }
1832
1833                 public override void Emit (EmitContext ec)
1834                 {
1835                         base.Emit (ec);
1836
1837                         ec.Emit (OpCodes.Box, child.Type);
1838                 }
1839
1840                 public override void EmitSideEffect (EmitContext ec)
1841                 {
1842                         // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
1843                         // so, we need to emit the box+pop instructions in most cases
1844                         if (child.Type.IsStruct &&
1845                             (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
1846                                 child.EmitSideEffect (ec);
1847                         else
1848                                 base.EmitSideEffect (ec);
1849                 }
1850         }
1851
1852         public class UnboxCast : TypeCast {
1853                 public UnboxCast (Expression expr, TypeSpec return_type)
1854                         : base (expr, return_type)
1855                 {
1856                 }
1857
1858                 protected override Expression DoResolve (ResolveContext ec)
1859                 {
1860                         // This should never be invoked, we are born in fully
1861                         // initialized state.
1862
1863                         return this;
1864                 }
1865
1866                 public override void Emit (EmitContext ec)
1867                 {
1868                         base.Emit (ec);
1869
1870                         ec.Emit (OpCodes.Unbox_Any, type);
1871                 }
1872         }
1873
1874         /// <summary>
1875         ///   This is used to perform explicit numeric conversions.
1876         ///
1877         ///   Explicit numeric conversions might trigger exceptions in a checked
1878         ///   context, so they should generate the conv.ovf opcodes instead of
1879         ///   conv opcodes.
1880         /// </summary>
1881         public class ConvCast : TypeCast {
1882                 public enum Mode : byte {
1883                         I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
1884                         U1_I1, U1_CH,
1885                         I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
1886                         U2_I1, U2_U1, U2_I2, U2_CH,
1887                         I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
1888                         U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
1889                         I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
1890                         U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
1891                         CH_I1, CH_U1, CH_I2,
1892                         R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
1893                         R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
1894                         I_I8,
1895                 }
1896
1897                 Mode mode;
1898
1899                 public ConvCast (Expression child, TypeSpec return_type, Mode m)
1900                         : base (child, return_type)
1901                 {
1902                         mode = m;
1903                 }
1904
1905                 protected override Expression DoResolve (ResolveContext ec)
1906                 {
1907                         // This should never be invoked, we are born in fully
1908                         // initialized state.
1909
1910                         return this;
1911                 }
1912
1913                 public override string ToString ()
1914                 {
1915                         return String.Format ("ConvCast ({0}, {1})", mode, child);
1916                 }
1917
1918                 public override void Emit (EmitContext ec)
1919                 {
1920                         base.Emit (ec);
1921                         Emit (ec, mode);
1922                 }
1923
1924                 public static void Emit (EmitContext ec, Mode mode)
1925                 {
1926                         if (ec.HasSet (EmitContext.Options.CheckedScope)) {
1927                                 switch (mode){
1928                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1929                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1930                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1931                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1932                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1933
1934                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1935                                 case Mode.U1_CH: /* nothing */ break;
1936
1937                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1938                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1939                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1940                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1941                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1942                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1943
1944                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1945                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1946                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1947                                 case Mode.U2_CH: /* nothing */ break;
1948
1949                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1950                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1951                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1952                                 case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1953                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1954                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1955                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1956
1957                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1958                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1959                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1960                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1961                                 case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1962                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1963
1964                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1965                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1966                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1967                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1968                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1969                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1970                                 case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1971                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1972                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;
1973
1974                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1975                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1976                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1977                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1978                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1979                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
1980                                 case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1981                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1982                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;
1983
1984                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1985                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1986                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1987
1988                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1989                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1990                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1991                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1992                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1993                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1994                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1995                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1996                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1997
1998                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1999                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
2000                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
2001                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
2002                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
2003                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
2004                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
2005                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
2006                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
2007                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
2008
2009                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
2010                                 }
2011                         } else {
2012                                 switch (mode){
2013                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
2014                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
2015                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
2016                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
2017                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;
2018
2019                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
2020                                 case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;
2021
2022                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
2023                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
2024                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
2025                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
2026                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
2027                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;
2028
2029                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
2030                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
2031                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
2032                                 case Mode.U2_CH: /* nothing */ break;
2033
2034                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
2035                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
2036                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
2037                                 case Mode.I4_U4: /* nothing */ break;
2038                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_U2); break;
2039                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_I8); break;
2040                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_U2); break;
2041
2042                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_I1); break;
2043                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_U1); break;
2044                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_I2); break;
2045                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_U2); break;
2046                                 case Mode.U4_I4: /* nothing */ break;
2047                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_U2); break;
2048
2049                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_I1); break;
2050                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_U1); break;
2051                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_I2); break;
2052                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_U2); break;
2053                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_I4); break;
2054                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_U4); break;
2055                                 case Mode.I8_U8: /* nothing */ break;
2056                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_U2); break;
2057                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_U); break;
2058
2059                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_I1); break;
2060                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_U1); break;
2061                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_I2); break;
2062                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_U2); break;
2063                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_I4); break;
2064                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_U4); break;
2065                                 case Mode.U8_I8: /* nothing */ break;
2066                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_U2); break;
2067                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_U); break;
2068
2069                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_I1); break;
2070                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_U1); break;
2071                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_I2); break;
2072
2073                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_I1); break;
2074                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_U1); break;
2075                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_I2); break;
2076                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_U2); break;
2077                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_I4); break;
2078                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_U4); break;
2079                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_I8); break;
2080                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_U8); break;
2081                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_U2); break;
2082
2083                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_I1); break;
2084                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_U1); break;
2085                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_I2); break;
2086                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_U2); break;
2087                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_I4); break;
2088                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_U4); break;
2089                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_I8); break;
2090                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_U8); break;
2091                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_U2); break;
2092                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
2093
2094                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_U8); break;
2095                                 }
2096                         }
2097                 }
2098         }
2099
2100         class OpcodeCast : TypeCast
2101         {
2102                 readonly OpCode op;
2103
2104                 public OpcodeCast (Expression child, TypeSpec return_type, OpCode op)
2105                         : base (child, return_type)
2106                 {
2107                         this.op = op;
2108                 }
2109
2110                 protected override Expression DoResolve (ResolveContext ec)
2111                 {
2112                         // This should never be invoked, we are born in fully
2113                         // initialized state.
2114
2115                         return this;
2116                 }
2117
2118                 public override void Emit (EmitContext ec)
2119                 {
2120                         base.Emit (ec);
2121                         ec.Emit (op);
2122                 }
2123
2124                 public TypeSpec UnderlyingType {
2125                         get { return child.Type; }
2126                 }
2127         }
2128
2129         //
2130         // Opcode casts expression with 2 opcodes but only
2131         // single expression tree node
2132         //
2133         class OpcodeCastDuplex : OpcodeCast
2134         {
2135                 readonly OpCode second;
2136
2137                 public OpcodeCastDuplex (Expression child, TypeSpec returnType, OpCode first, OpCode second)
2138                         : base (child, returnType, first)
2139                 {
2140                         this.second = second;
2141                 }
2142
2143                 public override void Emit (EmitContext ec)
2144                 {
2145                         base.Emit (ec);
2146                         ec.Emit (second);
2147                 }
2148         }
2149
2150         /// <summary>
2151         ///   This kind of cast is used to encapsulate a child and cast it
2152         ///   to the class requested
2153         /// </summary>
2154         public sealed class ClassCast : TypeCast {
2155                 readonly bool forced;
2156
2157                 public ClassCast (Expression child, TypeSpec return_type)
2158                         : base (child, return_type)
2159                 {
2160                 }
2161
2162                 public ClassCast (Expression child, TypeSpec return_type, bool forced)
2163                         : base (child, return_type)
2164                 {
2165                         this.forced = forced;
2166                 }
2167
2168                 public override void Emit (EmitContext ec)
2169                 {
2170                         base.Emit (ec);
2171
2172                         bool gen = TypeManager.IsGenericParameter (child.Type);
2173                         if (gen)
2174                                 ec.Emit (OpCodes.Box, child.Type);
2175
2176                         if (type.IsGenericParameter) {
2177                                 ec.Emit (OpCodes.Unbox_Any, type);
2178                                 return;
2179                         }
2180
2181                         if (gen && !forced)
2182                                 return;
2183
2184                         ec.Emit (OpCodes.Castclass, type);
2185                 }
2186         }
2187
2188         //
2189         // Created during resolving pahse when an expression is wrapped or constantified
2190         // and original expression can be used later (e.g. for expression trees)
2191         //
2192         public class ReducedExpression : Expression
2193         {
2194                 public class ReducedConstantExpression : EmptyConstantCast
2195                 {
2196                         readonly Expression orig_expr;
2197
2198                         public ReducedConstantExpression (Constant expr, Expression orig_expr)
2199                                 : base (expr, expr.Type)
2200                         {
2201                                 this.orig_expr = orig_expr;
2202                         }
2203
2204                         public Expression OriginalExpression {
2205                                 get {
2206                                         return orig_expr;
2207                                 }
2208                         }
2209
2210                         public override Constant ConvertImplicitly (TypeSpec target_type)
2211                         {
2212                                 Constant c = base.ConvertImplicitly (target_type);
2213                                 if (c != null)
2214                                         c = new ReducedConstantExpression (c, orig_expr);
2215
2216                                 return c;
2217                         }
2218
2219                         public override Expression CreateExpressionTree (ResolveContext ec)
2220                         {
2221                                 return orig_expr.CreateExpressionTree (ec);
2222                         }
2223
2224                         public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
2225                         {
2226                                 Constant c = base.ConvertExplicitly (in_checked_context, target_type);
2227                                 if (c != null)
2228                                         c = new ReducedConstantExpression (c, orig_expr);
2229                                 return c;
2230                         }
2231
2232                         public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType, TypeSpec parameterType)
2233                         {
2234                                 //
2235                                 // LAMESPEC: Reduced conditional expression is allowed as an attribute argument
2236                                 //
2237                                 if (orig_expr is Conditional)
2238                                         child.EncodeAttributeValue (rc, enc, targetType,parameterType);
2239                                 else
2240                                         base.EncodeAttributeValue (rc, enc, targetType, parameterType);
2241                         }
2242                 }
2243
2244                 sealed class ReducedConstantStatement : ReducedConstantExpression, IReducedExpressionStatement
2245                 {
2246                         public ReducedConstantStatement (Constant expr, Expression origExpr)
2247                                 : base (expr, origExpr)
2248                         {
2249                         }
2250                 }
2251
2252                 sealed class ReducedExpressionStatement : ExpressionStatement
2253                 {
2254                         readonly Expression orig_expr;
2255                         readonly ExpressionStatement stm;
2256
2257                         public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
2258                         {
2259                                 this.orig_expr = orig;
2260                                 this.stm = stm;
2261                                 this.eclass = stm.eclass;
2262                                 this.type = stm.Type;
2263
2264                                 this.loc = orig.Location;
2265                         }
2266
2267                         public override bool ContainsEmitWithAwait ()
2268                         {
2269                                 return stm.ContainsEmitWithAwait ();
2270                         }
2271
2272                         public override Expression CreateExpressionTree (ResolveContext ec)
2273                         {
2274                                 return orig_expr.CreateExpressionTree (ec);
2275                         }
2276
2277                         protected override Expression DoResolve (ResolveContext ec)
2278                         {
2279                                 return this;
2280                         }
2281
2282                         public override void Emit (EmitContext ec)
2283                         {
2284                                 stm.Emit (ec);
2285                         }
2286
2287                         public override void EmitStatement (EmitContext ec)
2288                         {
2289                                 stm.EmitStatement (ec);
2290                         }
2291
2292                         public override void FlowAnalysis (FlowAnalysisContext fc)
2293                         {
2294                                 stm.FlowAnalysis (fc);
2295                         }
2296                 }
2297
2298                 readonly Expression expr, orig_expr;
2299
2300                 private ReducedExpression (Expression expr, Expression orig_expr)
2301                 {
2302                         this.expr = expr;
2303                         this.eclass = expr.eclass;
2304                         this.type = expr.Type;
2305                         this.orig_expr = orig_expr;
2306                         this.loc = orig_expr.Location;
2307                 }
2308
2309                 #region Properties
2310
2311                 public override bool IsSideEffectFree {
2312                         get {
2313                                 return expr.IsSideEffectFree;
2314                         }
2315                 }
2316
2317                 public Expression OriginalExpression {
2318                         get {
2319                                 return orig_expr;
2320                         }
2321                 }
2322
2323                 #endregion
2324
2325                 public override bool ContainsEmitWithAwait ()
2326                 {
2327                         return expr.ContainsEmitWithAwait ();
2328                 }
2329
2330                 //
2331                 // Creates fully resolved expression switcher
2332                 //
2333                 public static Constant Create (Constant expr, Expression originalExpr)
2334                 {
2335                         if (expr.eclass == ExprClass.Unresolved)
2336                                 throw new ArgumentException ("Unresolved expression");
2337
2338                         if (originalExpr is ExpressionStatement)
2339                                 return new ReducedConstantStatement (expr, originalExpr);
2340
2341                         return new ReducedConstantExpression (expr, originalExpr);
2342                 }
2343
2344                 public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
2345                 {
2346                         return new ReducedExpressionStatement (s, orig);
2347                 }
2348
2349                 public static Expression Create (Expression expr, Expression original_expr)
2350                 {
2351                         return Create (expr, original_expr, true);
2352                 }
2353
2354                 //
2355                 // Creates unresolved reduce expression. The original expression has to be
2356                 // already resolved. Created expression is constant based based on `expr'
2357                 // value unless canBeConstant is used
2358                 //
2359                 public static Expression Create (Expression expr, Expression original_expr, bool canBeConstant)
2360                 {
2361                         if (canBeConstant) {
2362                                 Constant c = expr as Constant;
2363                                 if (c != null)
2364                                         return Create (c, original_expr);
2365                         }
2366
2367                         ExpressionStatement s = expr as ExpressionStatement;
2368                         if (s != null)
2369                                 return Create (s, original_expr);
2370
2371                         if (expr.eclass == ExprClass.Unresolved)
2372                                 throw new ArgumentException ("Unresolved expression");
2373
2374                         return new ReducedExpression (expr, original_expr);
2375                 }
2376
2377                 public override Expression CreateExpressionTree (ResolveContext ec)
2378                 {
2379                         return orig_expr.CreateExpressionTree (ec);
2380                 }
2381
2382                 protected override Expression DoResolve (ResolveContext ec)
2383                 {
2384                         return this;
2385                 }
2386
2387                 public override void Emit (EmitContext ec)
2388                 {
2389                         expr.Emit (ec);
2390                 }
2391
2392                 public override Expression EmitToField (EmitContext ec)
2393                 {
2394                         return expr.EmitToField(ec);
2395                 }
2396
2397                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2398                 {
2399                         expr.EmitBranchable (ec, target, on_true);
2400                 }
2401
2402                 public override void FlowAnalysis (FlowAnalysisContext fc)
2403                 {
2404                         expr.FlowAnalysis (fc);
2405                 }
2406
2407                 public override SLE.Expression MakeExpression (BuilderContext ctx)
2408                 {
2409                         return orig_expr.MakeExpression (ctx);
2410                 }
2411         }
2412
2413         //
2414         // Standard composite pattern
2415         //
2416         public abstract class CompositeExpression : Expression
2417         {
2418                 protected Expression expr;
2419
2420                 protected CompositeExpression (Expression expr)
2421                 {
2422                         this.expr = expr;
2423                         this.loc = expr.Location;
2424                 }
2425
2426                 public override bool ContainsEmitWithAwait ()
2427                 {
2428                         return expr.ContainsEmitWithAwait ();
2429                 }
2430
2431                 public override Expression CreateExpressionTree (ResolveContext rc)
2432                 {
2433                         return expr.CreateExpressionTree (rc);
2434                 }
2435
2436                 public Expression Child {
2437                         get { return expr; }
2438                 }
2439
2440                 protected override Expression DoResolve (ResolveContext rc)
2441                 {
2442                         expr = expr.Resolve (rc);
2443                         if (expr == null)
2444                                 return null;
2445
2446                         type = expr.Type;
2447                         eclass = expr.eclass;
2448                         return this;
2449                 }
2450
2451                 public override void Emit (EmitContext ec)
2452                 {
2453                         expr.Emit (ec);
2454                 }
2455
2456                 public override bool IsNull {
2457                         get { return expr.IsNull; }
2458                 }
2459         }
2460
2461         //
2462         // Base of expressions used only to narrow resolve flow
2463         //
2464         public abstract class ShimExpression : Expression
2465         {
2466                 protected Expression expr;
2467
2468                 protected ShimExpression (Expression expr)
2469                 {
2470                         this.expr = expr;
2471                 }
2472
2473                 public Expression Expr {
2474                         get {
2475                                 return expr;
2476                         }
2477                 }
2478
2479                 protected override void CloneTo (CloneContext clonectx, Expression t)
2480                 {
2481                         if (expr == null)
2482                                 return;
2483
2484                         ShimExpression target = (ShimExpression) t;
2485                         target.expr = expr.Clone (clonectx);
2486                 }
2487
2488                 public override bool ContainsEmitWithAwait ()
2489                 {
2490                         return expr.ContainsEmitWithAwait ();
2491                 }
2492
2493                 public override Expression CreateExpressionTree (ResolveContext ec)
2494                 {
2495                         throw new NotSupportedException ("ET");
2496                 }
2497
2498                 public override void Emit (EmitContext ec)
2499                 {
2500                         throw new InternalErrorException ("Missing Resolve call");
2501                 }
2502         }
2503
2504         public class UnreachableExpression : Expression
2505         {
2506                 public UnreachableExpression (Expression expr)
2507                 {
2508                         this.loc = expr.Location;
2509                 }
2510
2511                 public override Expression CreateExpressionTree (ResolveContext ec)
2512                 {
2513                         // TODO: is it ok
2514                         throw new NotImplementedException ();
2515                 }
2516
2517                 protected override Expression DoResolve (ResolveContext rc)
2518                 {
2519                         throw new NotSupportedException ();
2520                 }
2521
2522                 public override void FlowAnalysis (FlowAnalysisContext fc)
2523                 {
2524                         fc.Report.Warning (429, 4, loc, "Unreachable expression code detected");
2525                 }
2526
2527                 public override void Emit (EmitContext ec)
2528                 {
2529                 }
2530
2531                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2532                 {
2533                 }
2534         }
2535
2536         //
2537         // Unresolved type name expressions
2538         //
2539         public abstract class ATypeNameExpression : FullNamedExpression
2540         {
2541                 string name;
2542                 protected TypeArguments targs;
2543
2544                 protected ATypeNameExpression (string name, Location l)
2545                 {
2546                         this.name = name;
2547                         loc = l;
2548                 }
2549
2550                 protected ATypeNameExpression (string name, TypeArguments targs, Location l)
2551                 {
2552                         this.name = name;
2553                         this.targs = targs;
2554                         loc = l;
2555                 }
2556
2557                 protected ATypeNameExpression (string name, int arity, Location l)
2558                         : this (name, new UnboundTypeArguments (arity, l), l)
2559                 {
2560                 }
2561
2562                 #region Properties
2563
2564                 public int Arity {
2565                         get {
2566                                 return targs == null ? 0 : targs.Count;
2567                         }
2568                 }
2569
2570                 public bool HasTypeArguments {
2571                         get {
2572                                 return targs != null && !targs.IsEmpty;
2573                         }
2574                 }
2575
2576                 public string Name {
2577                         get {
2578                                 return name;
2579                         }
2580                         set {
2581                                 name = value;
2582                         }
2583                 }
2584
2585                 public TypeArguments TypeArguments {
2586                         get {
2587                                 return targs;
2588                         }
2589                 }
2590
2591                 #endregion
2592
2593                 public override bool Equals (object obj)
2594                 {
2595                         ATypeNameExpression atne = obj as ATypeNameExpression;
2596                         return atne != null && atne.Name == Name &&
2597                                 (targs == null || targs.Equals (atne.targs));
2598                 }
2599
2600                 public override int GetHashCode ()
2601                 {
2602                         return Name.GetHashCode ();
2603                 }
2604
2605                 // TODO: Move it to MemberCore
2606                 public static string GetMemberType (MemberCore mc)
2607                 {
2608                         if (mc is Property)
2609                                 return "property";
2610                         if (mc is Indexer)
2611                                 return "indexer";
2612                         if (mc is FieldBase)
2613                                 return "field";
2614                         if (mc is MethodCore)
2615                                 return "method";
2616                         if (mc is EnumMember)
2617                                 return "enum";
2618                         if (mc is Event)
2619                                 return "event";
2620
2621                         return "type";
2622                 }
2623
2624                 public override string GetSignatureForError ()
2625                 {
2626                         if (targs != null) {
2627                                 return Name + "<" + targs.GetSignatureForError () + ">";
2628                         }
2629
2630                         return Name;
2631                 }
2632
2633                 public abstract Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restriction);
2634         }
2635
2636         /// <summary>
2637         ///   SimpleName expressions are formed of a single word and only happen at the beginning
2638         ///   of a dotted-name.
