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