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                 public virtual void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
3652                 {
3653
3654                 }
3655
3656                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
3657                 {
3658                         var inst = new InstanceEmitter (InstanceExpression, TypeSpec.IsValueType (InstanceExpression.Type));
3659                         inst.Emit (ec, ConditionalAccess);
3660
3661                         if (prepare_for_load)
3662                                 ec.Emit (OpCodes.Dup);
3663                 }
3664
3665                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3666         }
3667
3668         public class ExtensionMethodCandidates
3669         {
3670                 readonly NamespaceContainer container;
3671                 readonly IList<MethodSpec> methods;
3672                 readonly int index;
3673                 readonly IMemberContext context;
3674
3675                 public ExtensionMethodCandidates (IMemberContext context, IList<MethodSpec> methods, NamespaceContainer nsContainer, int lookupIndex)
3676                 {
3677                         this.context = context;
3678                         this.methods = methods;
3679                         this.container = nsContainer;
3680                         this.index = lookupIndex;
3681                 }
3682
3683                 public NamespaceContainer Container {
3684                         get {
3685                                 return container;
3686                         }
3687                 }
3688
3689                 public IMemberContext Context {
3690                         get {
3691                                 return context;
3692                         }
3693                 }
3694
3695                 public int LookupIndex {
3696                         get {
3697                                 return index;
3698                         }
3699                 }
3700
3701                 public IList<MethodSpec> Methods {
3702                         get {
3703                                 return methods;
3704                         }
3705                 }
3706         }
3707
3708         //
3709         // Represents a group of extension method candidates for whole namespace
3710         //
3711         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3712         {
3713                 ExtensionMethodCandidates candidates;
3714                 public Expression ExtensionExpression;
3715
3716                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3717                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3718                 {
3719                         this.candidates = candidates;
3720                         this.ExtensionExpression = extensionExpr;
3721                 }
3722
3723                 public override bool IsStatic {
3724                         get { return true; }
3725                 }
3726
3727                 //
3728                 // For extension methodgroup we are not looking for base members but parent
3729                 // namespace extension methods
3730                 //
3731                 public override IList<MemberSpec> GetBaseMembers (TypeSpec type)
3732                 {
3733                         // TODO: candidates are null only when doing error reporting, that's
3734                         // incorrect. We have to discover same extension methods in error mode
3735                         if (candidates == null)
3736                                 return null;
3737
3738                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3739
3740                         candidates = candidates.Container.LookupExtensionMethod (candidates.Context, Name, arity, candidates.LookupIndex);
3741                         if (candidates == null)
3742                                 return null;
3743
3744                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3745                 }
3746
3747                 public static bool IsExtensionTypeCompatible (TypeSpec argType, TypeSpec extensionType)
3748                 {
3749                         //
3750                         // Indentity, implicit reference or boxing conversion must exist for the extension parameter
3751                         //
3752                         // LAMESPEC: or implicit type parameter conversion
3753                         //
3754                         return argType == extensionType ||
3755                                 TypeSpecComparer.IsEqual (argType, extensionType) ||
3756                                 Convert.ImplicitReferenceConversionExists (argType, extensionType, false) ||
3757                                 Convert.ImplicitBoxingConversion (null, argType, extensionType) != null;
3758                 }
3759
3760                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
3761                 {
3762                         rc.Report.Error (8093, expr.Location, "An argument to nameof operator cannot be extension method group");
3763                 }
3764
3765                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3766                 {
3767                         // We are already here
3768                         return null;
3769                 }
3770
3771                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3772                 {
3773                         if (arguments == null)
3774                                 arguments = new Arguments (1);
3775
3776                         ExtensionExpression = ExtensionExpression.Resolve (ec);
3777                         if (ExtensionExpression == null)
3778                                 return null;
3779
3780                         var cand = candidates;
3781                         var atype = ConditionalAccess ? Argument.AType.ExtensionTypeConditionalAccess : Argument.AType.ExtensionType;
3782                         arguments.Insert (0, new Argument (ExtensionExpression, atype));
3783                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3784
3785                         // Restore candidates in case we are running in probing mode
3786                         candidates = cand;
3787
3788                         // Store resolved argument and restore original arguments
3789                         if (res == null) {
3790                                 // Clean-up modified arguments for error reporting
3791                                 arguments.RemoveAt (0);
3792                                 return null;
3793                         }
3794
3795                         var me = ExtensionExpression as MemberExpr;
3796                         if (me != null) {
3797                                 me.ResolveInstanceExpression (ec, null);
3798                                 var fe = me as FieldExpr;
3799                                 if (fe != null)
3800                                         fe.Spec.MemberDefinition.SetIsUsed ();
3801                         }
3802
3803                         InstanceExpression = null;
3804                         return this;
3805                 }
3806
3807                 #region IErrorHandler Members
3808
3809                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3810                 {
3811                         return false;
3812                 }
3813
3814                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3815                 {
3816                         rc.Report.SymbolRelatedToPreviousError (best);
3817
3818                         if (index == 0) {
3819                                 rc.Report.Error (1929, loc,
3820                                         "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' requires an instance of type `{3}'",
3821                                         queried_type.GetSignatureForError (), Name, best.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3822                         } else {
3823                                 rc.Report.Error (1928, loc,
3824                                         "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3825                                         queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3826                         }
3827
3828                         return true;
3829                 }
3830
3831                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3832                 {
3833                         return false;
3834                 }
3835
3836                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3837                 {
3838                         return false;
3839                 }
3840
3841                 #endregion
3842         }
3843
3844         /// <summary>
3845         ///   MethodGroupExpr represents a group of method candidates which
3846         ///   can be resolved to the best method overload
3847         /// </summary>
3848         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3849         {
3850                 static readonly MemberSpec[] Excluded = new MemberSpec[0];
3851
3852                 protected IList<MemberSpec> Methods;
3853                 MethodSpec best_candidate;
3854                 TypeSpec best_candidate_return;
3855                 protected TypeArguments type_arguments;
3856
3857                 SimpleName simple_name;
3858                 protected TypeSpec queried_type;
3859
3860                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3861                 {
3862                         Methods = mi;
3863                         this.loc = loc;
3864                         this.type = InternalType.MethodGroup;
3865
3866                         eclass = ExprClass.MethodGroup;
3867                         queried_type = type;
3868                 }
3869
3870                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3871                         : this (new MemberSpec[] { m }, type, loc)
3872                 {
3873                 }
3874
3875                 #region Properties
3876
3877                 public MethodSpec BestCandidate {
3878                         get {
3879                                 return best_candidate;
3880                         }
3881                 }
3882
3883                 public TypeSpec BestCandidateReturnType {
3884                         get {
3885                                 return best_candidate_return;
3886                         }
3887                 }
3888
3889                 public IList<MemberSpec> Candidates {
3890                         get {
3891                                 return Methods;
3892                         }
3893                 }
3894
3895                 protected override TypeSpec DeclaringType {
3896                         get {
3897                                 return queried_type;
3898                         }
3899                 }
3900
3901                 public bool IsConditionallyExcluded {
3902                         get {
3903                                 return Methods == Excluded;
3904                         }
3905                 }
3906
3907                 public override bool IsInstance {
3908                         get {
3909                                 if (best_candidate != null)
3910                                         return !best_candidate.IsStatic;
3911
3912                                 return false;
3913                         }
3914                 }
3915
3916                 public override bool IsSideEffectFree {
3917                         get {
3918                                 return InstanceExpression == null || InstanceExpression.IsSideEffectFree;
3919                         }
3920                 }
3921
3922                 public override bool IsStatic {
3923                         get {
3924                                 if (best_candidate != null)
3925                                         return best_candidate.IsStatic;
3926
3927                                 return false;
3928                         }
3929                 }
3930
3931                 public override string KindName {
3932                         get { return "method"; }
3933                 }
3934
3935                 public override string Name {
3936                         get {
3937                                 if (best_candidate != null)
3938                                         return best_candidate.Name;
3939
3940                                 // TODO: throw ?
3941                                 return Methods.First ().Name;
3942                         }
3943                 }
3944
3945                 #endregion
3946
3947                 //
3948                 // When best candidate is already know this factory can be used
3949                 // to avoid expensive overload resolution to be called
3950                 //
3951                 // NOTE: InstanceExpression has to be set manually
3952                 //
3953                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3954                 {
3955                         return new MethodGroupExpr (best, queriedType, loc) {
3956                                 best_candidate = best,
3957                                 best_candidate_return = best.ReturnType
3958                         };
3959                 }
3960
3961                 public override string GetSignatureForError ()
3962                 {
3963                         if (best_candidate != null)
3964                                 return best_candidate.GetSignatureForError ();
3965
3966                         return Methods.First ().GetSignatureForError ();
3967                 }
3968
3969                 public override Expression CreateExpressionTree (ResolveContext ec)
3970                 {
3971                         if (best_candidate == null) {
3972                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3973                                 return null;
3974                         }
3975
3976                         if (IsConditionallyExcluded)
3977                                 ec.Report.Error (765, loc,
3978                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3979
3980                         if (ConditionalAccess)
3981                                 Error_NullShortCircuitInsideExpressionTree (ec);
3982
3983                         return new TypeOfMethod (best_candidate, loc);
3984                 }
3985
3986                 protected override Expression DoResolve (ResolveContext ec)
3987                 {
3988                         this.eclass = ExprClass.MethodGroup;
3989
3990                         if (InstanceExpression != null) {
3991                                 InstanceExpression = InstanceExpression.Resolve (ec);
3992                                 if (InstanceExpression == null)
3993                                         return null;
3994                         }
3995
3996                         return this;
3997                 }
3998
3999                 public override void Emit (EmitContext ec)
4000                 {
4001                         throw new NotSupportedException ();
4002                 }
4003
4004                 public void EmitCall (EmitContext ec, Arguments arguments, bool statement)
4005                 {
4006                         var call = new CallEmitter ();
4007                         call.InstanceExpression = InstanceExpression;
4008                         call.ConditionalAccess = ConditionalAccess;
4009
4010                         if (statement)
4011                                 call.EmitStatement (ec, best_candidate, arguments, loc);
4012                         else
4013                                 call.Emit (ec, best_candidate, arguments, loc);
4014                 }
4015
4016                 public void EmitCall (EmitContext ec, Arguments arguments, TypeSpec conditionalAccessReceiver, bool statement)
4017                 {
4018                         var ca = ec.ConditionalAccess;
4019                         ec.ConditionalAccess = new ConditionalAccessContext (conditionalAccessReceiver, ec.DefineLabel ()) {
4020                                 Statement = statement
4021                         };
4022
4023                         EmitCall (ec, arguments, statement);
4024
4025                         ec.CloseConditionalAccess (!statement && best_candidate_return != conditionalAccessReceiver && conditionalAccessReceiver.IsNullableType ? conditionalAccessReceiver : null);
4026                         ec.ConditionalAccess = ca;
4027                 }
4028
4029                 public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
4030                 {
4031                         if (target != InternalType.ErrorType) {
4032                                 ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
4033                                         Name, target.GetSignatureForError ());
4034                         }
4035                 }
4036
4037                 public bool HasAccessibleCandidate (ResolveContext rc)
4038                 {
4039                         foreach (var candidate in Candidates) {
4040                                 if (candidate.IsAccessible (rc))
4041                                         return true;
4042                         }
4043
4044                         return false;
4045                 }
4046
4047                 public static bool IsExtensionMethodArgument (Expression expr)
4048                 {
4049                         //
4050                         // LAMESPEC: No details about which expressions are not allowed
4051                         //
4052                         return !(expr is TypeExpr) && !(expr is BaseThis);
4053                 }
4054
4055                 /// <summary>
4056                 ///   Find the Applicable Function Members (7.4.2.1)
4057                 ///
4058                 ///   me: Method Group expression with the members to select.
4059                 ///       it might contain constructors or methods (or anything
4060                 ///       that maps to a method).
4061                 ///
4062                 ///   Arguments: ArrayList containing resolved Argument objects.
4063                 ///
4064                 ///   loc: The location if we want an error to be reported, or a Null
4065                 ///        location for "probing" purposes.
4066                 ///
4067                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
4068                 ///            that is the best match of me on Arguments.