2639         /// </summary>
2640         public class SimpleName : ATypeNameExpression
2641         {
2642                 public SimpleName (string name, Location l)
2643                         : base (name, l)
2644                 {
2645                 }
2646
2647                 public SimpleName (string name, TypeArguments args, Location l)
2648                         : base (name, args, l)
2649                 {
2650                 }
2651
2652                 public SimpleName (string name, int arity, Location l)
2653                         : base (name, arity, l)
2654                 {
2655                 }
2656
2657                 public SimpleName GetMethodGroup ()
2658                 {
2659                         return new SimpleName (Name, targs, loc);
2660                 }
2661
2662                 protected override Expression DoResolve (ResolveContext rc)
2663                 {
2664                         return SimpleNameResolve (rc, null);
2665                 }
2666
2667                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
2668                 {
2669                         return SimpleNameResolve (ec, right_side);
2670                 }
2671
2672                 public void Error_NameDoesNotExist (ResolveContext rc)
2673                 {
2674                         rc.Report.Error (103, loc, "The name `{0}' does not exist in the current context", Name);
2675                 }
2676
2677                 protected virtual void Error_TypeOrNamespaceNotFound (IMemberContext ctx)
2678                 {
2679                         if (ctx.CurrentType != null) {
2680                                 var member = MemberLookup (ctx, false, ctx.CurrentType, Name, 0, MemberLookupRestrictions.ExactArity, loc) as MemberExpr;
2681                                 if (member != null) {
2682                                         Error_UnexpectedKind (ctx, member, "type", member.KindName, loc);
2683                                         return;
2684                                 }
2685                         }
2686
2687                         var report = ctx.Module.Compiler.Report;
2688
2689                         var retval = ctx.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2690                         if (retval != null) {
2691                                 report.SymbolRelatedToPreviousError (retval.Type);
2692                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
2693                                 return;
2694                         }
2695
2696                         retval = ctx.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2697                         if (retval != null) {
2698                                 Error_TypeArgumentsCannotBeUsed (ctx, retval.Type, loc);
2699                                 return;
2700                         }
2701
2702                         var ns_candidates = ctx.Module.GlobalRootNamespace.FindTypeNamespaces (ctx, Name, Arity);
2703                         if (ns_candidates != null) {
2704                                 if (ctx is UsingAliasNamespace.AliasContext) {
2705                                         report.Error (246, loc,
2706                                                 "The type or namespace name `{1}' could not be found. Consider using fully qualified name `{0}.{1}'",
2707                                                 ns_candidates[0], Name);
2708                                 } else {
2709                                         string usings = string.Join ("' or `", ns_candidates.ToArray ());
2710                                         report.Error (246, loc,
2711                                                 "The type or namespace name `{0}' could not be found. Are you missing `{1}' using directive?",
2712                                                 Name, usings);
2713                                 }
2714                         } else {
2715                                 report.Error (246, loc,
2716                                         "The type or namespace name `{0}' could not be found. Are you missing an assembly reference?",
2717                                         Name);
2718                         }
2719                 }
2720
2721                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
2722                 {
2723                         FullNamedExpression fne = mc.LookupNamespaceOrType (Name, Arity, LookupMode.Normal, loc);
2724
2725                         if (fne != null) {
2726                                 if (fne.Type != null && Arity > 0) {
2727                                         if (HasTypeArguments) {
2728                                                 GenericTypeExpr ct = new GenericTypeExpr (fne.Type, targs, loc);
2729                                                 if (ct.ResolveAsType (mc) == null)
2730                                                         return null;
2731
2732                                                 return ct;
2733                                         }
2734
2735                                         targs.Resolve (mc, allowUnboundTypeArguments);
2736
2737                                         return new GenericOpenTypeExpr (fne.Type, loc);
2738                                 }
2739
2740                                 //
2741                                 // dynamic namespace is ignored when dynamic is allowed (does not apply to types)
2742                                 //
2743                                 if (!(fne is NamespaceExpression))
2744                                         return fne;
2745                         }
2746
2747                         if (Arity == 0 && Name == "dynamic" && !(mc is NamespaceContainer) && mc.Module.Compiler.Settings.Version > LanguageVersion.V_3) {
2748                                 if (!mc.Module.PredefinedAttributes.Dynamic.IsDefined) {
2749                                         mc.Module.Compiler.Report.Error (1980, Location,
2750                                                 "Dynamic keyword requires `{0}' to be defined. Are you missing System.Core.dll assembly reference?",
2751                                                 mc.Module.PredefinedAttributes.Dynamic.GetSignatureForError ());
2752                                 }
2753
2754                                 fne = new DynamicTypeExpr (loc);
2755                                 fne.ResolveAsType (mc);
2756                         }
2757
2758                         if (fne != null)
2759                                 return fne;
2760
2761                         Error_TypeOrNamespaceNotFound (mc);
2762                         return null;
2763                 }
2764
2765                 public bool IsPossibleTypeOrNamespace (IMemberContext mc)
2766                 {
2767                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
2768                 }
2769
2770                 public bool IsPossibleType (IMemberContext mc)
2771                 {
2772                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) is TypeExpr;
2773                 }
2774
2775                 public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
2776                 {
2777                         int lookup_arity = Arity;
2778                         bool errorMode = false;
2779                         Expression e;
2780                         Block current_block = rc.CurrentBlock;
2781                         INamedBlockVariable variable = null;
2782                         bool variable_found = false;
2783
2784                         while (true) {
2785                                 //
2786                                 // Stage 1: binding to local variables or parameters
2787                                 //
2788                                 // LAMESPEC: It should take invocableOnly into account but that would break csc compatibility
2789                                 //
2790                                 if (current_block != null && lookup_arity == 0) {
2791                                         if (current_block.ParametersBlock.TopBlock.GetLocalName (Name, current_block.Original, ref variable)) {
2792                                                 if (!variable.IsDeclared) {
2793                                                         // We found local name in accessible block but it's not
2794                                                         // initialized yet, maybe the user wanted to bind to something else
2795                                                         errorMode = true;
2796                                                         variable_found = true;
2797                                                 } else {
2798                                                         e = variable.CreateReferenceExpression (rc, loc);
2799                                                         if (e != null) {
2800                                                                 if (Arity > 0)
2801                                                                         Error_TypeArgumentsCannotBeUsed (rc, "variable", Name, loc);
2802
2803                                                                 return e;
2804                                                         }
2805                                                 }
2806                                         }
2807                                 }
2808
2809                                 //
2810                                 // Stage 2: Lookup members if we are inside a type up to top level type for nested types
2811                                 //
2812                                 TypeSpec member_type = rc.CurrentType;
2813                                 for (; member_type != null; member_type = member_type.DeclaringType) {
2814                                         e = MemberLookup (rc, errorMode, member_type, Name, lookup_arity, restrictions, loc);
2815                                         if (e == null)
2816                                                 continue;
2817
2818                                         var me = e as MemberExpr;
2819                                         if (me == null) {
2820                                                 // The name matches a type, defer to ResolveAsTypeStep
2821                                                 if (e is TypeExpr)
2822                                                         break;
2823
2824                                                 continue;
2825                                         }
2826
2827                                         if (errorMode) {
2828                                                 if (variable != null) {
2829                                                         if (me is FieldExpr || me is ConstantExpr || me is EventExpr || me is PropertyExpr) {
2830                                                                 rc.Report.Error (844, loc,
2831                                                                         "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the member `{1}'",
2832                                                                         Name, me.GetSignatureForError ());
2833                                                         } else {
2834                                                                 break;
2835                                                         }
2836                                                 } else if (me is MethodGroupExpr || me is PropertyExpr || me is IndexerExpr) {
2837                                                         // Leave it to overload resolution to report correct error
2838                                                 } else {
2839                                                         // TODO: rc.Report.SymbolRelatedToPreviousError ()
2840                                                         ErrorIsInaccesible (rc, me.GetSignatureForError (), loc);
2841                                                 }
2842                                         } else {
2843                                                 //
2844                                                 // MemberLookup does not check accessors availability, this is actually needed for properties only
2845                                                 //
2846                                                 var pe = me as PropertyExpr;
2847                                                 if (pe != null) {
2848
2849                                                         // Break as there is no other overload available anyway
2850                                                         if ((restrictions & MemberLookupRestrictions.ReadAccess) != 0) {
2851                                                                 if (!pe.PropertyInfo.HasGet || !pe.PropertyInfo.Get.IsAccessible (rc))
2852                                                                         break;
2853
2854                                                                 pe.Getter = pe.PropertyInfo.Get;
2855                                                         } else {
2856                                                                 if (!pe.PropertyInfo.HasSet) {
2857                                                                         if (rc.HasSet (ResolveContext.Options.ConstructorScope) && pe.IsAutoPropertyAccess &&
2858                                                                                 pe.PropertyInfo.DeclaringType == rc.CurrentType && pe.IsStatic == rc.IsStatic) {
2859                                                                                 var p = (Property) pe.PropertyInfo.MemberDefinition;
2860                                                                                 return new FieldExpr (p.BackingField, loc);
2861                                                                         }
2862
2863                                                                         variable_found = true;
2864                                                                         break;
2865                                                                 }
2866
2867                                                                 if (!pe.PropertyInfo.Set.IsAccessible (rc)) {
2868                                                                         variable_found = true;
2869                                                                         break;
2870                                                                 }
2871
2872                                                                 pe.Setter = pe.PropertyInfo.Set;
2873                                                         }
2874                                                 }
2875                                         }
2876
2877                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2878                                         // TODO: Should go to MemberAccess
2879                                         me = me.ResolveMemberAccess (rc, null, null);
2880
2881                                         if (Arity > 0) {
2882                                                 targs.Resolve (rc, false);
2883                                                 me.SetTypeArguments (rc, targs);
2884                                         }
2885
2886                                         return me;
2887                                 }
2888
2889                                 var expr = NamespaceContainer.LookupStaticUsings (rc, Name, Arity, loc);
2890                                 if (expr != null) {
2891                                         if (Arity > 0) {
2892                                                 targs.Resolve (rc, false);
2893
2894                                                 var me = expr as MemberExpr;
2895                                                 if (me != null)
2896                                                         me.SetTypeArguments (rc, targs);
2897                                         }
2898                                         return expr;
2899                                 }
2900
2901                                 //
2902                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2903                                 //
2904                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2905                                         if (IsPossibleTypeOrNamespace (rc)) {
2906                                                 return ResolveAsTypeOrNamespace (rc, false);
2907                                         }
2908                                 }
2909
2910                                 if ((restrictions & MemberLookupRestrictions.NameOfExcluded) == 0 && Name == "nameof")
2911                                         return new NameOf (this);
2912
2913                                 if (errorMode) {
2914                                         if (variable_found) {
2915                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2916                                         } else {
2917                                                 if (Arity > 0) {
2918                                                         var tparams = rc.CurrentTypeParameters;
2919                                                         if (tparams != null) {
2920                                                                 if (tparams.Find (Name) != null) {
2921                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2922                                                                         return null;
2923                                                                 }
2924                                                         }
2925
2926                                                         var ct = rc.CurrentType;
2927                                                         do {
2928                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2929                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2930                                                                                 if (ctp.Name == Name) {
2931                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2932                                                                                         return null;
2933                                                                                 }
2934                                                                         }
2935                                                                 }
2936
2937                                                                 ct = ct.DeclaringType;
2938                                                         } while (ct != null);
2939                                                 }
2940
2941                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2942                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2943                                                         if (e != null) {
2944                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2945                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2946                                                                 return e;
2947                                                         }
2948                                                 } else {
2949                                                         var me = MemberLookup (rc, false, rc.CurrentType, Name, Arity, restrictions & ~MemberLookupRestrictions.InvocableOnly, loc) as MemberExpr;
2950                                                         if (me != null) {
2951                                                                 Error_UnexpectedKind (rc, me, "method group", me.KindName, loc);
2952                                                                 return ErrorExpression.Instance;
2953                                                         }
2954                                                 }
2955
2956                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2957                                                 if (e != null) {
2958                                                         if (e.Type.Arity != Arity && (restrictions & MemberLookupRestrictions.IgnoreArity) == 0) {
2959                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, loc);
2960                                                                 return e;
2961                                                         }
2962
2963                                                         if (e is TypeExpr) {
2964                                                                 // TypeExpression does not have correct location
2965                                                                 if (e is TypeExpression)
2966                                                                         e = new TypeExpression (e.Type, loc);
2967
2968                                                                 return e;
2969                                                         }
2970                                                 }
2971
2972                                                 Error_NameDoesNotExist (rc);
2973                                         }
2974
2975                                         return ErrorExpression.Instance;
2976                                 }
2977
2978                                 if (rc.Module.Evaluator != null) {
2979                                         var fi = rc.Module.Evaluator.LookupField (Name);
2980                                         if (fi != null)
2981                                                 return new FieldExpr (fi.Item1, loc);
2982                                 }
2983
2984                                 lookup_arity = 0;
2985                                 errorMode = true;
2986                         }
2987                 }
2988
2989                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side)
2990                 {
2991                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2992
2993                         if (e == null)
2994                                 return null;
2995
2996                         if (e is FullNamedExpression && e.eclass != ExprClass.Unresolved) {
2997                                 Error_UnexpectedKind (ec, e, "variable", e.ExprClassName, loc);
2998                                 return e;
2999                         }
3000
3001                         if (right_side != null) {
3002                                 e = e.ResolveLValue (ec, right_side);
3003                         } else {
3004                                 e = e.Resolve (ec);
3005                         }
3006
3007                         return e;
3008                 }
3009
3010                 public override object Accept (StructuralVisitor visitor)
3011                 {
3012                         return visitor.Visit (this);
3013                 }
3014         }
3015
3016         /// <summary>
3017         ///   Represents a namespace or a type.  The name of the class was inspired by
3018         ///   section 10.8.1 (Fully Qualified Names).
3019         /// </summary>
3020         public abstract class FullNamedExpression : Expression
3021         {
3022                 protected override void CloneTo (CloneContext clonectx, Expression target)
3023                 {
3024                         // Do nothing, most unresolved type expressions cannot be
3025                         // resolved to different type
3026                 }
3027
3028                 public override bool ContainsEmitWithAwait ()
3029                 {
3030                         return false;
3031                 }
3032
3033                 public override Expression CreateExpressionTree (ResolveContext ec)
3034                 {
3035                         throw new NotSupportedException ("ET");
3036                 }
3037
3038                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments);
3039
3040                 //
3041                 // This is used to resolve the expression as a type, a null
3042                 // value will be returned if the expression is not a type
3043                 // reference
3044                 //
3045                 public override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
3046                 {
3047                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc, allowUnboundTypeArguments);
3048
3049                         if (fne == null)
3050                                 return null;
3051
3052                         TypeExpr te = fne as TypeExpr;
3053                         if (te == null) {
3054                                 Error_UnexpectedKind (mc, fne, "type", fne.ExprClassName, loc);
3055                                 return null;
3056                         }
3057
3058                         te.loc = loc;
3059
3060                         type = te.Type;
3061
3062                         var dep = type.GetMissingDependencies ();
3063                         if (dep != null) {
3064                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
3065                         }
3066
3067                         if (type.Kind == MemberKind.Void) {
3068                                 mc.Module.Compiler.Report.Error (673, loc, "System.Void cannot be used from C#. Consider using `void'");
3069                         }
3070
3071                         //
3072                         // Obsolete checks cannot be done when resolving base context as they
3073                         // require type dependencies to be set but we are in process of resolving them
3074                         //
3075                         if (mc is ResolveContext) {
3076                                 var oa = type.GetAttributeObsolete ();
3077                                 if (oa != null && !mc.IsObsolete)
3078                                         AttributeTester.Report_ObsoleteMessage (oa, type.GetSignatureForError (), fne.Location, mc.Module.Compiler.Report);
3079                         }
3080
3081                         return type;
3082                 }
3083
3084
3085                 public override void Emit (EmitContext ec)
3086                 {
3087                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
3088                                 GetSignatureForError ());
3089                 }
3090         }
3091
3092         /// <summary>
3093         ///   Expression that evaluates to a type
3094         /// </summary>
3095         public abstract class TypeExpr : FullNamedExpression
3096         {
3097                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
3098                 {
3099                         ResolveAsType (mc);
3100                         return this;
3101                 }
3102
3103                 protected sealed override Expression DoResolve (ResolveContext ec)
3104                 {
3105                         ResolveAsType (ec);
3106                         return this;
3107                 }
3108
3109                 public override bool Equals (object obj)
3110                 {
3111                         TypeExpr tobj = obj as TypeExpr;
3112                         if (tobj == null)
3113                                 return false;
3114
3115                         return Type == tobj.Type;
3116                 }
3117
3118                 public override int GetHashCode ()
3119                 {
3120                         return Type.GetHashCode ();
3121                 }
3122         }
3123
3124         /// <summary>
3125         ///   Fully resolved Expression that already evaluated to a type
3126         /// </summary>
3127         public class TypeExpression : TypeExpr
3128         {
3129                 public TypeExpression (TypeSpec t, Location l)
3130                 {
3131                         Type = t;
3132                         eclass = ExprClass.Type;
3133                         loc = l;
3134                 }
3135
3136                 public sealed override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
3137                 {
3138                         return type;
3139                 }
3140         }
3141
3142         public class NamespaceExpression : FullNamedExpression
3143         {
3144                 readonly Namespace ns;
3145
3146                 public NamespaceExpression (Namespace ns, Location loc)
3147                 {
3148                         this.ns = ns;
3149                         this.Type = InternalType.Namespace;
3150                         this.eclass = ExprClass.Namespace;
3151                         this.loc = loc;
3152                 }
3153
3154                 public Namespace Namespace {
3155                         get {
3156                                 return ns;
3157                         }
3158                 }
3159
3160                 protected override Expression DoResolve (ResolveContext rc)
3161                 {
3162                         throw new NotImplementedException ();
3163                 }
3164
3165                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
3166                 {
3167                         return this;
3168                 }
3169
3170                 public void Error_NamespaceDoesNotExist (IMemberContext ctx, string name, int arity, Location loc)
3171                 {
3172                         var retval = Namespace.LookupType (ctx, name, arity, LookupMode.IgnoreAccessibility, loc);
3173                         if (retval != null) {
3174 //                              ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (retval.MemberDefinition);
3175                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
3176                                 return;
3177                         }
3178
3179                         retval = Namespace.LookupType (ctx, name, -System.Math.Max (1, arity), LookupMode.Probing, loc);
3180                         if (retval != null) {
3181                                 Error_TypeArgumentsCannotBeUsed (ctx, retval, loc);
3182                                 return;
3183                         }
3184
3185                         Namespace ns;
3186                         if (arity > 0 && Namespace.TryGetNamespace (name, out ns)) {
3187                                 Error_TypeArgumentsCannotBeUsed (ctx, ExprClassName, ns.GetSignatureForError (), loc);
3188                                 return;
3189                         }
3190
3191                         string assembly = null;
3192                         string possible_name = Namespace.GetSignatureForError () + "." + name;
3193
3194                         // Only assembly unique name should be added
3195                         switch (possible_name) {
3196                         case "System.Drawing":
3197                         case "System.Web.Services":
3198                         case "System.Web":
3199                         case "System.Data":
3200                         case "System.Configuration":
3201                         case "System.Data.Services":
3202                         case "System.DirectoryServices":
3203                         case "System.Json":
3204                         case "System.Net.Http":
3205                         case "System.Numerics":
3206                         case "System.Runtime.Caching":
3207                         case "System.ServiceModel":
3208                         case "System.Transactions":
3209                         case "System.Web.Routing":
3210                         case "System.Xml.Linq":
3211                         case "System.Xml":
3212                                 assembly = possible_name;
3213                                 break;
3214
3215                         case "System.Linq":
3216                         case "System.Linq.Expressions":
3217                                 assembly = "System.Core";
3218                                 break;
3219
3220                         case "System.Windows.Forms":
3221                         case "System.Windows.Forms.Layout":
3222                                 assembly = "System.Windows.Forms";
3223                                 break;
3224                         }
3225
3226                         assembly = assembly == null ? "an" : "`" + assembly + "'";
3227
3228                         if (Namespace is GlobalRootNamespace) {
3229                                 ctx.Module.Compiler.Report.Error (400, loc,
3230                                         "The type or namespace name `{0}' could not be found in the global namespace. Are you missing {1} assembly reference?",
3231                                         name, assembly);
3232                         } else {
3233                                 ctx.Module.Compiler.Report.Error (234, loc,
3234                                         "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing {2} assembly reference?",
3235                                         name, GetSignatureForError (), assembly);
3236                         }
3237                 }
3238
3239                 public override string GetSignatureForError ()
3240                 {
3241                         return ns.GetSignatureForError ();
3242                 }
3243
3244                 public FullNamedExpression LookupTypeOrNamespace (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
3245                 {
3246                         return ns.LookupTypeOrNamespace (ctx, name, arity, mode, loc);
3247                 }
3248
3249                 public override string ToString ()
3250                 {
3251                         return Namespace.Name;
3252                 }
3253     }
3254
3255         /// <summary>
3256         ///   This class denotes an expression which evaluates to a member
3257         ///   of a struct or a class.
3258         /// </summary>
3259         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
3260         {
3261                 protected bool conditional_access_receiver;
3262
3263                 //
3264                 // An instance expression associated with this member, if it's a
3265                 // non-static member
3266                 //
3267                 public Expression InstanceExpression;
3268
3269                 /// <summary>
3270                 ///   The name of this member.
3271                 /// </summary>
3272                 public abstract string Name {
3273                         get;
3274                 }
3275
3276                 //
3277                 // When base.member is used
3278                 //
3279                 public bool IsBase {
3280                         get { return InstanceExpression is BaseThis; }
3281                 }
3282
3283                 /// <summary>
3284                 ///   Whether this is an instance member.
3285                 /// </summary>
3286                 public abstract bool IsInstance {
3287                         get;
3288                 }
3289
3290                 /// <summary>
3291                 ///   Whether this is a static member.
3292                 /// </summary>
3293                 public abstract bool IsStatic {
3294                         get;
3295                 }
3296
3297                 public abstract string KindName {
3298                         get;
3299                 }
3300
3301                 public bool ConditionalAccess { get; set; }
3302
3303                 protected abstract TypeSpec DeclaringType {
3304                         get;
3305                 }
3306
3307                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
3308                         get {
3309                                 return InstanceExpression.Type;
3310                         }
3311                 }
3312
3313                 //
3314                 // Converts best base candidate for virtual method starting from QueriedBaseType
3315                 //
3316                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
3317                 {
3318                         //
3319                         // Only when base.member is used and method is virtual
3320                         //
3321                         if (!IsBase)
3322                                 return method;
3323
3324                         //
3325                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
3326                         // means for base.member access we have to find the closest match after we found best candidate
3327                         //
3328                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
3329                                 //
3330                                 // The method could already be what we are looking for
3331                                 //
3332                                 TypeSpec[] targs = null;
3333                                 if (method.DeclaringType != InstanceExpression.Type) {
3334                                         //
3335                                         // Candidate can have inflated MVAR parameters and we need to find
3336                                         // base match for original definition not inflated parameter types
3337                                         //
3338                                         var parameters = method.Parameters;
3339                                         if (method.Arity > 0) {
3340                                                 parameters = ((IParametersMember) method.MemberDefinition).Parameters;
3341                                                 var inflated = method.DeclaringType as InflatedTypeSpec;
3342                                                 if (inflated != null) {
3343                                                         parameters = parameters.Inflate (inflated.CreateLocalInflator (rc));
3344                                                 }
3345                                         }
3346
3347                                         var filter = new MemberFilter (method.Name, method.Arity, MemberKind.Method, parameters, null);
3348                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as MethodSpec;
3349                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
3350                                                 if (base_override.IsGeneric)
3351                                                         targs = method.TypeArguments;
3352
3353                                                 method = base_override;
3354                                         }
3355                                 }
3356
3357                                 //
3358                                 // When base access is used inside anonymous method/iterator/etc we need to
3359                                 // get back to the context of original type. We do it by emiting proxy
3360                                 // method in original class and rewriting base call to this compiler
3361                                 // generated method call which does the actual base invocation. This may
3362                                 // introduce redundant storey but with `this' only but it's tricky to avoid
3363                                 // at this stage as we don't know what expressions follow base
3364                                 //
3365                                 // TODO: It's needed only when the method with base call is moved to a storey
3366                                 //
3367                                 if (rc.CurrentAnonymousMethod != null) {
3368                                         if (targs == null && method.IsGeneric) {
3369                                                 targs = method.TypeArguments;
3370                                                 method = method.GetGenericMethodDefinition ();
3371                                         }
3372
3373                                         if (method.Parameters.HasArglist)
3374                                                 throw new NotImplementedException ("__arglist base call proxy");
3375
3376                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
3377
3378                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
3379                                         // get/set member expressions second call would fail to proxy because left expression
3380                                         // would be of 'this' and not 'base' because we share InstanceExpression for get/set
3381                                         // FIXME: The async check is another hack but will probably fail with mutators
3382                                         if (rc.CurrentType.IsStruct || rc.CurrentAnonymousMethod.Storey is AsyncTaskStorey)
3383                                                 InstanceExpression = new This (loc).Resolve (rc);
3384                                 }
3385
3386                                 if (targs != null)
3387                                         method = method.MakeGenericMethod (rc, targs);
3388                         }
3389
3390                         //
3391                         // Only base will allow this invocation to happen.
