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)
 232                 {
 233                         ResolveContext ec = new ResolveContext (mc);
 234                         Expression e = Resolve (ec);
 235                         if (e != null)
 236                                 e.Error_UnexpectedKind (ec, 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                 /// <summary>
 434                 ///   Resolves an expression and performs semantic analysis on it.
 435                 /// </summary>
 436                 ///
 437                 /// <remarks>
 438                 ///   Currently Resolve wraps DoResolve to perform sanity
 439                 ///   checking and assertion checking on what we expect from Resolve.
 440                 /// </remarks>
 441                 public Expression Resolve (ResolveContext ec, ResolveFlags flags)
 442                 {
 443                         if (eclass != ExprClass.Unresolved) {
 444                                 if ((flags & ExprClassToResolveFlags) == 0) {
 445                                         Error_UnexpectedKind (ec, flags, loc);
 446                                         return null;
 447                                 }
 448
 449                                 return this;
 450                         }
 451
 452                         Expression e;
 453                         try {
 454                                 e = DoResolve (ec);
 455
 456                                 if (e == null)
 457                                         return null;
 458
 459                                 if ((flags & e.ExprClassToResolveFlags) == 0) {
 460                                         e.Error_UnexpectedKind (ec, flags, loc);
 461                                         return null;
 462                                 }
 463
 464                                 if (e.type == null)
 465                                         throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());
 466
 467                                 return e;
 468                         } catch (Exception ex) {
 469                                 if (loc.IsNull || ec.Module.Compiler.Settings.BreakOnInternalError || ex is CompletionResult || ec.Report.IsDisabled || ex is FatalException ||
 470                                         ec.Report.Printer is NullReportPrinter)
 471                                         throw;
 472
 473                                 ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
 474                                 return ErrorExpression.Instance;        // TODO: Add location
 475                         }
 476                 }
 477
 478                 /// <summary>
 479                 ///   Resolves an expression and performs semantic analysis on it.
 480                 /// </summary>
 481                 public Expression Resolve (ResolveContext rc)
 482                 {
 483                         return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
 484                 }
 485
 486                 /// <summary>
 487                 ///   Resolves an expression for LValue assignment
 488                 /// </summary>
 489                 ///
 490                 /// <remarks>
 491                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 492                 ///   checking and assertion checking on what we expect from Resolve
 493                 /// </remarks>
 494                 public Expression ResolveLValue (ResolveContext ec, Expression right_side)
 495                 {
 496                         int errors = ec.Report.Errors;
 497                         bool out_access = right_side == EmptyExpression.OutAccess;
 498
 499                         Expression e = DoResolveLValue (ec, right_side);
 500
 501                         if (e != null && out_access && !(e is IMemoryLocation)) {
 502                                 // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
 503                                 //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,
 504
 505                                 //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
 506                                 //                                e.GetType () + " " + e.GetSignatureForError ());
 507                                 e = null;
 508                         }
 509
 510                         if (e == null) {
 511                                 if (errors == ec.Report.Errors) {
 512                                         Error_ValueAssignment (ec, right_side);
 513                                 }
 514                                 return null;
 515                         }
 516
 517                         if (e.eclass == ExprClass.Unresolved)
 518                                 throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");
 519
 520                         if ((e.type == null) && !(e is GenericTypeExpr))
 521                                 throw new Exception ("Expression " + e + " did not set its type after Resolve");
 522
 523                         return e;
 524                 }
 525
 526                 public Constant ResolveLabelConstant (ResolveContext rc)
 527                 {
 528                         var expr = Resolve (rc);
 529                         if (expr == null)
 530                                 return null;
 531
 532                         Constant c = expr as Constant;
 533                         if (c == null) {
 534                                 if (expr.type != InternalType.ErrorType)
 535                                         rc.Report.Error (150, expr.StartLocation, "A constant value is expected");
 536
 537                                 return null;
 538                         }
 539
 540                         return c;
 541                 }
 542
 543                 public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
 544                 {
 545                         rc.Module.Compiler.Report.Error (182, loc,
 546                                 "An attribute argument must be a constant expression, typeof expression or array creation expression");
 547                 }
 548
 549                 /// <summary>
 550                 ///   Emits the code for the expression
 551                 /// </summary>
 552                 ///
 553                 /// <remarks>
 554                 ///   The Emit method is invoked to generate the code
 555                 ///   for the expression.
 556                 /// </remarks>
 557                 public abstract void Emit (EmitContext ec);
 558
 559
 560                 // Emit code to branch to @target if this expression is equivalent to @on_true.
 561                 // The default implementation is to emit the value, and then emit a brtrue or brfalse.
 562                 // Subclasses can provide more efficient implementations, but those MUST be equivalent,
 563                 // including the use of conditional branches.  Note also that a branch MUST be emitted
 564                 public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
 565                 {
 566                         Emit (ec);
 567                         ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
 568                 }
 569
 570                 // Emit this expression for its side effects, not for its value.
 571                 // The default implementation is to emit the value, and then throw it away.
 572                 // Subclasses can provide more efficient implementations, but those MUST be equivalent
 573                 public virtual void EmitSideEffect (EmitContext ec)
 574                 {
 575                         Emit (ec);
 576                         ec.Emit (OpCodes.Pop);
 577                 }
 578
 579                 //
 580                 // Emits the expression into temporary field variable. The method
 581                 // should be used for await expressions only
 582                 //
 583                 public virtual Expression EmitToField (EmitContext ec)
 584                 {
 585                         //
 586                         // This is the await prepare Emit method. When emitting code like
 587                         // a + b we emit code like
 588                         //
 589                         // a.Emit ()
 590                         // b.Emit ()
 591                         // Opcodes.Add
 592                         //
 593                         // For await a + await b we have to interfere the flow to keep the
 594                         // stack clean because await yields from the expression. The emit
 595                         // then changes to
 596                         //
 597                         // a = a.EmitToField () // a is changed to temporary field access
 598                         // b = b.EmitToField ()
 599                         // a.Emit ()
 600                         // b.Emit ()
 601                         // Opcodes.Add
 602                         //
 603                         //
 604                         // The idea is to emit expression and leave the stack empty with
 605                         // result value still available.
 606                         //
 607                         // Expressions should override this default implementation when
 608                         // optimized version can be provided (e.g. FieldExpr)
 609                         //
 610                         //
 611                         // We can optimize for side-effect free expressions, they can be
 612                         // emitted out of order
 613                         //
 614                         if (IsSideEffectFree)
 615                                 return this;
 616
 617                         bool needs_temporary = ContainsEmitWithAwait ();
 618                         if (!needs_temporary)
 619                                 ec.EmitThis ();
 620
 621                         // Emit original code
 622                         var field = EmitToFieldSource (ec);
 623                         if (field == null) {
 624                                 //
 625                                 // Store the result to temporary field when we
 626                                 // cannot load `this' directly
 627                                 //
 628                                 field = ec.GetTemporaryField (type);
 629                                 if (needs_temporary) {
 630                                         //
 631                                         // Create temporary local (we cannot load `this' before Emit)
 632                                         //
 633                                         var temp = ec.GetTemporaryLocal (type);
 634                                         ec.Emit (OpCodes.Stloc, temp);
 635
 636                                         ec.EmitThis ();
 637                                         ec.Emit (OpCodes.Ldloc, temp);
 638                                         field.EmitAssignFromStack (ec);
 639
 640                                         ec.FreeTemporaryLocal (temp, type);
 641                                 } else {
 642                                         field.EmitAssignFromStack (ec);
 643                                 }
 644                         }
 645
 646                         return field;
 647                 }
 648
 649                 protected virtual FieldExpr EmitToFieldSource (EmitContext ec)
 650                 {
 651                         //
 652                         // Default implementation calls Emit method
 653                         //
 654                         Emit (ec);
 655                         return null;
 656                 }
 657
 658                 protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
 659                 {
 660                         if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
 661                                 bool contains_await = false;
 662
 663                                 for (int i = 1; i < expressions.Count; ++i) {
 664                                         if (expressions[i].ContainsEmitWithAwait ()) {
 665                                                 contains_await = true;
 666                                                 break;
 667                                         }
 668                                 }
 669
 670                                 if (contains_await) {
 671                                         for (int i = 0; i < expressions.Count; ++i) {
 672                                                 expressions[i] = expressions[i].EmitToField (ec);
 673                                         }
 674                                 }
 675                         }
 676
 677                         for (int i = 0; i < expressions.Count; ++i) {
 678                                 expressions[i].Emit (ec);
 679                         }
 680                 }
 681
 682                 /// <summary>
 683                 ///   Protected constructor.  Only derivate types should
 684                 ///   be able to be created
 685                 /// </summary>
 686
 687                 protected Expression ()
 688                 {
 689                 }
 690
 691                 /// <summary>
 692                 ///   Returns a fully formed expression after a MemberLookup
 693                 /// </summary>
 694                 ///
 695                 static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
 696                 {
 697                         if (spec is EventSpec)
 698                                 return new EventExpr ((EventSpec) spec, loc);
 699                         if (spec is ConstSpec)
 700                                 return new ConstantExpr ((ConstSpec) spec, loc);
 701                         if (spec is FieldSpec)
 702                                 return new FieldExpr ((FieldSpec) spec, loc);
 703                         if (spec is PropertySpec)
 704                                 return new PropertyExpr ((PropertySpec) spec, loc);
 705                         if (spec is TypeSpec)
 706                                 return new TypeExpression (((TypeSpec) spec), loc);
 707
 708                         return null;
 709                 }
 710
 711                 public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
 712                 {
 713                         var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
 714                         if (ctors == null) {
 715                                 switch (type.Kind) {
 716                                 case MemberKind.Struct:
 717                                         rc.Report.SymbolRelatedToPreviousError (type);
 718                                         // Report meaningful error for struct as they always have default ctor in C# context
 719                                         OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
 720                                         break;
 721                                 case MemberKind.MissingType:
 722                                 case MemberKind.InternalCompilerType:
 723                                         break;
 724                                 default:
 725                                         rc.Report.SymbolRelatedToPreviousError (type);
 726                                         rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
 727                                                 type.GetSignatureForError ());
 728                                         break;
 729                                 }
 730
 731                                 return null;
 732                         }
 733
 734                         var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
 735                         if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
 736                                 r.InstanceQualifier = new ConstructorInstanceQualifier (type);
 737                         }
 738
 739                         return r.ResolveMember<MethodSpec> (rc, ref args);
 740                 }
 741
 742                 [Flags]
 743                 public enum MemberLookupRestrictions
 744                 {
 745                         None = 0,
 746                         InvocableOnly = 1,
 747                         ExactArity = 1 << 2,
 748                         ReadAccess = 1 << 3
 749                 }
 750
 751                 //
 752                 // Lookup type `queried_type' for code in class `container_type' with a qualifier of
 753                 // `qualifier_type' or null to lookup members in the current class.
 754                 //
 755                 public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 756                 {
 757                         var members = MemberCache.FindMembers (queried_type, name, false);
 758                         if (members == null)
 759                                 return null;
 760
 761                         MemberSpec non_method = null;
 762                         MemberSpec ambig_non_method = null;
 763                         do {
 764                                 for (int i = 0; i < members.Count; ++i) {
 765                                         var member = members[i];
 766
 767                                         // HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
 768                                         if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
 769                                                 continue;
 770
 771                                         if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0 || member.Kind == MemberKind.Operator)
 772                                                 continue;
 773
 774                                         if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
 775                                                 continue;
 776
 777                                         if (!errorMode) {
 778                                                 if (!member.IsAccessible (rc))
 779                                                         continue;
 780
 781                                                 //
 782                                                 // With runtime binder we can have a situation where queried type is inaccessible
 783                                                 // because it came via dynamic object, the check about inconsisted accessibility
 784                                                 // had no effect as the type was unknown during compilation
 785                                                 //
 786                                                 // class A {
 787                                                 //              private class N { }
 788                                                 //
 789                                                 //              public dynamic Foo ()
 790                                                 //              {
 791                                                 //                      return new N ();
 792                                                 //              }
 793                                                 //      }
 794                                                 //
 795                                                 if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
 796                                                         continue;
 797                                         }
 798
 799                                         if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
 800                                                 if (member is MethodSpec) {
 801                                                         //
 802                                                         // Interface members that are hidden by class members are removed from the set. This
 803                                                         // step only has an effect if T is a type parameter and T has both an effective base
 804                                                         // class other than object and a non-empty effective interface set
 805                                                         //
 806                                                         var tps = queried_type as TypeParameterSpec;
 807                                                         if (tps != null && tps.HasTypeConstraint)
 808                                                                 members = RemoveHiddenTypeParameterMethods (members);
 809
 810                                                         return new MethodGroupExpr (members, queried_type, loc);
 811                                                 }
 812
 813                                                 if (!Invocation.IsMemberInvocable (member))
 814                                                         continue;
 815                                         }
 816
 817                                         if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
 818                                                 non_method = member;
 819                                         } else if (!errorMode && !member.IsNotCSharpCompatible) {
 820                                                 //
 821                                                 // Interface members that are hidden by class members are removed from the set when T is a type parameter and
 822                                                 // T has both an effective base class other than object and a non-empty effective interface set.
