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@seznam.cz)
   7 //
   8 // Copyright 2001, 2002, 2003 Ximian, Inc.
   9 // Copyright 2003-2008 Novell, Inc.
  10 // Copyright 2011 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                 public ExprClass eclass;
 131                 protected TypeSpec type;
 132                 protected Location loc;
 133
 134                 public TypeSpec Type {
 135                         get { return type; }
 136                         set { type = value; }
 137                 }
 138
 139                 public virtual bool IsSideEffectFree {
 140                         get {
 141                                 return false;
 142                         }
 143                 }
 144
 145                 public Location Location {
 146                         get { return loc; }
 147                 }
 148
 149                 public virtual bool IsNull {
 150                         get {
 151                                 return false;
 152                         }
 153                 }
 154
 155                 //
 156                 // Returns true when the expression during Emit phase breaks stack
 157                 // by using await expression
 158                 //
 159                 public virtual bool ContainsEmitWithAwait ()
 160                 {
 161                         return false;
 162                 }
 163
 164                 /// <summary>
 165                 ///   Performs semantic analysis on the Expression
 166                 /// </summary>
 167                 ///
 168                 /// <remarks>
 169                 ///   The Resolve method is invoked to perform the semantic analysis
 170                 ///   on the node.
 171                 ///
 172                 ///   The return value is an expression (it can be the
 173                 ///   same expression in some cases) or a new
 174                 ///   expression that better represents this node.
 175                 ///
 176                 ///   For example, optimizations of Unary (LiteralInt)
 177                 ///   would return a new LiteralInt with a negated
 178                 ///   value.
 179                 ///
 180                 ///   If there is an error during semantic analysis,
 181                 ///   then an error should be reported (using Report)
 182                 ///   and a null value should be returned.
 183                 ///
 184                 ///   There are two side effects expected from calling
 185                 ///   Resolve(): the the field variable "eclass" should
 186                 ///   be set to any value of the enumeration
 187                 ///   `ExprClass' and the type variable should be set
 188                 ///   to a valid type (this is the type of the
 189                 ///   expression).
 190                 /// </remarks>
 191                 protected abstract Expression DoResolve (ResolveContext rc);
 192
 193                 public virtual Expression DoResolveLValue (ResolveContext rc, Expression right_side)
 194                 {
 195                         return null;
 196                 }
 197
 198                 //
 199                 // This is used if the expression should be resolved as a type or namespace name.
 200                 // the default implementation fails.
 201                 //
 202                 public virtual TypeSpec ResolveAsType (IMemberContext mc)
 203                 {
 204                         ResolveContext ec = new ResolveContext (mc);
 205                         Expression e = Resolve (ec);
 206                         if (e != null)
 207                                 e.Error_UnexpectedKind (ec, ResolveFlags.Type, loc);
 208
 209                         return null;
 210                 }
 211
 212                 public static void ErrorIsInaccesible (IMemberContext rc, string member, Location loc)
 213                 {
 214                         rc.Module.Compiler.Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", member);
 215                 }
 216
 217                 public void Error_ExpressionMustBeConstant (ResolveContext rc, Location loc, string e_name)
 218                 {
 219                         rc.Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
 220                 }
 221
 222                 public void Error_ConstantCanBeInitializedWithNullOnly (ResolveContext rc, TypeSpec type, Location loc, string name)
 223                 {
 224                         rc.Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
 225                                 name, TypeManager.CSharpName (type));
 226                 }
 227
 228                 public static void Error_InvalidExpressionStatement (Report Report, Location loc)
 229                 {
 230                         Report.Error (201, loc, "Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement");
 231                 }
 232
 233                 public void Error_InvalidExpressionStatement (BlockContext ec)
 234                 {
 235                         Error_InvalidExpressionStatement (ec.Report, loc);
 236                 }
 237
 238                 public static void Error_VoidInvalidInTheContext (Location loc, Report Report)
 239                 {
 240                         Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
 241                 }
 242
 243                 public virtual void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
 244                 {
 245                         Error_ValueCannotBeConvertedCore (ec, loc, target, expl);
 246                 }
 247
 248                 protected void Error_ValueCannotBeConvertedCore (ResolveContext ec, Location loc, TypeSpec target, bool expl)
 249                 {
 250                         // The error was already reported as CS1660
 251                         if (type == InternalType.AnonymousMethod || type == InternalType.ErrorType)
 252                                 return;
 253
 254                         string from_type = type.GetSignatureForError ();
 255                         string to_type = target.GetSignatureForError ();
 256                         if (from_type == to_type) {
 257                                 from_type = type.GetSignatureForErrorIncludingAssemblyName ();
 258                                 to_type = target.GetSignatureForErrorIncludingAssemblyName ();
 259                         }
 260
 261                         if (expl) {
 262                                 ec.Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
 263                                         from_type, to_type);
 264                                 return;
 265                         }
 266
 267                         ec.Report.DisableReporting ();
 268                         bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
 269                         ec.Report.EnableReporting ();
 270
 271                         if (expl_exists) {
 272                                 ec.Report.Error (266, loc,
 273                                         "Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
 274                                         from_type, to_type);
 275                         } else {
 276                                 ec.Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
 277                                         from_type, to_type);
 278                         }
 279                 }
 280
 281                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, MemberSpec member, int arity, Location loc)
 282                 {
 283                         // Better message for possible generic expressions
 284                         if (member != null && (member.Kind & MemberKind.GenericMask) != 0) {
 285                                 var report = context.Module.Compiler.Report;
 286                                 report.SymbolRelatedToPreviousError (member);
 287                                 if (member is TypeSpec)
 288                                         member = ((TypeSpec) member).GetDefinition ();
 289                                 else
 290                                         member = ((MethodSpec) member).GetGenericMethodDefinition ();
 291
 292                                 string name = member.Kind == MemberKind.Method ? "method" : "type";
 293                                 if (member.IsGeneric) {
 294                                         report.Error (305, loc, "Using the generic {0} `{1}' requires `{2}' type argument(s)",
 295                                                 name, member.GetSignatureForError (), member.Arity.ToString ());
 296                                 } else {
 297                                         report.Error (308, loc, "The non-generic {0} `{1}' cannot be used with the type arguments",
 298                                                 name, member.GetSignatureForError ());
 299                                 }
 300                         } else {
 301                                 Error_TypeArgumentsCannotBeUsed (context, ExprClassName, GetSignatureForError (), loc);
 302                         }
 303                 }
 304
 305                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, string exprType, string name, Location loc)
 306                 {
 307                         context.Module.Compiler.Report.Error (307, loc, "The {0} `{1}' cannot be used with type arguments",
 308                                 exprType, name);
 309                 }
 310
 311                 protected virtual void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
 312                 {
 313                         Error_TypeDoesNotContainDefinition (ec, loc, type, name);
 314                 }
 315
 316                 public static void Error_TypeDoesNotContainDefinition (ResolveContext ec, Location loc, TypeSpec type, string name)
 317                 {
 318                         ec.Report.SymbolRelatedToPreviousError (type);
 319                         ec.Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
 320                                 TypeManager.CSharpName (type), name);
 321                 }
 322
 323                 public virtual void Error_ValueAssignment (ResolveContext rc, Expression rhs)
 324                 {
 325                         if (rhs == EmptyExpression.LValueMemberAccess || rhs == EmptyExpression.LValueMemberOutAccess) {
 326                                 rc.Report.SymbolRelatedToPreviousError (type);
 327                                 if (rc.CurrentInitializerVariable != null) {
 328                                         rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
 329                                                 type.GetSignatureForError (), GetSignatureForError ());
 330                                 } else {
 331                                         rc.Report.Error (1612, loc, "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
 332                                                 GetSignatureForError ());
 333                                 }
 334                         } else {
 335                                 rc.Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
 336                         }
 337                 }
 338
 339                 protected void Error_VoidPointerOperation (ResolveContext rc)
 340                 {
 341                         rc.Report.Error (242, loc, "The operation in question is undefined on void pointers");
 342                 }
 343
 344                 public ResolveFlags ExprClassToResolveFlags {
 345                         get {
 346                                 switch (eclass) {
 347                                 case ExprClass.Type:
 348                                 case ExprClass.Namespace:
 349                                         return ResolveFlags.Type;
 350
 351                                 case ExprClass.MethodGroup:
 352                                         return ResolveFlags.MethodGroup;
 353
 354                                 case ExprClass.TypeParameter:
 355                                         return ResolveFlags.TypeParameter;
 356
 357                                 case ExprClass.Value:
 358                                 case ExprClass.Variable:
 359                                 case ExprClass.PropertyAccess:
 360                                 case ExprClass.EventAccess:
 361                                 case ExprClass.IndexerAccess:
 362                                         return ResolveFlags.VariableOrValue;
 363
 364                                 default:
 365                                         throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
 366                                 }
 367                         }
 368                 }
 369
 370                 public virtual string GetSignatureForError ()
 371                 {
 372                         return type.GetDefinition ().GetSignatureForError ();
 373                 }
 374
 375                 /// <summary>
 376                 ///   Resolves an expression and performs semantic analysis on it.
 377                 /// </summary>
 378                 ///
 379                 /// <remarks>
 380                 ///   Currently Resolve wraps DoResolve to perform sanity
 381                 ///   checking and assertion checking on what we expect from Resolve.
 382                 /// </remarks>
 383                 public Expression Resolve (ResolveContext ec, ResolveFlags flags)
 384                 {
 385                         if (eclass != ExprClass.Unresolved)
 386                                 return this;
 387
 388                         Expression e;
 389                         try {
 390                                 e = DoResolve (ec);
 391
 392                                 if (e == null)
 393                                         return null;
 394
 395                                 if ((flags & e.ExprClassToResolveFlags) == 0) {
 396                                         e.Error_UnexpectedKind (ec, flags, loc);
 397                                         return null;
 398                                 }
 399
 400                                 if (e.type == null)
 401                                         throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());
 402
 403                                 return e;
 404                         } catch (Exception ex) {
 405                                 if (loc.IsNull || ec.Module.Compiler.Settings.DebugFlags > 0 || ex is CompletionResult || ec.Report.IsDisabled || ex is FatalException)
 406                                         throw;
 407
 408                                 ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
 409                                 return ErrorExpression.Instance;        // TODO: Add location
 410                         }
 411                 }
 412
 413                 /// <summary>
 414                 ///   Resolves an expression and performs semantic analysis on it.
 415                 /// </summary>
 416                 public Expression Resolve (ResolveContext rc)
 417                 {
 418                         return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
 419                 }
 420
 421                 /// <summary>
 422                 ///   Resolves an expression for LValue assignment
 423                 /// </summary>
 424                 ///
 425                 /// <remarks>
 426                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 427                 ///   checking and assertion checking on what we expect from Resolve
 428                 /// </remarks>
 429                 public Expression ResolveLValue (ResolveContext ec, Expression right_side)
 430                 {
 431                         int errors = ec.Report.Errors;
 432                         bool out_access = right_side == EmptyExpression.OutAccess;
 433
 434                         Expression e = DoResolveLValue (ec, right_side);
 435
 436                         if (e != null && out_access && !(e is IMemoryLocation)) {
 437                                 // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
 438                                 //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,
 439
 440                                 //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
 441                                 //                                e.GetType () + " " + e.GetSignatureForError ());
 442                                 e = null;
 443                         }
 444
 445                         if (e == null) {
 446                                 if (errors == ec.Report.Errors) {
 447                                         if (out_access)
 448                                                 ec.Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
 449                                         else
 450                                                 Error_ValueAssignment (ec, right_side);
 451                                 }
 452                                 return null;
 453                         }
 454
 455                         if (e.eclass == ExprClass.Unresolved)
 456                                 throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");
 457
 458                         if ((e.type == null) && !(e is GenericTypeExpr))
 459                                 throw new Exception ("Expression " + e + " did not set its type after Resolve");
 460
 461                         return e;
 462                 }
 463
 464                 public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
 465                 {
 466                         rc.Module.Compiler.Report.Error (182, loc,
 467                                 "An attribute argument must be a constant expression, typeof expression or array creation expression");
 468                 }
 469
 470                 /// <summary>
 471                 ///   Emits the code for the expression
 472                 /// </summary>
 473                 ///
 474                 /// <remarks>
 475                 ///   The Emit method is invoked to generate the code
 476                 ///   for the expression.
 477                 /// </remarks>
 478                 public abstract void Emit (EmitContext ec);
 479
 480
 481                 // Emit code to branch to @target if this expression is equivalent to @on_true.
 482                 // The default implementation is to emit the value, and then emit a brtrue or brfalse.
 483                 // Subclasses can provide more efficient implementations, but those MUST be equivalent,
 484                 // including the use of conditional branches.  Note also that a branch MUST be emitted
 485                 public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
 486                 {
 487                         Emit (ec);
 488                         ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
 489                 }
 490
 491                 // Emit this expression for its side effects, not for its value.
 492                 // The default implementation is to emit the value, and then throw it away.
 493                 // Subclasses can provide more efficient implementations, but those MUST be equivalent
 494                 public virtual void EmitSideEffect (EmitContext ec)
 495                 {
 496                         Emit (ec);
 497                         ec.Emit (OpCodes.Pop);
 498                 }
 499
 500                 //
 501                 // Emits the expression into temporary field variable. The method
 502                 // should be used for await expressions only
 503                 //
 504                 public virtual Expression EmitToField (EmitContext ec)
 505                 {
 506                         //
 507                         // This is the await prepare Emit method. When emitting code like
 508                         // a + b we emit code like
 509                         //
 510                         // a.Emit ()
 511                         // b.Emit ()
 512                         // Opcodes.Add
 513                         //
 514                         // For await a + await b we have to interfere the flow to keep the
 515                         // stack clean because await yields from the expression. The emit
 516                         // then changes to
 517                         //
 518                         // a = a.EmitToField () // a is changed to temporary field access
 519                         // b = b.EmitToField ()
 520                         // a.Emit ()
 521                         // b.Emit ()
 522                         // Opcodes.Add
 523                         //
 524                         //
 525                         // The idea is to emit expression and leave the stack empty with
 526                         // result value still available.
 527                         //
 528                         // Expressions should override this default implementation when
 529                         // optimized version can be provided (e.g. FieldExpr)
 530                         //
 531                         //
 532                         // We can optimize for side-effect free expressions, they can be
 533                         // emitted out of order
 534                         //
 535                         if (IsSideEffectFree)
 536                                 return this;
 537
 538                         bool needs_temporary = ContainsEmitWithAwait ();
 539                         if (!needs_temporary)
 540                                 ec.EmitThis ();
 541
 542                         // Emit original code
 543                         var field = EmitToFieldSource (ec);
 544                         if (field == null) {
 545                                 //
 546                                 // Store the result to temporary field when we
 547                                 // cannot load `this' directly
 548                                 //
 549                                 field = ec.GetTemporaryField (type);
 550                                 if (needs_temporary) {
 551                                         //
 552                                         // Create temporary local (we cannot load `this' before Emit)
 553                                         //
 554                                         var temp = ec.GetTemporaryLocal (type);
 555                                         ec.Emit (OpCodes.Stloc, temp);
 556
 557                                         ec.EmitThis ();
 558                                         ec.Emit (OpCodes.Ldloc, temp);
 559                                         field.EmitAssignFromStack (ec);
 560
 561                                         ec.FreeTemporaryLocal (temp, type);
 562                                 } else {
 563                                         field.EmitAssignFromStack (ec);
 564                                 }
 565                         }
 566
 567                         return field;
 568                 }
 569
 570                 protected virtual FieldExpr EmitToFieldSource (EmitContext ec)
 571                 {
 572                         //
 573                         // Default implementation calls Emit method
 574                         //
 575                         Emit (ec);
 576                         return null;
 577                 }
 578
 579                 protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
 580                 {
 581                         if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
 582                                 bool contains_await = false;
 583
 584                                 for (int i = 1; i < expressions.Count; ++i) {
 585                                         if (expressions[i].ContainsEmitWithAwait ()) {
 586                                                 contains_await = true;
 587                                                 break;
 588                                         }
 589                                 }
 590
 591                                 if (contains_await) {
 592                                         for (int i = 0; i < expressions.Count; ++i) {
 593                                                 expressions[i] = expressions[i].EmitToField (ec);
 594                                         }
 595                                 }
 596                         }
 597
 598                         for (int i = 0; i < expressions.Count; ++i) {
 599                                 expressions[i].Emit (ec);
 600                         }
 601                 }
 602
 603                 /// <summary>
 604                 ///   Protected constructor.  Only derivate types should
 605                 ///   be able to be created
 606                 /// </summary>
 607
 608                 protected Expression ()
 609                 {
 610                 }
 611
 612                 /// <summary>
 613                 ///   Returns a fully formed expression after a MemberLookup
 614                 /// </summary>
 615                 ///
 616                 static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
 617                 {
 618                         if (spec is EventSpec)
 619                                 return new EventExpr ((EventSpec) spec, loc);
 620                         if (spec is ConstSpec)
 621                                 return new ConstantExpr ((ConstSpec) spec, loc);
 622                         if (spec is FieldSpec)
 623                                 return new FieldExpr ((FieldSpec) spec, loc);
 624                         if (spec is PropertySpec)
 625                                 return new PropertyExpr ((PropertySpec) spec, loc);
 626                         if (spec is TypeSpec)
 627                                 return new TypeExpression (((TypeSpec) spec), loc);
 628
 629                         return null;
 630                 }
 631
 632                 public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
 633                 {
 634                         var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
 635                         if (ctors == null) {
 636                                 rc.Report.SymbolRelatedToPreviousError (type);
 637                                 if (type.IsStruct) {
 638                                         // Report meaningful error for struct as they always have default ctor in C# context
 639                                         OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
 640                                 } else {
 641                                         rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
 642                                                 type.GetSignatureForError ());
 643                                 }
 644
 645                                 return null;
 646                         }
 647
 648                         var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
 649                         if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
 650                                 r.InstanceQualifier = new ConstructorInstanceQualifier (type);
 651                         }
 652
 653                         return r.ResolveMember<MethodSpec> (rc, ref args);
 654                 }
 655
 656                 [Flags]
 657                 public enum MemberLookupRestrictions
 658                 {
 659                         None = 0,
 660                         InvocableOnly = 1,
 661                         ExactArity = 1 << 2,
 662                         ReadAccess = 1 << 3
 663                 }
 664
 665                 //
 666                 // Lookup type `queried_type' for code in class `container_type' with a qualifier of
 667                 // `qualifier_type' or null to lookup members in the current class.
 668                 //
 669                 public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 670                 {
 671                         var members = MemberCache.FindMembers (queried_type, name, false);
 672                         if (members == null)
 673                                 return null;
 674
 675                         MemberSpec non_method = null;
 676                         MemberSpec ambig_non_method = null;
 677                         do {
 678                                 for (int i = 0; i < members.Count; ++i) {
 679                                         var member = members[i];
 680
 681                                         // HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
 682                                         if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
 683                                                 continue;
 684
 685                                         if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0)
 686                                                 continue;
 687
 688                                         if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
 689                                                 continue;
 690
 691                                         if (!errorMode) {
 692                                                 if (!member.IsAccessible (rc))
 693                                                         continue;
 694
 695                                                 //
 696                                                 // With runtime binder we can have a situation where queried type is inaccessible
 697                                                 // because it came via dynamic object, the check about inconsisted accessibility
 698                                                 // had no effect as the type was unknown during compilation
 699                                                 //
 700                                                 // class A {
 701                                                 //              private class N { }
 702                                                 //
 703                                                 //              public dynamic Foo ()
 704                                                 //              {
 705                                                 //                      return new N ();
 706                                                 //              }
 707                                                 //      }
 708                                                 //
 709                                                 if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
 710                                                         continue;
 711                                         }
 712
 713                                         if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
 714                                                 if (member is MethodSpec)
 715                                                         return new MethodGroupExpr (members, queried_type, loc);
 716
 717                                                 if (!Invocation.IsMemberInvocable (member))
 718                                                         continue;
 719                                         }
 720
 721                                         if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
 722                                                 non_method = member;
 723                                         } else if (!errorMode && !member.IsNotCSharpCompatible) {
 724                                                 ambig_non_method = member;
 725                                         }
 726                                 }
 727
 728                                 if (non_method != null) {
 729                                         if (ambig_non_method != null && rc != null) {
 730                                                 var report = rc.Module.Compiler.Report;
 731                                                 report.SymbolRelatedToPreviousError (non_method);
 732                                                 report.SymbolRelatedToPreviousError (ambig_non_method);
 733                                                 report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
 734                                                         non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
 735                                         }
 736
 737                                         if (non_method is MethodSpec)
 738                                                 return new MethodGroupExpr (members, queried_type, loc);
 739
 740                                         return ExprClassFromMemberInfo (non_method, loc);
 741                                 }
 742
 743                                 if (members[0].DeclaringType.BaseType == null)
 744                                         members = null;
 745                                 else
 746                                         members = MemberCache.FindMembers (members[0].DeclaringType.BaseType, name, false);
 747
 748                         } while (members != null);
 749
 750                         return null;
 751                 }
 752
 753                 protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
 754                 {
 755                         throw new NotImplementedException ();
 756                 }
 757
 758                 public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
 759                 {
 760                         if (t == InternalType.ErrorType)
 761                                 return;
 762
 763                         rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
 764                                 oper, t.GetSignatureForError ());
 765                 }
 766
 767                 protected void Error_PointerInsideExpressionTree (ResolveContext ec)
 768                 {
 769                         ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
 770                 }
 771
 772                 /// <summary>
 773                 ///   Returns an expression that can be used to invoke operator true
 774                 ///   on the expression if it exists.
 775                 /// </summary>
 776                 protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
 777                 {
 778                         return GetOperatorTrueOrFalse (ec, e, true, loc);
 779                 }
 780
 781                 /// <summary>
 782                 ///   Returns an expression that can be used to invoke operator false
 783                 ///   on the expression if it exists.