4069                 ///
4070                 /// </summary>
4071                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
4072                 {
4073                         // TODO: causes issues with probing mode, remove explicit Kind check
4074                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
4075                                 return this;
4076
4077                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
4078                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
4079                                 r.BaseMembersProvider = this;
4080                                 r.InstanceQualifier = this;
4081                         }
4082
4083                         if (cerrors != null)
4084                                 r.CustomErrors = cerrors;
4085
4086                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
4087                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
4088                         if (best_candidate == null) {
4089                                 if (!r.BestCandidateIsDynamic)
4090                                         return null;
4091
4092                                 if (simple_name != null && ec.IsStatic)
4093                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
4094
4095                                 return this;
4096                         }
4097
4098                         // Overload resolver had to create a new method group, all checks bellow have already been executed
4099                         if (r.BestCandidateNewMethodGroup != null)
4100                                 return r.BestCandidateNewMethodGroup;
4101
4102                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
4103                                 if (InstanceExpression != null) {
4104                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
4105                                                 InstanceExpression = null;
4106                                         } else {
4107                                                 if (simple_name != null && best_candidate.IsStatic) {
4108                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
4109                                                 }
4110
4111                                                 InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup | ResolveFlags.Type);
4112                                         }
4113                                 }
4114
4115                                 ResolveInstanceExpression (ec, null);
4116                         }
4117
4118                         var base_override = CandidateToBaseOverride (ec, best_candidate);
4119                         if (base_override == best_candidate) {
4120                                 best_candidate_return = r.BestCandidateReturnType;
4121                         } else {
4122                                 best_candidate = base_override;
4123                                 best_candidate_return = best_candidate.ReturnType;
4124                         }
4125
4126                         if (best_candidate.IsGeneric && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0 && TypeParameterSpec.HasAnyTypeParameterConstrained (best_candidate.GenericDefinition)) {
4127                                 ConstraintChecker cc = new ConstraintChecker (ec);
4128                                 cc.CheckAll (best_candidate.GetGenericMethodDefinition (), best_candidate.TypeArguments, best_candidate.Constraints, loc);
4129                         }
4130
4131                         //
4132                         // Additional check for possible imported base override method which
4133                         // could not be done during IsOverrideMethodBaseTypeAccessible
4134                         //
4135                         if (best_candidate.IsVirtual && (best_candidate.DeclaringType.Modifiers & Modifiers.PROTECTED) != 0 &&
4136                                 best_candidate.MemberDefinition.IsImported && !best_candidate.DeclaringType.IsAccessible (ec)) {
4137                                 ec.Report.SymbolRelatedToPreviousError (best_candidate);
4138                                 ErrorIsInaccesible (ec, best_candidate.GetSignatureForError (), loc);
4139                         }
4140
4141                         // Speed up the check by not doing it on disallowed targets
4142                         if (best_candidate_return.Kind == MemberKind.Void && best_candidate.IsConditionallyExcluded (ec))
4143                                 Methods = Excluded;
4144
4145                         return this;
4146                 }
4147
4148                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
4149                 {
4150                         var fe = left as FieldExpr;
4151                         if (fe != null) {
4152                                 //
4153                                 // Using method-group on struct fields makes the struct assigned. I am not sure
4154                                 // why but that's what .net does
4155                                 //
4156                                 fe.Spec.MemberDefinition.SetIsAssigned ();
4157                         }
4158
4159                         simple_name = original;
4160                         return base.ResolveMemberAccess (ec, left, original);
4161                 }
4162
4163                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
4164                 {
4165                         if (!HasAccessibleCandidate (rc)) {
4166                                 ErrorIsInaccesible (rc, expr.GetSignatureForError (), loc);
4167                         }
4168
4169                         if (expr.HasTypeArguments) {
4170                                 rc.Report.Error (8084, expr.Location, "An argument to nameof operator cannot be method group with type arguments");
4171                         }
4172                 }
4173
4174                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
4175                 {
4176                         type_arguments = ta;
4177                 }
4178
4179                 #region IBaseMembersProvider Members
4180
4181                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec type)
4182                 {
4183                         var baseType = type.BaseType;
4184
4185                         IList<MemberSpec> members = baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
4186
4187                         if (members == null && !type.IsInterface) {
4188                                 var tps = queried_type as TypeParameterSpec;
4189                                 if (tps != null)
4190                                         members = MemberCache.FindInterfaceMembers (tps, Methods [0].Name);
4191                         }
4192
4193                         return members;
4194                 }
4195
4196                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
4197                 {
4198                         if (queried_type == member.DeclaringType)
4199                                 return null;
4200
4201                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
4202                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
4203                 }
4204
4205                 //
4206                 // Extension methods lookup after ordinary methods candidates failed to apply
4207                 //
4208                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
4209                 {
4210                         if (InstanceExpression == null || InstanceExpression.eclass == ExprClass.Type)
4211                                 return null;
4212
4213                         if (!IsExtensionMethodArgument (InstanceExpression))
4214                                 return null;
4215
4216                         int arity = type_arguments == null ? 0 : type_arguments.Count;
4217                         var methods = rc.LookupExtensionMethod (Methods[0].Name, arity);
4218                         if (methods == null)
4219                                 return null;
4220
4221                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
4222                         emg.SetTypeArguments (rc, type_arguments);
4223                         emg.ConditionalAccess = ConditionalAccess;
4224                         return emg;
4225                 }
4226
4227                 #endregion
4228         }
4229
4230         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
4231         {
4232                 public ConstructorInstanceQualifier (TypeSpec type)
4233                         : this ()
4234                 {
4235                         InstanceType = type;
4236                 }
4237
4238                 public TypeSpec InstanceType { get; private set; }
4239
4240                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
4241                 {
4242                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
4243                 }
4244         }
4245
4246         public struct OverloadResolver
4247         {
4248                 [Flags]
4249                 public enum Restrictions
4250                 {
4251                         None = 0,
4252                         DelegateInvoke = 1,
4253                         ProbingOnly     = 1 << 1,
4254                         CovariantDelegate = 1 << 2,
4255                         NoBaseMembers = 1 << 3,
4256                         BaseMembersIncluded = 1 << 4,
4257                         GetEnumeratorLookup = 1 << 5
4258                 }
4259
4260                 public interface IBaseMembersProvider
4261                 {
4262                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
4263                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
4264                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
4265                 }
4266
4267                 public interface IErrorHandler
4268                 {
4269                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
4270                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
4271                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
4272                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
4273                 }
4274
4275                 public interface IInstanceQualifier
4276                 {
4277                         TypeSpec InstanceType { get; }
4278                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
4279                 }
4280
4281                 sealed class NoBaseMembers : IBaseMembersProvider
4282                 {
4283                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
4284
4285                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
4286                         {
4287                                 return null;
4288                         }
4289
4290                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
4291                         {
4292                                 return null;
4293                         }
4294
4295                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
4296                         {
4297                                 return null;
4298                         }
4299                 }
4300
4301                 struct AmbiguousCandidate
4302                 {
4303                         public readonly MemberSpec Member;
4304                         public readonly bool Expanded;
4305                         public readonly AParametersCollection Parameters;
4306
4307                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
4308                         {
4309                                 Member = member;
4310                                 Parameters = parameters;
4311                                 Expanded = expanded;
4312                         }
4313                 }
4314
4315                 Location loc;
4316                 IList<MemberSpec> members;
4317                 TypeArguments type_arguments;
4318                 IBaseMembersProvider base_provider;
4319                 IErrorHandler custom_errors;
4320                 IInstanceQualifier instance_qualifier;
4321                 Restrictions restrictions;
4322                 MethodGroupExpr best_candidate_extension_group;
4323                 TypeSpec best_candidate_return_type;
4324
4325                 SessionReportPrinter lambda_conv_msgs;
4326
4327                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
4328                         : this (members, null, restrictions, loc)
4329                 {
4330                 }
4331
4332                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
4333                         : this ()
4334                 {
4335                         if (members == null || members.Count == 0)
4336                                 throw new ArgumentException ("empty members set");
4337
4338                         this.members = members;
4339                         this.loc = loc;
4340                         type_arguments = targs;
4341                         this.restrictions = restrictions;
4342                         if (IsDelegateInvoke)
4343                                 this.restrictions |= Restrictions.NoBaseMembers;
4344
4345                         base_provider = NoBaseMembers.Instance;
4346                 }
4347
4348                 #region Properties
4349
4350                 public IBaseMembersProvider BaseMembersProvider {
4351                         get {
4352                                 return base_provider;
4353                         }
4354                         set {
4355                                 base_provider = value;
4356                         }
4357                 }
4358
4359                 public bool BestCandidateIsDynamic { get; set; }
4360
4361                 //
4362                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
4363                 //
4364                 public MethodGroupExpr BestCandidateNewMethodGroup {
4365                         get {
4366                                 return best_candidate_extension_group;
4367                         }
4368                 }
4369
4370                 //
4371                 // Return type can be different between best candidate and closest override
4372                 //
4373                 public TypeSpec BestCandidateReturnType {
4374                         get {
4375                                 return best_candidate_return_type;
4376                         }
4377                 }
4378
4379                 public IErrorHandler CustomErrors {
4380                         get {
4381                                 return custom_errors;
4382                         }
4383                         set {
4384                                 custom_errors = value;
4385                         }
4386                 }
4387
4388                 TypeSpec DelegateType {
4389                         get {
4390                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
4391                                         throw new InternalErrorException ("Not running in delegate mode", loc);
4392
4393                                 return members [0].DeclaringType;
4394                         }
4395                 }
4396
4397                 public IInstanceQualifier InstanceQualifier {
4398                         get {
4399                                 return instance_qualifier;
4400                         }
4401                         set {
4402                                 instance_qualifier = value;
4403                         }
4404                 }
4405
4406                 bool IsProbingOnly {
4407                         get {
4408                                 return (restrictions & Restrictions.ProbingOnly) != 0;
4409                         }
4410                 }
4411
4412                 bool IsDelegateInvoke {
4413                         get {
4414                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
4415                         }
4416                 }
4417
4418                 #endregion
4419
4420                 //
4421                 //  7.4.3.3  Better conversion from expression
4422                 //  Returns :   1    if a->p is better,
4423                 //              2    if a->q is better,
4424                 //              0 if neither is better
4425                 //
4426                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
4427                 {
4428                         TypeSpec argument_type = a.Type;
4429
4430                         //
4431                         // Exactly matching Expression phase
4432                         //
4433
4434                         //
4435                         // If argument is an anonymous function
4436                         //
4437                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
4438                                 //
4439                                 // p and q are delegate types or expression tree types
4440                                 //
4441                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
4442                                         if (q.MemberDefinition != p.MemberDefinition) {
4443                                                 return 0;
4444                                         }
4445
4446                                         //
4447                                         // Uwrap delegate from Expression<T>
4448                                         //
4449                                         q = TypeManager.GetTypeArguments (q) [0];
4450                                         p = TypeManager.GetTypeArguments (p) [0];
4451                                 }
4452
4453                                 var p_m = Delegate.GetInvokeMethod (p);
4454                                 var q_m = Delegate.GetInvokeMethod (q);
4455
4456                                 //
4457                                 // With identical parameter lists
4458                                 //
4459                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
4460                                         return 0;
4461
4462                                 p = p_m.ReturnType;
4463                                 var orig_q = q;
4464                                 q = q_m.ReturnType;
4465
4466                                 //
4467                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4468                                 //
4469                                 if (p.Kind == MemberKind.Void) {
4470                                         return q.Kind != MemberKind.Void ? 2 : 0;
4471                                 }
4472
4473                                 //
4474                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4475                                 //
4476                                 if (q.Kind == MemberKind.Void) {
4477                                         return p.Kind != MemberKind.Void ? 1 : 0;
4478                                 }
4479
4480                                 var am = (AnonymousMethodExpression)a.Expr;
4481
4482                                 //
4483                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
4484                                 // better conversion is performed between underlying types Y1 and Y2
4485                                 //
4486                                 if (p.IsGenericTask || q.IsGenericTask) {
4487                                         if (am.Block.IsAsync && p.IsGenericTask && q.IsGenericTask) {
4488                                                 q = q.TypeArguments [0];
4489                                                 p = p.TypeArguments [0];
4490                                         }
4491                                 }
4492
4493                                 if (q != p) {
4494                                         //
4495                                         // An inferred return type X exists for E in the context of the parameter list, and
4496                                         // an identity conversion exists from X to the return type of D
4497                                         //
4498                                         var inferred_type = am.InferReturnType (ec, null, orig_q);
4499                                         if (inferred_type != null) {
4500                                                 if (inferred_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4501                                                         inferred_type = ec.BuiltinTypes.Object;
4502
4503                                                 if (inferred_type == p)
4504                                                         return 1;
4505
4506                                                 if (inferred_type == q)
4507                                                         return 2;
4508                                         }
4509                                 }
4510                         }
4511
4512                         if (argument_type == p)
4513                                 return 1;
4514
4515                         if (argument_type == q)
4516                                 return 2;
4517
4518                         return IsBetterConversionTarget (ec, p, q);
4519                 }
4520
4521                 static int IsBetterConversionTarget (ResolveContext rc, TypeSpec p, TypeSpec q)
4522                 {
4523                         if ((p.Kind == MemberKind.Delegate || p.IsExpressionTreeType) && (q.Kind == MemberKind.Delegate || q.IsExpressionTreeType)) {
4524
4525                                 if (p.Kind != MemberKind.Delegate) {
4526                                         p = TypeManager.GetTypeArguments (p) [0];
4527                                 }
4528
4529                                 if (q.Kind != MemberKind.Delegate) {
4530                                         q = TypeManager.GetTypeArguments (q) [0];
4531                                 }
4532
4533                                 var p_m = Delegate.GetInvokeMethod (p);
4534                                 var q_m = Delegate.GetInvokeMethod (q);
4535
4536                                 p = p_m.ReturnType;
4537                                 q = q_m.ReturnType;
4538
4539                                 //
4540                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4541                                 //
4542                                 if (p.Kind == MemberKind.Void) {
4543                                         return q.Kind != MemberKind.Void ? 2 : 0;
4544                                 }
4545
4546                                 //
4547                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4548                                 //
4549                                 if (q.Kind == MemberKind.Void) {
4550                                         return p.Kind != MemberKind.Void ? 1 : 0;
4551                                 }
4552
4553                                 return IsBetterConversionTarget (rc, p, q);
4554                         }
4555
4556                         if (p.IsGenericTask && q.IsGenericTask) {
4557                                 q = q.TypeArguments [0];
4558                                 p = p.TypeArguments [0];
4559                                 return IsBetterConversionTarget (rc, p, q);
4560                         }
4561
4562                         var p_orig = p;
4563                         if (p.IsNullableType) {
4564                                 p = Nullable.NullableInfo.GetUnderlyingType (p);
4565                                 if (!BuiltinTypeSpec.IsPrimitiveTypeOrDecimal (p))
4566                                         return BetterTypeConversionImplicitConversion (rc, p_orig, q);
4567
4568                                 //
4569                                 // Spec expects implicit conversion check between p and q, q and p
4570                                 // to be done before nullable unwrapping but that's expensive operation.
4571                                 //
4572                                 // Extra manual tweak is needed because BetterTypeConversion works on
4573                                 // unwrapped types
4574                                 //
4575                                 if (p == q)
4576                                         return 2;
4577                         }
4578
4579                         var q_orig = q;
4580                         if (q.IsNullableType) {
4581                                 q = Nullable.NullableInfo.GetUnderlyingType (q);
4582                                 if (!BuiltinTypeSpec.IsPrimitiveTypeOrDecimal (q))
4583                                         return BetterTypeConversionImplicitConversion (rc, p_orig, q_orig);
4584
4585                                 if (q == p)
4586                                         return 1;
4587                         }
4588
4589                         return BetterTypeConversion (rc, p, q);
4590                 }
4591
4592                 //
4593                 // 7.4.3.4  Better conversion from type
4594                 //
4595                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
4596                 {
4597                         if (p == null || q == null)
4598                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
4599
4600                         switch (p.BuiltinType) {
4601                         case BuiltinTypeSpec.Type.Int:
4602                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4603                                         return 1;
4604                                 break;
4605                         case BuiltinTypeSpec.Type.Long:
4606                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4607                                         return 1;
4608                                 break;
4609                         case BuiltinTypeSpec.Type.SByte:
4610                                 switch (q.BuiltinType) {
4611                                 case BuiltinTypeSpec.Type.Byte:
4612                                 case BuiltinTypeSpec.Type.UShort:
4613                                 case BuiltinTypeSpec.Type.UInt:
4614                                 case BuiltinTypeSpec.Type.ULong:
4615                                         return 1;
4616                                 }
4617                                 break;
4618                         case BuiltinTypeSpec.Type.Short:
4619                                 switch (q.BuiltinType) {
4620                                 case BuiltinTypeSpec.Type.UShort:
4621                                 case BuiltinTypeSpec.Type.UInt:
4622                                 case BuiltinTypeSpec.Type.ULong:
4623                                         return 1;
4624                                 }
4625                                 break;
4626                         case BuiltinTypeSpec.Type.Dynamic:
4627                                 // LAMESPEC: Dynamic conversions is not considered
4628                                 p = ec.Module.Compiler.BuiltinTypes.Object;
4629                                 break;
4630                         }
4631
4632                         switch (q.BuiltinType) {
4633                         case BuiltinTypeSpec.Type.Int:
4634                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4635                                         return 2;
4636                                 break;
4637                         case BuiltinTypeSpec.Type.Long:
4638                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4639                                         return 2;
4640                                 break;
4641                         case BuiltinTypeSpec.Type.SByte:
4642                                 switch (p.BuiltinType) {
4643                                 case BuiltinTypeSpec.Type.Byte:
4644                                 case BuiltinTypeSpec.Type.UShort:
4645                                 case BuiltinTypeSpec.Type.UInt:
4646                                 case BuiltinTypeSpec.Type.ULong:
4647                                         return 2;
4648                                 }
4649                                 break;
4650                         case BuiltinTypeSpec.Type.Short:
4651                                 switch (p.BuiltinType) {
4652                                 case BuiltinTypeSpec.Type.UShort:
4653                                 case BuiltinTypeSpec.Type.UInt:
4654                                 case BuiltinTypeSpec.Type.ULong:
4655                                         return 2;
4656                                 }
4657                                 break;
4658                         case BuiltinTypeSpec.Type.Dynamic:
4659                                 // LAMESPEC: Dynamic conversions is not considered
4660                                 q = ec.Module.Compiler.BuiltinTypes.Object;
4661                                 break;
4662                         }
4663
4664                         return BetterTypeConversionImplicitConversion (ec, p, q);
4665                 }
4666
4667                 static int BetterTypeConversionImplicitConversion (ResolveContext rc, TypeSpec p, TypeSpec q)
4668                 {
4669                         // TODO: this is expensive
4670                         Expression p_tmp = new EmptyExpression (p);
4671                         Expression q_tmp = new EmptyExpression (q);
4672
4673                         bool p_to_q = Convert.ImplicitConversionExists (rc, p_tmp, q);
4674                         bool q_to_p = Convert.ImplicitConversionExists (rc, q_tmp, p);
4675
4676                         if (p_to_q && !q_to_p)
4677                                 return 1;
4678
4679                         if (q_to_p && !p_to_q)
4680                                 return 2;
4681
4682                         return 0;
4683                 }
4684
4685                 /// <summary>
4686                 ///   Determines "Better function" between candidate
4687                 ///   and the current best match
4688                 /// </summary>
4689                 /// <remarks>
4690                 ///    Returns a boolean indicating :
4691                 ///     false if candidate ain't better
4692                 ///     true  if candidate is better than the current best match
4693                 /// </remarks>
4694                 bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
4695                         MemberSpec best, AParametersCollection bparam, bool best_params)
4696                 {
4697                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
4698                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
4699
4700                         int candidate_better_count = 0;
4701                         int best_better_count = 0;
4702
4703                         bool are_equivalent = true;
4704                         int args_count = args == null ? 0 : args.Count;
4705                         int j = 0;
4706                         Argument a = null;
4707                         TypeSpec ct, bt;
4708                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
4709                                 a = args[j];
4710
4711                                 // Default arguments are ignored for better decision
4712                                 if (a.IsDefaultArgument)
4713                                         break;
4714
4715                                 //
4716                                 // When comparing named argument the parameter type index has to be looked up
4717                                 // in original parameter set (override version for virtual members)
4718                                 //
4719                                 NamedArgument na = a as NamedArgument;
4720                                 if (na != null) {
4721                                         int idx = cparam.GetParameterIndexByName (na.Name);
4722                                         ct = candidate_pd.Types[idx];
4723                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4724                                                 ct = TypeManager.GetElementType (ct);
4725
4726                                         idx = bparam.GetParameterIndexByName (na.Name);
4727                                         bt = best_pd.Types[idx];
4728                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4729                                                 bt = TypeManager.GetElementType (bt);
4730                                 } else {
4731                                         ct = candidate_pd.Types[c_idx];
4732                                         bt = best_pd.Types[b_idx];
4733
4734                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
4735                                                 ct = TypeManager.GetElementType (ct);
4736                                                 --c_idx;
4737                                         }
4738
4739                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
4740                                                 bt = TypeManager.GetElementType (bt);
4741                                                 --b_idx;
4742                                         }
4743                                 }
4744
4745                                 if (TypeSpecComparer.IsEqual (ct, bt))
4746                                         continue;
4747
4748                                 are_equivalent = false;
4749                                 int result = BetterExpressionConversion (ec, a, ct, bt);
4750
4751                                 // for each argument, the conversion to 'ct' should be no worse than
4752                                 // the conversion to 'bt'.