 823                                                 //
 824                                                 // The spec has more complex rules but we simply remove all members declared in an interface declaration.
 825                                                 //
 826                                                 var tps = queried_type as TypeParameterSpec;
 827                                                 if (tps != null && tps.HasTypeConstraint) {
 828                                                         if (non_method.DeclaringType.IsClass && member.DeclaringType.IsInterface)
 829                                                                 continue;
 830
 831                                                         if (non_method.DeclaringType.IsInterface && member.DeclaringType.IsInterface) {
 832                                                                 non_method = member;
 833                                                                 continue;
 834                                                         }
 835                                                 }
 836
 837                                                 ambig_non_method = member;
 838                                         }
 839                                 }
 840
 841                                 if (non_method != null) {
 842                                         if (ambig_non_method != null && rc != null) {
 843                                                 var report = rc.Module.Compiler.Report;
 844                                                 report.SymbolRelatedToPreviousError (non_method);
 845                                                 report.SymbolRelatedToPreviousError (ambig_non_method);
 846                                                 report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
 847                                                         non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
 848                                         }
 849
 850                                         if (non_method is MethodSpec)
 851                                                 return new MethodGroupExpr (members, queried_type, loc);
 852
 853                                         return ExprClassFromMemberInfo (non_method, loc);
 854                                 }
 855
 856                                 if (members[0].DeclaringType.BaseType == null)
 857                                         members = null;
 858                                 else
 859                                         members = MemberCache.FindMembers (members[0].DeclaringType.BaseType, name, false);
 860
 861                         } while (members != null);
 862
 863                         return null;
 864                 }
 865
 866                 static IList<MemberSpec> RemoveHiddenTypeParameterMethods (IList<MemberSpec> members)
 867                 {
 868                         if (members.Count < 2)
 869                                 return members;
 870
 871                         //
 872                         // If M is a method, then all non-method members declared in an interface declaration
 873                         // are removed from the set, and all methods with the same signature as M declared in
 874                         // an interface declaration are removed from the set
 875                         //
 876
 877                         bool copied = false;
 878                         for (int i = 0; i < members.Count; ++i) {
 879                                 var method = members[i] as MethodSpec;
 880                                 if (method == null) {
 881                                         if (!copied) {
 882                                                 copied = true;
 883                                                 members = new List<MemberSpec> (members);
 884                                         }
 885
 886                                         members.RemoveAt (i--);
 887                                         continue;
 888                                 }
 889
 890                                 if (!method.DeclaringType.IsInterface)
 891                                         continue;
 892
 893                                 for (int ii = 0; ii < members.Count; ++ii) {
 894                                         var candidate = members[ii] as MethodSpec;
 895                                         if (candidate == null || !candidate.DeclaringType.IsClass)
 896                                                 continue;
 897
 898                                         if (!TypeSpecComparer.Override.IsEqual (candidate.Parameters, method.Parameters))
 899                                                 continue;
 900
 901                                         if (!copied) {
 902                                                 copied = true;
 903                                                 members = new List<MemberSpec> (members);
 904                                         }
 905
 906                                         members.RemoveAt (i--);
 907                                         break;
 908                                 }
 909                         }
 910
 911                         return members;
 912                 }
 913
 914                 protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
 915                 {
 916                         throw new NotImplementedException ();
 917                 }
 918
 919                 public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
 920                 {
 921                         if (t == InternalType.ErrorType)
 922                                 return;
 923
 924                         rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
 925                                 oper, t.GetSignatureForError ());
 926                 }
 927
 928                 protected void Error_PointerInsideExpressionTree (ResolveContext ec)
 929                 {
 930                         ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
 931                 }
 932
 933                 public virtual void FlowAnalysis (FlowAnalysisContext fc)
 934                 {
 935                 }
 936
 937                 /// <summary>
 938                 ///   Returns an expression that can be used to invoke operator true
 939                 ///   on the expression if it exists.
 940                 /// </summary>
 941                 protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
 942                 {
 943                         return GetOperatorTrueOrFalse (ec, e, true, loc);
 944                 }
 945
 946                 /// <summary>
 947                 ///   Returns an expression that can be used to invoke operator false
 948                 ///   on the expression if it exists.
 949                 /// </summary>
 950                 protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
 951                 {
 952                         return GetOperatorTrueOrFalse (ec, e, false, loc);
 953                 }
 954
 955                 static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
 956                 {
 957                         var op = is_true ? Operator.OpType.True : Operator.OpType.False;
 958                         var methods = MemberCache.GetUserOperator (e.type, op, false);
 959                         if (methods == null)
 960                                 return null;
 961
 962                         Arguments arguments = new Arguments (1);
 963                         arguments.Add (new Argument (e));
 964
 965                         var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
 966                         var oper = res.ResolveOperator (ec, ref arguments);
 967
 968                         if (oper == null)
 969                                 return null;
 970
 971                         return new UserOperatorCall (oper, arguments, null, loc);
 972                 }
 973
 974                 public virtual string ExprClassName
 975                 {
 976                         get {
 977                                 switch (eclass){
 978                                 case ExprClass.Unresolved:
 979                                         return "Unresolved";
 980                                 case ExprClass.Value:
 981                                         return "value";
 982                                 case ExprClass.Variable:
 983                                         return "variable";
 984                                 case ExprClass.Namespace:
 985                                         return "namespace";
 986                                 case ExprClass.Type:
 987                                         return "type";
 988                                 case ExprClass.MethodGroup:
 989                                         return "method group";
 990                                 case ExprClass.PropertyAccess:
 991                                         return "property access";
 992                                 case ExprClass.EventAccess:
 993                                         return "event access";
 994                                 case ExprClass.IndexerAccess:
 995                                         return "indexer access";
 996                                 case ExprClass.Nothing:
 997                                         return "null";
 998                                 case ExprClass.TypeParameter:
 999                                         return "type parameter";
1000                                 }
1001                                 throw new Exception ("Should not happen");
1002                         }
1003                 }
1004
1005                 /// <summary>
1006                 ///   Reports that we were expecting `expr' to be of class `expected'
1007                 /// </summary>
1008                 public static void Error_UnexpectedKind (IMemberContext ctx, Expression memberExpr, string expected, string was, Location loc)
1009                 {
1010                         var name = memberExpr.GetSignatureForError ();
1011
1012                         ctx.Module.Compiler.Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected", name, was, expected);
1013                 }
1014
1015                 public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
1016                 {
1017                         string [] valid = new string [4];
1018                         int count = 0;
1019
1020                         if ((flags & ResolveFlags.VariableOrValue) != 0) {
1021                                 valid [count++] = "variable";
1022                                 valid [count++] = "value";
1023                         }
1024
1025                         if ((flags & ResolveFlags.Type) != 0)
1026                                 valid [count++] = "type";
1027
1028                         if ((flags & ResolveFlags.MethodGroup) != 0)
1029                                 valid [count++] = "method group";
1030
1031                         if (count == 0)
1032                                 valid [count++] = "unknown";
1033
1034                         StringBuilder sb = new StringBuilder (valid [0]);
1035                         for (int i = 1; i < count - 1; i++) {
1036                                 sb.Append ("', `");
1037                                 sb.Append (valid [i]);
1038                         }
1039                         if (count > 1) {
1040                                 sb.Append ("' or `");
1041                                 sb.Append (valid [count - 1]);
1042                         }
1043
1044                         ec.Report.Error (119, loc,
1045                                 "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
1046                 }
1047
1048                 public static void UnsafeError (ResolveContext ec, Location loc)
1049                 {
1050                         UnsafeError (ec.Report, loc);
1051                 }
1052
1053                 public static void UnsafeError (Report Report, Location loc)
1054                 {
1055                         Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
1056                 }
1057
1058                 //
1059                 // Converts `source' to an int, uint, long or ulong.
1060                 //
1061                 protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source, bool pointerArray = false)
1062                 {
1063                         var btypes = ec.BuiltinTypes;
1064
1065                         if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
1066                                 Arguments args = new Arguments (1);
1067                                 args.Add (new Argument (source));
1068                                 return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, loc).Resolve (ec);
1069                         }
1070
1071                         Expression converted;
1072
1073                         using (ec.Set (ResolveContext.Options.CheckedScope)) {
1074                                 converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
1075                                 if (converted == null)
1076                                         converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
1077                                 if (converted == null)
1078                                         converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
1079                                 if (converted == null)
1080                                         converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);
1081
1082                                 if (converted == null) {
1083                                         source.Error_ValueCannotBeConverted (ec, btypes.Int, false);
1084                                         return null;
1085                                 }
1086                         }
1087
1088                         if (pointerArray)
1089                                 return converted;
1090
1091                         //
1092                         // Only positive constants are allowed at compile time
1093                         //
1094                         Constant c = converted as Constant;
1095                         if (c != null && c.IsNegative)
1096                                 Error_NegativeArrayIndex (ec, source.loc);
1097
1098                         // No conversion needed to array index
1099                         if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
1100                                 return converted;
1101
1102                         return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
1103                 }
1104
1105                 //
1106                 // Derived classes implement this method by cloning the fields that
1107                 // could become altered during the Resolve stage
1108                 //
1109                 // Only expressions that are created for the parser need to implement
1110                 // this.
1111                 //
1112                 protected virtual void CloneTo (CloneContext clonectx, Expression target)
1113                 {
1114                         throw new NotImplementedException (
1115                                 String.Format (
1116                                         "CloneTo not implemented for expression {0}", this.GetType ()));
1117                 }
1118
1119                 //
1120                 // Clones an expression created by the parser.
1121                 //
1122                 // We only support expressions created by the parser so far, not
1123                 // expressions that have been resolved (many more classes would need
1124                 // to implement CloneTo).
1125                 //
1126                 // This infrastructure is here merely for Lambda expressions which
1127                 // compile the same code using different type values for the same
1128                 // arguments to find the correct overload
1129                 //
1130                 public virtual Expression Clone (CloneContext clonectx)
1131                 {
1132                         Expression cloned = (Expression) MemberwiseClone ();
1133                         CloneTo (clonectx, cloned);
1134
1135                         return cloned;
1136                 }
1137
1138                 //
1139                 // Implementation of expression to expression tree conversion
1140                 //
1141                 public abstract Expression CreateExpressionTree (ResolveContext ec);
1142
1143                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
1144                 {
1145                         return CreateExpressionFactoryCall (ec, name, null, args, loc);
1146                 }
1147
1148                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
1149                 {
1150                         return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
1151                 }
1152
1153                 public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
1154                 {
1155                         return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
1156                 }
1157
1158                 protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
1159                 {
1160                         var t = ec.Module.PredefinedTypes.Expression.Resolve ();
1161                         if (t == null)
1162                                 return null;
1163
1164                         return new TypeExpression (t, loc);
1165                 }
1166
1167                 //
1168                 // Implemented by all expressions which support conversion from
1169                 // compiler expression to invokable runtime expression. Used by
1170                 // dynamic C# binder.
1171                 //
1172                 public virtual SLE.Expression MakeExpression (BuilderContext ctx)
1173                 {
1174                         throw new NotImplementedException ("MakeExpression for " + GetType ());
1175                 }
1176
1177                 public virtual object Accept (StructuralVisitor visitor)
1178                 {
1179                         return visitor.Visit (this);
1180                 }
1181         }
1182
1183         /// <summary>
1184         ///   This is just a base class for expressions that can
1185         ///   appear on statements (invocations, object creation,
1186         ///   assignments, post/pre increment and decrement).  The idea
1187         ///   being that they would support an extra Emition interface that
1188         ///   does not leave a result on the stack.