 784                 /// </summary>
 785                 protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
 786                 {
 787                         return GetOperatorTrueOrFalse (ec, e, false, loc);
 788                 }
 789
 790                 static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
 791                 {
 792                         var op = is_true ? Operator.OpType.True : Operator.OpType.False;
 793                         var methods = MemberCache.GetUserOperator (e.type, op, false);
 794                         if (methods == null)
 795                                 return null;
 796
 797                         Arguments arguments = new Arguments (1);
 798                         arguments.Add (new Argument (e));
 799
 800                         var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
 801                         var oper = res.ResolveOperator (ec, ref arguments);
 802
 803                         if (oper == null)
 804                                 return null;
 805
 806                         return new UserOperatorCall (oper, arguments, null, loc);
 807                 }
 808
 809                 public virtual string ExprClassName
 810                 {
 811                         get {
 812                                 switch (eclass){
 813                                 case ExprClass.Unresolved:
 814                                         return "Unresolved";
 815                                 case ExprClass.Value:
 816                                         return "value";
 817                                 case ExprClass.Variable:
 818                                         return "variable";
 819                                 case ExprClass.Namespace:
 820                                         return "namespace";
 821                                 case ExprClass.Type:
 822                                         return "type";
 823                                 case ExprClass.MethodGroup:
 824                                         return "method group";
 825                                 case ExprClass.PropertyAccess:
 826                                         return "property access";
 827                                 case ExprClass.EventAccess:
 828                                         return "event access";
 829                                 case ExprClass.IndexerAccess:
 830                                         return "indexer access";
 831                                 case ExprClass.Nothing:
 832                                         return "null";
 833                                 case ExprClass.TypeParameter:
 834                                         return "type parameter";
 835                                 }
 836                                 throw new Exception ("Should not happen");
 837                         }
 838                 }
 839
 840                 /// <summary>
 841                 ///   Reports that we were expecting `expr' to be of class `expected'
 842                 /// </summary>
 843                 public void Error_UnexpectedKind (IMemberContext ctx, Expression memberExpr, string expected, string was, Location loc)
 844                 {
 845                         var name = memberExpr.GetSignatureForError ();
 846
 847                         ctx.Module.Compiler.Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected", name, was, expected);
 848                 }
 849
 850                 public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
 851                 {
 852                         string [] valid = new string [4];
 853                         int count = 0;
 854
 855                         if ((flags & ResolveFlags.VariableOrValue) != 0) {
 856                                 valid [count++] = "variable";
 857                                 valid [count++] = "value";
 858                         }
 859
 860                         if ((flags & ResolveFlags.Type) != 0)
 861                                 valid [count++] = "type";
 862
 863                         if ((flags & ResolveFlags.MethodGroup) != 0)
 864                                 valid [count++] = "method group";
 865
 866                         if (count == 0)
 867                                 valid [count++] = "unknown";
 868
 869                         StringBuilder sb = new StringBuilder (valid [0]);
 870                         for (int i = 1; i < count - 1; i++) {
 871                                 sb.Append ("', `");
 872                                 sb.Append (valid [i]);
 873                         }
 874                         if (count > 1) {
 875                                 sb.Append ("' or `");
 876                                 sb.Append (valid [count - 1]);
 877                         }
 878
 879                         ec.Report.Error (119, loc,
 880                                 "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
 881                 }
 882
 883                 public static void UnsafeError (ResolveContext ec, Location loc)
 884                 {
 885                         UnsafeError (ec.Report, loc);
 886                 }
 887
 888                 public static void UnsafeError (Report Report, Location loc)
 889                 {
 890                         Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
 891                 }
 892
 893                 //
 894                 // Converts `source' to an int, uint, long or ulong.
 895                 //
 896                 protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source)
 897                 {
 898                         var btypes = ec.BuiltinTypes;
 899
 900                         if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 901                                 Arguments args = new Arguments (1);
 902                                 args.Add (new Argument (source));
 903                                 return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, loc).Resolve (ec);
 904                         }
 905
 906                         Expression converted;
 907
 908                         using (ec.Set (ResolveContext.Options.CheckedScope)) {
 909                                 converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
 910                                 if (converted == null)
 911                                         converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
 912                                 if (converted == null)
 913                                         converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
 914                                 if (converted == null)
 915                                         converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);
 916
 917                                 if (converted == null) {
 918                                         source.Error_ValueCannotBeConverted (ec, btypes.Int, false);
 919                                         return null;
 920                                 }
 921                         }
 922
 923                         //
 924                         // Only positive constants are allowed at compile time
 925                         //
 926                         Constant c = converted as Constant;
 927                         if (c != null && c.IsNegative)
 928                                 Error_NegativeArrayIndex (ec, source.loc);
 929
 930                         // No conversion needed to array index
 931                         if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
 932                                 return converted;
 933
 934                         return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
 935                 }
 936
 937                 //
 938                 // Derived classes implement this method by cloning the fields that
 939                 // could become altered during the Resolve stage
 940                 //
 941                 // Only expressions that are created for the parser need to implement
 942                 // this.
 943                 //
 944                 protected virtual void CloneTo (CloneContext clonectx, Expression target)
 945                 {
 946                         throw new NotImplementedException (
 947                                 String.Format (
 948                                         "CloneTo not implemented for expression {0}", this.GetType ()));
 949                 }
 950
 951                 //
 952                 // Clones an expression created by the parser.
 953                 //
 954                 // We only support expressions created by the parser so far, not
 955                 // expressions that have been resolved (many more classes would need
 956                 // to implement CloneTo).
 957                 //
 958                 // This infrastructure is here merely for Lambda expressions which
 959                 // compile the same code using different type values for the same
 960                 // arguments to find the correct overload
 961                 //
 962                 public virtual Expression Clone (CloneContext clonectx)
 963                 {
 964                         Expression cloned = (Expression) MemberwiseClone ();
 965                         CloneTo (clonectx, cloned);
 966
 967                         return cloned;
 968                 }
 969
 970                 //
 971                 // Implementation of expression to expression tree conversion
 972                 //
 973                 public abstract Expression CreateExpressionTree (ResolveContext ec);
 974
 975                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
 976                 {
 977                         return CreateExpressionFactoryCall (ec, name, null, args, loc);
 978                 }
 979
 980                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
 981                 {
 982                         return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
 983                 }
 984
 985                 public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
 986                 {
 987                         return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
 988                 }
 989
 990                 protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
 991                 {
 992                         var t = ec.Module.PredefinedTypes.Expression.Resolve ();
 993                         if (t == null)
 994                                 return null;
 995
 996                         return new TypeExpression (t, loc);
 997                 }
 998
 999                 //
1000                 // Implemented by all expressions which support conversion from
1001                 // compiler expression to invokable runtime expression. Used by
1002                 // dynamic C# binder.
1003                 //
1004                 public virtual SLE.Expression MakeExpression (BuilderContext ctx)
1005                 {
1006                         throw new NotImplementedException ("MakeExpression for " + GetType ());
1007                 }
1008
1009                 public virtual object Accept (StructuralVisitor visitor)
1010                 {
1011                         return visitor.Visit (this);
1012                 }
1013         }
1014
1015         /// <summary>
1016         ///   This is just a base class for expressions that can
1017         ///   appear on statements (invocations, object creation,
1018         ///   assignments, post/pre increment and decrement).  The idea
1019         ///   being that they would support an extra Emition interface that
1020         ///   does not leave a result on the stack.
1021         /// </summary>
1022         public abstract class ExpressionStatement : Expression {
1023
1024                 public ExpressionStatement ResolveStatement (BlockContext ec)
1025                 {
1026                         Expression e = Resolve (ec);
1027                         if (e == null)
1028                                 return null;
1029
1030                         ExpressionStatement es = e as ExpressionStatement;
1031                         if (es == null)
1032                                 Error_InvalidExpressionStatement (ec);
1033
1034                         if (ec.CurrentAnonymousMethod is AsyncInitializer && !(e is Assign) &&
1035                                 (e.Type.IsGenericTask || e.Type == ec.Module.PredefinedTypes.Task.TypeSpec)) {
1036                                 ec.Report.Warning (4014, 1, e.Location,
1037                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator");
1038                         }
1039
1040                         return es;
1041                 }
1042
1043                 /// <summary>
1044                 ///   Requests the expression to be emitted in a `statement'
1045                 ///   context.  This means that no new value is left on the
1046                 ///   stack after invoking this method (constrasted with
1047                 ///   Emit that will always leave a value on the stack).
1048                 /// </summary>
1049                 public abstract void EmitStatement (EmitContext ec);
1050
1051                 public override void EmitSideEffect (EmitContext ec)
1052                 {
1053                         EmitStatement (ec);
1054                 }
1055         }
1056
1057         /// <summary>
1058         ///   This kind of cast is used to encapsulate the child
1059         ///   whose type is child.Type into an expression that is
1060         ///   reported to return "return_type".  This is used to encapsulate
1061         ///   expressions which have compatible types, but need to be dealt
1062         ///   at higher levels with.
1063         ///
1064         ///   For example, a "byte" expression could be encapsulated in one
1065         ///   of these as an "unsigned int".  The type for the expression
1066         ///   would be "unsigned int".
1067         ///
1068         /// </summary>
1069         public abstract class TypeCast : Expression
1070         {
1071                 protected readonly Expression child;
1072
1073                 protected TypeCast (Expression child, TypeSpec return_type)
1074                 {
1075                         eclass = child.eclass;
1076                         loc = child.Location;
1077                         type = return_type;
1078                         this.child = child;
1079                 }
1080
1081                 public Expression Child {
1082                         get {
1083                                 return child;
1084                         }
1085                 }
1086
1087                 public override bool ContainsEmitWithAwait ()
1088                 {
1089                         return child.ContainsEmitWithAwait ();
1090                 }
1091
1092                 public override Expression CreateExpressionTree (ResolveContext ec)
1093                 {
1094                         Arguments args = new Arguments (2);
1095                         args.Add (new Argument (child.CreateExpressionTree (ec)));
1096                         args.Add (new Argument (new TypeOf (type, loc)));
1097
1098                         if (type.IsPointer || child.Type.IsPointer)
1099                                 Error_PointerInsideExpressionTree (ec);
1100
1101                         return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
1102                 }
1103
1104                 protected override Expression DoResolve (ResolveContext ec)
1105                 {
1106                         // This should never be invoked, we are born in fully
1107                         // initialized state.
1108
1109                         return this;
1110                 }
1111
1112                 public override void Emit (EmitContext ec)
1113                 {
1114                         child.Emit (ec);
1115                 }
1116
1117                 public override SLE.Expression MakeExpression (BuilderContext ctx)
1118                 {
1119 #if STATIC
1120                         return base.MakeExpression (ctx);
1121 #else
1122                         return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
1123                                 SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
1124                                 SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
1125 #endif
1126                 }
1127
1128                 protected override void CloneTo (CloneContext clonectx, Expression t)
1129                 {
1130                         // Nothing to clone
1131                 }
1132
1133                 public override bool IsNull {
1134                         get { return child.IsNull; }
1135                 }
1136         }
1137
1138         public class EmptyCast : TypeCast {
1139                 EmptyCast (Expression child, TypeSpec target_type)
1140                         : base (child, target_type)
1141                 {
1142                 }
1143
1144                 public static Expression Create (Expression child, TypeSpec type)
1145                 {
1146                         Constant c = child as Constant;
1147                         if (c != null)
1148                                 return new EmptyConstantCast (c, type);
1149
1150                         EmptyCast e = child as EmptyCast;
1151                         if (e != null)
1152                                 return new EmptyCast (e.child, type);
1153
1154                         return new EmptyCast (child, type);
1155                 }
1156
1157                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1158                 {
1159                         child.EmitBranchable (ec, label, on_true);
1160                 }
1161
1162                 public override void EmitSideEffect (EmitContext ec)
1163                 {
1164                         child.EmitSideEffect (ec);
1165                 }
1166         }
1167
1168         //
1169         // Used for predefined type user operator (no obsolete check, etc.)
1170         //
1171         public class OperatorCast : TypeCast
1172         {
1173                 readonly MethodSpec conversion_operator;
1174
1175                 public OperatorCast (Expression expr, TypeSpec target_type)
1176                         : this (expr, target_type, target_type, false)
1177                 {
1178                 }
1179
1180                 public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
1181                         : this (expr, target_type, target_type, find_explicit)
1182                 {
1183                 }
1184
1185                 public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
1186                         : base (expr, returnType)
1187                 {
1188                         var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
1189                         var mi = MemberCache.GetUserOperator (declaringType, op, true);
1190
1191                         if (mi != null) {
1192                                 foreach (MethodSpec oper in mi) {
1193                                         if (oper.ReturnType != returnType)
1194                                                 continue;
1195
1196                                         if (oper.Parameters.Types[0] == expr.Type) {
1197                                                 conversion_operator = oper;
1198                                                 return;
1199                                         }
1200                                 }
1201                         }
1202
1203                         throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
1204                                 returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
1205                 }
1206
1207                 public override void Emit (EmitContext ec)
1208                 {
1209                         child.Emit (ec);
1210                         ec.Emit (OpCodes.Call, conversion_operator);
1211                 }
1212         }
1213
1214         //
1215         // Constant specialization of EmptyCast.
1216         // We need to special case this since an empty cast of
1217         // a constant is still a constant.
1218         //
1219         public class EmptyConstantCast : Constant
1220         {
1221                 public readonly Constant child;
1222
1223                 public EmptyConstantCast (Constant child, TypeSpec type)
1224                         : base (child.Location)
1225                 {
1226                         if (child == null)
1227                                 throw new ArgumentNullException ("child");
1228
1229                         this.child = child;
1230                         this.eclass = child.eclass;
1231                         this.type = type;
1232                 }
1233
1234                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1235                 {
1236                         if (child.Type == target_type)
1237                                 return child;
1238
1239                         // FIXME: check that 'type' can be converted to 'target_type' first
1240                         return child.ConvertExplicitly (in_checked_context, target_type);
1241                 }
1242
1243                 public override Expression CreateExpressionTree (ResolveContext ec)
1244                 {
1245                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
1246                                 child.CreateExpressionTree (ec),
1247                                 new TypeOf (type, loc));
1248
1249                         if (type.IsPointer)
1250                                 Error_PointerInsideExpressionTree (ec);
1251
1252                         return CreateExpressionFactoryCall (ec, "Convert", args);
1253                 }
1254
1255                 public override bool IsDefaultValue {
1256                         get { return child.IsDefaultValue; }
1257                 }
1258
1259                 public override bool IsNegative {
1260                         get { return child.IsNegative; }
1261                 }
1262
1263                 public override bool IsNull {
1264                         get { return child.IsNull; }
1265                 }
1266
1267                 public override bool IsOneInteger {
1268                         get { return child.IsOneInteger; }
1269                 }
1270
1271                 public override bool IsSideEffectFree {
1272                         get {
1273                                 return child.IsSideEffectFree;
1274                         }
1275                 }
1276
1277                 public override bool IsZeroInteger {
1278                         get { return child.IsZeroInteger; }
1279                 }
1280
1281                 public override void Emit (EmitContext ec)
1282                 {
1283                         child.Emit (ec);
1284                 }
1285
1286                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1287                 {
1288                         child.EmitBranchable (ec, label, on_true);
1289
1290                         // Only to make verifier happy
1291                         if (TypeManager.IsGenericParameter (type) && child.IsNull)
1292                                 ec.Emit (OpCodes.Unbox_Any, type);
1293                 }
1294
1295                 public override void EmitSideEffect (EmitContext ec)
1296                 {
1297                         child.EmitSideEffect (ec);
1298                 }
1299
1300                 public override object GetValue ()
1301                 {
1302                         return child.GetValue ();
1303                 }
1304
1305                 public override string GetValueAsLiteral ()
1306                 {
1307                         return child.GetValueAsLiteral ();
1308                 }
1309
1310                 public override long GetValueAsLong ()
1311                 {
1312                         return child.GetValueAsLong ();
1313                 }
1314
1315                 public override Constant ConvertImplicitly (TypeSpec target_type)
1316                 {
1317                         if (type == target_type)
1318                                 return this;
1319
1320                         // FIXME: Do we need to check user conversions?
1321                         if (!Convert.ImplicitStandardConversionExists (this, target_type))
1322                                 return null;
1323
1324                         return child.ConvertImplicitly (target_type);
1325                 }
1326         }
1327
1328         /// <summary>
1329         ///  This class is used to wrap literals which belong inside Enums
1330         /// </summary>
1331         public class EnumConstant : Constant
1332         {
1333                 public Constant Child;
1334
1335                 public EnumConstant (Constant child, TypeSpec enum_type)
1336                         : base (child.Location)
1337                 {
1338                         this.Child = child;
1339
1340                         this.eclass = ExprClass.Value;
1341                         this.type = enum_type;
1342                 }
1343
1344                 protected EnumConstant (Location loc)
1345                         : base (loc)
1346                 {
1347                 }
1348
1349                 public override void Emit (EmitContext ec)
1350                 {
1351                         Child.Emit (ec);
1352                 }
1353
1354                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1355                 {
1356                         Child.EncodeAttributeValue (rc, enc, Child.Type);
1357                 }
1358
1359                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1360                 {
1361                         Child.EmitBranchable (ec, label, on_true);
1362                 }
1363
1364                 public override void EmitSideEffect (EmitContext ec)
1365                 {
1366                         Child.EmitSideEffect (ec);
1367                 }
1368
1369                 public override string GetSignatureForError()
1370                 {
1371                         return TypeManager.CSharpName (Type);
1372                 }
1373
1374                 public override object GetValue ()
1375                 {
1376                         return Child.GetValue ();
1377                 }
1378
1379 #if !STATIC
1380                 public override object GetTypedValue ()
1381                 {
1382                         //
1383                         // The method can be used in dynamic context only (on closed types)
1384                         //
1385                         // System.Enum.ToObject cannot be called on dynamic types
1386                         // EnumBuilder has to be used, but we cannot use EnumBuilder
1387                         // because it does not properly support generics
1388                         //
1389                         return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
1390                 }
1391 #endif
1392
1393                 public override string GetValueAsLiteral ()
1394                 {
1395                         return Child.GetValueAsLiteral ();
1396                 }
1397
1398                 public override long GetValueAsLong ()
1399                 {
1400                         return Child.GetValueAsLong ();
1401                 }
1402
1403                 public EnumConstant Increment()
1404                 {
1405                         return new EnumConstant (((IntegralConstant) Child).Increment (), type);
1406                 }
1407
1408                 public override bool IsDefaultValue {
1409                         get {
1410                                 return Child.IsDefaultValue;
1411                         }
1412                 }
1413
1414                 public override bool IsSideEffectFree {
1415                         get {
1416                                 return Child.IsSideEffectFree;
1417                         }
1418                 }
1419
1420                 public override bool IsZeroInteger {
1421                         get { return Child.IsZeroInteger; }
1422                 }
1423
1424                 public override bool IsNegative {
1425                         get {
1426                                 return Child.IsNegative;
1427                         }
1428                 }
1429
1430                 public override Constant ConvertExplicitly(bool in_checked_context, TypeSpec target_type)
1431                 {
1432                         if (Child.Type == target_type)
1433                                 return Child;
1434
1435                         return Child.ConvertExplicitly (in_checked_context, target_type);
1436                 }
1437
1438                 public override Constant ConvertImplicitly (TypeSpec type)
1439                 {
1440                         if (this.type == type) {
1441                                 return this;
1442                         }
1443
1444                         if (!Convert.ImplicitStandardConversionExists (this, type)){
1445                                 return null;
1446                         }
1447
1448                         return Child.ConvertImplicitly (type);
1449                 }
1450         }
1451
1452         /// <summary>
1453         ///   This kind of cast is used to encapsulate Value Types in objects.
1454         ///
1455         ///   The effect of it is to box the value type emitted by the previous
1456         ///   operation.
1457         /// </summary>
1458         public class BoxedCast : TypeCast {
1459
1460                 public BoxedCast (Expression expr, TypeSpec target_type)
1461                         : base (expr, target_type)
1462                 {
1463                         eclass = ExprClass.Value;
1464                 }
1465
1466                 protected override Expression DoResolve (ResolveContext ec)
1467                 {
1468                         // This should never be invoked, we are born in fully
1469                         // initialized state.
1470
1471                         return this;
1472                 }
1473
1474                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1475                 {
1476                         // Only boxing to object type is supported
1477                         if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
1478                                 base.EncodeAttributeValue (rc, enc, targetType);
1479                                 return;
1480                         }
1481
1482                         enc.Encode (child.Type);
1483                         child.EncodeAttributeValue (rc, enc, child.Type);
1484                 }
1485
1486                 public override void Emit (EmitContext ec)
1487                 {
1488                         base.Emit (ec);
1489
1490                         ec.Emit (OpCodes.Box, child.Type);
1491                 }
1492
1493                 public override void EmitSideEffect (EmitContext ec)
1494                 {
1495                         // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
1496                         // so, we need to emit the box+pop instructions in most cases
1497                         if (child.Type.IsStruct &&
1498                             (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
1499                                 child.EmitSideEffect (ec);
1500                         else
1501                                 base.EmitSideEffect (ec);
1502                 }
1503         }
1504
1505         public class UnboxCast : TypeCast {
1506                 public UnboxCast (Expression expr, TypeSpec return_type)
1507                         : base (expr, return_type)
1508                 {
1509                 }
1510
1511                 protected override Expression DoResolve (ResolveContext ec)
1512                 {
1513                         // This should never be invoked, we are born in fully
1514                         // initialized state.
1515
1516                         return this;
1517                 }
1518
1519                 public override void Emit (EmitContext ec)
1520                 {
1521                         base.Emit (ec);
1522
1523                         ec.Emit (OpCodes.Unbox_Any, type);
1524                 }
1525         }
1526
1527         /// <summary>
1528         ///   This is used to perform explicit numeric conversions.
1529         ///
1530         ///   Explicit numeric conversions might trigger exceptions in a checked
1531         ///   context, so they should generate the conv.ovf opcodes instead of
1532         ///   conv opcodes.
1533         /// </summary>
1534         public class ConvCast : TypeCast {
1535                 public enum Mode : byte {
1536                         I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
1537                         U1_I1, U1_CH,
1538                         I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
1539                         U2_I1, U2_U1, U2_I2, U2_CH,
1540                         I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
1541                         U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
1542                         I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
1543                         U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
1544                         CH_I1, CH_U1, CH_I2,
1545                         R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
1546                         R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
1547                         I_I8,
1548                 }
1549
1550                 Mode mode;
1551
1552                 public ConvCast (Expression child, TypeSpec return_type, Mode m)
1553                         : base (child, return_type)
1554                 {
1555                         mode = m;
1556                 }
1557
1558                 protected override Expression DoResolve (ResolveContext ec)
1559                 {
1560                         // This should never be invoked, we are born in fully
1561                         // initialized state.
1562
1563                         return this;
1564                 }
1565
1566                 public override string ToString ()
1567                 {
1568                         return String.Format ("ConvCast ({0}, {1})", mode, child);
1569                 }
1570
1571                 public override void Emit (EmitContext ec)
1572                 {
1573                         base.Emit (ec);
1574
1575                         if (ec.HasSet (EmitContext.Options.CheckedScope)) {
1576                                 switch (mode){
1577                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1578                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1579                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1580                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1581                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1582
1583                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1584                                 case Mode.U1_CH: /* nothing */ break;
1585
1586                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1587                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1588                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1589                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1590                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1591                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1592
1593                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1594                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1595                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1596                                 case Mode.U2_CH: /* nothing */ break;
1597
1598                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1599                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1600                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1601                                 case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1602                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1603                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1604                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1605
1606                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1607                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1608                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1609                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1610                                 case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1611                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1612
1613                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1614                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1615                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1616                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1617                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1618                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1619                                 case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1620                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1621                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;
1622
1623                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1624                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1625                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1626                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1627                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1628                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
1629                                 case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1630                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1631                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;
1632
1633                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1634                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1635                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1636
1637                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1638                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1639                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1640                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1641                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1642                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1643                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1644                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1645                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1646
1647                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1648                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1649                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1650                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1651                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1652                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1653                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1654                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1655                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1656                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1657
1658                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1659                                 }
1660                         } else {
1661                                 switch (mode){
1662                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
1663                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
1664                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
1665                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
1666                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;
1667
1668                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
1669                                 case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;
1670
1671                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
1672                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
1673                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
1674                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
1675                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
1676                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;
1677
1678                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
1679                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
1680                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
1681                                 case Mode.U2_CH: /* nothing */ break;
1682
1683                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
1684                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
1685                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
1686                                 case Mode.I4_U4: /* nothing */ break;
1687                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_U2); break;
1688                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_I8); break;
1689                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_U2); break;
1690
1691                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_I1); break;
1692                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_U1); break;
1693                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_I2); break;
1694                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_U2); break;
1695                                 case Mode.U4_I4: /* nothing */ break;
1696                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_U2); break;
1697
1698                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_I1); break;
1699                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_U1); break;
1700                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_I2); break;
1701                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_U2); break;
1702                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_I4); break;
1703                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_U4); break;
1704                                 case Mode.I8_U8: /* nothing */ break;
1705                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_U2); break;
1706                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_U); break;
1707
1708                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_I1); break;
1709                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_U1); break;
1710                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_I2); break;
1711                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_U2); break;
1712                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_I4); break;
1713                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_U4); break;
1714                                 case Mode.U8_I8: /* nothing */ break;
1715                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_U2); break;
1716                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_U); break;
1717
1718                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_I1); break;
1719                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_U1); break;
1720                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_I2); break;
1721
1722                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_I1); break;
1723                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_U1); break;
1724                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_I2); break;
1725                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_U2); break;
1726                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_I4); break;
1727                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_U4); break;
1728                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_I8); break;
1729                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_U8); break;
1730                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_U2); break;
1731
1732                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_I1); break;
1733                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_U1); break;
1734                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_I2); break;
1735                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_U2); break;
1736                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_I4); break;
1737                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_U4); break;
1738                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_I8); break;
1739                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_U8); break;
1740                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_U2); break;
1741                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1742
1743                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_U8); break;
1744                                 }
1745                         }
1746                 }
1747         }
1748
1749         class OpcodeCast : TypeCast
1750         {
1751                 readonly OpCode op;
1752
1753                 public OpcodeCast (Expression child, TypeSpec return_type, OpCode op)
1754                         : base (child, return_type)
1755                 {
1756                         this.op = op;
1757                 }
1758
1759                 protected override Expression DoResolve (ResolveContext ec)
1760                 {
1761                         // This should never be invoked, we are born in fully
1762                         // initialized state.