4753                                 if (result == 2) {
4754                                         //
4755                                         // No optional parameters tie breaking rules for delegates overload resolution
4756                                         //
4757                                         if ((restrictions & Restrictions.CovariantDelegate) != 0)
4758                                                 return false;
4759
4760                                         ++best_better_count;
4761                                         continue;
4762                                 }
4763
4764                                 // for at least one argument, the conversion to 'ct' should be better than
4765                                 // the conversion to 'bt'.
4766                                 if (result != 0)
4767                                         ++candidate_better_count;
4768                         }
4769
4770                         if (candidate_better_count != 0 && best_better_count == 0)
4771                                 return true;
4772
4773                         if (best_better_count > 0 && candidate_better_count == 0)
4774                                 return false;
4775
4776                         //
4777                         // LAMESPEC: Tie-breaking rules for not equivalent parameter types
4778                         //
4779                         if (!are_equivalent) {
4780                                 while (j < args_count && !args [j++].IsDefaultArgument) ;
4781
4782                                 //
4783                                 // A candidate with no default parameters is still better when there
4784                                 // is no better expression conversion
4785                                 //
4786                                 if (candidate_pd.Count < best_pd.Count) {
4787                                         if (!candidate_params && !candidate_pd.FixedParameters [j - j].HasDefaultValue) {
4788                                                 return true;
4789                                         }
4790                                 } else if (candidate_pd.Count == best_pd.Count) {
4791                                         if (candidate_params)
4792                                                 return false;
4793
4794                                         if (!candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.FixedParameters [j - 1].HasDefaultValue)
4795                                                 return true;
4796
4797                                         if (candidate_pd.FixedParameters [j - 1].HasDefaultValue && best_pd.HasParams)
4798                                                 return true;
4799                                 }
4800
4801                                 return false;
4802                         }
4803
4804                         //
4805                         // If candidate is applicable in its normal form and best has a params array and is applicable
4806                         // only in its expanded form, then candidate is better
4807                         //
4808                         if (candidate_params != best_params)
4809                                 return !candidate_params;
4810
4811                         //
4812                         // We have not reached end of parameters list due to params or used default parameters
4813                         //
4814                         bool defaults_ambiguity = false;
4815                         while (j < candidate_pd.Count && j < best_pd.Count) {
4816                                 var cand_param = candidate_pd.FixedParameters [j];
4817                                 var best_param = best_pd.FixedParameters [j];
4818
4819                                 if (cand_param.HasDefaultValue != best_param.HasDefaultValue && (!candidate_pd.HasParams || !best_pd.HasParams))
4820                                         return cand_param.HasDefaultValue;
4821
4822                                 defaults_ambiguity = true;
4823                                 if (candidate_pd.Count == best_pd.Count) {
4824                                         //
4825                                         // LAMESPEC:
4826                                         //
4827                                         // void Foo (int i = 0) is better than void Foo (params int[]) for Foo ()
4828                                         // void Foo (string[] s, string value = null) is better than Foo (string s, params string[]) for Foo (null) or Foo ()
4829                                         //
4830                                         if (cand_param.HasDefaultValue) {
4831                                                 ++j;
4832                                                 continue;
4833                                         }
4834
4835                                         break;
4836                                 }
4837
4838                                 //
4839                                 // Neither is better when not all arguments are provided
4840                                 //
4841                                 // void Foo (string s, int i = 0) <-> Foo (string s, int i = 0, int i2 = 0)
4842                                 // void Foo (string s, int i = 0) <-> Foo (string s, byte i = 0)
4843                                 // void Foo (string s, params int[]) <-> Foo (string s, params byte[])
4844                                 //
4845                                 ++j;
4846                         }
4847
4848                         if (candidate_pd.Count != best_pd.Count) {
4849                                 if (defaults_ambiguity && best_pd.Count - 1 == j)
4850                                         return best_pd.HasParams;
4851
4852                                 return candidate_pd.Count < best_pd.Count;
4853                         }
4854
4855                         //
4856                         // One is a non-generic method and second is a generic method, then non-generic is better
4857                         //
4858                         if (best.IsGeneric != candidate.IsGeneric)
4859                                 return best.IsGeneric;
4860
4861                         //
4862                         // Both methods have the same number of parameters, and the parameters have equal types
4863                         // Pick the "more specific" signature using rules over original (non-inflated) types
4864                         //
4865                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
4866                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
4867
4868                         bool specific_at_least_once = false;
4869                         for (j = 0; j < args_count; ++j) {
4870                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
4871                                 if (na != null) {
4872                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
4873                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
4874                                 } else {
4875                                         ct = candidate_def_pd.Types[j];
4876                                         bt = best_def_pd.Types[j];
4877                                 }
4878
4879                                 if (ct == bt)
4880                                         continue;
4881                                 TypeSpec specific = MoreSpecific (ct, bt);
4882                                 if (specific == bt)
4883                                         return false;
4884                                 if (specific == ct)
4885                                         specific_at_least_once = true;
4886                         }
4887
4888                         if (specific_at_least_once)
4889                                 return true;
4890
4891                         return false;
4892                 }
4893
4894                 static bool CheckInflatedArguments (MethodSpec ms)
4895                 {
4896                         if (!TypeParameterSpec.HasAnyTypeParameterTypeConstrained (ms.GenericDefinition))
4897                                 return true;
4898
4899                         // Setup constraint checker for probing only
4900                         ConstraintChecker cc = new ConstraintChecker (null);
4901
4902                         var mp = ms.Parameters.Types;
4903                         for (int i = 0; i < mp.Length; ++i) {
4904                                 var type = mp[i] as InflatedTypeSpec;
4905                                 if (type == null)
4906                                         continue;
4907
4908                                 var targs = type.TypeArguments;
4909                                 if (targs.Length == 0)
4910                                         continue;
4911
4912                                 // TODO: Checking inflated MVAR arguments should be enough
4913                                 if (!cc.CheckAll (type.GetDefinition (), targs, type.Constraints, Location.Null))
4914                                         return false;
4915                         }
4916
4917                         return true;
4918                 }
4919
4920                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4921                 {
4922                         rc.Report.Error (1729, loc,
4923                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4924                                 type.GetSignatureForError (), argCount.ToString ());
4925                 }
4926
4927                 //
4928                 // Determines if the candidate method is applicable to the given set of arguments
4929                 // There could be two different set of parameters for same candidate where one
4930                 // is the closest override for default values and named arguments checks and second
4931                 // one being the virtual base for the parameter types and modifiers.
4932                 //
4933                 // A return value rates candidate method compatibility,
4934                 // -1 = fatal error
4935                 // 0 = the best, int.MaxValue = the worst
4936                 //
4937                 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)
4938                 {
4939                         //
4940                         // Each step has allocated 10 values, it can overflow for
4941                         // more than 10 arguments but that's ok as it's used for
4942                         // better error reporting only
4943                         //
4944                         const int ArgumentCountMismatch         = 1000000000;
4945                         const int NamedArgumentsMismatch        = 100000000;
4946                         const int DefaultArgumentMismatch       = 10000000;
4947                         const int UnexpectedTypeArguments       = 1000000;
4948                         const int TypeArgumentsMismatch         = 100000;
4949                         const int InflatedTypesMismatch         = 10000;
4950
4951                         // Parameters of most-derived type used mainly for named and optional parameters
4952                         var pd = pm.Parameters;
4953
4954                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4955                         // params modifier instead of most-derived type
4956                         var cpd = ((IParametersMember) candidate).Parameters;
4957                         int param_count = pd.Count;
4958                         int optional_count = 0;
4959                         int score;
4960                         Arguments orig_args = arguments;
4961
4962                         if (arg_count != param_count) {
4963                                 //
4964                                 // No arguments expansion when doing exact match for delegates
4965                                 //
4966                                 if ((restrictions & Restrictions.CovariantDelegate) == 0) {
4967                                         for (int i = 0; i < pd.Count; ++i) {
4968                                                 if (pd.FixedParameters[i].HasDefaultValue) {
4969                                                         optional_count = pd.Count - i;
4970                                                         break;
4971                                                 }
4972                                         }
4973                                 }
4974
4975                                 if (optional_count != 0) {
4976                                         // Readjust expected number when params used
4977                                         if (cpd.HasParams) {
4978                                                 optional_count--;
4979                                                 if (arg_count < param_count)
4980                                                         param_count--;
4981                                         } else if (arg_count > param_count) {
4982                                                 int args_gap = System.Math.Abs (arg_count - param_count);
4983                                                 return ArgumentCountMismatch + args_gap;
4984                                         } else if (arg_count < param_count - optional_count) {
4985                                                 int args_gap = System.Math.Abs (param_count - optional_count - arg_count);
4986                                                 return ArgumentCountMismatch + args_gap;
4987                                         }
4988                                 } else if (arg_count != param_count) {
4989                                         int args_gap = System.Math.Abs (arg_count - param_count);
4990                                         if (!cpd.HasParams)
4991                                                 return ArgumentCountMismatch + args_gap;
4992                                         if (arg_count < param_count - 1)
4993                                                 return ArgumentCountMismatch + args_gap;
4994                                 }
4995
4996                                 // Resize to fit optional arguments
4997                                 if (optional_count != 0) {
4998                                         if (arguments == null) {
4999                                                 arguments = new Arguments (optional_count);
5000                                         } else {
5001                                                 // Have to create a new container, so the next run can do same
5002                                                 var resized = new Arguments (param_count);
5003                                                 resized.AddRange (arguments);
5004                                                 arguments = resized;
5005                                         }
5006
5007                                         for (int i = arg_count; i < param_count; ++i)
5008                                                 arguments.Add (null);
5009                                 }
5010                         }
5011
5012                         if (arg_count > 0) {
5013                                 //
5014                                 // Shuffle named arguments to the right positions if there are any
5015                                 //
5016                                 if (arguments[arg_count - 1] is NamedArgument) {
5017                                         arg_count = arguments.Count;
5018
5019                                         for (int i = 0; i < arg_count; ++i) {
5020                                                 bool arg_moved = false;
5021                                                 while (true) {
5022                                                         NamedArgument na = arguments[i] as NamedArgument;
5023                                                         if (na == null)
5024                                                                 break;
5025
5026                                                         int index = pd.GetParameterIndexByName (na.Name);
5027
5028                                                         // Named parameter not found
5029                                                         if (index < 0)
5030                                                                 return NamedArgumentsMismatch - i;
5031
5032                                                         // already reordered
5033                                                         if (index == i)
5034                                                                 break;
5035
5036                                                         Argument temp;
5037                                                         if (index >= param_count) {
5038                                                                 // When using parameters which should not be available to the user
5039                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
5040                                                                         break;
5041
5042                                                                 arguments.Add (null);
5043                                                                 ++arg_count;
5044                                                                 temp = null;
5045                                                         } else {
5046                                                                 if (index == arg_count)
5047                                                                         return NamedArgumentsMismatch - i - 1;
5048
5049                                                                 temp = arguments [index];
5050
5051                                                                 // The slot has been taken by positional argument
5052                                                                 if (temp != null && !(temp is NamedArgument))
5053                                                                         break;
5054                                                         }
5055
5056                                                         if (!arg_moved) {
5057                                                                 arguments = arguments.MarkOrderedArgument (na);
5058                                                                 arg_moved = true;
5059                                                         }
5060
5061                                                         if (arguments == orig_args) {
5062                                                                 arguments = new Arguments (orig_args.Count);
5063                                                                 arguments.AddRange (orig_args);
5064                                                         }
5065
5066                                                         arguments[index] = arguments[i];
5067                                                         arguments[i] = temp;
5068
5069                                                         if (temp == null)
5070                                                                 break;
5071                                                 }
5072                                         }
5073                                 } else {
5074                                         arg_count = arguments.Count;
5075                                 }
5076                         } else if (arguments != null) {
5077                                 arg_count = arguments.Count;
5078                         }
5079
5080                         //
5081                         // Don't do any expensive checks when the candidate cannot succeed
5082                         //
5083                         if (arg_count != param_count && !cpd.HasParams)
5084                                 return DefaultArgumentMismatch - System.Math.Abs (param_count - arg_count);
5085
5086                         var dep = candidate.GetMissingDependencies ();
5087                         if (dep != null) {
5088                                 ImportedTypeDefinition.Error_MissingDependency (ec, dep, loc);
5089                                 return -1;
5090                         }
5091
5092                         //
5093                         // 1. Handle generic method using type arguments when specified or type inference
5094                         //
5095                         TypeSpec[] ptypes;
5096                         var ms = candidate as MethodSpec;
5097                         if (ms != null && ms.IsGeneric) {
5098                                 if (type_arguments != null) {
5099                                         var g_args_count = ms.Arity;
5100                                         if (g_args_count != type_arguments.Count)
5101                                                 return TypeArgumentsMismatch - System.Math.Abs (type_arguments.Count - g_args_count);
5102
5103                                         if (type_arguments.Arguments != null)
5104                                                 ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
5105                                 } else {
5106                                         //
5107                                         // Deploy custom error reporting for infered anonymous expression or lambda methods. When
5108                                         // probing lambda methods keep all errors reported in separate set and once we are done and no best
5109                                         // candidate was found use the set to report more details about what was wrong with lambda body.
