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         /// <remarks>
 122         ///   Base class for expressions
 123         /// </remarks>
 124         public abstract class Expression {
 125                 public ExprClass eclass;
 126                 protected TypeSpec type;
 127                 protected Location loc;
 128
 129                 public TypeSpec Type {
 130                         get { return type; }
 131                         set { type = value; }
 132                 }
 133
 134                 public virtual bool IsSideEffectFree {
 135                         get {
 136                                 return false;
 137                         }
 138                 }
 139
 140                 public Location Location {
 141                         get { return loc; }
 142                 }
 143
 144                 public virtual bool IsNull {
 145                         get {
 146                                 return false;
 147                         }
 148                 }
 149
 150                 //
 151                 // Returns true when the expression during Emit phase breaks stack
 152                 // by using await expression
 153                 //
 154                 public virtual bool ContainsEmitWithAwait ()
 155                 {
 156                         return false;
 157                 }
 158
 159                 /// <summary>
 160                 ///   Performs semantic analysis on the Expression
 161                 /// </summary>
 162                 ///
 163                 /// <remarks>
 164                 ///   The Resolve method is invoked to perform the semantic analysis
 165                 ///   on the node.
 166                 ///
 167                 ///   The return value is an expression (it can be the
 168                 ///   same expression in some cases) or a new
 169                 ///   expression that better represents this node.
 170                 ///
 171                 ///   For example, optimizations of Unary (LiteralInt)
 172                 ///   would return a new LiteralInt with a negated
 173                 ///   value.
 174                 ///
 175                 ///   If there is an error during semantic analysis,
 176                 ///   then an error should be reported (using Report)
 177                 ///   and a null value should be returned.
 178                 ///
 179                 ///   There are two side effects expected from calling
 180                 ///   Resolve(): the the field variable "eclass" should
 181                 ///   be set to any value of the enumeration
 182                 ///   `ExprClass' and the type variable should be set
 183                 ///   to a valid type (this is the type of the
 184                 ///   expression).
 185                 /// </remarks>
 186                 protected abstract Expression DoResolve (ResolveContext rc);
 187
 188                 public virtual Expression DoResolveLValue (ResolveContext rc, Expression right_side)
 189                 {
 190                         return null;
 191                 }
 192
 193                 //
 194                 // This is used if the expression should be resolved as a type or namespace name.
 195                 // the default implementation fails.
 196                 //
 197                 public virtual TypeSpec ResolveAsType (IMemberContext mc)
 198                 {
 199                         ResolveContext ec = new ResolveContext (mc);
 200                         Expression e = Resolve (ec);
 201                         if (e != null)
 202                                 e.Error_UnexpectedKind (ec, ResolveFlags.Type, loc);
 203
 204                         return null;
 205                 }
 206
 207                 public static void ErrorIsInaccesible (IMemberContext rc, string member, Location loc)
 208                 {
 209                         rc.Module.Compiler.Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", member);
 210                 }
 211
 212                 public void Error_ExpressionMustBeConstant (ResolveContext rc, Location loc, string e_name)
 213                 {
 214                         rc.Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
 215                 }
 216
 217                 public void Error_ConstantCanBeInitializedWithNullOnly (ResolveContext rc, TypeSpec type, Location loc, string name)
 218                 {
 219                         rc.Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
 220                                 name, TypeManager.CSharpName (type));
 221                 }
 222
 223                 public static void Error_InvalidExpressionStatement (Report Report, Location loc)
 224                 {
 225                         Report.Error (201, loc, "Only assignment, call, increment, decrement, and new object " +
 226                                        "expressions can be used as a statement");
 227                 }
 228
 229                 public void Error_InvalidExpressionStatement (BlockContext ec)
 230                 {
 231                         Error_InvalidExpressionStatement (ec.Report, loc);
 232                 }
 233
 234                 public static void Error_VoidInvalidInTheContext (Location loc, Report Report)
 235                 {
 236                         Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
 237                 }
 238
 239                 public virtual void Error_ValueCannotBeConverted (ResolveContext ec, Location loc, TypeSpec target, bool expl)
 240                 {
 241                         Error_ValueCannotBeConvertedCore (ec, loc, target, expl);
 242                 }
 243
 244                 protected void Error_ValueCannotBeConvertedCore (ResolveContext ec, Location loc, TypeSpec target, bool expl)
 245                 {
 246                         // The error was already reported as CS1660
 247                         if (type == InternalType.AnonymousMethod)
 248                                 return;
 249
 250                         string from_type = type.GetSignatureForError ();
 251                         string to_type = target.GetSignatureForError ();
 252                         if (from_type == to_type) {
 253                                 from_type = type.GetSignatureForErrorIncludingAssemblyName ();
 254                                 to_type = target.GetSignatureForErrorIncludingAssemblyName ();
 255                         }
 256
 257                         if (expl) {
 258                                 ec.Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
 259                                         from_type, to_type);
 260                                 return;
 261                         }
 262
 263                         ec.Report.DisableReporting ();
 264                         bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
 265                         ec.Report.EnableReporting ();
 266
 267                         if (expl_exists) {
 268                                 ec.Report.Error (266, loc,
 269                                         "Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
 270                                         from_type, to_type);
 271                         } else {
 272                                 ec.Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
 273                                         from_type, to_type);
 274                         }
 275                 }
 276
 277                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, MemberSpec member, int arity, Location loc)
 278                 {
 279                         // Better message for possible generic expressions
 280                         if (member != null && (member.Kind & MemberKind.GenericMask) != 0) {
 281                                 var report = context.Module.Compiler.Report;
 282                                 report.SymbolRelatedToPreviousError (member);
 283                                 if (member is TypeSpec)
 284                                         member = ((TypeSpec) member).GetDefinition ();
 285                                 else
 286                                         member = ((MethodSpec) member).GetGenericMethodDefinition ();
 287
 288                                 string name = member.Kind == MemberKind.Method ? "method" : "type";
 289                                 if (member.IsGeneric) {
 290                                         report.Error (305, loc, "Using the generic {0} `{1}' requires `{2}' type argument(s)",
 291                                                 name, member.GetSignatureForError (), member.Arity.ToString ());
 292                                 } else {
 293                                         report.Error (308, loc, "The non-generic {0} `{1}' cannot be used with the type arguments",
 294                                                 name, member.GetSignatureForError ());
 295                                 }
 296                         } else {
 297                                 Error_TypeArgumentsCannotBeUsed (context, ExprClassName, GetSignatureForError (), loc);
 298                         }
 299                 }
 300
 301                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, string exprType, string name, Location loc)
 302                 {
 303                         context.Module.Compiler.Report.Error (307, loc, "The {0} `{1}' cannot be used with type arguments",
 304                                 exprType, name);
 305                 }
 306
 307                 protected virtual void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
 308                 {
 309                         Error_TypeDoesNotContainDefinition (ec, loc, type, name);
 310                 }
 311
 312                 public static void Error_TypeDoesNotContainDefinition (ResolveContext ec, Location loc, TypeSpec type, string name)
 313                 {
 314                         ec.Report.SymbolRelatedToPreviousError (type);
 315                         ec.Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
 316                                 TypeManager.CSharpName (type), name);
 317                 }
 318
 319                 public void Error_ValueAssignment (ResolveContext rc, Expression rhs)
 320                 {
 321                         if (rhs == EmptyExpression.LValueMemberAccess || rhs == EmptyExpression.LValueMemberOutAccess) {
 322                                 rc.Report.SymbolRelatedToPreviousError (type);
 323                                 if (rc.CurrentInitializerVariable != null) {
 324                                         rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
 325                                                 type.GetSignatureForError (), GetSignatureForError ());
 326                                 } else {
 327                                         rc.Report.Error (1612, loc, "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
 328                                                 GetSignatureForError ());
 329                                 }
 330                         } else {
 331                                 rc.Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
 332                         }
 333                 }
 334
 335                 protected void Error_VoidPointerOperation (ResolveContext rc)
 336                 {
 337                         rc.Report.Error (242, loc, "The operation in question is undefined on void pointers");
 338                 }
 339
 340                 public ResolveFlags ExprClassToResolveFlags {
 341                         get {
 342                                 switch (eclass) {
 343                                 case ExprClass.Type:
 344                                 case ExprClass.Namespace:
 345                                         return ResolveFlags.Type;
 346
 347                                 case ExprClass.MethodGroup:
 348                                         return ResolveFlags.MethodGroup;
 349
 350                                 case ExprClass.TypeParameter:
 351                                         return ResolveFlags.TypeParameter;
 352
 353                                 case ExprClass.Value:
 354                                 case ExprClass.Variable:
 355                                 case ExprClass.PropertyAccess:
 356                                 case ExprClass.EventAccess:
 357                                 case ExprClass.IndexerAccess:
 358                                         return ResolveFlags.VariableOrValue;
 359
 360                                 default:
 361                                         throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
 362                                 }
 363                         }
 364                 }
 365
 366                 public virtual string GetSignatureForError ()
 367                 {
 368                         return type.GetDefinition ().GetSignatureForError ();
 369                 }
 370
 371                 /// <summary>
 372                 ///   Resolves an expression and performs semantic analysis on it.
 373                 /// </summary>
 374                 ///
 375                 /// <remarks>
 376                 ///   Currently Resolve wraps DoResolve to perform sanity
 377                 ///   checking and assertion checking on what we expect from Resolve.
 378                 /// </remarks>
 379                 public Expression Resolve (ResolveContext ec, ResolveFlags flags)
 380                 {
 381                         if (eclass != ExprClass.Unresolved)
 382                                 return this;
 383
 384                         Expression e;
 385                         try {
 386                                 e = DoResolve (ec);
 387
 388                                 if (e == null)
 389                                         return null;
 390
 391                                 if ((flags & e.ExprClassToResolveFlags) == 0) {
 392                                         e.Error_UnexpectedKind (ec, flags, loc);
 393                                         return null;
 394                                 }
 395
 396                                 if (e.type == null)
 397                                         throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());
 398
 399                                 return e;
 400                         } catch (Exception ex) {
 401                                 if (loc.IsNull || ec.Module.Compiler.Settings.DebugFlags > 0 || ex is CompletionResult || ec.Report.IsDisabled)
 402                                         throw;
 403
 404                                 ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
 405                                 return ErrorExpression.Instance;        // TODO: Add location
 406                         }
 407                 }
 408
 409                 /// <summary>
 410                 ///   Resolves an expression and performs semantic analysis on it.
 411                 /// </summary>
 412                 public Expression Resolve (ResolveContext rc)
 413                 {
 414                         return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
 415                 }
 416
 417                 /// <summary>
 418                 ///   Resolves an expression for LValue assignment
 419                 /// </summary>
 420                 ///
 421                 /// <remarks>
 422                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 423                 ///   checking and assertion checking on what we expect from Resolve
 424                 /// </remarks>
 425                 public Expression ResolveLValue (ResolveContext ec, Expression right_side)
 426                 {
 427                         int errors = ec.Report.Errors;
 428                         bool out_access = right_side == EmptyExpression.OutAccess;
 429
 430                         Expression e = DoResolveLValue (ec, right_side);
 431
 432                         if (e != null && out_access && !(e is IMemoryLocation)) {
 433                                 // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
 434                                 //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,
 435
 436                                 //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
 437                                 //                                e.GetType () + " " + e.GetSignatureForError ());
 438                                 e = null;
 439                         }
 440
 441                         if (e == null) {
 442                                 if (errors == ec.Report.Errors) {
 443                                         if (out_access)
 444                                                 ec.Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
 445                                         else
 446                                                 Error_ValueAssignment (ec, right_side);
 447                                 }
 448                                 return null;
 449                         }
 450
 451                         if (e.eclass == ExprClass.Unresolved)
 452                                 throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");
 453
 454                         if ((e.type == null) && !(e is GenericTypeExpr))
 455                                 throw new Exception ("Expression " + e + " did not set its type after Resolve");
 456
 457                         return e;
 458                 }
 459
 460                 public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
 461                 {
 462                         rc.Module.Compiler.Report.Error (182, loc,
 463                                 "An attribute argument must be a constant expression, typeof expression or array creation expression");
 464                 }
 465
 466                 /// <summary>
 467                 ///   Emits the code for the expression
 468                 /// </summary>
 469                 ///
 470                 /// <remarks>
 471                 ///   The Emit method is invoked to generate the code
 472                 ///   for the expression.
 473                 /// </remarks>
 474                 public abstract void Emit (EmitContext ec);
 475
 476
 477                 // Emit code to branch to @target if this expression is equivalent to @on_true.
 478                 // The default implementation is to emit the value, and then emit a brtrue or brfalse.
 479                 // Subclasses can provide more efficient implementations, but those MUST be equivalent,
 480                 // including the use of conditional branches.  Note also that a branch MUST be emitted
 481                 public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
 482                 {
 483                         Emit (ec);
 484                         ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
 485                 }
 486
 487                 // Emit this expression for its side effects, not for its value.
 488                 // The default implementation is to emit the value, and then throw it away.
 489                 // Subclasses can provide more efficient implementations, but those MUST be equivalent
 490                 public virtual void EmitSideEffect (EmitContext ec)
 491                 {
 492                         Emit (ec);
 493                         ec.Emit (OpCodes.Pop);
 494                 }
 495
 496                 //
 497                 // Emits the expression into temporary field variable. The method
 498                 // should be used for await expressions only
 499                 //
 500                 public virtual Expression EmitToField (EmitContext ec)
 501                 {
 502                         //
 503                         // This is the await prepare Emit method. When emitting code like
 504                         // a + b we emit code like
 505                         //
 506                         // a.Emit ()
 507                         // b.Emit ()
 508                         // Opcodes.Add
 509                         //
 510                         // For await a + await b we have to interfere the flow to keep the
 511                         // stack clean because await yields from the expression. The emit
 512                         // then changes to
 513                         //
 514                         // a = a.EmitToField () // a is changed to temporary field access
 515                         // b = b.EmitToField ()
 516                         // a.Emit ()
 517                         // b.Emit ()
 518                         // Opcodes.Add
 519                         //
 520                         //
 521                         // The idea is to emit expression and leave the stack empty with
 522                         // result value still available.
 523                         //
 524                         // Expressions should override this default implementation when
 525                         // optimized version can be provided (e.g. FieldExpr)
 526                         //
 527                         //
 528                         // We can optimize for side-effect free expressions, they can be
 529                         // emitted out of order
 530                         //
 531                         if (IsSideEffectFree)
 532                                 return this;
 533
 534                         bool needs_temporary = ContainsEmitWithAwait ();
 535                         if (!needs_temporary)
 536                                 ec.EmitThis ();
 537
 538                         // Emit original code
 539                         EmitToFieldSource (ec);
 540
 541                         //
 542                         // Store the result to temporary field when we
 543                         // cannot load `this' directly
 544                         //
 545                         var field = ec.GetTemporaryField (type);
 546                         if (needs_temporary) {
 547                                 //
 548                                 // Create temporary local (we cannot load `this' before Emit)
 549                                 //
 550                                 var temp = ec.GetTemporaryLocal (type);
 551                                 ec.Emit (OpCodes.Stloc, temp);
 552
 553                                 ec.EmitThis ();
 554                                 ec.Emit (OpCodes.Ldloc, temp);
 555                                 field.EmitAssignFromStack (ec);
 556
 557                                 ec.FreeTemporaryLocal (temp, type);
 558                         } else {
 559                                 field.EmitAssignFromStack (ec);
 560                         }
 561
 562                         return field;
 563                 }
 564
 565                 protected virtual void EmitToFieldSource (EmitContext ec)
 566                 {
 567                         //
 568                         // Default implementation calls Emit method
 569                         //
 570                         Emit (ec);
 571                 }
 572
 573                 protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
 574                 {
 575                         if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
 576                                 bool contains_await = false;
 577
 578                                 for (int i = 1; i < expressions.Count; ++i) {
 579                                         if (expressions[i].ContainsEmitWithAwait ()) {
 580                                                 contains_await = true;
 581                                                 break;
 582                                         }
 583                                 }
 584
 585                                 if (contains_await) {
 586                                         for (int i = 0; i < expressions.Count; ++i) {
 587                                                 expressions[i] = expressions[i].EmitToField (ec);
 588                                         }
 589                                 }
 590                         }
 591
 592                         for (int i = 0; i < expressions.Count; ++i) {
 593                                 expressions[i].Emit (ec);
 594                         }
 595                 }
 596
 597                 /// <summary>
 598                 ///   Protected constructor.  Only derivate types should
 599                 ///   be able to be created
 600                 /// </summary>
 601
 602                 protected Expression ()
 603                 {
 604                 }
 605
 606                 /// <summary>
 607                 ///   Returns a fully formed expression after a MemberLookup
 608                 /// </summary>
 609                 ///
 610                 static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
 611                 {
 612                         if (spec is EventSpec)
 613                                 return new EventExpr ((EventSpec) spec, loc);
 614                         if (spec is ConstSpec)
 615                                 return new ConstantExpr ((ConstSpec) spec, loc);
 616                         if (spec is FieldSpec)
 617                                 return new FieldExpr ((FieldSpec) spec, loc);
 618                         if (spec is PropertySpec)
 619                                 return new PropertyExpr ((PropertySpec) spec, loc);
 620                         if (spec is TypeSpec)
 621                                 return new TypeExpression (((TypeSpec) spec), loc);
 622
 623                         return null;
 624                 }
 625
 626                 public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
 627                 {
 628                         var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
 629                         if (ctors == null) {
 630                                 rc.Report.SymbolRelatedToPreviousError (type);
 631                                 if (type.IsStruct) {
 632                                         // Report meaningful error for struct as they always have default ctor in C# context
 633                                         OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
 634                                 } else {
 635                                         rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
 636                                                 type.GetSignatureForError ());
 637                                 }
 638
 639                                 return null;
 640                         }
 641
 642                         var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
 643                         if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
 644                                 r.InstanceQualifier = new ConstructorInstanceQualifier (type);
 645                         }
 646
 647                         return r.ResolveMember<MethodSpec> (rc, ref args);
 648                 }
 649
 650                 [Flags]
 651                 public enum MemberLookupRestrictions
 652                 {
 653                         None = 0,
 654                         InvocableOnly = 1,
 655                         ExactArity = 1 << 2,
 656                         ReadAccess = 1 << 3
 657                 }
 658
 659                 //
 660                 // Lookup type `queried_type' for code in class `container_type' with a qualifier of
 661                 // `qualifier_type' or null to lookup members in the current class.
 662                 //
 663                 public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 664                 {
 665                         var members = MemberCache.FindMembers (queried_type, name, false);
 666                         if (members == null)
 667                                 return null;
 668
 669                         MemberSpec non_method = null;
 670                         MemberSpec ambig_non_method = null;
 671                         do {
 672                                 for (int i = 0; i < members.Count; ++i) {
 673                                         var member = members[i];
 674
 675                                         // HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
 676                                         if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
 677                                                 continue;
 678
 679                                         if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0)
 680                                                 continue;
 681
 682                                         if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
 683                                                 continue;
 684
 685                                         if (!errorMode) {
 686                                                 if (!member.IsAccessible (rc))
 687                                                         continue;
 688
 689                                                 //
 690                                                 // With runtime binder we can have a situation where queried type is inaccessible
 691                                                 // because it came via dynamic object, the check about inconsisted accessibility
 692                                                 // had no effect as the type was unknown during compilation
 693                                                 //
 694                                                 // class A {
 695                                                 //              private class N { }
 696                                                 //
 697                                                 //              public dynamic Foo ()
 698                                                 //              {
 699                                                 //                      return new N ();
 700                                                 //              }
 701                                                 //      }
 702                                                 //
 703                                                 if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
 704                                                         continue;
 705                                         }
 706
 707                                         if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
 708                                                 if (member is MethodSpec)
 709                                                         return new MethodGroupExpr (members, queried_type, loc);
 710
 711                                                 if (!Invocation.IsMemberInvocable (member))
 712                                                         continue;
 713                                         }
 714
 715                                         if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
 716                                                 non_method = member;
 717                                         } else if (!errorMode && !member.IsNotCSharpCompatible) {
 718                                                 ambig_non_method = member;
 719                                         }
 720                                 }
 721
 722                                 if (non_method != null) {
 723                                         if (ambig_non_method != null && rc != null) {
 724                                                 var report = rc.Module.Compiler.Report;
 725                                                 report.SymbolRelatedToPreviousError (non_method);
 726                                                 report.SymbolRelatedToPreviousError (ambig_non_method);
 727                                                 report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
 728                                                         non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
 729                                         }
 730
 731                                         if (non_method is MethodSpec)
 732                                                 return new MethodGroupExpr (members, queried_type, loc);
 733
 734                                         return ExprClassFromMemberInfo (non_method, loc);
 735                                 }
 736
 737                                 if (members[0].DeclaringType.BaseType == null)
 738                                         members = null;
 739                                 else
 740                                         members = MemberCache.FindMembers (members[0].DeclaringType.BaseType, name, false);
 741
 742                         } while (members != null);
 743
 744                         return null;
 745                 }
 746
 747                 protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
 748                 {
 749                         throw new NotImplementedException ();
 750                 }
 751
 752                 public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
 753                 {
 754                         rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
 755                                 oper, t.GetSignatureForError ());
 756                 }
 757
 758                 protected void Error_PointerInsideExpressionTree (ResolveContext ec)
 759                 {
 760                         ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
 761                 }
 762
 763                 /// <summary>
 764                 ///   Returns an expression that can be used to invoke operator true
 765                 ///   on the expression if it exists.
 766                 /// </summary>
 767                 protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
 768                 {
 769                         return GetOperatorTrueOrFalse (ec, e, true, loc);
 770                 }
 771
 772                 /// <summary>
 773                 ///   Returns an expression that can be used to invoke operator false
 774                 ///   on the expression if it exists.