1763
1764                         return this;
1765                 }
1766
1767                 public override void Emit (EmitContext ec)
1768                 {
1769                         base.Emit (ec);
1770                         ec.Emit (op);
1771                 }
1772
1773                 public TypeSpec UnderlyingType {
1774                         get { return child.Type; }
1775                 }
1776         }
1777
1778         //
1779         // Opcode casts expression with 2 opcodes but only
1780         // single expression tree node
1781         //
1782         class OpcodeCastDuplex : OpcodeCast
1783         {
1784                 readonly OpCode second;
1785
1786                 public OpcodeCastDuplex (Expression child, TypeSpec returnType, OpCode first, OpCode second)
1787                         : base (child, returnType, first)
1788                 {
1789                         this.second = second;
1790                 }
1791
1792                 public override void Emit (EmitContext ec)
1793                 {
1794                         base.Emit (ec);
1795                         ec.Emit (second);
1796                 }
1797         }
1798
1799         /// <summary>
1800         ///   This kind of cast is used to encapsulate a child and cast it
1801         ///   to the class requested
1802         /// </summary>
1803         public sealed class ClassCast : TypeCast {
1804                 readonly bool forced;
1805
1806                 public ClassCast (Expression child, TypeSpec return_type)
1807                         : base (child, return_type)
1808                 {
1809                 }
1810
1811                 public ClassCast (Expression child, TypeSpec return_type, bool forced)
1812                         : base (child, return_type)
1813                 {
1814                         this.forced = forced;
1815                 }
1816
1817                 public override void Emit (EmitContext ec)
1818                 {
1819                         base.Emit (ec);
1820
1821                         bool gen = TypeManager.IsGenericParameter (child.Type);
1822                         if (gen)
1823                                 ec.Emit (OpCodes.Box, child.Type);
1824
1825                         if (type.IsGenericParameter) {
1826                                 ec.Emit (OpCodes.Unbox_Any, type);
1827                                 return;
1828                         }
1829
1830                         if (gen && !forced)
1831                                 return;
1832
1833                         ec.Emit (OpCodes.Castclass, type);
1834                 }
1835         }
1836
1837         //
1838         // Created during resolving pahse when an expression is wrapped or constantified
1839         // and original expression can be used later (e.g. for expression trees)
1840         //
1841         public class ReducedExpression : Expression
1842         {
1843                 sealed class ReducedConstantExpression : EmptyConstantCast
1844                 {
1845                         readonly Expression orig_expr;
1846
1847                         public ReducedConstantExpression (Constant expr, Expression orig_expr)
1848                                 : base (expr, expr.Type)
1849                         {
1850                                 this.orig_expr = orig_expr;
1851                         }
1852
1853                         public override Constant ConvertImplicitly (TypeSpec target_type)
1854                         {
1855                                 Constant c = base.ConvertImplicitly (target_type);
1856                                 if (c != null)
1857                                         c = new ReducedConstantExpression (c, orig_expr);
1858
1859                                 return c;
1860                         }
1861
1862                         public override Expression CreateExpressionTree (ResolveContext ec)
1863                         {
1864                                 return orig_expr.CreateExpressionTree (ec);
1865                         }
1866
1867                         public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1868                         {
1869                                 Constant c = base.ConvertExplicitly (in_checked_context, target_type);
1870                                 if (c != null)
1871                                         c = new ReducedConstantExpression (c, orig_expr);
1872                                 return c;
1873                         }
1874
1875                         public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1876                         {
1877                                 //
1878                                 // LAMESPEC: Reduced conditional expression is allowed as an attribute argument
1879                                 //
1880                                 if (orig_expr is Conditional)
1881                                         child.EncodeAttributeValue (rc, enc, targetType);
1882                                 else
1883                                         base.EncodeAttributeValue (rc, enc, targetType);
1884                         }
1885                 }
1886
1887                 sealed class ReducedExpressionStatement : ExpressionStatement
1888                 {
1889                         readonly Expression orig_expr;
1890                         readonly ExpressionStatement stm;
1891
1892                         public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
1893                         {
1894                                 this.orig_expr = orig;
1895                                 this.stm = stm;
1896                                 this.eclass = stm.eclass;
1897                                 this.type = stm.Type;
1898
1899                                 this.loc = orig.Location;
1900                         }
1901
1902                         public override bool ContainsEmitWithAwait ()
1903                         {
1904                                 return stm.ContainsEmitWithAwait ();
1905                         }
1906
1907                         public override Expression CreateExpressionTree (ResolveContext ec)
1908                         {
1909                                 return orig_expr.CreateExpressionTree (ec);
1910                         }
1911
1912                         protected override Expression DoResolve (ResolveContext ec)
1913                         {
1914                                 return this;
1915                         }
1916
1917                         public override void Emit (EmitContext ec)
1918                         {
1919                                 stm.Emit (ec);
1920                         }
1921
1922                         public override void EmitStatement (EmitContext ec)
1923                         {
1924                                 stm.EmitStatement (ec);
1925                         }
1926                 }
1927
1928                 readonly Expression expr, orig_expr;
1929
1930                 private ReducedExpression (Expression expr, Expression orig_expr)
1931                 {
1932                         this.expr = expr;
1933                         this.eclass = expr.eclass;
1934                         this.type = expr.Type;
1935                         this.orig_expr = orig_expr;
1936                         this.loc = orig_expr.Location;
1937                 }
1938
1939                 #region Properties
1940
1941                 public override bool IsSideEffectFree {
1942                         get {
1943                                 return expr.IsSideEffectFree;
1944                         }
1945                 }
1946
1947                 public Expression OriginalExpression {
1948                         get {
1949                                 return orig_expr;
1950                         }
1951                 }
1952
1953                 #endregion
1954
1955                 public override bool ContainsEmitWithAwait ()
1956                 {
1957                         return expr.ContainsEmitWithAwait ();
1958                 }
1959
1960                 //
1961                 // Creates fully resolved expression switcher
1962                 //
1963                 public static Constant Create (Constant expr, Expression original_expr)
1964                 {
1965                         if (expr.eclass == ExprClass.Unresolved)
1966                                 throw new ArgumentException ("Unresolved expression");
1967
1968                         return new ReducedConstantExpression (expr, original_expr);
1969                 }
1970
1971                 public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
1972                 {
1973                         return new ReducedExpressionStatement (s, orig);
1974                 }
1975
1976                 public static Expression Create (Expression expr, Expression original_expr)
1977                 {
1978                         return Create (expr, original_expr, true);
1979                 }
1980
1981                 //
1982                 // Creates unresolved reduce expression. The original expression has to be
1983                 // already resolved. Created expression is constant based based on `expr'
1984                 // value unless canBeConstant is used
1985                 //
1986                 public static Expression Create (Expression expr, Expression original_expr, bool canBeConstant)
1987                 {
1988                         if (canBeConstant) {
1989                                 Constant c = expr as Constant;
1990                                 if (c != null)
1991                                         return Create (c, original_expr);
1992                         }
1993
1994                         ExpressionStatement s = expr as ExpressionStatement;
1995                         if (s != null)
1996                                 return Create (s, original_expr);
1997
1998                         if (expr.eclass == ExprClass.Unresolved)
1999                                 throw new ArgumentException ("Unresolved expression");
2000
2001                         return new ReducedExpression (expr, original_expr);
2002                 }
2003
2004                 public override Expression CreateExpressionTree (ResolveContext ec)
2005                 {
2006                         return orig_expr.CreateExpressionTree (ec);
2007                 }
2008
2009                 protected override Expression DoResolve (ResolveContext ec)
2010                 {
2011                         return this;
2012                 }
2013
2014                 public override void Emit (EmitContext ec)
2015                 {
2016                         expr.Emit (ec);
2017                 }
2018
2019                 public override Expression EmitToField (EmitContext ec)
2020                 {
2021                         return expr.EmitToField(ec);
2022                 }
2023
2024                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2025                 {
2026                         expr.EmitBranchable (ec, target, on_true);
2027                 }
2028
2029                 public override SLE.Expression MakeExpression (BuilderContext ctx)
2030                 {
2031                         return orig_expr.MakeExpression (ctx);
2032                 }
2033         }
2034
2035         //
2036         // Standard composite pattern
2037         //
2038         public abstract class CompositeExpression : Expression
2039         {
2040                 protected Expression expr;
2041
2042                 protected CompositeExpression (Expression expr)
2043                 {
2044                         this.expr = expr;
2045                         this.loc = expr.Location;
2046                 }
2047
2048                 public override bool ContainsEmitWithAwait ()
2049                 {
2050                         return expr.ContainsEmitWithAwait ();
2051                 }
2052
2053                 public override Expression CreateExpressionTree (ResolveContext rc)
2054                 {
2055                         return expr.CreateExpressionTree (rc);
2056                 }
2057
2058                 public Expression Child {
2059                         get { return expr; }
2060                 }
2061
2062                 protected override Expression DoResolve (ResolveContext rc)
2063                 {
2064                         expr = expr.Resolve (rc);
2065                         if (expr != null) {
2066                                 type = expr.Type;
2067                                 eclass = expr.eclass;
2068                         }
2069
2070                         return this;
2071                 }
2072
2073                 public override void Emit (EmitContext ec)
2074                 {
2075                         expr.Emit (ec);
2076                 }
2077
2078                 public override bool IsNull {
2079                         get { return expr.IsNull; }
2080                 }
2081         }
2082
2083         //
2084         // Base of expressions used only to narrow resolve flow
2085         //
2086         public abstract class ShimExpression : Expression
2087         {
2088                 protected Expression expr;
2089
2090                 protected ShimExpression (Expression expr)
2091                 {
2092                         this.expr = expr;
2093                 }
2094
2095                 public Expression Expr {
2096                         get {
2097                                 return expr;
2098                         }
2099                 }
2100
2101                 protected override void CloneTo (CloneContext clonectx, Expression t)
2102                 {
2103                         if (expr == null)
2104                                 return;
2105
2106                         ShimExpression target = (ShimExpression) t;
2107                         target.expr = expr.Clone (clonectx);
2108                 }
2109
2110                 public override bool ContainsEmitWithAwait ()
2111                 {
2112                         return expr.ContainsEmitWithAwait ();
2113                 }
2114
2115                 public override Expression CreateExpressionTree (ResolveContext ec)
2116                 {
2117                         throw new NotSupportedException ("ET");
2118                 }
2119
2120                 public override void Emit (EmitContext ec)
2121                 {
2122                         throw new InternalErrorException ("Missing Resolve call");
2123                 }
2124
2125         }
2126
2127         //
2128         // Unresolved type name expressions
2129         //
2130         public abstract class ATypeNameExpression : FullNamedExpression
2131         {
2132                 string name;
2133                 protected TypeArguments targs;
2134
2135                 protected ATypeNameExpression (string name, Location l)
2136                 {
2137                         this.name = name;
2138                         loc = l;
2139                 }
2140
2141                 protected ATypeNameExpression (string name, TypeArguments targs, Location l)
2142                 {
2143                         this.name = name;
2144                         this.targs = targs;
2145                         loc = l;
2146                 }
2147
2148                 protected ATypeNameExpression (string name, int arity, Location l)
2149                         : this (name, new UnboundTypeArguments (arity), l)
2150                 {
2151                 }
2152
2153                 #region Properties
2154
2155                 protected int Arity {
2156                         get {
2157                                 return targs == null ? 0 : targs.Count;
2158                         }
2159                 }
2160
2161                 public bool HasTypeArguments {
2162                         get {
2163                                 return targs != null && !targs.IsEmpty;
2164                         }
2165                 }
2166
2167                 public string Name {
2168                         get {
2169                                 return name;
2170                         }
2171                         set {
2172                                 name = value;
2173                         }
2174                 }
2175
2176                 public TypeArguments TypeArguments {
2177                         get {
2178                                 return targs;
2179                         }
2180                 }
2181
2182                 #endregion
2183
2184                 public override bool Equals (object obj)
2185                 {
2186                         ATypeNameExpression atne = obj as ATypeNameExpression;
2187                         return atne != null && atne.Name == Name &&
2188                                 (targs == null || targs.Equals (atne.targs));
2189                 }
2190
2191                 public override int GetHashCode ()
2192                 {
2193                         return Name.GetHashCode ();
2194                 }
2195
2196                 // TODO: Move it to MemberCore
2197                 public static string GetMemberType (MemberCore mc)
2198                 {
2199                         if (mc is Property)
2200                                 return "property";
2201                         if (mc is Indexer)
2202                                 return "indexer";
2203                         if (mc is FieldBase)
2204                                 return "field";
2205                         if (mc is MethodCore)
2206                                 return "method";
2207                         if (mc is EnumMember)
2208                                 return "enum";
2209                         if (mc is Event)
2210                                 return "event";
2211
2212                         return "type";
2213                 }
2214
2215                 public override string GetSignatureForError ()
2216                 {
2217                         if (targs != null) {
2218                                 return Name + "<" + targs.GetSignatureForError () + ">";
2219                         }
2220
2221                         return Name;
2222                 }
2223
2224                 public abstract Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restriction);
2225         }
2226
2227         /// <summary>
2228         ///   SimpleName expressions are formed of a single word and only happen at the beginning
2229         ///   of a dotted-name.
2230         /// </summary>
2231         public class SimpleName : ATypeNameExpression
2232         {
2233                 public SimpleName (string name, Location l)
2234                         : base (name, l)
2235                 {
2236                 }
2237
2238                 public SimpleName (string name, TypeArguments args, Location l)
2239                         : base (name, args, l)
2240                 {
2241                 }
2242
2243                 public SimpleName (string name, int arity, Location l)
2244                         : base (name, arity, l)
2245                 {
2246                 }
2247
2248                 public SimpleName GetMethodGroup ()
2249                 {
2250                         return new SimpleName (Name, targs, loc);
2251                 }
2252
2253                 protected override Expression DoResolve (ResolveContext rc)
2254                 {
2255                         var e = SimpleNameResolve (rc, null, false);
2256
2257                         var fe = e as FieldExpr;
2258                         if (fe != null) {
2259                                 fe.VerifyAssignedStructField (rc, null);
2260                         }
2261
2262                         return e;
2263                 }
2264
2265                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
2266                 {
2267                         return SimpleNameResolve (ec, right_side, false);
2268                 }
2269
2270                 protected virtual void Error_TypeOrNamespaceNotFound (IMemberContext ctx)
2271                 {
2272                         if (ctx.CurrentType != null) {
2273                                 var member = MemberLookup (ctx, false, ctx.CurrentType, Name, 0, MemberLookupRestrictions.ExactArity, loc) as MemberExpr;
2274                                 if (member != null) {
2275                                         member.Error_UnexpectedKind (ctx, member, "type", member.KindName, loc);
2276                                         return;
2277                                 }
2278                         }
2279
2280                         var retval = ctx.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2281                         if (retval != null) {
2282                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (retval.Type);
2283                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
2284                                 return;
2285                         }
2286
2287                         retval = ctx.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2288                         if (retval != null) {
2289                                 Error_TypeArgumentsCannotBeUsed (ctx, retval.Type, Arity, loc);
2290                                 return;
2291                         }
2292
2293                         NamespaceContainer.Error_NamespaceNotFound (loc, Name, ctx.Module.Compiler.Report);
2294                 }
2295
2296                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext ec)
2297                 {
2298                         FullNamedExpression fne = ec.LookupNamespaceOrType (Name, Arity, LookupMode.Normal, loc);
2299
2300                         if (fne != null) {
2301                                 if (fne.Type != null && Arity > 0) {
2302                                         if (HasTypeArguments) {
2303                                                 GenericTypeExpr ct = new GenericTypeExpr (fne.Type, targs, loc);
2304                                                 if (ct.ResolveAsType (ec) == null)
2305                                                         return null;
2306
2307                                                 return ct;
2308                                         }
2309
2310                                         return new GenericOpenTypeExpr (fne.Type, loc);
2311                                 }
2312
2313                                 //
2314                                 // dynamic namespace is ignored when dynamic is allowed (does not apply to types)
2315                                 //
2316                                 if (!(fne is Namespace))
2317                                         return fne;
2318                         }
2319
2320                         if (Arity == 0 && Name == "dynamic" && ec.Module.Compiler.Settings.Version > LanguageVersion.V_3) {
2321                                 if (!ec.Module.PredefinedAttributes.Dynamic.IsDefined) {
2322                                         ec.Module.Compiler.Report.Error (1980, Location,
2323                                                 "Dynamic keyword requires `{0}' to be defined. Are you missing System.Core.dll assembly reference?",
2324                                                 ec.Module.PredefinedAttributes.Dynamic.GetSignatureForError ());
2325                                 }
2326
2327                                 fne = new DynamicTypeExpr (loc);
2328                                 fne.ResolveAsType (ec);
2329                         }
2330
2331                         if (fne != null)
2332                                 return fne;
2333
2334                         Error_TypeOrNamespaceNotFound (ec);
2335                         return null;
2336                 }
2337
2338                 public bool IsPossibleTypeOrNamespace (IMemberContext mc)
2339                 {
2340                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
2341                 }
2342
2343                 public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
2344                 {
2345                         int lookup_arity = Arity;
2346                         bool errorMode = false;
2347                         Expression e;
2348                         Block current_block = rc.CurrentBlock;
2349                         INamedBlockVariable variable = null;
2350                         bool variable_found = false;
2351
2352                         while (true) {
2353                                 //
2354                                 // Stage 1: binding to local variables or parameters
2355                                 //
2356                                 // LAMESPEC: It should take invocableOnly into account but that would break csc compatibility
2357                                 //
2358                                 if (current_block != null && lookup_arity == 0) {
2359                                         if (current_block.ParametersBlock.TopBlock.GetLocalName (Name, current_block.Original, ref variable)) {
2360                                                 if (!variable.IsDeclared) {
2361                                                         // We found local name in accessible block but it's not
2362                                                         // initialized yet, maybe the user wanted to bind to something else
2363                                                         errorMode = true;
2364                                                         variable_found = true;
2365                                                 } else {
2366                                                         e = variable.CreateReferenceExpression (rc, loc);
2367                                                         if (e != null) {
2368                                                                 if (Arity > 0)
2369                                                                         Error_TypeArgumentsCannotBeUsed (rc, "variable", Name, loc);
2370
2371                                                                 return e;
2372                                                         }
2373                                                 }
2374                                         }
2375                                 }
2376
2377                                 //
2378                                 // Stage 2: Lookup members if we are inside a type up to top level type for nested types
2379                                 //
2380                                 TypeSpec member_type = rc.CurrentType;
2381                                 for (; member_type != null; member_type = member_type.DeclaringType) {
2382                                         e = MemberLookup (rc, errorMode, member_type, Name, lookup_arity, restrictions, loc);
2383                                         if (e == null)
2384                                                 continue;
2385
2386                                         var me = e as MemberExpr;
2387                                         if (me == null) {
2388                                                 // The name matches a type, defer to ResolveAsTypeStep
2389                                                 if (e is TypeExpr)
2390                                                         break;
2391
2392                                                 continue;
2393                                         }
2394
2395                                         if (errorMode) {
2396                                                 if (variable != null) {
2397                                                         if (me is FieldExpr || me is ConstantExpr || me is EventExpr || me is PropertyExpr) {
2398                                                                 rc.Report.Error (844, loc,
2399                                                                         "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the member `{1}'",
2400                                                                         Name, me.GetSignatureForError ());
2401                                                         } else {
2402                                                                 break;
2403                                                         }
2404                                                 } else if (me is MethodGroupExpr || me is PropertyExpr || me is IndexerExpr) {
2405                                                         // Leave it to overload resolution to report correct error
2406                                                 } else {
2407                                                         // TODO: rc.Report.SymbolRelatedToPreviousError ()
2408                                                         ErrorIsInaccesible (rc, me.GetSignatureForError (), loc);
2409                                                 }
2410                                         } else {
2411                                                 // LAMESPEC: again, ignores InvocableOnly
2412                                                 if (variable != null) {
2413                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2414                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2415                                                 }
2416
2417                                                 //
2418                                                 // MemberLookup does not check accessors availability, this is actually needed for properties only
2419                                                 //
2420                                                 var pe = me as PropertyExpr;
2421                                                 if (pe != null) {
2422
2423                                                         // Break as there is no other overload available anyway
2424                                                         if ((restrictions & MemberLookupRestrictions.ReadAccess) != 0) {
2425                                                                 if (!pe.PropertyInfo.HasGet || !pe.PropertyInfo.Get.IsAccessible (rc))
2426                                                                         break;
2427
2428                                                                 pe.Getter = pe.PropertyInfo.Get;
2429                                                         } else {
2430                                                                 if (!pe.PropertyInfo.HasSet || !pe.PropertyInfo.Set.IsAccessible (rc))
2431                                                                         break;
2432
2433                                                                 pe.Setter = pe.PropertyInfo.Set;
2434                                                         }
2435                                                 }
2436                                         }
2437
2438                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2439                                         // TODO: Should go to MemberAccess
2440                                         me = me.ResolveMemberAccess (rc, null, null);
2441
2442                                         if (Arity > 0) {
2443                                                 targs.Resolve (rc);
2444                                                 me.SetTypeArguments (rc, targs);
2445                                         }
2446
2447                                         return me;
2448                                 }
2449
2450                                 //
2451                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2452                                 //
2453                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2454                                         if (IsPossibleTypeOrNamespace (rc)) {
2455                                                 if (variable != null) {
2456                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2457                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2458                                                 }
2459
2460                                                 return ResolveAsTypeOrNamespace (rc);
2461                                         }
2462                                 }
2463
2464                                 if (errorMode) {
2465                                         if (variable_found) {
2466                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2467                                         } else {
2468                                                 if (Arity > 0) {
2469                                                         var tparams = rc.CurrentTypeParameters;
2470                                                         if (tparams != null) {
2471                                                                 if (tparams.Find (Name) != null) {
2472                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2473                                                                         return null;
2474                                                                 }
2475                                                         }
2476
2477                                                         var ct = rc.CurrentType;
2478                                                         do {
2479                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2480                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2481                                                                                 if (ctp.Name == Name) {
2482                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2483                                                                                         return null;
2484                                                                                 }
2485                                                                         }
2486                                                                 }
2487
2488                                                                 ct = ct.DeclaringType;
2489                                                         } while (ct != null);
2490                                                 }
2491
2492                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2493                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2494                                                         if (e != null) {
2495                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2496                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2497                                                                 return e;
2498                                                         }
2499                                                 } else {
2500                                                         var me = MemberLookup (rc, false, rc.CurrentType, Name, Arity, restrictions & ~MemberLookupRestrictions.InvocableOnly, loc) as MemberExpr;
2501                                                         if (me != null) {
2502                                                                 me.Error_UnexpectedKind (rc, me, "method group", me.KindName, loc);
2503                                                                 return ErrorExpression.Instance;
2504                                                         }
2505                                                 }
2506
2507                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2508                                                 if (e != null) {
2509                                                         if (e.Type.Arity != Arity) {
2510                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, Arity, loc);
2511                                                                 return e;
2512                                                         }
2513
2514                                                         if (e is TypeExpr) {
2515                                                                 e.Error_UnexpectedKind (rc, e, "variable", e.ExprClassName, loc);
2516                                                                 return e;
2517                                                         }
2518                                                 }
2519
2520                                                 rc.Report.Error (103, loc, "The name `{0}' does not exist in the current context", Name);
2521                                         }
2522
2523                                         return ErrorExpression.Instance;
2524                                 }
2525
2526                                 if (rc.Module.Evaluator != null) {
2527                                         var fi = rc.Module.Evaluator.LookupField (Name);
2528                                         if (fi != null)
2529                                                 return new FieldExpr (fi.Item1, loc);
2530                                 }
2531
2532                                 lookup_arity = 0;
2533                                 errorMode = true;
2534                         }
2535                 }
2536
2537                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side, bool intermediate)
2538                 {
2539                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2540
2541                         if (e == null)
2542                                 return null;
2543
2544                         if (right_side != null) {
2545                                 if (e is FullNamedExpression && e.eclass != ExprClass.Unresolved) {
2546                                         e.Error_UnexpectedKind (ec, e, "variable", e.ExprClassName, loc);
2547                                     return null;
2548                                 }
2549
2550                                 e = e.ResolveLValue (ec, right_side);
2551                         } else {
2552                                 e = e.Resolve (ec);
2553                         }
2554
2555                         return e;
2556                 }
2557
2558                 public override object Accept (StructuralVisitor visitor)
2559                 {
2560                         return visitor.Visit (this);
2561                 }
2562         }
2563
2564         /// <summary>
2565         ///   Represents a namespace or a type.  The name of the class was inspired by
2566         ///   section 10.8.1 (Fully Qualified Names).