5110                                         // The general idea is to distinguish between code errors and errors caused by
5111                                         // trial-and-error type inference
5112                                         //
5113                                         if (lambda_conv_msgs == null) {
5114                                                 for (int i = 0; i < arg_count; i++) {
5115                                                         Argument a = arguments[i];
5116                                                         if (a == null)
5117                                                                 continue;
5118
5119                                                         var am = a.Expr as AnonymousMethodExpression;
5120                                                         if (am != null) {
5121                                                                 if (lambda_conv_msgs == null)
5122                                                                         lambda_conv_msgs = new SessionReportPrinter ();
5123
5124                                                                 am.TypeInferenceReportPrinter = lambda_conv_msgs;
5125                                                         }
5126                                                 }
5127                                         }
5128
5129                                         var ti = new TypeInference (arguments);
5130                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
5131
5132                                         if (i_args == null)
5133                                                 return TypeArgumentsMismatch - ti.InferenceScore;
5134
5135                                         //
5136                                         // Clear any error messages when the result was success
5137                                         //
5138                                         if (lambda_conv_msgs != null)
5139                                                 lambda_conv_msgs.ClearSession ();
5140
5141                                         if (i_args.Length != 0) {
5142                                                 if (!errorMode) {
5143                                                         for (int i = 0; i < i_args.Length; ++i) {
5144                                                                 var ta = i_args [i];
5145                                                                 if (!ta.IsAccessible (ec))
5146                                                                         return TypeArgumentsMismatch - i;
5147                                                         }
5148                                                 }
5149
5150                                                 ms = ms.MakeGenericMethod (ec, i_args);
5151                                         }
5152                                 }
5153
5154                                 //
5155                                 // Type arguments constraints have to match for the method to be applicable
5156                                 //
5157                                 if (!CheckInflatedArguments (ms)) {
5158                                         candidate = ms;
5159                                         return InflatedTypesMismatch;
5160                                 }
5161
5162                                 //
5163                                 // We have a generic return type and at same time the method is override which
5164                                 // means we have to also inflate override return type in case the candidate is
5165                                 // best candidate and override return type is different to base return type.
5166                                 //
5167                                 // virtual Foo<T, object> with override Foo<T, dynamic>
5168                                 //
5169                                 if (candidate != pm) {
5170                                         MethodSpec override_ms = (MethodSpec) pm;
5171                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
5172                                         returnType = inflator.Inflate (returnType);
5173                                 } else {
5174                                         returnType = ms.ReturnType;
5175                                 }
5176
5177                                 candidate = ms;
5178                                 pd = ms.Parameters;
5179                                 ptypes = pd.Types;
5180                         } else {
5181                                 if (type_arguments != null)
5182                                         return UnexpectedTypeArguments;
5183
5184                                 ptypes = cpd.Types;
5185                         }
5186
5187                         //
5188                         // 2. Each argument has to be implicitly convertible to method parameter
5189                         //
5190                         Parameter.Modifier p_mod = 0;
5191                         TypeSpec pt = null;
5192
5193                         for (int i = 0; i < arg_count; i++) {
5194                                 Argument a = arguments[i];
5195                                 if (a == null) {
5196                                         var fp = pd.FixedParameters[i];
5197                                         if (!fp.HasDefaultValue) {
5198                                                 arguments = orig_args;
5199                                                 return arg_count * 2 + 2;
5200                                         }
5201
5202                                         //
5203                                         // Get the default value expression, we can use the same expression
5204                                         // if the type matches
5205                                         //
5206                                         Expression e = fp.DefaultValue;
5207                                         if (e != null) {
5208                                                 e = ResolveDefaultValueArgument (ec, ptypes[i], e, loc);
5209                                                 if (e == null) {
5210                                                         // Restore for possible error reporting
5211                                                         for (int ii = i; ii < arg_count; ++ii)
5212                                                                 arguments.RemoveAt (i);
5213
5214                                                         return (arg_count - i) * 2 + 1;
5215                                                 }
5216                                         }
5217
5218                                         if ((fp.ModFlags & Parameter.Modifier.CallerMask) != 0) {
5219                                                 //
5220                                                 // LAMESPEC: Attributes can be mixed together with build-in priority
5221                                                 //
5222                                                 if ((fp.ModFlags & Parameter.Modifier.CallerLineNumber) != 0) {
5223                                                         e = new IntLiteral (ec.BuiltinTypes, loc.Row, loc);
5224                                                 } else if ((fp.ModFlags & Parameter.Modifier.CallerFilePath) != 0) {
5225                                                         e = new StringLiteral (ec.BuiltinTypes, loc.NameFullPath, loc);
5226                                                 } else if (ec.MemberContext.CurrentMemberDefinition != null) {
5227                                                         e = new StringLiteral (ec.BuiltinTypes, ec.MemberContext.CurrentMemberDefinition.GetCallerMemberName (), loc);
5228                                                 }
5229                                         }
5230
5231                                         arguments[i] = new Argument (e, Argument.AType.Default);
5232                                         continue;
5233                                 }
5234
5235                                 if (p_mod != Parameter.Modifier.PARAMS) {
5236                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
5237                                         pt = ptypes [i];
5238                                 } else if (!params_expanded_form) {
5239                                         params_expanded_form = true;
5240                                         pt = ((ElementTypeSpec) pt).Element;
5241                                         i -= 2;
5242                                         continue;
5243                                 }
5244
5245                                 score = 1;
5246                                 if (!params_expanded_form) {
5247                                         if (a.IsExtensionType) {
5248                                                 if (ExtensionMethodGroupExpr.IsExtensionTypeCompatible (a.Type, pt)) {
5249                                                         score = 0;
5250                                                         continue;
5251                                                 }
5252                                         } else {
5253                                                 score = IsArgumentCompatible (ec, a, p_mod, pt);
5254
5255                                                 if (score < 0)
5256                                                         dynamicArgument = true;
5257                                         }
5258                                 }
5259
5260                                 //
5261                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
5262                                 //
5263                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
5264                                         if (!params_expanded_form) {
5265                                                 pt = ((ElementTypeSpec) pt).Element;
5266                                         }
5267
5268                                         if (score > 0)
5269                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
5270
5271                                         if (score < 0) {
5272                                                 params_expanded_form = true;
5273                                                 dynamicArgument = true;
5274                                         } else if (score == 0 || arg_count > pd.Count) {
5275                                                 params_expanded_form = true;
5276                                         }
5277                                 }
5278
5279                                 if (score > 0) {
5280                                         if (params_expanded_form)
5281                                                 ++score;
5282                                         return (arg_count - i) * 2 + score;
5283                                 }
5284                         }
5285
5286                         //
5287                         // Restore original arguments for dynamic binder to keep the intention of original source code
5288                         //
5289                         if (dynamicArgument)
5290                                 arguments = orig_args;
5291
5292                         return 0;
5293                 }
5294
5295                 public static Expression ResolveDefaultValueArgument (ResolveContext ec, TypeSpec ptype, Expression e, Location loc)
5296                 {
5297                         if (e is Constant && e.Type == ptype)
5298                                 return e;
5299
5300                         //
5301                         // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
5302                         //
5303                         if (e == EmptyExpression.MissingValue && (ptype.BuiltinType == BuiltinTypeSpec.Type.Object || ptype.BuiltinType == BuiltinTypeSpec.Type.Dynamic)) {
5304                                 e = new MemberAccess (new MemberAccess (new MemberAccess (
5305                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
5306                         } else if (e is Constant) {
5307                                 //
5308                                 // Handles int to int? conversions, DefaultParameterValue check
5309                                 //
5310                                 e = Convert.ImplicitConversionStandard (ec, e, ptype, loc);
5311                                 if (e == null)
5312                                         return null;
5313                         } else {
5314                                 e = new DefaultValueExpression (new TypeExpression (ptype, loc), loc);
5315                         }
5316
5317                         return e.Resolve (ec);
5318                 }
5319
5320                 //
5321                 // Tests argument compatibility with the parameter
5322                 // The possible return values are
5323                 // 0 - success
5324                 // 1 - modifier mismatch
5325                 // 2 - type mismatch
5326                 // -1 - dynamic binding required
5327                 //
5328                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
5329                 {
5330                         //
5331                         // Types have to be identical when ref or out modifer
5332                         // is used and argument is not of dynamic type
5333                         //
5334                         if (((argument.Modifier | param_mod) & Parameter.Modifier.RefOutMask) != 0) {
5335                                 var arg_type = argument.Type;
5336
5337                                 if ((argument.Modifier & Parameter.Modifier.RefOutMask) != (param_mod & Parameter.Modifier.RefOutMask)) {
5338                                         //
5339                                         // Using dynamic for ref/out parameter can still succeed at runtime
5340                                         //
5341                                         if (arg_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
5342                                                 return -1;
5343
5344                                         return 1;
5345                                 }
5346
5347                                 if (arg_type != parameter) {
5348                                         if (arg_type == InternalType.VarOutType)
5349                                                 return 0;
5350
5351                                         //
5352                                         // Do full equality check after quick path
5353                                         //
5354                                         if (!TypeSpecComparer.IsEqual (arg_type, parameter)) {
5355                                                 //
5356                                                 // Using dynamic for ref/out parameter can still succeed at runtime
5357                                                 //
5358                                                 if (arg_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
5359                                                         return -1;
5360
5361                                                 return 2;
5362                                         }
5363                                 }
5364
5365                         } else {
5366                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
5367                                         return -1;
5368
5369                                 //
5370                                 // Use implicit conversion in all modes to return same candidates when the expression
5371                                 // is used as argument or delegate conversion
5372                                 //
5373                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
5374                                         return parameter.IsDelegate && argument.Expr is AnonymousMethodExpression ? 2 : 3;
5375                                 }
5376                         }
5377
5378                         return 0;
5379                 }
5380
5381                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
5382                 {
5383                         if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
5384                                 return q;
5385                         if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
5386                                 return p;
5387
5388                         var ac_p = p as ArrayContainer;
5389                         if (ac_p != null) {
5390                                 var ac_q = q as ArrayContainer;
5391                                 if (ac_q == null)
5392                                         return null;
5393
5394                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
5395                                 if (specific == ac_p.Element)
5396                                         return p;
5397                                 if (specific == ac_q.Element)
5398                                         return q;
5399                         } else if (p.IsGeneric && q.IsGeneric) {
5400                                 var pargs = TypeManager.GetTypeArguments (p);
5401                                 var qargs = TypeManager.GetTypeArguments (q);
5402
5403                                 bool p_specific_at_least_once = false;
5404                                 bool q_specific_at_least_once = false;
5405
5406                                 for (int i = 0; i < pargs.Length; i++) {
5407                                         TypeSpec specific = MoreSpecific (pargs[i], qargs[i]);
5408                                         if (specific == pargs[i])
5409                                                 p_specific_at_least_once = true;
5410                                         if (specific == qargs[i])
5411                                                 q_specific_at_least_once = true;
5412                                 }
5413
5414                                 if (p_specific_at_least_once && !q_specific_at_least_once)
5415                                         return p;
5416                                 if (!p_specific_at_least_once && q_specific_at_least_once)
5417                                         return q;
5418                         }
5419
5420                         return null;
5421                 }
5422
5423                 //
5424                 // Find the best method from candidate list
5425                 //
5426                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
5427                 {
5428                         List<AmbiguousCandidate> ambiguous_candidates = null;
5429
5430                         MemberSpec best_candidate;
5431                         Arguments best_candidate_args = null;
5432                         bool best_candidate_params = false;
5433                         bool best_candidate_dynamic = false;
5434                         int best_candidate_rate;
5435                         IParametersMember best_parameter_member = null;
5436
5437                         int args_count = args != null ? args.Count : 0;
5438
5439                         Arguments candidate_args = args;
5440                         bool error_mode = false;
5441                         MemberSpec invocable_member = null;
5442                         int applicable_candidates = 0;
5443
5444                         while (true) {
5445                                 best_candidate = null;
5446                                 best_candidate_rate = int.MaxValue;
5447
5448                                 var type_members = members;
5449                                 do {
5450                                         for (int i = 0; i < type_members.Count; ++i) {
5451                                                 var member = type_members[i];
5452
5453                                                 //
5454                                                 // Methods in a base class are not candidates if any method in a derived
5455                                                 // class is applicable
5456                                                 //
5457                                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
5458                                                         continue;
5459
5460                                                 if (!error_mode) {
5461                                                         if (!member.IsAccessible (rc))
5462                                                                 continue;
5463
5464                                                         if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
5465                                                                 continue;
5466
5467                                                         if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5468                                                                 instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
5469                                                                 continue;
5470                                                         }
5471                                                 }
5472
5473                                                 IParametersMember pm = member as IParametersMember;
5474                                                 if (pm == null) {
5475                                                         //
5476                                                         // Will use it later to report ambiguity between best method and invocable member
5477                                                         //
5478                                                         if (Invocation.IsMemberInvocable (member))
5479                                                                 invocable_member = member;
5480
5481                                                         continue;
5482                                                 }
5483
5484                                                 //
5485                                                 // Overload resolution is looking for base member but using parameter names
5486                                                 // and default values from the closest member. That means to do expensive lookup
5487                                                 // for the closest override for virtual or abstract members
5488                                                 //
5489                                                 if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
5490                                                         var override_params = base_provider.GetOverrideMemberParameters (member);
5491                                                         if (override_params != null)
5492                                                                 pm = override_params;
5493                                                 }
5494
5495                                                 //
5496                                                 // Check if the member candidate is applicable
5497                                                 //
5498                                                 bool params_expanded_form = false;
5499                                                 bool dynamic_argument = false;
5500                                                 TypeSpec rt = pm.MemberType;
5501                                                 int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt, error_mode);
5502
5503                                                 if (lambda_conv_msgs != null)
5504                                                         lambda_conv_msgs.EndSession ();
5505
5506                                                 //
5507                                                 // How does it score compare to others
5508                                                 //
5509                                                 if (candidate_rate < best_candidate_rate) {
5510
5511                                                         // Fatal error (missing dependency), cannot continue
5512                                                         if (candidate_rate < 0)
5513                                                                 return null;
5514
5515                                                         applicable_candidates = 1;
5516                                                         if ((restrictions & Restrictions.GetEnumeratorLookup) != 0 && candidate_args.Count != 0) {
5517                                                                 // Only parameterless methods are considered
5518                                                         } else {
5519                                                                 best_candidate_rate = candidate_rate;
5520                                                                 best_candidate = member;
5521                                                                 best_candidate_args = candidate_args;
5522                                                                 best_candidate_params = params_expanded_form;
5523                                                                 best_candidate_dynamic = dynamic_argument;
5524                                                                 best_parameter_member = pm;
5525                                                                 best_candidate_return_type = rt;
5526                                                         }
5527                                                 } else if (candidate_rate == 0) {
5528                                                         //
5529                                                         // The member look is done per type for most operations but sometimes
5530                                                         // it's not possible like for binary operators overload because they
5531                                                         // are unioned between 2 sides
5532                                                         //
5533                                                         if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
5534                                                                 if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
5535                                                                         continue;
5536                                                         }
5537
5538                                                         ++applicable_candidates;
5539                                                         bool is_better;
5540                                                         if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5541                                                                 //
5542                                                                 // We pack all interface members into top level type which makes the overload resolution
5543                                                                 // more complicated for interfaces. We compensate it by removing methods with same
5544                                                                 // signature when building the cache hence this path should not really be hit often
5545                                                                 //
5546                                                                 // Example:
5547                                                                 // interface IA { void Foo (int arg); }
5548                                                                 // interface IB : IA { void Foo (params int[] args); }
5549                                                                 //
5550                                                                 // IB::Foo is the best overload when calling IB.Foo (1)
5551                                                                 //
5552                                                                 is_better = true;
5553                                                                 if (ambiguous_candidates != null) {
5554                                                                         foreach (var amb_cand in ambiguous_candidates) {
5555                                                                                 if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5556                                                                                         continue;
5557                                                                                 }
5558
5559                                                                                 is_better = false;
5560                                                                                 break;
5561                                                                         }
5562
5563                                                                         if (is_better)
5564                                                                                 ambiguous_candidates = null;
5565                                                                 }
5566                                                         } else {
5567                                                                 // Is the new candidate better
5568                                                                 is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
5569                                                         }
5570
5571                                                         if (is_better) {
5572                                                                 best_candidate = member;
5573                                                                 best_candidate_args = candidate_args;
5574                                                                 best_candidate_params = params_expanded_form;
5575                                                                 best_candidate_dynamic = dynamic_argument;
5576                                                                 best_parameter_member = pm;