3392                         //
3393                         if (method.IsAbstract) {
3394                                 rc.Report.SymbolRelatedToPreviousError (method);
3395                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
3396                         }
3397
3398                         return method;
3399                 }
3400
3401                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3402                 {
3403                         if (InstanceExpression == null)
3404                                 return;
3405
3406                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
3407                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
3408                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
3409                                 }
3410                         }
3411                 }
3412
3413                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3414                 {
3415                         if (InstanceExpression == null)
3416                                 return true;
3417
3418                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
3419                 }
3420
3421                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
3422                 {
3423                         var ct = rc.CurrentType;
3424                         if (ct == qualifier)
3425                                 return true;
3426
3427                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
3428                                 return true;
3429
3430                         qualifier = qualifier.GetDefinition ();
3431                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
3432                                 return false;
3433                         }
3434
3435                         return true;
3436                 }
3437
3438                 public override bool ContainsEmitWithAwait ()
3439                 {
3440                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
3441                 }
3442
3443                 public override bool HasConditionalAccess ()
3444                 {
3445                         return ConditionalAccess || (InstanceExpression != null && InstanceExpression.HasConditionalAccess ());
3446                 }
3447
3448                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
3449                 {
3450                         do {
3451                                 type = type.GetDefinition ();
3452
3453                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
3454                                         return true;
3455
3456                                 type = type.DeclaringType;
3457                         } while (type != null);
3458
3459                         return false;
3460                 }
3461
3462                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
3463                 {
3464                         if (InstanceExpression != null) {
3465                                 InstanceExpression = InstanceExpression.Resolve (rc);
3466                                 CheckProtectedMemberAccess (rc, member);
3467                         }
3468
3469                         if (member.MemberType.IsPointer) {
3470                                 if (rc.CurrentIterator != null) {
3471                                         UnsafeInsideIteratorError (rc, loc);
3472                                 } else if (!rc.IsUnsafe) {
3473                                         UnsafeError (rc, loc);
3474                                 }
3475                         }
3476
3477                         var dep = member.GetMissingDependencies ();
3478                         if (dep != null) {
3479                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
3480                         }
3481
3482                         member.CheckObsoleteness (rc, loc);
3483
3484                         if (!(member is FieldSpec))
3485                                 member.MemberDefinition.SetIsUsed ();
3486                 }
3487
3488                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
3489                 {
3490                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
3491                 }
3492
3493                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
3494                 {
3495                         rc.Report.SymbolRelatedToPreviousError (member);
3496                         rc.Report.Error (1540, loc,
3497                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
3498                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3499                 }
3500
3501                 public override void FlowAnalysis (FlowAnalysisContext fc)
3502                 {
3503                         if (InstanceExpression != null) {
3504                                 InstanceExpression.FlowAnalysis (fc);
3505                         }
3506                 }
3507
3508                 protected void ResolveConditionalAccessReceiver (ResolveContext rc)
3509                 {
3510                         if (!rc.HasSet (ResolveContext.Options.DontSetConditionalAccessReceiver) && HasConditionalAccess ()) {
3511                                 conditional_access_receiver = true;
3512                         }
3513                 }
3514
3515                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
3516                 {
3517                         if (!ResolveInstanceExpressionCore (rc, rhs))
3518                                 return false;
3519
3520                         //
3521                         // Check intermediate value modification which won't have any effect
3522                         //
3523                         if (rhs != null && TypeSpec.IsValueType (InstanceExpression.Type)) {
3524                                 var fexpr = InstanceExpression as FieldExpr;
3525                                 if (fexpr != null) {
3526                                         if (!fexpr.Spec.IsReadOnly || rc.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
3527                                                 return true;
3528
3529                                         if (fexpr.IsStatic) {
3530                                                 rc.Report.Error (1650, loc, "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
3531                                                         fexpr.GetSignatureForError ());
3532                                         } else {
3533                                                 rc.Report.Error (1648, loc, "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
3534                                                         fexpr.GetSignatureForError ());
3535                                         }
3536
3537                                         return true;
3538                                 }
3539
3540                                 if (InstanceExpression is PropertyExpr || InstanceExpression is IndexerExpr || InstanceExpression is Invocation) {
3541                                         if (rc.CurrentInitializerVariable != null) {
3542                                                 rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
3543                                                         InstanceExpression.Type.GetSignatureForError (), InstanceExpression.GetSignatureForError ());
3544                                         } else {
3545                                                 rc.Report.Error (1612, loc,
3546                                                         "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
3547                                                         InstanceExpression.GetSignatureForError ());
3548                                         }
3549
3550                                         return true;
3551                                 }
3552
3553                                 var lvr = InstanceExpression as LocalVariableReference;
3554                                 if (lvr != null) {
3555
3556                                         if (!lvr.local_info.IsReadonly)
3557                                                 return true;
3558
3559                                         rc.Report.Error (1654, loc, "Cannot assign to members of `{0}' because it is a `{1}'",
3560                                                 InstanceExpression.GetSignatureForError (), lvr.local_info.GetReadOnlyContext ());
3561                                 }
3562                         }
3563
3564                         return true;
3565                 }
3566
3567                 bool ResolveInstanceExpressionCore (ResolveContext rc, Expression rhs)
3568                 {
3569                         if (IsStatic) {
3570                                 if (InstanceExpression != null) {
3571                                         if (InstanceExpression is TypeExpr) {
3572                                                 var t = InstanceExpression.Type;
3573                                                 do {
3574                                                         t.CheckObsoleteness (rc, loc);
3575
3576                                                         t = t.DeclaringType;
3577                                                 } while (t != null);
3578                                         } else {
3579                                                 var runtime_expr = InstanceExpression as RuntimeValueExpression;
3580                                                 if (runtime_expr == null || !runtime_expr.IsSuggestionOnly) {
3581                                                         rc.Report.Error (176, loc,
3582                                                                 "Static member `{0}' cannot be accessed with an instance reference, qualify it with a type name instead",
3583                                                                 GetSignatureForError ());
3584                                                 }
3585                                         }
3586
3587                                         InstanceExpression = null;
3588                                 }
3589
3590                                 return false;
3591                         }
3592
3593                         if (InstanceExpression == null || InstanceExpression is TypeExpr) {
3594                                 if (InstanceExpression != null || !This.IsThisAvailable (rc, true)) {
3595                                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope)) {
3596                                                 rc.Report.Error (236, loc,
3597                                                         "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
3598                                                         GetSignatureForError ());
3599                                         } else {
3600                                                 var fe = this as FieldExpr;
3601                                                 if (fe != null && fe.Spec.MemberDefinition is PrimaryConstructorField) {
3602                                                         if (rc.HasSet (ResolveContext.Options.BaseInitializer)) {
3603                                                                 rc.Report.Error (9005, loc, "Constructor initializer cannot access primary constructor parameters");
3604                                                         } else  {
3605                                                                 rc.Report.Error (9006, loc, "An object reference is required to access primary constructor parameter `{0}'",
3606                                                                         fe.Name);
3607                                                         }
3608                                                 } else {
3609                                                         rc.Report.Error (120, loc,
3610                                                                 "An object reference is required to access non-static member `{0}'",
3611                                                                 GetSignatureForError ());
3612                                                 }
3613                                         }
3614
3615                                         InstanceExpression = new CompilerGeneratedThis (rc.CurrentType, loc).Resolve (rc);
3616                                         return false;
3617                                 }
3618
3619                                 if (!TypeManager.IsFamilyAccessible (rc.CurrentType, DeclaringType)) {
3620                                         rc.Report.Error (38, loc,
3621                                                 "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
3622                                                 DeclaringType.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3623                                 }
3624
3625                                 InstanceExpression = new This (loc).Resolve (rc);
3626                                 return false;
3627                         }
3628
3629                         var me = InstanceExpression as MemberExpr;
3630                         if (me != null) {
3631                                 me.ResolveInstanceExpressionCore (rc, rhs);
3632
3633                                 var fe = me as FieldExpr;
3634                                 if (fe != null && fe.IsMarshalByRefAccess (rc)) {
3635                                         rc.Report.SymbolRelatedToPreviousError (me.DeclaringType);
3636                                         rc.Report.Warning (1690, 1, loc,
3637                                                 "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
3638                                                 me.GetSignatureForError ());
3639                                 }
3640
3641                                 return true;
3642                         }
3643
3644                         //
3645                         // Additional checks for l-value member access
3646                         //
3647                         if (rhs != null) {
3648                                 if (InstanceExpression is UnboxCast) {
3649                                         rc.Report.Error (445, InstanceExpression.Location, "Cannot modify the result of an unboxing conversion");
3650                                 }
3651                         }
3652
3653                         return true;
3654                 }
3655
3656                 public virtual MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3657                 {
3658                         if (left != null && !ConditionalAccess && !ec.HasSet (ResolveContext.Options.NameOfScope) && left.IsNull && TypeSpec.IsReferenceType (left.Type)) {
3659                                 ec.Report.Warning (1720, 1, left.Location,
3660                                         "Expression will always cause a `{0}'", "System.NullReferenceException");
3661                         }
3662
3663                         InstanceExpression = left;
3664                         return this;
3665                 }
3666
3667                 public virtual void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
3668                 {
3669
3670                 }
3671
3672                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
3673                 {
3674                         var inst = new InstanceEmitter (InstanceExpression, TypeSpec.IsValueType (InstanceExpression.Type));
3675                         inst.Emit (ec, ConditionalAccess);
3676
3677                         if (prepare_for_load)
3678                                 ec.Emit (OpCodes.Dup);
3679                 }
3680
3681                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3682         }
3683
3684         public class ExtensionMethodCandidates
3685         {
3686                 readonly NamespaceContainer container;
3687                 readonly IList<MethodSpec> methods;
3688                 readonly int index;
3689                 readonly IMemberContext context;
3690
3691                 public ExtensionMethodCandidates (IMemberContext context, IList<MethodSpec> methods, NamespaceContainer nsContainer, int lookupIndex)
3692                 {
3693                         this.context = context;
3694                         this.methods = methods;
3695                         this.container = nsContainer;
3696                         this.index = lookupIndex;
3697                 }
3698
3699                 public NamespaceContainer Container {
3700                         get {
3701                                 return container;
3702                         }
3703                 }
3704
3705                 public IMemberContext Context {
3706                         get {
3707                                 return context;
3708                         }
3709                 }
3710
3711                 public int LookupIndex {
3712                         get {
3713                                 return index;
3714                         }
3715                 }
3716
3717                 public IList<MethodSpec> Methods {
3718                         get {
3719                                 return methods;
3720                         }
3721                 }
3722         }
3723
3724         //
3725         // Represents a group of extension method candidates for whole namespace
3726         //
3727         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3728         {
3729                 ExtensionMethodCandidates candidates;
3730                 public Expression ExtensionExpression;
3731
3732                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3733                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3734                 {
3735                         this.candidates = candidates;
3736                         this.ExtensionExpression = extensionExpr;
3737                 }
3738
3739                 public override bool IsStatic {
3740                         get { return true; }
3741                 }
3742
3743                 //
3744                 // For extension methodgroup we are not looking for base members but parent
3745                 // namespace extension methods
3746                 //
3747                 public override IList<MemberSpec> GetBaseMembers (TypeSpec type)
3748                 {
3749                         // TODO: candidates are null only when doing error reporting, that's
3750                         // incorrect. We have to discover same extension methods in error mode
3751                         if (candidates == null)
3752                                 return null;
3753
3754                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3755
3756                         candidates = candidates.Container.LookupExtensionMethod (candidates.Context, Name, arity, candidates.LookupIndex);
3757                         if (candidates == null)
3758                                 return null;
3759
3760                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3761                 }
3762
3763                 public static bool IsExtensionTypeCompatible (TypeSpec argType, TypeSpec extensionType)
3764                 {
3765                         //
3766                         // Indentity, implicit reference or boxing conversion must exist for the extension parameter
3767                         //
3768                         // LAMESPEC: or implicit type parameter conversion
3769                         //
3770                         return argType == extensionType ||
3771                                 TypeSpecComparer.IsEqual (argType, extensionType) ||
3772                                 Convert.ImplicitReferenceConversionExists (argType, extensionType, false) ||
3773                                 Convert.ImplicitBoxingConversion (null, argType, extensionType) != null;
3774                 }
3775
3776                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
3777                 {
3778                         rc.Report.Error (8093, expr.Location, "An argument to nameof operator cannot be extension method group");
3779                 }
3780
3781                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3782                 {
3783                         // We are already here
3784                         return null;
3785                 }
3786
3787                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3788                 {
3789                         if (arguments == null)
3790                                 arguments = new Arguments (1);
3791
3792                         ExtensionExpression = ExtensionExpression.Resolve (ec);
3793                         if (ExtensionExpression == null)
3794                                 return null;
3795
3796                         var cand = candidates;
3797                         var atype = ConditionalAccess ? Argument.AType.ExtensionTypeConditionalAccess : Argument.AType.ExtensionType;
3798                         arguments.Insert (0, new Argument (ExtensionExpression, atype));
3799                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3800
3801                         // Restore candidates in case we are running in probing mode
3802                         candidates = cand;
3803
3804                         // Store resolved argument and restore original arguments
3805                         if (res == null) {
3806                                 // Clean-up modified arguments for error reporting
3807                                 arguments.RemoveAt (0);
3808                                 return null;
3809                         }
3810
3811                         var me = ExtensionExpression as MemberExpr;
3812                         if (me != null) {
3813                                 me.ResolveInstanceExpression (ec, null);
3814                                 var fe = me as FieldExpr;
3815                                 if (fe != null)
3816                                         fe.Spec.MemberDefinition.SetIsUsed ();
3817                         }
3818
3819                         InstanceExpression = null;
3820                         return this;
3821                 }
3822
3823                 #region IErrorHandler Members
3824
3825                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3826                 {
3827                         return false;
3828                 }
3829
3830                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3831                 {
3832                         rc.Report.SymbolRelatedToPreviousError (best);
3833
3834                         if (index == 0) {
3835                                 rc.Report.Error (1929, loc,
3836                                         "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' requires an instance of type `{3}'",
3837                                         queried_type.GetSignatureForError (), Name, best.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3838                         } else {
3839                                 rc.Report.Error (1928, loc,
3840                                         "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3841                                         queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3842                         }
3843
3844                         return true;
3845                 }
3846
3847                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3848                 {
3849                         return false;
3850                 }
3851
3852                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3853                 {
3854                         return false;
3855                 }
3856
3857                 #endregion
3858         }
3859
3860         /// <summary>
3861         ///   MethodGroupExpr represents a group of method candidates which
3862         ///   can be resolved to the best method overload
3863         /// </summary>
3864         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3865         {
3866                 static readonly MemberSpec[] Excluded = new MemberSpec[0];
3867
3868                 protected IList<MemberSpec> Methods;
3869                 MethodSpec best_candidate;
3870                 TypeSpec best_candidate_return;
3871                 protected TypeArguments type_arguments;
3872
3873                 SimpleName simple_name;
3874                 protected TypeSpec queried_type;
3875
3876                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3877                 {
3878                         Methods = mi;
3879                         this.loc = loc;
3880                         this.type = InternalType.MethodGroup;
3881
3882                         eclass = ExprClass.MethodGroup;
3883                         queried_type = type;
3884                 }
3885
3886                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3887                         : this (new MemberSpec[] { m }, type, loc)
3888                 {
3889                 }
3890
3891                 #region Properties
3892
3893                 public MethodSpec BestCandidate {
3894                         get {
3895                                 return best_candidate;
3896                         }
3897                 }
3898
3899                 public TypeSpec BestCandidateReturnType {
3900                         get {
3901                                 return best_candidate_return;
3902                         }
3903                 }
3904
3905                 public IList<MemberSpec> Candidates {
3906                         get {
3907                                 return Methods;
3908                         }
3909                 }
3910
3911                 protected override TypeSpec DeclaringType {
3912                         get {
3913                                 return queried_type;
3914                         }
3915                 }
3916
3917                 public bool IsConditionallyExcluded {
3918                         get {
3919                                 return Methods == Excluded;
3920                         }
3921                 }
3922
3923                 public override bool IsInstance {
3924                         get {
3925                                 if (best_candidate != null)
3926                                         return !best_candidate.IsStatic;
3927
3928                                 return false;
3929                         }
3930                 }
3931
3932                 public override bool IsSideEffectFree {
3933                         get {
3934                                 return InstanceExpression == null || InstanceExpression.IsSideEffectFree;
3935                         }
3936                 }
3937
3938                 public override bool IsStatic {
3939                         get {
3940                                 if (best_candidate != null)
3941                                         return best_candidate.IsStatic;
3942
3943                                 return false;
3944                         }
3945                 }
3946
3947                 public override string KindName {
3948                         get { return "method"; }
3949                 }
3950
3951                 public override string Name {
3952                         get {
3953                                 if (best_candidate != null)
3954                                         return best_candidate.Name;
3955
3956                                 // TODO: throw ?
3957                                 return Methods.First ().Name;
3958                         }
3959                 }
3960
3961                 #endregion
3962
3963                 //
3964                 // When best candidate is already know this factory can be used
3965                 // to avoid expensive overload resolution to be called
3966                 //
3967                 // NOTE: InstanceExpression has to be set manually
3968                 //
3969                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3970                 {
3971                         return new MethodGroupExpr (best, queriedType, loc) {
3972                                 best_candidate = best,
3973                                 best_candidate_return = best.ReturnType
3974                         };
3975                 }
3976
3977                 public override string GetSignatureForError ()
3978                 {
3979                         if (best_candidate != null)
3980                                 return best_candidate.GetSignatureForError ();
3981
3982                         return Methods.First ().GetSignatureForError ();
3983                 }
3984
3985                 public override Expression CreateExpressionTree (ResolveContext ec)
3986                 {
3987                         if (best_candidate == null) {
3988                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3989                                 return null;
3990                         }
3991
3992                         if (IsConditionallyExcluded)
3993                                 ec.Report.Error (765, loc,
3994                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3995
3996                         if (ConditionalAccess)
3997                                 Error_NullShortCircuitInsideExpressionTree (ec);
3998
3999                         return new TypeOfMethod (best_candidate, loc);
4000                 }
4001
4002                 protected override Expression DoResolve (ResolveContext ec)
4003                 {
4004                         this.eclass = ExprClass.MethodGroup;
4005
4006                         if (InstanceExpression != null) {
4007                                 InstanceExpression = InstanceExpression.Resolve (ec);
4008                                 if (InstanceExpression == null)
4009                                         return null;
4010                         }
4011
4012                         return this;
4013                 }
4014
4015                 public override void Emit (EmitContext ec)
4016                 {
4017                         throw new NotSupportedException ();
4018                 }
4019
4020                 public void EmitCall (EmitContext ec, Arguments arguments, bool statement)
4021                 {
4022                         var call = new CallEmitter ();
4023                         call.InstanceExpression = InstanceExpression;
4024                         call.ConditionalAccess = ConditionalAccess;
4025
4026                         if (statement)
4027                                 call.EmitStatement (ec, best_candidate, arguments, loc);
4028                         else
4029                                 call.Emit (ec, best_candidate, arguments, loc);
4030                 }
4031
4032                 public void EmitCall (EmitContext ec, Arguments arguments, TypeSpec conditionalAccessReceiver, bool statement)
4033                 {
4034                         var ca = ec.ConditionalAccess;
4035                         ec.ConditionalAccess = new ConditionalAccessContext (conditionalAccessReceiver, ec.DefineLabel ()) {
4036                                 Statement = statement
4037                         };
4038
4039                         EmitCall (ec, arguments, statement);
4040
4041                         ec.CloseConditionalAccess (!statement && best_candidate_return != conditionalAccessReceiver && conditionalAccessReceiver.IsNullableType ? conditionalAccessReceiver : null);
4042                         ec.ConditionalAccess = ca;
4043                 }
4044
4045                 public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
4046                 {
4047                         if (target != InternalType.ErrorType) {
4048                                 ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
4049                                         Name, target.GetSignatureForError ());
4050                         }
4051                 }
4052
4053                 public bool HasAccessibleCandidate (ResolveContext rc)
4054                 {
4055                         foreach (var candidate in Candidates) {
4056                                 if (candidate.IsAccessible (rc))
4057                                         return true;
4058                         }
4059
4060                         return false;
4061                 }
4062
4063                 public static bool IsExtensionMethodArgument (Expression expr)
4064                 {
4065                         //
4066                         // LAMESPEC: No details about which expressions are not allowed
4067                         //
4068                         return !(expr is TypeExpr) && !(expr is BaseThis);
4069                 }
4070
4071                 /// <summary>
4072                 ///   Find the Applicable Function Members (7.4.2.1)
4073                 ///
4074                 ///   me: Method Group expression with the members to select.
4075                 ///       it might contain constructors or methods (or anything
4076                 ///       that maps to a method).
4077                 ///
4078                 ///   Arguments: ArrayList containing resolved Argument objects.
4079                 ///
4080                 ///   loc: The location if we want an error to be reported, or a Null
4081                 ///        location for "probing" purposes.
4082                 ///
4083                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
4084                 ///            that is the best match of me on Arguments.