 775                 /// </summary>
 776                 protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
 777                 {
 778                         return GetOperatorTrueOrFalse (ec, e, false, loc);
 779                 }
 780
 781                 static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
 782                 {
 783                         var op = is_true ? Operator.OpType.True : Operator.OpType.False;
 784                         var methods = MemberCache.GetUserOperator (e.type, op, false);
 785                         if (methods == null)
 786                                 return null;
 787
 788                         Arguments arguments = new Arguments (1);
 789                         arguments.Add (new Argument (e));
 790
 791                         var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
 792                         var oper = res.ResolveOperator (ec, ref arguments);
 793
 794                         if (oper == null)
 795                                 return null;
 796
 797                         return new UserOperatorCall (oper, arguments, null, loc);
 798                 }
 799
 800                 public virtual string ExprClassName
 801                 {
 802                         get {
 803                                 switch (eclass){
 804                                 case ExprClass.Unresolved:
 805                                         return "Unresolved";
 806                                 case ExprClass.Value:
 807                                         return "value";
 808                                 case ExprClass.Variable:
 809                                         return "variable";
 810                                 case ExprClass.Namespace:
 811                                         return "namespace";
 812                                 case ExprClass.Type:
 813                                         return "type";
 814                                 case ExprClass.MethodGroup:
 815                                         return "method group";
 816                                 case ExprClass.PropertyAccess:
 817                                         return "property access";
 818                                 case ExprClass.EventAccess:
 819                                         return "event access";
 820                                 case ExprClass.IndexerAccess:
 821                                         return "indexer access";
 822                                 case ExprClass.Nothing:
 823                                         return "null";
 824                                 case ExprClass.TypeParameter:
 825                                         return "type parameter";
 826                                 }
 827                                 throw new Exception ("Should not happen");
 828                         }
 829                 }
 830
 831                 /// <summary>
 832                 ///   Reports that we were expecting `expr' to be of class `expected'
 833                 /// </summary>
 834                 public void Error_UnexpectedKind (Report r, MemberCore mc, string expected, Location loc)
 835                 {
 836                         Error_UnexpectedKind (r, mc, expected, ExprClassName, loc);
 837                 }
 838
 839                 public void Error_UnexpectedKind (Report r, MemberCore mc, string expected, string was, Location loc)
 840                 {
 841                         string name;
 842                         if (mc != null)
 843                                 name = mc.GetSignatureForError ();
 844                         else
 845                                 name = GetSignatureForError ();
 846
 847                         r.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected",
 848                               name, was, expected);
 849                 }
 850
 851                 public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
 852                 {
 853                         string [] valid = new string [4];
 854                         int count = 0;
 855
 856                         if ((flags & ResolveFlags.VariableOrValue) != 0) {
 857                                 valid [count++] = "variable";
 858                                 valid [count++] = "value";
 859                         }
 860
 861                         if ((flags & ResolveFlags.Type) != 0)
 862                                 valid [count++] = "type";
 863
 864                         if ((flags & ResolveFlags.MethodGroup) != 0)
 865                                 valid [count++] = "method group";
 866
 867                         if (count == 0)
 868                                 valid [count++] = "unknown";
 869
 870                         StringBuilder sb = new StringBuilder (valid [0]);
 871                         for (int i = 1; i < count - 1; i++) {
 872                                 sb.Append ("', `");
 873                                 sb.Append (valid [i]);
 874                         }
 875                         if (count > 1) {
 876                                 sb.Append ("' or `");
 877                                 sb.Append (valid [count - 1]);
 878                         }
 879
 880                         ec.Report.Error (119, loc,
 881                                 "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
 882                 }
 883
 884                 public static void UnsafeError (ResolveContext ec, Location loc)
 885                 {
 886                         UnsafeError (ec.Report, loc);
 887                 }
 888
 889                 public static void UnsafeError (Report Report, Location loc)
 890                 {
 891                         Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
 892                 }
 893
 894                 //
 895                 // Converts `source' to an int, uint, long or ulong.
 896                 //
 897                 protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source)
 898                 {
 899                         var btypes = ec.BuiltinTypes;
 900
 901                         if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 902                                 Arguments args = new Arguments (1);
 903                                 args.Add (new Argument (source));
 904                                 return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, loc).Resolve (ec);
 905                         }
 906
 907                         Expression converted;
 908
 909                         using (ec.Set (ResolveContext.Options.CheckedScope)) {
 910                                 converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
 911                                 if (converted == null)
 912                                         converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
 913                                 if (converted == null)
 914                                         converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
 915                                 if (converted == null)
 916                                         converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);
 917
 918                                 if (converted == null) {
 919                                         source.Error_ValueCannotBeConverted (ec, source.loc, btypes.Int, false);
 920                                         return null;
 921                                 }
 922                         }
 923
 924                         //
 925                         // Only positive constants are allowed at compile time
 926                         //
 927                         Constant c = converted as Constant;
 928                         if (c != null && c.IsNegative)
 929                                 Error_NegativeArrayIndex (ec, source.loc);
 930
 931                         // No conversion needed to array index
 932                         if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
 933                                 return converted;
 934
 935                         return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
 936                 }
 937
 938                 //
 939                 // Derived classes implement this method by cloning the fields that
 940                 // could become altered during the Resolve stage
 941                 //
 942                 // Only expressions that are created for the parser need to implement
 943                 // this.
 944                 //
 945                 protected virtual void CloneTo (CloneContext clonectx, Expression target)
 946                 {
 947                         throw new NotImplementedException (
 948                                 String.Format (
 949                                         "CloneTo not implemented for expression {0}", this.GetType ()));
 950                 }
 951
 952                 //
 953                 // Clones an expression created by the parser.
 954                 //
 955                 // We only support expressions created by the parser so far, not
 956                 // expressions that have been resolved (many more classes would need
 957                 // to implement CloneTo).
 958                 //
 959                 // This infrastructure is here merely for Lambda expressions which
 960                 // compile the same code using different type values for the same
 961                 // arguments to find the correct overload
 962                 //
 963                 public virtual Expression Clone (CloneContext clonectx)
 964                 {
 965                         Expression cloned = (Expression) MemberwiseClone ();
 966                         CloneTo (clonectx, cloned);
 967
 968                         return cloned;
 969                 }
 970
 971                 //
 972                 // Implementation of expression to expression tree conversion
 973                 //
 974                 public abstract Expression CreateExpressionTree (ResolveContext ec);
 975
 976                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
 977                 {
 978                         return CreateExpressionFactoryCall (ec, name, null, args, loc);
 979                 }
 980
 981                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
 982                 {
 983                         return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
 984                 }
 985
 986                 public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
 987                 {
 988                         return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
 989                 }
 990
 991                 protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
 992                 {
 993                         var t = ec.Module.PredefinedTypes.Expression.Resolve ();
 994                         if (t == null)
 995                                 return null;
 996
 997                         return new TypeExpression (t, loc);
 998                 }
 999
1000                 //
1001                 // Implemented by all expressions which support conversion from
1002                 // compiler expression to invokable runtime expression. Used by
1003                 // dynamic C# binder.
1004                 //
1005                 public virtual SLE.Expression MakeExpression (BuilderContext ctx)
1006                 {
1007                         throw new NotImplementedException ("MakeExpression for " + GetType ());
1008                 }
1009         }
1010
1011         /// <summary>
1012         ///   This is just a base class for expressions that can
1013         ///   appear on statements (invocations, object creation,
1014         ///   assignments, post/pre increment and decrement).  The idea
1015         ///   being that they would support an extra Emition interface that
1016         ///   does not leave a result on the stack.
1017         /// </summary>
1018         public abstract class ExpressionStatement : Expression {
1019
1020                 public ExpressionStatement ResolveStatement (BlockContext ec)
1021                 {
1022                         Expression e = Resolve (ec);
1023                         if (e == null)
1024                                 return null;
1025
1026                         ExpressionStatement es = e as ExpressionStatement;
1027                         if (es == null)
1028                                 Error_InvalidExpressionStatement (ec);
1029
1030                         return es;
1031                 }
1032
1033                 /// <summary>
1034                 ///   Requests the expression to be emitted in a `statement'
1035                 ///   context.  This means that no new value is left on the
1036                 ///   stack after invoking this method (constrasted with
1037                 ///   Emit that will always leave a value on the stack).
1038                 /// </summary>
1039                 public abstract void EmitStatement (EmitContext ec);
1040
1041                 public override void EmitSideEffect (EmitContext ec)
1042                 {
1043                         EmitStatement (ec);
1044                 }
1045         }
1046
1047         /// <summary>
1048         ///   This kind of cast is used to encapsulate the child
1049         ///   whose type is child.Type into an expression that is
1050         ///   reported to return "return_type".  This is used to encapsulate
1051         ///   expressions which have compatible types, but need to be dealt
1052         ///   at higher levels with.
1053         ///
1054         ///   For example, a "byte" expression could be encapsulated in one
1055         ///   of these as an "unsigned int".  The type for the expression
1056         ///   would be "unsigned int".
1057         ///
1058         /// </summary>
1059         public abstract class TypeCast : Expression
1060         {
1061                 protected readonly Expression child;
1062
1063                 protected TypeCast (Expression child, TypeSpec return_type)
1064                 {
1065                         eclass = child.eclass;
1066                         loc = child.Location;
1067                         type = return_type;
1068                         this.child = child;
1069                 }
1070
1071                 public Expression Child {
1072                         get {
1073                                 return child;
1074                         }
1075                 }
1076
1077                 public override bool ContainsEmitWithAwait ()
1078                 {
1079                         return child.ContainsEmitWithAwait ();
1080                 }
1081
1082                 public override Expression CreateExpressionTree (ResolveContext ec)
1083                 {
1084                         Arguments args = new Arguments (2);
1085                         args.Add (new Argument (child.CreateExpressionTree (ec)));
1086                         args.Add (new Argument (new TypeOf (type, loc)));
1087
1088                         if (type.IsPointer || child.Type.IsPointer)
1089                                 Error_PointerInsideExpressionTree (ec);
1090
1091                         return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
1092                 }
1093
1094                 protected override Expression DoResolve (ResolveContext ec)
1095                 {
1096                         // This should never be invoked, we are born in fully
1097                         // initialized state.
1098
1099                         return this;
1100                 }
1101
1102                 public override void Emit (EmitContext ec)
1103                 {
1104                         child.Emit (ec);
1105                 }
1106
1107                 public override SLE.Expression MakeExpression (BuilderContext ctx)
1108                 {
1109 #if STATIC
1110                         return base.MakeExpression (ctx);
1111 #else
1112                         return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
1113                                 SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
1114                                 SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
1115 #endif
1116                 }
1117
1118                 protected override void CloneTo (CloneContext clonectx, Expression t)
1119                 {
1120                         // Nothing to clone
1121                 }
1122
1123                 public override bool IsNull {
1124                         get { return child.IsNull; }
1125                 }
1126         }
1127
1128         public class EmptyCast : TypeCast {
1129                 EmptyCast (Expression child, TypeSpec target_type)
1130                         : base (child, target_type)
1131                 {
1132                 }
1133
1134                 public static Expression Create (Expression child, TypeSpec type)
1135                 {
1136                         Constant c = child as Constant;
1137                         if (c != null)
1138                                 return new EmptyConstantCast (c, type);
1139
1140                         EmptyCast e = child as EmptyCast;
1141                         if (e != null)
1142                                 return new EmptyCast (e.child, type);
1143
1144                         return new EmptyCast (child, type);
1145                 }
1146
1147                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1148                 {
1149                         child.EmitBranchable (ec, label, on_true);
1150                 }
1151
1152                 public override void EmitSideEffect (EmitContext ec)
1153                 {
1154                         child.EmitSideEffect (ec);
1155                 }
1156         }
1157
1158         //
1159         // Used for predefined type user operator (no obsolete check, etc.)
1160         //
1161         public class OperatorCast : TypeCast
1162         {
1163                 readonly MethodSpec conversion_operator;
1164
1165                 public OperatorCast (Expression expr, TypeSpec target_type)
1166                         : this (expr, target_type, target_type, false)
1167                 {
1168                 }
1169
1170                 public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
1171                         : this (expr, target_type, target_type, find_explicit)
1172                 {
1173                 }
1174
1175                 public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
1176                         : base (expr, returnType)
1177                 {
1178                         var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
1179                         var mi = MemberCache.GetUserOperator (declaringType, op, true);
1180
1181                         if (mi != null) {
1182                                 foreach (MethodSpec oper in mi) {
1183                                         if (oper.ReturnType != returnType)
1184                                                 continue;
1185
1186                                         if (oper.Parameters.Types[0] == expr.Type) {
1187                                                 conversion_operator = oper;
1188                                                 return;
1189                                         }
1190                                 }
1191                         }
1192
1193                         throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
1194                                 returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
1195                 }
1196
1197                 public override void Emit (EmitContext ec)
1198                 {
1199                         child.Emit (ec);
1200                         ec.Emit (OpCodes.Call, conversion_operator);
1201                 }
1202         }
1203
1204         //
1205         // Constant specialization of EmptyCast.
1206         // We need to special case this since an empty cast of
1207         // a constant is still a constant.
1208         //
1209         public class EmptyConstantCast : Constant
1210         {
1211                 public readonly Constant child;
1212
1213                 public EmptyConstantCast (Constant child, TypeSpec type)
1214                         : base (child.Location)
1215                 {
1216                         if (child == null)
1217                                 throw new ArgumentNullException ("child");
1218
1219                         this.child = child;
1220                         this.eclass = child.eclass;
1221                         this.type = type;
1222                 }
1223
1224                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1225                 {
1226                         if (child.Type == target_type)
1227                                 return child;
1228
1229                         // FIXME: check that 'type' can be converted to 'target_type' first
1230                         return child.ConvertExplicitly (in_checked_context, target_type);
1231                 }
1232
1233                 public override Expression CreateExpressionTree (ResolveContext ec)
1234                 {
1235                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
1236                                 child.CreateExpressionTree (ec),
1237                                 new TypeOf (type, loc));
1238
1239                         if (type.IsPointer)
1240                                 Error_PointerInsideExpressionTree (ec);
1241
1242                         return CreateExpressionFactoryCall (ec, "Convert", args);
1243                 }
1244
1245                 public override bool IsDefaultValue {
1246                         get { return child.IsDefaultValue; }
1247                 }
1248
1249                 public override bool IsNegative {
1250                         get { return child.IsNegative; }
1251                 }
1252
1253                 public override bool IsNull {
1254                         get { return child.IsNull; }
1255                 }
1256
1257                 public override bool IsOneInteger {
1258                         get { return child.IsOneInteger; }
1259                 }
1260
1261                 public override bool IsSideEffectFree {
1262                         get {
1263                                 return child.IsSideEffectFree;
1264                         }
1265                 }
1266
1267                 public override bool IsZeroInteger {
1268                         get { return child.IsZeroInteger; }
1269                 }
1270
1271                 public override void Emit (EmitContext ec)
1272                 {
1273                         child.Emit (ec);
1274                 }
1275
1276                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1277                 {
1278                         child.EmitBranchable (ec, label, on_true);
1279
1280                         // Only to make verifier happy
1281                         if (TypeManager.IsGenericParameter (type) && child.IsNull)
1282                                 ec.Emit (OpCodes.Unbox_Any, type);
1283                 }
1284
1285                 public override void EmitSideEffect (EmitContext ec)
1286                 {
1287                         child.EmitSideEffect (ec);
1288                 }
1289
1290                 public override object GetValue ()
1291                 {
1292                         return child.GetValue ();
1293                 }
1294
1295                 public override string GetValueAsLiteral ()
1296                 {
1297                         return child.GetValueAsLiteral ();
1298                 }
1299
1300                 public override long GetValueAsLong ()
1301                 {
1302                         return child.GetValueAsLong ();
1303                 }
1304
1305                 public override Constant ConvertImplicitly (TypeSpec target_type)
1306                 {
1307                         if (type == target_type)
1308                                 return this;
1309
1310                         // FIXME: Do we need to check user conversions?
1311                         if (!Convert.ImplicitStandardConversionExists (this, target_type))
1312                                 return null;
1313
1314                         return child.ConvertImplicitly (target_type);
1315                 }
1316         }
1317
1318         /// <summary>
1319         ///  This class is used to wrap literals which belong inside Enums
1320         /// </summary>
1321         public class EnumConstant : Constant
1322         {
1323                 public Constant Child;
1324
1325                 public EnumConstant (Constant child, TypeSpec enum_type)
1326                         : base (child.Location)
1327                 {
1328                         this.Child = child;
1329
1330                         this.eclass = ExprClass.Value;
1331                         this.type = enum_type;
1332                 }
1333
1334                 protected EnumConstant (Location loc)
1335                         : base (loc)
1336                 {
1337                 }
1338
1339                 public override void Emit (EmitContext ec)
1340                 {
1341                         Child.Emit (ec);
1342                 }
1343
1344                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1345                 {
1346                         Child.EncodeAttributeValue (rc, enc, Child.Type);
1347                 }
1348
1349                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1350                 {
1351                         Child.EmitBranchable (ec, label, on_true);
1352                 }
1353
1354                 public override void EmitSideEffect (EmitContext ec)
1355                 {
1356                         Child.EmitSideEffect (ec);
1357                 }
1358
1359                 public override string GetSignatureForError()
1360                 {
1361                         return TypeManager.CSharpName (Type);
1362                 }
1363
1364                 public override object GetValue ()
1365                 {
1366                         return Child.GetValue ();
1367                 }
1368
1369 #if !STATIC
1370                 public override object GetTypedValue ()
1371                 {
1372                         //
1373                         // The method can be used in dynamic context only (on closed types)
1374                         //
1375                         // System.Enum.ToObject cannot be called on dynamic types
1376                         // EnumBuilder has to be used, but we cannot use EnumBuilder
1377                         // because it does not properly support generics
1378                         //
1379                         return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
1380                 }
1381 #endif
1382
1383                 public override string GetValueAsLiteral ()
1384                 {
1385                         return Child.GetValueAsLiteral ();
1386                 }
1387
1388                 public override long GetValueAsLong ()
1389                 {
1390                         return Child.GetValueAsLong ();
1391                 }
1392
1393                 public EnumConstant Increment()
1394                 {
1395                         return new EnumConstant (((IntegralConstant) Child).Increment (), type);
1396                 }
1397
1398                 public override bool IsDefaultValue {
1399                         get {
1400                                 return Child.IsDefaultValue;
1401                         }
1402                 }
1403
1404                 public override bool IsSideEffectFree {
1405                         get {
1406                                 return Child.IsSideEffectFree;
1407                         }
1408                 }
1409
1410                 public override bool IsZeroInteger {
1411                         get { return Child.IsZeroInteger; }
1412                 }
1413
1414                 public override bool IsNegative {
1415                         get {
1416                                 return Child.IsNegative;
1417                         }
1418                 }
1419
1420                 public override Constant ConvertExplicitly(bool in_checked_context, TypeSpec target_type)
1421                 {
1422                         if (Child.Type == target_type)
1423                                 return Child;
1424
1425                         return Child.ConvertExplicitly (in_checked_context, target_type);
1426                 }
1427
1428                 public override Constant ConvertImplicitly (TypeSpec type)
1429                 {
1430                         if (this.type == type) {
1431                                 return this;
1432                         }
1433
1434                         if (!Convert.ImplicitStandardConversionExists (this, type)){
1435                                 return null;
1436                         }
1437
1438                         return Child.ConvertImplicitly (type);
1439                 }
1440         }
1441
1442         /// <summary>
1443         ///   This kind of cast is used to encapsulate Value Types in objects.
1444         ///
1445         ///   The effect of it is to box the value type emitted by the previous
1446         ///   operation.
1447         /// </summary>
1448         public class BoxedCast : TypeCast {
1449
1450                 public BoxedCast (Expression expr, TypeSpec target_type)
1451                         : base (expr, target_type)
1452                 {
1453                         eclass = ExprClass.Value;
1454                 }
1455
1456                 protected override Expression DoResolve (ResolveContext ec)
1457                 {
1458                         // This should never be invoked, we are born in fully
1459                         // initialized state.
1460
1461                         return this;
1462                 }
1463
1464                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1465                 {
1466                         // Only boxing to object type is supported
1467                         if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
1468                                 base.EncodeAttributeValue (rc, enc, targetType);
1469                                 return;
1470                         }
1471
1472                         enc.Encode (child.Type);
1473                         child.EncodeAttributeValue (rc, enc, child.Type);
1474                 }
1475
1476                 public override void Emit (EmitContext ec)
1477                 {
1478                         base.Emit (ec);
1479
1480                         ec.Emit (OpCodes.Box, child.Type);
1481                 }
1482
1483                 public override void EmitSideEffect (EmitContext ec)
1484                 {
1485                         // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
1486                         // so, we need to emit the box+pop instructions in most cases
1487                         if (child.Type.IsStruct &&
1488                             (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
1489                                 child.EmitSideEffect (ec);
1490                         else
1491                                 base.EmitSideEffect (ec);
1492                 }
1493         }
1494
1495         public class UnboxCast : TypeCast {
1496                 public UnboxCast (Expression expr, TypeSpec return_type)
1497                         : base (expr, return_type)
1498                 {
1499                 }
1500
1501                 protected override Expression DoResolve (ResolveContext ec)
1502                 {
1503                         // This should never be invoked, we are born in fully
1504                         // initialized state.
1505
1506                         return this;
1507                 }
1508
1509                 public override void Emit (EmitContext ec)
1510                 {
1511                         base.Emit (ec);
1512
1513                         ec.Emit (OpCodes.Unbox_Any, type);
1514                 }
1515         }
1516
1517         /// <summary>
1518         ///   This is used to perform explicit numeric conversions.
1519         ///
1520         ///   Explicit numeric conversions might trigger exceptions in a checked
1521         ///   context, so they should generate the conv.ovf opcodes instead of
1522         ///   conv opcodes.
1523         /// </summary>
1524         public class ConvCast : TypeCast {
1525                 public enum Mode : byte {
1526                         I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
1527                         U1_I1, U1_CH,
1528                         I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
1529                         U2_I1, U2_U1, U2_I2, U2_CH,
1530                         I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
1531                         U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
1532                         I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
1533                         U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
1534                         CH_I1, CH_U1, CH_I2,
1535                         R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
1536                         R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
1537                         I_I8,
1538                 }
1539
1540                 Mode mode;
1541
1542                 public ConvCast (Expression child, TypeSpec return_type, Mode m)
1543                         : base (child, return_type)
1544                 {
1545                         mode = m;
1546                 }
1547
1548                 protected override Expression DoResolve (ResolveContext ec)
1549                 {
1550                         // This should never be invoked, we are born in fully
1551                         // initialized state.