5577                                                                 best_candidate_return_type = rt;
5578                                                         } else {
5579                                                                 // It's not better but any other found later could be but we are not sure yet
5580                                                                 if (ambiguous_candidates == null)
5581                                                                         ambiguous_candidates = new List<AmbiguousCandidate> ();
5582
5583                                                                 ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
5584                                                         }
5585                                                 }
5586
5587                                                 // Restore expanded arguments
5588                                                 candidate_args = args;
5589                                         }
5590                                 } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType)) != null);
5591
5592                                 //
5593                                 // We've found exact match
5594                                 //
5595                                 if (best_candidate_rate == 0)
5596                                         break;
5597
5598                                 //
5599                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
5600                                 //
5601                                 if (!error_mode) {
5602                                         var emg = base_provider.LookupExtensionMethod (rc);
5603                                         if (emg != null) {
5604                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
5605                                                 if (emg != null) {
5606                                                         best_candidate_extension_group = emg;
5607                                                         return (T) (MemberSpec) emg.BestCandidate;
5608                                                 }
5609                                         }
5610                                 }
5611
5612                                 // Don't run expensive error reporting mode for probing
5613                                 if (IsProbingOnly)
5614                                         return null;
5615
5616                                 if (error_mode)
5617                                         break;
5618
5619                                 if (lambda_conv_msgs != null && !lambda_conv_msgs.IsEmpty)
5620                                         break;
5621
5622                                 lambda_conv_msgs = null;
5623                                 error_mode = true;
5624                         }
5625
5626                         //
5627                         // No best member match found, report an error
5628                         //
5629                         if (best_candidate_rate != 0 || error_mode) {
5630                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
5631                                 return null;
5632                         }
5633
5634                         if (best_candidate_dynamic) {
5635                                 if (args[0].IsExtensionType) {
5636                                         rc.Report.Error (1973, loc,
5637                                                 "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",
5638                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
5639                                 }
5640
5641                                 //
5642                                 // Check type constraints only when explicit type arguments are used
5643                                 //
5644                                 if (applicable_candidates == 1 && best_candidate.IsGeneric && type_arguments != null) {
5645                                         MethodSpec bc = best_candidate as MethodSpec;
5646                                         if (bc != null && TypeParameterSpec.HasAnyTypeParameterConstrained (bc.GenericDefinition)) {
5647                                                 ConstraintChecker cc = new ConstraintChecker (rc);
5648                                                 cc.CheckAll (bc.GetGenericMethodDefinition (), bc.TypeArguments, bc.Constraints, loc);
5649                                         }
5650                                 }
5651
5652                                 BestCandidateIsDynamic = true;
5653                                 return null;
5654                         }
5655
5656                         //
5657                         // These flags indicates we are running delegate probing conversion. No need to
5658                         // do more expensive checks
5659                         //
5660                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
5661                                 return (T) best_candidate;
5662
5663                         if (ambiguous_candidates != null) {
5664                                 //
5665                                 // Now check that there are no ambiguities i.e the selected method
5666                                 // should be better than all the others
5667                                 //
5668                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
5669                                         var candidate = ambiguous_candidates [ix];
5670
5671                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
5672                                                 var ambiguous = candidate.Member;
5673                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
5674                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
5675                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
5676                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
5677                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
5678                                                 }
5679
5680                                                 return (T) best_candidate;
5681                                         }
5682                                 }
5683                         }
5684
5685                         if (invocable_member != null && !IsProbingOnly) {
5686                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5687                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
5688                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
5689                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
5690                         }
5691
5692                         //
5693                         // And now check if the arguments are all
5694                         // compatible, perform conversions if
5695                         // necessary etc. and return if everything is
5696                         // all right
5697                         //
5698                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
5699                                 return null;
5700
5701                         if (best_candidate == null)
5702                                 return null;
5703
5704                         //
5705                         // Don't run possibly expensive checks in probing mode
5706                         //
5707                         if (!IsProbingOnly && !rc.IsInProbingMode) {
5708                                 //
5709                                 // Check ObsoleteAttribute on the best method
5710                                 //
5711                                 best_candidate.CheckObsoleteness (rc, loc);
5712
5713                                 best_candidate.MemberDefinition.SetIsUsed ();
5714                         }
5715
5716                         args = best_candidate_args;
5717                         return (T) best_candidate;
5718                 }
5719
5720                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
5721                 {
5722                         return ResolveMember<MethodSpec> (rc, ref args);
5723                 }
5724
5725                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
5726                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
5727                 {
5728                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
5729                                 return;
5730
5731                         if (a.Type == InternalType.ErrorType)
5732                                 return;
5733
5734                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
5735                                 ec.Report.SymbolRelatedToPreviousError (method);
5736                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
5737                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have `ref' or `out' modifier",
5738                                                 TypeManager.CSharpSignature (method));
5739                                         return;
5740                                 }
5741                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
5742                                           TypeManager.CSharpSignature (method));
5743                         } else if (IsDelegateInvoke) {
5744                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
5745                                         DelegateType.GetSignatureForError ());
5746                         } else {
5747                                 ec.Report.SymbolRelatedToPreviousError (method);
5748                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
5749                                         method.GetSignatureForError ());
5750                         }
5751
5752                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
5753
5754                         string index = (idx + 1).ToString ();
5755                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
5756                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
5757                                         ec.Report.Error (1615, a.Expr.Location, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
5758                                                 index, Parameter.GetModifierSignature (a.Modifier));
5759                                 else
5760                                         ec.Report.Error (1620, a.Expr.Location, "Argument `#{0}' is missing `{1}' modifier",
5761                                                 index, Parameter.GetModifierSignature (mod));
5762                         } else {
5763                                 string p1 = a.GetSignatureForError ();
5764                                 string p2 = paramType.GetSignatureForError ();
5765
5766                                 if (p1 == p2) {
5767                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
5768                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
5769                                 }
5770
5771                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
5772                                         p1 = Parameter.GetModifierSignature (a.Modifier) + " " + p1;
5773                                         p2 = Parameter.GetModifierSignature (a.Modifier) + " " + p2;
5774                                 }
5775
5776                                 ec.Report.Error (1503, a.Expr.Location,
5777                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
5778                         }
5779                 }
5780
5781                 //
5782                 // We have failed to find exact match so we return error info about the closest match
5783                 //
5784                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
5785                 {
5786                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
5787                         int arg_count = args == null ? 0 : args.Count;
5788
5789                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
5790                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
5791                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, loc);
5792                                 return;
5793                         }
5794
5795                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
5796                                 return;
5797                         }
5798
5799
5800                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5801                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
5802                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
5803                         }
5804
5805                         //
5806                         // For candidates which match on parameters count report more details about incorrect arguments
5807                         //
5808                         if (pm != null) {
5809                                 if (pm.Parameters.Count == arg_count || params_expanded || HasUnfilledParams (best_candidate, pm, args)) {
5810                                         // Reject any inaccessible member
5811                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
5812                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5813                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
5814                                                 return;
5815                                         }
5816
5817                                         var ms = best_candidate as MethodSpec;
5818                                         if (ms != null && ms.IsGeneric) {
5819                                                 bool constr_ok = true;
5820                                                 if (ms.TypeArguments != null)
5821                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
5822
5823                                                 if (ta_count == 0 && ms.TypeArguments == null) {
5824                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
5825                                                                 return;
5826
5827                                                         if (constr_ok) {
5828                                                                 rc.Report.Error (411, loc,
5829                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
5830                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
5831                                                         }
5832
5833                                                         return;
5834                                                 }
5835                                         }
5836
5837                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
5838                                         return;
5839                                 }
5840                         }
5841
5842                         //
5843                         // We failed to find any method with correct argument count, report best candidate
5844                         //
5845                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
5846                                 return;
5847
5848                         if (best_candidate.Kind == MemberKind.Constructor) {
5849                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5850                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
5851                         } else if (IsDelegateInvoke) {
5852                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
5853                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
5854                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
5855                         } else {
5856                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
5857                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5858                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
5859                                         name, arg_count.ToString ());
5860                         }
5861                 }
5862
5863                 static bool HasUnfilledParams (MemberSpec best_candidate, IParametersMember pm, Arguments args)
5864                 {
5865                         var p = ((IParametersMember)best_candidate).Parameters;
5866                         if (!p.HasParams)
5867                                 return false;
5868
5869                         string name = null;
5870                         for (int i = p.Count - 1; i != 0; --i) {
5871                                 var fp = p.FixedParameters [i];
5872                                 if ((fp.ModFlags & Parameter.Modifier.PARAMS) == 0)
5873                                         continue;
5874
5875                                 name = fp.Name;
5876                                 break;
5877                         }
5878
5879                         if (args == null)
5880                                 return false;
5881
5882                         foreach (var arg in args) {
5883                                 var na = arg as NamedArgument;
5884                                 if (na == null)
5885                                         continue;
5886
5887                                 if (na.Name == name) {
5888                                         name = null;
5889                                         break;
5890                                 }
5891                         }
5892
5893                         if (name == null)
5894                                 return false;
5895
5896                         return args.Count + 1 == pm.Parameters.Count;
5897                 }
5898
5899                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
5900                 {
5901                         var pd = pm.Parameters;
5902                         var cpd = ((IParametersMember) member).Parameters;
5903                         var ptypes = cpd.Types;
5904
5905                         Parameter.Modifier p_mod = 0;
5906                         TypeSpec pt = null;
5907                         int a_idx = 0, a_pos = 0;
5908                         Argument a = null;
5909                         ArrayInitializer params_initializers = null;
5910                         bool has_unsafe_arg = pm.MemberType.IsPointer;
5911                         int arg_count = args == null ? 0 : args.Count;
5912
5913                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
5914                                 a = args[a_idx];
5915                                 if (a == null)
5916                                         continue;
5917
5918                                 if (p_mod != Parameter.Modifier.PARAMS) {
5919                                         p_mod = cpd.FixedParameters [a_idx].ModFlags;
5920                                         pt = ptypes[a_idx];
5921                                         has_unsafe_arg |= pt.IsPointer;
5922
5923                                         if (p_mod == Parameter.Modifier.PARAMS) {
5924                                                 if (chose_params_expanded) {
5925                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
5926                                                         pt = TypeManager.GetElementType (pt);
5927                                                 }
5928                                         }
5929                                 }
5930
5931                                 //
5932                                 // Types have to be identical when ref or out modifer is used
5933                                 //
5934                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
5935                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
5936                                                 break;
5937
5938                                         var arg_type = a.Type;
5939                                         if (arg_type == pt)
5940                                                 continue;
5941
5942                                         if (arg_type == InternalType.VarOutType) {
5943                                                 //
5944                                                 // Set underlying variable type based on parameter type
5945                                                 //
5946                                                 ((DeclarationExpression)a.Expr).Variable.Type = pt;
5947                                                 continue;
5948                                         }
5949
5950                                         if (!TypeSpecComparer.IsEqual (arg_type, pt))
5951                                                 break;
5952                                 }
5953
5954                                 NamedArgument na = a as NamedArgument;
5955                                 if (na != null) {
5956                                         int name_index = pd.GetParameterIndexByName (na.Name);
5957                                         if (name_index < 0 || name_index >= pd.Count) {
5958                                                 if (IsDelegateInvoke) {
5959                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5960                                                         ec.Report.Error (1746, na.Location,
5961                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
5962                                                                 DelegateType.GetSignatureForError (), na.Name);
5963                                                 } else {
5964                                                         ec.Report.SymbolRelatedToPreviousError (member);
5965                                                         ec.Report.Error (1739, na.Location,
5966                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
5967                                                                 TypeManager.CSharpSignature (member), na.Name);
5968                                                 }
5969                                         } else if (args[name_index] != a && args[name_index] != null) {
5970                                                 if (IsDelegateInvoke)
5971                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5972                                                 else
5973                                                         ec.Report.SymbolRelatedToPreviousError (member);
5974
5975                                                 ec.Report.Error (1744, na.Location,
5976                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
5977                                                         na.Name);
5978                                         }
5979                                 }
5980
5981                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
5982                                         continue;
5983
5984                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
5985                                         if (a.IsExtensionType) {
5986                                                 // TODO: Should report better message type, something similar to CS1928/1929 instead of
5987                                                 // CS1061 but that still better than confusing CS0123
5988                                                 var ma = new MemberAccess (a.Expr, member.Name, loc);
5989                                                 ma.Error_TypeDoesNotContainDefinition (ec, a.Expr.Type, ma.Name);
5990                                         } else {
5991                                                 custom_errors.NoArgumentMatch (ec, member);
5992                                         }
5993                                         return false;
5994                                 }
5995
5996                                 Expression conv;
5997                                 if (a.IsExtensionType) {
5998                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
5999                                                 conv = a.Expr;
6000                                         } else {
6001                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
6002                                                 if (conv == null)
6003                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
6004                                         }
6005                                 } else {
6006                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
6007                                 }
6008
6009                                 if (conv == null)
6010                                         break;
6011
6012                                 //
6013                                 // Convert params arguments to an array initializer
6014                                 //
6015                                 if (params_initializers != null) {
6016                                         // we choose to use 'a.Expr' rather than 'conv' so that
6017                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
6018                                         params_initializers.Add (a.Expr);
6019                                         args.RemoveAt (a_idx--);
6020                                         --arg_count;
6021                                         a.Expr = conv;
6022                                         continue;
6023                                 }
6024
6025                                 // Update the argument with the implicit conversion
6026                                 a.Expr = conv;
6027                         }
6028
6029                         if (a_idx != arg_count) {
6030                                 //
6031                                 // Convert all var out argument to error type for less confusing error reporting
6032                                 // when no matching overload is found
6033                                 //
6034                                 for (; a_idx < arg_count; a_idx++) {
6035                                         var arg = args [a_idx];
6036                                         if (arg == null)
6037                                                 continue;
6038
6039                                         if (arg.Type == InternalType.VarOutType) {
6040                                                 ((DeclarationExpression)arg.Expr).Variable.Type = InternalType.ErrorType;
6041                                         }
6042                                 }
6043
6044                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
6045                                 return false;
6046                         }
6047
6048                         //
6049                         // Fill not provided arguments required by params modifier
6050                         //
6051                         if (params_initializers == null && arg_count + 1 == pd.Count) {
6052                                 if (args == null)
6053                                         args = new Arguments (1);
6054
6055                                 pt = ptypes[pd.Count - 1];
6056                                 pt = TypeManager.GetElementType (pt);
6057                                 has_unsafe_arg |= pt.IsPointer;
6058                                 params_initializers = new ArrayInitializer (0, loc);
6059                         }
6060
6061                         //
6062                         // Append an array argument with all params arguments
6063                         //
6064                         if (params_initializers != null) {
6065                                 args.Add (new Argument (
6066                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
6067                                 arg_count++;
6068                         }
6069
6070                         if (has_unsafe_arg && !ec.IsUnsafe) {
6071                                 Expression.UnsafeError (ec, loc);
6072                         }
6073
6074                         //
6075                         // We could infer inaccesible type arguments
6076                         //
6077                         if (type_arguments == null && member.IsGeneric) {
6078                                 var ms = (MethodSpec) member;
6079                                 foreach (var ta in ms.TypeArguments) {
6080                                         if (!ta.IsAccessible (ec)) {
6081                                                 ec.Report.SymbolRelatedToPreviousError (ta);
6082                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
6083                                                 break;
6084                                         }
6085                                 }
6086                         }
6087
6088                         return true;
6089                 }
6090         }
6091
6092         public class ConstantExpr : MemberExpr
6093         {
6094                 readonly ConstSpec constant;
6095
6096                 public ConstantExpr (ConstSpec constant, Location loc)
6097                 {
6098                         this.constant = constant;
6099                         this.loc = loc;
6100                 }
6101
6102                 public override string Name {
6103                         get { throw new NotImplementedException (); }
6104                 }
6105
6106                 public override string KindName {
6107                         get { return "constant"; }
6108                 }
6109
6110                 public override bool IsInstance {
6111                         get { return !IsStatic; }
6112                 }
6113
6114                 public override bool IsStatic {
6115                         get { return true; }
6116                 }
6117
6118                 protected override TypeSpec DeclaringType {
6119                         get { return constant.DeclaringType; }
6120                 }
6121
6122                 public override Expression CreateExpressionTree (ResolveContext ec)
6123                 {
6124                         throw new NotSupportedException ("ET");
6125                 }
6126
6127                 protected override Expression DoResolve (ResolveContext rc)
