mcs/mcs/ecore.cs

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