1552
1553                         return this;
1554                 }
1555
1556                 public override string ToString ()
1557                 {
1558                         return String.Format ("ConvCast ({0}, {1})", mode, child);
1559                 }
1560
1561                 public override void Emit (EmitContext ec)
1562                 {
1563                         base.Emit (ec);
1564
1565                         if (ec.HasSet (EmitContext.Options.CheckedScope)) {
1566                                 switch (mode){
1567                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1568                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1569                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1570                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1571                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1572
1573                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1574                                 case Mode.U1_CH: /* nothing */ break;
1575
1576                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1577                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1578                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1579                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1580                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1581                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1582
1583                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1584                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1585                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1586                                 case Mode.U2_CH: /* nothing */ break;
1587
1588                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1589                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1590                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1591                                 case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1592                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1593                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1594                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1595
1596                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1597                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1598                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1599                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1600                                 case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1601                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1602
1603                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1604                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1605                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1606                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1607                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1608                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1609                                 case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1610                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1611                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;
1612
1613                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1614                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1615                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1616                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1617                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1618                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
1619                                 case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1620                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1621                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;
1622
1623                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1624                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1625                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1626
1627                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1628                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1629                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1630                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1631                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1632                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1633                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1634                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1635                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1636
1637                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1638                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1639                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1640                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1641                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1642                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1643                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1644                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1645                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1646                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1647
1648                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1649                                 }
1650                         } else {
1651                                 switch (mode){
1652                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
1653                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
1654                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
1655                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
1656                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;
1657
1658                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
1659                                 case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;
1660
1661                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
1662                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
1663                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
1664                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
1665                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
1666                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;
1667
1668                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
1669                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
1670                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
1671                                 case Mode.U2_CH: /* nothing */ break;
1672
1673                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
1674                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
1675                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
1676                                 case Mode.I4_U4: /* nothing */ break;
1677                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_U2); break;
1678                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_I8); break;
1679                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_U2); break;
1680
1681                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_I1); break;
1682                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_U1); break;
1683                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_I2); break;
1684                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_U2); break;
1685                                 case Mode.U4_I4: /* nothing */ break;
1686                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_U2); break;
1687
1688                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_I1); break;
1689                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_U1); break;
1690                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_I2); break;
1691                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_U2); break;
1692                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_I4); break;
1693                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_U4); break;
1694                                 case Mode.I8_U8: /* nothing */ break;
1695                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_U2); break;
1696                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_U); break;
1697
1698                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_I1); break;
1699                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_U1); break;
1700                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_I2); break;
1701                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_U2); break;
1702                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_I4); break;
1703                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_U4); break;
1704                                 case Mode.U8_I8: /* nothing */ break;
1705                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_U2); break;
1706                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_U); break;
1707
1708                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_I1); break;
1709                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_U1); break;
1710                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_I2); break;
1711
1712                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_I1); break;
1713                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_U1); break;
1714                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_I2); break;
1715                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_U2); break;
1716                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_I4); break;
1717                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_U4); break;
1718                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_I8); break;
1719                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_U8); break;
1720                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_U2); break;
1721
1722                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_I1); break;
1723                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_U1); break;
1724                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_I2); break;
1725                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_U2); break;
1726                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_I4); break;
1727                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_U4); break;
1728                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_I8); break;
1729                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_U8); break;
1730                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_U2); break;
1731                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1732
1733                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_U8); break;
1734                                 }
1735                         }
1736                 }
1737         }
1738
1739         class OpcodeCast : TypeCast
1740         {
1741                 readonly OpCode op;
1742
1743                 public OpcodeCast (Expression child, TypeSpec return_type, OpCode op)
1744                         : base (child, return_type)
1745                 {
1746                         this.op = op;
1747                 }
1748
1749                 protected override Expression DoResolve (ResolveContext ec)
1750                 {
1751                         // This should never be invoked, we are born in fully
1752                         // initialized state.
1753
1754                         return this;
1755                 }
1756
1757                 public override void Emit (EmitContext ec)
1758                 {
1759                         base.Emit (ec);
1760                         ec.Emit (op);
1761                 }
1762
1763                 public TypeSpec UnderlyingType {
1764                         get { return child.Type; }
1765                 }
1766         }
1767
1768         //
1769         // Opcode casts expression with 2 opcodes but only
1770         // single expression tree node
1771         //
1772         class OpcodeCastDuplex : OpcodeCast
1773         {
1774                 readonly OpCode second;
1775
1776                 public OpcodeCastDuplex (Expression child, TypeSpec returnType, OpCode first, OpCode second)
1777                         : base (child, returnType, first)
1778                 {
1779                         this.second = second;
1780                 }
1781
1782                 public override void Emit (EmitContext ec)
1783                 {
1784                         base.Emit (ec);
1785                         ec.Emit (second);
1786                 }
1787         }
1788
1789         /// <summary>
1790         ///   This kind of cast is used to encapsulate a child and cast it
1791         ///   to the class requested
1792         /// </summary>
1793         public sealed class ClassCast : TypeCast {
1794                 readonly bool forced;
1795
1796                 public ClassCast (Expression child, TypeSpec return_type)
1797                         : base (child, return_type)
1798                 {
1799                 }
1800
1801                 public ClassCast (Expression child, TypeSpec return_type, bool forced)
1802                         : base (child, return_type)
1803                 {
1804                         this.forced = forced;
1805                 }
1806
1807                 public override void Emit (EmitContext ec)
1808                 {
1809                         base.Emit (ec);
1810
1811                         bool gen = TypeManager.IsGenericParameter (child.Type);
1812                         if (gen)
1813                                 ec.Emit (OpCodes.Box, child.Type);
1814
1815                         if (type.IsGenericParameter) {
1816                                 ec.Emit (OpCodes.Unbox_Any, type);
1817                                 return;
1818                         }
1819
1820                         if (gen && !forced)
1821                                 return;
1822
1823                         ec.Emit (OpCodes.Castclass, type);
1824                 }
1825         }
1826
1827         //
1828         // Created during resolving pahse when an expression is wrapped or constantified
1829         // and original expression can be used later (e.g. for expression trees)
1830         //
1831         public class ReducedExpression : Expression
1832         {
1833                 sealed class ReducedConstantExpression : EmptyConstantCast
1834                 {
1835                         readonly Expression orig_expr;
1836
1837                         public ReducedConstantExpression (Constant expr, Expression orig_expr)
1838                                 : base (expr, expr.Type)
1839                         {
1840                                 this.orig_expr = orig_expr;
1841                         }
1842
1843                         public override Constant ConvertImplicitly (TypeSpec target_type)
1844                         {
1845                                 Constant c = base.ConvertImplicitly (target_type);
1846                                 if (c != null)
1847                                         c = new ReducedConstantExpression (c, orig_expr);
1848
1849                                 return c;
1850                         }
1851
1852                         public override Expression CreateExpressionTree (ResolveContext ec)
1853                         {
1854                                 return orig_expr.CreateExpressionTree (ec);
1855                         }
1856
1857                         public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1858                         {
1859                                 Constant c = base.ConvertExplicitly (in_checked_context, target_type);
1860                                 if (c != null)
1861                                         c = new ReducedConstantExpression (c, orig_expr);
1862                                 return c;
1863                         }
1864
1865                         public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1866                         {
1867                                 //
1868                                 // LAMESPEC: Reduced conditional expression is allowed as an attribute argument
1869                                 //
1870                                 if (orig_expr is Conditional)
1871                                         child.EncodeAttributeValue (rc, enc, targetType);
1872                                 else
1873                                         base.EncodeAttributeValue (rc, enc, targetType);
1874                         }
1875                 }
1876
1877                 sealed class ReducedExpressionStatement : ExpressionStatement
1878                 {
1879                         readonly Expression orig_expr;
1880                         readonly ExpressionStatement stm;
1881
1882                         public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
1883                         {
1884                                 this.orig_expr = orig;
1885                                 this.stm = stm;
1886                                 this.eclass = stm.eclass;
1887                                 this.type = stm.Type;
1888
1889                                 this.loc = orig.Location;
1890                         }
1891
1892                         public override bool ContainsEmitWithAwait ()
1893                         {
1894                                 return stm.ContainsEmitWithAwait ();
1895                         }
1896
1897                         public override Expression CreateExpressionTree (ResolveContext ec)
1898                         {
1899                                 return orig_expr.CreateExpressionTree (ec);
1900                         }
1901
1902                         protected override Expression DoResolve (ResolveContext ec)
1903                         {
1904                                 return this;
1905                         }
1906
1907                         public override void Emit (EmitContext ec)
1908                         {
1909                                 stm.Emit (ec);
1910                         }
1911
1912                         public override void EmitStatement (EmitContext ec)
1913                         {
1914                                 stm.EmitStatement (ec);
1915                         }
1916                 }
1917
1918                 readonly Expression expr, orig_expr;
1919
1920                 private ReducedExpression (Expression expr, Expression orig_expr)
1921                 {
1922                         this.expr = expr;
1923                         this.eclass = expr.eclass;
1924                         this.type = expr.Type;
1925                         this.orig_expr = orig_expr;
1926                         this.loc = orig_expr.Location;
1927                 }
1928
1929                 #region Properties
1930
1931                 public Expression OriginalExpression {
1932                         get {
1933                                 return orig_expr;
1934                         }
1935                 }
1936
1937                 #endregion
1938
1939                 public override bool ContainsEmitWithAwait ()
1940                 {
1941                         return expr.ContainsEmitWithAwait ();
1942                 }
1943
1944                 //
1945                 // Creates fully resolved expression switcher
1946                 //
1947                 public static Constant Create (Constant expr, Expression original_expr)
1948                 {
1949                         if (expr.eclass == ExprClass.Unresolved)
1950                                 throw new ArgumentException ("Unresolved expression");
1951
1952                         return new ReducedConstantExpression (expr, original_expr);
1953                 }
1954
1955                 public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
1956                 {
1957                         return new ReducedExpressionStatement (s, orig);
1958                 }
1959
1960                 public static Expression Create (Expression expr, Expression original_expr)
1961                 {
1962                         return Create (expr, original_expr, true);
1963                 }
1964
1965                 //
1966                 // Creates unresolved reduce expression. The original expression has to be
1967                 // already resolved. Created expression is constant based based on `expr'
1968                 // value unless canBeConstant is used
1969                 //
1970                 public static Expression Create (Expression expr, Expression original_expr, bool canBeConstant)
1971                 {
1972                         if (canBeConstant) {
1973                                 Constant c = expr as Constant;
1974                                 if (c != null)
1975                                         return Create (c, original_expr);
1976                         }
1977
1978                         ExpressionStatement s = expr as ExpressionStatement;
1979                         if (s != null)
1980                                 return Create (s, original_expr);
1981
1982                         if (expr.eclass == ExprClass.Unresolved)
1983                                 throw new ArgumentException ("Unresolved expression");
1984
1985                         return new ReducedExpression (expr, original_expr);
1986                 }
1987
1988                 public override Expression CreateExpressionTree (ResolveContext ec)
1989                 {
1990                         return orig_expr.CreateExpressionTree (ec);
1991                 }
1992
1993                 protected override Expression DoResolve (ResolveContext ec)
1994                 {
1995                         return this;
1996                 }
1997
1998                 public override void Emit (EmitContext ec)
1999                 {
2000                         expr.Emit (ec);
2001                 }
2002
2003                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2004                 {
2005                         expr.EmitBranchable (ec, target, on_true);
2006                 }
2007
2008                 public override SLE.Expression MakeExpression (BuilderContext ctx)
2009                 {
2010                         return orig_expr.MakeExpression (ctx);
2011                 }
2012         }
2013
2014         //
2015         // Standard composite pattern
2016         //
2017         public abstract class CompositeExpression : Expression
2018         {
2019                 protected Expression expr;
2020
2021                 protected CompositeExpression (Expression expr)
2022                 {
2023                         this.expr = expr;
2024                         this.loc = expr.Location;
2025                 }
2026
2027                 public override bool ContainsEmitWithAwait ()
2028                 {
2029                         return expr.ContainsEmitWithAwait ();
2030                 }
2031
2032                 public override Expression CreateExpressionTree (ResolveContext rc)
2033                 {
2034                         return expr.CreateExpressionTree (rc);
2035                 }
2036
2037                 public Expression Child {
2038                         get { return expr; }
2039                 }
2040
2041                 protected override Expression DoResolve (ResolveContext rc)
2042                 {
2043                         expr = expr.Resolve (rc);
2044                         if (expr != null) {
2045                                 type = expr.Type;
2046                                 eclass = expr.eclass;
2047                         }
2048
2049                         return this;
2050                 }
2051
2052                 public override void Emit (EmitContext ec)
2053                 {
2054                         expr.Emit (ec);
2055                 }
2056
2057                 public override bool IsNull {
2058                         get { return expr.IsNull; }
2059                 }
2060         }
2061
2062         //
2063         // Base of expressions used only to narrow resolve flow
2064         //
2065         public abstract class ShimExpression : Expression
2066         {
2067                 protected Expression expr;
2068
2069                 protected ShimExpression (Expression expr)
2070                 {
2071                         this.expr = expr;
2072                 }
2073
2074                 public Expression Expr {
2075                         get {
2076                                 return expr;
2077                         }
2078                 }
2079
2080                 protected override void CloneTo (CloneContext clonectx, Expression t)
2081                 {
2082                         if (expr == null)
2083                                 return;
2084
2085                         ShimExpression target = (ShimExpression) t;
2086                         target.expr = expr.Clone (clonectx);
2087                 }
2088
2089                 public override bool ContainsEmitWithAwait ()
2090                 {
2091                         return expr.ContainsEmitWithAwait ();
2092                 }
2093
2094                 public override Expression CreateExpressionTree (ResolveContext ec)
2095                 {
2096                         throw new NotSupportedException ("ET");
2097                 }
2098
2099                 public override void Emit (EmitContext ec)
2100                 {
2101                         throw new InternalErrorException ("Missing Resolve call");
2102                 }
2103
2104         }
2105
2106         //
2107         // Unresolved type name expressions
2108         //
2109         public abstract class ATypeNameExpression : FullNamedExpression
2110         {
2111                 string name;
2112                 protected TypeArguments targs;
2113
2114                 protected ATypeNameExpression (string name, Location l)
2115                 {
2116                         this.name = name;
2117                         loc = l;
2118                 }
2119
2120                 protected ATypeNameExpression (string name, TypeArguments targs, Location l)
2121                 {
2122                         this.name = name;
2123                         this.targs = targs;
2124                         loc = l;
2125                 }
2126
2127                 protected ATypeNameExpression (string name, int arity, Location l)
2128                         : this (name, new UnboundTypeArguments (arity), l)
2129                 {
2130                 }
2131
2132                 #region Properties
2133
2134                 protected int Arity {
2135                         get {
2136                                 return targs == null ? 0 : targs.Count;
2137                         }
2138                 }
2139
2140                 public bool HasTypeArguments {
2141                         get {
2142                                 return targs != null && !targs.IsEmpty;
2143                         }
2144                 }
2145
2146                 public string Name {
2147                         get {
2148                                 return name;
2149                         }
2150                         set {
2151                                 name = value;
2152                         }
2153                 }
2154
2155                 public TypeArguments TypeArguments {
2156                         get {
2157                                 return targs;
2158                         }
2159                 }
2160
2161                 #endregion
2162
2163                 public override bool Equals (object obj)
2164                 {
2165                         ATypeNameExpression atne = obj as ATypeNameExpression;
2166                         return atne != null && atne.Name == Name &&
2167                                 (targs == null || targs.Equals (atne.targs));
2168                 }
2169
2170                 public override int GetHashCode ()
2171                 {
2172                         return Name.GetHashCode ();
2173                 }
2174
2175                 // TODO: Move it to MemberCore
2176                 public static string GetMemberType (MemberCore mc)
2177                 {
2178                         if (mc is Property)
2179                                 return "property";
2180                         if (mc is Indexer)
2181                                 return "indexer";
2182                         if (mc is FieldBase)
2183                                 return "field";
2184                         if (mc is MethodCore)
2185                                 return "method";
2186                         if (mc is EnumMember)
2187                                 return "enum";
2188                         if (mc is Event)
2189                                 return "event";
2190
2191                         return "type";
2192                 }
2193
2194                 public override string GetSignatureForError ()
2195                 {
2196                         if (targs != null) {
2197                                 return Name + "<" + targs.GetSignatureForError () + ">";
2198                         }
2199
2200                         return Name;
2201                 }
2202
2203                 public abstract Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restriction);
2204         }
2205
2206         /// <summary>
2207         ///   SimpleName expressions are formed of a single word and only happen at the beginning
2208         ///   of a dotted-name.
2209         /// </summary>
2210         public class SimpleName : ATypeNameExpression
2211         {
2212                 public SimpleName (string name, Location l)
2213                         : base (name, l)
2214                 {
2215                 }
2216
2217                 public SimpleName (string name, TypeArguments args, Location l)
2218                         : base (name, args, l)
2219                 {
2220                 }
2221
2222                 public SimpleName (string name, int arity, Location l)
2223                         : base (name, arity, l)
2224                 {
2225                 }
2226
2227                 public SimpleName GetMethodGroup ()
2228                 {
2229                         return new SimpleName (Name, targs, loc);
2230                 }
2231
2232                 protected override Expression DoResolve (ResolveContext rc)
2233                 {
2234                         var e = SimpleNameResolve (rc, null, false);
2235
2236                         var fe = e as FieldExpr;
2237                         if (fe != null) {
2238                                 fe.VerifyAssignedStructField (rc, null);
2239                         }
2240
2241                         return e;
2242                 }
2243
2244                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
2245                 {
2246                         return SimpleNameResolve (ec, right_side, false);
2247                 }
2248
2249                 protected virtual void Error_TypeOrNamespaceNotFound (IMemberContext ctx)
2250                 {
2251                         if (ctx.CurrentType != null) {
2252                                 if (ctx.CurrentMemberDefinition != null) {
2253                                         MemberCore mc = ctx.CurrentMemberDefinition.Parent.GetDefinition (Name);
2254                                         if (mc != null) {
2255                                                 Error_UnexpectedKind (ctx.Module.Compiler.Report, mc, "type", GetMemberType (mc), loc);
2256                                                 return;
2257                                         }
2258                                 }
2259                         }
2260
2261                         var retval = ctx.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2262                         if (retval != null) {
2263                                 ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (retval.Type);
2264                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
2265                                 return;
2266                         }
2267
2268                         retval = ctx.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2269                         if (retval != null) {
2270                                 Error_TypeArgumentsCannotBeUsed (ctx, retval.Type, Arity, loc);
2271                                 return;
2272                         }
2273
2274                         NamespaceContainer.Error_NamespaceNotFound (loc, Name, ctx.Module.Compiler.Report);
2275                 }
2276
2277                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext ec)
2278                 {
2279                         FullNamedExpression fne = ec.LookupNamespaceOrType (Name, Arity, LookupMode.Normal, loc);
2280
2281                         if (fne != null) {
2282                                 if (fne.Type != null && Arity > 0) {
2283                                         if (HasTypeArguments) {
2284                                                 GenericTypeExpr ct = new GenericTypeExpr (fne.Type, targs, loc);
2285                                                 if (ct.ResolveAsType (ec) == null)
2286                                                         return null;
2287
2288                                                 return ct;
2289                                         }
2290
2291                                         return new GenericOpenTypeExpr (fne.Type, loc);
2292                                 }
2293
2294                                 //
2295                                 // dynamic namespace is ignored when dynamic is allowed (does not apply to types)
2296                                 //
2297                                 if (!(fne is Namespace))
2298                                         return fne;
2299                         }
2300
2301                         if (Arity == 0 && Name == "dynamic" && ec.Module.Compiler.Settings.Version > LanguageVersion.V_3) {
2302                                 if (!ec.Module.PredefinedAttributes.Dynamic.IsDefined) {
2303                                         ec.Module.Compiler.Report.Error (1980, Location,
2304                                                 "Dynamic keyword requires `{0}' to be defined. Are you missing System.Core.dll assembly reference?",
2305                                                 ec.Module.PredefinedAttributes.Dynamic.GetSignatureForError ());
2306                                 }
2307
2308                                 fne = new DynamicTypeExpr (loc);
2309                                 fne.ResolveAsType (ec);
2310                         }
2311
2312                         if (fne != null)
2313                                 return fne;
2314
2315                         Error_TypeOrNamespaceNotFound (ec);
2316                         return null;
2317                 }
2318
2319                 public bool IsPossibleTypeOrNamespace (IMemberContext mc)
2320                 {
2321                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
2322                 }
2323
2324                 public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
2325                 {
2326                         int lookup_arity = Arity;
2327                         bool errorMode = false;
2328                         Expression e;
2329                         Block current_block = rc.CurrentBlock;
2330                         INamedBlockVariable variable = null;
2331                         bool variable_found = false;
2332
2333                         while (true) {
2334                                 //
2335                                 // Stage 1: binding to local variables or parameters
2336                                 //
2337                                 // LAMESPEC: It should take invocableOnly into account but that would break csc compatibility
2338                                 //
2339                                 if (current_block != null && lookup_arity == 0) {
2340                                         if (current_block.ParametersBlock.TopBlock.GetLocalName (Name, current_block.Original, ref variable)) {
2341                                                 if (!variable.IsDeclared) {
2342                                                         // We found local name in accessible block but it's not
2343                                                         // initialized yet, maybe the user wanted to bind to something else
2344                                                         errorMode = true;
2345                                                         variable_found = true;
2346                                                 } else {
2347                                                         e = variable.CreateReferenceExpression (rc, loc);
2348                                                         if (e != null) {
2349                                                                 if (Arity > 0)
2350                                                                         Error_TypeArgumentsCannotBeUsed (rc, "variable", Name, loc);
2351
2352                                                                 return e;
2353                                                         }
2354                                                 }
2355                                         }
2356                                 }
2357
2358                                 //
2359                                 // Stage 2: Lookup members if we are inside a type up to top level type for nested types
2360                                 //
2361                                 TypeSpec member_type = rc.CurrentType;
2362                                 for (; member_type != null; member_type = member_type.DeclaringType) {
2363                                         e = MemberLookup (rc, errorMode, member_type, Name, lookup_arity, restrictions, loc);
2364                                         if (e == null)
2365                                                 continue;
2366
2367                                         var me = e as MemberExpr;
2368                                         if (me == null) {
2369                                                 // The name matches a type, defer to ResolveAsTypeStep
2370                                                 if (e is TypeExpr)
2371                                                         break;
2372
2373                                                 continue;
2374                                         }
2375
2376                                         if (errorMode) {
2377                                                 if (variable != null) {
2378                                                         if (me is FieldExpr || me is ConstantExpr || me is EventExpr || me is PropertyExpr) {
2379                                                                 rc.Report.Error (844, loc,
2380                                                                         "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the member `{1}'",
2381                                                                         Name, me.GetSignatureForError ());
2382                                                         } else {
2383                                                                 break;
2384                                                         }
2385                                                 } else if (me is MethodGroupExpr) {
2386                                                         // Leave it to overload resolution to report correct error
2387                                                 } else {
2388                                                         // TODO: rc.Report.SymbolRelatedToPreviousError ()
2389                                                         ErrorIsInaccesible (rc, me.GetSignatureForError (), loc);
2390                                                 }
2391                                         } else {
2392                                                 // LAMESPEC: again, ignores InvocableOnly
2393                                                 if (variable != null) {
2394                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2395                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2396                                                 }
2397
2398                                                 //
2399                                                 // MemberLookup does not check accessors availability, this is actually needed for properties only
2400                                                 //
2401                                                 var pe = me as PropertyExpr;
2402                                                 if (pe != null) {
2403
2404                                                         // Break as there is no other overload available anyway
2405                                                         if ((restrictions & MemberLookupRestrictions.ReadAccess) != 0) {
2406                                                                 if (!pe.PropertyInfo.HasGet || !pe.PropertyInfo.Get.IsAccessible (rc))
2407                                                                         break;
2408
2409                                                                 pe.Getter = pe.PropertyInfo.Get;
2410                                                         } else {
2411                                                                 if (!pe.PropertyInfo.HasSet || !pe.PropertyInfo.Set.IsAccessible (rc))
2412                                                                         break;
2413
2414                                                                 pe.Setter = pe.PropertyInfo.Set;
2415                                                         }
2416                                                 }
2417                                         }
2418
2419                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2420                                         // TODO: Should go to MemberAccess
2421                                         me = me.ResolveMemberAccess (rc, null, null);
2422
2423                                         if (Arity > 0) {
2424                                                 targs.Resolve (rc);
2425                                                 me.SetTypeArguments (rc, targs);
2426                                         }
2427
2428                                         return me;
2429                                 }
2430
2431                                 //
2432                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2433                                 //
2434                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2435                                         if (IsPossibleTypeOrNamespace (rc)) {
2436                                                 if (variable != null) {
2437                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2438                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2439                                                 }
2440
2441                                                 return ResolveAsTypeOrNamespace (rc);
2442                                         }
2443                                 }
2444
2445                                 if (errorMode) {
2446                                         if (variable_found) {
2447                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2448                                         } else {
2449                                                 if (Arity > 0) {
2450                                                         TypeParameter[] tparams = rc.CurrentTypeParameters;
2451                                                         if (tparams != null) {
2452                                                                 foreach (var ctp in tparams) {
2453                                                                         if (ctp.Name == Name) {
2454                                                                                 Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2455                                                                                 return null;
2456                                                                         }
2457                                                                 }
2458                                                         }
2459
2460                                                         var ct = rc.CurrentType;
2461                                                         do {
2462                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2463                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2464                                                                                 if (ctp.Name == Name) {
2465                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2466                                                                                         return null;
2467                                                                                 }
2468                                                                         }
2469                                                                 }
2470
2471                                                                 ct = ct.DeclaringType;
2472                                                         } while (ct != null);
2473                                                 }
2474
2475                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2476                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2477                                                         if (e != null) {
2478                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2479                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2480                                                                 return e;
2481                                                         }
2482                                                 }
2483
2484                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2485                                                 if (e != null) {
2486                                                         if (!(e is TypeExpr) || (restrictions & MemberLookupRestrictions.InvocableOnly) == 0 || !e.Type.IsDelegate) {
2487                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, Arity, loc);
2488                                                                 return e;
2489                                                         }
2490                                                 }
2491
2492                                                 rc.Report.Error (103, loc, "The name `{0}' does not exist in the current context", Name);
2493                                         }
2494
2495                                         return ErrorExpression.Instance;
2496                                 }
2497
2498                                 if (rc.Module.Evaluator != null) {
2499                                         var fi = rc.Module.Evaluator.LookupField (Name);
2500                                         if (fi != null)
2501                                                 return new FieldExpr (fi.Item1, loc);
2502                                 }
2503
2504                                 lookup_arity = 0;
2505                                 errorMode = true;
2506                         }
2507                 }
2508
2509                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side, bool intermediate)
2510                 {
2511                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2512
2513                         if (e == null)
2514                                 return null;
2515
2516                         if (right_side != null) {
2517                                 if (e is TypeExpr) {
2518                                     e.Error_UnexpectedKind (ec, ResolveFlags.VariableOrValue, loc);
2519                                     return null;
2520                                 }
2521
2522                                 e = e.ResolveLValue (ec, right_side);
2523                         } else {
2524                                 e = e.Resolve (ec);
2525                         }
2526
2527                         //if (ec.CurrentBlock == null || ec.CurrentBlock.CheckInvariantMeaningInBlock (Name, e, Location))
2528                         return e;
2529                 }
2530         }
2531
2532         /// <summary>
2533         ///   Represents a namespace or a type.  The name of the class was inspired by
2534         ///   section 10.8.1 (Fully Qualified Names).