6128                 {
6129                         ResolveInstanceExpression (rc, null);
6130                         DoBestMemberChecks (rc, constant);
6131
6132                         if (rc.HasSet (ResolveContext.Options.NameOfScope)) {
6133                                 eclass = ExprClass.Value;
6134                                 type = constant.MemberType;
6135                                 return this;
6136                         }
6137
6138                         var c = constant.GetConstant (rc);
6139
6140                         // Creates reference expression to the constant value
6141                         return Constant.CreateConstantFromValue (constant.MemberType, c.GetValue (), loc);
6142                 }
6143
6144                 public override void Emit (EmitContext ec)
6145                 {
6146                         throw new NotSupportedException ();
6147                 }
6148
6149                 public override string GetSignatureForError ()
6150                 {
6151                         return constant.GetSignatureForError ();
6152                 }
6153
6154                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
6155                 {
6156                         constant.CheckObsoleteness (rc, expr.Location);
6157                 }
6158
6159                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6160                 {
6161                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
6162                 }
6163         }
6164
6165         //
6166         // Fully resolved expression that references a Field
6167         //
6168         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
6169         {
6170                 protected FieldSpec spec;
6171                 VariableInfo variable_info;
6172
6173                 LocalTemporary temp;
6174                 bool prepared;
6175
6176                 protected FieldExpr (Location l)
6177                 {
6178                         loc = l;
6179                 }
6180
6181                 public FieldExpr (FieldSpec spec, Location loc)
6182                 {
6183                         this.spec = spec;
6184                         this.loc = loc;
6185
6186                         type = spec.MemberType;
6187                 }
6188
6189                 public FieldExpr (FieldBase fi, Location l)
6190                         : this (fi.Spec, l)
6191                 {
6192                 }
6193
6194                 #region Properties
6195
6196                 public override string Name {
6197                         get {
6198                                 return spec.Name;
6199                         }
6200                 }
6201
6202                 public bool IsHoisted {
6203                         get {
6204                                 IVariableReference hv = InstanceExpression as IVariableReference;
6205                                 return hv != null && hv.IsHoisted;
6206                         }
6207                 }
6208
6209                 public override bool IsInstance {
6210                         get {
6211                                 return !spec.IsStatic;
6212                         }
6213                 }
6214
6215                 public override bool IsStatic {
6216                         get {
6217                                 return spec.IsStatic;
6218                         }
6219                 }
6220
6221                 public override string KindName {
6222                         get { return "field"; }
6223                 }
6224
6225                 public FieldSpec Spec {
6226                         get {
6227                                 return spec;
6228                         }
6229                 }
6230
6231                 protected override TypeSpec DeclaringType {
6232                         get {
6233                                 return spec.DeclaringType;
6234                         }
6235                 }
6236
6237                 public VariableInfo VariableInfo {
6238                         get {
6239                                 return variable_info;
6240                         }
6241                 }
6242
6243 #endregion
6244
6245                 public override string GetSignatureForError ()
6246                 {
6247                         return spec.GetSignatureForError ();
6248                 }
6249
6250                 public bool IsMarshalByRefAccess (ResolveContext rc)
6251                 {
6252                         // Checks possible ldflda of field access expression
6253                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
6254                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
6255                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
6256                 }
6257
6258                 public void SetHasAddressTaken ()
6259                 {
6260                         IVariableReference vr = InstanceExpression as IVariableReference;
6261                         if (vr != null) {
6262                                 vr.SetHasAddressTaken ();
6263                         }
6264                 }
6265
6266                 protected override void CloneTo (CloneContext clonectx, Expression target)
6267                 {
6268                         var t = (FieldExpr) target;
6269
6270                         if (InstanceExpression != null)
6271                                 t.InstanceExpression = InstanceExpression.Clone (clonectx);
6272                 }
6273
6274                 public override Expression CreateExpressionTree (ResolveContext ec)
6275                 {
6276                         if (ConditionalAccess) {
6277                                 Error_NullShortCircuitInsideExpressionTree (ec);
6278                         }
6279
6280                         return CreateExpressionTree (ec, true);
6281                 }
6282
6283                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
6284                 {
6285                         Arguments args;
6286                         Expression instance;
6287
6288                         if (InstanceExpression == null) {
6289                                 instance = new NullLiteral (loc);
6290                         } else if (convertInstance) {
6291                                 instance = InstanceExpression.CreateExpressionTree (ec);
6292                         } else {
6293                                 args = new Arguments (1);
6294                                 args.Add (new Argument (InstanceExpression));
6295                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
6296                         }
6297
6298                         args = Arguments.CreateForExpressionTree (ec, null,
6299                                 instance,
6300                                 CreateTypeOfExpression ());
6301
6302                         return CreateExpressionFactoryCall (ec, "Field", args);
6303                 }
6304
6305                 public Expression CreateTypeOfExpression ()
6306                 {
6307                         return new TypeOfField (spec, loc);
6308                 }
6309
6310                 protected override Expression DoResolve (ResolveContext ec)
6311                 {
6312                         spec.MemberDefinition.SetIsUsed ();
6313
6314                         return DoResolve (ec, null);
6315                 }
6316
6317                 Expression DoResolve (ResolveContext ec, Expression rhs)
6318                 {
6319                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
6320
6321                         if (rhs != this) {
6322                                 ResolveConditionalAccessReceiver (ec);
6323
6324                                 if (ResolveInstanceExpression (ec, rhs)) {
6325                                         // Resolve the field's instance expression while flow analysis is turned
6326                                         // off: when accessing a field "a.b", we must check whether the field
6327                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
6328
6329                                         if (lvalue_instance) {
6330                                                 bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
6331
6332                                                 Expression right_side =
6333                                                         out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
6334
6335                                                 InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
6336                                         } else {
6337                                                 InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
6338                                         }
6339
6340                                         if (InstanceExpression == null)
6341                                                 return null;
6342                                 }
6343
6344                                 DoBestMemberChecks (ec, spec);
6345
6346                                 if (conditional_access_receiver)
6347                                         ec.With (ResolveContext.Options.DontSetConditionalAccessReceiver, false);
6348                         }
6349
6350                         var fb = spec as FixedFieldSpec;
6351                         IVariableReference var = InstanceExpression as IVariableReference;
6352
6353                         if (fb != null) {
6354                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6355                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
6356                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
6357                                 }
6358
6359                                 if (InstanceExpression.eclass != ExprClass.Variable) {
6360                                         ec.Report.SymbolRelatedToPreviousError (spec);
6361                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
6362                                                 TypeManager.GetFullNameSignature (spec));
6363                                 } else if (var != null && var.IsHoisted) {
6364                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
6365                                 }
6366
6367                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
6368                         }
6369
6370                         //
6371                         // Set flow-analysis variable info for struct member access. It will be check later
6372                         // for precise error reporting
6373                         //
6374                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
6375                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
6376                         }
6377
6378                         if (conditional_access_receiver)
6379                                 type = LiftMemberType (ec, type);
6380
6381                         if (ConditionalAccess && InstanceExpression != null && InstanceExpression.IsNull)
6382                                 return Constant.CreateConstantFromValue (type, null, loc);
6383
6384                         eclass = ExprClass.Variable;
6385                         return this;
6386                 }
6387
6388                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
6389                 {
6390                         spec.CheckObsoleteness (rc, expr.Location);
6391                 }
6392
6393                 public void SetFieldAssigned (FlowAnalysisContext fc)
6394                 {
6395                         if (!IsInstance)
6396                                 return;
6397
6398                         bool lvalue_instance = spec.DeclaringType.IsStruct;
6399                         if (lvalue_instance) {
6400                                 var var = InstanceExpression as IVariableReference;
6401                                 if (var != null && var.VariableInfo != null) {
6402                                         fc.SetStructFieldAssigned (var.VariableInfo, Name);
6403                                 }
6404                         }
6405
6406                         var fe = InstanceExpression as FieldExpr;
6407                         if (fe != null) {
6408                                 Expression instance;
6409
6410                                 do {
6411                                         instance = fe.InstanceExpression;
6412                                         var fe_instance = instance as FieldExpr;
6413                                         if ((fe_instance != null && !fe_instance.IsStatic) || instance is LocalVariableReference) {
6414                                                 if (TypeSpec.IsReferenceType (fe.Type) && instance.Type.IsStruct) {
6415                                                         var var = InstanceExpression as IVariableReference;
6416                                                         if (var != null && var.VariableInfo == null) {
6417                                                                 var var_inst = instance as IVariableReference;
6418                                                                 if (var_inst == null || (var_inst.VariableInfo != null && !fc.IsDefinitelyAssigned (var_inst.VariableInfo)))
6419                                                                         fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
6420                                                         }
6421                                                 }
6422
6423                                                 if (fe_instance != null) {
6424                                                         fe = fe_instance;
6425                                                         continue;
6426                                                 }
6427                                         }
6428
6429                                         break;
6430                                 } while (true);
6431
6432                                 if (instance != null && TypeSpec.IsReferenceType (instance.Type))
6433                                         instance.FlowAnalysis (fc);
6434                         } else {
6435                                 if (TypeSpec.IsReferenceType (InstanceExpression.Type))
6436                                         InstanceExpression.FlowAnalysis (fc);
6437                         }
6438                 }
6439
6440                 Expression Error_AssignToReadonly (ResolveContext rc, Expression right_side)
6441                 {
6442                         // The return value is always null.  Returning a value simplifies calling code.
6443
6444                         if (right_side == EmptyExpression.OutAccess) {
6445                                 if (IsStatic) {
6446                                         rc.Report.Error (199, loc, "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6447                                                 GetSignatureForError ());
6448                                 } else {
6449                                         rc.Report.Error (192, loc, "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6450                                                 GetSignatureForError ());
6451                                 }
6452
6453                                 return null;
6454                         }
6455
6456                         if (right_side == EmptyExpression.LValueMemberAccess) {
6457                                 // Already reported as CS1648/CS1650
6458                                 return null;
6459                         }
6460
6461                         if (right_side == EmptyExpression.LValueMemberOutAccess) {
6462                                 if (IsStatic) {
6463                                         rc.Report.Error (1651, loc, "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6464                                                 GetSignatureForError ());
6465                                 } else {
6466                                         rc.Report.Error (1649, loc, "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6467                                                 GetSignatureForError ());
6468                                 }
6469                                 return null;
6470                         }
6471
6472                         if (IsStatic) {
6473                                 rc.Report.Error (198, loc, "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
6474                                         GetSignatureForError ());
6475                         } else {
6476                                 rc.Report.Error (191, loc, "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
6477                                         GetSignatureForError ());
6478                         }
6479
6480                         return null;
6481                 }
6482
6483                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6484                 {
6485                         if (HasConditionalAccess ())
6486                                 Error_NullPropagatingLValue (ec);
6487
6488                         if (spec is FixedFieldSpec) {
6489                                 // It could be much better error message but we want to be error compatible
6490                                 Error_ValueAssignment (ec, right_side);
6491                         }
6492
6493                         Expression e = DoResolve (ec, right_side);
6494
6495                         if (e == null)
6496                                 return null;
6497
6498                         spec.MemberDefinition.SetIsAssigned ();
6499
6500                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
6501                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
6502                                 ec.Report.Warning (420, 1, loc,
6503                                         "`{0}': A volatile field references will not be treated as volatile",
6504                                         spec.GetSignatureForError ());
6505                         }
6506
6507                         if (spec.IsReadOnly) {
6508                                 // InitOnly fields can only be assigned in constructors or initializers
6509                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
6510                                         return Error_AssignToReadonly (ec, right_side);
6511
6512                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
6513
6514                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
6515                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
6516                                                 return Error_AssignToReadonly (ec, right_side);
6517                                         // static InitOnly fields cannot be assigned-to in an instance constructor
6518                                         if (IsStatic && !ec.IsStatic)
6519                                                 return Error_AssignToReadonly (ec, right_side);
6520                                         // instance constructors can't modify InitOnly fields of other instances of the same type
6521                                         if (!IsStatic && !(InstanceExpression is This))
6522                                                 return Error_AssignToReadonly (ec, right_side);
6523                                 }
6524                         }
6525
6526                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
6527                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
6528                                 ec.Report.Warning (197, 1, loc,
6529                                                 "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",
6530                                                 GetSignatureForError ());
6531                         }
6532
6533                         eclass = ExprClass.Variable;
6534                         return this;
6535                 }
6536
6537                 public override void FlowAnalysis (FlowAnalysisContext fc)
6538                 {
6539                         var var = InstanceExpression as IVariableReference;
6540                         if (var != null) {
6541                                 var vi = var.VariableInfo;
6542                                 if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, Name)) {
6543                                         fc.Report.Error (170, loc, "Use of possibly unassigned field `{0}'", Name);
6544                                         return;
6545                                 }
6546
6547                                 if (TypeSpec.IsValueType (InstanceExpression.Type)) {
6548                                         var le = SkipLeftValueTypeAccess (InstanceExpression);
6549                                         if (le != null)
6550                                                 le.FlowAnalysis (fc);
6551
6552                                         return;
6553                                 }
6554                         }
6555
6556                         var da = conditional_access_receiver ? fc.BranchDefiniteAssignment () : null;
6557
6558                         base.FlowAnalysis (fc);
6559
6560                         if (conditional_access_receiver)
6561                                 fc.DefiniteAssignment = da;
6562                 }
6563
6564                 static Expression SkipLeftValueTypeAccess (Expression expr)
6565                 {
6566                         if (!TypeSpec.IsValueType (expr.Type))
6567                                 return expr;
6568
6569                         if (expr is VariableReference)
6570                                 return null;
6571
6572                         var fe = expr as FieldExpr;
6573                         if (fe == null)
6574                                 return expr;
6575
6576                         if (fe.InstanceExpression == null)
6577                                 return expr;
6578
6579                         return SkipLeftValueTypeAccess (fe.InstanceExpression);
6580                 }
6581
6582                 public override int GetHashCode ()
6583                 {
6584                         return spec.GetHashCode ();
6585                 }
6586
6587                 public bool IsFixed {
6588                         get {
6589                                 //
6590                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
6591                                 //
6592                                 IVariableReference variable = InstanceExpression as IVariableReference;
6593                                 if (variable != null)
6594                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
6595
6596                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6597                                 return fe != null && fe.IsFixed;
6598                         }
6599                 }
6600
6601                 public override bool Equals (object obj)
6602                 {
6603                         FieldExpr fe = obj as FieldExpr;
6604                         if (fe == null)
6605                                 return false;
6606
6607                         if (spec != fe.spec)
6608                                 return false;
6609
6610                         if (InstanceExpression == null || fe.InstanceExpression == null)
6611                                 return true;
6612
6613                         return InstanceExpression.Equals (fe.InstanceExpression);
6614                 }
6615
6616                 public void Emit (EmitContext ec, bool leave_copy)
6617                 {
6618                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6619
6620                         if (IsStatic){
6621                                 if (is_volatile)
6622                                         ec.Emit (OpCodes.Volatile);
6623
6624                                 ec.Emit (OpCodes.Ldsfld, spec);
6625                         } else {
6626                                 var ca = ec.ConditionalAccess;
6627
6628                                 if (!prepared) {
6629                                         if (conditional_access_receiver)
6630                                                 ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
6631
6632                                         EmitInstance (ec, false);
6633                                 }
6634
6635                                 // Optimization for build-in types
6636                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
6637                                         ec.EmitLoadFromPtr (type);
6638                                 } else {
6639                                         var ff = spec as FixedFieldSpec;
6640                                         if (ff != null) {
6641                                                 ec.Emit (OpCodes.Ldflda, spec);
6642                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
6643                                         } else {
6644                                                 if (is_volatile)
6645                                                         ec.Emit (OpCodes.Volatile);
6646
6647                                                 ec.Emit (OpCodes.Ldfld, spec);
6648                                         }
6649                                 }
6650
6651                                 if (conditional_access_receiver) {
6652                                         ec.CloseConditionalAccess (type.IsNullableType && type != spec.MemberType ? type : null);
6653                                         ec.ConditionalAccess = ca;
6654                                 }
6655                         }
6656
6657                         if (leave_copy) {
6658                                 ec.Emit (OpCodes.Dup);
6659                                 if (!IsStatic) {
6660                                         temp = new LocalTemporary (this.Type);
6661                                         temp.Store (ec);
6662                                 }
6663                         }
6664                 }
6665
6666                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6667                 {
6668                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
6669                         if (isCompound && !(source is DynamicExpressionStatement) && !has_await_source) {
6670                                 prepared = true;
6671                         }
6672
6673                         if (IsInstance) {
6674                                 if (ConditionalAccess)
6675                                         throw new NotImplementedException ("null operator assignment");
6676
6677                                 if (has_await_source)
6678                                         source = source.EmitToField (ec);
6679
6680                                 EmitInstance (ec, prepared);
6681                         }
6682
6683                         source.Emit (ec);
6684
6685                         if (leave_copy || ec.NotifyEvaluatorOnStore) {
6686                                 ec.Emit (OpCodes.Dup);
6687                                 if (!IsStatic) {
6688                                         temp = new LocalTemporary (this.Type);
6689                                         temp.Store (ec);
6690                                 }
6691                         }
6692
6693                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
6694                                 ec.Emit (OpCodes.Volatile);
6695
6696                         spec.MemberDefinition.SetIsAssigned ();
6697
6698                         if (IsStatic)
6699                                 ec.Emit (OpCodes.Stsfld, spec);
6700                         else
6701                                 ec.Emit (OpCodes.Stfld, spec);
6702
6703                         if (ec.NotifyEvaluatorOnStore) {
6704                                 if (!IsStatic)
6705                                         throw new NotImplementedException ("instance field write");
6706
6707                                 if (leave_copy)
6708                                         ec.Emit (OpCodes.Dup);
6709
6710                                 ec.Module.Evaluator.EmitValueChangedCallback (ec, Name, type, loc);
6711                         }
6712
6713                         if (temp != null) {
6714                                 temp.Emit (ec);
6715                                 temp.Release (ec);
6716                                 temp = null;
6717                         }
6718                 }
6719
6720                 //
6721                 // Emits store to field with prepared values on stack
6722                 //
6723                 public void EmitAssignFromStack (EmitContext ec)
6724                 {
6725                         if (IsStatic) {
6726                                 ec.Emit (OpCodes.Stsfld, spec);
6727                         } else {
6728                                 ec.Emit (OpCodes.Stfld, spec);
6729                         }
6730                 }
6731
6732                 public override void Emit (EmitContext ec)
6733                 {
6734                         Emit (ec, false);
6735                 }
6736
6737                 public override void EmitSideEffect (EmitContext ec)
6738                 {
6739                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6740
6741                         if (is_volatile) // || is_marshal_by_ref ())
6742                                 base.EmitSideEffect (ec);
6743                 }
6744
6745                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
6746                 {
6747                         if ((mode & AddressOp.Store) != 0)
6748                                 spec.MemberDefinition.SetIsAssigned ();
6749                         if ((mode & AddressOp.Load) != 0)
6750                                 spec.MemberDefinition.SetIsUsed ();
6751
6752                         //
6753                         // Handle initonly fields specially: make a copy and then
6754                         // get the address of the copy.