2567         /// </summary>
2568         public abstract class FullNamedExpression : Expression
2569         {
2570                 protected override void CloneTo (CloneContext clonectx, Expression target)
2571                 {
2572                         // Do nothing, most unresolved type expressions cannot be
2573                         // resolved to different type
2574                 }
2575
2576                 public override bool ContainsEmitWithAwait ()
2577                 {
2578                         return false;
2579                 }
2580
2581                 public override Expression CreateExpressionTree (ResolveContext ec)
2582                 {
2583                         throw new NotSupportedException ("ET");
2584                 }
2585
2586                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc);
2587
2588                 //
2589                 // This is used to resolve the expression as a type, a null
2590                 // value will be returned if the expression is not a type
2591                 // reference
2592                 //
2593                 public override TypeSpec ResolveAsType (IMemberContext mc)
2594                 {
2595                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc);
2596
2597                         if (fne == null)
2598                                 return null;
2599
2600                         TypeExpr te = fne as TypeExpr;
2601                         if (te == null) {
2602                                 fne.Error_UnexpectedKind (mc, fne, "type", fne.ExprClassName, loc);
2603                                 return null;
2604                         }
2605
2606                         te.loc = loc;
2607
2608                         type = te.Type;
2609
2610                         var dep = type.GetMissingDependencies ();
2611                         if (dep != null) {
2612                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
2613                         }
2614
2615                         if (type.Kind == MemberKind.Void) {
2616                                 mc.Module.Compiler.Report.Error (673, loc, "System.Void cannot be used from C#. Consider using `void'");
2617                         }
2618
2619                         //
2620                         // Obsolete checks cannot be done when resolving base context as they
2621                         // require type dependencies to be set but we are in process of resolving them
2622                         //
2623                         if (!(mc is TypeDefinition.BaseContext) && !(mc is UsingAliasNamespace.AliasContext)) {
2624                                 ObsoleteAttribute obsolete_attr = type.GetAttributeObsolete ();
2625                                 if (obsolete_attr != null && !mc.IsObsolete) {
2626                                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location, mc.Module.Compiler.Report);
2627                                 }
2628                         }
2629
2630                         return type;
2631                 }
2632
2633
2634                 public override void Emit (EmitContext ec)
2635                 {
2636                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
2637                                 GetSignatureForError ());
2638                 }
2639         }
2640
2641         /// <summary>
2642         ///   Expression that evaluates to a type
2643         /// </summary>
2644         public abstract class TypeExpr : FullNamedExpression
2645         {
2646                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2647                 {
2648                         ResolveAsType (mc);
2649                         return this;
2650                 }
2651
2652                 protected sealed override Expression DoResolve (ResolveContext ec)
2653                 {
2654                         ResolveAsType (ec);
2655                         return this;
2656                 }
2657
2658                 public override bool Equals (object obj)
2659                 {
2660                         TypeExpr tobj = obj as TypeExpr;
2661                         if (tobj == null)
2662                                 return false;
2663
2664                         return Type == tobj.Type;
2665                 }
2666
2667                 public override int GetHashCode ()
2668                 {
2669                         return Type.GetHashCode ();
2670                 }
2671         }
2672
2673         /// <summary>
2674         ///   Fully resolved Expression that already evaluated to a type
2675         /// </summary>
2676         public class TypeExpression : TypeExpr
2677         {
2678                 public TypeExpression (TypeSpec t, Location l)
2679                 {
2680                         Type = t;
2681                         eclass = ExprClass.Type;
2682                         loc = l;
2683                 }
2684
2685                 public sealed override TypeSpec ResolveAsType (IMemberContext ec)
2686                 {
2687                         return type;
2688                 }
2689         }
2690
2691         /// <summary>
2692         ///   This class denotes an expression which evaluates to a member
2693         ///   of a struct or a class.
2694         /// </summary>
2695         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
2696         {
2697                 //
2698                 // An instance expression associated with this member, if it's a
2699                 // non-static member
2700                 //
2701                 public Expression InstanceExpression;
2702
2703                 /// <summary>
2704                 ///   The name of this member.
2705                 /// </summary>
2706                 public abstract string Name {
2707                         get;
2708                 }
2709
2710                 //
2711                 // When base.member is used
2712                 //
2713                 public bool IsBase {
2714                         get { return InstanceExpression is BaseThis; }
2715                 }
2716
2717                 /// <summary>
2718                 ///   Whether this is an instance member.
2719                 /// </summary>
2720                 public abstract bool IsInstance {
2721                         get;
2722                 }
2723
2724                 /// <summary>
2725                 ///   Whether this is a static member.
2726                 /// </summary>
2727                 public abstract bool IsStatic {
2728                         get;
2729                 }
2730
2731                 public abstract string KindName {
2732                         get;
2733                 }
2734
2735                 protected abstract TypeSpec DeclaringType {
2736                         get;
2737                 }
2738
2739                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
2740                         get {
2741                                 return InstanceExpression.Type;
2742                         }
2743                 }
2744
2745                 //
2746                 // Converts best base candidate for virtual method starting from QueriedBaseType
2747                 //
2748                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
2749                 {
2750                         //
2751                         // Only when base.member is used and method is virtual
2752                         //
2753                         if (!IsBase)
2754                                 return method;
2755
2756                         //
2757                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
2758                         // means for base.member access we have to find the closest match after we found best candidate
2759                         //
2760                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
2761                                 //
2762                                 // The method could already be what we are looking for
2763                                 //
2764                                 TypeSpec[] targs = null;
2765                                 if (method.DeclaringType != InstanceExpression.Type) {
2766                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, new MemberFilter (method), BindingRestriction.InstanceOnly) as MethodSpec;
2767                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
2768                                                 if (base_override.IsGeneric)
2769                                                         targs = method.TypeArguments;
2770
2771                                                 method = base_override;
2772                                         }
2773                                 }
2774
2775                                 //
2776                                 // When base access is used inside anonymous method/iterator/etc we need to
2777                                 // get back to the context of original type. We do it by emiting proxy
2778                                 // method in original class and rewriting base call to this compiler
2779                                 // generated method call which does the actual base invocation. This may
2780                                 // introduce redundant storey but with `this' only but it's tricky to avoid
2781                                 // at this stage as we don't know what expressions follow base
2782                                 //
2783                                 if (rc.CurrentAnonymousMethod != null) {
2784                                         if (targs == null && method.IsGeneric) {
2785                                                 targs = method.TypeArguments;
2786                                                 method = method.GetGenericMethodDefinition ();
2787                                         }
2788
2789                                         if (method.Parameters.HasArglist)
2790                                                 throw new NotImplementedException ("__arglist base call proxy");
2791
2792                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
2793
2794                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
2795                                         // get/set member expressions second call would fail to proxy because left expression
2796                                         // would be of 'this' and not 'base' because we share InstanceExpression for get/set
2797                                         // FIXME: The async check is another hack but will probably fail with mutators
2798                                         if (rc.CurrentType.IsStruct || rc.CurrentAnonymousMethod.Storey is AsyncTaskStorey)
2799                                                 InstanceExpression = new This (loc).Resolve (rc);
2800                                 }
2801
2802                                 if (targs != null)
2803                                         method = method.MakeGenericMethod (rc, targs);
2804                         }
2805
2806                         //
2807                         // Only base will allow this invocation to happen.
2808                         //
2809                         if (method.IsAbstract) {
2810                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
2811                         }
2812
2813                         return method;
2814                 }
2815
2816                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
2817                 {
2818                         if (InstanceExpression == null)
2819                                 return;
2820
2821                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
2822                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
2823                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
2824                                 }
2825                         }
2826                 }
2827
2828                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
2829                 {
2830                         if (InstanceExpression == null)
2831                                 return true;
2832
2833                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
2834                 }
2835
2836                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
2837                 {
2838                         var ct = rc.CurrentType;
2839                         if (ct == qualifier)
2840                                 return true;
2841
2842                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
2843                                 return true;
2844
2845                         qualifier = qualifier.GetDefinition ();
2846                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
2847                                 return false;
2848                         }
2849
2850                         return true;
2851                 }
2852
2853                 public override bool ContainsEmitWithAwait ()
2854                 {
2855                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
2856                 }
2857
2858                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
2859                 {
2860                         do {
2861                                 type = type.GetDefinition ();
2862
2863                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
2864                                         return true;
2865
2866                                 type = type.DeclaringType;
2867                         } while (type != null);
2868
2869                         return false;
2870                 }
2871
2872                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
2873                 {
2874                         if (InstanceExpression != null) {
2875                                 InstanceExpression = InstanceExpression.Resolve (rc);
2876                                 CheckProtectedMemberAccess (rc, member);
2877                         }
2878
2879                         if (member.MemberType.IsPointer && !rc.IsUnsafe) {
2880                                 UnsafeError (rc, loc);
2881                         }
2882
2883                         var dep = member.GetMissingDependencies ();
2884                         if (dep != null) {
2885                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
2886                         }
2887
2888                         if (!rc.IsObsolete) {
2889                                 ObsoleteAttribute oa = member.GetAttributeObsolete ();
2890                                 if (oa != null)
2891                                         AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
2892                         }
2893
2894                         if (!(member is FieldSpec))
2895                                 member.MemberDefinition.SetIsUsed ();
2896                 }
2897
2898                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
2899                 {
2900                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
2901                 }
2902
2903                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
2904                 {
2905                         rc.Report.SymbolRelatedToPreviousError (member);
2906                         rc.Report.Error (1540, loc,
2907                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
2908                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
2909                 }
2910
2911                 //
2912                 // Implements identicial simple name and type-name
2913                 //
2914                 public Expression ProbeIdenticalTypeName (ResolveContext rc, Expression left, SimpleName name)
2915                 {
2916                         var t = left.Type;
2917                         if (t.Kind == MemberKind.InternalCompilerType || t is ElementTypeSpec || t.Arity > 0)
2918                                 return left;
2919
2920                         // 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
2921                         // a constant, field, property, local variable, or parameter with the same type as the meaning of E as a type-name
2922
2923                         if (left is MemberExpr || left is VariableReference) {
2924                                 var identical_type = rc.LookupNamespaceOrType (name.Name, 0, LookupMode.Probing, loc) as TypeExpr;
2925                                 if (identical_type != null && identical_type.Type == left.Type)
2926                                         return identical_type;
2927                         }
2928
2929                         return left;
2930                 }
2931
2932                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
2933                 {
2934                         if (IsStatic) {
2935                                 if (InstanceExpression != null) {
2936                                         if (InstanceExpression is TypeExpr) {
2937                                                 var t = InstanceExpression.Type;
2938                                                 do {
2939                                                         ObsoleteAttribute oa = t.GetAttributeObsolete ();
2940                                                         if (oa != null && !rc.IsObsolete) {
2941                                                                 AttributeTester.Report_ObsoleteMessage (oa, t.GetSignatureForError (), loc, rc.Report);
2942                                                         }
2943
2944                                                         t = t.DeclaringType;
2945                                                 } while (t != null);
2946                                         } else {
2947                                                 var runtime_expr = InstanceExpression as RuntimeValueExpression;
2948                                                 if (runtime_expr == null || !runtime_expr.IsSuggestionOnly) {
2949                                                         rc.Report.Error (176, loc,
2950                                                                 "Static member `{0}' cannot be accessed with an instance reference, qualify it with a type name instead",
2951                                                                 GetSignatureForError ());
2952                                                 }
2953                                         }
2954
2955                                         InstanceExpression = null;
2956                                 }
2957
2958                                 return false;
2959                         }
2960
2961                         if (InstanceExpression == null || InstanceExpression is TypeExpr) {
2962                                 if (InstanceExpression != null || !This.IsThisAvailable (rc, true)) {
2963                                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope))
2964                                                 rc.Report.Error (236, loc,
2965                                                         "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
2966                                                         GetSignatureForError ());
2967                                         else
2968                                                 rc.Report.Error (120, loc,
2969                                                         "An object reference is required to access non-static member `{0}'",
2970                                                         GetSignatureForError ());
2971
2972                                         InstanceExpression = new CompilerGeneratedThis (type, loc).Resolve (rc);
2973                                         return false;
2974                                 }
2975
2976                                 if (!TypeManager.IsFamilyAccessible (rc.CurrentType, DeclaringType)) {
2977                                         rc.Report.Error (38, loc,
2978                                                 "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
2979                                                 DeclaringType.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
2980                                 }
2981
2982                                 InstanceExpression = new This (loc);
2983                                 if (this is FieldExpr && rc.CurrentBlock.ParametersBlock.TopBlock.ThisVariable != null) {
2984                                         using (rc.Set (ResolveContext.Options.OmitStructFlowAnalysis)) {
2985                                                 InstanceExpression = InstanceExpression.Resolve (rc);
2986                                         }
2987                                 } else {
2988                                         InstanceExpression = InstanceExpression.Resolve (rc);
2989                                 }
2990
2991                                 return false;
2992                         }
2993
2994                         var me = InstanceExpression as MemberExpr;
2995                         if (me != null) {
2996                                 me.ResolveInstanceExpression (rc, rhs);
2997
2998                                 // Using this check to detect probing instance expression resolve
2999                                 if (!rc.OmitStructFlowAnalysis) {
3000                                         var fe = me as FieldExpr;
3001                                         if (fe != null && fe.IsMarshalByRefAccess (rc)) {
3002                                                 rc.Report.SymbolRelatedToPreviousError (me.DeclaringType);
3003                                                 rc.Report.Warning (1690, 1, loc,
3004                                                         "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
3005                                                         me.GetSignatureForError ());
3006                                         }
3007                                 }
3008
3009                                 return true;
3010                         }
3011
3012                         //
3013                         // Run member-access postponed check once we know that
3014                         // the expression is not field expression which is the only
3015                         // expression which can use uninitialized this
3016                         //
3017                         if (InstanceExpression is This && !(this is FieldExpr) && rc.CurrentBlock.ParametersBlock.TopBlock.ThisVariable != null) {
3018                                 ((This)InstanceExpression).CheckStructThisDefiniteAssignment (rc);
3019                         }
3020
3021                         //
3022                         // Additional checks for l-value member access
3023                         //
3024                         if (rhs != null) {
3025                                 if (InstanceExpression is UnboxCast) {
3026                                         rc.Report.Error (445, InstanceExpression.Location, "Cannot modify the result of an unboxing conversion");
3027                                 }
3028                         }
3029
3030                         return true;
3031                 }
3032
3033                 public virtual MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3034                 {
3035                         if (left != null && left.IsNull && TypeSpec.IsReferenceType (left.Type)) {
3036                                 ec.Report.Warning (1720, 1, left.Location,
3037                                         "Expression will always cause a `{0}'", "System.NullReferenceException");
3038                         }
3039
3040                         InstanceExpression = left;
3041                         return this;
3042                 }
3043
3044                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
3045                 {
3046                         TypeSpec instance_type = InstanceExpression.Type;
3047                         if (TypeSpec.IsValueType (instance_type)) {
3048                                 if (InstanceExpression is IMemoryLocation) {
3049                                         ((IMemoryLocation) InstanceExpression).AddressOf (ec, AddressOp.Load);
3050                                 } else {
3051                                         // Cannot release the temporary variable when its address
3052                                         // is required to be on stack for any parent
3053                                         LocalTemporary t = new LocalTemporary (instance_type);
3054                                         InstanceExpression.Emit (ec);
3055                                         t.Store (ec);
3056                                         t.AddressOf (ec, AddressOp.Store);
3057                                 }
3058                         } else {
3059                                 InstanceExpression.Emit (ec);
3060
3061                                 // Only to make verifier happy
3062                                 if (instance_type.IsGenericParameter && !(InstanceExpression is This) && TypeSpec.IsReferenceType (instance_type))
3063                                         ec.Emit (OpCodes.Box, instance_type);
3064                         }
3065
3066                         if (prepare_for_load)
3067                                 ec.Emit (OpCodes.Dup);
3068                 }
3069
3070                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3071         }
3072
3073         public class ExtensionMethodCandidates
3074         {
3075                 readonly NamespaceContainer container;
3076                 readonly IList<MethodSpec> methods;
3077                 readonly int index;
3078                 readonly IMemberContext context;
3079
3080                 public ExtensionMethodCandidates (IMemberContext context, IList<MethodSpec> methods, NamespaceContainer nsContainer, int lookupIndex)
3081                 {
3082                         this.context = context;
3083                         this.methods = methods;
3084                         this.container = nsContainer;
3085                         this.index = lookupIndex;
3086                 }
3087
3088                 public NamespaceContainer Container {
3089                         get {
3090                                 return container;
3091                         }
3092                 }
3093
3094                 public IMemberContext Context {
3095                         get {
3096                                 return context;
3097                         }
3098                 }
3099
3100                 public int LookupIndex {
3101                         get {
3102                                 return index;
3103                         }
3104                 }
3105
3106                 public IList<MethodSpec> Methods {
3107                         get {
3108                                 return methods;
3109                         }
3110                 }
3111         }
3112
3113         //
3114         // Represents a group of extension method candidates for whole namespace
3115         //
3116         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3117         {
3118                 ExtensionMethodCandidates candidates;
3119                 public readonly Expression ExtensionExpression;
3120
3121                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3122                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3123                 {
3124                         this.candidates = candidates;
3125                         this.ExtensionExpression = extensionExpr;
3126                 }
3127
3128                 public override bool IsStatic {
3129                         get { return true; }
3130                 }
3131
3132                 //
3133                 // For extension methodgroup we are not looking for base members but parent
3134                 // namespace extension methods
3135                 //
3136                 public override IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3137                 {
3138                         // TODO: candidates are null only when doing error reporting, that's
3139                         // incorrect. We have to discover same extension methods in error mode
3140                         if (candidates == null)
3141                                 return null;
3142
3143                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3144
3145                         candidates = candidates.Container.LookupExtensionMethod (candidates.Context, ExtensionExpression.Type, Name, arity, candidates.LookupIndex);
3146                         if (candidates == null)
3147                                 return null;
3148
3149                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3150                 }
3151
3152                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3153                 {
3154                         // We are already here
3155                         return null;
3156                 }
3157
3158                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3159                 {
3160                         if (arguments == null)
3161                                 arguments = new Arguments (1);
3162
3163                         arguments.Insert (0, new Argument (ExtensionExpression, Argument.AType.ExtensionType));
3164                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3165
3166                         // Store resolved argument and restore original arguments
3167                         if (res == null) {
3168                                 // Clean-up modified arguments for error reporting
3169                                 arguments.RemoveAt (0);
3170                                 return null;
3171                         }
3172
3173                         var me = ExtensionExpression as MemberExpr;
3174                         if (me != null)
3175                                 me.ResolveInstanceExpression (ec, null);
3176
3177                         InstanceExpression = null;
3178                         return this;
3179                 }
3180
3181                 #region IErrorHandler Members
3182
3183                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3184                 {
3185                         return false;
3186                 }
3187
3188                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3189                 {
3190                         rc.Report.SymbolRelatedToPreviousError (best);
3191                         rc.Report.Error (1928, loc,
3192                                 "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3193                                 queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3194
3195                         if (index == 0) {
3196                                 rc.Report.Error (1929, loc,
3197                                         "Extension method instance type `{0}' cannot be converted to `{1}'",
3198                                         arg.Type.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3199                         }
3200
3201                         return true;
3202                 }
3203
3204                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3205                 {
3206                         return false;
3207                 }
3208
3209                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3210                 {
3211                         return false;
3212                 }
3213
3214                 #endregion
3215         }
3216
3217         /// <summary>
3218         ///   MethodGroupExpr represents a group of method candidates which
3219         ///   can be resolved to the best method overload
3220         /// </summary>
3221         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3222         {
3223                 protected IList<MemberSpec> Methods;
3224                 MethodSpec best_candidate;
3225                 TypeSpec best_candidate_return;
3226                 protected TypeArguments type_arguments;
3227
3228                 SimpleName simple_name;
3229                 protected TypeSpec queried_type;
3230
3231                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3232                 {
3233                         Methods = mi;
3234                         this.loc = loc;
3235                         this.type = InternalType.MethodGroup;
3236
3237                         eclass = ExprClass.MethodGroup;
3238                         queried_type = type;
3239                 }
3240
3241                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3242                         : this (new MemberSpec[] { m }, type, loc)
3243                 {
3244                 }
3245
3246                 #region Properties
3247
3248                 public MethodSpec BestCandidate {
3249                         get {
3250                                 return best_candidate;
3251                         }
3252                 }
3253
3254                 public TypeSpec BestCandidateReturnType {
3255                         get {
3256                                 return best_candidate_return;
3257                         }
3258                 }
3259
3260                 public IList<MemberSpec> Candidates {
3261                         get {
3262                                 return Methods;
3263                         }
3264                 }
3265
3266                 protected override TypeSpec DeclaringType {
3267                         get {
3268                                 return queried_type;
3269                         }
3270                 }
3271
3272                 public override bool IsInstance {
3273                         get {
3274                                 if (best_candidate != null)
3275                                         return !best_candidate.IsStatic;
3276
3277                                 return false;
3278                         }
3279                 }
3280
3281                 public override bool IsStatic {
3282                         get {
3283                                 if (best_candidate != null)
3284                                         return best_candidate.IsStatic;
3285
3286                                 return false;
3287                         }
3288                 }
3289
3290                 public override string KindName {
3291                         get { return "method"; }
3292                 }
3293
3294                 public override string Name {
3295                         get {
3296                                 if (best_candidate != null)
3297                                         return best_candidate.Name;
3298
3299                                 // TODO: throw ?