2535         /// </summary>
2536         public abstract class FullNamedExpression : Expression
2537         {
2538                 protected override void CloneTo (CloneContext clonectx, Expression target)
2539                 {
2540                         // Do nothing, most unresolved type expressions cannot be
2541                         // resolved to different type
2542                 }
2543
2544                 public override bool ContainsEmitWithAwait ()
2545                 {
2546                         return false;
2547                 }
2548
2549                 public override Expression CreateExpressionTree (ResolveContext ec)
2550                 {
2551                         throw new NotSupportedException ("ET");
2552                 }
2553
2554                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc);
2555
2556                 //
2557                 // This is used to resolve the expression as a type, a null
2558                 // value will be returned if the expression is not a type
2559                 // reference
2560                 //
2561                 public override TypeSpec ResolveAsType (IMemberContext mc)
2562                 {
2563                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc);
2564
2565                         if (fne == null)
2566                                 return null;
2567
2568                         TypeExpr te = fne as TypeExpr;
2569                         if (te == null) {
2570                                 fne.Error_UnexpectedKind (mc.Module.Compiler.Report, null, "type", loc);
2571                                 return null;
2572                         }
2573
2574                         te.loc = loc;
2575
2576                         type = te.Type;
2577
2578                         var dep = type.GetMissingDependencies ();
2579                         if (dep != null) {
2580                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
2581                         }
2582
2583                         //
2584                         // Obsolete checks cannot be done when resolving base context as they
2585                         // require type dependencies to be set but we are in process of resolving them
2586                         //
2587                         if (!(mc is TypeContainer.BaseContext)) {
2588                                 ObsoleteAttribute obsolete_attr = type.GetAttributeObsolete ();
2589                                 if (obsolete_attr != null && !mc.IsObsolete) {
2590                                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location, mc.Module.Compiler.Report);
2591                                 }
2592                         }
2593
2594                         return type;
2595                 }
2596
2597
2598                 public override void Emit (EmitContext ec)
2599                 {
2600                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
2601                                 GetSignatureForError ());
2602                 }
2603         }
2604
2605         /// <summary>
2606         ///   Expression that evaluates to a type
2607         /// </summary>
2608         public abstract class TypeExpr : FullNamedExpression
2609         {
2610                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2611                 {
2612                         ResolveAsType (mc);
2613                         return this;
2614                 }
2615
2616                 protected sealed override Expression DoResolve (ResolveContext ec)
2617                 {
2618                         ResolveAsType (ec);
2619                         return this;
2620                 }
2621
2622                 public override bool Equals (object obj)
2623                 {
2624                         TypeExpr tobj = obj as TypeExpr;
2625                         if (tobj == null)
2626                                 return false;
2627
2628                         return Type == tobj.Type;
2629                 }
2630
2631                 public override int GetHashCode ()
2632                 {
2633                         return Type.GetHashCode ();
2634                 }
2635         }
2636
2637         /// <summary>
2638         ///   Fully resolved Expression that already evaluated to a type
2639         /// </summary>
2640         public class TypeExpression : TypeExpr
2641         {
2642                 public TypeExpression (TypeSpec t, Location l)
2643                 {
2644                         Type = t;
2645                         eclass = ExprClass.Type;
2646                         loc = l;
2647                 }
2648
2649                 public sealed override TypeSpec ResolveAsType (IMemberContext ec)
2650                 {
2651                         return type;
2652                 }
2653         }
2654
2655         /// <summary>
2656         ///   This class denotes an expression which evaluates to a member
2657         ///   of a struct or a class.
2658         /// </summary>
2659         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
2660         {
2661                 //
2662                 // An instance expression associated with this member, if it's a
2663                 // non-static member
2664                 //
2665                 public Expression InstanceExpression;
2666
2667                 /// <summary>
2668                 ///   The name of this member.
2669                 /// </summary>
2670                 public abstract string Name {
2671                         get;
2672                 }
2673
2674                 //
2675                 // When base.member is used
2676                 //
2677                 public bool IsBase {
2678                         get { return InstanceExpression is BaseThis; }
2679                 }
2680
2681                 /// <summary>
2682                 ///   Whether this is an instance member.
2683                 /// </summary>
2684                 public abstract bool IsInstance {
2685                         get;
2686                 }
2687
2688                 /// <summary>
2689                 ///   Whether this is a static member.
2690                 /// </summary>
2691                 public abstract bool IsStatic {
2692                         get;
2693                 }
2694
2695                 protected abstract TypeSpec DeclaringType {
2696                         get;
2697                 }
2698
2699                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
2700                         get {
2701                                 return InstanceExpression.Type;
2702                         }
2703                 }
2704
2705                 //
2706                 // Converts best base candidate for virtual method starting from QueriedBaseType
2707                 //
2708                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
2709                 {
2710                         //
2711                         // Only when base.member is used and method is virtual
2712                         //
2713                         if (!IsBase)
2714                                 return method;
2715
2716                         //
2717                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
2718                         // means for base.member access we have to find the closest match after we found best candidate
2719                         //
2720                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
2721                                 //
2722                                 // The method could already be what we are looking for
2723                                 //
2724                                 TypeSpec[] targs = null;
2725                                 if (method.DeclaringType != InstanceExpression.Type) {
2726                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, new MemberFilter (method), BindingRestriction.InstanceOnly) as MethodSpec;
2727                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
2728                                                 if (base_override.IsGeneric)
2729                                                         targs = method.TypeArguments;
2730
2731                                                 method = base_override;
2732                                         }
2733                                 }
2734
2735                                 // TODO: For now we do it for any hoisted call even if it's needed for
2736                                 // hoisted stories only but that requires a new expression wrapper
2737                                 if (rc.CurrentAnonymousMethod != null) {
2738                                         if (targs == null && method.IsGeneric) {
2739                                                 targs = method.TypeArguments;
2740                                                 method = method.GetGenericMethodDefinition ();
2741                                         }
2742
2743                                         if (method.Parameters.HasArglist)
2744                                                 throw new NotImplementedException ("__arglist base call proxy");
2745
2746                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
2747
2748                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
2749                                         // get/set member expressions second call would fail to proxy because left expression
2750                                         // would be of 'this' and not 'base'
2751                                         if (rc.CurrentType.IsStruct)
2752                                                 InstanceExpression = new This (loc).Resolve (rc);
2753                                 }
2754
2755                                 if (targs != null)
2756                                         method = method.MakeGenericMethod (rc, targs);
2757                         }
2758
2759                         //
2760                         // Only base will allow this invocation to happen.
2761                         //
2762                         if (method.IsAbstract) {
2763                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
2764                         }
2765
2766                         return method;
2767                 }
2768
2769                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
2770                 {
2771                         if (InstanceExpression == null)
2772                                 return;
2773
2774                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
2775                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
2776                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
2777                                 }
2778                         }
2779                 }
2780
2781                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
2782                 {
2783                         if (InstanceExpression == null)
2784                                 return true;
2785
2786                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
2787                 }
2788
2789                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
2790                 {
2791                         var ct = rc.CurrentType;
2792                         if (ct == qualifier)
2793                                 return true;
2794
2795                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
2796                                 return true;
2797
2798                         qualifier = qualifier.GetDefinition ();
2799                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
2800                                 return false;
2801                         }
2802
2803                         return true;
2804                 }
2805
2806                 public override bool ContainsEmitWithAwait ()
2807                 {
2808                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
2809                 }
2810
2811                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
2812                 {
2813                         do {
2814                                 type = type.GetDefinition ();
2815
2816                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
2817                                         return true;
2818
2819                                 type = type.DeclaringType;
2820                         } while (type != null);
2821
2822                         return false;
2823                 }
2824
2825                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
2826                 {
2827                         if (InstanceExpression != null) {
2828                                 InstanceExpression = InstanceExpression.Resolve (rc);
2829                                 CheckProtectedMemberAccess (rc, member);
2830                         }
2831
2832                         if (member.MemberType.IsPointer && !rc.IsUnsafe) {
2833                                 UnsafeError (rc, loc);
2834                         }
2835
2836                         var dep = member.GetMissingDependencies ();
2837                         if (dep != null) {
2838                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
2839                         }
2840
2841                         if (!rc.IsObsolete) {
2842                                 ObsoleteAttribute oa = member.GetAttributeObsolete ();
2843                                 if (oa != null)
2844                                         AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
2845                         }
2846
2847                         if (!(member is FieldSpec))
2848                                 member.MemberDefinition.SetIsUsed ();
2849                 }
2850
2851                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
2852                 {
2853                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
2854                 }
2855
2856                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
2857                 {
2858                         rc.Report.SymbolRelatedToPreviousError (member);
2859                         rc.Report.Error (1540, loc,
2860                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
2861                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
2862                 }
2863
2864                 //
2865                 // Implements identicial simple name and type-name
2866                 //
2867                 public Expression ProbeIdenticalTypeName (ResolveContext rc, Expression left, SimpleName name)
2868                 {
2869                         var t = left.Type;
2870                         if (t.Kind == MemberKind.InternalCompilerType || t is ElementTypeSpec || t.Arity > 0)
2871                                 return left;
2872
2873                         // 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
2874                         // a constant, field, property, local variable, or parameter with the same type as the meaning of E as a type-name
2875
2876                         if (left is MemberExpr || left is VariableReference) {
2877                                 var identical_type = rc.LookupNamespaceOrType (name.Name, 0, LookupMode.Probing, loc) as TypeExpr;
2878                                 if (identical_type != null && identical_type.Type == left.Type)
2879                                         return identical_type;
2880                         }
2881
2882                         return left;
2883                 }
2884
2885                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
2886                 {
2887                         if (IsStatic) {
2888                                 if (InstanceExpression != null) {
2889                                         if (InstanceExpression is TypeExpr) {
2890                                                 var t = InstanceExpression.Type;
2891                                                 do {
2892                                                         ObsoleteAttribute oa = t.GetAttributeObsolete ();
2893                                                         if (oa != null && !rc.IsObsolete) {
2894                                                                 AttributeTester.Report_ObsoleteMessage (oa, t.GetSignatureForError (), loc, rc.Report);
2895                                                         }
2896
2897                                                         t = t.DeclaringType;
2898                                                 } while (t != null);
2899                                         } else {
2900                                                 var runtime_expr = InstanceExpression as RuntimeValueExpression;
2901                                                 if (runtime_expr == null || !runtime_expr.IsSuggestionOnly) {
2902                                                         rc.Report.Error (176, loc,
2903                                                                 "Static member `{0}' cannot be accessed with an instance reference, qualify it with a type name instead",
2904                                                                 GetSignatureForError ());
2905                                                 }
2906                                         }
2907
2908                                         InstanceExpression = null;
2909                                 }
2910
2911                                 return false;
2912                         }
2913
2914                         if (InstanceExpression == null || InstanceExpression is TypeExpr) {
2915                                 if (InstanceExpression != null || !This.IsThisAvailable (rc, true)) {
2916                                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope))
2917                                                 rc.Report.Error (236, loc,
2918                                                         "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
2919                                                         GetSignatureForError ());
2920                                         else
2921                                                 rc.Report.Error (120, loc,
2922                                                         "An object reference is required to access non-static member `{0}'",
2923                                                         GetSignatureForError ());
2924
2925                                         InstanceExpression = new CompilerGeneratedThis (type, loc).Resolve (rc);
2926                                         return false;
2927                                 }
2928
2929                                 if (!TypeManager.IsFamilyAccessible (rc.CurrentType, DeclaringType)) {
2930                                         rc.Report.Error (38, loc,
2931                                                 "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
2932                                                 DeclaringType.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
2933                                 }
2934
2935                                 InstanceExpression = new This (loc);
2936                                 if (this is FieldExpr && rc.CurrentBlock.ParametersBlock.TopBlock.ThisVariable != null) {
2937                                         using (rc.Set (ResolveContext.Options.OmitStructFlowAnalysis)) {
2938                                                 InstanceExpression = InstanceExpression.Resolve (rc);
2939                                         }
2940                                 } else {
2941                                         InstanceExpression = InstanceExpression.Resolve (rc);
2942                                 }
2943
2944                                 return false;
2945                         }
2946
2947                         var me = InstanceExpression as MemberExpr;
2948                         if (me != null) {
2949                                 me.ResolveInstanceExpression (rc, rhs);
2950
2951                                 var fe = me as FieldExpr;
2952                                 if (fe != null && fe.IsMarshalByRefAccess (rc)) {
2953                                         rc.Report.SymbolRelatedToPreviousError (me.DeclaringType);
2954                                         rc.Report.Warning (1690, 1, loc,
2955                                                 "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
2956                                                 me.GetSignatureForError ());
2957                                 }
2958
2959                                 return true;
2960                         }
2961
2962                         //
2963                         // Run member-access postponed check once we know that
2964                         // the expression is not field expression which is the only
2965                         // expression which can use uninitialized this
2966                         //
2967                         if (InstanceExpression is This && !(this is FieldExpr) && rc.CurrentBlock.ParametersBlock.TopBlock.ThisVariable != null) {
2968                                 ((This)InstanceExpression).CheckStructThisDefiniteAssignment (rc);
2969                         }
2970
2971                         //
2972                         // Additional checks for l-value member access
2973                         //
2974                         if (rhs != null) {
2975                                 if (InstanceExpression is UnboxCast) {
2976                                         rc.Report.Error (445, InstanceExpression.Location, "Cannot modify the result of an unboxing conversion");
2977                                 }
2978                         }
2979
2980                         return true;
2981                 }
2982
2983                 public virtual MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
2984                 {
2985                         if (left != null && left.IsNull && TypeSpec.IsReferenceType (left.Type)) {
2986                                 ec.Report.Warning (1720, 1, left.Location,
2987                                         "Expression will always cause a `{0}'", "System.NullReferenceException");
2988                         }
2989
2990                         InstanceExpression = left;
2991                         return this;
2992                 }
2993
2994                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
2995                 {
2996                         TypeSpec instance_type = InstanceExpression.Type;
2997                         if (TypeSpec.IsValueType (instance_type)) {
2998                                 if (InstanceExpression is IMemoryLocation) {
2999                                         ((IMemoryLocation) InstanceExpression).AddressOf (ec, AddressOp.Load);
3000                                 } else {
3001                                         // Cannot release the temporary variable when its address
3002                                         // is required to be on stack for any parent
3003                                         LocalTemporary t = new LocalTemporary (instance_type);
3004                                         InstanceExpression.Emit (ec);
3005                                         t.Store (ec);
3006                                         t.AddressOf (ec, AddressOp.Store);
3007                                 }
3008                         } else {
3009                                 InstanceExpression.Emit (ec);
3010
3011                                 // Only to make verifier happy
3012                                 if (instance_type.IsGenericParameter && !(InstanceExpression is This) && TypeSpec.IsReferenceType (instance_type))
3013                                         ec.Emit (OpCodes.Box, instance_type);
3014                         }
3015
3016                         if (prepare_for_load)
3017                                 ec.Emit (OpCodes.Dup);
3018                 }
3019
3020                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3021         }
3022
3023         public class ExtensionMethodCandidates
3024         {
3025                 NamespaceContainer container;
3026                 Namespace ns;
3027                 IList<MethodSpec> methods;
3028
3029                 public ExtensionMethodCandidates (IList<MethodSpec> methods, NamespaceContainer nsContainer)
3030                         : this (methods, nsContainer, null)
3031                 {
3032                 }
3033
3034                 public ExtensionMethodCandidates (IList<MethodSpec> methods, NamespaceContainer nsContainer, Namespace ns)
3035                 {
3036                         this.methods = methods;
3037                         this.container = nsContainer;
3038                         this.ns = ns;
3039                 }
3040
3041                 public NamespaceContainer Container {
3042                         get {
3043                                 return container;
3044                         }
3045                 }
3046
3047                 public bool HasUninspectedMembers { get; set; }
3048
3049                 public Namespace Namespace {
3050                         get {
3051                                 return ns;
3052                         }
3053                 }
3054
3055                 public IList<MethodSpec> Methods {
3056                         get {
3057                                 return methods;
3058                         }
3059                 }
3060         }
3061
3062         //
3063         // Represents a group of extension method candidates for whole namespace
3064         //
3065         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3066         {
3067                 ExtensionMethodCandidates candidates;
3068                 public readonly Expression ExtensionExpression;
3069
3070                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3071                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3072                 {
3073                         this.candidates = candidates;
3074                         this.ExtensionExpression = extensionExpr;
3075                 }
3076
3077                 public override bool IsStatic {
3078                         get { return true; }
3079                 }
3080
3081                 //
3082                 // For extension methodgroup we are not looking for base members but parent
3083                 // namespace extension methods
3084                 //
3085                 public override IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3086                 {
3087                         // TODO: candidates are null only when doing error reporting, that's
3088                         // incorrect. We have to discover same extension methods in error mode
3089                         if (candidates == null)
3090                                 return null;
3091
3092                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3093
3094                         //
3095                         // Here we try to resume the search for extension method at the point
3096                         // where the last bunch of candidates was found. It's more tricky than
3097                         // it seems as we have to check both namespace containers and namespace
3098                         // in correct order.
3099                         //
3100                         // Consider:
3101                         //
3102                         // namespace A {
3103                         //      using N1;
3104                         //  namespace B.C.D {
3105                         //              <our first search found candidates in A.B.C.D
3106                         //  }
3107                         // }
3108                         //
3109                         // In the example above namespace A.B.C.D, A.B.C and A.B have to be
3110                         // checked before we hit A.N1 using
3111                         //
3112                         if (candidates.Namespace == null) {
3113                                 Namespace scope;
3114                                 var methods = candidates.Container.NS.LookupExtensionMethod (candidates.Container, ExtensionExpression.Type, Name, arity, out scope);
3115                                 if (methods != null) {
3116                                         candidates = new ExtensionMethodCandidates (null, candidates.Container, scope);
3117                                         return methods.Cast<MemberSpec> ().ToList ();
3118                                 }
3119                         }
3120
3121                         var ns_container = candidates.HasUninspectedMembers ? candidates.Container : candidates.Container.Parent;
3122                         if (ns_container == null)
3123                                 return null;
3124
3125                         candidates = ns_container.LookupExtensionMethod (ExtensionExpression.Type, Name, arity);
3126                         if (candidates == null)
3127                                 return null;
3128
3129                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3130                 }
3131
3132                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3133                 {
3134                         // We are already here
3135                         return null;
3136                 }
3137
3138                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3139                 {
3140                         if (arguments == null)
3141                                 arguments = new Arguments (1);
3142
3143                         arguments.Insert (0, new Argument (ExtensionExpression, Argument.AType.ExtensionType));
3144                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3145
3146                         // Store resolved argument and restore original arguments
3147                         if (res == null) {
3148                                 // Clean-up modified arguments for error reporting
3149                                 arguments.RemoveAt (0);
3150                                 return null;
3151                         }
3152
3153                         var me = ExtensionExpression as MemberExpr;
3154                         if (me != null)
3155                                 me.ResolveInstanceExpression (ec, null);
3156
3157                         InstanceExpression = null;
3158                         return this;
3159                 }
3160
3161                 #region IErrorHandler Members
3162
3163                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3164                 {
3165                         return false;
3166                 }
3167
3168                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3169                 {
3170                         rc.Report.SymbolRelatedToPreviousError (best);
3171                         rc.Report.Error (1928, loc,
3172                                 "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3173                                 queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3174
3175                         if (index == 0) {
3176                                 rc.Report.Error (1929, loc,
3177                                         "Extension method instance type `{0}' cannot be converted to `{1}'",
3178                                         arg.Type.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3179                         }
3180
3181                         return true;
3182                 }
3183
3184                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3185                 {
3186                         return false;
3187                 }
3188
3189                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3190                 {
3191                         return false;
3192                 }
3193
3194                 #endregion
3195         }
3196
3197         /// <summary>
3198         ///   MethodGroupExpr represents a group of method candidates which
3199         ///   can be resolved to the best method overload
3200         /// </summary>
3201         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3202         {
3203                 protected IList<MemberSpec> Methods;
3204                 MethodSpec best_candidate;
3205                 TypeSpec best_candidate_return;
3206                 protected TypeArguments type_arguments;
3207
3208                 SimpleName simple_name;
3209                 protected TypeSpec queried_type;
3210
3211                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3212                 {
3213                         Methods = mi;
3214                         this.loc = loc;
3215                         this.type = InternalType.MethodGroup;
3216
3217                         eclass = ExprClass.MethodGroup;
3218                         queried_type = type;
3219                 }
3220
3221                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3222                         : this (new MemberSpec[] { m }, type, loc)
3223                 {
3224                 }
3225
3226                 #region Properties
3227
3228                 public MethodSpec BestCandidate {
3229                         get {
3230                                 return best_candidate;
3231                         }
3232                 }
3233
3234                 public TypeSpec BestCandidateReturnType {
3235                         get {
3236                                 return best_candidate_return;
3237                         }
3238                 }
3239
3240                 public IList<MemberSpec> Candidates {
3241                         get {
3242                                 return Methods;
3243                         }
3244                 }
3245
3246                 protected override TypeSpec DeclaringType {
3247                         get {
3248                                 return queried_type;
3249                         }
3250                 }
3251
3252                 public override bool IsInstance {
3253                         get {
3254                                 if (best_candidate != null)
3255                                         return !best_candidate.IsStatic;
3256
3257                                 return false;
3258                         }
3259                 }
3260
3261                 public override bool IsStatic {
3262                         get {
3263                                 if (best_candidate != null)
3264                                         return best_candidate.IsStatic;
3265
3266                                 return false;
3267                         }
3268                 }
3269
3270                 public override string Name {
3271                         get {
3272                                 if (best_candidate != null)
3273                                         return best_candidate.Name;
3274
3275                                 // TODO: throw ?
