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