1189         /// </summary>
1190         public abstract class ExpressionStatement : Expression
1191         {
1192                 public virtual void MarkReachable (Reachability rc)
1193                 {
1194                 }
1195
1196                 public ExpressionStatement ResolveStatement (BlockContext ec)
1197                 {
1198                         Expression e = Resolve (ec);
1199                         if (e == null)
1200                                 return null;
1201
1202                         ExpressionStatement es = e as ExpressionStatement;
1203                         if (es == null || e is AnonymousMethodBody)
1204                                 Error_InvalidExpressionStatement (ec);
1205
1206                         //
1207                         // This is quite expensive warning, try to limit the damage
1208                         //
1209                         if (MemberAccess.IsValidDotExpression (e.Type) && !(e is Assign || e is Await)) {
1210                                 WarningAsyncWithoutWait (ec, e);
1211                         }
1212
1213                         return es;
1214                 }
1215
1216                 static void WarningAsyncWithoutWait (BlockContext bc, Expression e)
1217                 {
1218                         if (bc.CurrentAnonymousMethod is AsyncInitializer) {
1219                                 var awaiter = new AwaitStatement.AwaitableMemberAccess (e) {
1220                                         ProbingMode = true
1221                                 };
1222
1223                                 //
1224                                 // Need to do full resolve because GetAwaiter can be extension method
1225                                 // available only in this context
1226                                 //
1227                                 var mg = awaiter.Resolve (bc) as MethodGroupExpr;
1228                                 if (mg == null)
1229                                         return;
1230
1231                                 var arguments = new Arguments (0);
1232                                 mg = mg.OverloadResolve (bc, ref arguments, null, OverloadResolver.Restrictions.ProbingOnly);
1233                                 if (mg == null)
1234                                         return;
1235
1236                                 //
1237                                 // Use same check rules as for real await
1238                                 //
1239                                 var awaiter_definition = bc.Module.GetAwaiter (mg.BestCandidateReturnType);
1240                                 if (!awaiter_definition.IsValidPattern || !awaiter_definition.INotifyCompletion)
1241                                         return;
1242
1243                                 bc.Report.Warning (4014, 1, e.Location,
1244                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator");
1245                                 return;
1246                         }
1247
1248                         var inv = e as Invocation;
1249                         if (inv != null && inv.MethodGroup != null && inv.MethodGroup.BestCandidate.IsAsync) {
1250                                 // The warning won't be reported for imported methods to maintain warning compatiblity with csc
1251                                 bc.Report.Warning (4014, 1, e.Location,
1252                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator or calling `Wait' method");
1253                                 return;
1254                         }
1255                 }
1256
1257                 /// <summary>
1258                 ///   Requests the expression to be emitted in a `statement'
1259                 ///   context.  This means that no new value is left on the
1260                 ///   stack after invoking this method (constrasted with
1261                 ///   Emit that will always leave a value on the stack).
1262                 /// </summary>
1263                 public abstract void EmitStatement (EmitContext ec);
1264
1265                 public override void EmitSideEffect (EmitContext ec)
1266                 {
1267                         EmitStatement (ec);
1268                 }
1269         }
1270
1271         /// <summary>
1272         ///   This kind of cast is used to encapsulate the child
1273         ///   whose type is child.Type into an expression that is
1274         ///   reported to return "return_type".  This is used to encapsulate
1275         ///   expressions which have compatible types, but need to be dealt
1276         ///   at higher levels with.
1277         ///
1278         ///   For example, a "byte" expression could be encapsulated in one
1279         ///   of these as an "unsigned int".  The type for the expression
1280         ///   would be "unsigned int".
1281         ///
1282         /// </summary>
1283         public abstract class TypeCast : Expression
1284         {
1285                 protected readonly Expression child;
1286
1287                 protected TypeCast (Expression child, TypeSpec return_type)
1288                 {
1289                         eclass = child.eclass;
1290                         loc = child.Location;
1291                         type = return_type;
1292                         this.child = child;
1293                 }
1294
1295                 public Expression Child {
1296                         get {
1297                                 return child;
1298                         }
1299                 }
1300
1301                 public override bool ContainsEmitWithAwait ()
1302                 {
1303                         return child.ContainsEmitWithAwait ();
1304                 }
1305
1306                 public override Expression CreateExpressionTree (ResolveContext ec)
1307                 {
1308                         Arguments args = new Arguments (2);
1309                         args.Add (new Argument (child.CreateExpressionTree (ec)));
1310                         args.Add (new Argument (new TypeOf (type, loc)));
1311
1312                         if (type.IsPointer || child.Type.IsPointer)
1313                                 Error_PointerInsideExpressionTree (ec);
1314
1315                         return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
1316                 }
1317
1318                 protected override Expression DoResolve (ResolveContext ec)
1319                 {
1320                         // This should never be invoked, we are born in fully
1321                         // initialized state.
1322
1323                         return this;
1324                 }
1325
1326                 public override void Emit (EmitContext ec)
1327                 {
1328                         child.Emit (ec);
1329                 }
1330
1331                 public override void FlowAnalysis (FlowAnalysisContext fc)
1332                 {
1333                         child.FlowAnalysis (fc);
1334                 }
1335
1336                 public override SLE.Expression MakeExpression (BuilderContext ctx)
1337                 {
1338 #if STATIC
1339                         return base.MakeExpression (ctx);
1340 #else
1341                         return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
1342                                 SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
1343                                 SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
1344 #endif
1345                 }
1346
1347                 protected override void CloneTo (CloneContext clonectx, Expression t)
1348                 {
1349                         // Nothing to clone
1350                 }
1351
1352                 public override bool IsNull {
1353                         get { return child.IsNull; }
1354                 }
1355         }
1356
1357         public class EmptyCast : TypeCast {
1358                 EmptyCast (Expression child, TypeSpec target_type)
1359                         : base (child, target_type)
1360                 {
1361                 }
1362
1363                 public static Expression Create (Expression child, TypeSpec type)
1364                 {
1365                         Constant c = child as Constant;
1366                         if (c != null) {
1367                                 var enum_constant = c as EnumConstant;
1368                                 if (enum_constant != null)
1369                                         c = enum_constant.Child;
1370
1371                                 if (!(c is ReducedExpression.ReducedConstantExpression)) {
1372                                         if (c.Type == type)
1373                                                 return c;
1374
1375                                         var res = c.ConvertImplicitly (type);
1376                                         if (res != null)
1377                                                 return res;
1378                                 }
1379                         }
1380
1381                         EmptyCast e = child as EmptyCast;
1382                         if (e != null)
1383                                 return new EmptyCast (e.child, type);
1384
1385                         return new EmptyCast (child, type);
1386                 }
1387
1388                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1389                 {
1390                         child.EmitBranchable (ec, label, on_true);
1391                 }
1392
1393                 public override void EmitSideEffect (EmitContext ec)
1394                 {
1395                         child.EmitSideEffect (ec);
1396                 }
1397         }
1398
1399         //
1400         // Used for predefined type user operator (no obsolete check, etc.)
1401         //
1402         public class OperatorCast : TypeCast
1403         {
1404                 readonly MethodSpec conversion_operator;
1405
1406                 public OperatorCast (Expression expr, TypeSpec target_type)
1407                         : this (expr, target_type, target_type, false)
1408                 {
1409                 }
1410
1411                 public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
1412                         : this (expr, target_type, target_type, find_explicit)
1413                 {
1414                 }
1415
1416                 public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
1417                         : base (expr, returnType)
1418                 {
1419                         var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
1420                         var mi = MemberCache.GetUserOperator (declaringType, op, true);
1421
1422                         if (mi != null) {
1423                                 foreach (MethodSpec oper in mi) {
1424                                         if (oper.ReturnType != returnType)
1425                                                 continue;
1426
1427                                         if (oper.Parameters.Types[0] == expr.Type) {
1428                                                 conversion_operator = oper;
1429                                                 return;
1430                                         }
1431                                 }
1432                         }
1433
1434                         throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
1435                                 returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
1436                 }
1437
1438                 public override void Emit (EmitContext ec)
1439                 {
1440                         child.Emit (ec);
1441                         ec.Emit (OpCodes.Call, conversion_operator);
1442                 }
1443         }
1444
1445         //
1446         // Constant specialization of EmptyCast.
1447         // We need to special case this since an empty cast of
1448         // a constant is still a constant.
1449         //
1450         public class EmptyConstantCast : Constant
1451         {
1452                 public readonly Constant child;
1453
1454                 public EmptyConstantCast (Constant child, TypeSpec type)
1455                         : base (child.Location)
1456                 {
1457                         if (child == null)
1458                                 throw new ArgumentNullException ("child");
1459
1460                         this.child = child;
1461                         this.eclass = child.eclass;
1462                         this.type = type;
1463                 }
1464
1465                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1466                 {
1467                         if (child.Type == target_type)
1468                                 return child;
1469
1470                         // FIXME: check that 'type' can be converted to 'target_type' first
1471                         return child.ConvertExplicitly (in_checked_context, target_type);
1472                 }
1473
1474                 public override Expression CreateExpressionTree (ResolveContext ec)
1475                 {
1476                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
1477                                 child.CreateExpressionTree (ec),
1478                                 new TypeOf (type, loc));
1479
1480                         if (type.IsPointer)
1481                                 Error_PointerInsideExpressionTree (ec);
1482
1483                         return CreateExpressionFactoryCall (ec, "Convert", args);
1484                 }
1485
1486                 public override bool IsDefaultValue {
1487                         get { return child.IsDefaultValue; }
1488                 }
1489
1490                 public override bool IsNegative {
1491                         get { return child.IsNegative; }
1492                 }
1493
1494                 public override bool IsNull {
1495                         get { return child.IsNull; }
1496                 }
1497
1498                 public override bool IsOneInteger {
1499                         get { return child.IsOneInteger; }
1500                 }
1501
1502                 public override bool IsSideEffectFree {
1503                         get {
1504                                 return child.IsSideEffectFree;
1505                         }
1506                 }
1507
1508                 public override bool IsZeroInteger {
1509                         get { return child.IsZeroInteger; }
1510                 }
1511
1512                 public override void Emit (EmitContext ec)
1513                 {
1514                         child.Emit (ec);
1515                 }
1516
1517                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1518                 {
1519                         child.EmitBranchable (ec, label, on_true);
1520
1521                         // Only to make verifier happy
1522                         if (TypeManager.IsGenericParameter (type) && child.IsNull)
1523                                 ec.Emit (OpCodes.Unbox_Any, type);
1524                 }
1525
1526                 public override void EmitSideEffect (EmitContext ec)
1527                 {
1528                         child.EmitSideEffect (ec);
1529                 }
1530
1531                 public override object GetValue ()
1532                 {
1533                         return child.GetValue ();
1534                 }
1535
1536                 public override string GetValueAsLiteral ()
1537                 {
1538                         return child.GetValueAsLiteral ();
1539                 }
1540
1541                 public override long GetValueAsLong ()
1542                 {
1543                         return child.GetValueAsLong ();
1544                 }
1545
1546                 public override Constant ConvertImplicitly (TypeSpec target_type)
1547                 {
1548                         if (type == target_type)
1549                                 return this;
1550
1551                         // FIXME: Do we need to check user conversions?
1552                         if (!Convert.ImplicitStandardConversionExists (this, target_type))
1553                                 return null;
1554
1555                         return child.ConvertImplicitly (target_type);
1556                 }
1557         }
1558
1559         /// <summary>
1560         ///  This class is used to wrap literals which belong inside Enums
1561         /// </summary>
1562         public class EnumConstant : Constant
1563         {
1564                 public Constant Child;
1565
1566                 public EnumConstant (Constant child, TypeSpec enum_type)
1567                         : base (child.Location)
1568                 {
1569                         this.Child = child;
1570
1571                         this.eclass = ExprClass.Value;
1572                         this.type = enum_type;
1573                 }
1574
1575                 protected EnumConstant (Location loc)
1576                         : base (loc)
1577                 {
1578                 }
1579
1580                 public override void Emit (EmitContext ec)
1581                 {
1582                         Child.Emit (ec);
1583                 }
1584
1585                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1586                 {
1587                         Child.EncodeAttributeValue (rc, enc, Child.Type);
1588                 }
1589
1590                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1591                 {
1592                         Child.EmitBranchable (ec, label, on_true);
1593                 }
1594
1595                 public override void EmitSideEffect (EmitContext ec)
1596                 {
1597                         Child.EmitSideEffect (ec);
1598                 }
1599
1600                 public override string GetSignatureForError()
1601                 {
1602                         return Type.GetSignatureForError ();
1603                 }
1604
1605                 public override object GetValue ()
1606                 {
1607                         return Child.GetValue ();
1608                 }
1609
1610 #if !STATIC
1611                 public override object GetTypedValue ()
1612                 {
1613                         //
1614                         // The method can be used in dynamic context only (on closed types)
1615                         //
1616                         // System.Enum.ToObject cannot be called on dynamic types
1617                         // EnumBuilder has to be used, but we cannot use EnumBuilder
1618                         // because it does not properly support generics
1619                         //
1620                         return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
1621                 }
1622 #endif
1623
1624                 public override string GetValueAsLiteral ()
1625                 {
1626                         return Child.GetValueAsLiteral ();
1627                 }
1628
1629                 public override long GetValueAsLong ()
1630                 {
1631                         return Child.GetValueAsLong ();
1632                 }
1633
1634                 public EnumConstant Increment()
1635                 {
1636                         return new EnumConstant (((IntegralConstant) Child).Increment (), type);
1637                 }
1638
1639                 public override bool IsDefaultValue {
1640                         get {
1641                                 return Child.IsDefaultValue;
1642                         }
1643                 }
1644
1645                 public override bool IsSideEffectFree {
1646                         get {
1647                                 return Child.IsSideEffectFree;
1648                         }
1649                 }
1650
1651                 public override bool IsZeroInteger {
1652                         get { return Child.IsZeroInteger; }
1653                 }
1654
1655                 public override bool IsNegative {
1656                         get {
1657                                 return Child.IsNegative;
1658                         }
1659                 }
1660
1661                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1662                 {
1663                         if (Child.Type == target_type)
1664                                 return Child;
1665
1666                         return Child.ConvertExplicitly (in_checked_context, target_type);
1667                 }
1668
1669                 public override Constant ConvertImplicitly (TypeSpec type)
1670                 {
1671                         if (this.type == type) {
1672                                 return this;
1673                         }
1674
1675                         if (!Convert.ImplicitStandardConversionExists (this, type)){
1676                                 return null;
1677                         }
1678
1679                         return Child.ConvertImplicitly (type);
1680                 }
1681         }
1682
1683         /// <summary>
1684         ///   This kind of cast is used to encapsulate Value Types in objects.