4085                 ///
4086                 /// </summary>
4087                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
4088                 {
4089                         // TODO: causes issues with probing mode, remove explicit Kind check
4090                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
4091                                 return this;
4092
4093                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
4094                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
4095                                 r.BaseMembersProvider = this;
4096                                 r.InstanceQualifier = this;
4097                         }
4098
4099                         if (cerrors != null)
4100                                 r.CustomErrors = cerrors;
4101
4102                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
4103                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
4104                         if (best_candidate == null) {
4105                                 if (!r.BestCandidateIsDynamic)
4106                                         return null;
4107
4108                                 if (simple_name != null && ec.IsStatic)
4109                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
4110
4111                                 return this;
4112                         }
4113
4114                         // Overload resolver had to create a new method group, all checks bellow have already been executed
4115                         if (r.BestCandidateNewMethodGroup != null)
4116                                 return r.BestCandidateNewMethodGroup;
4117
4118                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
4119                                 if (InstanceExpression != null) {
4120                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
4121                                                 InstanceExpression = null;
4122                                         } else {
4123                                                 if (simple_name != null && best_candidate.IsStatic) {
4124                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
4125                                                 }
4126
4127                                                 InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup | ResolveFlags.Type);
4128                                         }
4129                                 }
4130
4131                                 ResolveInstanceExpression (ec, null);
4132                         }
4133
4134                         var base_override = CandidateToBaseOverride (ec, best_candidate);
4135                         if (base_override == best_candidate) {
4136                                 best_candidate_return = r.BestCandidateReturnType;
4137                         } else {
4138                                 best_candidate = base_override;
4139                                 best_candidate_return = best_candidate.ReturnType;
4140                         }
4141
4142                         if (best_candidate.IsGeneric && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0 && TypeParameterSpec.HasAnyTypeParameterConstrained (best_candidate.GenericDefinition)) {
4143                                 ConstraintChecker cc = new ConstraintChecker (ec);
4144                                 cc.CheckAll (best_candidate.GetGenericMethodDefinition (), best_candidate.TypeArguments, best_candidate.Constraints, loc);
4145                         }
4146
4147                         //
4148                         // Additional check for possible imported base override method which
4149                         // could not be done during IsOverrideMethodBaseTypeAccessible
4150                         //
4151                         if (best_candidate.IsVirtual && (best_candidate.DeclaringType.Modifiers & Modifiers.PROTECTED) != 0 &&
4152                                 best_candidate.MemberDefinition.IsImported && !best_candidate.DeclaringType.IsAccessible (ec)) {
4153                                 ec.Report.SymbolRelatedToPreviousError (best_candidate);
4154                                 ErrorIsInaccesible (ec, best_candidate.GetSignatureForError (), loc);
4155                         }
4156
4157                         // Speed up the check by not doing it on disallowed targets
4158                         if (best_candidate_return.Kind == MemberKind.Void && best_candidate.IsConditionallyExcluded (ec))
4159                                 Methods = Excluded;
4160
4161                         return this;
4162                 }
4163
4164                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
4165                 {
4166                         var fe = left as FieldExpr;
4167                         if (fe != null) {
4168                                 //
4169                                 // Using method-group on struct fields makes the struct assigned. I am not sure
4170                                 // why but that's what .net does
4171                                 //
4172                                 fe.Spec.MemberDefinition.SetIsAssigned ();
4173                         }
4174
4175                         simple_name = original;
4176                         return base.ResolveMemberAccess (ec, left, original);
4177                 }
4178
4179                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
4180                 {
4181                         if (!HasAccessibleCandidate (rc)) {
4182                                 ErrorIsInaccesible (rc, expr.GetSignatureForError (), loc);
4183                         }
4184
4185                         if (expr.HasTypeArguments) {
4186                                 rc.Report.Error (8084, expr.Location, "An argument to nameof operator cannot be method group with type arguments");
4187                         }
4188                 }
4189
4190                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
4191                 {
4192                         type_arguments = ta;
4193                 }
4194
4195                 #region IBaseMembersProvider Members
4196
4197                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec type)
4198                 {
4199                         var baseType = type.BaseType;
4200
4201                         IList<MemberSpec> members = baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
4202
4203                         if (members == null && !type.IsInterface) {
4204                                 var tps = queried_type as TypeParameterSpec;
4205                                 if (tps != null)
4206                                         members = MemberCache.FindInterfaceMembers (tps, Methods [0].Name);
4207                         }
4208
4209                         return members;
4210                 }
4211
4212                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
4213                 {
4214                         if (queried_type == member.DeclaringType)
4215                                 return null;
4216
4217                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
4218                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
4219                 }
4220
4221                 //
4222                 // Extension methods lookup after ordinary methods candidates failed to apply
4223                 //
4224                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
4225                 {
4226                         if (InstanceExpression == null || InstanceExpression.eclass == ExprClass.Type)
4227                                 return null;
4228
4229                         if (!IsExtensionMethodArgument (InstanceExpression))
4230                                 return null;
4231
4232                         int arity = type_arguments == null ? 0 : type_arguments.Count;
4233                         var methods = rc.LookupExtensionMethod (Methods[0].Name, arity);
4234                         if (methods == null)
4235                                 return null;
4236
4237                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
4238                         emg.SetTypeArguments (rc, type_arguments);
4239                         emg.ConditionalAccess = ConditionalAccess;
4240                         return emg;
4241                 }
4242
4243                 #endregion
4244         }
4245
4246         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
4247         {
4248                 public ConstructorInstanceQualifier (TypeSpec type)
4249                         : this ()
4250                 {
4251                         InstanceType = type;
4252                 }
4253
4254                 public TypeSpec InstanceType { get; private set; }
4255
4256                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
4257                 {
4258                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
4259                 }
4260         }
4261
4262         public struct OverloadResolver
4263         {
4264                 [Flags]
4265                 public enum Restrictions
4266                 {
4267                         None = 0,
4268                         DelegateInvoke = 1,
4269                         ProbingOnly     = 1 << 1,
4270                         CovariantDelegate = 1 << 2,
4271                         NoBaseMembers = 1 << 3,
4272                         BaseMembersIncluded = 1 << 4,
4273                         GetEnumeratorLookup = 1 << 5
4274                 }
4275
4276                 public interface IBaseMembersProvider
4277                 {
4278                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
4279                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
4280                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
4281                 }
4282
4283                 public interface IErrorHandler
4284                 {
4285                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
4286                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
4287                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
4288                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
4289                 }
4290
4291                 public interface IInstanceQualifier
4292                 {
4293                         TypeSpec InstanceType { get; }
4294                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
4295                 }
4296
4297                 sealed class NoBaseMembers : IBaseMembersProvider
4298                 {
4299                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
4300
4301                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
4302                         {
4303                                 return null;
4304                         }
4305
4306                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
4307                         {
4308                                 return null;
4309                         }
4310
4311                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
4312                         {
4313                                 return null;
4314                         }
4315                 }
4316
4317                 struct AmbiguousCandidate
4318                 {
4319                         public readonly MemberSpec Member;
4320                         public readonly bool Expanded;
4321                         public readonly AParametersCollection Parameters;
4322
4323                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
4324                         {
4325                                 Member = member;
4326                                 Parameters = parameters;
4327                                 Expanded = expanded;
4328                         }
4329                 }
4330
4331                 Location loc;
4332                 IList<MemberSpec> members;
4333                 TypeArguments type_arguments;
4334                 IBaseMembersProvider base_provider;
4335                 IErrorHandler custom_errors;
4336                 IInstanceQualifier instance_qualifier;
4337                 Restrictions restrictions;
4338                 MethodGroupExpr best_candidate_extension_group;
4339                 TypeSpec best_candidate_return_type;
4340
4341                 SessionReportPrinter lambda_conv_msgs;
4342
4343                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
4344                         : this (members, null, restrictions, loc)
4345                 {
4346                 }
4347
4348                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
4349                         : this ()
4350                 {
4351                         if (members == null || members.Count == 0)
4352                                 throw new ArgumentException ("empty members set");
4353
4354                         this.members = members;
4355                         this.loc = loc;
4356                         type_arguments = targs;
4357                         this.restrictions = restrictions;
4358                         if (IsDelegateInvoke)
4359                                 this.restrictions |= Restrictions.NoBaseMembers;
4360
4361                         base_provider = NoBaseMembers.Instance;
4362                 }
4363
4364                 #region Properties
4365
4366                 public IBaseMembersProvider BaseMembersProvider {
4367                         get {
4368                                 return base_provider;
4369                         }
4370                         set {
4371                                 base_provider = value;
4372                         }
4373                 }
4374
4375                 public bool BestCandidateIsDynamic { get; set; }
4376
4377                 //
4378                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
4379                 //
4380                 public MethodGroupExpr BestCandidateNewMethodGroup {
4381                         get {
4382                                 return best_candidate_extension_group;
4383                         }
4384                 }
4385
4386                 //
4387                 // Return type can be different between best candidate and closest override
4388                 //
4389                 public TypeSpec BestCandidateReturnType {
4390                         get {
4391                                 return best_candidate_return_type;
4392                         }
4393                 }
4394
4395                 public IErrorHandler CustomErrors {
4396                         get {
4397                                 return custom_errors;
4398                         }
4399                         set {
4400                                 custom_errors = value;
4401                         }
4402                 }
4403
4404                 TypeSpec DelegateType {
4405                         get {
4406                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
4407                                         throw new InternalErrorException ("Not running in delegate mode", loc);
4408
4409                                 return members [0].DeclaringType;
4410                         }
4411                 }
4412
4413                 public IInstanceQualifier InstanceQualifier {
4414                         get {
4415                                 return instance_qualifier;
4416                         }
4417                         set {
4418                                 instance_qualifier = value;
4419                         }
4420                 }
4421
4422                 bool IsProbingOnly {
4423                         get {
4424                                 return (restrictions & Restrictions.ProbingOnly) != 0;
4425                         }
4426                 }
4427
4428                 bool IsDelegateInvoke {
4429                         get {
4430                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
4431                         }
4432                 }
4433
4434                 #endregion
4435
4436                 //
4437                 //  7.4.3.3  Better conversion from expression
4438                 //  Returns :   1    if a->p is better,
4439                 //              2    if a->q is better,
4440                 //              0 if neither is better
4441                 //
4442                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
4443                 {
4444                         TypeSpec argument_type = a.Type;
4445
4446                         //
4447                         // Exactly matching Expression phase
4448                         //
4449
4450                         //
4451                         // If argument is an anonymous function
4452                         //
4453                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
4454                                 //
4455                                 // p and q are delegate types or expression tree types
4456                                 //
4457                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
4458                                         if (q.MemberDefinition != p.MemberDefinition) {
4459                                                 return 0;
4460                                         }
4461
4462                                         //
4463                                         // Uwrap delegate from Expression<T>
4464                                         //
4465                                         q = TypeManager.GetTypeArguments (q) [0];
4466                                         p = TypeManager.GetTypeArguments (p) [0];
4467                                 }
4468
4469                                 var p_m = Delegate.GetInvokeMethod (p);
4470                                 var q_m = Delegate.GetInvokeMethod (q);
4471
4472                                 //
4473                                 // With identical parameter lists
4474                                 //
4475                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
4476                                         return 0;
4477
4478                                 p = p_m.ReturnType;
4479                                 var orig_q = q;
4480                                 q = q_m.ReturnType;
4481
4482                                 //
4483                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4484                                 //
4485                                 if (p.Kind == MemberKind.Void) {
4486                                         return q.Kind != MemberKind.Void ? 2 : 0;
4487                                 }
4488
4489                                 //
4490                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4491                                 //
4492                                 if (q.Kind == MemberKind.Void) {
4493                                         return p.Kind != MemberKind.Void ? 1 : 0;
4494                                 }
4495
4496                                 var am = (AnonymousMethodExpression)a.Expr;
4497
4498                                 //
4499                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
4500                                 // better conversion is performed between underlying types Y1 and Y2
4501                                 //
4502                                 if (p.IsGenericTask || q.IsGenericTask) {
4503                                         if (am.Block.IsAsync && p.IsGenericTask && q.IsGenericTask) {
4504                                                 q = q.TypeArguments [0];
4505                                                 p = p.TypeArguments [0];
4506                                         }
4507                                 }
4508
4509                                 if (q != p) {
4510                                         //
4511                                         // An inferred return type X exists for E in the context of the parameter list, and
4512                                         // an identity conversion exists from X to the return type of D
4513                                         //
4514                                         var inferred_type = am.InferReturnType (ec, null, orig_q);
4515                                         if (inferred_type != null) {
4516                                                 if (inferred_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4517                                                         inferred_type = ec.BuiltinTypes.Object;
4518
4519                                                 if (inferred_type == p)
4520                                                         return 1;
4521
4522                                                 if (inferred_type == q)
4523                                                         return 2;
4524                                         }
4525                                 }
4526                         }
4527
4528                         if (argument_type == p)
4529                                 return 1;
4530
4531                         if (argument_type == q)
4532                                 return 2;
4533
4534                         return IsBetterConversionTarget (ec, p, q);
4535                 }
4536
4537                 static int IsBetterConversionTarget (ResolveContext rc, TypeSpec p, TypeSpec q)
4538                 {
4539                         if ((p.Kind == MemberKind.Delegate || p.IsExpressionTreeType) && (q.Kind == MemberKind.Delegate || q.IsExpressionTreeType)) {
4540
4541                                 if (p.Kind != MemberKind.Delegate) {
4542                                         p = TypeManager.GetTypeArguments (p) [0];
4543                                 }
4544
4545                                 if (q.Kind != MemberKind.Delegate) {
4546                                         q = TypeManager.GetTypeArguments (q) [0];
4547                                 }
4548
4549                                 var p_m = Delegate.GetInvokeMethod (p);
4550                                 var q_m = Delegate.GetInvokeMethod (q);
4551
4552                                 p = p_m.ReturnType;
4553                                 q = q_m.ReturnType;
4554
4555                                 //
4556                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4557                                 //
4558                                 if (p.Kind == MemberKind.Void) {
4559                                         return q.Kind != MemberKind.Void ? 2 : 0;
4560                                 }
4561
4562                                 //
4563                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4564                                 //
4565                                 if (q.Kind == MemberKind.Void) {
4566                                         return p.Kind != MemberKind.Void ? 1 : 0;
4567                                 }
4568
4569                                 return IsBetterConversionTarget (rc, p, q);
4570                         }
4571
4572                         if (p.IsGenericTask && q.IsGenericTask) {
4573                                 q = q.TypeArguments [0];
4574                                 p = p.TypeArguments [0];
4575                                 return IsBetterConversionTarget (rc, p, q);
4576                         }
4577
4578                         var p_orig = p;
4579                         if (p.IsNullableType) {
4580                                 p = Nullable.NullableInfo.GetUnderlyingType (p);
4581                                 if (!BuiltinTypeSpec.IsPrimitiveTypeOrDecimal (p))
4582                                         return BetterTypeConversionImplicitConversion (rc, p_orig, q);
4583
4584                                 //
4585                                 // Spec expects implicit conversion check between p and q, q and p
4586                                 // to be done before nullable unwrapping but that's expensive operation.
4587                                 //
4588                                 // Extra manual tweak is needed because BetterTypeConversion works on
4589                                 // unwrapped types
4590                                 //
4591                                 if (p == q)
4592                                         return 2;
4593                         }
4594
4595                         var q_orig = q;
4596                         if (q.IsNullableType) {
4597                                 q = Nullable.NullableInfo.GetUnderlyingType (q);
4598                                 if (!BuiltinTypeSpec.IsPrimitiveTypeOrDecimal (q))
4599                                         return BetterTypeConversionImplicitConversion (rc, p_orig, q_orig);
4600
4601                                 if (q == p)
4602                                         return 1;
4603                         }
4604
4605                         return BetterTypeConversion (rc, p, q);
4606                 }
4607
4608                 //
4609                 // 7.4.3.4  Better conversion from type
4610                 //
4611                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
4612                 {
4613                         if (p == null || q == null)
4614                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
4615
4616                         switch (p.BuiltinType) {
4617                         case BuiltinTypeSpec.Type.Int:
4618                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4619                                         return 1;
4620                                 break;
4621                         case BuiltinTypeSpec.Type.Long:
4622                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4623                                         return 1;
4624                                 break;
4625                         case BuiltinTypeSpec.Type.SByte:
4626                                 switch (q.BuiltinType) {
4627                                 case BuiltinTypeSpec.Type.Byte:
4628                                 case BuiltinTypeSpec.Type.UShort:
4629                                 case BuiltinTypeSpec.Type.UInt:
4630                                 case BuiltinTypeSpec.Type.ULong:
4631                                         return 1;
4632                                 }
4633                                 break;
4634                         case BuiltinTypeSpec.Type.Short:
4635                                 switch (q.BuiltinType) {
4636                                 case BuiltinTypeSpec.Type.UShort:
4637                                 case BuiltinTypeSpec.Type.UInt:
4638                                 case BuiltinTypeSpec.Type.ULong:
4639                                         return 1;
4640                                 }
4641                                 break;
4642                         case BuiltinTypeSpec.Type.Dynamic:
4643                                 // LAMESPEC: Dynamic conversions is not considered
4644                                 p = ec.Module.Compiler.BuiltinTypes.Object;
4645                                 break;
4646                         }
4647
4648                         switch (q.BuiltinType) {
4649                         case BuiltinTypeSpec.Type.Int:
4650                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4651                                         return 2;
4652                                 break;
4653                         case BuiltinTypeSpec.Type.Long:
4654                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4655                                         return 2;
4656                                 break;
4657                         case BuiltinTypeSpec.Type.SByte:
4658                                 switch (p.BuiltinType) {
4659                                 case BuiltinTypeSpec.Type.Byte:
4660                                 case BuiltinTypeSpec.Type.UShort:
4661                                 case BuiltinTypeSpec.Type.UInt:
4662                                 case BuiltinTypeSpec.Type.ULong:
4663                                         return 2;
4664                                 }
4665                                 break;
4666                         case BuiltinTypeSpec.Type.Short:
4667                                 switch (p.BuiltinType) {
4668                                 case BuiltinTypeSpec.Type.UShort:
4669                                 case BuiltinTypeSpec.Type.UInt:
4670                                 case BuiltinTypeSpec.Type.ULong:
4671                                         return 2;
4672                                 }
4673                                 break;
4674                         case BuiltinTypeSpec.Type.Dynamic:
4675                                 // LAMESPEC: Dynamic conversions is not considered
4676                                 q = ec.Module.Compiler.BuiltinTypes.Object;
4677                                 break;
4678                         }
4679
4680                         return BetterTypeConversionImplicitConversion (ec, p, q);
4681                 }
4682
4683                 static int BetterTypeConversionImplicitConversion (ResolveContext rc, TypeSpec p, TypeSpec q)
4684                 {
4685                         // TODO: this is expensive
4686                         Expression p_tmp = new EmptyExpression (p);
4687                         Expression q_tmp = new EmptyExpression (q);
4688
4689                         bool p_to_q = Convert.ImplicitConversionExists (rc, p_tmp, q);
4690                         bool q_to_p = Convert.ImplicitConversionExists (rc, q_tmp, p);
4691
4692                         if (p_to_q && !q_to_p)
4693                                 return 1;
4694
4695                         if (q_to_p && !p_to_q)
4696                                 return 2;
4697
4698                         return 0;
4699                 }
4700
4701                 /// <summary>
4702                 ///   Determines "Better function" between candidate
4703                 ///   and the current best match
4704                 /// </summary>
4705                 /// <remarks>
4706                 ///    Returns a boolean indicating :
4707                 ///     false if candidate ain't better
4708                 ///     true  if candidate is better than the current best match
4709                 /// </remarks>
4710                 bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
4711                         MemberSpec best, AParametersCollection bparam, bool best_params)
4712                 {
4713                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
4714                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
4715
4716                         int candidate_better_count = 0;
4717                         int best_better_count = 0;
4718
4719                         bool are_equivalent = true;
4720                         int args_count = args == null ? 0 : args.Count;
4721                         int j = 0;
4722                         Argument a = null;
4723                         TypeSpec ct, bt;
4724                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
4725                                 a = args[j];
4726
4727                                 // Default arguments are ignored for better decision
4728                                 if (a.IsDefaultArgument)
4729                                         break;
4730
4731                                 //
4732                                 // When comparing named argument the parameter type index has to be looked up
4733                                 // in original parameter set (override version for virtual members)
4734                                 //
4735                                 NamedArgument na = a as NamedArgument;
4736                                 if (na != null) {
4737                                         int idx = cparam.GetParameterIndexByName (na.Name);
4738                                         ct = candidate_pd.Types[idx];
4739                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4740                                                 ct = TypeManager.GetElementType (ct);
4741
4742                                         idx = bparam.GetParameterIndexByName (na.Name);
4743                                         bt = best_pd.Types[idx];
4744                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4745                                                 bt = TypeManager.GetElementType (bt);
4746                                 } else {
4747                                         ct = candidate_pd.Types[c_idx];
4748                                         bt = best_pd.Types[b_idx];
4749
4750                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
4751                                                 ct = TypeManager.GetElementType (ct);
4752                                                 --c_idx;
4753                                         }
4754
4755                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
4756                                                 bt = TypeManager.GetElementType (bt);
4757                                                 --b_idx;
4758                                         }
4759                                 }
4760
4761                                 if (TypeSpecComparer.IsEqual (ct, bt))
4762                                         continue;
4763
4764                                 are_equivalent = false;
4765                                 int result = BetterExpressionConversion (ec, a, ct, bt);
4766
4767                                 // for each argument, the conversion to 'ct' should be no worse than
4768                                 // the conversion to 'bt'.
4769                                 if (result == 2) {
4770                                         //
4771                                         // No optional parameters tie breaking rules for delegates overload resolution
4772                                         //
4773                                         if ((restrictions & Restrictions.CovariantDelegate) != 0)
4774                                                 return false;
4775
4776                                         ++best_better_count;
4777                                         continue;
4778                                 }
4779
4780                                 // for at least one argument, the conversion to 'ct' should be better than
4781                                 // the conversion to 'bt'.