3276                                 return Methods.First ().Name;
3277                         }
3278                 }
3279
3280                 #endregion
3281
3282                 //
3283                 // When best candidate is already know this factory can be used
3284                 // to avoid expensive overload resolution to be called
3285                 //
3286                 // NOTE: InstanceExpression has to be set manually
3287                 //
3288                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3289                 {
3290                         return new MethodGroupExpr (best, queriedType, loc) {
3291                                 best_candidate = best,
3292                                 best_candidate_return = best.ReturnType
3293                         };
3294                 }
3295
3296                 public override string GetSignatureForError ()
3297                 {
3298                         if (best_candidate != null)
3299                                 return best_candidate.GetSignatureForError ();
3300
3301                         return Methods.First ().GetSignatureForError ();
3302                 }
3303
3304                 public override Expression CreateExpressionTree (ResolveContext ec)
3305                 {
3306                         if (best_candidate == null) {
3307                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3308                                 return null;
3309                         }
3310
3311                         if (best_candidate.IsConditionallyExcluded (ec.Module.Compiler, loc))
3312                                 ec.Report.Error (765, loc,
3313                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3314
3315                         return new TypeOfMethod (best_candidate, loc);
3316                 }
3317
3318                 protected override Expression DoResolve (ResolveContext ec)
3319                 {
3320                         this.eclass = ExprClass.MethodGroup;
3321
3322                         if (InstanceExpression != null) {
3323                                 InstanceExpression = InstanceExpression.Resolve (ec);
3324                                 if (InstanceExpression == null)
3325                                         return null;
3326                         }
3327
3328                         return this;
3329                 }
3330
3331                 public override void Emit (EmitContext ec)
3332                 {
3333                         throw new NotSupportedException ();
3334                 }
3335
3336                 public void EmitCall (EmitContext ec, Arguments arguments)
3337                 {
3338                         var call = new CallEmitter ();
3339                         call.InstanceExpression = InstanceExpression;
3340                         call.Emit (ec, best_candidate, arguments, loc);
3341                 }
3342
3343                 public override void Error_ValueCannotBeConverted (ResolveContext ec, Location loc, TypeSpec target, bool expl)
3344                 {
3345                         ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
3346                                 Name, TypeManager.CSharpName (target));
3347                 }
3348
3349                 public static bool IsExtensionMethodArgument (Expression expr)
3350                 {
3351                         //
3352                         // LAMESPEC: No details about which expressions are not allowed
3353                         //
3354                         return !(expr is TypeExpr) && !(expr is BaseThis);
3355                 }
3356
3357                 /// <summary>
3358                 ///   Find the Applicable Function Members (7.4.2.1)
3359                 ///
3360                 ///   me: Method Group expression with the members to select.
3361                 ///       it might contain constructors or methods (or anything
3362                 ///       that maps to a method).
3363                 ///
3364                 ///   Arguments: ArrayList containing resolved Argument objects.
3365                 ///
3366                 ///   loc: The location if we want an error to be reported, or a Null
3367                 ///        location for "probing" purposes.
3368                 ///
3369                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
3370                 ///            that is the best match of me on Arguments.
3371                 ///
3372                 /// </summary>
3373                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
3374                 {
3375                         // TODO: causes issues with probing mode, remove explicit Kind check
3376                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
3377                                 return this;
3378
3379                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
3380                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
3381                                 r.BaseMembersProvider = this;
3382                                 r.InstanceQualifier = this;
3383                         }
3384
3385                         if (cerrors != null)
3386                                 r.CustomErrors = cerrors;
3387
3388                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
3389                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
3390                         if (best_candidate == null)
3391                                 return r.BestCandidateIsDynamic ? this : null;
3392
3393                         // Overload resolver had to create a new method group, all checks bellow have already been executed
3394                         if (r.BestCandidateNewMethodGroup != null)
3395                                 return r.BestCandidateNewMethodGroup;
3396
3397                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
3398                                 if (InstanceExpression != null) {
3399                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
3400                                                 InstanceExpression = null;
3401                                         } else {
3402                                                 if (best_candidate.IsStatic && simple_name != null) {
3403                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
3404                                                 }
3405
3406                                                 InstanceExpression.Resolve (ec);
3407                                         }
3408                                 }
3409
3410                                 ResolveInstanceExpression (ec, null);
3411                         }
3412
3413                         var base_override = CandidateToBaseOverride (ec, best_candidate);
3414                         if (base_override == best_candidate) {
3415                                 best_candidate_return = r.BestCandidateReturnType;
3416                         } else {
3417                                 best_candidate = base_override;
3418                                 best_candidate_return = best_candidate.ReturnType;
3419                         }
3420
3421                         return this;
3422                 }
3423
3424                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3425                 {
3426                         simple_name = original;
3427                         return base.ResolveMemberAccess (ec, left, original);
3428                 }
3429
3430                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
3431                 {
3432                         type_arguments = ta;
3433                 }
3434
3435                 #region IBaseMembersProvider Members
3436
3437                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3438                 {
3439                         return baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
3440                 }
3441
3442                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3443                 {
3444                         if (queried_type == member.DeclaringType)
3445                                 return null;
3446
3447                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
3448                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
3449                 }
3450
3451                 //
3452                 // Extension methods lookup after ordinary methods candidates failed to apply
3453                 //
3454                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3455                 {
3456                         if (InstanceExpression == null)
3457                                 return null;
3458
3459                         InstanceExpression = InstanceExpression.Resolve (rc);
3460                         if (!IsExtensionMethodArgument (InstanceExpression))
3461                                 return null;
3462
3463                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3464                         var methods = rc.LookupExtensionMethod (InstanceExpression.Type, Methods[0].Name, arity);
3465                         if (methods == null)
3466                                 return null;
3467
3468                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
3469                         emg.SetTypeArguments (rc, type_arguments);
3470                         return emg;
3471                 }
3472
3473                 #endregion
3474         }
3475
3476         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
3477         {
3478                 public ConstructorInstanceQualifier (TypeSpec type)
3479                         : this ()
3480                 {
3481                         InstanceType = type;
3482                 }
3483
3484                 public TypeSpec InstanceType { get; private set; }
3485
3486                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3487                 {
3488                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
3489                 }
3490         }
3491
3492         public struct OverloadResolver
3493         {
3494                 [Flags]
3495                 public enum Restrictions
3496                 {
3497                         None = 0,
3498                         DelegateInvoke = 1,
3499                         ProbingOnly     = 1 << 1,
3500                         CovariantDelegate = 1 << 2,
3501                         NoBaseMembers = 1 << 3,
3502                         BaseMembersIncluded = 1 << 4
3503                 }
3504
3505                 public interface IBaseMembersProvider
3506                 {
3507                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
3508                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
3509                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
3510                 }
3511
3512                 public interface IErrorHandler
3513                 {
3514                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
3515                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
3516                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
3517                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
3518                 }
3519
3520                 public interface IInstanceQualifier
3521                 {
3522                         TypeSpec InstanceType { get; }
3523                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
3524                 }
3525
3526                 sealed class NoBaseMembers : IBaseMembersProvider
3527                 {
3528                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
3529
3530                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3531                         {
3532                                 return null;
3533                         }
3534
3535                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3536                         {
3537                                 return null;
3538                         }
3539
3540                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3541                         {
3542                                 return null;
3543                         }
3544                 }
3545
3546                 struct AmbiguousCandidate
3547                 {
3548                         public readonly MemberSpec Member;
3549                         public readonly bool Expanded;
3550                         public readonly AParametersCollection Parameters;
3551
3552                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
3553                         {
3554                                 Member = member;
3555                                 Parameters = parameters;
3556                                 Expanded = expanded;
3557                         }
3558                 }
3559
3560                 Location loc;
3561                 IList<MemberSpec> members;
3562                 TypeArguments type_arguments;
3563                 IBaseMembersProvider base_provider;
3564                 IErrorHandler custom_errors;
3565                 IInstanceQualifier instance_qualifier;
3566                 Restrictions restrictions;
3567                 MethodGroupExpr best_candidate_extension_group;
3568                 TypeSpec best_candidate_return_type;
3569
3570                 SessionReportPrinter lambda_conv_msgs;
3571                 ReportPrinter prev_recorder;
3572
3573                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
3574                         : this (members, null, restrictions, loc)
3575                 {
3576                 }
3577
3578                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
3579                         : this ()
3580                 {
3581                         if (members == null || members.Count == 0)
3582                                 throw new ArgumentException ("empty members set");
3583
3584                         this.members = members;
3585                         this.loc = loc;
3586                         type_arguments = targs;
3587                         this.restrictions = restrictions;
3588                         if (IsDelegateInvoke)
3589                                 this.restrictions |= Restrictions.NoBaseMembers;
3590
3591                         base_provider = NoBaseMembers.Instance;
3592                 }
3593
3594                 #region Properties
3595
3596                 public IBaseMembersProvider BaseMembersProvider {
3597                         get {
3598                                 return base_provider;
3599                         }
3600                         set {
3601                                 base_provider = value;
3602                         }
3603                 }
3604
3605                 public bool BestCandidateIsDynamic { get; set; }
3606
3607                 //
3608                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
3609                 //
3610                 public MethodGroupExpr BestCandidateNewMethodGroup {
3611                         get {
3612                                 return best_candidate_extension_group;
3613                         }
3614                 }
3615
3616                 //
3617                 // Return type can be different between best candidate and closest override
3618                 //
3619                 public TypeSpec BestCandidateReturnType {
3620                         get {
3621                                 return best_candidate_return_type;
3622                         }
3623                 }
3624
3625                 public IErrorHandler CustomErrors {
3626                         get {
3627                                 return custom_errors;
3628                         }
3629                         set {
3630                                 custom_errors = value;
3631                         }
3632                 }
3633
3634                 TypeSpec DelegateType {
3635                         get {
3636                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
3637                                         throw new InternalErrorException ("Not running in delegate mode", loc);
3638
3639                                 return members [0].DeclaringType;
3640                         }
3641                 }
3642
3643                 public IInstanceQualifier InstanceQualifier {
3644                         get {
3645                                 return instance_qualifier;
3646                         }
3647                         set {
3648                                 instance_qualifier = value;
3649                         }
3650                 }
3651
3652                 bool IsProbingOnly {
3653                         get {
3654                                 return (restrictions & Restrictions.ProbingOnly) != 0;
3655                         }
3656                 }
3657
3658                 bool IsDelegateInvoke {
3659                         get {
3660                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
3661                         }
3662                 }
3663
3664                 #endregion
3665
3666                 //
3667                 //  7.4.3.3  Better conversion from expression
3668                 //  Returns :   1    if a->p is better,
3669                 //              2    if a->q is better,
3670                 //              0 if neither is better
3671                 //
3672                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
3673                 {
3674                         TypeSpec argument_type = a.Type;
3675
3676                         //
3677                         // If argument is an anonymous function
3678                         //
3679                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
3680                                 //
3681                                 // p and q are delegate types or expression tree types
3682                                 //
3683                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
3684                                         if (q.MemberDefinition != p.MemberDefinition) {
3685                                                 return 0;
3686                                         }
3687
3688                                         //
3689                                         // Uwrap delegate from Expression<T>
3690                                         //
3691                                         q = TypeManager.GetTypeArguments (q)[0];
3692                                         p = TypeManager.GetTypeArguments (p)[0];
3693                                 }
3694
3695                                 var p_m = Delegate.GetInvokeMethod (p);
3696                                 var q_m = Delegate.GetInvokeMethod (q);
3697
3698                                 //
3699                                 // With identical parameter lists
3700                                 //
3701                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
3702                                         return 0;
3703
3704                                 p = p_m.ReturnType;
3705                                 q = q_m.ReturnType;
3706
3707                                 //
3708                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
3709                                 //
3710                                 if (p.Kind == MemberKind.Void) {
3711                                         return q.Kind != MemberKind.Void ? 2 : 0;
3712                                 }
3713
3714                                 //
3715                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
3716                                 //
3717                                 if (q.Kind == MemberKind.Void) {
3718                                         return p.Kind != MemberKind.Void ? 1: 0;
3719                                 }
3720
3721                                 //
3722                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
3723                                 // better conversion is performed between underlying types Y1 and Y2
3724                                 //
3725                                 if (p.IsGenericTask || q.IsGenericTask) {
3726                                         var async_am = a.Expr as AnonymousMethodExpression;
3727                                         if (async_am != null && async_am.Block.IsAsync) {
3728
3729                                                 if (p.IsGenericTask != q.IsGenericTask) {
3730                                                         return 0;
3731                                                 }
3732
3733                                                 q = q.TypeArguments[0];
3734                                                 p = p.TypeArguments[0];
3735                                         }
3736                                 }
3737
3738                                 //
3739                                 // The parameters are identicial and return type is not void, use better type conversion
3740                                 // on return type to determine better one
3741                                 //
3742                         } else {
3743                                 if (argument_type == p)
3744                                         return 1;
3745
3746                                 if (argument_type == q)
3747                                         return 2;
3748                         }
3749
3750                         return BetterTypeConversion (ec, p, q);
3751                 }
3752
3753                 //
3754                 // 7.4.3.4  Better conversion from type
3755                 //
3756                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
3757                 {
3758                         if (p == null || q == null)
3759                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
3760
3761                         switch (p.BuiltinType) {
3762                         case BuiltinTypeSpec.Type.Int:
3763                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
3764                                         return 1;
3765                                 break;
3766                         case BuiltinTypeSpec.Type.Long:
3767                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
3768                                         return 1;
3769                                 break;
3770                         case BuiltinTypeSpec.Type.SByte:
3771                                 switch (q.BuiltinType) {
3772                                 case BuiltinTypeSpec.Type.Byte:
3773                                 case BuiltinTypeSpec.Type.UShort:
3774                                 case BuiltinTypeSpec.Type.UInt:
3775                                 case BuiltinTypeSpec.Type.ULong:
3776                                         return 1;
3777                                 }
3778                                 break;
3779                         case BuiltinTypeSpec.Type.Short:
3780                                 switch (q.BuiltinType) {
3781                                 case BuiltinTypeSpec.Type.UShort:
3782                                 case BuiltinTypeSpec.Type.UInt:
3783                                 case BuiltinTypeSpec.Type.ULong:
3784                                         return 1;
3785                                 }
3786                                 break;
3787                         case BuiltinTypeSpec.Type.Dynamic:
3788                                 // Dynamic is never better
3789                                 return 2;
3790                         }
3791
3792                         switch (q.BuiltinType) {
3793                         case BuiltinTypeSpec.Type.Int:
3794                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
3795                                         return 2;
3796                                 break;
3797                         case BuiltinTypeSpec.Type.Long:
3798                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
3799                                         return 2;
3800                                 break;
3801                         case BuiltinTypeSpec.Type.SByte:
3802                                 switch (p.BuiltinType) {
3803                                 case BuiltinTypeSpec.Type.Byte:
3804                                 case BuiltinTypeSpec.Type.UShort:
3805                                 case BuiltinTypeSpec.Type.UInt:
3806                                 case BuiltinTypeSpec.Type.ULong:
3807                                         return 2;
3808                                 }
3809                                 break;
3810                         case BuiltinTypeSpec.Type.Short:
3811                                 switch (p.BuiltinType) {
3812                                 case BuiltinTypeSpec.Type.UShort:
3813                                 case BuiltinTypeSpec.Type.UInt:
3814                                 case BuiltinTypeSpec.Type.ULong:
3815                                         return 2;
3816                                 }
3817                                 break;
3818                         case BuiltinTypeSpec.Type.Dynamic:
3819                                 // Dynamic is never better
3820                                 return 1;
3821                         }
3822
3823                         // FIXME: handle lifted operators
3824
3825                         // TODO: this is expensive
3826                         Expression p_tmp = new EmptyExpression (p);
3827                         Expression q_tmp = new EmptyExpression (q);
3828
3829                         bool p_to_q = Convert.ImplicitConversionExists (ec, p_tmp, q);
3830                         bool q_to_p = Convert.ImplicitConversionExists (ec, q_tmp, p);
3831
3832                         if (p_to_q && !q_to_p)
3833                                 return 1;
3834
3835                         if (q_to_p && !p_to_q)
3836                                 return 2;
3837
3838                         return 0;
3839                 }
3840
3841                 /// <summary>
3842                 ///   Determines "Better function" between candidate
3843                 ///   and the current best match
3844                 /// </summary>
3845                 /// <remarks>
3846                 ///    Returns a boolean indicating :
3847                 ///     false if candidate ain't better
3848                 ///     true  if candidate is better than the current best match
3849                 /// </remarks>
3850                 static bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
3851                         MemberSpec best, AParametersCollection bparam, bool best_params)
3852                 {
3853                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
3854                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
3855
3856                         bool better_at_least_one = false;
3857                         bool same = true;
3858                         int args_count = args == null ? 0 : args.Count;
3859                         int j = 0;
3860                         Argument a = null;
3861                         TypeSpec ct, bt;
3862                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
3863                                 a = args[j];
3864
3865                                 // Default arguments are ignored for better decision
3866                                 if (a.IsDefaultArgument)
3867                                         break;
3868
3869                                 //
3870                                 // When comparing named argument the parameter type index has to be looked up
3871                                 // in original parameter set (override version for virtual members)
3872                                 //
3873                                 NamedArgument na = a as NamedArgument;
3874                                 if (na != null) {
3875                                         int idx = cparam.GetParameterIndexByName (na.Name);
3876                                         ct = candidate_pd.Types[idx];
3877                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
3878                                                 ct = TypeManager.GetElementType (ct);
3879
3880                                         idx = bparam.GetParameterIndexByName (na.Name);
3881                                         bt = best_pd.Types[idx];
3882                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
3883                                                 bt = TypeManager.GetElementType (bt);
3884                                 } else {
3885                                         ct = candidate_pd.Types[c_idx];
3886                                         bt = best_pd.Types[b_idx];
3887
3888                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
3889                                                 ct = TypeManager.GetElementType (ct);
3890                                                 --c_idx;
3891                                         }
3892
3893                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
3894                                                 bt = TypeManager.GetElementType (bt);
3895                                                 --b_idx;
3896                                         }
3897                                 }
3898
3899                                 if (TypeSpecComparer.IsEqual (ct, bt))
3900                                         continue;
3901
3902                                 same = false;
3903                                 int result = BetterExpressionConversion (ec, a, ct, bt);
3904
3905                                 // for each argument, the conversion to 'ct' should be no worse than
3906                                 // the conversion to 'bt'.
3907                                 if (result == 2)
3908                                         return false;
3909
3910                                 // for at least one argument, the conversion to 'ct' should be better than
3911                                 // the conversion to 'bt'.
3912                                 if (result != 0)
3913                                         better_at_least_one = true;
3914                         }
3915
3916                         if (better_at_least_one)
3917                                 return true;
3918
3919                         //
3920                         // This handles the case
3921                         //
3922                         //   Add (float f1, float f2, float f3);
3923                         //   Add (params decimal [] foo);
3924                         //
3925                         // The call Add (3, 4, 5) should be ambiguous.  Without this check, the
3926                         // first candidate would've chosen as better.
3927                         //
3928                         if (!same && !a.IsDefaultArgument)
3929                                 return false;
3930
3931                         //
3932                         // The two methods have equal non-optional parameter types, apply tie-breaking rules
3933                         //
3934
3935                         //
3936                         // This handles the following cases:
3937                         //
3938                         //  Foo (int i) is better than Foo (int i, long l = 0)
3939                         //  Foo (params int[] args) is better than Foo (int i = 0, params int[] args)
3940                         //
3941                         // Prefer non-optional version
3942                         //
3943                         // LAMESPEC: Specification claims this should be done at last but the opposite is true
3944                         //
3945                         if (candidate_params == best_params && candidate_pd.Count != best_pd.Count) {
3946                                 if (candidate_pd.Count >= best_pd.Count)
3947                                         return false;
3948
3949                                 if (j < candidate_pd.Count && candidate_pd.FixedParameters[j].HasDefaultValue)
3950                                         return false;
3951
3952                                 return true;
3953                         }
3954
3955                         //
3956                         // One is a non-generic method and second is a generic method, then non-generic is better
3957                         //
3958                         if (best.IsGeneric != candidate.IsGeneric)
3959                                 return best.IsGeneric;
3960
3961                         //
3962                         // This handles the following cases:
3963                         //
3964                         //   Trim () is better than Trim (params char[] chars)
3965                         //   Concat (string s1, string s2, string s3) is better than
3966                         //     Concat (string s1, params string [] srest)
3967                         //   Foo (int, params int [] rest) is better than Foo (params int [] rest)
3968                         //
3969                         // Prefer non-expanded version
3970                         //
3971                         if (candidate_params != best_params)
3972                                 return best_params;
3973
3974                         int candidate_param_count = candidate_pd.Count;
3975                         int best_param_count = best_pd.Count;
3976
3977                         if (candidate_param_count != best_param_count)
3978                                 // can only happen if (candidate_params && best_params)
3979                                 return candidate_param_count > best_param_count && best_pd.HasParams;
3980
3981                         //
3982                         // Both methods have the same number of parameters, and the parameters have equal types
3983                         // Pick the "more specific" signature using rules over original (non-inflated) types
3984                         //
3985                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
3986                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
3987
3988                         bool specific_at_least_once = false;
3989                         for (j = 0; j < args_count; ++j) {
3990                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
3991                                 if (na != null) {
3992                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
3993                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
3994                                 } else {
3995                                         ct = candidate_def_pd.Types[j];
3996                                         bt = best_def_pd.Types[j];
3997                                 }
3998
3999                                 if (ct == bt)
4000                                         continue;
4001                                 TypeSpec specific = MoreSpecific (ct, bt);
4002                                 if (specific == bt)
4003                                         return false;
4004                                 if (specific == ct)
4005                                         specific_at_least_once = true;
4006                         }
4007
4008                         if (specific_at_least_once)
4009                                 return true;
4010
4011                         return false;
4012                 }
4013
4014                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4015                 {
4016                         rc.Report.Error (1729, loc,
4017                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4018                                 type.GetSignatureForError (), argCount.ToString ());
4019                 }
4020
4021                 //
4022                 // Determines if the candidate method is applicable to the given set of arguments
4023                 // There could be two different set of parameters for same candidate where one
4024                 // is the closest override for default values and named arguments checks and second
4025                 // one being the virtual base for the parameter types and modifiers.