1685         ///
1686         ///   The effect of it is to box the value type emitted by the previous
1687         ///   operation.
1688         /// </summary>
1689         public class BoxedCast : TypeCast {
1690
1691                 public BoxedCast (Expression expr, TypeSpec target_type)
1692                         : base (expr, target_type)
1693                 {
1694                         eclass = ExprClass.Value;
1695                 }
1696
1697                 protected override Expression DoResolve (ResolveContext ec)
1698                 {
1699                         // This should never be invoked, we are born in fully
1700                         // initialized state.
1701
1702                         return this;
1703                 }
1704
1705                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1706                 {
1707                         // Only boxing to object type is supported
1708                         if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
1709                                 base.EncodeAttributeValue (rc, enc, targetType);
1710                                 return;
1711                         }
1712
1713                         enc.Encode (child.Type);
1714                         child.EncodeAttributeValue (rc, enc, child.Type);
1715                 }
1716
1717                 public override void Emit (EmitContext ec)
1718                 {
1719                         base.Emit (ec);
1720
1721                         ec.Emit (OpCodes.Box, child.Type);
1722                 }
1723
1724                 public override void EmitSideEffect (EmitContext ec)
1725                 {
1726                         // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
1727                         // so, we need to emit the box+pop instructions in most cases
1728                         if (child.Type.IsStruct &&
1729                             (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
1730                                 child.EmitSideEffect (ec);
1731                         else
1732                                 base.EmitSideEffect (ec);
1733                 }
1734         }
1735
1736         public class UnboxCast : TypeCast {
1737                 public UnboxCast (Expression expr, TypeSpec return_type)
1738                         : base (expr, return_type)
1739                 {
1740                 }
1741
1742                 protected override Expression DoResolve (ResolveContext ec)
1743                 {
1744                         // This should never be invoked, we are born in fully
1745                         // initialized state.
1746
1747                         return this;
1748                 }
1749
1750                 public override void Emit (EmitContext ec)
1751                 {
1752                         base.Emit (ec);
1753
1754                         ec.Emit (OpCodes.Unbox_Any, type);
1755                 }
1756         }
1757
1758         /// <summary>
1759         ///   This is used to perform explicit numeric conversions.
1760         ///
1761         ///   Explicit numeric conversions might trigger exceptions in a checked
1762         ///   context, so they should generate the conv.ovf opcodes instead of
1763         ///   conv opcodes.
1764         /// </summary>
1765         public class ConvCast : TypeCast {
1766                 public enum Mode : byte {
1767                         I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
1768                         U1_I1, U1_CH,
1769                         I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
1770                         U2_I1, U2_U1, U2_I2, U2_CH,
1771                         I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
1772                         U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
1773                         I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
1774                         U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
1775                         CH_I1, CH_U1, CH_I2,
1776                         R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
1777                         R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
1778                         I_I8,
1779                 }
1780
1781                 Mode mode;
1782
1783                 public ConvCast (Expression child, TypeSpec return_type, Mode m)
1784                         : base (child, return_type)
1785                 {
1786                         mode = m;
1787                 }
1788
1789                 protected override Expression DoResolve (ResolveContext ec)
1790                 {
1791                         // This should never be invoked, we are born in fully
1792                         // initialized state.
1793
1794                         return this;
1795                 }
1796
1797                 public override string ToString ()
1798                 {
1799                         return String.Format ("ConvCast ({0}, {1})", mode, child);
1800                 }
1801
1802                 public override void Emit (EmitContext ec)
1803                 {
1804                         base.Emit (ec);
1805                         Emit (ec, mode);
1806                 }
1807
1808                 public static void Emit (EmitContext ec, Mode mode)
1809                 {
1810                         if (ec.HasSet (EmitContext.Options.CheckedScope)) {
1811                                 switch (mode){
1812                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1813                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1814                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1815                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1816                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1817
1818                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1819                                 case Mode.U1_CH: /* nothing */ break;
1820
1821                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1822                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1823                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1824                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1825                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1826                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1827
1828                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1829                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1830                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1831                                 case Mode.U2_CH: /* nothing */ break;
1832
1833                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1834                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1835                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1836                                 case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1837                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1838                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1839                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1840
1841                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1842                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1843                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1844                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1845                                 case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1846                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1847
1848                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1849                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1850                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1851                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1852                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1853                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1854                                 case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1855                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1856                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;
1857
1858                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1859                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1860                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1861                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1862                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1863                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
1864                                 case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1865                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1866                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;
1867
1868                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1869                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1870                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1871
1872                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1873                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1874                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1875                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1876                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1877                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1878                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1879                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1880                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1881
1882                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1883                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1884                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1885                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1886                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1887                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1888                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1889                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1890                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1891                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1892
1893                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1894                                 }
1895                         } else {
1896                                 switch (mode){
1897                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
1898                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
1899                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
1900                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
1901                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;
1902
1903                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
1904                                 case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;
1905
1906                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
1907                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
1908                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
1909                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
1910                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
1911                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;
1912
1913                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
1914                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
1915                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
1916                                 case Mode.U2_CH: /* nothing */ break;
1917
1918                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
1919                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
1920                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
1921                                 case Mode.I4_U4: /* nothing */ break;
1922                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_U2); break;
1923                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_I8); break;
1924                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_U2); break;
1925
1926                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_I1); break;
1927                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_U1); break;
1928                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_I2); break;
1929                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_U2); break;
1930                                 case Mode.U4_I4: /* nothing */ break;
1931                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_U2); break;
1932
1933                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_I1); break;
1934                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_U1); break;
1935                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_I2); break;
1936                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_U2); break;
1937                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_I4); break;
1938                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_U4); break;
1939                                 case Mode.I8_U8: /* nothing */ break;
1940                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_U2); break;
1941                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_U); break;
1942
1943                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_I1); break;
1944                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_U1); break;
1945                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_I2); break;
1946                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_U2); break;
1947                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_I4); break;
1948                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_U4); break;
1949                                 case Mode.U8_I8: /* nothing */ break;
1950                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_U2); break;
1951                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_U); break;
1952
1953                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_I1); break;
1954                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_U1); break;
1955                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_I2); break;
1956
1957                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_I1); break;
1958                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_U1); break;
1959                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_I2); break;
1960                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_U2); break;
1961                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_I4); break;
1962                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_U4); break;
1963                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_I8); break;
1964                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_U8); break;
1965                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_U2); break;
1966
1967                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_I1); break;
1968                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_U1); break;
1969                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_I2); break;
1970                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_U2); break;
1971                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_I4); break;
1972                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_U4); break;
1973                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_I8); break;
1974                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_U8); break;
1975                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_U2); break;
1976                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1977
1978                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_U8); break;
1979                                 }
1980                         }
1981                 }
1982         }
1983
1984         class OpcodeCast : TypeCast
1985         {
1986                 readonly OpCode op;
1987
1988                 public OpcodeCast (Expression child, TypeSpec return_type, OpCode op)
1989                         : base (child, return_type)
1990                 {
1991                         this.op = op;
1992                 }
1993
1994                 protected override Expression DoResolve (ResolveContext ec)
1995                 {
1996                         // This should never be invoked, we are born in fully
1997                         // initialized state.
1998
1999                         return this;
2000                 }
2001
2002                 public override void Emit (EmitContext ec)
2003                 {
2004                         base.Emit (ec);
2005                         ec.Emit (op);
2006                 }
2007
2008                 public TypeSpec UnderlyingType {
2009                         get { return child.Type; }
2010                 }
2011         }
2012
2013         //
2014         // Opcode casts expression with 2 opcodes but only
2015         // single expression tree node
2016         //
2017         class OpcodeCastDuplex : OpcodeCast
2018         {
2019                 readonly OpCode second;
2020
2021                 public OpcodeCastDuplex (Expression child, TypeSpec returnType, OpCode first, OpCode second)
2022                         : base (child, returnType, first)
2023                 {
2024                         this.second = second;
2025                 }
2026
2027                 public override void Emit (EmitContext ec)
2028                 {
2029                         base.Emit (ec);
2030                         ec.Emit (second);
2031                 }
2032         }
2033
2034         /// <summary>
2035         ///   This kind of cast is used to encapsulate a child and cast it
2036         ///   to the class requested
2037         /// </summary>
2038         public sealed class ClassCast : TypeCast {
2039                 readonly bool forced;
2040
2041                 public ClassCast (Expression child, TypeSpec return_type)