4782                                 if (result != 0)
4783                                         ++candidate_better_count;
4784                         }
4785
4786                         if (candidate_better_count != 0 && best_better_count == 0)
4787                                 return true;
4788
4789                         if (best_better_count > 0 && candidate_better_count == 0)
4790                                 return false;
4791
4792                         //
4793                         // LAMESPEC: Tie-breaking rules for not equivalent parameter types
4794                         //
4795                         if (!are_equivalent) {
4796                                 while (j < args_count && !args [j++].IsDefaultArgument) ;
4797
4798                                 //
4799                                 // A candidate with no default parameters is still better when there
4800                                 // is no better expression conversion and does not have more parameters
4801                                 //
4802                                 if (candidate_pd.Count < best_pd.Count) {
4803                                         if (candidate_params)
4804                                                 return false;
4805
4806                                         if (!candidate_pd.FixedParameters [j - 1].HasDefaultValue)
4807                                                 return true;
4808
4809                                         if (best_pd.FixedParameters [j].HasDefaultValue)
4810                                                 return true;
4811
4812                                 } else if (candidate_pd.Count == best_pd.Count) {
4813                                         if (candidate_params)
4814                                                 return false;
4815
4816                                         if (!candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.FixedParameters [j - 1].HasDefaultValue)
4817                                                 return true;
4818
4819                                         if (candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.HasParams)
4820                                                 return true;
4821                                 }
4822
4823                                 return false;
4824                         }
4825
4826                         //
4827                         // If candidate is applicable in its normal form and best has a params array and is applicable
4828                         // only in its expanded form, then candidate is better
4829                         //
4830                         if (candidate_params != best_params)
4831                                 return !candidate_params;
4832
4833                         //
4834                         // We have not reached end of parameters list due to params or used default parameters
4835                         //
4836                         bool defaults_ambiguity = false;
4837                         while (j < candidate_pd.Count && j < best_pd.Count) {
4838                                 var cand_param = candidate_pd.FixedParameters [j];
4839                                 var best_param = best_pd.FixedParameters [j];
4840
4841                                 if (cand_param.HasDefaultValue != best_param.HasDefaultValue && (!candidate_pd.HasParams || !best_pd.HasParams))
4842                                         return cand_param.HasDefaultValue;
4843
4844                                 defaults_ambiguity = true;
4845                                 if (candidate_pd.Count == best_pd.Count) {
4846                                         //
4847                                         // LAMESPEC:
4848                                         //
4849                                         // void Foo (int i = 0) is better than void Foo (params int[]) for Foo ()
4850                                         // void Foo (string[] s, string value = null) is better than Foo (string s, params string[]) for Foo (null) or Foo ()
4851                                         //
4852                                         if (cand_param.HasDefaultValue) {
4853                                                 ++j;
4854                                                 continue;
4855                                         }
4856
4857                                         break;
4858                                 }
4859
4860                                 //
4861                                 // Neither is better when not all arguments are provided
4862                                 //
4863                                 // void Foo (string s, int i = 0) <-> Foo (string s, int i = 0, int i2 = 0)
4864                                 // void Foo (string s, int i = 0) <-> Foo (string s, byte i = 0)
4865                                 // void Foo (string s, params int[]) <-> Foo (string s, params byte[])
4866                                 //
4867                                 ++j;
4868                         }
4869
4870                         if (candidate_pd.Count != best_pd.Count) {
4871                                 if (defaults_ambiguity && best_pd.Count - 1 == j)
4872                                         return best_pd.HasParams;
4873
4874                                 return candidate_pd.Count < best_pd.Count;
4875                         }
4876
4877                         //
4878                         // One is a non-generic method and second is a generic method, then non-generic is better
4879                         //
4880                         if (best.IsGeneric != candidate.IsGeneric)
4881                                 return best.IsGeneric;
4882
4883                         //
4884                         // Both methods have the same number of parameters, and the parameters have equal types
4885                         // Pick the "more specific" signature using rules over original (non-inflated) types
4886                         //
4887                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
4888                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
4889
4890                         bool specific_at_least_once = false;
4891                         for (j = 0; j < args_count; ++j) {
4892                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
4893                                 if (na != null) {
4894                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
4895                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
4896                                 } else {
4897                                         ct = candidate_def_pd.Types[j];
4898                                         bt = best_def_pd.Types[j];
4899                                 }
4900
4901                                 if (ct == bt)
4902                                         continue;
4903                                 TypeSpec specific = MoreSpecific (ct, bt);
4904                                 if (specific == bt)
4905                                         return false;
4906                                 if (specific == ct)
4907                                         specific_at_least_once = true;
4908                         }
4909
4910                         if (specific_at_least_once)
4911                                 return true;
4912
4913                         return false;
4914                 }
4915
4916                 static bool CheckInflatedArguments (MethodSpec ms)
4917                 {
4918                         if (!TypeParameterSpec.HasAnyTypeParameterTypeConstrained (ms.GenericDefinition))
4919                                 return true;
4920
4921                         // Setup constraint checker for probing only
4922                         ConstraintChecker cc = new ConstraintChecker (null);
4923
4924                         var mp = ms.Parameters.Types;
4925                         for (int i = 0; i < mp.Length; ++i) {
4926                                 var type = mp[i] as InflatedTypeSpec;
4927                                 if (type == null)
4928                                         continue;
4929
4930                                 var targs = type.TypeArguments;
4931                                 if (targs.Length == 0)
4932                                         continue;
4933
4934                                 // TODO: Checking inflated MVAR arguments should be enough
4935                                 if (!cc.CheckAll (type.GetDefinition (), targs, type.Constraints, Location.Null))
4936                                         return false;
4937                         }
4938
4939                         return true;
4940                 }
4941
4942                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4943                 {
4944                         rc.Report.Error (1729, loc,
4945                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4946                                 type.GetSignatureForError (), argCount.ToString ());
4947                 }
4948
4949                 //
4950                 // Determines if the candidate method is applicable to the given set of arguments
4951                 // There could be two different set of parameters for same candidate where one
4952                 // is the closest override for default values and named arguments checks and second
4953                 // one being the virtual base for the parameter types and modifiers.
4954                 //
4955                 // A return value rates candidate method compatibility,
4956                 // -1 = fatal error
4957                 // 0 = the best, int.MaxValue = the worst
4958                 //
4959                 int IsApplicable (ResolveContext ec, ref Arguments arguments, int arg_count, ref MemberSpec candidate, IParametersMember pm, ref bool params_expanded_form, ref bool dynamicArgument, ref TypeSpec returnType, bool errorMode)
4960                 {
4961                         //
4962                         // Each step has allocated 10 values, it can overflow for
4963                         // more than 10 arguments but that's ok as it's used for
4964                         // better error reporting only
4965                         //
4966                         const int ArgumentCountMismatch         = 1000000000;
4967                         const int NamedArgumentsMismatch        = 100000000;
4968                         const int DefaultArgumentMismatch       = 10000000;
4969                         const int UnexpectedTypeArguments       = 1000000;
4970                         const int TypeArgumentsMismatch         = 100000;
4971                         const int InflatedTypesMismatch         = 10000;
4972
4973                         // Parameters of most-derived type used mainly for named and optional parameters
4974                         var pd = pm.Parameters;
4975
4976                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4977                         // params modifier instead of most-derived type
4978                         var cpd = ((IParametersMember) candidate).Parameters;
4979                         int param_count = pd.Count;
4980                         int optional_count = 0;
4981                         int score;
4982                         Arguments orig_args = arguments;
4983
4984                         if (arg_count != param_count) {
4985                                 //
4986                                 // No arguments expansion when doing exact match for delegates
4987                                 //
4988                                 if ((restrictions & Restrictions.CovariantDelegate) == 0) {
4989                                         for (int i = 0; i < pd.Count; ++i) {
4990                                                 if (pd.FixedParameters[i].HasDefaultValue) {
4991                                                         optional_count = pd.Count - i;
4992                                                         break;
4993                                                 }
4994                                         }
4995                                 }
4996
4997                                 if (optional_count != 0) {
4998                                         // Readjust expected number when params used
4999                                         if (cpd.HasParams) {
5000                                                 optional_count--;
5001                                                 if (arg_count < param_count)
5002                                                         param_count--;
5003                                         } else if (arg_count > param_count) {
5004                                                 int args_gap = System.Math.Abs (arg_count - param_count);
5005                                                 return ArgumentCountMismatch + args_gap;
5006                                         } else if (arg_count < param_count - optional_count) {
5007                                                 int args_gap = System.Math.Abs (param_count - optional_count - arg_count);
5008                                                 return ArgumentCountMismatch + args_gap;
5009                                         }
5010                                 } else if (arg_count != param_count) {
5011                                         int args_gap = System.Math.Abs (arg_count - param_count);
5012                                         if (!cpd.HasParams)
5013                                                 return ArgumentCountMismatch + args_gap;
5014                                         if (arg_count < param_count - 1)
5015                                                 return ArgumentCountMismatch + args_gap;
5016                                 }
5017
5018                                 // Resize to fit optional arguments
5019                                 if (optional_count != 0) {
5020                                         if (arguments == null) {
5021                                                 arguments = new Arguments (optional_count);
5022                                         } else {
5023                                                 // Have to create a new container, so the next run can do same
5024                                                 var resized = new Arguments (param_count);
5025                                                 resized.AddRange (arguments);
5026                                                 arguments = resized;
5027                                         }
5028
5029                                         for (int i = arg_count; i < param_count; ++i)
5030                                                 arguments.Add (null);
5031                                 }
5032                         }
5033
5034                         if (arg_count > 0) {
5035                                 //
5036                                 // Shuffle named arguments to the right positions if there are any
5037                                 //
5038                                 if (arguments[arg_count - 1] is NamedArgument) {
5039                                         arg_count = arguments.Count;
5040
5041                                         for (int i = 0; i < arg_count; ++i) {
5042                                                 bool arg_moved = false;
5043                                                 while (true) {
5044                                                         NamedArgument na = arguments[i] as NamedArgument;
5045                                                         if (na == null)
5046                                                                 break;
5047
5048                                                         int index = pd.GetParameterIndexByName (na.Name);
5049
5050                                                         // Named parameter not found
5051                                                         if (index < 0)
5052                                                                 return NamedArgumentsMismatch - i;
5053
5054                                                         // already reordered
5055                                                         if (index == i)
5056                                                                 break;
5057
5058                                                         Argument temp;
5059                                                         if (index >= param_count) {
5060                                                                 // When using parameters which should not be available to the user
5061                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
5062                                                                         break;
5063
5064                                                                 arguments.Add (null);
5065                                                                 ++arg_count;
5066                                                                 temp = null;
5067                                                         } else {
5068                                                                 if (index == arg_count)
5069                                                                         return NamedArgumentsMismatch - i - 1;
5070
5071                                                                 temp = arguments [index];
5072
5073                                                                 // The slot has been taken by positional argument
5074                                                                 if (temp != null && !(temp is NamedArgument))
5075                                                                         return NamedArgumentsMismatch - i - 1;
5076                                                         }
5077
5078                                                         if (!arg_moved) {
5079                                                                 arguments = arguments.MarkOrderedArgument (na);
5080                                                                 arg_moved = true;
5081                                                         }
5082
5083                                                         if (arguments == orig_args) {
5084                                                                 arguments = new Arguments (orig_args.Count);
5085                                                                 arguments.AddRange (orig_args);
5086                                                         }
5087
5088                                                         arguments[index] = arguments[i];
5089                                                         arguments[i] = temp;
5090
5091                                                         if (temp == null)
5092                                                                 break;
5093                                                 }
5094                                         }
5095                                 } else {
5096                                         arg_count = arguments.Count;
5097                                 }
5098                         } else if (arguments != null) {
5099                                 arg_count = arguments.Count;
5100                         }
5101
5102                         //
5103                         // Don't do any expensive checks when the candidate cannot succeed
5104                         //
5105                         if (arg_count != param_count && !cpd.HasParams)
5106                                 return DefaultArgumentMismatch - System.Math.Abs (param_count - arg_count);
5107
5108                         var dep = candidate.GetMissingDependencies ();
5109                         if (dep != null) {
5110                                 ImportedTypeDefinition.Error_MissingDependency (ec, dep, loc);
5111                                 return -1;
5112                         }
5113
5114                         //
5115                         // 1. Handle generic method using type arguments when specified or type inference
5116                         //
5117                         TypeSpec[] ptypes;
5118                         var ms = candidate as MethodSpec;
5119                         if (ms != null && ms.IsGeneric) {
5120                                 if (type_arguments != null) {
5121                                         var g_args_count = ms.Arity;
5122                                         if (g_args_count != type_arguments.Count)
5123                                                 return TypeArgumentsMismatch - System.Math.Abs (type_arguments.Count - g_args_count);
5124
5125                                         if (type_arguments.Arguments != null)
5126                                                 ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
5127                                 } else {
5128                                         //
5129                                         // Deploy custom error reporting for infered anonymous expression or lambda methods. When
5130                                         // probing lambda methods keep all errors reported in separate set and once we are done and no best
5131                                         // candidate was found use the set to report more details about what was wrong with lambda body.
5132                                         // The general idea is to distinguish between code errors and errors caused by
5133                                         // trial-and-error type inference
5134                                         //
5135                                         if (lambda_conv_msgs == null) {
5136                                                 for (int i = 0; i < arg_count; i++) {
5137                                                         Argument a = arguments[i];
5138                                                         if (a == null)
5139                                                                 continue;
5140
5141                                                         var am = a.Expr as AnonymousMethodExpression;
5142                                                         if (am != null) {
5143                                                                 if (lambda_conv_msgs == null)
5144                                                                         lambda_conv_msgs = new SessionReportPrinter ();
5145
5146                                                                 am.TypeInferenceReportPrinter = lambda_conv_msgs;
5147                                                         }
5148                                                 }
5149                                         }
5150
5151                                         var ti = new TypeInference (arguments);
5152                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
5153
5154                                         if (i_args == null)
5155                                                 return TypeArgumentsMismatch - ti.InferenceScore;
5156
5157                                         //
5158                                         // Clear any error messages when the result was success
5159                                         //
5160                                         if (lambda_conv_msgs != null)
5161                                                 lambda_conv_msgs.ClearSession ();
5162
5163                                         if (i_args.Length != 0) {
5164                                                 if (!errorMode) {
5165                                                         for (int i = 0; i < i_args.Length; ++i) {
5166                                                                 var ta = i_args [i];
5167                                                                 if (!ta.IsAccessible (ec))
5168                                                                         return TypeArgumentsMismatch - i;
5169                                                         }
5170                                                 }
5171
5172                                                 ms = ms.MakeGenericMethod (ec, i_args);
5173                                         }
5174                                 }
5175
5176                                 //
5177                                 // Type arguments constraints have to match for the method to be applicable
5178                                 //
5179                                 if (!CheckInflatedArguments (ms)) {
5180                                         candidate = ms;
5181                                         return InflatedTypesMismatch;
5182                                 }
5183
5184                                 //
5185                                 // We have a generic return type and at same time the method is override which
5186                                 // means we have to also inflate override return type in case the candidate is
5187                                 // best candidate and override return type is different to base return type.
5188                                 //
5189                                 // virtual Foo<T, object> with override Foo<T, dynamic>
5190                                 //
5191                                 if (candidate != pm) {
5192                                         MethodSpec override_ms = (MethodSpec) pm;
5193                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
5194                                         returnType = inflator.Inflate (returnType);
5195                                 } else {
5196                                         returnType = ms.ReturnType;
5197                                 }
5198
5199                                 candidate = ms;
5200                                 pd = ms.Parameters;
5201                                 ptypes = pd.Types;
5202                         } else {
5203                                 if (type_arguments != null)
5204                                         return UnexpectedTypeArguments;
5205
5206                                 ptypes = cpd.Types;
5207                         }
5208
5209                         //
5210                         // 2. Each argument has to be implicitly convertible to method parameter
5211                         //
5212                         Parameter.Modifier p_mod = 0;
5213                         TypeSpec pt = null;
5214
5215                         for (int i = 0; i < arg_count; i++) {
5216                                 Argument a = arguments[i];
5217                                 if (a == null) {
5218                                         var fp = pd.FixedParameters[i];
5219                                         if (!fp.HasDefaultValue) {
5220                                                 arguments = orig_args;
5221                                                 return arg_count * 2 + 2;
5222                                         }
5223
5224                                         //
5225                                         // Get the default value expression, we can use the same expression
5226                                         // if the type matches
5227                                         //
5228                                         Expression e = fp.DefaultValue;
5229                                         if (e != null) {
5230                                                 e = ResolveDefaultValueArgument (ec, ptypes[i], e, loc);
5231                                                 if (e == null) {
5232                                                         // Restore for possible error reporting
5233                                                         for (int ii = i; ii < arg_count; ++ii)
5234                                                                 arguments.RemoveAt (i);
5235
5236                                                         return (arg_count - i) * 2 + 1;
5237                                                 }
5238                                         }
5239
5240                                         if ((fp.ModFlags & Parameter.Modifier.CallerMask) != 0) {
5241                                                 //
5242                                                 // LAMESPEC: Attributes can be mixed together with build-in priority
5243                                                 //
5244                                                 if ((fp.ModFlags & Parameter.Modifier.CallerLineNumber) != 0) {
5245                                                         e = new IntLiteral (ec.BuiltinTypes, loc.Row, loc);
5246                                                 } else if ((fp.ModFlags & Parameter.Modifier.CallerFilePath) != 0) {
5247                                                         e = new StringLiteral (ec.BuiltinTypes, loc.SourceFile.GetFullPathName (ec.Module.Compiler.Settings.PathMap), loc);
5248                                                 } else if (ec.MemberContext.CurrentMemberDefinition != null) {
5249                                                         e = new StringLiteral (ec.BuiltinTypes, ec.MemberContext.CurrentMemberDefinition.GetCallerMemberName (), loc);
5250                                                 }
5251                                         }
5252
5253                                         arguments[i] = new Argument (e, Argument.AType.Default);
5254                                         continue;
5255                                 }
5256
5257                                 if (p_mod != Parameter.Modifier.PARAMS) {
5258                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
5259                                         pt = ptypes [i];
5260                                 } else if (!params_expanded_form) {
5261                                         params_expanded_form = true;
5262                                         pt = ((ElementTypeSpec) pt).Element;
5263                                         i -= 2;
5264                                         continue;
5265                                 }
5266
5267                                 score = 1;
5268                                 if (!params_expanded_form) {
5269                                         if (a.IsExtensionType) {
5270                                                 if (ExtensionMethodGroupExpr.IsExtensionTypeCompatible (a.Type, pt)) {
5271                                                         score = 0;
5272                                                         continue;
5273                                                 }
5274                                         } else {
5275                                                 score = IsArgumentCompatible (ec, a, p_mod, pt);
5276
5277                                                 if (score < 0)
5278                                                         dynamicArgument = true;
5279                                         }
5280                                 }
5281
5282                                 //
5283                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
5284                                 //
5285                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
5286                                         if (!params_expanded_form) {
5287                                                 pt = ((ElementTypeSpec) pt).Element;
5288                                         }
5289
5290                                         if (score > 0)
5291                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
5292
5293                                         if (score < 0) {
5294                                                 params_expanded_form = true;
5295                                                 dynamicArgument = true;
5296                                         } else if (score == 0 || arg_count > pd.Count) {
5297                                                 params_expanded_form = true;
5298                                         }
5299                                 }
5300
5301                                 if (score > 0) {
5302                                         if (params_expanded_form)
5303                                                 ++score;
5304                                         return (arg_count - i) * 2 + score;
5305                                 }
5306                         }
5307
5308                         //
5309                         // Restore original arguments for dynamic binder to keep the intention of original source code
5310                         //
5311                         if (dynamicArgument)
5312                                 arguments = orig_args;
5313
5314                         return 0;
5315                 }
5316
5317                 public static Expression ResolveDefaultValueArgument (ResolveContext ec, TypeSpec ptype, Expression e, Location loc)
5318                 {
5319                         if (e is Constant && e.Type == ptype)
5320                                 return e;
5321
5322                         //
5323                         // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
5324                         //
5325                         if (e == EmptyExpression.MissingValue && (ptype.BuiltinType == BuiltinTypeSpec.Type.Object || ptype.BuiltinType == BuiltinTypeSpec.Type.Dynamic)) {
5326                                 e = new MemberAccess (new MemberAccess (new MemberAccess (
5327                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
5328                         } else if (e is Constant) {
5329                                 //
5330                                 // Handles int to int? conversions, DefaultParameterValue check
5331                                 //
5332                                 e = Convert.ImplicitConversionStandard (ec, e, ptype, loc);
5333                                 if (e == null)
5334                                         return null;
5335                         } else {
5336                                 e = new DefaultValueExpression (new TypeExpression (ptype, loc), loc);
5337                         }
5338
5339                         return e.Resolve (ec);
5340                 }
5341
5342                 //
5343                 // Tests argument compatibility with the parameter
5344                 // The possible return values are
5345                 // 0 - success
5346                 // 1 - modifier mismatch
5347                 // 2 - type mismatch
5348                 // -1 - dynamic binding required
5349                 //
5350                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
5351                 {
5352                         //
5353                         // Types have to be identical when ref or out modifer
5354                         // is used and argument is not of dynamic type
5355                         //
5356                         if (((argument.Modifier | param_mod) & Parameter.Modifier.RefOutMask) != 0) {
5357                                 var arg_type = argument.Type;
5358
5359                                 if ((argument.Modifier & Parameter.Modifier.RefOutMask) != (param_mod & Parameter.Modifier.RefOutMask)) {
5360                                         //
5361                                         // Using dynamic for ref/out parameter can still succeed at runtime
5362                                         //
5363                                         if (arg_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
5364                                                 return -1;
5365
5366                                         return 1;
5367                                 }
5368
5369                                 if (arg_type != parameter) {
5370                                         if (arg_type == InternalType.VarOutType)
5371                                                 return 0;
5372
5373                                         //
5374                                         // Do full equality check after quick path
5375                                         //
5376                                         if (!TypeSpecComparer.IsEqual (arg_type, parameter)) {
5377                                                 //
5378                                                 // Using dynamic for ref/out parameter can still succeed at runtime
5379                                                 //
5380                                                 if (arg_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
5381                                                         return -1;
5382
5383                                                 return 2;
5384                                         }
5385                                 }
5386
5387                         } else {
5388                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
5389                                         return -1;
5390
5391                                 //
5392                                 // Use implicit conversion in all modes to return same candidates when the expression
5393                                 // is used as argument or delegate conversion
5394                                 //
5395                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
5396                                         return parameter.IsDelegate && argument.Expr is AnonymousMethodExpression ? 2 : 3;
5397                                 }
5398                         }
5399
5400                         return 0;
5401                 }
5402
5403                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
5404                 {
5405                         if (p.IsGenericParameter != q.IsGenericParameter)
5406                                 return p.IsGenericParameter ? q : p;
5407
5408                         var ac_p = p as ArrayContainer;
5409                         if (ac_p != null) {
5410                                 var ac_q = q as ArrayContainer;
5411                                 if (ac_q == null)
5412                                         return null;
5413
5414                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
5415                                 if (specific == ac_p.Element)