3300                                 return Methods.First ().Name;
3301                         }
3302                 }
3303
3304                 #endregion
3305
3306                 //
3307                 // When best candidate is already know this factory can be used
3308                 // to avoid expensive overload resolution to be called
3309                 //
3310                 // NOTE: InstanceExpression has to be set manually
3311                 //
3312                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3313                 {
3314                         return new MethodGroupExpr (best, queriedType, loc) {
3315                                 best_candidate = best,
3316                                 best_candidate_return = best.ReturnType
3317                         };
3318                 }
3319
3320                 public override string GetSignatureForError ()
3321                 {
3322                         if (best_candidate != null)
3323                                 return best_candidate.GetSignatureForError ();
3324
3325                         return Methods.First ().GetSignatureForError ();
3326                 }
3327
3328                 public override Expression CreateExpressionTree (ResolveContext ec)
3329                 {
3330                         if (best_candidate == null) {
3331                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3332                                 return null;
3333                         }
3334
3335                         if (best_candidate.IsConditionallyExcluded (ec, loc))
3336                                 ec.Report.Error (765, loc,
3337                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3338
3339                         return new TypeOfMethod (best_candidate, loc);
3340                 }
3341
3342                 protected override Expression DoResolve (ResolveContext ec)
3343                 {
3344                         this.eclass = ExprClass.MethodGroup;
3345
3346                         if (InstanceExpression != null) {
3347                                 InstanceExpression = InstanceExpression.Resolve (ec);
3348                                 if (InstanceExpression == null)
3349                                         return null;
3350                         }
3351
3352                         return this;
3353                 }
3354
3355                 public override void Emit (EmitContext ec)
3356                 {
3357                         throw new NotSupportedException ();
3358                 }
3359
3360                 public void EmitCall (EmitContext ec, Arguments arguments)
3361                 {
3362                         var call = new CallEmitter ();
3363                         call.InstanceExpression = InstanceExpression;
3364                         call.Emit (ec, best_candidate, arguments, loc);
3365                 }
3366
3367                 public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
3368                 {
3369                         ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
3370                                 Name, TypeManager.CSharpName (target));
3371                 }
3372
3373                 public static bool IsExtensionMethodArgument (Expression expr)
3374                 {
3375                         //
3376                         // LAMESPEC: No details about which expressions are not allowed
3377                         //
3378                         return !(expr is TypeExpr) && !(expr is BaseThis);
3379                 }
3380
3381                 /// <summary>
3382                 ///   Find the Applicable Function Members (7.4.2.1)
3383                 ///
3384                 ///   me: Method Group expression with the members to select.
3385                 ///       it might contain constructors or methods (or anything
3386                 ///       that maps to a method).
3387                 ///
3388                 ///   Arguments: ArrayList containing resolved Argument objects.
3389                 ///
3390                 ///   loc: The location if we want an error to be reported, or a Null
3391                 ///        location for "probing" purposes.
3392                 ///
3393                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
3394                 ///            that is the best match of me on Arguments.
3395                 ///
3396                 /// </summary>
3397                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
3398                 {
3399                         // TODO: causes issues with probing mode, remove explicit Kind check
3400                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
3401                                 return this;
3402
3403                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
3404                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
3405                                 r.BaseMembersProvider = this;
3406                                 r.InstanceQualifier = this;
3407                         }
3408
3409                         if (cerrors != null)
3410                                 r.CustomErrors = cerrors;
3411
3412                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
3413                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
3414                         if (best_candidate == null)
3415                                 return r.BestCandidateIsDynamic ? this : null;
3416
3417                         // Overload resolver had to create a new method group, all checks bellow have already been executed
3418                         if (r.BestCandidateNewMethodGroup != null)
3419                                 return r.BestCandidateNewMethodGroup;
3420
3421                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
3422                                 if (InstanceExpression != null) {
3423                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
3424                                                 InstanceExpression = null;
3425                                         } else {
3426                                                 if (best_candidate.IsStatic && simple_name != null) {
3427                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
3428                                                 }
3429
3430                                                 InstanceExpression.Resolve (ec);
3431                                         }
3432                                 }
3433
3434                                 ResolveInstanceExpression (ec, null);
3435                         }
3436
3437                         var base_override = CandidateToBaseOverride (ec, best_candidate);
3438                         if (base_override == best_candidate) {
3439                                 best_candidate_return = r.BestCandidateReturnType;
3440                         } else {
3441                                 best_candidate = base_override;
3442                                 best_candidate_return = best_candidate.ReturnType;
3443                         }
3444
3445                         return this;
3446                 }
3447
3448                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3449                 {
3450                         simple_name = original;
3451                         return base.ResolveMemberAccess (ec, left, original);
3452                 }
3453
3454                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
3455                 {
3456                         type_arguments = ta;
3457                 }
3458
3459                 #region IBaseMembersProvider Members
3460
3461                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3462                 {
3463                         return baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
3464                 }
3465
3466                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3467                 {
3468                         if (queried_type == member.DeclaringType)
3469                                 return null;
3470
3471                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
3472                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
3473                 }
3474
3475                 //
3476                 // Extension methods lookup after ordinary methods candidates failed to apply
3477                 //
3478                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3479                 {
3480                         if (InstanceExpression == null)
3481                                 return null;
3482
3483                         InstanceExpression = InstanceExpression.Resolve (rc);
3484                         if (!IsExtensionMethodArgument (InstanceExpression))
3485                                 return null;
3486
3487                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3488                         var methods = rc.LookupExtensionMethod (InstanceExpression.Type, Methods[0].Name, arity);
3489                         if (methods == null)
3490                                 return null;
3491
3492                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
3493                         emg.SetTypeArguments (rc, type_arguments);
3494                         return emg;
3495                 }
3496
3497                 #endregion
3498         }
3499
3500         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
3501         {
3502                 public ConstructorInstanceQualifier (TypeSpec type)
3503                         : this ()
3504                 {
3505                         InstanceType = type;
3506                 }
3507
3508                 public TypeSpec InstanceType { get; private set; }
3509
3510                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3511                 {
3512                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
3513                 }
3514         }
3515
3516         public struct OverloadResolver
3517         {
3518                 [Flags]
3519                 public enum Restrictions
3520                 {
3521                         None = 0,
3522                         DelegateInvoke = 1,
3523                         ProbingOnly     = 1 << 1,
3524                         CovariantDelegate = 1 << 2,
3525                         NoBaseMembers = 1 << 3,
3526                         BaseMembersIncluded = 1 << 4
3527                 }
3528
3529                 public interface IBaseMembersProvider
3530                 {
3531                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
3532                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
3533                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
3534                 }
3535
3536                 public interface IErrorHandler
3537                 {
3538                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
3539                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
3540                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
3541                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
3542                 }
3543
3544                 public interface IInstanceQualifier
3545                 {
3546                         TypeSpec InstanceType { get; }
3547                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
3548                 }
3549
3550                 sealed class NoBaseMembers : IBaseMembersProvider
3551                 {
3552                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
3553
3554                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3555                         {
3556                                 return null;
3557                         }
3558
3559                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3560                         {
3561                                 return null;
3562                         }
3563
3564                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3565                         {
3566                                 return null;
3567                         }
3568                 }
3569
3570                 struct AmbiguousCandidate
3571                 {
3572                         public readonly MemberSpec Member;
3573                         public readonly bool Expanded;
3574                         public readonly AParametersCollection Parameters;
3575
3576                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
3577                         {
3578                                 Member = member;
3579                                 Parameters = parameters;
3580                                 Expanded = expanded;
3581                         }
3582                 }
3583
3584                 Location loc;
3585                 IList<MemberSpec> members;
3586                 TypeArguments type_arguments;
3587                 IBaseMembersProvider base_provider;
3588                 IErrorHandler custom_errors;
3589                 IInstanceQualifier instance_qualifier;
3590                 Restrictions restrictions;
3591                 MethodGroupExpr best_candidate_extension_group;
3592                 TypeSpec best_candidate_return_type;
3593
3594                 SessionReportPrinter lambda_conv_msgs;
3595
3596                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
3597                         : this (members, null, restrictions, loc)
3598                 {
3599                 }
3600
3601                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
3602                         : this ()
3603                 {
3604                         if (members == null || members.Count == 0)
3605                                 throw new ArgumentException ("empty members set");
3606
3607                         this.members = members;
3608                         this.loc = loc;
3609                         type_arguments = targs;
3610                         this.restrictions = restrictions;
3611                         if (IsDelegateInvoke)
3612                                 this.restrictions |= Restrictions.NoBaseMembers;
3613
3614                         base_provider = NoBaseMembers.Instance;
3615                 }
3616
3617                 #region Properties
3618
3619                 public IBaseMembersProvider BaseMembersProvider {
3620                         get {
3621                                 return base_provider;
3622                         }
3623                         set {
3624                                 base_provider = value;
3625                         }
3626                 }
3627
3628                 public bool BestCandidateIsDynamic { get; set; }
3629
3630                 //
3631                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
3632                 //
3633                 public MethodGroupExpr BestCandidateNewMethodGroup {
3634                         get {
3635                                 return best_candidate_extension_group;
3636                         }
3637                 }
3638
3639                 //
3640                 // Return type can be different between best candidate and closest override
3641                 //
3642                 public TypeSpec BestCandidateReturnType {
3643                         get {
3644                                 return best_candidate_return_type;
3645                         }
3646                 }
3647
3648                 public IErrorHandler CustomErrors {
3649                         get {
3650                                 return custom_errors;
3651                         }
3652                         set {
3653                                 custom_errors = value;
3654                         }
3655                 }
3656
3657                 TypeSpec DelegateType {
3658                         get {
3659                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
3660                                         throw new InternalErrorException ("Not running in delegate mode", loc);
3661
3662                                 return members [0].DeclaringType;
3663                         }
3664                 }
3665
3666                 public IInstanceQualifier InstanceQualifier {
3667                         get {
3668                                 return instance_qualifier;
3669                         }
3670                         set {
3671                                 instance_qualifier = value;
3672                         }
3673                 }
3674
3675                 bool IsProbingOnly {
3676                         get {
3677                                 return (restrictions & Restrictions.ProbingOnly) != 0;
3678                         }
3679                 }
3680
3681                 bool IsDelegateInvoke {
3682                         get {
3683                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
3684                         }
3685                 }
3686
3687                 #endregion
3688
3689                 //
3690                 //  7.4.3.3  Better conversion from expression
3691                 //  Returns :   1    if a->p is better,
3692                 //              2    if a->q is better,
3693                 //              0 if neither is better
3694                 //
3695                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
3696                 {
3697                         TypeSpec argument_type = a.Type;
3698
3699                         //
3700                         // If argument is an anonymous function
3701                         //
3702                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
3703                                 //
3704                                 // p and q are delegate types or expression tree types
3705                                 //
3706                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
3707                                         if (q.MemberDefinition != p.MemberDefinition) {
3708                                                 return 0;
3709                                         }
3710
3711                                         //
3712                                         // Uwrap delegate from Expression<T>
3713                                         //
3714                                         q = TypeManager.GetTypeArguments (q)[0];
3715                                         p = TypeManager.GetTypeArguments (p)[0];
3716                                 }
3717
3718                                 var p_m = Delegate.GetInvokeMethod (p);
3719                                 var q_m = Delegate.GetInvokeMethod (q);
3720
3721                                 //
3722                                 // With identical parameter lists
3723                                 //
3724                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
3725                                         return 0;
3726
3727                                 p = p_m.ReturnType;
3728                                 q = q_m.ReturnType;
3729
3730                                 //
3731                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
3732                                 //
3733                                 if (p.Kind == MemberKind.Void) {
3734                                         return q.Kind != MemberKind.Void ? 2 : 0;
3735                                 }
3736
3737                                 //
3738                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
3739                                 //
3740                                 if (q.Kind == MemberKind.Void) {
3741                                         return p.Kind != MemberKind.Void ? 1: 0;
3742                                 }
3743
3744                                 //
3745                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
3746                                 // better conversion is performed between underlying types Y1 and Y2
3747                                 //
3748                                 if (p.IsGenericTask || q.IsGenericTask) {
3749                                         var async_am = a.Expr as AnonymousMethodExpression;
3750                                         if (async_am != null && async_am.Block.IsAsync) {
3751
3752                                                 if (p.IsGenericTask != q.IsGenericTask) {
3753                                                         return 0;
3754                                                 }
3755
3756                                                 q = q.TypeArguments[0];
3757                                                 p = p.TypeArguments[0];
3758                                         }
3759                                 }
3760
3761                                 //
3762                                 // The parameters are identicial and return type is not void, use better type conversion
3763                                 // on return type to determine better one
3764                                 //
3765                         } else {
3766                                 if (argument_type == p)
3767                                         return 1;
3768
3769                                 if (argument_type == q)
3770                                         return 2;
3771                         }
3772
3773                         return BetterTypeConversion (ec, p, q);
3774                 }
3775
3776                 //
3777                 // 7.4.3.4  Better conversion from type
3778                 //
3779                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
3780                 {
3781                         if (p == null || q == null)
3782                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
3783
3784                         switch (p.BuiltinType) {
3785                         case BuiltinTypeSpec.Type.Int:
3786                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
3787                                         return 1;
3788                                 break;
3789                         case BuiltinTypeSpec.Type.Long:
3790                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
3791                                         return 1;
3792                                 break;
3793                         case BuiltinTypeSpec.Type.SByte:
3794                                 switch (q.BuiltinType) {
3795                                 case BuiltinTypeSpec.Type.Byte:
3796                                 case BuiltinTypeSpec.Type.UShort:
3797                                 case BuiltinTypeSpec.Type.UInt:
3798                                 case BuiltinTypeSpec.Type.ULong:
3799                                         return 1;
3800                                 }
3801                                 break;
3802                         case BuiltinTypeSpec.Type.Short:
3803                                 switch (q.BuiltinType) {
3804                                 case BuiltinTypeSpec.Type.UShort:
3805                                 case BuiltinTypeSpec.Type.UInt:
3806                                 case BuiltinTypeSpec.Type.ULong:
3807                                         return 1;
3808                                 }
3809                                 break;
3810                         case BuiltinTypeSpec.Type.Dynamic:
3811                                 // Dynamic is never better
3812                                 return 2;
3813                         }
3814
3815                         switch (q.BuiltinType) {
3816                         case BuiltinTypeSpec.Type.Int:
3817                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
3818                                         return 2;
3819                                 break;
3820                         case BuiltinTypeSpec.Type.Long:
3821                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
3822                                         return 2;
3823                                 break;
3824                         case BuiltinTypeSpec.Type.SByte:
3825                                 switch (p.BuiltinType) {
3826                                 case BuiltinTypeSpec.Type.Byte:
3827                                 case BuiltinTypeSpec.Type.UShort:
3828                                 case BuiltinTypeSpec.Type.UInt:
3829                                 case BuiltinTypeSpec.Type.ULong:
3830                                         return 2;
3831                                 }
3832                                 break;
3833                         case BuiltinTypeSpec.Type.Short:
3834                                 switch (p.BuiltinType) {
3835                                 case BuiltinTypeSpec.Type.UShort:
3836                                 case BuiltinTypeSpec.Type.UInt:
3837                                 case BuiltinTypeSpec.Type.ULong:
3838                                         return 2;
3839                                 }
3840                                 break;
3841                         case BuiltinTypeSpec.Type.Dynamic:
3842                                 // Dynamic is never better
3843                                 return 1;
3844                         }
3845
3846                         // FIXME: handle lifted operators
3847
3848                         // TODO: this is expensive
3849                         Expression p_tmp = new EmptyExpression (p);
3850                         Expression q_tmp = new EmptyExpression (q);
3851
3852                         bool p_to_q = Convert.ImplicitConversionExists (ec, p_tmp, q);
3853                         bool q_to_p = Convert.ImplicitConversionExists (ec, q_tmp, p);
3854
3855                         if (p_to_q && !q_to_p)
3856                                 return 1;
3857
3858                         if (q_to_p && !p_to_q)
3859                                 return 2;
3860
3861                         return 0;
3862                 }
3863
3864                 /// <summary>
3865                 ///   Determines "Better function" between candidate
3866                 ///   and the current best match
3867                 /// </summary>
3868                 /// <remarks>
3869                 ///    Returns a boolean indicating :
3870                 ///     false if candidate ain't better
3871                 ///     true  if candidate is better than the current best match
3872                 /// </remarks>
3873                 static bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
3874                         MemberSpec best, AParametersCollection bparam, bool best_params)
3875                 {
3876                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
3877                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
3878
3879                         bool better_at_least_one = false;
3880                         bool same = true;
3881                         int args_count = args == null ? 0 : args.Count;
3882                         int j = 0;
3883                         Argument a = null;
3884                         TypeSpec ct, bt;
3885                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
3886                                 a = args[j];
3887
3888                                 // Default arguments are ignored for better decision
3889                                 if (a.IsDefaultArgument)
3890                                         break;
3891
3892                                 //
3893                                 // When comparing named argument the parameter type index has to be looked up
3894                                 // in original parameter set (override version for virtual members)
3895                                 //
3896                                 NamedArgument na = a as NamedArgument;
3897                                 if (na != null) {
3898                                         int idx = cparam.GetParameterIndexByName (na.Name);
3899                                         ct = candidate_pd.Types[idx];
3900                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
3901                                                 ct = TypeManager.GetElementType (ct);
3902
3903                                         idx = bparam.GetParameterIndexByName (na.Name);
3904                                         bt = best_pd.Types[idx];
3905                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
3906                                                 bt = TypeManager.GetElementType (bt);
3907                                 } else {
3908                                         ct = candidate_pd.Types[c_idx];
3909                                         bt = best_pd.Types[b_idx];
3910
3911                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
3912                                                 ct = TypeManager.GetElementType (ct);
3913                                                 --c_idx;
3914                                         }
3915
3916                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
3917                                                 bt = TypeManager.GetElementType (bt);
3918                                                 --b_idx;
3919                                         }
3920                                 }
3921
3922                                 if (TypeSpecComparer.IsEqual (ct, bt))
3923                                         continue;
3924
3925                                 same = false;
3926                                 int result = BetterExpressionConversion (ec, a, ct, bt);
3927
3928                                 // for each argument, the conversion to 'ct' should be no worse than
3929                                 // the conversion to 'bt'.
3930                                 if (result == 2)
3931                                         return false;
3932
3933                                 // for at least one argument, the conversion to 'ct' should be better than
3934                                 // the conversion to 'bt'.
3935                                 if (result != 0)
3936                                         better_at_least_one = true;
3937                         }
3938
3939                         if (better_at_least_one)
3940                                 return true;
3941
3942                         //
3943                         // This handles the case
3944                         //
3945                         //   Add (float f1, float f2, float f3);
3946                         //   Add (params decimal [] foo);
3947                         //
3948                         // The call Add (3, 4, 5) should be ambiguous.  Without this check, the
3949                         // first candidate would've chosen as better.
3950                         //
3951                         if (!same && !a.IsDefaultArgument)
3952                                 return false;
3953
3954                         //
3955                         // The two methods have equal non-optional parameter types, apply tie-breaking rules
3956                         //
3957
3958                         //
3959                         // This handles the following cases:
3960                         //
3961                         //  Foo (int i) is better than Foo (int i, long l = 0)
3962                         //  Foo (params int[] args) is better than Foo (int i = 0, params int[] args)
3963                         //
3964                         // Prefer non-optional version
3965                         //
3966                         // LAMESPEC: Specification claims this should be done at last but the opposite is true
3967                         //
3968                         if (candidate_params == best_params && candidate_pd.Count != best_pd.Count) {
3969                                 if (candidate_pd.Count >= best_pd.Count)
3970                                         return false;
3971
3972                                 if (j < candidate_pd.Count && candidate_pd.FixedParameters[j].HasDefaultValue)
3973                                         return false;
3974
3975                                 return true;
3976                         }
3977
3978                         //
3979                         // One is a non-generic method and second is a generic method, then non-generic is better
3980                         //
3981                         if (best.IsGeneric != candidate.IsGeneric)
3982                                 return best.IsGeneric;
3983
3984                         //
3985                         // This handles the following cases:
3986                         //
3987                         //   Trim () is better than Trim (params char[] chars)
3988                         //   Concat (string s1, string s2, string s3) is better than
3989                         //     Concat (string s1, params string [] srest)
3990                         //   Foo (int, params int [] rest) is better than Foo (params int [] rest)
3991                         //
3992                         // Prefer non-expanded version
3993                         //
3994                         if (candidate_params != best_params)
3995                                 return best_params;
3996
3997                         int candidate_param_count = candidate_pd.Count;
3998                         int best_param_count = best_pd.Count;
3999
4000                         if (candidate_param_count != best_param_count)
4001                                 // can only happen if (candidate_params && best_params)
4002                                 return candidate_param_count > best_param_count && best_pd.HasParams;
4003
4004                         //
4005                         // Both methods have the same number of parameters, and the parameters have equal types
4006                         // Pick the "more specific" signature using rules over original (non-inflated) types
4007                         //
4008                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
4009                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
4010
4011                         bool specific_at_least_once = false;
4012                         for (j = 0; j < args_count; ++j) {
4013                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
4014                                 if (na != null) {
4015                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
4016                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
4017                                 } else {
4018                                         ct = candidate_def_pd.Types[j];
4019                                         bt = best_def_pd.Types[j];
4020                                 }
4021
4022                                 if (ct == bt)
4023                                         continue;
4024                                 TypeSpec specific = MoreSpecific (ct, bt);
4025                                 if (specific == bt)
4026                                         return false;
4027                                 if (specific == ct)
4028                                         specific_at_least_once = true;
4029                         }
4030
4031                         if (specific_at_least_once)
4032                                 return true;
4033
4034                         return false;
4035                 }
4036
4037                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4038                 {
4039                         rc.Report.Error (1729, loc,
4040                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4041                                 type.GetSignatureForError (), argCount.ToString ());
4042                 }
4043
4044                 //
4045                 // Determines if the candidate method is applicable to the given set of arguments
4046                 // There could be two different set of parameters for same candidate where one
4047                 // is the closest override for default values and named arguments checks and second
4048                 // one being the virtual base for the parameter types and modifiers.