2042                         : base (child, return_type)
2043                 {
2044                 }
2045
2046                 public ClassCast (Expression child, TypeSpec return_type, bool forced)
2047                         : base (child, return_type)
2048                 {
2049                         this.forced = forced;
2050                 }
2051
2052                 public override void Emit (EmitContext ec)
2053                 {
2054                         base.Emit (ec);
2055
2056                         bool gen = TypeManager.IsGenericParameter (child.Type);
2057                         if (gen)
2058                                 ec.Emit (OpCodes.Box, child.Type);
2059
2060                         if (type.IsGenericParameter) {
2061                                 ec.Emit (OpCodes.Unbox_Any, type);
2062                                 return;
2063                         }
2064
2065                         if (gen && !forced)
2066                                 return;
2067
2068                         ec.Emit (OpCodes.Castclass, type);
2069                 }
2070         }
2071
2072         //
2073         // Created during resolving pahse when an expression is wrapped or constantified
2074         // and original expression can be used later (e.g. for expression trees)
2075         //
2076         public class ReducedExpression : Expression
2077         {
2078                 public sealed class ReducedConstantExpression : EmptyConstantCast
2079                 {
2080                         readonly Expression orig_expr;
2081
2082                         public ReducedConstantExpression (Constant expr, Expression orig_expr)
2083                                 : base (expr, expr.Type)
2084                         {
2085                                 this.orig_expr = orig_expr;
2086                         }
2087
2088                         public Expression OriginalExpression {
2089                                 get {
2090                                         return orig_expr;
2091                                 }
2092                         }
2093
2094                         public override Constant ConvertImplicitly (TypeSpec target_type)
2095                         {
2096                                 Constant c = base.ConvertImplicitly (target_type);
2097                                 if (c != null)
2098                                         c = new ReducedConstantExpression (c, orig_expr);
2099
2100                                 return c;
2101                         }
2102
2103                         public override Expression CreateExpressionTree (ResolveContext ec)
2104                         {
2105                                 return orig_expr.CreateExpressionTree (ec);
2106                         }
2107
2108                         public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
2109                         {
2110                                 Constant c = base.ConvertExplicitly (in_checked_context, target_type);
2111                                 if (c != null)
2112                                         c = new ReducedConstantExpression (c, orig_expr);
2113                                 return c;
2114                         }
2115
2116                         public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
2117                         {
2118                                 //
2119                                 // LAMESPEC: Reduced conditional expression is allowed as an attribute argument
2120                                 //
2121                                 if (orig_expr is Conditional)
2122                                         child.EncodeAttributeValue (rc, enc, targetType);
2123                                 else
2124                                         base.EncodeAttributeValue (rc, enc, targetType);
2125                         }
2126                 }
2127
2128                 sealed class ReducedExpressionStatement : ExpressionStatement
2129                 {
2130                         readonly Expression orig_expr;
2131                         readonly ExpressionStatement stm;
2132
2133                         public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
2134                         {
2135                                 this.orig_expr = orig;
2136                                 this.stm = stm;
2137                                 this.eclass = stm.eclass;
2138                                 this.type = stm.Type;
2139
2140                                 this.loc = orig.Location;
2141                         }
2142
2143                         public override bool ContainsEmitWithAwait ()
2144                         {
2145                                 return stm.ContainsEmitWithAwait ();
2146                         }
2147
2148                         public override Expression CreateExpressionTree (ResolveContext ec)
2149                         {
2150                                 return orig_expr.CreateExpressionTree (ec);
2151                         }
2152
2153                         protected override Expression DoResolve (ResolveContext ec)
2154                         {
2155                                 return this;
2156                         }
2157
2158                         public override void Emit (EmitContext ec)
2159                         {
2160                                 stm.Emit (ec);
2161                         }
2162
2163                         public override void EmitStatement (EmitContext ec)
2164                         {
2165                                 stm.EmitStatement (ec);
2166                         }
2167
2168                         public override void FlowAnalysis (FlowAnalysisContext fc)
2169                         {
2170                                 stm.FlowAnalysis (fc);
2171                         }
2172                 }
2173
2174                 readonly Expression expr, orig_expr;
2175
2176                 private ReducedExpression (Expression expr, Expression orig_expr)
2177                 {
2178                         this.expr = expr;
2179                         this.eclass = expr.eclass;
2180                         this.type = expr.Type;
2181                         this.orig_expr = orig_expr;
2182                         this.loc = orig_expr.Location;
2183                 }
2184
2185                 #region Properties
2186
2187                 public override bool IsSideEffectFree {
2188                         get {
2189                                 return expr.IsSideEffectFree;
2190                         }
2191                 }
2192
2193                 public Expression OriginalExpression {
2194                         get {
2195                                 return orig_expr;
2196                         }
2197                 }
2198
2199                 #endregion
2200
2201                 public override bool ContainsEmitWithAwait ()
2202                 {
2203                         return expr.ContainsEmitWithAwait ();
2204                 }
2205
2206                 //
2207                 // Creates fully resolved expression switcher
2208                 //
2209                 public static Constant Create (Constant expr, Expression original_expr)
2210                 {
2211                         if (expr.eclass == ExprClass.Unresolved)
2212                                 throw new ArgumentException ("Unresolved expression");
2213
2214                         return new ReducedConstantExpression (expr, original_expr);
2215                 }
2216
2217                 public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
2218                 {
2219                         return new ReducedExpressionStatement (s, orig);
2220                 }
2221
2222                 public static Expression Create (Expression expr, Expression original_expr)
2223                 {
2224                         return Create (expr, original_expr, true);
2225                 }
2226
2227                 //
2228                 // Creates unresolved reduce expression. The original expression has to be
2229                 // already resolved. Created expression is constant based based on `expr'
2230                 // value unless canBeConstant is used
2231                 //
2232                 public static Expression Create (Expression expr, Expression original_expr, bool canBeConstant)
2233                 {
2234                         if (canBeConstant) {
2235                                 Constant c = expr as Constant;
2236                                 if (c != null)
2237                                         return Create (c, original_expr);
2238                         }
2239
2240                         ExpressionStatement s = expr as ExpressionStatement;
2241                         if (s != null)
2242                                 return Create (s, original_expr);
2243
2244                         if (expr.eclass == ExprClass.Unresolved)
2245                                 throw new ArgumentException ("Unresolved expression");
2246
2247                         return new ReducedExpression (expr, original_expr);
2248                 }
2249
2250                 public override Expression CreateExpressionTree (ResolveContext ec)
2251                 {
2252                         return orig_expr.CreateExpressionTree (ec);
2253                 }
2254
2255                 protected override Expression DoResolve (ResolveContext ec)
2256                 {
2257                         return this;
2258                 }
2259
2260                 public override void Emit (EmitContext ec)
2261                 {
2262                         expr.Emit (ec);
2263                 }
2264
2265                 public override Expression EmitToField (EmitContext ec)
2266                 {
2267                         return expr.EmitToField(ec);
2268                 }
2269
2270                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2271                 {
2272                         expr.EmitBranchable (ec, target, on_true);
2273                 }
2274
2275                 public override void FlowAnalysis (FlowAnalysisContext fc)
2276                 {
2277                         expr.FlowAnalysis (fc);
2278                 }
2279
2280                 public override SLE.Expression MakeExpression (BuilderContext ctx)
2281                 {
2282                         return orig_expr.MakeExpression (ctx);
2283                 }
2284         }
2285
2286         //
2287         // Standard composite pattern
2288         //
2289         public abstract class CompositeExpression : Expression
2290         {
2291                 protected Expression expr;
2292
2293                 protected CompositeExpression (Expression expr)
2294                 {
2295                         this.expr = expr;
2296                         this.loc = expr.Location;
2297                 }
2298
2299                 public override bool ContainsEmitWithAwait ()
2300                 {
2301                         return expr.ContainsEmitWithAwait ();
2302                 }
2303
2304                 public override Expression CreateExpressionTree (ResolveContext rc)
2305                 {
2306                         return expr.CreateExpressionTree (rc);
2307                 }
2308
2309                 public Expression Child {
2310                         get { return expr; }
2311                 }
2312
2313                 protected override Expression DoResolve (ResolveContext rc)
2314                 {
2315                         expr = expr.Resolve (rc);
2316                         if (expr == null)
2317                                 return null;
2318
2319                         type = expr.Type;
2320                         eclass = expr.eclass;
2321                         return this;
2322                 }
2323
2324                 public override void Emit (EmitContext ec)
2325                 {
2326                         expr.Emit (ec);
2327                 }
2328
2329                 public override bool IsNull {
2330                         get { return expr.IsNull; }
2331                 }
2332         }
2333
2334         //
2335         // Base of expressions used only to narrow resolve flow
2336         //
2337         public abstract class ShimExpression : Expression
2338         {
2339                 protected Expression expr;
2340
2341                 protected ShimExpression (Expression expr)
2342                 {
2343                         this.expr = expr;
2344                 }
2345
2346                 public Expression Expr {
2347                         get {
2348                                 return expr;
2349                         }
2350                 }
2351
2352                 protected override void CloneTo (CloneContext clonectx, Expression t)
2353                 {
2354                         if (expr == null)
2355                                 return;
2356
2357                         ShimExpression target = (ShimExpression) t;
2358                         target.expr = expr.Clone (clonectx);
2359                 }
2360
2361                 public override bool ContainsEmitWithAwait ()
2362                 {
2363                         return expr.ContainsEmitWithAwait ();
2364                 }
2365
2366                 public override Expression CreateExpressionTree (ResolveContext ec)
2367                 {
2368                         throw new NotSupportedException ("ET");
2369                 }
2370
2371                 public override void Emit (EmitContext ec)
2372                 {
2373                         throw new InternalErrorException ("Missing Resolve call");
2374                 }
2375         }
2376
2377         public class UnreachableExpression : Expression
2378         {
2379                 public UnreachableExpression (Expression expr)
2380                 {
2381                         this.loc = expr.Location;
2382                 }
2383
2384                 public override Expression CreateExpressionTree (ResolveContext ec)
2385                 {
2386                         // TODO: is it ok
2387                         throw new NotImplementedException ();
2388                 }
2389
2390                 protected override Expression DoResolve (ResolveContext rc)
2391                 {
2392                         throw new NotSupportedException ();
2393                 }
2394
2395                 public override void FlowAnalysis (FlowAnalysisContext fc)
2396                 {
2397                         fc.Report.Warning (429, 4, loc, "Unreachable expression code detected");
2398                 }
2399
2400                 public override void Emit (EmitContext ec)
2401                 {
2402                 }
2403
2404                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2405                 {
2406                 }
2407         }
2408
2409         //
2410         // Unresolved type name expressions
2411         //
2412         public abstract class ATypeNameExpression : FullNamedExpression
2413         {
2414                 string name;
2415                 protected TypeArguments targs;
2416
2417                 protected ATypeNameExpression (string name, Location l)
2418                 {
2419                         this.name = name;
2420                         loc = l;
2421                 }
2422
2423                 protected ATypeNameExpression (string name, TypeArguments targs, Location l)
2424                 {
2425                         this.name = name;
2426                         this.targs = targs;
2427                         loc = l;
2428                 }
2429
2430                 protected ATypeNameExpression (string name, int arity, Location l)
2431                         : this (name, new UnboundTypeArguments (arity), l)
2432                 {
2433                 }
2434
2435                 #region Properties
2436
2437                 protected int Arity {
2438                         get {
2439                                 return targs == null ? 0 : targs.Count;
2440                         }
2441                 }
2442
2443                 public bool HasTypeArguments {
2444                         get {
2445                                 return targs != null && !targs.IsEmpty;
2446                         }
2447                 }
2448
2449                 public string Name {
2450                         get {
2451                                 return name;
2452                         }
2453                         set {
2454                                 name = value;
2455                         }
2456                 }
2457
2458                 public TypeArguments TypeArguments {
2459                         get {
2460                                 return targs;
2461                         }
2462                 }
2463
2464                 #endregion
2465
2466                 public override bool Equals (object obj)
2467                 {
2468                         ATypeNameExpression atne = obj as ATypeNameExpression;
2469                         return atne != null && atne.Name == Name &&
2470                                 (targs == null || targs.Equals (atne.targs));
2471                 }
2472
2473                 public override int GetHashCode ()
2474                 {
2475                         return Name.GetHashCode ();
2476                 }
2477
2478                 // TODO: Move it to MemberCore
2479                 public static string GetMemberType (MemberCore mc)
2480                 {
2481                         if (mc is Property)
2482                                 return "property";
2483                         if (mc is Indexer)
2484                                 return "indexer";
2485                         if (mc is FieldBase)
2486                                 return "field";
2487                         if (mc is MethodCore)
2488                                 return "method";
2489                         if (mc is EnumMember)
2490                                 return "enum";
2491                         if (mc is Event)
2492                                 return "event";
2493
2494                         return "type";
2495                 }
2496
2497                 public override string GetSignatureForError ()
2498                 {
2499                         if (targs != null) {
2500                                 return Name + "<" + targs.GetSignatureForError () + ">";
2501                         }
2502
2503                         return Name;
2504                 }
2505
2506                 public abstract Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restriction);
2507         }
2508
2509         /// <summary>
2510         ///   SimpleName expressions are formed of a single word and only happen at the beginning
2511         ///   of a dotted-name.