5416                                         return p;
5417                                 if (specific == ac_q.Element)
5418                                         return q;
5419
5420                                 return null;
5421                         }
5422
5423                         if (p.IsGeneric && q.IsGeneric) {
5424                                 var pargs = p.TypeArguments;
5425                                 var qargs = q.TypeArguments;
5426
5427                                 bool p_specific_at_least_once = false;
5428                                 bool q_specific_at_least_once = false;
5429
5430                                 for (int i = 0; i < pargs.Length; i++) {
5431                                         TypeSpec specific = MoreSpecific (pargs [i], qargs [i]);
5432                                         if (specific == pargs [i])
5433                                                 p_specific_at_least_once = true;
5434                                         if (specific == qargs [i])
5435                                                 q_specific_at_least_once = true;
5436                                 }
5437
5438                                 if (p_specific_at_least_once && !q_specific_at_least_once)
5439                                         return p;
5440                                 if (!p_specific_at_least_once && q_specific_at_least_once)
5441                                         return q;
5442                         }
5443
5444                         return null;
5445                 }
5446
5447                 //
5448                 // Find the best method from candidate list
5449                 //
5450                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
5451                 {
5452                         List<AmbiguousCandidate> ambiguous_candidates = null;
5453
5454                         MemberSpec best_candidate;
5455                         Arguments best_candidate_args = null;
5456                         bool best_candidate_params = false;
5457                         bool best_candidate_dynamic = false;
5458                         int best_candidate_rate;
5459                         IParametersMember best_parameter_member = null;
5460
5461                         int args_count = args != null ? args.Count : 0;
5462
5463                         Arguments candidate_args = args;
5464                         bool error_mode = false;
5465                         MemberSpec invocable_member = null;
5466                         int applicable_candidates = 0;
5467
5468                         while (true) {
5469                                 best_candidate = null;
5470                                 best_candidate_rate = int.MaxValue;
5471
5472                                 var type_members = members;
5473                                 do {
5474                                         for (int i = 0; i < type_members.Count; ++i) {
5475                                                 var member = type_members[i];
5476
5477                                                 //
5478                                                 // Methods in a base class are not candidates if any method in a derived
5479                                                 // class is applicable
5480                                                 //
5481                                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
5482                                                         continue;
5483
5484                                                 if (!error_mode) {
5485                                                         if (!member.IsAccessible (rc))
5486                                                                 continue;
5487
5488                                                         if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
5489                                                                 continue;
5490
5491                                                         if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5492                                                                 instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
5493                                                                 continue;
5494                                                         }
5495                                                 }
5496
5497                                                 IParametersMember pm = member as IParametersMember;
5498                                                 if (pm == null) {
5499                                                         //
5500                                                         // Will use it later to report ambiguity between best method and invocable member
5501                                                         //
5502                                                         if (Invocation.IsMemberInvocable (member))
5503                                                                 invocable_member = member;
5504
5505                                                         continue;
5506                                                 }
5507
5508                                                 //
5509                                                 // Overload resolution is looking for base member but using parameter names
5510                                                 // and default values from the closest member. That means to do expensive lookup
5511                                                 // for the closest override for virtual or abstract members
5512                                                 //
5513                                                 if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
5514                                                         var override_params = base_provider.GetOverrideMemberParameters (member);
5515                                                         if (override_params != null)
5516                                                                 pm = override_params;
5517                                                 }
5518
5519                                                 //
5520                                                 // Check if the member candidate is applicable
5521                                                 //
5522                                                 bool params_expanded_form = false;
5523                                                 bool dynamic_argument = false;
5524                                                 TypeSpec rt = pm.MemberType;
5525                                                 int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt, error_mode);
5526
5527                                                 if (lambda_conv_msgs != null)
5528                                                         lambda_conv_msgs.EndSession ();
5529
5530                                                 //
5531                                                 // How does it score compare to others
5532                                                 //
5533                                                 if (candidate_rate < best_candidate_rate) {
5534
5535                                                         // Fatal error (missing dependency), cannot continue
5536                                                         if (candidate_rate < 0)
5537                                                                 return null;
5538
5539                                                         applicable_candidates = 1;
5540                                                         if ((restrictions & Restrictions.GetEnumeratorLookup) != 0 && candidate_args.Count != 0) {
5541                                                                 // Only parameterless methods are considered
5542                                                         } else {
5543                                                                 best_candidate_rate = candidate_rate;
5544                                                                 best_candidate = member;
5545                                                                 best_candidate_args = candidate_args;
5546                                                                 best_candidate_params = params_expanded_form;
5547                                                                 best_candidate_dynamic = dynamic_argument;
5548                                                                 best_parameter_member = pm;
5549                                                                 best_candidate_return_type = rt;
5550                                                         }
5551                                                 } else if (candidate_rate == 0) {
5552                                                         //
5553                                                         // The member look is done per type for most operations but sometimes
5554                                                         // it's not possible like for binary operators overload because they
5555                                                         // are unioned between 2 sides
5556                                                         //
5557                                                         if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
5558                                                                 if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
5559                                                                         continue;
5560                                                         }
5561
5562                                                         ++applicable_candidates;
5563                                                         bool is_better;
5564                                                         if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5565                                                                 //
5566                                                                 // We pack all interface members into top level type which makes the overload resolution
5567                                                                 // more complicated for interfaces. We compensate it by removing methods with same
5568                                                                 // signature when building the cache hence this path should not really be hit often
5569                                                                 //
5570                                                                 // Example:
5571                                                                 // interface IA { void Foo (int arg); }
5572                                                                 // interface IB : IA { void Foo (params int[] args); }
5573                                                                 //
5574                                                                 // IB::Foo is the best overload when calling IB.Foo (1)
5575                                                                 //
5576                                                                 is_better = true;
5577                                                                 if (ambiguous_candidates != null) {
5578                                                                         foreach (var amb_cand in ambiguous_candidates) {
5579                                                                                 if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5580                                                                                         continue;
5581                                                                                 }
5582
5583                                                                                 is_better = false;
5584                                                                                 break;
5585                                                                         }
5586
5587                                                                         if (is_better)
5588                                                                                 ambiguous_candidates = null;
5589                                                                 }
5590                                                         } else {
5591                                                                 // Is the new candidate better
5592                                                                 is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
5593                                                         }
5594
5595                                                         if (is_better) {
5596                                                                 best_candidate = member;
5597                                                                 best_candidate_args = candidate_args;
5598                                                                 best_candidate_params = params_expanded_form;
5599                                                                 best_candidate_dynamic = dynamic_argument;
5600                                                                 best_parameter_member = pm;
5601                                                                 best_candidate_return_type = rt;
5602                                                         } else {
5603                                                                 // It's not better but any other found later could be but we are not sure yet
5604                                                                 if (ambiguous_candidates == null)
5605                                                                         ambiguous_candidates = new List<AmbiguousCandidate> ();
5606
5607                                                                 ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
5608                                                         }
5609                                                 }
5610
5611                                                 // Restore expanded arguments
5612                                                 candidate_args = args;
5613                                         }
5614                                 } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType)) != null);
5615
5616                                 //
5617                                 // We've found exact match
5618                                 //
5619                                 if (best_candidate_rate == 0)
5620                                         break;
5621
5622                                 //
5623                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
5624                                 //
5625                                 if (!error_mode) {
5626                                         var emg = base_provider.LookupExtensionMethod (rc);
5627                                         if (emg != null) {
5628                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
5629                                                 if (emg != null) {
5630                                                         best_candidate_extension_group = emg;
5631                                                         return (T) (MemberSpec) emg.BestCandidate;
5632                                                 }
5633                                         }
5634                                 }
5635
5636                                 // Don't run expensive error reporting mode for probing
5637                                 if (IsProbingOnly)
5638                                         return null;
5639
5640                                 if (error_mode)
5641                                         break;
5642
5643                                 if (lambda_conv_msgs != null && !lambda_conv_msgs.IsEmpty)
5644                                         break;
5645
5646                                 lambda_conv_msgs = null;
5647                                 error_mode = true;
5648                         }
5649
5650                         //
5651                         // No best member match found, report an error
5652                         //
5653                         if (best_candidate_rate != 0 || error_mode) {
5654                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
5655                                 return null;
5656                         }
5657
5658                         if (best_candidate_dynamic) {
5659                                 if (args[0].IsExtensionType) {
5660                                         rc.Report.Error (1973, loc,
5661                                                 "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' cannot be dynamically dispatched. Consider calling the method without the extension method syntax",
5662                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
5663                                 }
5664
5665                                 //
5666                                 // Check type constraints only when explicit type arguments are used
5667                                 //
5668                                 if (applicable_candidates == 1 && best_candidate.IsGeneric && type_arguments != null) {
5669                                         MethodSpec bc = best_candidate as MethodSpec;
5670                                         if (bc != null && TypeParameterSpec.HasAnyTypeParameterConstrained (bc.GenericDefinition)) {
5671                                                 ConstraintChecker cc = new ConstraintChecker (rc);
5672                                                 cc.CheckAll (bc.GetGenericMethodDefinition (), bc.TypeArguments, bc.Constraints, loc);
5673                                         }
5674                                 }
5675
5676                                 BestCandidateIsDynamic = true;
5677                                 return null;
5678                         }
5679
5680                         //
5681                         // These flags indicates we are running delegate probing conversion. No need to
5682                         // do more expensive checks
5683                         //
5684                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
5685                                 return (T) best_candidate;
5686
5687                         if (ambiguous_candidates != null) {
5688                                 //
5689                                 // Now check that there are no ambiguities i.e the selected method
5690                                 // should be better than all the others
5691                                 //
5692                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
5693                                         var candidate = ambiguous_candidates [ix];
5694
5695                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
5696                                                 var ambiguous = candidate.Member;
5697                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
5698                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
5699                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
5700                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
5701                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
5702                                                 }
5703
5704                                                 return (T) best_candidate;
5705                                         }
5706                                 }
5707                         }
5708
5709                         if (invocable_member != null && !IsProbingOnly) {
5710                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5711                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
5712                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
5713                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
5714                         }
5715
5716                         //
5717                         // And now check if the arguments are all
5718                         // compatible, perform conversions if
5719                         // necessary etc. and return if everything is
5720                         // all right
5721                         //
5722                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
5723                                 return null;
5724
5725                         if (best_candidate == null)
5726                                 return null;
5727
5728                         //
5729                         // Don't run possibly expensive checks in probing mode
5730                         //
5731                         if (!IsProbingOnly && !rc.IsInProbingMode) {
5732                                 //
5733                                 // Check ObsoleteAttribute on the best method
5734                                 //
5735                                 best_candidate.CheckObsoleteness (rc, loc);
5736
5737                                 best_candidate.MemberDefinition.SetIsUsed ();
5738                         }
5739
5740                         args = best_candidate_args;
5741                         return (T) best_candidate;
5742                 }
5743
5744                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
5745                 {
5746                         return ResolveMember<MethodSpec> (rc, ref args);
5747                 }
5748
5749                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
5750                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
5751                 {
5752                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
5753                                 return;
5754
5755                         if (a.Type == InternalType.ErrorType)
5756                                 return;
5757
5758                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
5759                                 ec.Report.SymbolRelatedToPreviousError (method);
5760                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
5761                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have `ref' or `out' modifier",
5762                                                 TypeManager.CSharpSignature (method));
5763                                         return;
5764                                 }
5765                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
5766                                           TypeManager.CSharpSignature (method));
5767                         } else if (IsDelegateInvoke) {
5768                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
5769                                         DelegateType.GetSignatureForError ());
5770                         } else {
5771                                 ec.Report.SymbolRelatedToPreviousError (method);
5772                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
5773                                         method.GetSignatureForError ());
5774                         }
5775
5776                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
5777
5778                         string index = (idx + 1).ToString ();
5779                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
5780                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
5781                                         ec.Report.Error (1615, a.Expr.Location, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
5782                                                 index, Parameter.GetModifierSignature (a.Modifier));
5783                                 else
5784                                         ec.Report.Error (1620, a.Expr.Location, "Argument `#{0}' is missing `{1}' modifier",
5785                                                 index, Parameter.GetModifierSignature (mod));
5786                         } else {
5787                                 string p1 = a.GetSignatureForError ();
5788                                 string p2 = paramType.GetSignatureForError ();
5789
5790                                 if (p1 == p2) {
5791                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
5792                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
5793                                 }
5794
5795                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
5796                                         p1 = Parameter.GetModifierSignature (a.Modifier) + " " + p1;
5797                                         p2 = Parameter.GetModifierSignature (a.Modifier) + " " + p2;
5798                                 }
5799
5800                                 ec.Report.Error (1503, a.Expr.Location,
5801                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
5802                         }
5803                 }
5804
5805                 //
5806                 // We have failed to find exact match so we return error info about the closest match
5807                 //
5808                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
5809                 {
5810                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
5811                         int arg_count = args == null ? 0 : args.Count;
5812
5813                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
5814                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
5815                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, loc);
5816                                 return;
5817                         }
5818
5819                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
5820                                 return;
5821                         }
5822
5823
5824                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5825                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
5826                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
5827                         }
5828
5829                         //
5830                         // For candidates which match on parameters count report more details about incorrect arguments
5831                         //
5832                         if (pm != null) {
5833                                 if (pm.Parameters.Count == arg_count || params_expanded || HasUnfilledParams (best_candidate, pm, args)) {
5834                                         // Reject any inaccessible member
5835                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
5836                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5837                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
5838                                                 return;
5839                                         }
5840
5841                                         var ms = best_candidate as MethodSpec;
5842                                         if (ms != null && ms.IsGeneric) {
5843                                                 bool constr_ok = true;
5844                                                 if (ms.TypeArguments != null)
5845                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
5846
5847                                                 if (ta_count == 0 && ms.TypeArguments == null) {
5848                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
5849                                                                 return;
5850
5851                                                         if (constr_ok) {
5852                                                                 rc.Report.Error (411, loc,
5853                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
5854                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
5855                                                         }
5856
5857                                                         return;
5858                                                 }
5859                                         }
5860
5861                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
5862                                         return;
5863                                 }
5864                         }
5865
5866                         //
5867                         // We failed to find any method with correct argument count, report best candidate
5868                         //
5869                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
5870                                 return;
5871
5872                         if (best_candidate.Kind == MemberKind.Constructor) {
5873                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5874                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
5875                         } else if (IsDelegateInvoke) {
5876                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
5877                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
5878                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
5879                         } else {
5880                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
5881                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5882                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
5883                                         name, arg_count.ToString ());
5884                         }
5885                 }
5886
5887                 static bool HasUnfilledParams (MemberSpec best_candidate, IParametersMember pm, Arguments args)
5888                 {
5889                         var p = ((IParametersMember)best_candidate).Parameters;
5890                         if (!p.HasParams)
5891                                 return false;
5892
5893                         string name = null;
5894                         for (int i = p.Count - 1; i != 0; --i) {
5895                                 var fp = p.FixedParameters [i];
5896                                 if ((fp.ModFlags & Parameter.Modifier.PARAMS) == 0)
5897                                         continue;
5898
5899                                 name = fp.Name;
5900                                 break;
5901                         }
5902
5903                         if (args == null)
5904                                 return false;
5905
5906                         foreach (var arg in args) {
5907                                 var na = arg as NamedArgument;
5908                                 if (na == null)
5909                                         continue;
5910
5911                                 if (na.Name == name) {
5912                                         name = null;
5913                                         break;
5914                                 }
5915                         }
5916
5917                         if (name == null)
5918                                 return false;
5919
5920                         return args.Count + 1 == pm.Parameters.Count;
5921                 }
5922
5923                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
5924                 {
5925                         var pd = pm.Parameters;
5926                         var cpd = ((IParametersMember) member).Parameters;
5927                         var ptypes = cpd.Types;
5928
5929                         Parameter.Modifier p_mod = 0;
5930                         TypeSpec pt = null;
5931                         int a_idx = 0, a_pos = 0;
5932                         Argument a = null;
5933                         ArrayInitializer params_initializers = null;
5934                         bool has_unsafe_arg = pm.MemberType.IsPointer;
5935                         int arg_count = args == null ? 0 : args.Count;
5936
5937                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
5938                                 a = args[a_idx];
5939                                 if (a == null)
5940                                         continue;
5941
5942                                 if (p_mod != Parameter.Modifier.PARAMS) {
5943                                         p_mod = cpd.FixedParameters [a_idx].ModFlags;
5944                                         pt = ptypes[a_idx];
5945                                         has_unsafe_arg |= pt.IsPointer;
5946
5947                                         if (p_mod == Parameter.Modifier.PARAMS) {
5948                                                 if (chose_params_expanded) {
5949                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
5950                                                         pt = TypeManager.GetElementType (pt);
5951                                                 }
5952                                         }
5953                                 }
5954
5955                                 //
5956                                 // Types have to be identical when ref or out modifer is used
5957                                 //
5958                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
5959                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
5960                                                 break;
5961
5962                                         var arg_type = a.Type;
5963                                         if (arg_type == pt)
5964                                                 continue;
5965
5966                                         if (arg_type == InternalType.VarOutType) {
5967                                                 //
5968                                                 // Set underlying variable type based on parameter type
5969                                                 //
5970                                                 ((DeclarationExpression)a.Expr).Variable.Type = pt;
5971                                                 continue;
5972                                         }
5973
5974                                         if (!TypeSpecComparer.IsEqual (arg_type, pt))
5975                                                 break;
5976                                 }
5977
5978                                 NamedArgument na = a as NamedArgument;
5979                                 if (na != null) {
5980                                         int name_index = pd.GetParameterIndexByName (na.Name);
5981                                         if (name_index < 0 || name_index >= pd.Count) {
5982                                                 if (IsDelegateInvoke) {
5983                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5984                                                         ec.Report.Error (1746, na.Location,
5985                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
5986                                                                 DelegateType.GetSignatureForError (), na.Name);
5987                                                 } else {
5988                                                         ec.Report.SymbolRelatedToPreviousError (member);
5989                                                         ec.Report.Error (1739, na.Location,
5990                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
5991                                                                 TypeManager.CSharpSignature (member), na.Name);
5992                                                 }
5993                                         } else if (args[name_index] != a && args[name_index] != null) {
5994                                                 if (IsDelegateInvoke)
5995                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5996                                                 else
5997                                                         ec.Report.SymbolRelatedToPreviousError (member);
5998
5999                                                 ec.Report.Error (1744, na.Location,
6000                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
6001                                                         na.Name);
6002                                         }
6003                                 }
6004
6005                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
6006                                         continue;
6007
6008                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
6009                                         if (a.IsExtensionType) {
6010                                                 // TODO: Should report better message type, something similar to CS1928/1929 instead of
6011                                                 // CS1061 but that still better than confusing CS0123
6012                                                 var ma = new MemberAccess (a.Expr, member.Name, loc);
6013                                                 ma.Error_TypeDoesNotContainDefinition (ec, a.Expr.Type, ma.Name);
6014                                         } else {
6015                                                 custom_errors.NoArgumentMatch (ec, member);
6016                                         }
6017                                         return false;
6018                                 }
6019
6020                                 Expression conv;
6021                                 if (a.IsExtensionType) {
6022                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
6023                                                 conv = a.Expr;
6024                                         } else {
6025                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
6026                                                 if (conv == null)
6027                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
6028                                         }
6029                                 } else {
6030                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
6031                                 }
6032
6033                                 if (conv == null)
6034                                         break;
6035
6036                                 //
6037                                 // Convert params arguments to an array initializer
6038                                 //
6039                                 if (params_initializers != null) {