4049                 //
4050                 // A return value rates candidate method compatibility,
4051                 // 0 = the best, int.MaxValue = the worst
4052                 // -1 = fatal error
4053                 //
4054                 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)
4055                 {
4056                         // Parameters of most-derived type used mainly for named and optional parameters
4057                         var pd = pm.Parameters;
4058
4059                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4060                         // params modifier instead of most-derived type
4061                         var cpd = ((IParametersMember) candidate).Parameters;
4062                         int param_count = pd.Count;
4063                         int optional_count = 0;
4064                         int score;
4065                         Arguments orig_args = arguments;
4066
4067                         if (arg_count != param_count) {
4068                                 //
4069                                 // No arguments expansion when doing exact match for delegates
4070                                 //
4071                                 if ((restrictions & Restrictions.CovariantDelegate) == 0) {
4072                                         for (int i = 0; i < pd.Count; ++i) {
4073                                                 if (pd.FixedParameters[i].HasDefaultValue) {
4074                                                         optional_count = pd.Count - i;
4075                                                         break;
4076                                                 }
4077                                         }
4078                                 }
4079
4080                                 if (optional_count != 0) {
4081                                         // Readjust expected number when params used
4082                                         if (cpd.HasParams) {
4083                                                 optional_count--;
4084                                                 if (arg_count < param_count)
4085                                                         param_count--;
4086                                         } else if (arg_count > param_count) {
4087                                                 int args_gap = System.Math.Abs (arg_count - param_count);
4088                                                 return int.MaxValue - 10000 + args_gap;
4089                                         }
4090                                 } else if (arg_count != param_count) {
4091                                         int args_gap = System.Math.Abs (arg_count - param_count);
4092                                         if (!cpd.HasParams)
4093                                                 return int.MaxValue - 10000 + args_gap;
4094                                         if (arg_count < param_count - 1)
4095                                                 return int.MaxValue - 10000 + args_gap;
4096                                 }
4097
4098                                 // Resize to fit optional arguments
4099                                 if (optional_count != 0) {
4100                                         if (arguments == null) {
4101                                                 arguments = new Arguments (optional_count);
4102                                         } else {
4103                                                 // Have to create a new container, so the next run can do same
4104                                                 var resized = new Arguments (param_count);
4105                                                 resized.AddRange (arguments);
4106                                                 arguments = resized;
4107                                         }
4108
4109                                         for (int i = arg_count; i < param_count; ++i)
4110                                                 arguments.Add (null);
4111                                 }
4112                         }
4113
4114                         if (arg_count > 0) {
4115                                 //
4116                                 // Shuffle named arguments to the right positions if there are any
4117                                 //
4118                                 if (arguments[arg_count - 1] is NamedArgument) {
4119                                         arg_count = arguments.Count;
4120
4121                                         for (int i = 0; i < arg_count; ++i) {
4122                                                 bool arg_moved = false;
4123                                                 while (true) {
4124                                                         NamedArgument na = arguments[i] as NamedArgument;
4125                                                         if (na == null)
4126                                                                 break;
4127
4128                                                         int index = pd.GetParameterIndexByName (na.Name);
4129
4130                                                         // Named parameter not found
4131                                                         if (index < 0)
4132                                                                 return (i + 1) * 3;
4133
4134                                                         // already reordered
4135                                                         if (index == i)
4136                                                                 break;
4137
4138                                                         Argument temp;
4139                                                         if (index >= param_count) {
4140                                                                 // When using parameters which should not be available to the user
4141                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
4142                                                                         break;
4143
4144                                                                 arguments.Add (null);
4145                                                                 ++arg_count;
4146                                                                 temp = null;
4147                                                         } else {
4148                                                                 temp = arguments[index];
4149
4150                                                                 // The slot has been taken by positional argument
4151                                                                 if (temp != null && !(temp is NamedArgument))
4152                                                                         break;
4153                                                         }
4154
4155                                                         if (!arg_moved) {
4156                                                                 arguments = arguments.MarkOrderedArgument (na);
4157                                                                 arg_moved = true;
4158                                                         }
4159
4160                                                         arguments[index] = arguments[i];
4161                                                         arguments[i] = temp;
4162
4163                                                         if (temp == null)
4164                                                                 break;
4165                                                 }
4166                                         }
4167                                 } else {
4168                                         arg_count = arguments.Count;
4169                                 }
4170                         } else if (arguments != null) {
4171                                 arg_count = arguments.Count;
4172                         }
4173
4174                         //
4175                         // Don't do any expensive checks when the candidate cannot succeed
4176                         //
4177                         if (arg_count != param_count && !cpd.HasParams)
4178                                 return (param_count - arg_count) * 2 + 1;
4179
4180                         var dep = candidate.GetMissingDependencies ();
4181                         if (dep != null) {
4182                                 ImportedTypeDefinition.Error_MissingDependency (ec, dep, loc);
4183                                 return -1;
4184                         }
4185
4186                         //
4187                         // 1. Handle generic method using type arguments when specified or type inference
4188                         //
4189                         TypeSpec[] ptypes;
4190                         var ms = candidate as MethodSpec;
4191                         if (ms != null && ms.IsGeneric) {
4192                                 // Setup constraint checker for probing only
4193                                 ConstraintChecker cc = new ConstraintChecker (null);
4194
4195                                 if (type_arguments != null) {
4196                                         var g_args_count = ms.Arity;
4197                                         if (g_args_count != type_arguments.Count)
4198                                                 return int.MaxValue - 20000 + System.Math.Abs (type_arguments.Count - g_args_count);
4199
4200                                         ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
4201                                 } else {
4202                                         //
4203                                         // Deploy custom error reporting for infered anonymous expression or lambda methods. When
4204                                         // probing lambda methods keep all errors reported in separate set and once we are done and no best
4205                                         // candidate was found use the set to report more details about what was wrong with lambda body.
4206                                         // The general idea is to distinguish between code errors and errors caused by
4207                                         // trial-and-error type inference
4208                                         //
4209                                         if (lambda_conv_msgs == null) {
4210                                                 for (int i = 0; i < arg_count; i++) {
4211                                                         Argument a = arguments[i];
4212                                                         if (a == null)
4213                                                                 continue;
4214
4215                                                         var am = a.Expr as AnonymousMethodExpression;
4216                                                         if (am != null) {
4217                                                                 if (lambda_conv_msgs == null)
4218                                                                         lambda_conv_msgs = new SessionReportPrinter ();
4219
4220                                                                 am.TypeInferenceReportPrinter = lambda_conv_msgs;
4221                                                         }
4222                                                 }
4223                                         }
4224
4225                                         var ti = new TypeInference (arguments);
4226                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
4227
4228                                         if (i_args == null)
4229                                                 return ti.InferenceScore - 20000;
4230
4231                                         //
4232                                         // Clear any error messages when the result was success
4233                                         //
4234                                         if (lambda_conv_msgs != null)
4235                                                 lambda_conv_msgs.ClearSession ();
4236
4237                                         if (i_args.Length != 0) {
4238                                                 ms = ms.MakeGenericMethod (ec, i_args);
4239                                         }
4240
4241                                         cc.IgnoreInferredDynamic = true;
4242                                 }
4243
4244                                 //
4245                                 // Type arguments constraints have to match for the method to be applicable
4246                                 //
4247                                 if (!cc.CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc)) {
4248                                         candidate = ms;
4249                                         return int.MaxValue - 25000;
4250                                 }
4251
4252                                 //
4253                                 // We have a generic return type and at same time the method is override which
4254                                 // means we have to also inflate override return type in case the candidate is
4255                                 // best candidate and override return type is different to base return type.
4256                                 //
4257                                 // virtual Foo<T, object> with override Foo<T, dynamic>
4258                                 //
4259                                 if (candidate != pm) {
4260                                         MethodSpec override_ms = (MethodSpec) pm;
4261                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
4262                                         returnType = inflator.Inflate (returnType);
4263                                 } else {
4264                                         returnType = ms.ReturnType;
4265                                 }
4266
4267                                 candidate = ms;
4268                                 ptypes = ms.Parameters.Types;
4269                         } else {
4270                                 if (type_arguments != null)
4271                                         return int.MaxValue - 15000;
4272
4273                                 ptypes = cpd.Types;
4274                         }
4275
4276                         //
4277                         // 2. Each argument has to be implicitly convertible to method parameter
4278                         //
4279                         Parameter.Modifier p_mod = 0;
4280                         TypeSpec pt = null;
4281
4282                         for (int i = 0; i < arg_count; i++) {
4283                                 Argument a = arguments[i];
4284                                 if (a == null) {
4285                                         var fp = pd.FixedParameters[i];
4286                                         if (!fp.HasDefaultValue) {
4287                                                 arguments = orig_args;
4288                                                 return arg_count * 2 + 2;
4289                                         }
4290
4291                                         //
4292                                         // Get the default value expression, we can use the same expression
4293                                         // if the type matches
4294                                         //
4295                                         Expression e = fp.DefaultValue;
4296                                         if (!(e is Constant) || e.Type.IsGenericOrParentIsGeneric || e.Type.IsGenericParameter) {
4297                                                 //
4298                                                 // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
4299                                                 //
4300                                                 if (e == EmptyExpression.MissingValue && ptypes[i].BuiltinType == BuiltinTypeSpec.Type.Object || ptypes[i].BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
4301                                                         e = new MemberAccess (new MemberAccess (new MemberAccess (
4302                                                                 new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
4303                                                 } else {
4304                                                         e = new DefaultValueExpression (new TypeExpression (ptypes [i], loc), loc);
4305                                                 }
4306
4307                                                 e = e.Resolve (ec);
4308                                         }
4309
4310                                         if ((fp.ModFlags & Parameter.Modifier.CallerMask) != 0) {
4311                                                 //
4312                                                 // LAMESPEC: Attributes can be mixed together with build-in priority
4313                                                 //
4314                                                 if ((fp.ModFlags & Parameter.Modifier.CallerLineNumber) != 0) {
4315                                                         e = new IntLiteral (ec.BuiltinTypes, loc.Row, loc);
4316                                                 } else if ((fp.ModFlags & Parameter.Modifier.CallerFilePath) != 0) {
4317                                                         e = new StringLiteral (ec.BuiltinTypes, loc.NameFullPath, loc);
4318                                                 } else if (ec.MemberContext.CurrentMemberDefinition != null) {
4319                                                         e = new StringLiteral (ec.BuiltinTypes, ec.MemberContext.CurrentMemberDefinition.GetCallerMemberName (), loc);
4320                                                 }
4321                                         }
4322
4323                                         arguments[i] = new Argument (e, Argument.AType.Default);
4324                                         continue;
4325                                 }
4326
4327                                 if (p_mod != Parameter.Modifier.PARAMS) {
4328                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
4329                                         pt = ptypes [i];
4330                                 } else if (!params_expanded_form) {
4331                                         params_expanded_form = true;
4332                                         pt = ((ElementTypeSpec) pt).Element;
4333                                         i -= 2;
4334                                         continue;
4335                                 }
4336
4337                                 score = 1;
4338                                 if (!params_expanded_form) {
4339                                         if (a.ArgType == Argument.AType.ExtensionType) {
4340                                                 //
4341                                                 // Indentity, implicit reference or boxing conversion must exist for the extension parameter
4342                                                 //
4343                                                 // LAMESPEC: or implicit type parameter conversion
4344                                                 //
4345                                                 var at = a.Type;
4346                                                 if (at == pt || TypeSpecComparer.IsEqual (at, pt) ||
4347                                                         Convert.ImplicitReferenceConversionExists (at, pt, false) ||
4348                                                         Convert.ImplicitBoxingConversion (null, at, pt) != null) {
4349                                                         score = 0;
4350                                                         continue;
4351                                                 }
4352                                         } else {
4353                                                 score = IsArgumentCompatible (ec, a, p_mod, pt);
4354
4355                                                 if (score < 0)
4356                                                         dynamicArgument = true;
4357                                         }
4358                                 }
4359
4360                                 //
4361                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
4362                                 //
4363                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
4364                                         if (!params_expanded_form)
4365                                                 pt = ((ElementTypeSpec) pt).Element;
4366
4367                                         if (score > 0)
4368                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
4369
4370                                         if (score == 0) {
4371                                                 params_expanded_form = true;
4372                                         } else if (score < 0) {
4373                                                 params_expanded_form = true;
4374                                                 dynamicArgument = true;
4375                                         }
4376                                 }
4377
4378                                 if (score > 0) {
4379                                         if (params_expanded_form)
4380                                                 ++score;
4381                                         return (arg_count - i) * 2 + score;
4382                                 }
4383                         }
4384
4385                         //
4386                         // When params parameter has no argument it will be provided later if the method is the best candidate
4387                         //
4388                         if (arg_count + 1 == pd.Count && (cpd.FixedParameters [arg_count].ModFlags & Parameter.Modifier.PARAMS) != 0)
4389                                 params_expanded_form = true;
4390
4391                         //
4392                         // Restore original arguments for dynamic binder to keep the intention of original source code
4393                         //
4394                         if (dynamicArgument)
4395                                 arguments = orig_args;
4396
4397                         return 0;
4398                 }
4399
4400                 //
4401                 // Tests argument compatibility with the parameter
4402                 // The possible return values are
4403                 // 0 - success
4404                 // 1 - modifier mismatch
4405                 // 2 - type mismatch
4406                 // -1 - dynamic binding required
4407                 //
4408                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
4409                 {
4410                         //
4411                         // Types have to be identical when ref or out modifer
4412                         // is used and argument is not of dynamic type
4413                         //
4414                         if (((argument.Modifier | param_mod) & Parameter.Modifier.RefOutMask) != 0) {
4415                                 if (argument.Type != parameter) {
4416                                         //
4417                                         // Do full equality check after quick path
4418                                         //
4419                                         if (!TypeSpecComparer.IsEqual (argument.Type, parameter)) {
4420                                                 //
4421                                                 // Using dynamic for ref/out parameter can still succeed at runtime
4422                                                 //
4423                                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4424                                                         return -1;
4425
4426                                                 return 2;
4427                                         }
4428                                 }
4429
4430                                 if ((argument.Modifier & Parameter.Modifier.RefOutMask) != (param_mod & Parameter.Modifier.RefOutMask)) {
4431                                         //
4432                                         // Using dynamic for ref/out parameter can still succeed at runtime
4433                                         //
4434                                         if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4435                                                 return -1;
4436
4437                                         return 1;
4438                                 }
4439
4440                         } else {
4441                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
4442                                         return -1;
4443
4444                                 //
4445                                 // Use implicit conversion in all modes to return same candidates when the expression
4446                                 // is used as argument or delegate conversion
4447                                 //
4448                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
4449                                         return 2;
4450                                 }
4451                         }
4452
4453                         return 0;
4454                 }
4455
4456                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
4457                 {
4458                         if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
4459                                 return q;
4460                         if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
4461                                 return p;
4462
4463                         var ac_p = p as ArrayContainer;
4464                         if (ac_p != null) {
4465                                 var ac_q = q as ArrayContainer;
4466                                 if (ac_q == null)
4467                                         return null;
4468
4469                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
4470                                 if (specific == ac_p.Element)
4471                                         return p;
4472                                 if (specific == ac_q.Element)
4473                                         return q;
4474                         } else if (TypeManager.IsGenericType (p)) {
4475                                 var pargs = TypeManager.GetTypeArguments (p);
4476                                 var qargs = TypeManager.GetTypeArguments (q);
4477
4478                                 bool p_specific_at_least_once = false;
4479                                 bool q_specific_at_least_once = false;
4480
4481                                 for (int i = 0; i < pargs.Length; i++) {
4482                                         TypeSpec specific = MoreSpecific (pargs[i], qargs[i]);
4483                                         if (specific == pargs[i])
4484                                                 p_specific_at_least_once = true;
4485                                         if (specific == qargs[i])
4486                                                 q_specific_at_least_once = true;
4487                                 }
4488
4489                                 if (p_specific_at_least_once && !q_specific_at_least_once)
4490                                         return p;
4491                                 if (!p_specific_at_least_once && q_specific_at_least_once)
4492                                         return q;
4493                         }
4494
4495                         return null;
4496                 }
4497
4498                 //
4499                 // Find the best method from candidate list
4500                 //
4501                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
4502                 {
4503                         List<AmbiguousCandidate> ambiguous_candidates = null;
4504
4505                         MemberSpec best_candidate;
4506                         Arguments best_candidate_args = null;
4507                         bool best_candidate_params = false;
4508                         bool best_candidate_dynamic = false;
4509                         int best_candidate_rate;
4510                         IParametersMember best_parameter_member = null;
4511
4512                         int args_count = args != null ? args.Count : 0;
4513
4514                         Arguments candidate_args = args;
4515                         bool error_mode = false;
4516                         MemberSpec invocable_member = null;
4517
4518                         while (true) {
4519                                 best_candidate = null;
4520                                 best_candidate_rate = int.MaxValue;
4521
4522                                 var type_members = members;
4523                                 do {
4524                                         for (int i = 0; i < type_members.Count; ++i) {
4525                                                 var member = type_members[i];
4526
4527                                                 //
4528                                                 // Methods in a base class are not candidates if any method in a derived
4529                                                 // class is applicable
4530                                                 //
4531                                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
4532                                                         continue;
4533
4534                                                 if (!error_mode) {
4535                                                         if (!member.IsAccessible (rc))
4536                                                                 continue;
4537
4538                                                         if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
4539                                                                 continue;
4540
4541                                                         if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
4542                                                                 instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
4543                                                                 continue;
4544                                                         }
4545                                                 }
4546
4547                                                 IParametersMember pm = member as IParametersMember;
4548                                                 if (pm == null) {
4549                                                         //
4550                                                         // Will use it later to report ambiguity between best method and invocable member
4551                                                         //
4552                                                         if (Invocation.IsMemberInvocable (member))
4553                                                                 invocable_member = member;
4554
4555                                                         continue;
4556                                                 }
4557
4558                                                 //
4559                                                 // Overload resolution is looking for base member but using parameter names
4560                                                 // and default values from the closest member. That means to do expensive lookup
4561                                                 // for the closest override for virtual or abstract members
4562                                                 //
4563                                                 if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
4564                                                         var override_params = base_provider.GetOverrideMemberParameters (member);
4565                                                         if (override_params != null)
4566                                                                 pm = override_params;
4567                                                 }
4568
4569                                                 //
4570                                                 // Check if the member candidate is applicable
4571                                                 //
4572                                                 bool params_expanded_form = false;
4573                                                 bool dynamic_argument = false;
4574                                                 TypeSpec rt = pm.MemberType;
4575                                                 int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt);
4576
4577                                                 if (lambda_conv_msgs != null)
4578                                                         lambda_conv_msgs.EndSession ();
4579
4580                                                 //
4581                                                 // How does it score compare to others
4582                                                 //
4583                                                 if (candidate_rate < best_candidate_rate) {
4584
4585                                                         // Fatal error (missing dependency), cannot continue
4586                                                         if (candidate_rate < 0)
4587                                                                 return null;
4588
4589                                                         best_candidate_rate = candidate_rate;
4590                                                         best_candidate = member;
4591                                                         best_candidate_args = candidate_args;
4592                                                         best_candidate_params = params_expanded_form;
4593                                                         best_candidate_dynamic = dynamic_argument;
4594                                                         best_parameter_member = pm;
4595                                                         best_candidate_return_type = rt;
4596                                                 } else if (candidate_rate == 0) {
4597                                                         //
4598                                                         // The member look is done per type for most operations but sometimes
4599                                                         // it's not possible like for binary operators overload because they
4600                                                         // are unioned between 2 sides
4601                                                         //
4602                                                         if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
4603                                                                 if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
4604                                                                         continue;
4605                                                         }
4606
4607                                                         bool is_better;
4608                                                         if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
4609                                                                 //
4610                                                                 // We pack all interface members into top level type which makes the overload resolution
4611                                                                 // more complicated for interfaces. We compensate it by removing methods with same
4612                                                                 // signature when building the cache hence this path should not really be hit often
4613                                                                 //
4614                                                                 // Example:
4615                                                                 // interface IA { void Foo (int arg); }
4616                                                                 // interface IB : IA { void Foo (params int[] args); }
4617                                                                 //
4618                                                                 // IB::Foo is the best overload when calling IB.Foo (1)
4619                                                                 //
4620                                                                 is_better = true;
4621                                                                 if (ambiguous_candidates != null) {
4622                                                                         foreach (var amb_cand in ambiguous_candidates) {
4623                                                                                 if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
4624                                                                                         continue;
4625                                                                                 }
4626
4627                                                                                 is_better = false;
4628                                                                                 break;
4629                                                                         }
4630
4631                                                                         if (is_better)
4632                                                                                 ambiguous_candidates = null;
4633                                                                 }
4634                                                         } else {
4635                                                                 // Is the new candidate better
4636                                                                 is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
4637                                                         }
4638
4639                                                         if (is_better) {
4640                                                                 best_candidate = member;
4641                                                                 best_candidate_args = candidate_args;
4642                                                                 best_candidate_params = params_expanded_form;
4643                                                                 best_candidate_dynamic = dynamic_argument;
4644                                                                 best_parameter_member = pm;
4645                                                                 best_candidate_return_type = rt;
4646                                                         } else {
4647                                                                 // It's not better but any other found later could be but we are not sure yet
4648                                                                 if (ambiguous_candidates == null)
4649                                                                         ambiguous_candidates = new List<AmbiguousCandidate> ();
4650
4651                                                                 ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
4652                                                         }
4653                                                 }
4654
4655                                                 // Restore expanded arguments
4656                                                 if (candidate_args != args)
4657                                                         candidate_args = args;
4658                                         }
4659                                 } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType.BaseType)) != null);
4660
4661                                 //
4662                                 // We've found exact match
4663                                 //
4664                                 if (best_candidate_rate == 0)
4665                                         break;
4666
4667                                 //
4668                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
4669                                 //
4670                                 if (!error_mode) {
4671                                         var emg = base_provider.LookupExtensionMethod (rc);
4672                                         if (emg != null) {
4673                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
4674                                                 if (emg != null) {
4675                                                         best_candidate_extension_group = emg;
4676                                                         return (T) (MemberSpec) emg.BestCandidate;
4677                                                 }
4678                                         }
4679                                 }
4680
4681                                 // Don't run expensive error reporting mode for probing
4682                                 if (IsProbingOnly)
4683                                         return null;
4684
4685                                 if (error_mode)
4686                                         break;
4687
4688                                 if (lambda_conv_msgs != null && !lambda_conv_msgs.IsEmpty)
4689                                         break;
4690
4691                                 lambda_conv_msgs = null;
4692                                 error_mode = true;
4693                         }
4694
4695                         //
4696                         // No best member match found, report an error
4697                         //
4698                         if (best_candidate_rate != 0 || error_mode) {
4699                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
4700                                 return null;
4701                         }
4702
4703                         if (best_candidate_dynamic) {
4704                                 if (args[0].ArgType == Argument.AType.ExtensionType) {
4705                                         rc.Report.Error (1973, loc,
4706                                                 "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",
4707                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
4708                                 }
4709
4710                                 BestCandidateIsDynamic = true;
4711                                 return null;
4712                         }
4713
4714                         //
4715                         // These flags indicates we are running delegate probing conversion. No need to
4716                         // do more expensive checks
4717                         //
4718                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
4719                                 return (T) best_candidate;
4720
4721                         if (ambiguous_candidates != null) {
4722                                 //
4723                                 // Now check that there are no ambiguities i.e the selected method
4724                                 // should be better than all the others
4725                                 //
4726                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
4727                                         var candidate = ambiguous_candidates [ix];
4728
4729                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
4730                                                 var ambiguous = candidate.Member;
4731                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
4732                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