4026                 //
4027                 // A return value rates candidate method compatibility,
4028                 // 0 = the best, int.MaxValue = the worst
4029                 //
4030                 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)
4031                 {
4032                         // Parameters of most-derived type used mainly for named and optional parameters
4033                         var pd = pm.Parameters;
4034
4035                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4036                         // params modifier instead of most-derived type
4037                         var cpd = ((IParametersMember) candidate).Parameters;
4038                         int param_count = pd.Count;
4039                         int optional_count = 0;
4040                         int score;
4041                         Arguments orig_args = arguments;
4042
4043                         if (arg_count != param_count) {
4044                                 for (int i = 0; i < pd.Count; ++i) {
4045                                         if (pd.FixedParameters[i].HasDefaultValue) {
4046                                                 optional_count = pd.Count - i;
4047                                                 break;
4048                                         }
4049                                 }
4050
4051                                 if (optional_count != 0) {
4052                                         // Readjust expected number when params used
4053                                         if (cpd.HasParams) {
4054                                                 optional_count--;
4055                                                 if (arg_count < param_count)
4056                                                         param_count--;
4057                                         } else if (arg_count > param_count) {
4058                                                 int args_gap = System.Math.Abs (arg_count - param_count);
4059                                                 return int.MaxValue - 10000 + args_gap;
4060                                         }
4061                                 } else if (arg_count != param_count) {
4062                                         int args_gap = System.Math.Abs (arg_count - param_count);
4063                                         if (!cpd.HasParams)
4064                                                 return int.MaxValue - 10000 + args_gap;
4065                                         if (arg_count < param_count - 1)
4066                                                 return int.MaxValue - 10000 + args_gap;
4067                                 }
4068
4069                                 // Resize to fit optional arguments
4070                                 if (optional_count != 0) {
4071                                         if (arguments == null) {
4072                                                 arguments = new Arguments (optional_count);
4073                                         } else {
4074                                                 // Have to create a new container, so the next run can do same
4075                                                 var resized = new Arguments (param_count);
4076                                                 resized.AddRange (arguments);
4077                                                 arguments = resized;
4078                                         }
4079
4080                                         for (int i = arg_count; i < param_count; ++i)
4081                                                 arguments.Add (null);
4082                                 }
4083                         }
4084
4085                         if (arg_count > 0) {
4086                                 //
4087                                 // Shuffle named arguments to the right positions if there are any
4088                                 //
4089                                 if (arguments[arg_count - 1] is NamedArgument) {
4090                                         arg_count = arguments.Count;
4091
4092                                         for (int i = 0; i < arg_count; ++i) {
4093                                                 bool arg_moved = false;
4094                                                 while (true) {
4095                                                         NamedArgument na = arguments[i] as NamedArgument;
4096                                                         if (na == null)
4097                                                                 break;
4098
4099                                                         int index = pd.GetParameterIndexByName (na.Name);
4100
4101                                                         // Named parameter not found
4102                                                         if (index < 0)
4103                                                                 return (i + 1) * 3;
4104
4105                                                         // already reordered
4106                                                         if (index == i)
4107                                                                 break;
4108
4109                                                         Argument temp;
4110                                                         if (index >= param_count) {
4111                                                                 // When using parameters which should not be available to the user
4112                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
4113                                                                         break;
4114
4115                                                                 arguments.Add (null);
4116                                                                 ++arg_count;
4117                                                                 temp = null;
4118                                                         } else {
4119                                                                 temp = arguments[index];
4120
4121                                                                 // The slot has been taken by positional argument
4122                                                                 if (temp != null && !(temp is NamedArgument))
4123                                                                         break;
4124                                                         }
4125
4126                                                         if (!arg_moved) {
4127                                                                 arguments = arguments.MarkOrderedArgument (na);
4128                                                                 arg_moved = true;
4129                                                         }
4130
4131                                                         arguments[index] = arguments[i];
4132                                                         arguments[i] = temp;
4133
4134                                                         if (temp == null)
4135                                                                 break;
4136                                                 }
4137                                         }
4138                                 } else {
4139                                         arg_count = arguments.Count;
4140                                 }
4141                         } else if (arguments != null) {
4142                                 arg_count = arguments.Count;
4143                         }
4144
4145                         //
4146                         // 1. Handle generic method using type arguments when specified or type inference
4147                         //
4148                         TypeSpec[] ptypes;
4149                         var ms = candidate as MethodSpec;
4150                         if (ms != null && ms.IsGeneric) {
4151                                 // Setup constraint checker for probing only
4152                                 ConstraintChecker cc = new ConstraintChecker (null);
4153
4154                                 if (type_arguments != null) {
4155                                         var g_args_count = ms.Arity;
4156                                         if (g_args_count != type_arguments.Count)
4157                                                 return int.MaxValue - 20000 + System.Math.Abs (type_arguments.Count - g_args_count);
4158
4159                                         ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
4160                                 } else {
4161                                         // TODO: It should not be here (we don't know yet whether any argument is lambda) but
4162                                         // for now it simplifies things. I should probably add a callback to ResolveContext
4163                                         if (lambda_conv_msgs == null) {
4164                                                 lambda_conv_msgs = new SessionReportPrinter ();
4165                                                 prev_recorder = ec.Report.SetPrinter (lambda_conv_msgs);
4166                                         }
4167
4168                                         var ti = new TypeInference (arguments);
4169                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
4170                                         lambda_conv_msgs.EndSession ();
4171
4172                                         if (i_args == null)
4173                                                 return ti.InferenceScore - 20000;
4174
4175                                         if (i_args.Length != 0) {
4176                                                 ms = ms.MakeGenericMethod (ec, i_args);
4177                                         }
4178
4179                                         cc.IgnoreInferredDynamic = true;
4180                                 }
4181
4182                                 //
4183                                 // Type arguments constraints have to match for the method to be applicable
4184                                 //
4185                                 if (!cc.CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc)) {
4186                                         candidate = ms;
4187                                         return int.MaxValue - 25000;
4188                                 }
4189
4190                                 //
4191                                 // We have a generic return type and at same time the method is override which
4192                                 // means we have to also inflate override return type in case the candidate is
4193                                 // best candidate and override return type is different to base return type.
4194                                 //
4195                                 // virtual Foo<T, object> with override Foo<T, dynamic>
4196                                 //
4197                                 if (candidate != pm) {
4198                                         MethodSpec override_ms = (MethodSpec) pm;
4199                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
4200                                         returnType = inflator.Inflate (returnType);
4201                                 } else {
4202                                         returnType = ms.ReturnType;
4203                                 }
4204
4205                                 candidate = ms;
4206                                 ptypes = ms.Parameters.Types;
4207                         } else {
4208                                 if (type_arguments != null)
4209                                         return int.MaxValue - 15000;
4210
4211                                 ptypes = cpd.Types;
4212                         }
4213
4214                         //
4215                         // 2. Each argument has to be implicitly convertible to method parameter
4216                         //
4217                         Parameter.Modifier p_mod = 0;
4218                         TypeSpec pt = null;
4219
4220                         for (int i = 0; i < arg_count; i++) {
4221                                 Argument a = arguments[i];
4222                                 if (a == null) {
4223                                         if (!pd.FixedParameters[i].HasDefaultValue) {
4224                                                 arguments = orig_args;
4225                                                 return arg_count * 2 + 2;
4226                                         }
4227
4228                                         //
4229                                         // Get the default value expression, we can use the same expression
4230                                         // if the type matches
4231                                         //
4232                                         Expression e = pd.FixedParameters[i].DefaultValue;
4233                                         if (!(e is Constant) || e.Type.IsGenericOrParentIsGeneric || e.Type.IsGenericParameter) {
4234                                                 //
4235                                                 // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
4236                                                 //
4237                                                 if (e == EmptyExpression.MissingValue && ptypes[i].BuiltinType == BuiltinTypeSpec.Type.Object || ptypes[i].BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
4238                                                         e = new MemberAccess (new MemberAccess (new MemberAccess (
4239                                                                 new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
4240                                                 } else {
4241                                                         e = new DefaultValueExpression (new TypeExpression (ptypes [i], loc), loc);
4242                                                 }
4243
4244                                                 e = e.Resolve (ec);
4245                                         }
4246
4247                                         arguments[i] = new Argument (e, Argument.AType.Default);
4248                                         continue;
4249                                 }
4250
4251                                 if (p_mod != Parameter.Modifier.PARAMS) {
4252                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
4253                                         pt = ptypes [i];
4254                                 } else if (!params_expanded_form) {
4255                                         params_expanded_form = true;
4256                                         pt = ((ElementTypeSpec) pt).Element;
4257                                         i -= 2;
4258                                         continue;
4259                                 }
4260
4261                                 score = 1;
4262                                 if (!params_expanded_form) {
4263                                         if (a.ArgType == Argument.AType.ExtensionType) {
4264                                                 //
4265                                                 // Indentity, implicit reference or boxing conversion must exist for the extension parameter
4266                                                 //
4267                                                 // LAMESPEC: or implicit type parameter conversion
4268                                                 //
4269                                                 var at = a.Type;
4270                                                 if (at == pt || TypeSpecComparer.IsEqual (at, pt) ||
4271                                                         Convert.ImplicitReferenceConversionExists (at, pt, false) ||
4272                                                         Convert.ImplicitBoxingConversion (null, at, pt) != null) {
4273                                                         score = 0;
4274                                                         continue;
4275                                                 }
4276                                         } else {
4277                                                 score = IsArgumentCompatible (ec, a, p_mod & ~Parameter.Modifier.PARAMS, pt);
4278
4279                                                 if (score < 0)
4280                                                         dynamicArgument = true;
4281                                         }
4282                                 }
4283
4284                                 //
4285                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
4286                                 //
4287                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
4288                                         if (!params_expanded_form)
4289                                                 pt = ((ElementTypeSpec) pt).Element;
4290
4291                                         if (score > 0)
4292                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
4293
4294                                         if (score == 0) {
4295                                                 params_expanded_form = true;
4296                                         } else if (score < 0) {
4297                                                 params_expanded_form = true;
4298                                                 dynamicArgument = true;
4299                                         }
4300                                 }
4301
4302                                 if (score > 0) {
4303                                         if (params_expanded_form)
4304                                                 ++score;
4305                                         return (arg_count - i) * 2 + score;
4306                                 }
4307                         }
4308
4309                         //
4310                         // When params parameter has no argument it will be provided later if the method is the best candidate
4311                         //
4312                         if (arg_count + 1 == pd.Count && (cpd.FixedParameters [arg_count].ModFlags & Parameter.Modifier.PARAMS) != 0)
4313                                 params_expanded_form = true;
4314
4315                         //
4316                         // Restore original arguments for dynamic binder to keep the intention of original source code
4317                         //
4318                         if (dynamicArgument)
4319                                 arguments = orig_args;
4320
4321                         return 0;
4322                 }
4323
4324                 //
4325                 // Tests argument compatibility with the parameter
4326                 // The possible return values are
4327                 // 0 - success
4328                 // 1 - modifier mismatch
4329                 // 2 - type mismatch
4330                 // -1 - dynamic binding required
4331                 //
4332                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
4333                 {
4334                         //
4335                         // Types have to be identical when ref or out modifer
4336                         // is used and argument is not of dynamic type
4337                         //
4338                         if ((argument.Modifier | param_mod) != 0) {
4339                                 if (argument.Type != parameter) {
4340                                         //
4341                                         // Do full equality check after quick path
4342                                         //
4343                                         if (!TypeSpecComparer.IsEqual (argument.Type, parameter)) {
4344                                                 //
4345                                                 // Using dynamic for ref/out parameter can still succeed at runtime
4346                                                 //
4347                                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && argument.Modifier == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4348                                                         return -1;
4349
4350                                                 return 2;
4351                                         }
4352                                 }
4353
4354                                 if (argument.Modifier != param_mod) {
4355                                         //
4356                                         // Using dynamic for ref/out parameter can still succeed at runtime
4357                                         //
4358                                         if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && argument.Modifier == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4359                                                 return -1;
4360
4361                                         return 1;
4362                                 }
4363
4364                         } else {
4365                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
4366                                         return -1;
4367
4368                                 //
4369                                 // Deploy custom error reporting for lambda methods. When probing lambda methods
4370                                 // keep all errors reported in separate set and once we are done and no best
4371                                 // candidate was found, this set is used to report more details about what was wrong
4372                                 // with lambda body
4373                                 //
4374                                 if (argument.Expr.Type == InternalType.AnonymousMethod) {
4375                                         if (lambda_conv_msgs == null) {
4376                                                 lambda_conv_msgs = new SessionReportPrinter ();
4377                                                 prev_recorder = ec.Report.SetPrinter (lambda_conv_msgs);
4378                                         }
4379                                 }
4380
4381                                 //
4382                                 // Use implicit conversion in all modes to return same candidates when the expression
4383                                 // is used as argument or delegate conversion
4384                                 //
4385                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
4386                                         if (lambda_conv_msgs != null) {
4387                                                 lambda_conv_msgs.EndSession ();
4388                                         }
4389
4390                                         return 2;
4391                                 }
4392                         }
4393
4394                         return 0;
4395                 }
4396
4397                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
4398                 {
4399                         if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
4400                                 return q;
4401                         if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
4402                                 return p;
4403
4404                         var ac_p = p as ArrayContainer;
4405                         if (ac_p != null) {
4406                                 var ac_q = ((ArrayContainer) q);
4407                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
4408                                 if (specific == ac_p.Element)
4409                                         return p;
4410                                 if (specific == ac_q.Element)
4411                                         return q;
4412                         } else if (TypeManager.IsGenericType (p)) {
4413                                 var pargs = TypeManager.GetTypeArguments (p);
4414                                 var qargs = TypeManager.GetTypeArguments (q);
4415
4416                                 bool p_specific_at_least_once = false;
4417                                 bool q_specific_at_least_once = false;
4418
4419                                 for (int i = 0; i < pargs.Length; i++) {
4420                                         TypeSpec specific = MoreSpecific (pargs[i], qargs[i]);
4421                                         if (specific == pargs[i])
4422                                                 p_specific_at_least_once = true;
4423                                         if (specific == qargs[i])
4424                                                 q_specific_at_least_once = true;
4425                                 }
4426
4427                                 if (p_specific_at_least_once && !q_specific_at_least_once)
4428                                         return p;
4429                                 if (!p_specific_at_least_once && q_specific_at_least_once)
4430                                         return q;
4431                         }
4432
4433                         return null;
4434                 }
4435
4436                 //
4437                 // Find the best method from candidate list
4438                 //
4439                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
4440                 {
4441                         List<AmbiguousCandidate> ambiguous_candidates = null;
4442
4443                         MemberSpec best_candidate;
4444                         Arguments best_candidate_args = null;
4445                         bool best_candidate_params = false;
4446                         bool best_candidate_dynamic = false;
4447                         int best_candidate_rate;
4448                         IParametersMember best_parameter_member = null;
4449
4450                         int args_count = args != null ? args.Count : 0;
4451
4452                         Arguments candidate_args = args;
4453                         bool error_mode = false;
4454                         MemberSpec invocable_member = null;
4455
4456                         // Be careful, cannot return until error reporter is restored
4457                         while (true) {
4458                                 best_candidate = null;
4459                                 best_candidate_rate = int.MaxValue;
4460
4461                                 var type_members = members;
4462                                 try {
4463
4464                                         do {
4465                                                 for (int i = 0; i < type_members.Count; ++i) {
4466                                                         var member = type_members[i];
4467
4468                                                         //
4469                                                         // Methods in a base class are not candidates if any method in a derived
4470                                                         // class is applicable
4471                                                         //
4472                                                         if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
4473                                                                 continue;
4474
4475                                                         if (!error_mode) {
4476                                                                 if (!member.IsAccessible (rc))
4477                                                                         continue;
4478
4479                                                                 if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
4480                                                                         continue;
4481
4482                                                                 if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
4483                                                                         instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
4484                                                                         continue;
4485                                                                 }
4486                                                         }
4487
4488                                                         IParametersMember pm = member as IParametersMember;
4489                                                         if (pm == null) {
4490                                                                 //
4491                                                                 // Will use it later to report ambiguity between best method and invocable member
4492                                                                 //
4493                                                                 if (Invocation.IsMemberInvocable (member))
4494                                                                         invocable_member = member;
4495
4496                                                                 continue;
4497                                                         }
4498
4499                                                         //
4500                                                         // Overload resolution is looking for base member but using parameter names
4501                                                         // and default values from the closest member. That means to do expensive lookup
4502                                                         // for the closest override for virtual or abstract members
4503                                                         //
4504                                                         if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
4505                                                                 var override_params = base_provider.GetOverrideMemberParameters (member);
4506                                                                 if (override_params != null)
4507                                                                         pm = override_params;
4508                                                         }
4509
4510                                                         //
4511                                                         // Check if the member candidate is applicable
4512                                                         //
4513                                                         bool params_expanded_form = false;
4514                                                         bool dynamic_argument = false;
4515                                                         TypeSpec rt = pm.MemberType;
4516                                                         int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt);
4517
4518                                                         //
4519                                                         // How does it score compare to others
4520                                                         //
4521                                                         if (candidate_rate < best_candidate_rate) {
4522                                                                 best_candidate_rate = candidate_rate;
4523                                                                 best_candidate = member;
4524                                                                 best_candidate_args = candidate_args;
4525                                                                 best_candidate_params = params_expanded_form;
4526                                                                 best_candidate_dynamic = dynamic_argument;
4527                                                                 best_parameter_member = pm;
4528                                                                 best_candidate_return_type = rt;
4529                                                         } else if (candidate_rate == 0) {
4530                                                                 //
4531                                                                 // The member look is done per type for most operations but sometimes
4532                                                                 // it's not possible like for binary operators overload because they
4533                                                                 // are unioned between 2 sides
4534                                                                 //
4535                                                                 if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
4536                                                                         if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
4537                                                                                 continue;
4538                                                                 }
4539
4540                                                                 bool is_better;
4541                                                                 if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
4542                                                                         //
4543                                                                         // We pack all interface members into top level type which makes the overload resolution
4544                                                                         // more complicated for interfaces. We compensate it by removing methods with same
4545                                                                         // signature when building the cache hence this path should not really be hit often
4546                                                                         //
4547                                                                         // Example:
4548                                                                         // interface IA { void Foo (int arg); }
4549                                                                         // interface IB : IA { void Foo (params int[] args); }
4550                                                                         //
4551                                                                         // IB::Foo is the best overload when calling IB.Foo (1)
4552                                                                         //
4553                                                                         is_better = true;
4554                                                                         if (ambiguous_candidates != null) {
4555                                                                                 foreach (var amb_cand in ambiguous_candidates) {
4556                                                                                         if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
4557                                                                                                 continue;
4558                                                                                         }
4559
4560                                                                                         is_better = false;
4561                                                                                         break;
4562                                                                                 }
4563
4564                                                                                 if (is_better)
4565                                                                                         ambiguous_candidates = null;
4566                                                                         }
4567                                                                 } else {
4568                                                                         // Is the new candidate better
4569                                                                         is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
4570                                                                 }
4571
4572                                                                 if (is_better) {
4573                                                                         best_candidate = member;
4574                                                                         best_candidate_args = candidate_args;
4575                                                                         best_candidate_params = params_expanded_form;
4576                                                                         best_candidate_dynamic = dynamic_argument;
4577                                                                         best_parameter_member = pm;
4578                                                                         best_candidate_return_type = rt;
4579                                                                 } else {
4580                                                                         // It's not better but any other found later could be but we are not sure yet
4581                                                                         if (ambiguous_candidates == null)
4582                                                                                 ambiguous_candidates = new List<AmbiguousCandidate> ();
4583
4584                                                                         ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
4585                                                                 }
4586                                                         }
4587
4588                                                         // Restore expanded arguments
4589                                                         if (candidate_args != args)
4590                                                                 candidate_args = args;
4591                                                 }
4592                                         } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType.BaseType)) != null);
4593                                 } finally {
4594                                         if (prev_recorder != null)
4595                                                 rc.Report.SetPrinter (prev_recorder);
4596                                 }
4597
4598                                 //
4599                                 // We've found exact match
4600                                 //
4601                                 if (best_candidate_rate == 0)
4602                                         break;
4603
4604                                 //
4605                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
4606                                 //
4607                                 if (!error_mode) {
4608                                         var emg = base_provider.LookupExtensionMethod (rc);
4609                                         if (emg != null) {
4610                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
4611                                                 if (emg != null) {
4612                                                         best_candidate_extension_group = emg;
4613                                                         return (T) (MemberSpec) emg.BestCandidate;
4614                                                 }
4615                                         }
4616                                 }
4617
4618                                 // Don't run expensive error reporting mode for probing
4619                                 if (IsProbingOnly)
4620                                         return null;
4621
4622                                 if (error_mode)
4623                                         break;
4624
4625                                 lambda_conv_msgs = null;
4626                                 error_mode = true;
4627                         }
4628
4629                         //
4630                         // No best member match found, report an error
4631                         //
4632                         if (best_candidate_rate != 0 || error_mode) {
4633                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
4634                                 return null;
4635                         }
4636
4637                         if (best_candidate_dynamic) {
4638                                 if (args[0].ArgType == Argument.AType.ExtensionType) {
4639                                         rc.Report.Error (1973, loc,
4640                                                 "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",
4641                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
4642                                 }
4643
4644                                 BestCandidateIsDynamic = true;
4645                                 return null;
4646                         }
4647
4648                         //
4649                         // These flags indicates we are running delegate probing conversion. No need to
4650                         // do more expensive checks
4651                         //
4652                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
4653                                 return (T) best_candidate;
4654
4655                         if (ambiguous_candidates != null) {
4656                                 //
4657                                 // Now check that there are no ambiguities i.e the selected method
4658                                 // should be better than all the others
4659                                 //
4660                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
4661                                         var candidate = ambiguous_candidates [ix];
4662
4663                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
4664                                                 var ambiguous = candidate.Member;
4665                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
4666                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
4667                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
4668                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
4669                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
4670                                                 }
4671
4672                                                 return (T) best_candidate;
4673                                         }
4674                                 }
4675                         }
4676
4677                         if (invocable_member != null) {
4678                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4679                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
4680                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
4681                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