2512         /// </summary>
2513         public class SimpleName : ATypeNameExpression
2514         {
2515                 public SimpleName (string name, Location l)
2516                         : base (name, l)
2517                 {
2518                 }
2519
2520                 public SimpleName (string name, TypeArguments args, Location l)
2521                         : base (name, args, l)
2522                 {
2523                 }
2524
2525                 public SimpleName (string name, int arity, Location l)
2526                         : base (name, arity, l)
2527                 {
2528                 }
2529
2530                 public SimpleName GetMethodGroup ()
2531                 {
2532                         return new SimpleName (Name, targs, loc);
2533                 }
2534
2535                 protected override Expression DoResolve (ResolveContext rc)
2536                 {
2537                         return SimpleNameResolve (rc, null);
2538                 }
2539
2540                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
2541                 {
2542                         return SimpleNameResolve (ec, right_side);
2543                 }
2544
2545                 protected virtual void Error_TypeOrNamespaceNotFound (IMemberContext ctx)
2546                 {
2547                         if (ctx.CurrentType != null) {
2548                                 var member = MemberLookup (ctx, false, ctx.CurrentType, Name, 0, MemberLookupRestrictions.ExactArity, loc) as MemberExpr;
2549                                 if (member != null) {
2550                                         Error_UnexpectedKind (ctx, member, "type", member.KindName, loc);
2551                                         return;
2552                                 }
2553                         }
2554
2555                         var report = ctx.Module.Compiler.Report;
2556
2557                         var retval = ctx.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2558                         if (retval != null) {
2559                                 report.SymbolRelatedToPreviousError (retval.Type);
2560                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
2561                                 return;
2562                         }
2563
2564                         retval = ctx.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2565                         if (retval != null) {
2566                                 Error_TypeArgumentsCannotBeUsed (ctx, retval.Type, loc);
2567                                 return;
2568                         }
2569
2570                         var ns_candidates = ctx.Module.GlobalRootNamespace.FindTypeNamespaces (ctx, Name, Arity);
2571                         if (ns_candidates != null) {
2572                                 if (ctx is UsingAliasNamespace.AliasContext) {
2573                                         report.Error (246, loc,
2574                                                 "The type or namespace name `{1}' could not be found. Consider using fully qualified name `{0}.{1}'",
2575                                                 ns_candidates[0], Name);
2576                                 } else {
2577                                         string usings = string.Join ("' or `", ns_candidates.ToArray ());
2578                                         report.Error (246, loc,
2579                                                 "The type or namespace name `{0}' could not be found. Are you missing `{1}' using directive?",
2580                                                 Name, usings);
2581                                 }
2582                         } else {
2583                                 report.Error (246, loc,
2584                                         "The type or namespace name `{0}' could not be found. Are you missing an assembly reference?",
2585                                         Name);
2586                         }
2587                 }
2588
2589                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2590                 {
2591                         FullNamedExpression fne = mc.LookupNamespaceOrType (Name, Arity, LookupMode.Normal, loc);
2592
2593                         if (fne != null) {
2594                                 if (fne.Type != null && Arity > 0) {
2595                                         if (HasTypeArguments) {
2596                                                 GenericTypeExpr ct = new GenericTypeExpr (fne.Type, targs, loc);
2597                                                 if (ct.ResolveAsType (mc) == null)
2598                                                         return null;
2599
2600                                                 return ct;
2601                                         }
2602
2603                                         return new GenericOpenTypeExpr (fne.Type, loc);
2604                                 }
2605
2606                                 //
2607                                 // dynamic namespace is ignored when dynamic is allowed (does not apply to types)
2608                                 //
2609                                 if (!(fne is NamespaceExpression))
2610                                         return fne;
2611                         }
2612
2613                         if (Arity == 0 && Name == "dynamic" && mc.Module.Compiler.Settings.Version > LanguageVersion.V_3) {
2614                                 if (!mc.Module.PredefinedAttributes.Dynamic.IsDefined) {
2615                                         mc.Module.Compiler.Report.Error (1980, Location,
2616                                                 "Dynamic keyword requires `{0}' to be defined. Are you missing System.Core.dll assembly reference?",
2617                                                 mc.Module.PredefinedAttributes.Dynamic.GetSignatureForError ());
2618                                 }
2619
2620                                 fne = new DynamicTypeExpr (loc);
2621                                 fne.ResolveAsType (mc);
2622                         }
2623
2624                         if (fne != null)
2625                                 return fne;
2626
2627                         Error_TypeOrNamespaceNotFound (mc);
2628                         return null;
2629                 }
2630
2631                 public bool IsPossibleTypeOrNamespace (IMemberContext mc)
2632                 {
2633                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
2634                 }
2635
2636                 public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
2637                 {
2638                         int lookup_arity = Arity;
2639                         bool errorMode = false;
2640                         Expression e;
2641                         Block current_block = rc.CurrentBlock;
2642                         INamedBlockVariable variable = null;
2643                         bool variable_found = false;
2644
2645                         while (true) {
2646                                 //
2647                                 // Stage 1: binding to local variables or parameters
2648                                 //
2649                                 // LAMESPEC: It should take invocableOnly into account but that would break csc compatibility
2650                                 //
2651                                 if (current_block != null && lookup_arity == 0) {
2652                                         if (current_block.ParametersBlock.TopBlock.GetLocalName (Name, current_block.Original, ref variable)) {
2653                                                 if (!variable.IsDeclared) {
2654                                                         // We found local name in accessible block but it's not
2655                                                         // initialized yet, maybe the user wanted to bind to something else
2656                                                         errorMode = true;
2657                                                         variable_found = true;
2658                                                 } else {
2659                                                         e = variable.CreateReferenceExpression (rc, loc);
2660                                                         if (e != null) {
2661                                                                 if (Arity > 0)
2662                                                                         Error_TypeArgumentsCannotBeUsed (rc, "variable", Name, loc);
2663
2664                                                                 return e;
2665                                                         }
2666                                                 }
2667                                         }
2668                                 }
2669
2670                                 //
2671                                 // Stage 2: Lookup members if we are inside a type up to top level type for nested types
2672                                 //
2673                                 TypeSpec member_type = rc.CurrentType;
2674                                 for (; member_type != null; member_type = member_type.DeclaringType) {
2675                                         e = MemberLookup (rc, errorMode, member_type, Name, lookup_arity, restrictions, loc);
2676                                         if (e == null)
2677                                                 continue;
2678
2679                                         var me = e as MemberExpr;
2680                                         if (me == null) {
2681                                                 // The name matches a type, defer to ResolveAsTypeStep
2682                                                 if (e is TypeExpr)
2683                                                         break;
2684
2685                                                 continue;
2686                                         }
2687
2688                                         if (errorMode) {
2689                                                 if (variable != null) {
2690                                                         if (me is FieldExpr || me is ConstantExpr || me is EventExpr || me is PropertyExpr) {
2691                                                                 rc.Report.Error (844, loc,
2692                                                                         "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the member `{1}'",
2693                                                                         Name, me.GetSignatureForError ());
2694                                                         } else {
2695                                                                 break;
2696                                                         }
2697                                                 } else if (me is MethodGroupExpr || me is PropertyExpr || me is IndexerExpr) {
2698                                                         // Leave it to overload resolution to report correct error
2699                                                 } else {
2700                                                         // TODO: rc.Report.SymbolRelatedToPreviousError ()
2701                                                         ErrorIsInaccesible (rc, me.GetSignatureForError (), loc);
2702                                                 }
2703                                         } else {
2704                                                 // LAMESPEC: again, ignores InvocableOnly
2705                                                 if (variable != null) {
2706                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2707                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2708                                                 }
2709
2710                                                 //
2711                                                 // MemberLookup does not check accessors availability, this is actually needed for properties only
2712                                                 //
2713                                                 var pe = me as PropertyExpr;
2714                                                 if (pe != null) {
2715
2716                                                         // Break as there is no other overload available anyway
2717                                                         if ((restrictions & MemberLookupRestrictions.ReadAccess) != 0) {
2718                                                                 if (!pe.PropertyInfo.HasGet || !pe.PropertyInfo.Get.IsAccessible (rc))
2719                                                                         break;
2720
2721                                                                 pe.Getter = pe.PropertyInfo.Get;
2722                                                         } else {
2723                                                                 if (!pe.PropertyInfo.HasSet || !pe.PropertyInfo.Set.IsAccessible (rc))
2724                                                                         break;
2725
2726                                                                 pe.Setter = pe.PropertyInfo.Set;
2727                                                         }
2728                                                 }
2729                                         }
2730
2731                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2732                                         // TODO: Should go to MemberAccess
2733                                         me = me.ResolveMemberAccess (rc, null, null);
2734
2735                                         if (Arity > 0) {
2736                                                 targs.Resolve (rc);
2737                                                 me.SetTypeArguments (rc, targs);
2738                                         }
2739
2740                                         return me;
2741                                 }
2742
2743                                 //
2744                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2745                                 //
2746                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2747                                         if (IsPossibleTypeOrNamespace (rc)) {
2748                                                 if (variable != null) {
2749                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2750                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2751                                                 }
2752
2753                                                 return ResolveAsTypeOrNamespace (rc);
2754                                         }
2755                                 }
2756
2757                                 if (errorMode) {
2758                                         if (variable_found) {
2759                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2760                                         } else {
2761                                                 if (Arity > 0) {
2762                                                         var tparams = rc.CurrentTypeParameters;
2763                                                         if (tparams != null) {
2764                                                                 if (tparams.Find (Name) != null) {
2765                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2766                                                                         return null;
2767                                                                 }
2768                                                         }
2769
2770                                                         var ct = rc.CurrentType;
2771                                                         do {
2772                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2773                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2774                                                                                 if (ctp.Name == Name) {
2775                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2776                                                                                         return null;
2777                                                                                 }
2778                                                                         }
2779                                                                 }
2780
2781                                                                 ct = ct.DeclaringType;
2782                                                         } while (ct != null);
2783                                                 }
2784
2785                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2786                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2787                                                         if (e != null) {
2788                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2789                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2790                                                                 return e;
2791                                                         }
2792                                                 } else {
2793                                                         var me = MemberLookup (rc, false, rc.CurrentType, Name, Arity, restrictions & ~MemberLookupRestrictions.InvocableOnly, loc) as MemberExpr;
2794                                                         if (me != null) {
2795                                                                 Error_UnexpectedKind (rc, me, "method group", me.KindName, loc);
2796                                                                 return ErrorExpression.Instance;
2797                                                         }
2798                                                 }
2799
2800                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2801                                                 if (e != null) {
2802                                                         if (e.Type.Arity != Arity) {
2803                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, loc);
2804                                                                 return e;
2805                                                         }
2806
2807                                                         if (e is TypeExpr) {
2808                                                                 // TypeExpression does not have correct location
2809                                                                 if (e is TypeExpression)
2810                                                                         e = new TypeExpression (e.Type, loc);
2811
2812                                                                 return e;
2813                                                         }
2814                                                 }
2815
2816                                                 rc.Report.Error (103, loc, "The name `{0}' does not exist in the current context", Name);
2817                                         }
2818
2819                                         return ErrorExpression.Instance;
2820                                 }
2821
2822                                 if (rc.Module.Evaluator != null) {
2823                                         var fi = rc.Module.Evaluator.LookupField (Name);
2824                                         if (fi != null)
2825                                                 return new FieldExpr (fi.Item1, loc);
2826                                 }
2827
2828                                 lookup_arity = 0;
2829                                 errorMode = true;
2830                         }
2831                 }
2832
2833                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side)
2834                 {
2835                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2836
2837                         if (e == null)
2838                                 return null;
2839
2840                         if (e is FullNamedExpression && e.eclass != ExprClass.Unresolved) {
2841                                 Error_UnexpectedKind (ec, e, "variable", e.ExprClassName, loc);
2842                                 return e;
2843                         }
2844
2845                         if (right_side != null) {
2846                                 e = e.ResolveLValue (ec, right_side);
2847                         } else {
2848                                 e = e.Resolve (ec);
2849                         }
2850
2851                         return e;
2852                 }
2853
2854                 public override object Accept (StructuralVisitor visitor)
2855                 {
2856                         return visitor.Visit (this);
2857                 }
2858         }
2859
2860         /// <summary>
2861         ///   Represents a namespace or a type.  The name of the class was inspired by
2862         ///   section 10.8.1 (Fully Qualified Names).