4733                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
4734                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
4735                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
4736                                                 }
4737
4738                                                 return (T) best_candidate;
4739                                         }
4740                                 }
4741                         }
4742
4743                         if (invocable_member != null) {
4744                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4745                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
4746                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
4747                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
4748                         }
4749
4750                         //
4751                         // And now check if the arguments are all
4752                         // compatible, perform conversions if
4753                         // necessary etc. and return if everything is
4754                         // all right
4755                         //
4756                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
4757                                 return null;
4758
4759                         if (best_candidate == null)
4760                                 return null;
4761
4762                         //
4763                         // Check ObsoleteAttribute on the best method
4764                         //
4765                         ObsoleteAttribute oa = best_candidate.GetAttributeObsolete ();
4766                         if (oa != null && !rc.IsObsolete)
4767                                 AttributeTester.Report_ObsoleteMessage (oa, best_candidate.GetSignatureForError (), loc, rc.Report);
4768
4769                         best_candidate.MemberDefinition.SetIsUsed ();
4770
4771                         args = best_candidate_args;
4772                         return (T) best_candidate;
4773                 }
4774
4775                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
4776                 {
4777                         return ResolveMember<MethodSpec> (rc, ref args);
4778                 }
4779
4780                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
4781                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
4782                 {
4783                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
4784                                 return;
4785
4786                         if (a.Type == InternalType.ErrorType)
4787                                 return;
4788
4789                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
4790                                 ec.Report.SymbolRelatedToPreviousError (method);
4791                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
4792                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have 'ref', or `out' modifier",
4793                                                 TypeManager.CSharpSignature (method));
4794                                         return;
4795                                 }
4796                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
4797                                           TypeManager.CSharpSignature (method));
4798                         } else if (IsDelegateInvoke) {
4799                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
4800                                         DelegateType.GetSignatureForError ());
4801                         } else {
4802                                 ec.Report.SymbolRelatedToPreviousError (method);
4803                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
4804                                         method.GetSignatureForError ());
4805                         }
4806
4807                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
4808
4809                         string index = (idx + 1).ToString ();
4810                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
4811                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
4812                                         ec.Report.Error (1615, loc, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
4813                                                 index, Parameter.GetModifierSignature (a.Modifier));
4814                                 else
4815                                         ec.Report.Error (1620, loc, "Argument `#{0}' is missing `{1}' modifier",
4816                                                 index, Parameter.GetModifierSignature (mod));
4817                         } else {
4818                                 string p1 = a.GetSignatureForError ();
4819                                 string p2 = TypeManager.CSharpName (paramType);
4820
4821                                 if (p1 == p2) {
4822                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
4823                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
4824                                 }
4825
4826                                 ec.Report.Error (1503, loc,
4827                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
4828                         }
4829                 }
4830
4831                 //
4832                 // We have failed to find exact match so we return error info about the closest match
4833                 //
4834                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
4835                 {
4836                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
4837                         int arg_count = args == null ? 0 : args.Count;
4838
4839                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
4840                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
4841                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, ta_count, loc);
4842                                 return;
4843                         }
4844
4845                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
4846                                 return;
4847                         }
4848
4849
4850                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
4851                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
4852                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
4853                         }
4854
4855                         //
4856                         // For candidates which match on parameters count report more details about incorrect arguments
4857                         //
4858                         if (pm != null) {
4859                                 int unexpanded_count = ((IParametersMember) best_candidate).Parameters.HasParams ? pm.Parameters.Count - 1 : pm.Parameters.Count;
4860                                 if (pm.Parameters.Count == arg_count || params_expanded || unexpanded_count == arg_count) {
4861                                         // Reject any inaccessible member
4862                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
4863                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4864                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
4865                                                 return;
4866                                         }
4867
4868                                         var ms = best_candidate as MethodSpec;
4869                                         if (ms != null && ms.IsGeneric) {
4870                                                 bool constr_ok = true;
4871                                                 if (ms.TypeArguments != null)
4872                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
4873
4874                                                 if (ta_count == 0) {
4875                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
4876                                                                 return;
4877
4878                                                         if (constr_ok) {
4879                                                                 rc.Report.Error (411, loc,
4880                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
4881                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
4882                                                         }
4883
4884                                                         return;
4885                                                 }
4886                                         }
4887
4888                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
4889                                         return;
4890                                 }
4891                         }
4892
4893                         //
4894                         // We failed to find any method with correct argument count, report best candidate
4895                         //
4896                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
4897                                 return;
4898
4899                         if (best_candidate.Kind == MemberKind.Constructor) {
4900                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4901                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
4902                         } else if (IsDelegateInvoke) {
4903                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
4904                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
4905                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
4906                         } else {
4907                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
4908                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4909                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
4910                                         name, arg_count.ToString ());
4911                         }
4912                 }
4913
4914                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
4915                 {
4916                         var pd = pm.Parameters;
4917                         TypeSpec[] ptypes = ((IParametersMember) member).Parameters.Types;
4918
4919                         Parameter.Modifier p_mod = 0;
4920                         TypeSpec pt = null;
4921                         int a_idx = 0, a_pos = 0;
4922                         Argument a = null;
4923                         ArrayInitializer params_initializers = null;
4924                         bool has_unsafe_arg = pm.MemberType.IsPointer;
4925                         int arg_count = args == null ? 0 : args.Count;
4926
4927                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
4928                                 a = args[a_idx];
4929                                 if (p_mod != Parameter.Modifier.PARAMS) {
4930                                         p_mod = pd.FixedParameters[a_idx].ModFlags;
4931                                         pt = ptypes[a_idx];
4932                                         has_unsafe_arg |= pt.IsPointer;
4933
4934                                         if (p_mod == Parameter.Modifier.PARAMS) {
4935                                                 if (chose_params_expanded) {
4936                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
4937                                                         pt = TypeManager.GetElementType (pt);
4938                                                 }
4939                                         }
4940                                 }
4941
4942                                 //
4943                                 // Types have to be identical when ref or out modifer is used
4944                                 //
4945                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
4946                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
4947                                                 break;
4948
4949                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt))
4950                                                 continue;
4951
4952                                         break;
4953                                 }
4954
4955                                 NamedArgument na = a as NamedArgument;
4956                                 if (na != null) {
4957                                         int name_index = pd.GetParameterIndexByName (na.Name);
4958                                         if (name_index < 0 || name_index >= pd.Count) {
4959                                                 if (IsDelegateInvoke) {
4960                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
4961                                                         ec.Report.Error (1746, na.Location,
4962                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
4963                                                                 DelegateType.GetSignatureForError (), na.Name);
4964                                                 } else {
4965                                                         ec.Report.SymbolRelatedToPreviousError (member);
4966                                                         ec.Report.Error (1739, na.Location,
4967                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
4968                                                                 TypeManager.CSharpSignature (member), na.Name);
4969                                                 }
4970                                         } else if (args[name_index] != a) {
4971                                                 if (IsDelegateInvoke)
4972                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
4973                                                 else
4974                                                         ec.Report.SymbolRelatedToPreviousError (member);
4975
4976                                                 ec.Report.Error (1744, na.Location,
4977                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
4978                                                         na.Name);
4979                                         }
4980                                 }
4981
4982                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4983                                         continue;
4984
4985                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
4986                                         custom_errors.NoArgumentMatch (ec, member);
4987                                         return false;
4988                                 }
4989
4990                                 Expression conv = null;
4991                                 if (a.ArgType == Argument.AType.ExtensionType) {
4992                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
4993                                                 conv = a.Expr;
4994                                         } else {
4995                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
4996                                                 if (conv == null)
4997                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
4998                                         }
4999                                 } else {
5000                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
5001                                 }
5002
5003                                 if (conv == null)
5004                                         break;
5005
5006                                 //
5007                                 // Convert params arguments to an array initializer
5008                                 //
5009                                 if (params_initializers != null) {
5010                                         // we choose to use 'a.Expr' rather than 'conv' so that
5011                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
5012                                         params_initializers.Add (a.Expr);
5013                                         args.RemoveAt (a_idx--);
5014                                         --arg_count;
5015                                         continue;
5016                                 }
5017
5018                                 // Update the argument with the implicit conversion
5019                                 a.Expr = conv;
5020                         }
5021
5022                         if (a_idx != arg_count) {
5023                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
5024                                 return false;
5025                         }
5026
5027                         //
5028                         // Fill not provided arguments required by params modifier
5029                         //
5030                         if (params_initializers == null && pd.HasParams && arg_count + 1 == pd.Count) {
5031                                 if (args == null)
5032                                         args = new Arguments (1);
5033
5034                                 pt = ptypes[pd.Count - 1];
5035                                 pt = TypeManager.GetElementType (pt);
5036                                 has_unsafe_arg |= pt.IsPointer;
5037                                 params_initializers = new ArrayInitializer (0, loc);
5038                         }
5039
5040                         //
5041                         // Append an array argument with all params arguments
5042                         //
5043                         if (params_initializers != null) {
5044                                 args.Add (new Argument (
5045                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
5046                                 arg_count++;
5047                         }
5048
5049                         if (has_unsafe_arg && !ec.IsUnsafe) {
5050                                 Expression.UnsafeError (ec, loc);
5051                         }
5052
5053                         //
5054                         // We could infer inaccesible type arguments
5055                         //
5056                         if (type_arguments == null && member.IsGeneric) {
5057                                 var ms = (MethodSpec) member;
5058                                 foreach (var ta in ms.TypeArguments) {
5059                                         if (!ta.IsAccessible (ec)) {
5060                                                 ec.Report.SymbolRelatedToPreviousError (ta);
5061                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
5062                                                 break;
5063                                         }
5064                                 }
5065                         }
5066
5067                         return true;
5068                 }
5069         }
5070
5071         public class ConstantExpr : MemberExpr
5072         {
5073                 readonly ConstSpec constant;
5074
5075                 public ConstantExpr (ConstSpec constant, Location loc)
5076                 {
5077                         this.constant = constant;
5078                         this.loc = loc;
5079                 }
5080
5081                 public override string Name {
5082                         get { throw new NotImplementedException (); }
5083                 }
5084
5085                 public override string KindName {
5086                         get { return "constant"; }
5087                 }
5088
5089                 public override bool IsInstance {
5090                         get { return !IsStatic; }
5091                 }
5092
5093                 public override bool IsStatic {
5094                         get { return true; }
5095                 }
5096
5097                 protected override TypeSpec DeclaringType {
5098                         get { return constant.DeclaringType; }
5099                 }
5100
5101                 public override Expression CreateExpressionTree (ResolveContext ec)
5102                 {
5103                         throw new NotSupportedException ("ET");
5104                 }
5105
5106                 protected override Expression DoResolve (ResolveContext rc)
5107                 {
5108                         ResolveInstanceExpression (rc, null);
5109                         DoBestMemberChecks (rc, constant);
5110
5111                         var c = constant.GetConstant (rc);
5112
5113                         // Creates reference expression to the constant value
5114                         return Constant.CreateConstant (constant.MemberType, c.GetValue (), loc);
5115                 }
5116
5117                 public override void Emit (EmitContext ec)
5118                 {
5119                         throw new NotSupportedException ();
5120                 }
5121
5122                 public override string GetSignatureForError ()
5123                 {
5124                         return constant.GetSignatureForError ();
5125                 }
5126
5127                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5128                 {
5129                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
5130                 }
5131         }
5132
5133         //
5134         // Fully resolved expression that references a Field
5135         //
5136         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
5137         {
5138                 protected FieldSpec spec;
5139                 VariableInfo variable_info;
5140
5141                 LocalTemporary temp;
5142                 bool prepared;
5143
5144                 protected FieldExpr (Location l)
5145                 {
5146                         loc = l;
5147                 }
5148
5149                 public FieldExpr (FieldSpec spec, Location loc)
5150                 {
5151                         this.spec = spec;
5152                         this.loc = loc;
5153
5154                         type = spec.MemberType;
5155                 }
5156
5157                 public FieldExpr (FieldBase fi, Location l)
5158                         : this (fi.Spec, l)
5159                 {
5160                 }
5161
5162                 #region Properties
5163
5164                 public override string Name {
5165                         get {
5166                                 return spec.Name;
5167                         }
5168                 }
5169
5170                 public bool IsHoisted {
5171                         get {
5172                                 IVariableReference hv = InstanceExpression as IVariableReference;
5173                                 return hv != null && hv.IsHoisted;
5174                         }
5175                 }
5176
5177                 public override bool IsInstance {
5178                         get {
5179                                 return !spec.IsStatic;
5180                         }
5181                 }
5182
5183                 public override bool IsStatic {
5184                         get {
5185                                 return spec.IsStatic;
5186                         }
5187                 }
5188
5189                 public override string KindName {
5190                         get { return "field"; }
5191                 }
5192
5193                 public FieldSpec Spec {
5194                         get {
5195                                 return spec;
5196                         }
5197                 }
5198
5199                 protected override TypeSpec DeclaringType {
5200                         get {
5201                                 return spec.DeclaringType;
5202                         }
5203                 }
5204
5205                 public VariableInfo VariableInfo {
5206                         get {
5207                                 return variable_info;
5208                         }
5209                 }
5210
5211 #endregion
5212
5213                 public override string GetSignatureForError ()
5214                 {
5215                         return spec.GetSignatureForError ();
5216                 }
5217
5218                 public bool IsMarshalByRefAccess (ResolveContext rc)
5219                 {
5220                         // Checks possible ldflda of field access expression
5221                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
5222                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
5223                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
5224                 }
5225
5226                 public void SetHasAddressTaken ()
5227                 {
5228                         IVariableReference vr = InstanceExpression as IVariableReference;
5229                         if (vr != null) {
5230                                 vr.SetHasAddressTaken ();
5231                         }
5232                 }
5233
5234                 public override Expression CreateExpressionTree (ResolveContext ec)
5235                 {
5236                         return CreateExpressionTree (ec, true);
5237                 }
5238
5239                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
5240                 {
5241                         Arguments args;
5242                         Expression instance;
5243
5244                         if (InstanceExpression == null) {
5245                                 instance = new NullLiteral (loc);
5246                         } else if (convertInstance) {
5247                                 instance = InstanceExpression.CreateExpressionTree (ec);
5248                         } else {
5249                                 args = new Arguments (1);
5250                                 args.Add (new Argument (InstanceExpression));
5251                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
5252                         }
5253
5254                         args = Arguments.CreateForExpressionTree (ec, null,
5255                                 instance,
5256                                 CreateTypeOfExpression ());
5257
5258                         return CreateExpressionFactoryCall (ec, "Field", args);
5259                 }
5260
5261                 public Expression CreateTypeOfExpression ()
5262                 {
5263                         return new TypeOfField (spec, loc);
5264                 }
5265
5266                 protected override Expression DoResolve (ResolveContext ec)
5267                 {
5268                         return DoResolve (ec, null);
5269                 }
5270
5271                 Expression DoResolve (ResolveContext ec, Expression rhs)
5272                 {
5273                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
5274
5275                         if (rhs != this) {
5276                                 if (ResolveInstanceExpression (ec, rhs)) {
5277                                         // Resolve the field's instance expression while flow analysis is turned
5278                                         // off: when accessing a field "a.b", we must check whether the field
5279                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
5280
5281                                         if (lvalue_instance) {
5282                                                 using (ec.With (ResolveContext.Options.DoFlowAnalysis, false)) {
5283                                                         bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
5284
5285                                                         Expression right_side =
5286                                                                 out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
5287
5288                                                         InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
5289                                                 }
5290                                         } else {
5291                                                 using (ec.With (ResolveContext.Options.DoFlowAnalysis, false)) {
5292                                                         InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
5293                                                 }
5294                                         }
5295
5296                                         if (InstanceExpression == null)
5297                                                 return null;
5298                                 }
5299
5300                                 DoBestMemberChecks (ec, spec);
5301                         }
5302
5303                         var fb = spec as FixedFieldSpec;
5304                         IVariableReference var = InstanceExpression as IVariableReference;
5305
5306                         if (lvalue_instance && var != null && var.VariableInfo != null) {
5307                                 var.VariableInfo.SetStructFieldAssigned (ec, Name);
5308                         }
5309
5310                         if (fb != null) {
5311                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5312                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
5313                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
5314                                 }
5315
5316                                 if (InstanceExpression.eclass != ExprClass.Variable) {
5317                                         ec.Report.SymbolRelatedToPreviousError (spec);
5318                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
5319                                                 TypeManager.GetFullNameSignature (spec));
5320                                 } else if (var != null && var.IsHoisted) {
5321                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
5322                                 }
5323
5324                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
5325                         }
5326
5327                         //
5328                         // Set flow-analysis variable info for struct member access. It will be check later
5329                         // for precise error reporting
5330                         //
5331                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
5332                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
5333                                 if (rhs != null && variable_info != null)
5334                                         variable_info.SetStructFieldAssigned (ec, Name);
5335                         }
5336
5337                         eclass = ExprClass.Variable;
5338                         return this;
5339                 }
5340
5341                 public void VerifyAssignedStructField (ResolveContext rc, Expression rhs)
5342                 {
5343                         var fe = this;
5344
5345                         do {
5346                                 var var = fe.InstanceExpression as IVariableReference;
5347                                 if (var != null) {
5348                                         var vi = var.VariableInfo;
5349
5350                                         if (vi != null && !vi.IsStructFieldAssigned (rc, fe.Name) && (rhs == null || !fe.type.IsStruct)) {
5351                                                 if (rhs != null) {
5352                                                         rc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5353                                                 } else {
5354                                                         rc.Report.Error (170, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5355                                                 }
5356
5357                                                 return;
5358                                         }
5359                                 }
5360
5361                                 fe = fe.InstanceExpression as FieldExpr;
5362
5363                         } while (fe != null);
5364                 }
5365
5366                 static readonly int [] codes = {
5367                         191,    // instance, write access
5368                         192,    // instance, out access
5369                         198,    // static, write access
5370                         199,    // static, out access
5371                         1648,   // member of value instance, write access
5372                         1649,   // member of value instance, out access
5373                         1650,   // member of value static, write access
5374                         1651    // member of value static, out access
5375                 };
5376
5377                 static readonly string [] msgs = {
5378                         /*0191*/ "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
5379                         /*0192*/ "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5380                         /*0198*/ "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5381                         /*0199*/ "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5382                         /*1648*/ "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
5383                         /*1649*/ "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5384                         /*1650*/ "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5385                         /*1651*/ "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)"
5386                 };
5387
5388                 // The return value is always null.  Returning a value simplifies calling code.
5389                 Expression Report_AssignToReadonly (ResolveContext ec, Expression right_side)
5390                 {
5391                         int i = 0;
5392                         if (right_side == EmptyExpression.OutAccess || right_side == EmptyExpression.LValueMemberOutAccess)
5393                                 i += 1;
5394                         if (IsStatic)
5395                                 i += 2;
5396                         if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess)
5397                                 i += 4;
5398                         ec.Report.Error (codes [i], loc, msgs [i], GetSignatureForError ());
5399
5400                         return null;
5401                 }
5402
5403                 override public Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5404                 {
5405                         Expression e = DoResolve (ec, right_side);
5406
5407                         if (e == null)
5408                                 return null;
5409
5410                         spec.MemberDefinition.SetIsAssigned ();
5411
5412                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
5413                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
5414                                 ec.Report.Warning (420, 1, loc,
5415                                         "`{0}': A volatile field references will not be treated as volatile",
5416                                         spec.GetSignatureForError ());
5417                         }
5418
5419                         if (spec.IsReadOnly) {
5420                                 // InitOnly fields can only be assigned in constructors or initializers
5421                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
5422                                         return Report_AssignToReadonly (ec, right_side);
5423
5424                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
5425
5426                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
5427                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
5428                                                 return Report_AssignToReadonly (ec, right_side);
5429                                         // static InitOnly fields cannot be assigned-to in an instance constructor
5430                                         if (IsStatic && !ec.IsStatic)
5431                                                 return Report_AssignToReadonly (ec, right_side);
5432                                         // instance constructors can't modify InitOnly fields of other instances of the same type
5433                                         if (!IsStatic && !(InstanceExpression is This))
5434                                                 return Report_AssignToReadonly (ec, right_side);
5435                                 }
5436                         }
5437
5438                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
5439                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
5440                                 ec.Report.Warning (197, 1, loc,
5441                                                 "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",
5442                                                 GetSignatureForError ());
5443                         }
5444
5445                         eclass = ExprClass.Variable;
5446                         return this;
5447                 }
5448
5449                 public override int GetHashCode ()
5450                 {
5451                         return spec.GetHashCode ();
5452                 }
5453
5454                 public bool IsFixed {
5455                         get {
5456                                 //
5457                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
5458                                 //
5459                                 IVariableReference variable = InstanceExpression as IVariableReference;
5460                                 if (variable != null)
5461                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
5462
5463                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5464                                 return fe != null && fe.IsFixed;
5465                         }
5466                 }
5467
5468                 public override bool Equals (object obj)
5469                 {
5470                         FieldExpr fe = obj as FieldExpr;
5471                         if (fe == null)
5472                                 return false;
5473
5474                         if (spec != fe.spec)
5475                                 return false;
5476
5477                         if (InstanceExpression == null || fe.InstanceExpression == null)
5478                                 return true;
5479
5480                         return InstanceExpression.Equals (fe.InstanceExpression);
5481                 }
5482
5483                 public void Emit (EmitContext ec, bool leave_copy)
5484                 {
5485                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
5486
5487                         spec.MemberDefinition.SetIsUsed ();
5488
5489                         if (IsStatic){
5490                                 if (is_volatile)
5491                                         ec.Emit (OpCodes.Volatile);
5492
5493                                 ec.Emit (OpCodes.Ldsfld, spec);
5494                         } else {
5495                                 if (!prepared)
5496                                         EmitInstance (ec, false);
5497
5498                                 // Optimization for build-in types
5499                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
5500                                         ec.EmitLoadFromPtr (type);
5501                                 } else {
5502                                         var ff = spec as FixedFieldSpec;
5503                                         if (ff != null) {
5504                                                 ec.Emit (OpCodes.Ldflda, spec);
5505                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
5506                                         } else {
5507                                                 if (is_volatile)
5508                                                         ec.Emit (OpCodes.Volatile);
5509
5510                                                 ec.Emit (OpCodes.Ldfld, spec);
5511                                         }
5512                                 }
5513                         }
5514
5515                         if (leave_copy) {
5516                                 ec.Emit (OpCodes.Dup);
5517                                 if (!IsStatic) {
5518                                         temp = new LocalTemporary (this.Type);
5519                                         temp.Store (ec);
5520                                 }
5521                         }
5522                 }
5523
5524                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
5525                 {
5526                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
5527                         if (isCompound && !(source is DynamicExpressionStatement)) {
5528                                 if (has_await_source) {
5529                                         if (IsInstance)
5530                                                 InstanceExpression = InstanceExpression.EmitToField (ec);
5531                                 } else {
5532                                         prepared = true;
5533                                 }
5534                         }
5535
5536                         if (IsInstance) {
5537                                 if (has_await_source)
5538                                         source = source.EmitToField (ec);
5539
5540                                 EmitInstance (ec, prepared);
5541                         }
5542
5543                         source.Emit (ec);
5544
5545                         if (leave_copy) {
5546                                 ec.Emit (OpCodes.Dup);
5547                                 if (!IsStatic) {
5548                                         temp = new LocalTemporary (this.Type);
5549                                         temp.Store (ec);
5550                                 }
5551                         }
5552
5553                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
5554                                 ec.Emit (OpCodes.Volatile);
5555
5556                         spec.MemberDefinition.SetIsAssigned ();
5557
5558                         if (IsStatic)
5559                                 ec.Emit (OpCodes.Stsfld, spec);
5560                         else
5561                                 ec.Emit (OpCodes.Stfld, spec);
5562
5563                         if (temp != null) {
5564                                 temp.Emit (ec);
5565                                 temp.Release (ec);
5566                                 temp = null;
5567                         }
5568                 }
5569
5570                 //
5571                 // Emits store to field with prepared values on stack
5572                 //
5573                 public void EmitAssignFromStack (EmitContext ec)
5574                 {
5575                         if (IsStatic) {
5576                                 ec.Emit (OpCodes.Stsfld, spec);
5577                         } else {
5578                                 ec.Emit (OpCodes.Stfld, spec);
5579                         }
5580                 }
5581
5582                 public override void Emit (EmitContext ec)
5583                 {
5584                         Emit (ec, false);
5585                 }
5586
5587                 public override void EmitSideEffect (EmitContext ec)
5588                 {
5589                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
5590
5591                         if (is_volatile) // || is_marshal_by_ref ())
5592                                 base.EmitSideEffect (ec);
5593                 }
5594
5595                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
5596                 {
5597                         if ((mode & AddressOp.Store) != 0)
5598                                 spec.MemberDefinition.SetIsAssigned ();
5599                         if ((mode & AddressOp.Load) != 0)
5600                                 spec.MemberDefinition.SetIsUsed ();
5601
5602                         //
5603                         // Handle initonly fields specially: make a copy and then
5604                         // get the address of the copy.