4682                         }
4683
4684                         //
4685                         // And now check if the arguments are all
4686                         // compatible, perform conversions if
4687                         // necessary etc. and return if everything is
4688                         // all right
4689                         //
4690                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
4691                                 return null;
4692
4693                         if (best_candidate == null)
4694                                 return null;
4695
4696                         //
4697                         // Check ObsoleteAttribute on the best method
4698                         //
4699                         ObsoleteAttribute oa = best_candidate.GetAttributeObsolete ();
4700                         if (oa != null && !rc.IsObsolete)
4701                                 AttributeTester.Report_ObsoleteMessage (oa, best_candidate.GetSignatureForError (), loc, rc.Report);
4702
4703                         var dep = best_candidate.GetMissingDependencies ();
4704                         if (dep != null) {
4705                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
4706                         }
4707
4708                         best_candidate.MemberDefinition.SetIsUsed ();
4709
4710                         args = best_candidate_args;
4711                         return (T) best_candidate;
4712                 }
4713
4714                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
4715                 {
4716                         return ResolveMember<MethodSpec> (rc, ref args);
4717                 }
4718
4719                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
4720                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
4721                 {
4722                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
4723                                 return;
4724
4725                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
4726                                 ec.Report.SymbolRelatedToPreviousError (method);
4727                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.ISBYREF) != 0) {
4728                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have 'ref', or `out' modifier",
4729                                                 TypeManager.CSharpSignature (method));
4730                                         return;
4731                                 }
4732                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
4733                                           TypeManager.CSharpSignature (method));
4734                         } else if (IsDelegateInvoke) {
4735                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
4736                                         DelegateType.GetSignatureForError ());
4737                         } else {
4738                                 ec.Report.SymbolRelatedToPreviousError (method);
4739                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
4740                                         method.GetSignatureForError ());
4741                         }
4742
4743                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
4744
4745                         string index = (idx + 1).ToString ();
4746                         if (((mod & (Parameter.Modifier.REF | Parameter.Modifier.OUT)) ^
4747                                 (a.Modifier & (Parameter.Modifier.REF | Parameter.Modifier.OUT))) != 0) {
4748                                 if ((mod & Parameter.Modifier.ISBYREF) == 0)
4749                                         ec.Report.Error (1615, loc, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
4750                                                 index, Parameter.GetModifierSignature (a.Modifier));
4751                                 else
4752                                         ec.Report.Error (1620, loc, "Argument `#{0}' is missing `{1}' modifier",
4753                                                 index, Parameter.GetModifierSignature (mod));
4754                         } else if (a.Expr != ErrorExpression.Instance) {
4755                                 string p1 = a.GetSignatureForError ();
4756                                 string p2 = TypeManager.CSharpName (paramType);
4757
4758                                 if (p1 == p2) {
4759                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
4760                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
4761                                 }
4762
4763                                 ec.Report.Error (1503, loc,
4764                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
4765                         }
4766                 }
4767
4768                 //
4769                 // We have failed to find exact match so we return error info about the closest match
4770                 //
4771                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
4772                 {
4773                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
4774                         int arg_count = args == null ? 0 : args.Count;
4775
4776                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
4777                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
4778                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, ta_count, loc);
4779                                 return;
4780                         }
4781
4782                         if (lambda_conv_msgs != null) {
4783                                 if (lambda_conv_msgs.Merge (rc.Report.Printer))
4784                                         return;
4785                         }
4786
4787
4788                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
4789                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
4790                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
4791                         }
4792
4793                         //
4794                         // For candidates which match on parameters count report more details about incorrect arguments
4795                         //
4796                         if (pm != null) {
4797                                 int unexpanded_count = ((IParametersMember) best_candidate).Parameters.HasParams ? pm.Parameters.Count - 1 : pm.Parameters.Count;
4798                                 if (pm.Parameters.Count == arg_count || params_expanded || unexpanded_count == arg_count) {
4799                                         // Reject any inaccessible member
4800                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
4801                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4802                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
4803                                                 return;
4804                                         }
4805
4806                                         var ms = best_candidate as MethodSpec;
4807                                         if (ms != null && ms.IsGeneric) {
4808                                                 bool constr_ok = true;
4809                                                 if (ms.TypeArguments != null)
4810                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
4811
4812                                                 if (ta_count == 0) {
4813                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
4814                                                                 return;
4815
4816                                                         if (constr_ok) {
4817                                                                 rc.Report.Error (411, loc,
4818                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
4819                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
4820                                                         }
4821
4822                                                         return;
4823                                                 }
4824                                         }
4825
4826                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
4827                                         return;
4828                                 }
4829                         }
4830
4831                         //
4832                         // We failed to find any method with correct argument count, report best candidate
4833                         //
4834                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
4835                                 return;
4836
4837                         if (best_candidate.Kind == MemberKind.Constructor) {
4838                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4839                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
4840                         } else if (IsDelegateInvoke) {
4841                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
4842                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
4843                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
4844                         } else {
4845                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
4846                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
4847                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
4848                                         name, arg_count.ToString ());
4849                         }
4850                 }
4851
4852                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
4853                 {
4854                         var pd = pm.Parameters;
4855                         TypeSpec[] ptypes = ((IParametersMember) member).Parameters.Types;
4856
4857                         Parameter.Modifier p_mod = 0;
4858                         TypeSpec pt = null;
4859                         int a_idx = 0, a_pos = 0;
4860                         Argument a = null;
4861                         ArrayInitializer params_initializers = null;
4862                         bool has_unsafe_arg = pm.MemberType.IsPointer;
4863                         int arg_count = args == null ? 0 : args.Count;
4864
4865                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
4866                                 a = args[a_idx];
4867                                 if (p_mod != Parameter.Modifier.PARAMS) {
4868                                         p_mod = pd.FixedParameters[a_idx].ModFlags;
4869                                         pt = ptypes[a_idx];
4870                                         has_unsafe_arg |= pt.IsPointer;
4871
4872                                         if (p_mod == Parameter.Modifier.PARAMS) {
4873                                                 if (chose_params_expanded) {
4874                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
4875                                                         pt = TypeManager.GetElementType (pt);
4876                                                 }
4877                                         }
4878                                 }
4879
4880                                 //
4881                                 // Types have to be identical when ref or out modifer is used
4882                                 //
4883                                 if (a.Modifier != 0 || (p_mod & ~Parameter.Modifier.PARAMS) != 0) {
4884                                         if ((p_mod & ~Parameter.Modifier.PARAMS) != a.Modifier)
4885                                                 break;
4886
4887                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt))
4888                                                 continue;
4889
4890                                         break;
4891                                 }
4892
4893                                 NamedArgument na = a as NamedArgument;
4894                                 if (na != null) {
4895                                         int name_index = pd.GetParameterIndexByName (na.Name);
4896                                         if (name_index < 0 || name_index >= pd.Count) {
4897                                                 if (IsDelegateInvoke) {
4898                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
4899                                                         ec.Report.Error (1746, na.Location,
4900                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
4901                                                                 DelegateType.GetSignatureForError (), na.Name);
4902                                                 } else {
4903                                                         ec.Report.SymbolRelatedToPreviousError (member);
4904                                                         ec.Report.Error (1739, na.Location,
4905                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
4906                                                                 TypeManager.CSharpSignature (member), na.Name);
4907                                                 }
4908                                         } else if (args[name_index] != a) {
4909                                                 if (IsDelegateInvoke)
4910                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
4911                                                 else
4912                                                         ec.Report.SymbolRelatedToPreviousError (member);
4913
4914                                                 ec.Report.Error (1744, na.Location,
4915                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
4916                                                         na.Name);
4917                                         }
4918                                 }
4919
4920                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4921                                         continue;
4922
4923                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
4924                                         custom_errors.NoArgumentMatch (ec, member);
4925                                         return false;
4926                                 }
4927
4928                                 Expression conv = null;
4929                                 if (a.ArgType == Argument.AType.ExtensionType) {
4930                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
4931                                                 conv = a.Expr;
4932                                         } else {
4933                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
4934                                                 if (conv == null)
4935                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
4936                                         }
4937                                 } else {
4938                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
4939                                 }
4940
4941                                 if (conv == null)
4942                                         break;
4943
4944                                 //
4945                                 // Convert params arguments to an array initializer
4946                                 //
4947                                 if (params_initializers != null) {
4948                                         // we choose to use 'a.Expr' rather than 'conv' so that
4949                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
4950                                         params_initializers.Add (a.Expr);
4951                                         args.RemoveAt (a_idx--);
4952                                         --arg_count;
4953                                         continue;
4954                                 }
4955
4956                                 // Update the argument with the implicit conversion
4957                                 a.Expr = conv;
4958                         }
4959
4960                         if (a_idx != arg_count) {
4961                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
4962                                 return false;
4963                         }
4964
4965                         //
4966                         // Fill not provided arguments required by params modifier
4967                         //
4968                         if (params_initializers == null && pd.HasParams && arg_count + 1 == pd.Count) {
4969                                 if (args == null)
4970                                         args = new Arguments (1);
4971
4972                                 pt = ptypes[pd.Count - 1];
4973                                 pt = TypeManager.GetElementType (pt);
4974                                 has_unsafe_arg |= pt.IsPointer;
4975                                 params_initializers = new ArrayInitializer (0, loc);
4976                         }
4977
4978                         //
4979                         // Append an array argument with all params arguments
4980                         //
4981                         if (params_initializers != null) {
4982                                 args.Add (new Argument (
4983                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
4984                                 arg_count++;
4985                         }
4986
4987                         if (has_unsafe_arg && !ec.IsUnsafe) {
4988                                 Expression.UnsafeError (ec, loc);
4989                         }
4990
4991                         //
4992                         // We could infer inaccesible type arguments
4993                         //
4994                         if (type_arguments == null && member.IsGeneric) {
4995                                 var ms = (MethodSpec) member;
4996                                 foreach (var ta in ms.TypeArguments) {
4997                                         if (!ta.IsAccessible (ec)) {
4998                                                 ec.Report.SymbolRelatedToPreviousError (ta);
4999                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
5000                                                 break;
5001                                         }
5002                                 }
5003                         }
5004
5005                         return true;
5006                 }
5007         }
5008
5009         public class ConstantExpr : MemberExpr
5010         {
5011                 readonly ConstSpec constant;
5012
5013                 public ConstantExpr (ConstSpec constant, Location loc)
5014                 {
5015                         this.constant = constant;
5016                         this.loc = loc;
5017                 }
5018
5019                 public override string Name {
5020                         get { throw new NotImplementedException (); }
5021                 }
5022
5023                 public override bool IsInstance {
5024                         get { return !IsStatic; }
5025                 }
5026
5027                 public override bool IsStatic {
5028                         get { return true; }
5029                 }
5030
5031                 protected override TypeSpec DeclaringType {
5032                         get { return constant.DeclaringType; }
5033                 }
5034
5035                 public override Expression CreateExpressionTree (ResolveContext ec)
5036                 {
5037                         throw new NotSupportedException ("ET");
5038                 }
5039
5040                 protected override Expression DoResolve (ResolveContext rc)
5041                 {
5042                         ResolveInstanceExpression (rc, null);
5043                         DoBestMemberChecks (rc, constant);
5044
5045                         var c = constant.GetConstant (rc);
5046
5047                         // Creates reference expression to the constant value
5048                         return Constant.CreateConstant (constant.MemberType, c.GetValue (), loc);
5049                 }
5050
5051                 public override void Emit (EmitContext ec)
5052                 {
5053                         throw new NotSupportedException ();
5054                 }
5055
5056                 public override string GetSignatureForError ()
5057                 {
5058                         return constant.GetSignatureForError ();
5059                 }
5060
5061                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5062                 {
5063                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
5064                 }
5065         }
5066
5067         //
5068         // Fully resolved expression that references a Field
5069         //
5070         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
5071         {
5072                 protected FieldSpec spec;
5073                 VariableInfo variable_info;
5074
5075                 LocalTemporary temp;
5076                 bool prepared;
5077
5078                 protected FieldExpr (Location l)
5079                 {
5080                         loc = l;
5081                 }
5082
5083                 public FieldExpr (FieldSpec spec, Location loc)
5084                 {
5085                         this.spec = spec;
5086                         this.loc = loc;
5087
5088                         type = spec.MemberType;
5089                 }
5090
5091                 public FieldExpr (FieldBase fi, Location l)
5092                         : this (fi.Spec, l)
5093                 {
5094                 }
5095
5096                 #region Properties
5097
5098                 public override string Name {
5099                         get {
5100                                 return spec.Name;
5101                         }
5102                 }
5103
5104                 public bool IsHoisted {
5105                         get {
5106                                 IVariableReference hv = InstanceExpression as IVariableReference;
5107                                 return hv != null && hv.IsHoisted;
5108                         }
5109                 }
5110
5111                 public override bool IsInstance {
5112                         get {
5113                                 return !spec.IsStatic;
5114                         }
5115                 }
5116
5117                 public override bool IsStatic {
5118                         get {
5119                                 return spec.IsStatic;
5120                         }
5121                 }
5122
5123                 public FieldSpec Spec {
5124                         get {
5125                                 return spec;
5126                         }
5127                 }
5128
5129                 protected override TypeSpec DeclaringType {
5130                         get {
5131                                 return spec.DeclaringType;
5132                         }
5133                 }
5134
5135                 public VariableInfo VariableInfo {
5136                         get {
5137                                 return variable_info;
5138                         }
5139                 }
5140
5141 #endregion
5142
5143                 public override string GetSignatureForError ()
5144                 {
5145                         return spec.GetSignatureForError ();
5146                 }
5147
5148                 public bool IsMarshalByRefAccess (ResolveContext rc)
5149                 {
5150                         // Checks possible ldflda of field access expression
5151                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
5152                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
5153                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
5154                 }
5155
5156                 public void SetHasAddressTaken ()
5157                 {
5158                         IVariableReference vr = InstanceExpression as IVariableReference;
5159                         if (vr != null) {
5160                                 vr.SetHasAddressTaken ();
5161                         }
5162                 }
5163
5164                 public override Expression CreateExpressionTree (ResolveContext ec)
5165                 {
5166                         Expression instance;
5167                         if (InstanceExpression == null) {
5168                                 instance = new NullLiteral (loc);
5169                         } else {
5170                                 instance = InstanceExpression.CreateExpressionTree (ec);
5171                         }
5172
5173                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
5174                                 instance,
5175                                 CreateTypeOfExpression ());
5176
5177                         return CreateExpressionFactoryCall (ec, "Field", args);
5178                 }
5179
5180                 public Expression CreateTypeOfExpression ()
5181                 {
5182                         return new TypeOfField (spec, loc);
5183                 }
5184
5185                 protected override Expression DoResolve (ResolveContext ec)
5186                 {
5187                         return DoResolve (ec, null);
5188                 }
5189
5190                 Expression DoResolve (ResolveContext ec, Expression rhs)
5191                 {
5192                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
5193
5194                         if (rhs != this) {
5195                                 if (ResolveInstanceExpression (ec, rhs)) {
5196                                         // Resolve the field's instance expression while flow analysis is turned
5197                                         // off: when accessing a field "a.b", we must check whether the field
5198                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
5199
5200                                         if (lvalue_instance) {
5201                                                 using (ec.With (ResolveContext.Options.DoFlowAnalysis, false)) {
5202                                                         bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
5203
5204                                                         Expression right_side =
5205                                                                 out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
5206
5207                                                         InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
5208                                                 }
5209                                         } else {
5210                                                 using (ec.With (ResolveContext.Options.DoFlowAnalysis, false)) {
5211                                                         InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
5212                                                 }
5213                                         }
5214
5215                                         if (InstanceExpression == null)
5216                                                 return null;
5217                                 }
5218
5219                                 DoBestMemberChecks (ec, spec);
5220                         }
5221
5222                         var fb = spec as FixedFieldSpec;
5223                         IVariableReference var = InstanceExpression as IVariableReference;
5224
5225                         if (lvalue_instance && var != null && var.VariableInfo != null) {
5226                                 var.VariableInfo.SetStructFieldAssigned (ec, Name);
5227                         }
5228
5229                         if (fb != null) {
5230                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5231                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
5232                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
5233                                 }
5234
5235                                 if (InstanceExpression.eclass != ExprClass.Variable) {
5236                                         ec.Report.SymbolRelatedToPreviousError (spec);
5237                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
5238                                                 TypeManager.GetFullNameSignature (spec));
5239                                 } else if (var != null && var.IsHoisted) {
5240                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
5241                                 }
5242
5243                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
5244                         }
5245
5246                         //
5247                         // Set flow-analysis variable info for struct member access. It will be check later
5248                         // for precise error reporting
5249                         //
5250                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
5251                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
5252                                 if (rhs != null && variable_info != null)
5253                                         variable_info.SetStructFieldAssigned (ec, Name);
5254                         }
5255
5256                         eclass = ExprClass.Variable;
5257                         return this;
5258                 }
5259
5260                 public void VerifyAssignedStructField (ResolveContext rc, Expression rhs)
5261                 {
5262                         var fe = this;
5263
5264                         do {
5265                                 var var = fe.InstanceExpression as IVariableReference;
5266                                 if (var != null) {
5267                                         var vi = var.VariableInfo;
5268
5269                                         if (vi != null && !vi.IsStructFieldAssigned (rc, fe.Name) && (rhs == null || !fe.type.IsStruct)) {
5270                                                 if (rhs != null) {
5271                                                         rc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5272                                                 } else {
5273                                                         rc.Report.Error (170, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5274                                                 }
5275
5276                                                 return;
5277                                         }
5278                                 }
5279
5280                                 fe = fe.InstanceExpression as FieldExpr;
5281
5282                         } while (fe != null);
5283                 }
5284
5285                 static readonly int [] codes = {
5286                         191,    // instance, write access
5287                         192,    // instance, out access
5288                         198,    // static, write access
5289                         199,    // static, out access
5290                         1648,   // member of value instance, write access
5291                         1649,   // member of value instance, out access
5292                         1650,   // member of value static, write access
5293                         1651    // member of value static, out access
5294                 };
5295
5296                 static readonly string [] msgs = {
5297                         /*0191*/ "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
5298                         /*0192*/ "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5299                         /*0198*/ "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5300                         /*0199*/ "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5301                         /*1648*/ "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
5302                         /*1649*/ "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5303                         /*1650*/ "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5304                         /*1651*/ "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)"
5305                 };
5306
5307                 // The return value is always null.  Returning a value simplifies calling code.
5308                 Expression Report_AssignToReadonly (ResolveContext ec, Expression right_side)
5309                 {
5310                         int i = 0;
5311                         if (right_side == EmptyExpression.OutAccess || right_side == EmptyExpression.LValueMemberOutAccess)
5312                                 i += 1;
5313                         if (IsStatic)
5314                                 i += 2;
5315                         if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess)
5316                                 i += 4;
5317                         ec.Report.Error (codes [i], loc, msgs [i], GetSignatureForError ());
5318
5319                         return null;
5320                 }
5321
5322                 override public Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5323                 {
5324                         Expression e = DoResolve (ec, right_side);
5325
5326                         if (e == null)
5327                                 return null;
5328
5329                         spec.MemberDefinition.SetIsAssigned ();
5330
5331                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
5332                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
5333                                 ec.Report.Warning (420, 1, loc,
5334                                         "`{0}': A volatile field references will not be treated as volatile",
5335                                         spec.GetSignatureForError ());
5336                         }
5337
5338                         if (spec.IsReadOnly) {
5339                                 // InitOnly fields can only be assigned in constructors or initializers
5340                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
5341                                         return Report_AssignToReadonly (ec, right_side);
5342
5343                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
5344
5345                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
5346                                         if (ec.CurrentMemberDefinition.Parent.Definition != spec.DeclaringType.GetDefinition ())
5347                                                 return Report_AssignToReadonly (ec, right_side);
5348                                         // static InitOnly fields cannot be assigned-to in an instance constructor
5349                                         if (IsStatic && !ec.IsStatic)
5350                                                 return Report_AssignToReadonly (ec, right_side);
5351                                         // instance constructors can't modify InitOnly fields of other instances of the same type
5352                                         if (!IsStatic && !(InstanceExpression is This))
5353                                                 return Report_AssignToReadonly (ec, right_side);
5354                                 }
5355                         }
5356
5357                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
5358                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
5359                                 ec.Report.Warning (197, 1, loc,
5360                                                 "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",
5361                                                 GetSignatureForError ());
5362                         }
5363
5364                         eclass = ExprClass.Variable;
5365                         return this;
5366                 }
5367
5368                 public override int GetHashCode ()
5369                 {
5370                         return spec.GetHashCode ();
5371                 }
5372
5373                 public bool IsFixed {
5374                         get {
5375                                 //
5376                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
5377                                 //
5378                                 IVariableReference variable = InstanceExpression as IVariableReference;
5379                                 if (variable != null)
5380                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
5381
5382                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5383                                 return fe != null && fe.IsFixed;
5384                         }
5385                 }
5386
5387                 public override bool Equals (object obj)
5388                 {
5389                         FieldExpr fe = obj as FieldExpr;
5390                         if (fe == null)
5391                                 return false;
5392
5393                         if (spec != fe.spec)
5394                                 return false;
5395
5396                         if (InstanceExpression == null || fe.InstanceExpression == null)
5397                                 return true;
5398
5399                         return InstanceExpression.Equals (fe.InstanceExpression);
5400                 }
5401
5402                 public void Emit (EmitContext ec, bool leave_copy)
5403                 {
5404                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
5405
5406                         spec.MemberDefinition.SetIsUsed ();
5407
5408                         if (IsStatic){
5409                                 if (is_volatile)
5410                                         ec.Emit (OpCodes.Volatile);
5411
5412                                 ec.Emit (OpCodes.Ldsfld, spec);
5413                         } else {
5414                                 if (!prepared)
5415                                         EmitInstance (ec, false);
5416
5417                                 // Optimization for build-in types
5418                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
5419                                         ec.EmitLoadFromPtr (type);
5420                                 } else {
5421                                         var ff = spec as FixedFieldSpec;
5422                                         if (ff != null) {
5423                                                 ec.Emit (OpCodes.Ldflda, spec);
5424                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
5425                                         } else {
5426                                                 if (is_volatile)
5427                                                         ec.Emit (OpCodes.Volatile);
5428
5429                                                 ec.Emit (OpCodes.Ldfld, spec);
5430                                         }
5431                                 }
5432                         }
5433
5434                         if (leave_copy) {
5435                                 ec.Emit (OpCodes.Dup);
5436                                 if (!IsStatic) {
5437                                         temp = new LocalTemporary (this.Type);
5438                                         temp.Store (ec);
5439                                 }
5440                         }
5441                 }
5442
5443                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
5444                 {
5445                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
5446                         if (isCompound && !(source is DynamicExpressionStatement)) {
5447                                 if (has_await_source) {
5448                                         if (IsInstance)
5449                                                 InstanceExpression = InstanceExpression.EmitToField (ec);
5450                                 } else {
5451                                         prepared = true;
5452                                 }
5453                         }
5454
5455                         if (IsInstance) {
5456                                 if (has_await_source)
5457                                         source = source.EmitToField (ec);
5458
5459                                 EmitInstance (ec, prepared);
5460                         }
5461
5462                         source.Emit (ec);
5463
5464                         if (leave_copy) {
5465                                 ec.Emit (OpCodes.Dup);
5466                                 if (!IsStatic) {
5467                                         temp = new LocalTemporary (this.Type);
5468                                         temp.Store (ec);
5469                                 }
5470                         }
5471
5472                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
5473                                 ec.Emit (OpCodes.Volatile);
5474
5475                         spec.MemberDefinition.SetIsAssigned ();
5476
5477                         if (IsStatic)
5478                                 ec.Emit (OpCodes.Stsfld, spec);
5479                         else
5480                                 ec.Emit (OpCodes.Stfld, spec);
5481
5482                         if (temp != null) {
5483                                 temp.Emit (ec);
5484                                 temp.Release (ec);
5485                                 temp = null;
5486                         }
5487                 }
5488
5489                 //
5490                 // Emits store to field with prepared values on stack
5491                 //
5492                 public void EmitAssignFromStack (EmitContext ec)
5493                 {
5494                         if (IsStatic) {
5495                                 ec.Emit (OpCodes.Stsfld, spec);
5496                         } else {
5497                                 ec.Emit (OpCodes.Stfld, spec);
5498                         }
5499                 }
5500
5501                 public override void Emit (EmitContext ec)
5502                 {
5503                         Emit (ec, false);
5504                 }
5505
5506                 public override void EmitSideEffect (EmitContext ec)
5507                 {
5508                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
5509
5510                         if (is_volatile) // || is_marshal_by_ref ())
5511                                 base.EmitSideEffect (ec);
5512                 }
5513
5514                 public void AddressOf (EmitContext ec, AddressOp mode)
5515                 {
5516                         if ((mode & AddressOp.Store) != 0)
5517                                 spec.MemberDefinition.SetIsAssigned ();
5518                         if ((mode & AddressOp.Load) != 0)
5519                                 spec.MemberDefinition.SetIsUsed ();
5520
5521                         //
5522                         // Handle initonly fields specially: make a copy and then
5523                         // get the address of the copy.