2863         /// </summary>
2864         public abstract class FullNamedExpression : Expression
2865         {
2866                 protected override void CloneTo (CloneContext clonectx, Expression target)
2867                 {
2868                         // Do nothing, most unresolved type expressions cannot be
2869                         // resolved to different type
2870                 }
2871
2872                 public override bool ContainsEmitWithAwait ()
2873                 {
2874                         return false;
2875                 }
2876
2877                 public override Expression CreateExpressionTree (ResolveContext ec)
2878                 {
2879                         throw new NotSupportedException ("ET");
2880                 }
2881
2882                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc);
2883
2884                 //
2885                 // This is used to resolve the expression as a type, a null
2886                 // value will be returned if the expression is not a type
2887                 // reference
2888                 //
2889                 public override TypeSpec ResolveAsType (IMemberContext mc)
2890                 {
2891                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc);
2892
2893                         if (fne == null)
2894                                 return null;
2895
2896                         TypeExpr te = fne as TypeExpr;
2897                         if (te == null) {
2898                                 Error_UnexpectedKind (mc, fne, "type", fne.ExprClassName, loc);
2899                                 return null;
2900                         }
2901
2902                         te.loc = loc;
2903
2904                         type = te.Type;
2905
2906                         var dep = type.GetMissingDependencies ();
2907                         if (dep != null) {
2908                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
2909                         }
2910
2911                         if (type.Kind == MemberKind.Void) {
2912                                 mc.Module.Compiler.Report.Error (673, loc, "System.Void cannot be used from C#. Consider using `void'");
2913                         }
2914
2915                         //
2916                         // Obsolete checks cannot be done when resolving base context as they
2917                         // require type dependencies to be set but we are in process of resolving them
2918                         //
2919                         if (!(mc is TypeDefinition.BaseContext) && !(mc is UsingAliasNamespace.AliasContext)) {
2920                                 ObsoleteAttribute obsolete_attr = type.GetAttributeObsolete ();
2921                                 if (obsolete_attr != null && !mc.IsObsolete) {
2922                                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location, mc.Module.Compiler.Report);
2923                                 }
2924                         }
2925
2926                         return type;
2927                 }
2928
2929
2930                 public override void Emit (EmitContext ec)
2931                 {
2932                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
2933                                 GetSignatureForError ());
2934                 }
2935         }
2936
2937         /// <summary>
2938         ///   Expression that evaluates to a type
2939         /// </summary>
2940         public abstract class TypeExpr : FullNamedExpression
2941         {
2942                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2943                 {
2944                         ResolveAsType (mc);
2945                         return this;
2946                 }
2947
2948                 protected sealed override Expression DoResolve (ResolveContext ec)
2949                 {
2950                         ResolveAsType (ec);
2951                         return this;
2952                 }
2953
2954                 public override bool Equals (object obj)
2955                 {
2956                         TypeExpr tobj = obj as TypeExpr;
2957                         if (tobj == null)
2958                                 return false;
2959
2960                         return Type == tobj.Type;
2961                 }
2962
2963                 public override int GetHashCode ()
2964                 {
2965                         return Type.GetHashCode ();
2966                 }
2967         }
2968
2969         /// <summary>
2970         ///   Fully resolved Expression that already evaluated to a type
2971         /// </summary>
2972         public class TypeExpression : TypeExpr
2973         {
2974                 public TypeExpression (TypeSpec t, Location l)
2975                 {
2976                         Type = t;
2977                         eclass = ExprClass.Type;
2978                         loc = l;
2979                 }
2980
2981                 public sealed override TypeSpec ResolveAsType (IMemberContext ec)
2982                 {
2983                         return type;
2984                 }
2985         }
2986
2987         public class NamespaceExpression : FullNamedExpression
2988         {
2989                 readonly Namespace ns;
2990
2991                 public NamespaceExpression (Namespace ns, Location loc)
2992                 {
2993                         this.ns = ns;
2994                         this.Type = InternalType.Namespace;
2995                         this.eclass = ExprClass.Namespace;
2996                         this.loc = loc;
2997                 }
2998
2999                 public Namespace Namespace {
3000                         get {
3001                                 return ns;
3002                         }
3003                 }
3004
3005                 protected override Expression DoResolve (ResolveContext rc)
3006                 {
3007                         throw new NotImplementedException ();
3008                 }
3009
3010                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
3011                 {
3012                         return this;
3013                 }
3014
3015                 public void Error_NamespaceDoesNotExist (IMemberContext ctx, string name, int arity)
3016                 {
3017                         var retval = Namespace.LookupType (ctx, name, arity, LookupMode.IgnoreAccessibility, loc);
3018                         if (retval != null) {
3019 //                              ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (retval.MemberDefinition);
3020                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
3021                                 return;
3022                         }
3023
3024                         retval = Namespace.LookupType (ctx, name, -System.Math.Max (1, arity), LookupMode.Probing, loc);
3025                         if (retval != null) {
3026                                 Error_TypeArgumentsCannotBeUsed (ctx, retval, loc);
3027                                 return;
3028                         }
3029
3030                         Namespace ns;
3031                         if (arity > 0 && Namespace.TryGetNamespace (name, out ns)) {
3032                                 Error_TypeArgumentsCannotBeUsed (ctx, ExprClassName, ns.GetSignatureForError (), loc);
3033                                 return;
3034                         }
3035
3036                         string assembly = null;
3037                         string possible_name = Namespace.GetSignatureForError () + "." + name;
3038
3039                         // Only assembly unique name should be added
3040                         switch (possible_name) {
3041                         case "System.Drawing":
3042                         case "System.Web.Services":
3043                         case "System.Web":
3044                         case "System.Data":
3045                         case "System.Configuration":
3046                         case "System.Data.Services":
3047                         case "System.DirectoryServices":
3048                         case "System.Json":
3049                         case "System.Net.Http":
3050                         case "System.Numerics":
3051                         case "System.Runtime.Caching":
3052                         case "System.ServiceModel":
3053                         case "System.Transactions":
3054                         case "System.Web.Routing":
3055                         case "System.Xml.Linq":
3056                         case "System.Xml":
3057                                 assembly = possible_name;
3058                                 break;
3059
3060                         case "System.Linq":
3061                         case "System.Linq.Expressions":
3062                                 assembly = "System.Core";
3063                                 break;
3064
3065                         case "System.Windows.Forms":
3066                         case "System.Windows.Forms.Layout":
3067                                 assembly = "System.Windows.Forms";
3068                                 break;
3069                         }
3070
3071                         assembly = assembly == null ? "an" : "`" + assembly + "'";
3072
3073                         if (Namespace is GlobalRootNamespace) {
3074                                 ctx.Module.Compiler.Report.Error (400, loc,
3075                                         "The type or namespace name `{0}' could not be found in the global namespace. Are you missing {1} assembly reference?",
3076                                         name, assembly);
3077                         } else {
3078                                 ctx.Module.Compiler.Report.Error (234, loc,
3079                                         "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing {2} assembly reference?",
3080                                         name, GetSignatureForError (), assembly);
3081                         }
3082                 }
3083
3084                 public override string GetSignatureForError ()
3085                 {
3086                         return ns.GetSignatureForError ();
3087                 }
3088
3089                 public FullNamedExpression LookupTypeOrNamespace (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
3090                 {
3091                         return ns.LookupTypeOrNamespace (ctx, name, arity, mode, loc);
3092                 }
3093     }
3094
3095         /// <summary>
3096         ///   This class denotes an expression which evaluates to a member
3097         ///   of a struct or a class.
3098         /// </summary>
3099         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
3100         {
3101                 //
3102                 // An instance expression associated with this member, if it's a
3103                 // non-static member
3104                 //
3105                 public Expression InstanceExpression;
3106
3107                 /// <summary>
3108                 ///   The name of this member.
3109                 /// </summary>
3110                 public abstract string Name {
3111                         get;
3112                 }
3113
3114                 //
3115                 // When base.member is used
3116                 //
3117                 public bool IsBase {
3118                         get { return InstanceExpression is BaseThis; }
3119                 }
3120
3121                 /// <summary>
3122                 ///   Whether this is an instance member.
3123                 /// </summary>
3124                 public abstract bool IsInstance {
3125                         get;
3126                 }
3127
3128                 /// <summary>
3129                 ///   Whether this is a static member.
3130                 /// </summary>
3131                 public abstract bool IsStatic {
3132                         get;
3133                 }
3134
3135                 public abstract string KindName {
3136                         get;
3137                 }
3138
3139                 protected abstract TypeSpec DeclaringType {
3140                         get;
3141                 }
3142
3143                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
3144                         get {
3145                                 return InstanceExpression.Type;
3146                         }
3147                 }
3148
3149                 //
3150                 // Converts best base candidate for virtual method starting from QueriedBaseType
3151                 //
3152                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
3153                 {
3154                         //
3155                         // Only when base.member is used and method is virtual
3156                         //
3157                         if (!IsBase)
3158                                 return method;
3159
3160                         //
3161                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
3162                         // means for base.member access we have to find the closest match after we found best candidate
3163                         //
3164                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
3165                                 //
3166                                 // The method could already be what we are looking for
3167                                 //
3168                                 TypeSpec[] targs = null;
3169                                 if (method.DeclaringType != InstanceExpression.Type) {
3170                                         //
3171                                         // Candidate can have inflated MVAR parameters and we need to find
3172                                         // base match for original definition not inflated parameter types
3173                                         //
3174                                         var parameters = method.Parameters;
3175                                         if (method.Arity > 0) {
3176                                                 parameters = ((IParametersMember) method.MemberDefinition).Parameters;
3177                                                 var inflated = method.DeclaringType as InflatedTypeSpec;
3178                                                 if (inflated != null) {
3179                                                         parameters = parameters.Inflate (inflated.CreateLocalInflator (rc));
3180                                                 }
3181                                         }
3182
3183                                         var filter = new MemberFilter (method.Name, method.Arity, MemberKind.Method, parameters, null);
3184                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as MethodSpec;
3185                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
3186                                                 if (base_override.IsGeneric)
3187                                                         targs = method.TypeArguments;
3188
3189                                                 method = base_override;
3190                                         }
3191                                 }
3192
3193                                 //
3194                                 // When base access is used inside anonymous method/iterator/etc we need to
3195                                 // get back to the context of original type. We do it by emiting proxy
3196                                 // method in original class and rewriting base call to this compiler
3197                                 // generated method call which does the actual base invocation. This may
3198                                 // introduce redundant storey but with `this' only but it's tricky to avoid
3199                                 // at this stage as we don't know what expressions follow base
3200                                 //
3201                                 if (rc.CurrentAnonymousMethod != null) {
3202                                         if (targs == null && method.IsGeneric) {
3203                                                 targs = method.TypeArguments;
3204                                                 method = method.GetGenericMethodDefinition ();
3205                                         }
3206
3207                                         if (method.Parameters.HasArglist)
3208                                                 throw new NotImplementedException ("__arglist base call proxy");
3209
3210                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
3211
3212                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
3213                                         // get/set member expressions second call would fail to proxy because left expression
3214                                         // would be of 'this' and not 'base' because we share InstanceExpression for get/set
3215                                         // FIXME: The async check is another hack but will probably fail with mutators
3216                                         if (rc.CurrentType.IsStruct || rc.CurrentAnonymousMethod.Storey is AsyncTaskStorey)
3217                                                 InstanceExpression = new This (loc).Resolve (rc);
3218                                 }
3219
3220                                 if (targs != null)
3221                                         method = method.MakeGenericMethod (rc, targs);
3222                         }
3223
3224                         //
3225                         // Only base will allow this invocation to happen.
3226                         //
3227                         if (method.IsAbstract) {
3228                                 rc.Report.SymbolRelatedToPreviousError (method);
3229                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
3230                         }
3231
3232                         return method;
3233                 }
3234
3235                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3236                 {
3237                         if (InstanceExpression == null)
3238                                 return;
3239
3240                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
3241                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
3242                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
3243                                 }
3244                         }
3245                 }
3246
3247                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3248                 {
3249                         if (InstanceExpression == null)
3250                                 return true;
3251
3252                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
3253                 }
3254
3255                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
3256                 {
3257                         var ct = rc.CurrentType;
3258                         if (ct == qualifier)
3259                                 return true;
3260
3261                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
3262                                 return true;
3263
3264                         qualifier = qualifier.GetDefinition ();
3265                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
3266                                 return false;
3267                         }
3268
3269                         return true;
3270                 }
3271
3272                 public override bool ContainsEmitWithAwait ()
3273                 {
3274                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
3275                 }
3276
3277                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
3278                 {
3279                         do {
3280                                 type = type.GetDefinition ();
3281
3282                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
3283                                         return true;
3284
3285                                 type = type.DeclaringType;
3286                         } while (type != null);
3287
3288                         return false;
3289                 }
3290
3291                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
3292                 {
3293                         if (InstanceExpression != null) {
3294                                 InstanceExpression = InstanceExpression.Resolve (rc);
3295                                 CheckProtectedMemberAccess (rc, member);
3296                         }
3297
3298                         if (member.MemberType.IsPointer && !rc.IsUnsafe) {
3299                                 UnsafeError (rc, loc);
3300                         }
3301
3302                         var dep = member.GetMissingDependencies ();
3303                         if (dep != null) {
3304                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
3305                         }
3306
3307                         if (!rc.IsObsolete) {
3308                                 ObsoleteAttribute oa = member.GetAttributeObsolete ();
3309                                 if (oa != null)
3310                                         AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
3311                         }
3312
3313                         if (!(member is FieldSpec))
3314                                 member.MemberDefinition.SetIsUsed ();
3315                 }
3316
3317                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
3318                 {
3319                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
3320                 }
3321
3322                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
3323                 {
3324                         rc.Report.SymbolRelatedToPreviousError (member);
3325                         rc.Report.Error (1540, loc,
3326                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
3327                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3328                 }
3329
3330                 public override void FlowAnalysis (FlowAnalysisContext fc)
3331                 {
3332                         if (InstanceExpression != null)
3333                                 InstanceExpression.FlowAnalysis (fc);
3334                 }
3335
3336                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
3337                 {
3338                         if (!ResolveInstanceExpressionCore (rc, rhs))
3339                                 return false;
3340
3341                         //
3342                         // Check intermediate value modification which won't have any effect
3343                         //
3344                         if (rhs != null && InstanceExpression.Type.IsStruct) {
3345                                 var fexpr = InstanceExpression as FieldExpr;
3346                                 if (fexpr != null) {
3347                                         if (!fexpr.Spec.IsReadOnly || rc.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
3348                                                 return true;
3349
3350                                         if (fexpr.IsStatic) {
3351                                                 rc.Report.Error (1650, loc, "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