5605                         //
5606                         bool need_copy;
5607                         if (spec.IsReadOnly){
5608                                 need_copy = true;
5609                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
5610                                         if (IsStatic){
5611                                                 if (ec.IsStatic)
5612                                                         need_copy = false;
5613                                         } else
5614                                                 need_copy = false;
5615                                 }
5616                         } else
5617                                 need_copy = false;
5618
5619                         if (need_copy) {
5620                                 Emit (ec);
5621                                 var temp = ec.GetTemporaryLocal (type);
5622                                 ec.Emit (OpCodes.Stloc, temp);
5623                                 ec.Emit (OpCodes.Ldloca, temp);
5624                                 ec.FreeTemporaryLocal (temp, type);
5625                                 return;
5626                         }
5627
5628
5629                         if (IsStatic){
5630                                 ec.Emit (OpCodes.Ldsflda, spec);
5631                         } else {
5632                                 if (!prepared)
5633                                         EmitInstance (ec, false);
5634                                 ec.Emit (OpCodes.Ldflda, spec);
5635                         }
5636                 }
5637
5638                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
5639                 {
5640                         return MakeExpression (ctx);
5641                 }
5642
5643                 public override SLE.Expression MakeExpression (BuilderContext ctx)
5644                 {
5645 #if STATIC
5646                         return base.MakeExpression (ctx);
5647 #else
5648                         return SLE.Expression.Field (
5649                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
5650                                 spec.GetMetaInfo ());
5651 #endif
5652                 }
5653
5654                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5655                 {
5656                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
5657                 }
5658         }
5659
5660
5661         //
5662         // Expression that evaluates to a Property.
5663         //
5664         // This is not an LValue because we need to re-write the expression. We
5665         // can not take data from the stack and store it.
5666         //
5667         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
5668         {
5669                 public PropertyExpr (PropertySpec spec, Location l)
5670                         : base (l)
5671                 {
5672                         best_candidate = spec;
5673                         type = spec.MemberType;
5674                 }
5675
5676                 #region Properties
5677
5678                 protected override Arguments Arguments {
5679                         get {
5680                                 return null;
5681                         }
5682                         set {
5683                         }
5684                 }
5685
5686                 protected override TypeSpec DeclaringType {
5687                         get {
5688                                 return best_candidate.DeclaringType;
5689                         }
5690                 }
5691
5692                 public override string Name {
5693                         get {
5694                                 return best_candidate.Name;
5695                         }
5696                 }
5697
5698                 public override bool IsInstance {
5699                         get {
5700                                 return !IsStatic;
5701                         }
5702                 }
5703
5704                 public override bool IsStatic {
5705                         get {
5706                                 return best_candidate.IsStatic;
5707                         }
5708                 }
5709
5710                 public override string KindName {
5711                         get { return "property"; }
5712                 }
5713
5714                 public PropertySpec PropertyInfo {
5715                         get {
5716                                 return best_candidate;
5717                         }
5718                 }
5719
5720                 #endregion
5721
5722                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
5723                 {
5724                         return new PropertyExpr (spec, loc) {
5725                                 Getter = spec.Get,
5726                                 Setter = spec.Set
5727                         };
5728                 }
5729
5730                 public override Expression CreateExpressionTree (ResolveContext ec)
5731                 {
5732                         Arguments args;
5733                         if (IsSingleDimensionalArrayLength ()) {
5734                                 args = new Arguments (1);
5735                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
5736                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
5737                         }
5738
5739                         args = new Arguments (2);
5740                         if (InstanceExpression == null)
5741                                 args.Add (new Argument (new NullLiteral (loc)));
5742                         else
5743                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
5744                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
5745                         return CreateExpressionFactoryCall (ec, "Property", args);
5746                 }
5747
5748                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
5749                 {
5750                         DoResolveLValue (rc, null);
5751                         return new TypeOfMethod (Setter, loc);
5752                 }
5753
5754                 public override string GetSignatureForError ()
5755                 {
5756                         return best_candidate.GetSignatureForError ();
5757                 }
5758
5759                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
5760                 {
5761 #if STATIC
5762                         return base.MakeExpression (ctx);
5763 #else
5764                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
5765 #endif
5766                 }
5767
5768                 public override SLE.Expression MakeExpression (BuilderContext ctx)
5769                 {
5770 #if STATIC
5771                         return base.MakeExpression (ctx);
5772 #else
5773                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
5774 #endif
5775                 }
5776
5777                 void Error_PropertyNotValid (ResolveContext ec)
5778                 {
5779                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
5780                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
5781                                 GetSignatureForError ());
5782                 }
5783
5784                 bool IsSingleDimensionalArrayLength ()
5785                 {
5786                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
5787                                 return false;
5788
5789                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
5790                         return ac != null && ac.Rank == 1;
5791                 }
5792
5793                 public override void Emit (EmitContext ec, bool leave_copy)
5794                 {
5795                         //
5796                         // Special case: length of single dimension array property is turned into ldlen
5797                         //
5798                         if (IsSingleDimensionalArrayLength ()) {
5799                                 EmitInstance (ec, false);
5800                                 ec.Emit (OpCodes.Ldlen);
5801                                 ec.Emit (OpCodes.Conv_I4);
5802                                 return;
5803                         }
5804
5805                         base.Emit (ec, leave_copy);
5806                 }
5807
5808                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
5809                 {
5810                         Arguments args;
5811                         LocalTemporary await_source_arg = null;
5812
5813                         if (isCompound && !(source is DynamicExpressionStatement)) {
5814                                 emitting_compound_assignment = true;
5815                                 source.Emit (ec);
5816
5817                                 if (has_await_arguments) {
5818                                         await_source_arg = new LocalTemporary (Type);
5819                                         await_source_arg.Store (ec);
5820
5821                                         args = new Arguments (1);
5822                                         args.Add (new Argument (await_source_arg));
5823
5824                                         if (leave_copy) {
5825                                                 temp = await_source_arg;
5826                                         }
5827
5828                                         has_await_arguments = false;
5829                                 } else {
5830                                         args = null;
5831
5832                                         if (leave_copy) {
5833                                                 ec.Emit (OpCodes.Dup);
5834                                                 temp = new LocalTemporary (this.Type);
5835                                                 temp.Store (ec);
5836                                         }
5837                                 }
5838                         } else {
5839                                 args = new Arguments (1);
5840
5841                                 if (leave_copy) {
5842                                         source.Emit (ec);
5843                                         temp = new LocalTemporary (this.Type);
5844                                         temp.Store (ec);
5845                                         args.Add (new Argument (temp));
5846                                 } else {
5847                                         args.Add (new Argument (source));
5848                                 }
5849                         }
5850
5851                         emitting_compound_assignment = false;
5852
5853                         var call = new CallEmitter ();
5854                         call.InstanceExpression = InstanceExpression;
5855                         if (args == null)
5856                                 call.InstanceExpressionOnStack = true;
5857
5858                         call.Emit (ec, Setter, args, loc);
5859
5860                         if (temp != null) {
5861                                 temp.Emit (ec);
5862                                 temp.Release (ec);
5863                         }
5864
5865                         if (await_source_arg != null) {
5866                                 await_source_arg.Release (ec);
5867                         }
5868                 }
5869
5870                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
5871                 {
5872                         eclass = ExprClass.PropertyAccess;
5873
5874                         if (best_candidate.IsNotCSharpCompatible) {
5875                                 Error_PropertyNotValid (rc);
5876                         }
5877
5878                         ResolveInstanceExpression (rc, right_side);
5879
5880                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
5881                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
5882                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
5883                                 if (p != null) {
5884                                         type = p.MemberType;
5885                                 }
5886                         }
5887
5888                         DoBestMemberChecks (rc, best_candidate);
5889                         return this;
5890                 }
5891
5892                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5893                 {
5894                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
5895                 }
5896         }
5897
5898         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
5899         {
5900                 // getter and setter can be different for base calls
5901                 MethodSpec getter, setter;
5902                 protected T best_candidate;
5903
5904                 protected LocalTemporary temp;
5905                 protected bool emitting_compound_assignment;
5906                 protected bool has_await_arguments;
5907
5908                 protected PropertyOrIndexerExpr (Location l)
5909                 {
5910                         loc = l;
5911                 }
5912
5913                 #region Properties
5914
5915                 protected abstract Arguments Arguments { get; set; }
5916
5917                 public MethodSpec Getter {
5918                         get {
5919                                 return getter;
5920                         }
5921                         set {
5922                                 getter = value;
5923                         }
5924                 }
5925
5926                 public MethodSpec Setter {
5927                         get {
5928                                 return setter;
5929                         }
5930                         set {
5931                                 setter = value;
5932                         }
5933                 }
5934
5935                 #endregion
5936
5937                 protected override Expression DoResolve (ResolveContext ec)
5938                 {
5939                         if (eclass == ExprClass.Unresolved) {
5940                                 var expr = OverloadResolve (ec, null);
5941                                 if (expr == null)
5942                                         return null;
5943
5944                                 if (expr != this)
5945                                         return expr.Resolve (ec);
5946                         }
5947
5948                         if (!ResolveGetter (ec))
5949                                 return null;
5950
5951                         return this;
5952                 }
5953
5954                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5955                 {
5956                         if (right_side == EmptyExpression.OutAccess) {
5957                                 // TODO: best_candidate can be null at this point
5958                                 INamedBlockVariable variable = null;
5959                                 if (best_candidate != null && ec.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, ec.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
5960                                         ec.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
5961                                                 best_candidate.Name);
5962                                 } else {
5963                                         right_side.DoResolveLValue (ec, this);
5964                                 }
5965                                 return null;
5966                         }
5967
5968                         // if the property/indexer returns a value type, and we try to set a field in it
5969                         if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess) {
5970                                 Error_ValueAssignment (ec, right_side);
5971                         }
5972
5973                         if (eclass == ExprClass.Unresolved) {
5974                                 var expr = OverloadResolve (ec, right_side);
5975                                 if (expr == null)
5976                                         return null;
5977
5978                                 if (expr != this)
5979                                         return expr.ResolveLValue (ec, right_side);
5980                         }
5981
5982                         if (!ResolveSetter (ec))
5983                                 return null;
5984
5985                         return this;
5986                 }
5987
5988                 //
5989                 // Implements the IAssignMethod interface for assignments
5990                 //
5991                 public virtual void Emit (EmitContext ec, bool leave_copy)
5992                 {
5993                         var call = new CallEmitter ();
5994                         call.InstanceExpression = InstanceExpression;
5995                         if (has_await_arguments)
5996                                 call.HasAwaitArguments = true;
5997                         else
5998                                 call.DuplicateArguments = emitting_compound_assignment;
5999
6000                         call.Emit (ec, Getter, Arguments, loc);
6001
6002                         if (call.HasAwaitArguments) {
6003                                 InstanceExpression = call.InstanceExpression;
6004                                 Arguments = call.EmittedArguments;
6005                                 has_await_arguments = true;
6006                         }
6007
6008                         if (leave_copy) {
6009                                 ec.Emit (OpCodes.Dup);
6010                                 temp = new LocalTemporary (Type);
6011                                 temp.Store (ec);
6012                         }
6013                 }
6014
6015                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
6016
6017                 public override void Emit (EmitContext ec)
6018                 {
6019                         Emit (ec, false);
6020                 }
6021
6022                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
6023                 {
6024                         has_await_arguments = true;
6025                         Emit (ec, false);
6026                         return null;
6027                 }
6028
6029                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
6030
6031                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
6032
6033                 bool ResolveGetter (ResolveContext rc)
6034                 {
6035                         if (!best_candidate.HasGet) {
6036                                 if (InstanceExpression != EmptyExpression.Null) {
6037                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
6038                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
6039                                                 best_candidate.GetSignatureForError ());
6040                                         return false;
6041                                 }
6042                         } else if (!best_candidate.Get.IsAccessible (rc)) {
6043                                 if (best_candidate.HasDifferentAccessibility) {
6044                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6045                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
6046                                                 TypeManager.CSharpSignature (best_candidate));
6047                                 } else {
6048                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6049                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
6050                                 }
6051                         }
6052
6053                         if (best_candidate.HasDifferentAccessibility) {
6054                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
6055                         }
6056
6057                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
6058                         return true;
6059                 }
6060
6061                 bool ResolveSetter (ResolveContext rc)
6062                 {
6063                         if (!best_candidate.HasSet) {
6064                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
6065                                         GetSignatureForError ());
6066                                 return false;
6067                         }
6068
6069                         if (!best_candidate.Set.IsAccessible (rc)) {
6070                                 if (best_candidate.HasDifferentAccessibility) {
6071                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6072                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
6073                                                 GetSignatureForError ());
6074                                 } else {
6075                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6076                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
6077                                 }
6078                         }
6079
6080                         if (best_candidate.HasDifferentAccessibility)
6081                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
6082
6083                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
6084                         return true;
6085                 }
6086         }
6087
6088         /// <summary>
6089         ///   Fully resolved expression that evaluates to an Event
6090         /// </summary>
6091         public class EventExpr : MemberExpr, IAssignMethod
6092         {
6093                 readonly EventSpec spec;
6094                 MethodSpec op;
6095
6096                 public EventExpr (EventSpec spec, Location loc)
6097                 {
6098                         this.spec = spec;
6099                         this.loc = loc;
6100                 }
6101
6102                 #region Properties
6103
6104                 protected override TypeSpec DeclaringType {
6105                         get {
6106                                 return spec.DeclaringType;
6107                         }
6108                 }
6109
6110                 public override string Name {
6111                         get {
6112                                 return spec.Name;
6113                         }
6114                 }
6115
6116                 public override bool IsInstance {
6117                         get {
6118                                 return !spec.IsStatic;
6119                         }
6120                 }
6121
6122                 public override bool IsStatic {
6123                         get {
6124                                 return spec.IsStatic;
6125                         }
6126                 }
6127
6128                 public override string KindName {
6129                         get { return "event"; }
6130                 }
6131
6132                 public MethodSpec Operator {
6133                         get {
6134                                 return op;
6135                         }
6136                 }
6137
6138                 #endregion
6139
6140                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
6141                 {
6142                         //
6143                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
6144                         //
6145                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6146                                 if (spec.BackingField != null &&
6147                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
6148
6149                                         spec.MemberDefinition.SetIsUsed ();
6150
6151                                         if (!ec.IsObsolete) {
6152                                                 ObsoleteAttribute oa = spec.GetAttributeObsolete ();
6153                                                 if (oa != null)
6154                                                         AttributeTester.Report_ObsoleteMessage (oa, spec.GetSignatureForError (), loc, ec.Report);
6155                                         }
6156
6157                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
6158                                                 Error_AssignmentEventOnly (ec);
6159
6160                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
6161
6162                                         InstanceExpression = null;
6163
6164                                         return ml.ResolveMemberAccess (ec, left, original);
6165                                 }
6166                         }
6167
6168                         return base.ResolveMemberAccess (ec, left, original);
6169                 }
6170
6171                 public override Expression CreateExpressionTree (ResolveContext ec)
6172                 {
6173                         throw new NotSupportedException ("ET");
6174                 }
6175
6176                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6177                 {
6178                         if (right_side == EmptyExpression.EventAddition) {
6179                                 op = spec.AccessorAdd;
6180                         } else if (right_side == EmptyExpression.EventSubtraction) {
6181                                 op = spec.AccessorRemove;
6182                         }
6183
6184                         if (op == null) {
6185                                 Error_AssignmentEventOnly (ec);
6186                                 return null;
6187                         }
6188
6189                         op = CandidateToBaseOverride (ec, op);
6190                         return this;
6191                 }
6192
6193                 protected override Expression DoResolve (ResolveContext ec)
6194                 {
6195                         eclass = ExprClass.EventAccess;
6196                         type = spec.MemberType;
6197
6198                         ResolveInstanceExpression (ec, null);
6199
6200                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6201                                 Error_AssignmentEventOnly (ec);
6202                         }
6203
6204                         DoBestMemberChecks (ec, spec);
6205                         return this;
6206                 }
6207
6208                 public override void Emit (EmitContext ec)
6209                 {
6210                         throw new NotSupportedException ();
6211                         //Error_CannotAssign ();
6212                 }
6213
6214                 #region IAssignMethod Members
6215
6216                 public void Emit (EmitContext ec, bool leave_copy)
6217                 {
6218                         throw new NotImplementedException ();
6219                 }
6220
6221                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6222                 {
6223                         if (leave_copy || !isCompound)
6224                                 throw new NotImplementedException ("EventExpr::EmitAssign");
6225
6226                         Arguments args = new Arguments (1);
6227                         args.Add (new Argument (source));
6228
6229                         var call = new CallEmitter ();
6230                         call.InstanceExpression = InstanceExpression;
6231                         call.Emit (ec, op, args, loc);
6232                 }
6233
6234                 #endregion
6235
6236                 void Error_AssignmentEventOnly (ResolveContext ec)
6237                 {
6238                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
6239                                 ec.Report.Error (79, loc,
6240                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
6241                                         GetSignatureForError ());
6242                         } else {
6243                                 ec.Report.Error (70, loc,
6244                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
6245                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
6246                         }
6247                 }
6248
6249                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
6250                 {
6251                         name = name.Substring (0, name.LastIndexOf ('.'));
6252                         base.Error_CannotCallAbstractBase (rc, name);
6253                 }
6254
6255                 public override string GetSignatureForError ()
6256                 {
6257                         return TypeManager.CSharpSignature (spec);
6258                 }
6259
6260                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6261                 {
6262                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
6263                 }
6264         }
6265
6266         public class TemporaryVariableReference : VariableReference
6267         {
6268                 public class Declarator : Statement
6269                 {
6270                         TemporaryVariableReference variable;
6271
6272                         public Declarator (TemporaryVariableReference variable)
6273                         {
6274                                 this.variable = variable;
6275                                 loc = variable.loc;
6276                         }
6277
6278                         protected override void DoEmit (EmitContext ec)
6279                         {
6280                                 variable.li.CreateBuilder (ec);
6281                         }
6282
6283                         public override void Emit (EmitContext ec)
6284                         {
6285                                 // Don't create sequence point
6286                                 DoEmit (ec);
6287                         }
6288
6289                         protected override void CloneTo (CloneContext clonectx, Statement target)
6290                         {
6291                                 // Nothing
6292                         }
6293                 }
6294
6295                 LocalVariable li;
6296
6297                 public TemporaryVariableReference (LocalVariable li, Location loc)
6298                 {
6299                         this.li = li;
6300                         this.type = li.Type;
6301                         this.loc = loc;
6302                 }
6303
6304                 public override bool IsLockedByStatement {
6305                         get {
6306                                 return false;
6307                         }
6308                         set {
6309                         }
6310                 }
6311
6312                 public LocalVariable LocalInfo {
6313                     get {
6314                         return li;
6315                     }
6316                 }
6317
6318                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc)
6319                 {
6320                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc);
6321                         return new TemporaryVariableReference (li, loc);
6322                 }
6323
6324                 protected override Expression DoResolve (ResolveContext ec)
6325                 {
6326                         eclass = ExprClass.Variable;
6327
6328                         //
6329                         // Don't capture temporary variables except when using
6330                         // state machine redirection and block yields
6331                         //
6332                         if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.IsIterator &&
6333                                 ec.CurrentBlock.Explicit.HasYield && ec.IsVariableCapturingRequired) {
6334                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
6335                                 storey.CaptureLocalVariable (ec, li);
6336                         }
6337
6338                         return this;
6339                 }
6340
6341                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6342                 {
6343                         return Resolve (ec);
6344                 }
6345
6346                 public override void Emit (EmitContext ec)
6347                 {
6348                         li.CreateBuilder (ec);
6349
6350                         Emit (ec, false);
6351                 }
6352
6353                 public void EmitAssign (EmitContext ec, Expression source)
6354                 {
6355                         li.CreateBuilder (ec);
6356
6357                         EmitAssign (ec, source, false, false);
6358                 }
6359
6360                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
6361                 {
6362                         return li.HoistedVariant;
6363                 }
6364
6365                 public override bool IsFixed {
6366                         get { return true; }
6367                 }
6368
6369                 public override bool IsRef {
6370                         get { return false; }
6371                 }
6372
6373                 public override string Name {
6374                         get { throw new NotImplementedException (); }
6375                 }
6376
6377                 public override void SetHasAddressTaken ()
6378                 {
6379                         throw new NotImplementedException ();
6380                 }
6381
6382                 protected override ILocalVariable Variable {
6383                         get { return li; }
6384                 }
6385
6386                 public override VariableInfo VariableInfo {
6387                         get { return null; }
6388                 }
6389
6390                 public override void VerifyAssigned (ResolveContext rc)
6391                 {
6392                 }
6393         }
6394
6395         ///
6396         /// Handles `var' contextual keyword; var becomes a keyword only
6397         /// if no type called var exists in a variable scope
6398         ///
6399         class VarExpr : SimpleName
6400         {
6401                 public VarExpr (Location loc)
6402                         : base ("var", loc)
6403                 {
6404                 }
6405
6406                 public bool InferType (ResolveContext ec, Expression right_side)
6407                 {
6408                         if (type != null)
6409                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
6410
6411                         type = right_side.Type;
6412                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
6413                                 ec.Report.Error (815, loc,
6414                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
6415                                         type.GetSignatureForError ());
6416                                 return false;
6417                         }
6418
6419                         eclass = ExprClass.Variable;
6420                         return true;
6421                 }
6422
6423                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
6424                 {
6425                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
6426                                 base.Error_TypeOrNamespaceNotFound (ec);
6427                         else
6428                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
6429                 }
6430         }
6431 }