5524                         //
5525                         bool need_copy;
5526                         if (spec.IsReadOnly){
5527                                 need_copy = true;
5528                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
5529                                         if (IsStatic){
5530                                                 if (ec.IsStatic)
5531                                                         need_copy = false;
5532                                         } else
5533                                                 need_copy = false;
5534                                 }
5535                         } else
5536                                 need_copy = false;
5537
5538                         if (need_copy) {
5539                                 Emit (ec);
5540                                 var temp = ec.GetTemporaryLocal (type);
5541                                 ec.Emit (OpCodes.Stloc, temp);
5542                                 ec.Emit (OpCodes.Ldloca, temp);
5543                                 ec.FreeTemporaryLocal (temp, type);
5544                                 return;
5545                         }
5546
5547
5548                         if (IsStatic){
5549                                 ec.Emit (OpCodes.Ldsflda, spec);
5550                         } else {
5551                                 if (!prepared)
5552                                         EmitInstance (ec, false);
5553                                 ec.Emit (OpCodes.Ldflda, spec);
5554                         }
5555                 }
5556
5557                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
5558                 {
5559                         return MakeExpression (ctx);
5560                 }
5561
5562                 public override SLE.Expression MakeExpression (BuilderContext ctx)
5563                 {
5564 #if STATIC
5565                         return base.MakeExpression (ctx);
5566 #else
5567                         return SLE.Expression.Field (
5568                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
5569                                 spec.GetMetaInfo ());
5570 #endif
5571                 }
5572
5573                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5574                 {
5575                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
5576                 }
5577         }
5578
5579
5580         //
5581         // Expression that evaluates to a Property.
5582         //
5583         // This is not an LValue because we need to re-write the expression. We
5584         // can not take data from the stack and store it.
5585         //
5586         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
5587         {
5588                 public PropertyExpr (PropertySpec spec, Location l)
5589                         : base (l)
5590                 {
5591                         best_candidate = spec;
5592                         type = spec.MemberType;
5593                 }
5594
5595                 #region Properties
5596
5597                 protected override Arguments Arguments {
5598                         get {
5599                                 return null;
5600                         }
5601                         set {
5602                         }
5603                 }
5604
5605                 protected override TypeSpec DeclaringType {
5606                         get {
5607                                 return best_candidate.DeclaringType;
5608                         }
5609                 }
5610
5611                 public override string Name {
5612                         get {
5613                                 return best_candidate.Name;
5614                         }
5615                 }
5616
5617                 public override bool IsInstance {
5618                         get {
5619                                 return !IsStatic;
5620                         }
5621                 }
5622
5623                 public override bool IsStatic {
5624                         get {
5625                                 return best_candidate.IsStatic;
5626                         }
5627                 }
5628
5629                 public PropertySpec PropertyInfo {
5630                         get {
5631                                 return best_candidate;
5632                         }
5633                 }
5634
5635                 #endregion
5636
5637                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
5638                 {
5639                         return new PropertyExpr (spec, loc) {
5640                                 Getter = spec.Get,
5641                                 Setter = spec.Set
5642                         };
5643                 }
5644
5645                 public override Expression CreateExpressionTree (ResolveContext ec)
5646                 {
5647                         Arguments args;
5648                         if (IsSingleDimensionalArrayLength ()) {
5649                                 args = new Arguments (1);
5650                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
5651                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
5652                         }
5653
5654                         args = new Arguments (2);
5655                         if (InstanceExpression == null)
5656                                 args.Add (new Argument (new NullLiteral (loc)));
5657                         else
5658                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
5659                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
5660                         return CreateExpressionFactoryCall (ec, "Property", args);
5661                 }
5662
5663                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
5664                 {
5665                         DoResolveLValue (rc, null);
5666                         return new TypeOfMethod (Setter, loc);
5667                 }
5668
5669                 public override string GetSignatureForError ()
5670                 {
5671                         return best_candidate.GetSignatureForError ();
5672                 }
5673
5674                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
5675                 {
5676 #if STATIC
5677                         return base.MakeExpression (ctx);
5678 #else
5679                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
5680 #endif
5681                 }
5682
5683                 public override SLE.Expression MakeExpression (BuilderContext ctx)
5684                 {
5685 #if STATIC
5686                         return base.MakeExpression (ctx);
5687 #else
5688                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
5689 #endif
5690                 }
5691
5692                 void Error_PropertyNotValid (ResolveContext ec)
5693                 {
5694                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
5695                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
5696                                 GetSignatureForError ());
5697                 }
5698
5699                 bool IsSingleDimensionalArrayLength ()
5700                 {
5701                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
5702                                 return false;
5703
5704                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
5705                         return ac != null && ac.Rank == 1;
5706                 }
5707
5708                 public override void Emit (EmitContext ec, bool leave_copy)
5709                 {
5710                         //
5711                         // Special case: length of single dimension array property is turned into ldlen
5712                         //
5713                         if (IsSingleDimensionalArrayLength ()) {
5714                                 EmitInstance (ec, false);
5715                                 ec.Emit (OpCodes.Ldlen);
5716                                 ec.Emit (OpCodes.Conv_I4);
5717                                 return;
5718                         }
5719
5720                         base.Emit (ec, leave_copy);
5721                 }
5722
5723                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
5724                 {
5725                         Arguments args;
5726                         LocalTemporary await_source_arg = null;
5727
5728                         if (isCompound && !(source is DynamicExpressionStatement)) {
5729                                 emitting_compound_assignment = true;
5730                                 source.Emit (ec);
5731
5732                                 if (has_await_arguments) {
5733                                         await_source_arg = new LocalTemporary (Type);
5734                                         await_source_arg.Store (ec);
5735
5736                                         args = new Arguments (1);
5737                                         args.Add (new Argument (await_source_arg));
5738
5739                                         if (leave_copy) {
5740                                                 temp = await_source_arg;
5741                                         }
5742
5743                                         has_await_arguments = false;
5744                                 } else {
5745                                         args = null;
5746
5747                                         if (leave_copy) {
5748                                                 ec.Emit (OpCodes.Dup);
5749                                                 temp = new LocalTemporary (this.Type);
5750                                                 temp.Store (ec);
5751                                         }
5752                                 }
5753                         } else {
5754                                 args = new Arguments (1);
5755
5756                                 if (leave_copy) {
5757                                         source.Emit (ec);
5758                                         temp = new LocalTemporary (this.Type);
5759                                         temp.Store (ec);
5760                                         args.Add (new Argument (temp));
5761                                 } else {
5762                                         args.Add (new Argument (source));
5763                                 }
5764                         }
5765
5766                         emitting_compound_assignment = false;
5767
5768                         var call = new CallEmitter ();
5769                         call.InstanceExpression = InstanceExpression;
5770                         if (args == null)
5771                                 call.InstanceExpressionOnStack = true;
5772
5773                         call.Emit (ec, Setter, args, loc);
5774
5775                         if (temp != null) {
5776                                 temp.Emit (ec);
5777                                 temp.Release (ec);
5778                         }
5779
5780                         if (await_source_arg != null) {
5781                                 await_source_arg.Release (ec);
5782                         }
5783                 }
5784
5785                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
5786                 {
5787                         eclass = ExprClass.PropertyAccess;
5788
5789                         if (best_candidate.IsNotCSharpCompatible) {
5790                                 Error_PropertyNotValid (rc);
5791                         }
5792
5793                         ResolveInstanceExpression (rc, right_side);
5794
5795                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
5796                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
5797                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
5798                                 if (p != null) {
5799                                         type = p.MemberType;
5800                                 }
5801                         }
5802
5803                         DoBestMemberChecks (rc, best_candidate);
5804                         return this;
5805                 }
5806
5807                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5808                 {
5809                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
5810                 }
5811         }
5812
5813         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
5814         {
5815                 // getter and setter can be different for base calls
5816                 MethodSpec getter, setter;
5817                 protected T best_candidate;
5818
5819                 protected LocalTemporary temp;
5820                 protected bool emitting_compound_assignment;
5821                 protected bool has_await_arguments;
5822
5823                 protected PropertyOrIndexerExpr (Location l)
5824                 {
5825                         loc = l;
5826                 }
5827
5828                 #region Properties
5829
5830                 protected abstract Arguments Arguments { get; set; }
5831
5832                 public MethodSpec Getter {
5833                         get {
5834                                 return getter;
5835                         }
5836                         set {
5837                                 getter = value;
5838                         }
5839                 }
5840
5841                 public MethodSpec Setter {
5842                         get {
5843                                 return setter;
5844                         }
5845                         set {
5846                                 setter = value;
5847                         }
5848                 }
5849
5850                 #endregion
5851
5852                 protected override Expression DoResolve (ResolveContext ec)
5853                 {
5854                         if (eclass == ExprClass.Unresolved) {
5855                                 var expr = OverloadResolve (ec, null);
5856                                 if (expr == null)
5857                                         return null;
5858
5859                                 if (expr != this)
5860                                         return expr.Resolve (ec);
5861                         }
5862
5863                         if (!ResolveGetter (ec))
5864                                 return null;
5865
5866                         return this;
5867                 }
5868
5869                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5870                 {
5871                         if (right_side == EmptyExpression.OutAccess) {
5872                                 // TODO: best_candidate can be null at this point
5873                                 INamedBlockVariable variable = null;
5874                                 if (best_candidate != null && ec.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, ec.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
5875                                         ec.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
5876                                                 best_candidate.Name);
5877                                 } else {
5878                                         right_side.DoResolveLValue (ec, this);
5879                                 }
5880                                 return null;
5881                         }
5882
5883                         // if the property/indexer returns a value type, and we try to set a field in it
5884                         if (right_side == EmptyExpression.LValueMemberAccess || right_side == EmptyExpression.LValueMemberOutAccess) {
5885                                 Error_ValueAssignment (ec, right_side);
5886                         }
5887
5888                         if (eclass == ExprClass.Unresolved) {
5889                                 var expr = OverloadResolve (ec, right_side);
5890                                 if (expr == null)
5891                                         return null;
5892
5893                                 if (expr != this)
5894                                         return expr.ResolveLValue (ec, right_side);
5895                         }
5896
5897                         if (!ResolveSetter (ec))
5898                                 return null;
5899
5900                         return this;
5901                 }
5902
5903                 //
5904                 // Implements the IAssignMethod interface for assignments
5905                 //
5906                 public virtual void Emit (EmitContext ec, bool leave_copy)
5907                 {
5908                         var call = new CallEmitter ();
5909                         call.InstanceExpression = InstanceExpression;
5910                         if (has_await_arguments)
5911                                 call.HasAwaitArguments = true;
5912                         else
5913                                 call.DuplicateArguments = emitting_compound_assignment;
5914
5915                         call.Emit (ec, Getter, Arguments, loc);
5916
5917                         if (call.HasAwaitArguments) {
5918                                 InstanceExpression = call.InstanceExpression;
5919                                 Arguments = call.EmittedArguments;
5920                                 has_await_arguments = true;
5921                         }
5922
5923                         if (leave_copy) {
5924                                 ec.Emit (OpCodes.Dup);
5925                                 temp = new LocalTemporary (Type);
5926                                 temp.Store (ec);
5927                         }
5928                 }
5929
5930                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
5931
5932                 public override void Emit (EmitContext ec)
5933                 {
5934                         Emit (ec, false);
5935                 }
5936
5937                 protected override void EmitToFieldSource (EmitContext ec)
5938                 {
5939                         has_await_arguments = true;
5940                         Emit (ec, false);
5941                 }
5942
5943                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
5944
5945                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
5946
5947                 bool ResolveGetter (ResolveContext rc)
5948                 {
5949                         if (!best_candidate.HasGet) {
5950                                 if (InstanceExpression != EmptyExpression.Null) {
5951                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
5952                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
5953                                                 best_candidate.GetSignatureForError ());
5954                                         return false;
5955                                 }
5956                         } else if (!best_candidate.Get.IsAccessible (rc)) {
5957                                 if (best_candidate.HasDifferentAccessibility) {
5958                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
5959                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
5960                                                 TypeManager.CSharpSignature (best_candidate));
5961                                 } else {
5962                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
5963                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
5964                                 }
5965                         }
5966
5967                         if (best_candidate.HasDifferentAccessibility) {
5968                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
5969                         }
5970
5971                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
5972                         return true;
5973                 }
5974
5975                 bool ResolveSetter (ResolveContext rc)
5976                 {
5977                         if (!best_candidate.HasSet) {
5978                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
5979                                         GetSignatureForError ());
5980                                 return false;
5981                         }
5982
5983                         if (!best_candidate.Set.IsAccessible (rc)) {
5984                                 if (best_candidate.HasDifferentAccessibility) {
5985                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
5986                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
5987                                                 GetSignatureForError ());
5988                                 } else {
5989                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
5990                                         ErrorIsInaccesible (rc, best_candidate.Set.GetSignatureForError (), loc);
5991                                 }
5992                         }
5993
5994                         if (best_candidate.HasDifferentAccessibility)
5995                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
5996
5997                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
5998                         return true;
5999                 }
6000         }
6001
6002         /// <summary>
6003         ///   Fully resolved expression that evaluates to an Event
6004         /// </summary>
6005         public class EventExpr : MemberExpr, IAssignMethod
6006         {
6007                 readonly EventSpec spec;
6008                 MethodSpec op;
6009
6010                 public EventExpr (EventSpec spec, Location loc)
6011                 {
6012                         this.spec = spec;
6013                         this.loc = loc;
6014                 }
6015
6016                 #region Properties
6017
6018                 protected override TypeSpec DeclaringType {
6019                         get {
6020                                 return spec.DeclaringType;
6021                         }
6022                 }
6023
6024                 public override string Name {
6025                         get {
6026                                 return spec.Name;
6027                         }
6028                 }
6029
6030                 public override bool IsInstance {
6031                         get {
6032                                 return !spec.IsStatic;
6033                         }
6034                 }
6035
6036                 public override bool IsStatic {
6037                         get {
6038                                 return spec.IsStatic;
6039                         }
6040                 }
6041
6042                 public MethodSpec Operator {
6043                         get {
6044                                 return op;
6045                         }
6046                 }
6047
6048                 #endregion
6049
6050                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
6051                 {
6052                         //
6053                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
6054                         //
6055                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6056                                 if (spec.BackingField != null &&
6057                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
6058
6059                                         spec.MemberDefinition.SetIsUsed ();
6060
6061                                         if (!ec.IsObsolete) {
6062                                                 ObsoleteAttribute oa = spec.GetAttributeObsolete ();
6063                                                 if (oa != null)
6064                                                         AttributeTester.Report_ObsoleteMessage (oa, spec.GetSignatureForError (), loc, ec.Report);
6065                                         }
6066
6067                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
6068                                                 Error_AssignmentEventOnly (ec);
6069
6070                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
6071
6072                                         InstanceExpression = null;
6073
6074                                         return ml.ResolveMemberAccess (ec, left, original);
6075                                 }
6076                         }
6077
6078                         return base.ResolveMemberAccess (ec, left, original);
6079                 }
6080
6081                 public override Expression CreateExpressionTree (ResolveContext ec)
6082                 {
6083                         throw new NotSupportedException ("ET");
6084                 }
6085
6086                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6087                 {
6088                         if (right_side == EmptyExpression.EventAddition) {
6089                                 op = spec.AccessorAdd;
6090                         } else if (right_side == EmptyExpression.EventSubtraction) {
6091                                 op = spec.AccessorRemove;
6092                         }
6093
6094                         if (op == null) {
6095                                 Error_AssignmentEventOnly (ec);
6096                                 return null;
6097                         }
6098
6099                         op = CandidateToBaseOverride (ec, op);
6100                         return this;
6101                 }
6102
6103                 protected override Expression DoResolve (ResolveContext ec)
6104                 {
6105                         eclass = ExprClass.EventAccess;
6106                         type = spec.MemberType;
6107
6108                         ResolveInstanceExpression (ec, null);
6109
6110                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6111                                 Error_AssignmentEventOnly (ec);
6112                         }
6113
6114                         DoBestMemberChecks (ec, spec);
6115                         return this;
6116                 }
6117
6118                 public override void Emit (EmitContext ec)
6119                 {
6120                         throw new NotSupportedException ();
6121                         //Error_CannotAssign ();
6122                 }
6123
6124                 #region IAssignMethod Members
6125
6126                 public void Emit (EmitContext ec, bool leave_copy)
6127                 {
6128                         throw new NotImplementedException ();
6129                 }
6130
6131                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6132                 {
6133                         if (leave_copy || !isCompound)
6134                                 throw new NotImplementedException ("EventExpr::EmitAssign");
6135
6136                         Arguments args = new Arguments (1);
6137                         args.Add (new Argument (source));
6138
6139                         var call = new CallEmitter ();
6140                         call.InstanceExpression = InstanceExpression;
6141                         call.Emit (ec, op, args, loc);
6142                 }
6143
6144                 #endregion
6145
6146                 void Error_AssignmentEventOnly (ResolveContext ec)
6147                 {
6148                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
6149                                 ec.Report.Error (79, loc,
6150                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
6151                                         GetSignatureForError ());
6152                         } else {
6153                                 ec.Report.Error (70, loc,
6154                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
6155                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
6156                         }
6157                 }
6158
6159                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
6160                 {
6161                         name = name.Substring (0, name.LastIndexOf ('.'));
6162                         base.Error_CannotCallAbstractBase (rc, name);
6163                 }
6164
6165                 public override string GetSignatureForError ()
6166                 {
6167                         return TypeManager.CSharpSignature (spec);
6168                 }
6169
6170                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6171                 {
6172                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
6173                 }
6174         }
6175
6176         public class TemporaryVariableReference : VariableReference
6177         {
6178                 public class Declarator : Statement
6179                 {
6180                         TemporaryVariableReference variable;
6181
6182                         public Declarator (TemporaryVariableReference variable)
6183                         {
6184                                 this.variable = variable;
6185                                 loc = variable.loc;
6186                         }
6187
6188                         protected override void DoEmit (EmitContext ec)
6189                         {
6190                                 variable.li.CreateBuilder (ec);
6191                         }
6192
6193                         protected override void CloneTo (CloneContext clonectx, Statement target)
6194                         {
6195                                 // Nothing
6196                         }
6197                 }
6198
6199                 LocalVariable li;
6200
6201                 public TemporaryVariableReference (LocalVariable li, Location loc)
6202                 {
6203                         this.li = li;
6204                         this.type = li.Type;
6205                         this.loc = loc;
6206                 }
6207
6208                 public override bool IsLockedByStatement {
6209                         get {
6210                                 return false;
6211                         }
6212                         set {
6213                         }
6214                 }
6215
6216                 public LocalVariable LocalInfo {
6217                     get {
6218                         return li;
6219                     }
6220                 }
6221
6222                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc)
6223                 {
6224                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc);
6225                         return new TemporaryVariableReference (li, loc);
6226                 }
6227
6228                 protected override Expression DoResolve (ResolveContext ec)
6229                 {
6230                         eclass = ExprClass.Variable;
6231
6232                         //
6233                         // Don't capture temporary variables except when using
6234                         // state machine redirection
6235                         //
6236                         if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod is StateMachineInitializer && ec.IsVariableCapturingRequired) {
6237                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
6238                                 storey.CaptureLocalVariable (ec, li);
6239                         }
6240
6241                         return this;
6242                 }
6243
6244                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6245                 {
6246                         return Resolve (ec);
6247                 }
6248
6249                 public override void Emit (EmitContext ec)
6250                 {
6251                         li.CreateBuilder (ec);
6252
6253                         Emit (ec, false);
6254                 }
6255
6256                 public void EmitAssign (EmitContext ec, Expression source)
6257                 {
6258                         li.CreateBuilder (ec);
6259
6260                         EmitAssign (ec, source, false, false);
6261                 }
6262
6263                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
6264                 {
6265                         return li.HoistedVariant;
6266                 }
6267
6268                 public override bool IsFixed {
6269                         get { return true; }
6270                 }
6271
6272                 public override bool IsRef {
6273                         get { return false; }
6274                 }
6275
6276                 public override string Name {
6277                         get { throw new NotImplementedException (); }
6278                 }
6279
6280                 public override void SetHasAddressTaken ()
6281                 {
6282                         throw new NotImplementedException ();
6283                 }
6284
6285                 protected override ILocalVariable Variable {
6286                         get { return li; }
6287                 }
6288
6289                 public override VariableInfo VariableInfo {
6290                         get { return null; }
6291                 }
6292
6293                 public override void VerifyAssigned (ResolveContext rc)
6294                 {
6295                 }
6296         }
6297
6298         ///
6299         /// Handles `var' contextual keyword; var becomes a keyword only
6300         /// if no type called var exists in a variable scope
6301         ///
6302         class VarExpr : SimpleName
6303         {
6304                 public VarExpr (Location loc)
6305                         : base ("var", loc)
6306                 {
6307                 }
6308
6309                 public bool InferType (ResolveContext ec, Expression right_side)
6310                 {
6311                         if (type != null)
6312                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
6313
6314                         type = right_side.Type;
6315                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
6316                                 ec.Report.Error (815, loc,
6317                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
6318                                         type.GetSignatureForError ());
6319                                 return false;
6320                         }
6321
6322                         eclass = ExprClass.Variable;
6323                         return true;
6324                 }
6325
6326                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
6327                 {
6328                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
6329                                 base.Error_TypeOrNamespaceNotFound (ec);
6330                         else
6331                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
6332                 }
6333         }
6334 }