6040                                         // we choose to use 'a.Expr' rather than 'conv' so that
6041                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
6042                                         params_initializers.Add (a.Expr);
6043                                         args.RemoveAt (a_idx--);
6044                                         --arg_count;
6045                                         a.Expr = conv;
6046                                         continue;
6047                                 }
6048
6049                                 // Update the argument with the implicit conversion
6050                                 a.Expr = conv;
6051                         }
6052
6053                         if (a_idx != arg_count) {
6054                                 //
6055                                 // Convert all var out argument to error type for less confusing error reporting
6056                                 // when no matching overload is found
6057                                 //
6058                                 for (; a_idx < arg_count; a_idx++) {
6059                                         var arg = args [a_idx];
6060                                         if (arg == null)
6061                                                 continue;
6062
6063                                         if (arg.Type == InternalType.VarOutType) {
6064                                                 ((DeclarationExpression)arg.Expr).Variable.Type = InternalType.ErrorType;
6065                                         }
6066                                 }
6067
6068                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
6069                                 return false;
6070                         }
6071
6072                         //
6073                         // Fill not provided arguments required by params modifier
6074                         //
6075                         if (params_initializers == null && arg_count + 1 == pd.Count) {
6076                                 if (args == null)
6077                                         args = new Arguments (1);
6078
6079                                 pt = ptypes[pd.Count - 1];
6080                                 pt = TypeManager.GetElementType (pt);
6081                                 has_unsafe_arg |= pt.IsPointer;
6082                                 params_initializers = new ArrayInitializer (0, loc);
6083                         }
6084
6085                         //
6086                         // Append an array argument with all params arguments
6087                         //
6088                         if (params_initializers != null) {
6089                                 args.Add (new Argument (
6090                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
6091                                 arg_count++;
6092                         }
6093
6094                         if (has_unsafe_arg) {
6095                                 if (ec.CurrentIterator != null) {
6096                                         Expression.UnsafeInsideIteratorError (ec, loc);
6097                                 } else if (!ec.IsUnsafe) {
6098                                         Expression.UnsafeError (ec, loc);
6099                                 }
6100                         }
6101
6102                         //
6103                         // We could infer inaccesible type arguments
6104                         //
6105                         if (type_arguments == null && member.IsGeneric) {
6106                                 var ms = (MethodSpec) member;
6107                                 foreach (var ta in ms.TypeArguments) {
6108                                         if (!ta.IsAccessible (ec)) {
6109                                                 ec.Report.SymbolRelatedToPreviousError (ta);
6110                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
6111                                                 break;
6112                                         }
6113                                 }
6114                         }
6115
6116                         return true;
6117                 }
6118         }
6119
6120         public class ConstantExpr : MemberExpr
6121         {
6122                 readonly ConstSpec constant;
6123
6124                 public ConstantExpr (ConstSpec constant, Location loc)
6125                 {
6126                         this.constant = constant;
6127                         this.loc = loc;
6128                 }
6129
6130                 public override string Name {
6131                         get { throw new NotImplementedException (); }
6132                 }
6133
6134                 public override string KindName {
6135                         get { return "constant"; }
6136                 }
6137
6138                 public override bool IsInstance {
6139                         get { return !IsStatic; }
6140                 }
6141
6142                 public override bool IsStatic {
6143                         get { return true; }
6144                 }
6145
6146                 protected override TypeSpec DeclaringType {
6147                         get { return constant.DeclaringType; }
6148                 }
6149
6150                 public override Expression CreateExpressionTree (ResolveContext ec)
6151                 {
6152                         throw new NotSupportedException ("ET");
6153                 }
6154
6155                 protected override Expression DoResolve (ResolveContext rc)
6156                 {
6157                         ResolveInstanceExpression (rc, null);
6158                         DoBestMemberChecks (rc, constant);
6159
6160                         if (rc.HasSet (ResolveContext.Options.NameOfScope)) {
6161                                 eclass = ExprClass.Value;
6162                                 type = constant.MemberType;
6163                                 return this;
6164                         }
6165
6166                         var c = constant.GetConstant (rc);
6167
6168                         // Creates reference expression to the constant value
6169                         return Constant.CreateConstantFromValue (constant.MemberType, c.GetValue (), loc);
6170                 }
6171
6172                 public override void Emit (EmitContext ec)
6173                 {
6174                         throw new NotSupportedException ();
6175                 }
6176
6177                 public override string GetSignatureForError ()
6178                 {
6179                         return constant.GetSignatureForError ();
6180                 }
6181
6182                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
6183                 {
6184                         constant.CheckObsoleteness (rc, expr.Location);
6185                 }
6186
6187                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6188                 {
6189                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
6190                 }
6191         }
6192
6193         //
6194         // Fully resolved expression that references a Field
6195         //
6196         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
6197         {
6198                 protected FieldSpec spec;
6199                 VariableInfo variable_info;
6200
6201                 LocalTemporary temp;
6202                 bool prepared;
6203
6204                 protected FieldExpr (Location l)
6205                 {
6206                         loc = l;
6207                 }
6208
6209                 public FieldExpr (FieldSpec spec, Location loc)
6210                 {
6211                         this.spec = spec;
6212                         this.loc = loc;
6213
6214                         type = spec.MemberType;
6215                 }
6216
6217                 public FieldExpr (FieldBase fi, Location l)
6218                         : this (fi.Spec, l)
6219                 {
6220                 }
6221
6222                 #region Properties
6223
6224                 public override string Name {
6225                         get {
6226                                 return spec.Name;
6227                         }
6228                 }
6229
6230                 public bool IsHoisted {
6231                         get {
6232                                 IVariableReference hv = InstanceExpression as IVariableReference;
6233                                 return hv != null && hv.IsHoisted;
6234                         }
6235                 }
6236
6237                 public override bool IsInstance {
6238                         get {
6239                                 return !spec.IsStatic;
6240                         }
6241                 }
6242
6243                 public override bool IsStatic {
6244                         get {
6245                                 return spec.IsStatic;
6246                         }
6247                 }
6248
6249                 public override string KindName {
6250                         get { return "field"; }
6251                 }
6252
6253                 public FieldSpec Spec {
6254                         get {
6255                                 return spec;
6256                         }
6257                 }
6258
6259                 protected override TypeSpec DeclaringType {
6260                         get {
6261                                 return spec.DeclaringType;
6262                         }
6263                 }
6264
6265                 public VariableInfo VariableInfo {
6266                         get {
6267                                 return variable_info;
6268                         }
6269                 }
6270
6271 #endregion
6272
6273                 public override string GetSignatureForError ()
6274                 {
6275                         return spec.GetSignatureForError ();
6276                 }
6277
6278                 public bool IsMarshalByRefAccess (ResolveContext rc)
6279                 {
6280                         // Checks possible ldflda of field access expression
6281                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
6282                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
6283                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
6284                 }
6285
6286                 public void SetHasAddressTaken ()
6287                 {
6288                         IVariableReference vr = InstanceExpression as IVariableReference;
6289                         if (vr != null) {
6290                                 vr.SetHasAddressTaken ();
6291                         }
6292                 }
6293
6294                 protected override void CloneTo (CloneContext clonectx, Expression target)
6295                 {
6296                         var t = (FieldExpr) target;
6297
6298                         if (InstanceExpression != null)
6299                                 t.InstanceExpression = InstanceExpression.Clone (clonectx);
6300                 }
6301
6302                 public override Expression CreateExpressionTree (ResolveContext ec)
6303                 {
6304                         if (ConditionalAccess) {
6305                                 Error_NullShortCircuitInsideExpressionTree (ec);
6306                         }
6307
6308                         return CreateExpressionTree (ec, true);
6309                 }
6310
6311                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
6312                 {
6313                         Arguments args;
6314                         Expression instance;
6315
6316                         if (InstanceExpression == null) {
6317                                 instance = new NullLiteral (loc);
6318                         } else if (convertInstance) {
6319                                 instance = InstanceExpression.CreateExpressionTree (ec);
6320                         } else {
6321                                 args = new Arguments (1);
6322                                 args.Add (new Argument (InstanceExpression));
6323                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
6324                         }
6325
6326                         args = Arguments.CreateForExpressionTree (ec, null,
6327                                 instance,
6328                                 CreateTypeOfExpression ());
6329
6330                         return CreateExpressionFactoryCall (ec, "Field", args);
6331                 }
6332
6333                 public Expression CreateTypeOfExpression ()
6334                 {
6335                         return new TypeOfField (spec, loc);
6336                 }
6337
6338                 protected override Expression DoResolve (ResolveContext ec)
6339                 {
6340                         spec.MemberDefinition.SetIsUsed ();
6341
6342                         return DoResolve (ec, null);
6343                 }
6344
6345                 Expression DoResolve (ResolveContext ec, Expression rhs)
6346                 {
6347                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
6348
6349                         if (rhs != this) {
6350                                 ResolveConditionalAccessReceiver (ec);
6351
6352                                 if (ResolveInstanceExpression (ec, rhs)) {
6353                                         // Resolve the field's instance expression while flow analysis is turned
6354                                         // off: when accessing a field "a.b", we must check whether the field
6355                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
6356
6357                                         if (lvalue_instance) {
6358                                                 bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
6359
6360                                                 Expression right_side =
6361                                                         out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
6362
6363                                                 InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
6364                                         } else {
6365                                                 InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
6366                                         }
6367
6368                                         if (InstanceExpression == null)
6369                                                 return null;
6370                                 }
6371
6372                                 DoBestMemberChecks (ec, spec);
6373
6374                                 if (conditional_access_receiver)
6375                                         ec.With (ResolveContext.Options.DontSetConditionalAccessReceiver, false);
6376                         }
6377
6378                         var fb = spec as FixedFieldSpec;
6379                         IVariableReference var = InstanceExpression as IVariableReference;
6380
6381                         if (fb != null) {
6382                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6383                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
6384                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
6385                                 }
6386
6387                                 if (InstanceExpression.eclass != ExprClass.Variable) {
6388                                         ec.Report.SymbolRelatedToPreviousError (spec);
6389                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
6390                                                 TypeManager.GetFullNameSignature (spec));
6391                                 } else if (var != null && var.IsHoisted) {
6392                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
6393                                 }
6394
6395                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
6396                         }
6397
6398                         //
6399                         // Set flow-analysis variable info for struct member access. It will be check later
6400                         // for precise error reporting
6401                         //
6402                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
6403                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
6404                         }
6405
6406                         if (conditional_access_receiver)
6407                                 type = LiftMemberType (ec, type);
6408
6409                         if (ConditionalAccess && InstanceExpression != null && InstanceExpression.IsNull)
6410                                 return Constant.CreateConstantFromValue (type, null, loc);
6411
6412                         eclass = ExprClass.Variable;
6413                         return this;
6414                 }
6415
6416                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
6417                 {
6418                         spec.CheckObsoleteness (rc, expr.Location);
6419                 }
6420
6421                 public void SetFieldAssigned (FlowAnalysisContext fc)
6422                 {
6423                         if (!IsInstance)
6424                                 return;
6425
6426                         bool lvalue_instance = spec.DeclaringType.IsStruct;
6427                         if (lvalue_instance) {
6428                                 var var = InstanceExpression as IVariableReference;
6429                                 if (var != null && var.VariableInfo != null) {
6430                                         fc.SetStructFieldAssigned (var.VariableInfo, Name);
6431                                 }
6432                         }
6433
6434                         var fe = InstanceExpression as FieldExpr;
6435                         if (fe != null) {
6436                                 Expression instance;
6437
6438                                 do {
6439                                         instance = fe.InstanceExpression;
6440                                         var fe_instance = instance as FieldExpr;
6441                                         if ((fe_instance != null && !fe_instance.IsStatic) || instance is LocalVariableReference) {
6442                                                 if (TypeSpec.IsReferenceType (fe.Type) && instance.Type.IsStruct) {
6443                                                         var var = InstanceExpression as IVariableReference;
6444                                                         if (var != null && var.VariableInfo == null) {
6445                                                                 var var_inst = instance as IVariableReference;
6446                                                                 if (var_inst == null || (var_inst.VariableInfo != null && !fc.IsDefinitelyAssigned (var_inst.VariableInfo)))
6447                                                                         fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
6448                                                         }
6449                                                 }
6450
6451                                                 if (fe_instance != null) {
6452                                                         fe = fe_instance;
6453                                                         continue;
6454                                                 }
6455                                         }
6456
6457                                         break;
6458                                 } while (true);
6459
6460                                 if (instance != null && TypeSpec.IsReferenceType (instance.Type))
6461                                         instance.FlowAnalysis (fc);
6462                         } else {
6463                                 if (TypeSpec.IsReferenceType (InstanceExpression.Type))
6464                                         InstanceExpression.FlowAnalysis (fc);
6465                         }
6466                 }
6467
6468                 Expression Error_AssignToReadonly (ResolveContext rc, Expression right_side)
6469                 {
6470                         // The return value is always null.  Returning a value simplifies calling code.
6471
6472                         if (right_side == EmptyExpression.OutAccess) {
6473                                 if (IsStatic) {
6474                                         rc.Report.Error (199, loc, "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6475                                                 GetSignatureForError ());
6476                                 } else {
6477                                         rc.Report.Error (192, loc, "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6478                                                 GetSignatureForError ());
6479                                 }
6480
6481                                 return null;
6482                         }
6483
6484                         if (right_side == EmptyExpression.LValueMemberAccess) {
6485                                 // Already reported as CS1648/CS1650
6486                                 return null;
6487                         }
6488
6489                         if (right_side == EmptyExpression.LValueMemberOutAccess) {
6490                                 if (IsStatic) {
6491                                         rc.Report.Error (1651, loc, "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6492                                                 GetSignatureForError ());
6493                                 } else {
6494                                         rc.Report.Error (1649, loc, "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6495                                                 GetSignatureForError ());
6496                                 }
6497                                 return null;
6498                         }
6499
6500                         if (IsStatic) {
6501                                 rc.Report.Error (198, loc, "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
6502                                         GetSignatureForError ());
6503                         } else {
6504                                 rc.Report.Error (191, loc, "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
6505                                         GetSignatureForError ());
6506                         }
6507
6508                         return null;
6509                 }
6510
6511                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6512                 {
6513                         if (HasConditionalAccess ())
6514                                 Error_NullPropagatingLValue (ec);
6515
6516                         if (spec is FixedFieldSpec) {
6517                                 // It could be much better error message but we want to be error compatible
6518                                 Error_ValueAssignment (ec, right_side);
6519                         }
6520
6521                         Expression e = DoResolve (ec, right_side);
6522
6523                         if (e == null)
6524                                 return null;
6525
6526                         spec.MemberDefinition.SetIsAssigned ();
6527
6528                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
6529                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
6530                                 ec.Report.Warning (420, 1, loc,
6531                                         "`{0}': A volatile field references will not be treated as volatile",
6532                                         spec.GetSignatureForError ());
6533                         }
6534
6535                         if (spec.IsReadOnly) {
6536                                 // InitOnly fields can only be assigned in constructors or initializers
6537                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
6538                                         return Error_AssignToReadonly (ec, right_side);
6539
6540                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
6541
6542                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
6543                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
6544                                                 return Error_AssignToReadonly (ec, right_side);
6545                                         // static InitOnly fields cannot be assigned-to in an instance constructor
6546                                         if (IsStatic && !ec.IsStatic)
6547                                                 return Error_AssignToReadonly (ec, right_side);
6548                                         // instance constructors can't modify InitOnly fields of other instances of the same type
6549                                         if (!IsStatic && !(InstanceExpression is This))
6550                                                 return Error_AssignToReadonly (ec, right_side);
6551                                 }
6552                         }
6553
6554                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
6555                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
6556                                 ec.Report.Warning (197, 1, loc,
6557                                                 "Passing `{0}' as ref or out or taking its address may cause a runtime exception because it is a field of a marshal-by-reference class",
6558                                                 GetSignatureForError ());
6559                         }
6560
6561                         eclass = ExprClass.Variable;
6562                         return this;
6563                 }
6564
6565                 public override void FlowAnalysis (FlowAnalysisContext fc)
6566                 {
6567                         var var = InstanceExpression as IVariableReference;
6568                         if (var != null) {
6569                                 var vi = var.VariableInfo;
6570                                 if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, Name)) {
6571                                         fc.Report.Error (170, loc, "Use of possibly unassigned field `{0}'", Name);
6572                                         return;
6573                                 }
6574
6575                                 if (TypeSpec.IsValueType (InstanceExpression.Type)) {
6576                                         var le = SkipLeftValueTypeAccess (InstanceExpression);
6577                                         if (le != null)
6578                                                 le.FlowAnalysis (fc);
6579
6580                                         return;
6581                                 }
6582                         }
6583
6584                         var da = conditional_access_receiver ? fc.BranchDefiniteAssignment () : null;
6585
6586                         base.FlowAnalysis (fc);
6587
6588                         if (conditional_access_receiver)
6589                                 fc.DefiniteAssignment = da;
6590                 }
6591
6592                 static Expression SkipLeftValueTypeAccess (Expression expr)
6593                 {
6594                         if (!TypeSpec.IsValueType (expr.Type))
6595                                 return expr;
6596
6597                         if (expr is VariableReference)
6598                                 return null;
6599
6600                         var fe = expr as FieldExpr;
6601                         if (fe == null)
6602                                 return expr;
6603
6604                         if (fe.InstanceExpression == null)
6605                                 return expr;
6606
6607                         return SkipLeftValueTypeAccess (fe.InstanceExpression);
6608                 }
6609
6610                 public override int GetHashCode ()
6611                 {
6612                         return spec.GetHashCode ();
6613                 }
6614
6615                 public bool IsFixed {
6616                         get {
6617                                 //
6618                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
6619                                 //
6620                                 IVariableReference variable = InstanceExpression as IVariableReference;
6621                                 if (variable != null)
6622                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
6623
6624                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6625                                 return fe != null && fe.IsFixed;
6626                         }
6627                 }
6628
6629                 public override bool Equals (object obj)
6630                 {
6631                         FieldExpr fe = obj as FieldExpr;
6632                         if (fe == null)
6633                                 return false;
6634
6635                         if (spec != fe.spec)
6636                                 return false;
6637
6638                         if (InstanceExpression == null || fe.InstanceExpression == null)
6639                                 return true;
6640
6641                         return InstanceExpression.Equals (fe.InstanceExpression);
6642                 }
6643
6644                 public void Emit (EmitContext ec, bool leave_copy)
6645                 {
6646                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6647
6648                         if (IsStatic){
6649                                 if (is_volatile)
6650                                         ec.Emit (OpCodes.Volatile);
6651
6652                                 ec.Emit (OpCodes.Ldsfld, spec);
6653                         } else {
6654                                 var ca = ec.ConditionalAccess;
6655
6656                                 if (!prepared) {
6657                                         if (conditional_access_receiver)
6658                                                 ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
6659
6660                                         EmitInstance (ec, false);
6661                                 }
6662
6663                                 // Optimization for build-in types
6664                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
6665                                         ec.EmitLoadFromPtr (type);
6666                                 } else {
6667                                         var ff = spec as FixedFieldSpec;
6668                                         if (ff != null) {
6669                                                 ec.Emit (OpCodes.Ldflda, spec);
6670                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
6671                                         } else {
6672                                                 if (is_volatile)
6673                                                         ec.Emit (OpCodes.Volatile);
6674
6675                                                 ec.Emit (OpCodes.Ldfld, spec);
6676                                         }
6677                                 }
6678
6679                                 if (conditional_access_receiver) {
6680                                         ec.CloseConditionalAccess (type.IsNullableType && type != spec.MemberType ? type : null);
6681                                         ec.ConditionalAccess = ca;
6682                                 }
6683                         }
6684
6685                         if (leave_copy) {
6686                                 ec.Emit (OpCodes.Dup);
6687                                 if (!IsStatic) {
6688                                         temp = new LocalTemporary (this.Type);
6689                                         temp.Store (ec);
6690                                 }
6691                         }
6692                 }
6693
6694                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6695                 {
6696                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
6697                         if (isCompound && !(source is DynamicExpressionStatement) && !has_await_source) {
6698                                 prepared = true;
6699                         }
6700
6701                         if (IsInstance) {
6702                                 if (ConditionalAccess)
6703                                         throw new NotImplementedException ("null operator assignment");
6704
6705                                 if (has_await_source)
6706                                         source = source.EmitToField (ec);
6707
6708                                 EmitInstance (ec, prepared);
6709                         }
6710
6711                         source.Emit (ec);
6712
6713                         if (leave_copy || ec.NotifyEvaluatorOnStore) {
6714                                 ec.Emit (OpCodes.Dup);
6715                                 if (!IsStatic) {
6716                                         temp = new LocalTemporary (this.Type);
6717                                         temp.Store (ec);
6718                                 }
6719                         }
6720
6721                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
6722                                 ec.Emit (OpCodes.Volatile);
6723
6724                         spec.MemberDefinition.SetIsAssigned ();
6725
6726                         if (IsStatic)
6727                                 ec.Emit (OpCodes.Stsfld, spec);
6728                         else
6729                                 ec.Emit (OpCodes.Stfld, spec);
6730
6731                         if (ec.NotifyEvaluatorOnStore) {
6732                                 if (!IsStatic)
6733                                         throw new NotImplementedException ("instance field write");
6734
6735                                 if (leave_copy)
6736                                         ec.Emit (OpCodes.Dup);
6737
6738                                 ec.Module.Evaluator.EmitValueChangedCallback (ec, Name, type, loc);
6739                         }
6740
6741                         if (temp != null) {
6742                                 temp.Emit (ec);
6743                                 temp.Release (ec);
6744                                 temp = null;
6745                         }
6746                 }
6747
6748                 //
6749                 // Emits store to field with prepared values on stack
6750                 //
6751                 public void EmitAssignFromStack (EmitContext ec)
6752                 {
6753                         if (IsStatic) {
6754                                 ec.Emit (OpCodes.Stsfld, spec);
6755                         } else {
6756                                 ec.Emit (OpCodes.Stfld, spec);
6757                         }
6758                 }
6759
6760                 public override void Emit (EmitContext ec)
6761                 {
6762                         Emit (ec, false);
6763                 }
6764
6765                 public override void EmitSideEffect (EmitContext ec)
6766                 {
6767                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6768
6769                         if (is_volatile) // || is_marshal_by_ref ())
6770                                 base.EmitSideEffect (ec);
6771                 }
6772
6773                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
6774                 {
6775                         if ((mode & AddressOp.Store) != 0)
6776                                 spec.MemberDefinition.SetIsAssigned ();
6777                         if ((mode & AddressOp.Load) != 0)
6778                                 spec.MemberDefinition.SetIsUsed ();
6779
6780                         //
6781                         // Handle initonly fields specially: make a copy and then
6782                         // get the address of the copy.
6783                         //
6784                         bool need_copy;
6785                         if (spec.IsReadOnly){
6786                                 need_copy = true;
6787                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
6788                                         if (IsStatic){
6789                                                 if (ec.IsStatic)
6790                                                         need_copy = false;
6791                                         } else
6792                                                 need_copy = false;
6793                                 }
6794                         } else
6795                                 need_copy = false;
6796
6797                         if (need_copy) {
6798                                 Emit (ec);
6799                                 var temp = ec.GetTemporaryLocal (type);
6800                                 ec.Emit (OpCodes.Stloc, temp);
6801                                 ec.Emit (OpCodes.Ldloca, temp);
6802                                 return;
6803                         }
6804
6805
6806                         if (IsStatic){
6807                                 ec.Emit (OpCodes.Ldsflda, spec);
6808                         } else {
6809                                 if (!prepared)
6810                                         EmitInstance (ec, false);
6811                                 ec.Emit (OpCodes.Ldflda, spec);
6812                         }
6813                 }
6814
6815                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6816                 {
6817                         return MakeExpression (ctx);
6818                 }
6819
6820                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6821                 {
6822 #if STATIC
6823                         return base.MakeExpression (ctx);
6824 #else
6825                         return SLE.Expression.Field (
6826                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
6827                                 spec.GetMetaInfo ());
6828 #endif
6829                 }
6830
6831                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6832                 {
6833                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
6834                 }
6835         }
6836
6837
6838         //
6839         // Expression that evaluates to a Property.
6840         //
6841         // This is not an LValue because we need to re-write the expression. We
6842         // can not take data from the stack and store it.
