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