6755                         //
6756                         bool need_copy;
6757                         if (spec.IsReadOnly){
6758                                 need_copy = true;
6759                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
6760                                         if (IsStatic){
6761                                                 if (ec.IsStatic)
6762                                                         need_copy = false;
6763                                         } else
6764                                                 need_copy = false;
6765                                 }
6766                         } else
6767                                 need_copy = false;
6768
6769                         if (need_copy) {
6770                                 Emit (ec);
6771                                 var temp = ec.GetTemporaryLocal (type);
6772                                 ec.Emit (OpCodes.Stloc, temp);
6773                                 ec.Emit (OpCodes.Ldloca, temp);
6774                                 return;
6775                         }
6776
6777
6778                         if (IsStatic){
6779                                 ec.Emit (OpCodes.Ldsflda, spec);
6780                         } else {
6781                                 if (!prepared)
6782                                         EmitInstance (ec, false);
6783                                 ec.Emit (OpCodes.Ldflda, spec);
6784                         }
6785                 }
6786
6787                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6788                 {
6789                         return MakeExpression (ctx);
6790                 }
6791
6792                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6793                 {
6794 #if STATIC
6795                         return base.MakeExpression (ctx);
6796 #else
6797                         return SLE.Expression.Field (
6798                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
6799                                 spec.GetMetaInfo ());
6800 #endif
6801                 }
6802
6803                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6804                 {
6805                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
6806                 }
6807         }
6808
6809
6810         //
6811         // Expression that evaluates to a Property.
6812         //
6813         // This is not an LValue because we need to re-write the expression. We
6814         // can not take data from the stack and store it.
6815         //
6816         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
6817         {
6818                 Arguments arguments;
6819                 FieldExpr backing_field;
6820
6821                 public PropertyExpr (PropertySpec spec, Location l)
6822                         : base (l)
6823                 {
6824                         best_candidate = spec;
6825                         type = spec.MemberType;
6826                 }
6827
6828                 #region Properties
6829
6830                 protected override Arguments Arguments {
6831                         get {
6832                                 return arguments;
6833                         }
6834                         set {
6835                                 arguments = value;
6836                         }
6837                 }
6838
6839                 protected override TypeSpec DeclaringType {
6840                         get {
6841                                 return best_candidate.DeclaringType;
6842                         }
6843                 }
6844
6845                 public override string Name {
6846                         get {
6847                                 return best_candidate.Name;
6848                         }
6849                 }
6850
6851                 public bool IsAutoPropertyAccess {
6852                         get {
6853                                 var prop = best_candidate.MemberDefinition as Property;
6854                                 return prop != null && prop.BackingField != null;
6855                         }
6856                 }
6857
6858                 public override bool IsInstance {
6859                         get {
6860                                 return !IsStatic;
6861                         }
6862                 }
6863
6864                 public override bool IsStatic {
6865                         get {
6866                                 return best_candidate.IsStatic;
6867                         }
6868                 }
6869
6870                 public override string KindName {
6871                         get { return "property"; }
6872                 }
6873
6874                 public PropertySpec PropertyInfo {
6875                         get {
6876                                 return best_candidate;
6877                         }
6878                 }
6879
6880                 #endregion
6881
6882                 public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
6883                 {
6884                         if (best_candidate == null || !(best_candidate.IsStatic || InstanceExpression is This))
6885                                 return null;
6886
6887                         var args_count = arguments == null ? 0 : arguments.Count;
6888                         if (args_count != body.Parameters.Count && args_count == 0)
6889                                 return null;
6890
6891                         var mg = MethodGroupExpr.CreatePredefined (best_candidate.Get, DeclaringType, loc);
6892                         mg.InstanceExpression = InstanceExpression;
6893
6894                         return mg;
6895                 }
6896
6897                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
6898                 {
6899                         return new PropertyExpr (spec, loc) {
6900                                 Getter = spec.Get,
6901                                 Setter = spec.Set
6902                         };
6903                 }
6904
6905                 public override Expression CreateExpressionTree (ResolveContext ec)
6906                 {
6907                         if (ConditionalAccess) {
6908                                 Error_NullShortCircuitInsideExpressionTree (ec);
6909                         }
6910
6911                         Arguments args;
6912                         if (IsSingleDimensionalArrayLength ()) {
6913                                 args = new Arguments (1);
6914                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6915                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
6916                         }
6917
6918                         args = new Arguments (2);
6919                         if (InstanceExpression == null)
6920                                 args.Add (new Argument (new NullLiteral (loc)));
6921                         else
6922                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6923                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
6924                         return CreateExpressionFactoryCall (ec, "Property", args);
6925                 }
6926
6927                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
6928                 {
6929                         DoResolveLValue (rc, null);
6930                         return new TypeOfMethod (Setter, loc);
6931                 }
6932
6933                 public override string GetSignatureForError ()
6934                 {
6935                         return best_candidate.GetSignatureForError ();
6936                 }
6937
6938                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6939                 {
6940 #if STATIC
6941                         return base.MakeExpression (ctx);
6942 #else
6943                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
6944 #endif
6945                 }
6946
6947                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6948                 {
6949 #if STATIC
6950                         return base.MakeExpression (ctx);
6951 #else
6952                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
6953 #endif
6954                 }
6955
6956                 void Error_PropertyNotValid (ResolveContext ec)
6957                 {
6958                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
6959                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
6960                                 GetSignatureForError ());
6961                 }
6962
6963                 bool IsSingleDimensionalArrayLength ()
6964                 {
6965                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
6966                                 return false;
6967
6968                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
6969                         return ac != null && ac.Rank == 1;
6970                 }
6971
6972                 public override void Emit (EmitContext ec, bool leave_copy)
6973                 {
6974                         //
6975                         // Special case: length of single dimension array property is turned into ldlen
6976                         //
6977                         if (IsSingleDimensionalArrayLength ()) {
6978                                 if (conditional_access_receiver) {
6979                                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
6980                                 }
6981
6982                                 EmitInstance (ec, false);
6983
6984                                 ec.Emit (OpCodes.Ldlen);
6985                                 ec.Emit (OpCodes.Conv_I4);
6986
6987                                 if (conditional_access_receiver) {
6988                                         ec.CloseConditionalAccess (type);
6989                                 }
6990
6991                                 return;
6992                         }
6993
6994                         base.Emit (ec, leave_copy);
6995                 }
6996
6997                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6998                 {
6999                         if (backing_field != null) {
7000                                 backing_field.EmitAssign (ec, source, false, false);
7001                                 return;
7002                         }
7003
7004                         Arguments args;
7005                         LocalTemporary await_source_arg = null;
7006
7007                         if (isCompound && !(source is DynamicExpressionStatement)) {
7008                                 emitting_compound_assignment = true;
7009                                 source.Emit (ec);
7010
7011                                 if (has_await_arguments) {
7012                                         await_source_arg = new LocalTemporary (Type);
7013                                         await_source_arg.Store (ec);
7014
7015                                         args = new Arguments (1);
7016                                         args.Add (new Argument (await_source_arg));
7017
7018                                         if (leave_copy) {
7019                                                 temp = await_source_arg;
7020                                         }
7021
7022                                         has_await_arguments = false;
7023                                 } else {
7024                                         args = null;
7025
7026                                         if (leave_copy) {
7027                                                 ec.Emit (OpCodes.Dup);
7028                                                 temp = new LocalTemporary (this.Type);
7029                                                 temp.Store (ec);
7030                                         }
7031                                 }
7032                         } else {
7033                                 args = arguments ?? new Arguments (1);
7034
7035                                 if (leave_copy) {
7036                                         source.Emit (ec);
7037                                         temp = new LocalTemporary (this.Type);
7038                                         temp.Store (ec);
7039                                         args.Add (new Argument (temp));
7040                                 } else {
7041                                         args.Add (new Argument (source));
7042                                 }
7043                         }
7044
7045                         emitting_compound_assignment = false;
7046
7047                         var call = new CallEmitter ();
7048                         call.InstanceExpression = InstanceExpression;
7049                         if (args == null)
7050                                 call.InstanceExpressionOnStack = true;
7051
7052                         if (ConditionalAccess) {
7053                                 call.ConditionalAccess = true;
7054                         }
7055
7056                         if (leave_copy)
7057                                 call.Emit (ec, Setter, args, loc);
7058                         else
7059                                 call.EmitStatement (ec, Setter, args, loc);
7060
7061                         if (temp != null) {
7062                                 temp.Emit (ec);
7063                                 temp.Release (ec);
7064                         }
7065
7066                         if (await_source_arg != null) {
7067                                 await_source_arg.Release (ec);
7068                         }
7069                 }
7070
7071                 public override void FlowAnalysis (FlowAnalysisContext fc)
7072                 {
7073                         var prop = best_candidate.MemberDefinition as Property;
7074                         if (prop != null && prop.BackingField != null) {
7075                                 var var = InstanceExpression as IVariableReference;
7076                                 if (var != null) {
7077                                         var vi = var.VariableInfo;
7078                                         if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, prop.BackingField.Name)) {
7079                                                 fc.Report.Error (8079, loc, "Use of possibly unassigned auto-implemented property `{0}'", Name);
7080                                                 return;
7081                                         }
7082
7083                                         if (TypeSpec.IsValueType (InstanceExpression.Type) && InstanceExpression is VariableReference)
7084                                                 return;
7085                                 }
7086                         }
7087
7088                         var da = conditional_access_receiver ? fc.BranchDefiniteAssignment () : null;
7089
7090                         base.FlowAnalysis (fc);
7091
7092                         if (conditional_access_receiver)
7093                                 fc.DefiniteAssignment = da;
7094                 }
7095
7096                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
7097                 {
7098                         eclass = ExprClass.PropertyAccess;
7099
7100                         if (best_candidate.IsNotCSharpCompatible) {
7101                                 Error_PropertyNotValid (rc);
7102                         }
7103
7104                         ResolveInstanceExpression (rc, right_side);
7105
7106                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
7107                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
7108                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
7109                                 if (p != null) {
7110                                         type = p.MemberType;
7111                                 }
7112                         }
7113
7114                         DoBestMemberChecks (rc, best_candidate);
7115
7116                         // Handling of com-imported properties with any number of default property parameters
7117                         if (best_candidate.HasGet && !best_candidate.Get.Parameters.IsEmpty) {
7118                                 var p = best_candidate.Get.Parameters;
7119                                 arguments = new Arguments (p.Count);
7120                                 for (int i = 0; i < p.Count; ++i) {
7121                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
7122                                 }
7123                         } else if (best_candidate.HasSet && best_candidate.Set.Parameters.Count > 1) {
7124                                 var p = best_candidate.Set.Parameters;
7125                                 arguments = new Arguments (p.Count - 1);
7126                                 for (int i = 0; i < p.Count - 1; ++i) {
7127                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
7128                                 }
7129                         }
7130
7131                         return this;
7132                 }
7133
7134                 protected override bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7135                 {
7136                         if (!rc.HasSet (ResolveContext.Options.ConstructorScope))
7137                                 return false;
7138
7139                         var prop = best_candidate.MemberDefinition as Property;
7140                         if (prop == null || prop.Parent.PartialContainer != rc.CurrentMemberDefinition.Parent.PartialContainer) {
7141                                 var ps = MemberCache.FindMember (rc.CurrentType, MemberFilter.Property (best_candidate.Name, best_candidate.MemberType), BindingRestriction.DeclaredOnly) as PropertySpec;
7142                                 if (ps == null)
7143                                         return false;
7144
7145                                 prop = (Property)ps.MemberDefinition;
7146                         }
7147
7148                         var spec = prop.BackingField;
7149                         if (spec == null)
7150                                 return false;
7151
7152                         if (rc.IsStatic != spec.IsStatic)
7153                                 return false;
7154
7155                         if (!spec.IsStatic && (!(InstanceExpression is This) || InstanceExpression is BaseThis))
7156                                 return false;
7157
7158                         backing_field = new FieldExpr (prop.BackingField, loc);
7159                         backing_field.ResolveLValue (rc, rhs);
7160                         return true;
7161                 }
7162
7163                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
7164                 {
7165                         if (!best_candidate.IsAccessible (rc))
7166                                 ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), expr.Location);
7167
7168                         best_candidate.CheckObsoleteness (rc, expr.Location);
7169                 }
7170
7171                 public void SetBackingFieldAssigned (FlowAnalysisContext fc)
7172                 {
7173                         if (backing_field != null) {
7174                                 backing_field.SetFieldAssigned (fc);
7175                                 return;
7176                         }
7177
7178                         if (!IsAutoPropertyAccess)
7179                                 return;
7180
7181                         var prop = best_candidate.MemberDefinition as Property;
7182                         if (prop != null && prop.BackingField != null) {
7183                                 bool lvalue_instance = best_candidate.DeclaringType.IsStruct;
7184                                 if (lvalue_instance) {
7185                                         var var = InstanceExpression as IVariableReference;
7186                                         if (var != null && var.VariableInfo != null) {
7187                                                 fc.SetStructFieldAssigned (var.VariableInfo, prop.BackingField.Name);
7188                                         }
7189                                 }
7190                         }
7191                 }
7192
7193                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7194                 {
7195                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
7196                 }
7197         }
7198
7199         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
7200         {
7201                 // getter and setter can be different for base calls
7202                 MethodSpec getter, setter;
7203                 protected T best_candidate;
7204
7205                 protected LocalTemporary temp;
7206                 protected bool emitting_compound_assignment;
7207                 protected bool has_await_arguments;
7208
7209                 protected PropertyOrIndexerExpr (Location l)
7210                 {
7211                         loc = l;
7212                 }
7213
7214                 #region Properties
7215
7216                 protected abstract Arguments Arguments { get; set; }
7217
7218                 public MethodSpec Getter {
7219                         get {
7220                                 return getter;
7221                         }
7222                         set {
7223                                 getter = value;
7224                         }
7225                 }
7226
7227                 public MethodSpec Setter {
7228                         get {
7229                                 return setter;
7230                         }
7231                         set {
7232                                 setter = value;
7233                         }
7234                 }
7235
7236                 #endregion
7237
7238                 protected override Expression DoResolve (ResolveContext ec)
7239                 {
7240                         if (eclass == ExprClass.Unresolved) {
7241                                 ResolveConditionalAccessReceiver (ec);
7242
7243                                 var expr = OverloadResolve (ec, null);
7244                                 if (expr == null)
7245                                         return null;
7246
7247                                 if (expr != this) {
7248                                         using (ec.With (ResolveContext.Options.DontSetConditionalAccessReceiver, conditional_access_receiver))
7249                                                 return expr.Resolve (ec);
7250                                 }
7251