6843         //
6844         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
6845         {
6846                 Arguments arguments;
6847                 FieldExpr backing_field;
6848
6849                 public PropertyExpr (PropertySpec spec, Location l)
6850                         : base (l)
6851                 {
6852                         best_candidate = spec;
6853                         type = spec.MemberType;
6854                 }
6855
6856                 #region Properties
6857
6858                 protected override Arguments Arguments {
6859                         get {
6860                                 return arguments;
6861                         }
6862                         set {
6863                                 arguments = value;
6864                         }
6865                 }
6866
6867                 protected override TypeSpec DeclaringType {
6868                         get {
6869                                 return best_candidate.DeclaringType;
6870                         }
6871                 }
6872
6873                 public override string Name {
6874                         get {
6875                                 return best_candidate.Name;
6876                         }
6877                 }
6878
6879                 public bool IsAutoPropertyAccess {
6880                         get {
6881                                 var prop = best_candidate.MemberDefinition as Property;
6882                                 return prop != null && prop.BackingField != null;
6883                         }
6884                 }
6885
6886                 public override bool IsInstance {
6887                         get {
6888                                 return !IsStatic;
6889                         }
6890                 }
6891
6892                 public override bool IsStatic {
6893                         get {
6894                                 return best_candidate.IsStatic;
6895                         }
6896                 }
6897
6898                 public override string KindName {
6899                         get { return "property"; }
6900                 }
6901
6902                 public PropertySpec PropertyInfo {
6903                         get {
6904                                 return best_candidate;
6905                         }
6906                 }
6907
6908                 #endregion
6909
6910                 public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
6911                 {
6912                         if (best_candidate == null || !(best_candidate.IsStatic || InstanceExpression is This))
6913                                 return null;
6914
6915                         var args_count = arguments == null ? 0 : arguments.Count;
6916                         if (args_count != body.Parameters.Count && args_count == 0)
6917                                 return null;
6918
6919                         var mg = MethodGroupExpr.CreatePredefined (best_candidate.Get, DeclaringType, loc);
6920                         mg.InstanceExpression = InstanceExpression;
6921
6922                         return mg;
6923                 }
6924
6925                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
6926                 {
6927                         return new PropertyExpr (spec, loc) {
6928                                 Getter = spec.Get,
6929                                 Setter = spec.Set
6930                         };
6931                 }
6932
6933                 public override Expression CreateExpressionTree (ResolveContext ec)
6934                 {
6935                         if (ConditionalAccess) {
6936                                 Error_NullShortCircuitInsideExpressionTree (ec);
6937                         }
6938
6939                         Arguments args;
6940                         if (IsSingleDimensionalArrayLength ()) {
6941                                 args = new Arguments (1);
6942                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6943                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
6944                         }
6945
6946                         args = new Arguments (2);
6947                         if (InstanceExpression == null)
6948                                 args.Add (new Argument (new NullLiteral (loc)));
6949                         else
6950                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6951                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
6952                         return CreateExpressionFactoryCall (ec, "Property", args);
6953                 }
6954
6955                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
6956                 {
6957                         DoResolveLValue (rc, null);
6958                         return new TypeOfMethod (Setter, loc);
6959                 }
6960
6961                 public override string GetSignatureForError ()
6962                 {
6963                         return best_candidate.GetSignatureForError ();
6964                 }
6965
6966                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6967                 {
6968 #if STATIC
6969                         return base.MakeExpression (ctx);
6970 #else
6971                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
6972 #endif
6973                 }
6974
6975                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6976                 {
6977 #if STATIC
6978                         return base.MakeExpression (ctx);
6979 #else
6980                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
6981 #endif
6982                 }
6983
6984                 void Error_PropertyNotValid (ResolveContext ec)
6985                 {
6986                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
6987                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
6988                                 GetSignatureForError ());
6989                 }
6990
6991                 bool IsSingleDimensionalArrayLength ()
6992                 {
6993                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
6994                                 return false;
6995
6996                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
6997                         return ac != null && ac.Rank == 1;
6998                 }
6999
7000                 public override void Emit (EmitContext ec, bool leave_copy)
7001                 {
7002                         //
7003                         // Special case: length of single dimension array property is turned into ldlen
7004                         //
7005                         if (IsSingleDimensionalArrayLength ()) {
7006                                 if (conditional_access_receiver) {
7007                                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7008                                 }
7009
7010                                 EmitInstance (ec, false);
7011
7012                                 ec.Emit (OpCodes.Ldlen);
7013                                 ec.Emit (OpCodes.Conv_I4);
7014
7015                                 if (conditional_access_receiver) {
7016                                         ec.CloseConditionalAccess (type);
7017                                 }
7018
7019                                 return;
7020                         }
7021
7022                         base.Emit (ec, leave_copy);
7023                 }
7024
7025                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
7026                 {
7027                         if (backing_field != null) {
7028                                 backing_field.EmitAssign (ec, source, leave_copy, false);
7029                                 return;
7030                         }
7031
7032                         Arguments args;
7033                         LocalTemporary await_source_arg = null;
7034
7035                         if (isCompound && !(source is DynamicExpressionStatement)) {
7036                                 emitting_compound_assignment = true;
7037                                 source.Emit (ec);
7038
7039                                 if (has_await_arguments) {
7040                                         await_source_arg = new LocalTemporary (Type);
7041                                         await_source_arg.Store (ec);
7042
7043                                         args = new Arguments (1);
7044                                         args.Add (new Argument (await_source_arg));
7045
7046                                         if (leave_copy) {
7047                                                 temp = await_source_arg;
7048                                         }
7049
7050                                         has_await_arguments = false;
7051                                 } else {
7052                                         args = null;
7053
7054                                         if (leave_copy) {
7055                                                 ec.Emit (OpCodes.Dup);
7056                                                 temp = new LocalTemporary (this.Type);
7057                                                 temp.Store (ec);
7058                                         }
7059                                 }
7060                         } else {
7061                                 args = arguments ?? new Arguments (1);
7062
7063                                 if (leave_copy) {
7064                                         source.Emit (ec);
7065                                         temp = new LocalTemporary (this.Type);
7066                                         temp.Store (ec);
7067                                         args.Add (new Argument (temp));
7068                                 } else {
7069                                         args.Add (new Argument (source));
7070                                 }
7071                         }
7072
7073                         emitting_compound_assignment = false;
7074
7075                         var call = new CallEmitter ();
7076                         call.InstanceExpression = InstanceExpression;
7077                         if (args == null)
7078                                 call.InstanceExpressionOnStack = true;
7079
7080                         if (ConditionalAccess) {
7081                                 call.ConditionalAccess = true;
7082                         }
7083
7084                         if (leave_copy)
7085                                 call.Emit (ec, Setter, args, loc);
7086                         else
7087                                 call.EmitStatement (ec, Setter, args, loc);
7088
7089                         if (temp != null) {
7090                                 temp.Emit (ec);
7091                                 temp.Release (ec);
7092                         }
7093
7094                         if (await_source_arg != null) {
7095                                 await_source_arg.Release (ec);
7096                         }
7097                 }
7098
7099                 public override void FlowAnalysis (FlowAnalysisContext fc)
7100                 {
7101                         var prop = best_candidate.MemberDefinition as Property;
7102                         if (prop != null && prop.BackingField != null) {
7103                                 var var = InstanceExpression as IVariableReference;
7104                                 if (var != null) {
7105                                         var vi = var.VariableInfo;
7106                                         if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, prop.BackingField.Name)) {
7107                                                 fc.Report.Error (8079, loc, "Use of possibly unassigned auto-implemented property `{0}'", Name);
7108                                                 return;
7109                                         }
7110
7111                                         if (TypeSpec.IsValueType (InstanceExpression.Type) && InstanceExpression is VariableReference)
7112                                                 return;
7113                                 }
7114                         }
7115
7116                         var da = conditional_access_receiver ? fc.BranchDefiniteAssignment () : null;
7117
7118                         base.FlowAnalysis (fc);
7119
7120                         if (conditional_access_receiver)
7121                                 fc.DefiniteAssignment = da;
7122                 }
7123
7124                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
7125                 {
7126                         eclass = ExprClass.PropertyAccess;
7127
7128                         if (best_candidate.IsNotCSharpCompatible) {
7129                                 Error_PropertyNotValid (rc);
7130                         }
7131
7132                         ResolveInstanceExpression (rc, right_side);
7133
7134                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
7135                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
7136                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
7137                                 if (p != null) {
7138                                         type = p.MemberType;
7139                                 }
7140                         }
7141
7142                         DoBestMemberChecks (rc, best_candidate);
7143
7144                         // Handling of com-imported properties with any number of default property parameters
7145                         if (best_candidate.HasGet && !best_candidate.Get.Parameters.IsEmpty) {
7146                                 var p = best_candidate.Get.Parameters;
7147                                 arguments = new Arguments (p.Count);
7148                                 for (int i = 0; i < p.Count; ++i) {
7149                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
7150                                 }
7151                         } else if (best_candidate.HasSet && best_candidate.Set.Parameters.Count > 1) {
7152                                 var p = best_candidate.Set.Parameters;
7153                                 arguments = new Arguments (p.Count - 1);
7154                                 for (int i = 0; i < p.Count - 1; ++i) {
7155                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
7156                                 }
7157                         }
7158
7159                         return this;
7160                 }
7161
7162                 protected override bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7163                 {
7164                         if (!rc.HasSet (ResolveContext.Options.ConstructorScope))
7165                                 return false;
7166
7167                         var prop = best_candidate.MemberDefinition as Property;
7168                         if (prop == null || prop.Parent.PartialContainer != rc.CurrentMemberDefinition.Parent.PartialContainer) {
7169                                 var ps = MemberCache.FindMember (rc.CurrentType, MemberFilter.Property (best_candidate.Name, best_candidate.MemberType), BindingRestriction.DeclaredOnly) as PropertySpec;
7170                                 if (ps == null)
7171                                         return false;
7172
7173                                 prop = (Property)ps.MemberDefinition;
7174                         }
7175
7176                         var spec = prop.BackingField;
7177                         if (spec == null)
7178                                 return false;
7179
7180                         if (rc.IsStatic != spec.IsStatic)
7181                                 return false;
7182
7183                         if (!spec.IsStatic && (!(InstanceExpression is This) || InstanceExpression is BaseThis))
7184                                 return false;
7185
7186                         backing_field = new FieldExpr (prop.BackingField, loc);
7187                         backing_field.ResolveLValue (rc, rhs);
7188                         return true;
7189                 }
7190
7191                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
7192                 {
7193                         if (!best_candidate.IsAccessible (rc))
7194                                 ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), expr.Location);
7195
7196                         best_candidate.CheckObsoleteness (rc, expr.Location);
7197                 }
7198
7199                 public void SetBackingFieldAssigned (FlowAnalysisContext fc)
7200                 {
7201                         if (backing_field != null) {
7202                                 backing_field.SetFieldAssigned (fc);
7203                                 return;
7204                         }
7205
7206                         if (!IsAutoPropertyAccess)
7207                                 return;
7208
7209                         var prop = best_candidate.MemberDefinition as Property;
7210                         if (prop != null && prop.BackingField != null) {
7211                                 bool lvalue_instance = best_candidate.DeclaringType.IsStruct;
7212                                 if (lvalue_instance) {
7213                                         var var = InstanceExpression as IVariableReference;
7214                                         if (var != null && var.VariableInfo != null) {
7215                                                 fc.SetStructFieldAssigned (var.VariableInfo, prop.BackingField.Name);
7216                                         }
7217                                 }
7218                         }
7219                 }
7220
7221                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7222                 {
7223                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
7224                 }
7225         }
7226
7227         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
7228         {
7229                 // getter and setter can be different for base calls
7230                 MethodSpec getter, setter;
7231                 protected T best_candidate;
7232
7233                 protected LocalTemporary temp;
7234                 protected bool emitting_compound_assignment;
7235                 protected bool has_await_arguments;
7236
7237                 protected PropertyOrIndexerExpr (Location l)
7238                 {
7239                         loc = l;
7240                 }
7241
7242                 #region Properties
7243
7244                 protected abstract Arguments Arguments { get; set; }
7245
7246                 public MethodSpec Getter {
7247                         get {
7248                                 return getter;
7249                         }
7250                         set {
7251                                 getter = value;
7252                         }
7253                 }
7254
7255                 public MethodSpec Setter {
7256                         get {
7257                                 return setter;
7258                         }
7259                         set {
7260                                 setter = value;
7261                         }
7262                 }
7263
7264                 #endregion
7265
7266                 protected override Expression DoResolve (ResolveContext ec)
7267                 {
7268                         if (eclass == ExprClass.Unresolved) {
7269                                 ResolveConditionalAccessReceiver (ec);
7270
7271                                 var expr = OverloadResolve (ec, null);
7272                                 if (expr == null)
7273                                         return null;
7274
7275                                 if (expr != this) {
7276                                         using (ec.With (ResolveContext.Options.DontSetConditionalAccessReceiver, conditional_access_receiver))
7277                                                 return expr.Resolve (ec);
7278                                 }
7279
7280                                 if (conditional_access_receiver) {
7281                                         type = LiftMemberType (ec, type);
7282                                 }
7283                         }
7284
7285                         if (!ResolveGetter (ec))
7286                                 return null;
7287
7288                         return this;
7289                 }
7290
7291                 public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
7292                 {
7293                         if (HasConditionalAccess ())
7294                                 Error_NullPropagatingLValue (rc);
7295
7296                         if (right_side == EmptyExpression.OutAccess) {
7297                                 // TODO: best_candidate can be null at this point
7298                                 INamedBlockVariable variable = null;
7299                                 if (best_candidate != null && rc.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, rc.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
7300                                         rc.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
7301                                                 best_candidate.Name);
7302                                 } else {
7303                                         right_side.DoResolveLValue (rc, this);
7304                                 }
7305                                 return null;
7306                         }
7307
7308                         if (eclass == ExprClass.Unresolved) {
7309                                 var expr = OverloadResolve (rc, right_side);
7310                                 if (expr == null)
7311                                         return null;
7312
7313                                 if (expr != this)
7314                                         return expr.ResolveLValue (rc, right_side);
7315                         } else {
7316                                 ResolveInstanceExpression (rc, right_side);
7317                         }
7318
7319                         if (!best_candidate.HasSet) {
7320                                 if (ResolveAutopropertyAssignment (rc, right_side))
7321                                         return this;
7322
7323                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
7324                                         GetSignatureForError ());
7325                                 return null;
7326                         }
7327
7328                         if (!best_candidate.Set.IsAccessible (rc) || !best_candidate.Set.DeclaringType.IsAccessible (rc)) {
7329                                 if (best_candidate.HasDifferentAccessibility) {
7330                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7331                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
7332                                                 GetSignatureForError ());
7333                                 } else {
7334                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7335                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
7336                                 }
7337                         }
7338
7339                         if (best_candidate.HasDifferentAccessibility)
7340                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
7341
7342                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
7343                         return this;
7344                 }
7345
7346                 void EmitConditionalAccess (EmitContext ec, ref CallEmitter call, MethodSpec method, Arguments arguments)
7347                 {
7348                         var ca = ec.ConditionalAccess;
7349                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7350
7351                         call.Emit (ec, method, arguments, loc);
7352
7353                         ec.CloseConditionalAccess (method.ReturnType != type && type.IsNullableType ? type : null);
7354                         ec.ConditionalAccess = ca;
7355                 }
7356
7357                 //
7358                 // Implements the IAssignMethod interface for assignments
7359                 //
7360                 public virtual void Emit (EmitContext ec, bool leave_copy)
7361                 {
7362                         var call = new CallEmitter ();
7363                         call.ConditionalAccess = ConditionalAccess;
7364                         call.InstanceExpression = InstanceExpression;
7365                         if (has_await_arguments)
7366                                 call.HasAwaitArguments = true;
7367                         else
7368                                 call.DuplicateArguments = emitting_compound_assignment;
7369
7370                         if (conditional_access_receiver)
7371                                 EmitConditionalAccess (ec, ref call, Getter, Arguments);
7372                         else
7373                                 call.Emit (ec, Getter, Arguments, loc);
7374
7375                         if (call.HasAwaitArguments) {
7376                                 InstanceExpression = call.InstanceExpression;
7377                                 Arguments = call.EmittedArguments;
7378                                 has_await_arguments = true;
7379                         }
7380
7381                         if (leave_copy) {
7382                                 ec.Emit (OpCodes.Dup);
7383                                 temp = new LocalTemporary (Type);
7384                                 temp.Store (ec);
7385                         }
7386                 }
7387
7388                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
7389
7390                 public override void Emit (EmitContext ec)
7391                 {
7392                         Emit (ec, false);
7393                 }
7394
7395                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
7396                 {
7397                         has_await_arguments = true;
7398                         Emit (ec, false);
7399                         return null;
7400                 }
7401
7402                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
7403
7404                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
7405
7406                 bool ResolveGetter (ResolveContext rc)
7407                 {
7408                         if (!best_candidate.HasGet) {
7409                                 if (InstanceExpression != EmptyExpression.Null) {
7410                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
7411                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
7412                                                 best_candidate.GetSignatureForError ());
7413                                         return false;
7414                                 }
7415                         } else if (!best_candidate.Get.IsAccessible (rc) || !best_candidate.Get.DeclaringType.IsAccessible (rc)) {
7416                                 if (best_candidate.HasDifferentAccessibility) {
7417                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7418                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
7419                                                 TypeManager.CSharpSignature (best_candidate));
7420                                 } else {
7421                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7422                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
7423                                 }
7424                         }
7425
7426                         if (best_candidate.HasDifferentAccessibility) {
7427                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
7428                         }
7429
7430                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
7431                         return true;
7432                 }
7433
7434                 protected virtual bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7435                 {
7436                         return false;
7437                 }
7438         }
7439
7440         /// <summary>
7441         ///   Fully resolved expression that evaluates to an Event
7442         /// </summary>
7443         public class EventExpr : MemberExpr, IAssignMethod
7444         {
7445                 readonly EventSpec spec;
7446                 MethodSpec op;
7447
7448                 public EventExpr (EventSpec spec, Location loc)
7449                 {
7450                         this.spec = spec;
7451                         this.loc = loc;
7452                 }
7453
7454                 #region Properties
7455
7456                 protected override TypeSpec DeclaringType {
7457                         get {
7458                                 return spec.DeclaringType;
7459                         }
7460                 }
7461
7462                 public override string Name {
7463                         get {
7464                                 return spec.Name;
7465                         }
7466                 }
7467
7468                 public override bool IsInstance {
7469                         get {
7470                                 return !spec.IsStatic;
7471                         }
7472                 }
7473
7474                 public override bool IsStatic {
7475                         get {
7476                                 return spec.IsStatic;
7477                         }
7478                 }
7479
7480                 public override string KindName {
7481                         get { return "event"; }
7482                 }
7483
7484                 public MethodSpec Operator {
7485                         get {
7486                                 return op;
7487                         }
7488                 }
7489
7490                 #endregion
7491
7492                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
7493                 {
7494                         //
7495                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
7496                         //
7497                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7498                                 if (spec.BackingField != null &&
7499                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
7500
7501                                         spec.MemberDefinition.SetIsUsed ();
7502
7503                                         spec.CheckObsoleteness (ec, loc);
7504
7505                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
7506                                                 Error_AssignmentEventOnly (ec);
7507
7508                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
7509
7510                                         InstanceExpression = null;
7511
7512                                         return ml.ResolveMemberAccess (ec, left, original);
7513                                 }
7514                         }
7515
7516                         return base.ResolveMemberAccess (ec, left, original);
7517                 }
7518
7519                 public override Expression CreateExpressionTree (ResolveContext ec)
7520                 {
7521                         throw new NotSupportedException ("ET");
7522                 }
7523
7524                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7525                 {
7526                         if (right_side == EmptyExpression.EventAddition) {
7527                                 op = spec.AccessorAdd;
7528                         } else if (right_side == EmptyExpression.EventSubtraction) {
7529                                 op = spec.AccessorRemove;
7530                         }
7531
7532                         if (op == null) {
7533                                 Error_AssignmentEventOnly (ec);
7534                                 return null;
7535                         }
7536
7537                         if (HasConditionalAccess ())
7538                                 Error_NullPropagatingLValue (ec);
7539
7540                         op = CandidateToBaseOverride (ec, op);
7541                         return this;
7542                 }
7543
7544                 protected override Expression DoResolve (ResolveContext ec)
7545                 {
7546                         eclass = ExprClass.EventAccess;
7547                         type = spec.MemberType;
7548
7549                         ResolveInstanceExpression (ec, null);
7550
7551                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7552                                 Error_AssignmentEventOnly (ec);
7553                         }
7554
7555                         DoBestMemberChecks (ec, spec);
7556                         return this;
7557                 }
7558
7559                 public override void Emit (EmitContext ec)
7560                 {
7561                         throw new NotSupportedException ();
7562                         //Error_CannotAssign ();
7563                 }
7564
7565                 #region IAssignMethod Members
7566
7567                 public void Emit (EmitContext ec, bool leave_copy)
7568                 {
7569                         throw new NotImplementedException ();
7570                 }
7571
7572                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
7573                 {
7574                         if (leave_copy || !isCompound)
7575                                 throw new NotImplementedException ("EventExpr::EmitAssign");
7576
7577                         Arguments args = new Arguments (1);
7578                         args.Add (new Argument (source));
7579
7580                         // TODO: Wrong, needs receiver
7581 //                      if (NullShortCircuit) {
7582 //                              ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7583 //                      }
7584
7585                         var call = new CallEmitter ();
7586                         call.InstanceExpression = InstanceExpression;
7587                         call.ConditionalAccess = ConditionalAccess;
7588                         call.EmitStatement (ec, op, args, loc);
7589
7590 //                      if (NullShortCircuit)
7591 //                              ec.CloseConditionalAccess (null);
7592                 }
7593
7594                 #endregion
7595
7596                 void Error_AssignmentEventOnly (ResolveContext ec)
7597                 {
7598                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
7599                                 ec.Report.Error (79, loc,
7600                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
7601                                         GetSignatureForError ());
7602                         } else {
7603                                 ec.Report.Error (70, loc,
7604                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
7605                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
7606                         }
7607                 }
7608
7609                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
7610                 {
7611                         name = name.Substring (0, name.LastIndexOf ('.'));
7612                         base.Error_CannotCallAbstractBase (rc, name);
7613                 }
7614
7615                 public override string GetSignatureForError ()
7616                 {
7617                         return TypeManager.CSharpSignature (spec);
7618                 }
7619
7620                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
7621                 {
7622                         spec.CheckObsoleteness (rc, expr.Location);
7623                 }
7624
7625                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7626                 {
7627                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
7628                 }
7629         }
7630
7631         public class TemporaryVariableReference : VariableReference
7632         {
7633                 public class Declarator : Statement
7634                 {
7635                         TemporaryVariableReference variable;
7636
7637                         public Declarator (TemporaryVariableReference variable)
7638                         {
7639                                 this.variable = variable;
7640                                 loc = variable.loc;
7641                         }
7642
7643                         protected override void DoEmit (EmitContext ec)
7644                         {
7645                                 variable.li.CreateBuilder (ec);
7646                         }
7647
7648                         public override void Emit (EmitContext ec)
7649                         {
7650                                 // Don't create sequence point
7651                                 DoEmit (ec);
7652                         }
7653
7654                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7655                         {
7656                                 return false;
7657                         }
7658
7659                         protected override void CloneTo (CloneContext clonectx, Statement target)
7660                         {
7661                                 // Nothing
7662                         }
7663                 }
7664
7665                 LocalVariable li;
7666
7667                 public TemporaryVariableReference (LocalVariable li, Location loc)
7668                 {
7669                         this.li = li;
7670                         this.type = li.Type;
7671                         this.loc = loc;
7672                 }
7673
7674                 public override bool IsLockedByStatement {
7675                         get {
7676                                 return false;
7677                         }
7678                         set {
7679                         }
7680                 }
7681
7682                 public LocalVariable LocalInfo {
7683                     get {
7684                         return li;
7685                     }
7686                 }
7687
7688                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc, bool writeToSymbolFile = false)
7689                 {
7690                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc, writeToSymbolFile);
7691                         return new TemporaryVariableReference (li, loc);
7692                 }
7693
7694                 protected override Expression DoResolve (ResolveContext ec)
7695                 {
7696                         eclass = ExprClass.Variable;
7697
7698                         //
7699                         // Don't capture temporary variables except when using
7700                         // state machine redirection and block yields
7701                         //
7702                         if (ec.CurrentAnonymousMethod is StateMachineInitializer &&
7703                                 (ec.CurrentBlock.Explicit.HasYield || ec.CurrentBlock.Explicit.HasAwait) &&
7704                                 ec.IsVariableCapturingRequired) {
7705                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
7706                                 storey.CaptureLocalVariable (ec, li);
7707                         }
7708
7709                         return this;
7710                 }
7711
7712                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7713                 {
7714                         return Resolve (ec);
7715                 }
7716
7717                 public override void Emit (EmitContext ec)
7718                 {
7719                         li.CreateBuilder (ec);
7720
7721                         Emit (ec, false);
7722                 }
7723
7724                 public void EmitAssign (EmitContext ec, Expression source)
7725                 {
7726                         li.CreateBuilder (ec);
7727
7728                         EmitAssign (ec, source, false, false);
7729                 }
7730
7731                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
7732                 {
7733                         return li.HoistedVariant;
7734                 }
7735
7736                 public override bool IsFixed {
7737                         get { return true; }
7738                 }
7739
7740                 public override bool IsRef {
7741                         get { return false; }
7742                 }
7743
7744                 public override string Name {
7745                         get { throw new NotImplementedException (); }
7746                 }
7747
7748                 public override void SetHasAddressTaken ()
7749                 {
7750                         throw new NotImplementedException ();
7751                 }
7752
7753                 protected override ILocalVariable Variable {
7754                         get { return li; }
7755                 }
7756
7757                 public override VariableInfo VariableInfo {
7758                         get { return null; }
7759                 }
7760         }
7761
7762         ///
7763         /// Handles `var' contextual keyword; var becomes a keyword only
7764         /// if no type called var exists in a variable scope
7765         ///
7766         class VarExpr : SimpleName
7767         {
7768                 public VarExpr (Location loc)
7769                         : base ("var", loc)
7770                 {
7771                 }
7772
7773                 public bool InferType (ResolveContext ec, Expression right_side)
7774                 {
7775                         if (type != null)
7776                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
7777
7778                         type = right_side.Type;
7779                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
7780                                 ec.Report.Error (815, loc,
7781                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
7782                                         type.GetSignatureForError ());
7783                                 type = InternalType.ErrorType;
7784                                 return false;
7785                         }
7786
7787                         eclass = ExprClass.Variable;
7788                         return true;
7789                 }
7790
7791                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
7792                 {
7793                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
7794                                 base.Error_TypeOrNamespaceNotFound (ec);
7795                         else
7796                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
7797                 }
7798         }
7799 }