7252                                 if (conditional_access_receiver) {
7253                                         type = LiftMemberType (ec, type);
7254                                 }
7255                         }
7256
7257                         if (!ResolveGetter (ec))
7258                                 return null;
7259
7260                         return this;
7261                 }
7262
7263                 public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
7264                 {
7265                         if (HasConditionalAccess ())
7266                                 Error_NullPropagatingLValue (rc);
7267
7268                         if (right_side == EmptyExpression.OutAccess) {
7269                                 // TODO: best_candidate can be null at this point
7270                                 INamedBlockVariable variable = null;
7271                                 if (best_candidate != null && rc.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, rc.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
7272                                         rc.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
7273                                                 best_candidate.Name);
7274                                 } else {
7275                                         right_side.DoResolveLValue (rc, this);
7276                                 }
7277                                 return null;
7278                         }
7279
7280                         if (eclass == ExprClass.Unresolved) {
7281                                 var expr = OverloadResolve (rc, right_side);
7282                                 if (expr == null)
7283                                         return null;
7284
7285                                 if (expr != this)
7286                                         return expr.ResolveLValue (rc, right_side);
7287                         } else {
7288                                 ResolveInstanceExpression (rc, right_side);
7289                         }
7290
7291                         if (!best_candidate.HasSet) {
7292                                 if (ResolveAutopropertyAssignment (rc, right_side))
7293                                         return this;
7294
7295                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
7296                                         GetSignatureForError ());
7297                                 return null;
7298                         }
7299
7300                         if (!best_candidate.Set.IsAccessible (rc) || !best_candidate.Set.DeclaringType.IsAccessible (rc)) {
7301                                 if (best_candidate.HasDifferentAccessibility) {
7302                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7303                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
7304                                                 GetSignatureForError ());
7305                                 } else {
7306                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7307                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
7308                                 }
7309                         }
7310
7311                         if (best_candidate.HasDifferentAccessibility)
7312                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
7313
7314                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
7315                         return this;
7316                 }
7317
7318                 void EmitConditionalAccess (EmitContext ec, ref CallEmitter call, MethodSpec method, Arguments arguments)
7319                 {
7320                         var ca = ec.ConditionalAccess;
7321                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7322
7323                         call.Emit (ec, method, arguments, loc);
7324
7325                         ec.CloseConditionalAccess (method.ReturnType != type && type.IsNullableType ? type : null);
7326                         ec.ConditionalAccess = ca;
7327                 }
7328
7329                 //
7330                 // Implements the IAssignMethod interface for assignments
7331                 //
7332                 public virtual void Emit (EmitContext ec, bool leave_copy)
7333                 {
7334                         var call = new CallEmitter ();
7335                         call.ConditionalAccess = ConditionalAccess;
7336                         call.InstanceExpression = InstanceExpression;
7337                         if (has_await_arguments)
7338                                 call.HasAwaitArguments = true;
7339                         else
7340                                 call.DuplicateArguments = emitting_compound_assignment;
7341
7342                         if (conditional_access_receiver)
7343                                 EmitConditionalAccess (ec, ref call, Getter, Arguments);
7344                         else
7345                                 call.Emit (ec, Getter, Arguments, loc);
7346
7347                         if (call.HasAwaitArguments) {
7348                                 InstanceExpression = call.InstanceExpression;
7349                                 Arguments = call.EmittedArguments;
7350                                 has_await_arguments = true;
7351                         }
7352
7353                         if (leave_copy) {
7354                                 ec.Emit (OpCodes.Dup);
7355                                 temp = new LocalTemporary (Type);
7356                                 temp.Store (ec);
7357                         }
7358                 }
7359
7360                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
7361
7362                 public override void Emit (EmitContext ec)
7363                 {
7364                         Emit (ec, false);
7365                 }
7366
7367                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
7368                 {
7369                         has_await_arguments = true;
7370                         Emit (ec, false);
7371                         return null;
7372                 }
7373
7374                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
7375
7376                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
7377
7378                 bool ResolveGetter (ResolveContext rc)
7379                 {
7380                         if (!best_candidate.HasGet) {
7381                                 if (InstanceExpression != EmptyExpression.Null) {
7382                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
7383                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
7384                                                 best_candidate.GetSignatureForError ());
7385                                         return false;
7386                                 }
7387                         } else if (!best_candidate.Get.IsAccessible (rc) || !best_candidate.Get.DeclaringType.IsAccessible (rc)) {
7388                                 if (best_candidate.HasDifferentAccessibility) {
7389                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7390                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
7391                                                 TypeManager.CSharpSignature (best_candidate));
7392                                 } else {
7393                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7394                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
7395                                 }
7396                         }
7397
7398                         if (best_candidate.HasDifferentAccessibility) {
7399                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
7400                         }
7401
7402                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
7403                         return true;
7404                 }
7405
7406                 protected virtual bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7407                 {
7408                         return false;
7409                 }
7410         }
7411
7412         /// <summary>
7413         ///   Fully resolved expression that evaluates to an Event
7414         /// </summary>
7415         public class EventExpr : MemberExpr, IAssignMethod
7416         {
7417                 readonly EventSpec spec;
7418                 MethodSpec op;
7419
7420                 public EventExpr (EventSpec spec, Location loc)
7421                 {
7422                         this.spec = spec;
7423                         this.loc = loc;
7424                 }
7425
7426                 #region Properties
7427
7428                 protected override TypeSpec DeclaringType {
7429                         get {
7430                                 return spec.DeclaringType;
7431                         }
7432                 }
7433
7434                 public override string Name {
7435                         get {
7436                                 return spec.Name;
7437                         }
7438                 }
7439
7440                 public override bool IsInstance {
7441                         get {
7442                                 return !spec.IsStatic;
7443                         }
7444                 }
7445
7446                 public override bool IsStatic {
7447                         get {
7448                                 return spec.IsStatic;
7449                         }
7450                 }
7451
7452                 public override string KindName {
7453                         get { return "event"; }
7454                 }
7455
7456                 public MethodSpec Operator {
7457                         get {
7458                                 return op;
7459                         }
7460                 }
7461
7462                 #endregion
7463
7464                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
7465                 {
7466                         //
7467                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
7468                         //
7469                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7470                                 if (spec.BackingField != null &&
7471                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
7472
7473                                         spec.MemberDefinition.SetIsUsed ();
7474
7475                                         spec.CheckObsoleteness (ec, loc);
7476
7477                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
7478                                                 Error_AssignmentEventOnly (ec);
7479
7480                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
7481
7482                                         InstanceExpression = null;
7483
7484                                         return ml.ResolveMemberAccess (ec, left, original);
7485                                 }
7486                         }
7487
7488                         return base.ResolveMemberAccess (ec, left, original);
7489                 }
7490
7491                 public override Expression CreateExpressionTree (ResolveContext ec)
7492                 {
7493                         throw new NotSupportedException ("ET");
7494                 }
7495
7496                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7497                 {
7498                         if (right_side == EmptyExpression.EventAddition) {
7499                                 op = spec.AccessorAdd;
7500                         } else if (right_side == EmptyExpression.EventSubtraction) {
7501                                 op = spec.AccessorRemove;
7502                         }
7503
7504                         if (op == null) {
7505                                 Error_AssignmentEventOnly (ec);
7506                                 return null;
7507                         }
7508
7509                         if (HasConditionalAccess ())
7510                                 Error_NullPropagatingLValue (ec);
7511
7512                         op = CandidateToBaseOverride (ec, op);
7513                         return this;
7514                 }
7515
7516                 protected override Expression DoResolve (ResolveContext ec)
7517                 {
7518                         eclass = ExprClass.EventAccess;
7519                         type = spec.MemberType;
7520
7521                         ResolveInstanceExpression (ec, null);
7522
7523                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7524                                 Error_AssignmentEventOnly (ec);
7525                         }
7526
7527                         DoBestMemberChecks (ec, spec);
7528                         return this;
7529                 }
7530
7531                 public override void Emit (EmitContext ec)
7532                 {
7533                         throw new NotSupportedException ();
7534                         //Error_CannotAssign ();
7535                 }
7536
7537                 #region IAssignMethod Members
7538
7539                 public void Emit (EmitContext ec, bool leave_copy)
7540                 {
7541                         throw new NotImplementedException ();
7542                 }
7543
7544                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
7545                 {
7546                         if (leave_copy || !isCompound)
7547                                 throw new NotImplementedException ("EventExpr::EmitAssign");
7548
7549                         Arguments args = new Arguments (1);
7550                         args.Add (new Argument (source));
7551
7552                         // TODO: Wrong, needs receiver
7553 //                      if (NullShortCircuit) {
7554 //                              ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7555 //                      }
7556
7557                         var call = new CallEmitter ();
7558                         call.InstanceExpression = InstanceExpression;
7559                         call.ConditionalAccess = ConditionalAccess;
7560                         call.EmitStatement (ec, op, args, loc);
7561
7562 //                      if (NullShortCircuit)
7563 //                              ec.CloseConditionalAccess (null);
7564                 }
7565
7566                 #endregion
7567
7568                 void Error_AssignmentEventOnly (ResolveContext ec)
7569                 {
7570                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
7571                                 ec.Report.Error (79, loc,
7572                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
7573                                         GetSignatureForError ());
7574                         } else {
7575                                 ec.Report.Error (70, loc,
7576                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
7577                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
7578                         }
7579                 }
7580
7581                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
7582                 {
7583                         name = name.Substring (0, name.LastIndexOf ('.'));
7584                         base.Error_CannotCallAbstractBase (rc, name);
7585                 }
7586
7587                 public override string GetSignatureForError ()
7588                 {
7589                         return TypeManager.CSharpSignature (spec);
7590                 }
7591
7592                 public override void ResolveNameOf (ResolveContext rc, ATypeNameExpression expr)
7593                 {
7594                         spec.CheckObsoleteness (rc, expr.Location);
7595                 }
7596
7597                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7598                 {
7599                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
7600                 }
7601         }
7602
7603         public class TemporaryVariableReference : VariableReference
7604         {
7605                 public class Declarator : Statement
7606                 {
7607                         TemporaryVariableReference variable;
7608
7609                         public Declarator (TemporaryVariableReference variable)
7610                         {
7611                                 this.variable = variable;
7612                                 loc = variable.loc;
7613                         }
7614
7615                         protected override void DoEmit (EmitContext ec)
7616                         {
7617                                 variable.li.CreateBuilder (ec);
7618                         }
7619
7620                         public override void Emit (EmitContext ec)
7621                         {
7622                                 // Don't create sequence point
7623                                 DoEmit (ec);
7624                         }
7625
7626                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7627                         {
7628                                 return false;
7629                         }
7630
7631                         protected override void CloneTo (CloneContext clonectx, Statement target)
7632                         {
7633                                 // Nothing
7634                         }
7635                 }
7636
7637                 LocalVariable li;
7638
7639                 public TemporaryVariableReference (LocalVariable li, Location loc)
7640                 {
7641                         this.li = li;
7642                         this.type = li.Type;
7643                         this.loc = loc;
7644                 }
7645
7646                 public override bool IsLockedByStatement {
7647                         get {
7648                                 return false;
7649                         }
7650                         set {
7651                         }
7652                 }
7653
7654                 public LocalVariable LocalInfo {
7655                     get {
7656                         return li;
7657                     }
7658                 }
7659
7660                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc, bool writeToSymbolFile = false)
7661                 {
7662                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc, writeToSymbolFile);
7663                         return new TemporaryVariableReference (li, loc);
7664                 }
7665
7666                 protected override Expression DoResolve (ResolveContext ec)
7667                 {
7668                         eclass = ExprClass.Variable;
7669
7670                         //
7671                         // Don't capture temporary variables except when using
7672                         // state machine redirection and block yields
7673                         //
7674                         if (ec.CurrentAnonymousMethod is StateMachineInitializer &&
7675                                 (ec.CurrentBlock.Explicit.HasYield || ec.CurrentBlock.Explicit.HasAwait) &&
7676                                 ec.IsVariableCapturingRequired) {
7677                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
7678                                 storey.CaptureLocalVariable (ec, li);
7679                         }
7680
7681                         return this;
7682                 }
7683
7684                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7685                 {
7686                         return Resolve (ec);
7687                 }
7688
7689                 public override void Emit (EmitContext ec)
7690                 {
7691                         li.CreateBuilder (ec);
7692
7693                         Emit (ec, false);
7694                 }
7695
7696                 public void EmitAssign (EmitContext ec, Expression source)
7697                 {
7698                         li.CreateBuilder (ec);
7699
7700                         EmitAssign (ec, source, false, false);
7701                 }
7702
7703                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
7704                 {
7705                         return li.HoistedVariant;
7706                 }
7707
7708                 public override bool IsFixed {
7709                         get { return true; }
7710                 }
7711
7712                 public override bool IsRef {
7713                         get { return false; }
7714                 }
7715
7716                 public override string Name {
7717                         get { throw new NotImplementedException (); }
7718                 }
7719
7720                 public override void SetHasAddressTaken ()
7721                 {
7722                         throw new NotImplementedException ();
7723                 }
7724
7725                 protected override ILocalVariable Variable {
7726                         get { return li; }
7727                 }
7728
7729                 public override VariableInfo VariableInfo {
7730                         get { return null; }
7731                 }
7732         }
7733
7734         ///
7735         /// Handles `var' contextual keyword; var becomes a keyword only
7736         /// if no type called var exists in a variable scope
7737         ///
7738         class VarExpr : SimpleName
7739         {
7740                 public VarExpr (Location loc)
7741                         : base ("var", loc)
7742                 {
7743                 }
7744
7745                 public bool InferType (ResolveContext ec, Expression right_side)
7746                 {
7747                         if (type != null)
7748                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
7749
7750                         type = right_side.Type;
7751                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
7752                                 ec.Report.Error (815, loc,
7753                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
7754                                         type.GetSignatureForError ());
7755                                 type = InternalType.ErrorType;
7756                                 return false;
7757                         }
7758
7759                         eclass = ExprClass.Variable;
7760                         return true;
7761                 }
7762
7763                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
7764                 {
7765                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
7766                                 base.Error_TypeOrNamespaceNotFound (ec);
7767                         else
7768                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
7769                 }
7770         }
7771 }