3352                                                         fexpr.GetSignatureForError ());
3353                                         } else {
3354                                                 rc.Report.Error (1648, loc, "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
3355                                                         fexpr.GetSignatureForError ());
3356                                         }
3357
3358                                         return true;
3359                                 }
3360
3361                                 if (InstanceExpression is PropertyExpr || InstanceExpression is IndexerExpr || InstanceExpression is Invocation) {
3362                                         if (rc.CurrentInitializerVariable != null) {
3363                                                 rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
3364                                                         InstanceExpression.Type.GetSignatureForError (), InstanceExpression.GetSignatureForError ());
3365                                         } else {
3366                                                 rc.Report.Error (1612, loc,
3367                                                         "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
3368                                                         InstanceExpression.GetSignatureForError ());
3369                                         }
3370
3371                                         return true;
3372                                 }
3373
3374                                 var lvr = InstanceExpression as LocalVariableReference;
3375                                 if (lvr != null) {
3376
3377                                         if (!lvr.local_info.IsReadonly)
3378                                                 return true;
3379
3380                                         rc.Report.Error (1654, loc, "Cannot assign to members of `{0}' because it is a `{1}'",
3381                                                 InstanceExpression.GetSignatureForError (), lvr.local_info.GetReadOnlyContext ());
3382                                 }
3383                         }
3384
3385                         return true;
3386                 }
3387
3388                 bool ResolveInstanceExpressionCore (ResolveContext rc, Expression rhs)
3389                 {
3390                         if (IsStatic) {
3391                                 if (InstanceExpression != null) {
3392                                         if (InstanceExpression is TypeExpr) {
3393                                                 var t = InstanceExpression.Type;
3394                                                 do {
3395                                                         ObsoleteAttribute oa = t.GetAttributeObsolete ();
3396                                                         if (oa != null && !rc.IsObsolete) {
3397                                                                 AttributeTester.Report_ObsoleteMessage (oa, t.GetSignatureForError (), loc, rc.Report);
3398                                                         }
3399
3400                                                         t = t.DeclaringType;
3401                                                 } while (t != null);
3402                                         } else {
3403                                                 var runtime_expr = InstanceExpression as RuntimeValueExpression;
3404                                                 if (runtime_expr == null || !runtime_expr.IsSuggestionOnly) {
3405                                                         rc.Report.Error (176, loc,
3406                                                                 "Static member `{0}' cannot be accessed with an instance reference, qualify it with a type name instead",
3407                                                                 GetSignatureForError ());
3408                                                 }
3409                                         }
3410
3411                                         InstanceExpression = null;
3412                                 }
3413
3414                                 return false;
3415                         }
3416
3417                         if (InstanceExpression == null || InstanceExpression is TypeExpr) {
3418                                 if (InstanceExpression != null || !This.IsThisAvailable (rc, true)) {
3419                                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope))
3420                                                 rc.Report.Error (236, loc,
3421                                                         "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
3422                                                         GetSignatureForError ());
3423                                         else
3424                                                 rc.Report.Error (120, loc,
3425                                                         "An object reference is required to access non-static member `{0}'",
3426                                                         GetSignatureForError ());
3427
3428                                         InstanceExpression = new CompilerGeneratedThis (rc.CurrentType, loc).Resolve (rc);
3429                                         return false;
3430                                 }
3431
3432                                 if (!TypeManager.IsFamilyAccessible (rc.CurrentType, DeclaringType)) {
3433                                         rc.Report.Error (38, loc,
3434                                                 "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
3435                                                 DeclaringType.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3436                                 }
3437
3438                                 InstanceExpression = new This (loc).Resolve (rc);
3439                                 return false;
3440                         }
3441
3442                         var me = InstanceExpression as MemberExpr;
3443                         if (me != null) {
3444                                 me.ResolveInstanceExpressionCore (rc, rhs);
3445
3446                                 var fe = me as FieldExpr;
3447                                 if (fe != null && fe.IsMarshalByRefAccess (rc)) {
3448                                         rc.Report.SymbolRelatedToPreviousError (me.DeclaringType);
3449                                         rc.Report.Warning (1690, 1, loc,
3450                                                 "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
3451                                                 me.GetSignatureForError ());
3452                                 }
3453
3454                                 return true;
3455                         }
3456
3457                         //
3458                         // Additional checks for l-value member access
3459                         //
3460                         if (rhs != null) {
3461                                 if (InstanceExpression is UnboxCast) {
3462                                         rc.Report.Error (445, InstanceExpression.Location, "Cannot modify the result of an unboxing conversion");
3463                                 }
3464                         }
3465
3466                         return true;
3467                 }
3468
3469                 public virtual MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3470                 {
3471                         if (left != null && left.IsNull && TypeSpec.IsReferenceType (left.Type)) {
3472                                 ec.Report.Warning (1720, 1, left.Location,
3473                                         "Expression will always cause a `{0}'", "System.NullReferenceException");
3474                         }
3475
3476                         InstanceExpression = left;
3477                         return this;
3478                 }
3479
3480                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
3481                 {
3482                         TypeSpec instance_type = InstanceExpression.Type;
3483                         if (TypeSpec.IsValueType (instance_type)) {
3484                                 if (InstanceExpression is IMemoryLocation) {
3485                                         ((IMemoryLocation) InstanceExpression).AddressOf (ec, AddressOp.Load);
3486                                 } else {
3487                                         // Cannot release the temporary variable when its address
3488                                         // is required to be on stack for any parent
3489                                         LocalTemporary t = new LocalTemporary (instance_type);
3490                                         InstanceExpression.Emit (ec);
3491                                         t.Store (ec);
3492                                         t.AddressOf (ec, AddressOp.Store);
3493                                 }
3494                         } else {
3495                                 InstanceExpression.Emit (ec);
3496
3497                                 // Only to make verifier happy
3498                                 if (instance_type.IsGenericParameter && !(InstanceExpression is This) && TypeSpec.IsReferenceType (instance_type))
3499                                         ec.Emit (OpCodes.Box, instance_type);
3500                         }
3501
3502                         if (prepare_for_load)
3503                                 ec.Emit (OpCodes.Dup);
3504                 }
3505
3506                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3507         }
3508
3509         public class ExtensionMethodCandidates
3510         {
3511                 readonly NamespaceContainer container;
3512                 readonly IList<MethodSpec> methods;
3513                 readonly int index;
3514                 readonly IMemberContext context;
3515
3516                 public ExtensionMethodCandidates (IMemberContext context, IList<MethodSpec> methods, NamespaceContainer nsContainer, int lookupIndex)
3517                 {
3518                         this.context = context;
3519                         this.methods = methods;
3520                         this.container = nsContainer;
3521                         this.index = lookupIndex;
3522                 }
3523
3524                 public NamespaceContainer Container {
3525                         get {
3526                                 return container;
3527                         }
3528                 }
3529
3530                 public IMemberContext Context {
3531                         get {
3532                                 return context;
3533                         }
3534                 }
3535
3536                 public int LookupIndex {
3537                         get {
3538                                 return index;
3539                         }
3540                 }
3541
3542                 public IList<MethodSpec> Methods {
3543                         get {
3544                                 return methods;
3545                         }
3546                 }
3547         }
3548
3549         //
3550         // Represents a group of extension method candidates for whole namespace
3551         //
3552         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3553         {
3554                 ExtensionMethodCandidates candidates;
3555                 public Expression ExtensionExpression;
3556
3557                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3558                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3559                 {
3560                         this.candidates = candidates;
3561                         this.ExtensionExpression = extensionExpr;
3562                 }
3563
3564                 public override bool IsStatic {
3565                         get { return true; }
3566                 }
3567
3568                 //
3569                 // For extension methodgroup we are not looking for base members but parent
3570                 // namespace extension methods
3571                 //
3572                 public override IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3573                 {
3574                         // TODO: candidates are null only when doing error reporting, that's
3575                         // incorrect. We have to discover same extension methods in error mode
3576                         if (candidates == null)
3577                                 return null;
3578
3579                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3580
3581                         candidates = candidates.Container.LookupExtensionMethod (candidates.Context, ExtensionExpression.Type, Name, arity, candidates.LookupIndex);
3582                         if (candidates == null)
3583                                 return null;
3584
3585                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3586                 }
3587
3588                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3589                 {
3590                         // We are already here
3591                         return null;
3592                 }
3593
3594                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3595                 {
3596                         if (arguments == null)
3597                                 arguments = new Arguments (1);
3598
3599                         ExtensionExpression = ExtensionExpression.Resolve (ec);
3600                         if (ExtensionExpression == null)
3601                                 return null;
3602
3603                         var cand = candidates;
3604                         arguments.Insert (0, new Argument (ExtensionExpression, Argument.AType.ExtensionType));
3605                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3606
3607                         // Restore candidates in case we are running in probing mode
3608                         candidates = cand;
3609
3610                         // Store resolved argument and restore original arguments
3611                         if (res == null) {
3612                                 // Clean-up modified arguments for error reporting
3613                                 arguments.RemoveAt (0);
3614                                 return null;
3615                         }
3616
3617                         var me = ExtensionExpression as MemberExpr;
3618                         if (me != null) {
3619                                 me.ResolveInstanceExpression (ec, null);
3620                                 var fe = me as FieldExpr;
3621                                 if (fe != null)
3622                                         fe.Spec.MemberDefinition.SetIsUsed ();
3623                         }
3624
3625                         InstanceExpression = null;
3626                         return this;
3627                 }
3628
3629                 #region IErrorHandler Members
3630
3631                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3632                 {
3633                         return false;
3634                 }
3635
3636                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3637                 {
3638                         rc.Report.SymbolRelatedToPreviousError (best);
3639                         rc.Report.Error (1928, loc,
3640                                 "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3641                                 queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3642
3643                         if (index == 0) {
3644                                 rc.Report.Error (1929, loc,
3645                                         "Extension method instance type `{0}' cannot be converted to `{1}'",
3646                                         arg.Type.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3647                         }
3648
3649                         return true;
3650                 }
3651
3652                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3653                 {
3654                         return false;
3655                 }
3656
3657                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3658                 {
3659                         return false;
3660                 }
3661
3662                 #endregion
3663         }
3664
3665         /// <summary>
3666         ///   MethodGroupExpr represents a group of method candidates which
3667         ///   can be resolved to the best method overload
3668         /// </summary>
3669         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3670         {
3671                 static readonly MemberSpec[] Excluded = new MemberSpec[0];
3672
3673                 protected IList<MemberSpec> Methods;
3674                 MethodSpec best_candidate;
3675                 TypeSpec best_candidate_return;
3676                 protected TypeArguments type_arguments;
3677
3678                 SimpleName simple_name;
3679                 protected TypeSpec queried_type;
3680
3681                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3682                 {
3683                         Methods = mi;
3684                         this.loc = loc;
3685                         this.type = InternalType.MethodGroup;
3686
3687                         eclass = ExprClass.MethodGroup;
3688                         queried_type = type;
3689                 }
3690
3691                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3692                         : this (new MemberSpec[] { m }, type, loc)
3693                 {
3694                 }
3695
3696                 #region Properties
3697
3698                 public MethodSpec BestCandidate {
3699                         get {
3700                                 return best_candidate;
3701                         }
3702                 }
3703
3704                 public TypeSpec BestCandidateReturnType {
3705                         get {
3706                                 return best_candidate_return;
3707                         }
3708                 }
3709
3710                 public IList<MemberSpec> Candidates {
3711                         get {
3712                                 return Methods;
3713                         }
3714                 }
3715
3716                 protected override TypeSpec DeclaringType {
3717                         get {
3718                                 return queried_type;
3719                         }
3720                 }
3721
3722                 public bool IsConditionallyExcluded {
3723                         get {
3724                                 return Methods == Excluded;
3725                         }
3726                 }
3727
3728                 public override bool IsInstance {
3729                         get {
3730                                 if (best_candidate != null)
3731                                         return !best_candidate.IsStatic;
3732
3733                                 return false;
3734                         }
3735                 }
3736
3737                 public override bool IsSideEffectFree {
3738                         get {
3739                                 return InstanceExpression == null || InstanceExpression.IsSideEffectFree;
3740                         }
3741                 }
3742
3743                 public override bool IsStatic {
3744                         get {
3745                                 if (best_candidate != null)
3746                                         return best_candidate.IsStatic;
3747
3748                                 return false;
3749                         }
3750                 }
3751
3752                 public override string KindName {
3753                         get { return "method"; }
3754                 }
3755
3756                 public override string Name {
3757                         get {
3758                                 if (best_candidate != null)
3759                                         return best_candidate.Name;
3760
3761                                 // TODO: throw ?
3762                                 return Methods.First ().Name;
3763                         }
3764                 }
3765
3766                 #endregion
3767
3768                 //
3769                 // When best candidate is already know this factory can be used
3770                 // to avoid expensive overload resolution to be called
3771                 //
3772                 // NOTE: InstanceExpression has to be set manually
3773                 //
3774                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3775                 {
3776                         return new MethodGroupExpr (best, queriedType, loc) {
3777                                 best_candidate = best,
3778                                 best_candidate_return = best.ReturnType
3779                         };
3780                 }
3781
3782                 public override string GetSignatureForError ()
3783                 {
3784                         if (best_candidate != null)
3785                                 return best_candidate.GetSignatureForError ();
3786
3787                         return Methods.First ().GetSignatureForError ();
3788                 }
3789
3790                 public override Expression CreateExpressionTree (ResolveContext ec)
3791                 {
3792                         if (best_candidate == null) {
3793                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3794                                 return null;
3795                         }
3796
3797                         if (IsConditionallyExcluded)
3798                                 ec.Report.Error (765, loc,
3799                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3800
3801                         return new TypeOfMethod (best_candidate, loc);
3802                 }
3803
3804                 protected override Expression DoResolve (ResolveContext ec)
3805                 {
3806                         this.eclass = ExprClass.MethodGroup;
3807
3808                         if (InstanceExpression != null) {
3809                                 InstanceExpression = InstanceExpression.Resolve (ec);
3810                                 if (InstanceExpression == null)
3811                                         return null;
3812                         }
3813
3814                         return this;
3815                 }
3816
3817                 public override void Emit (EmitContext ec)
3818                 {
3819                         throw new NotSupportedException ();
3820                 }
3821
3822                 public void EmitCall (EmitContext ec, Arguments arguments)
3823                 {
3824                         var call = new CallEmitter ();
3825                         call.InstanceExpression = InstanceExpression;
3826                         call.Emit (ec, best_candidate, arguments, loc);
3827                 }
3828
3829                 public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
3830                 {
3831                         ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
3832                                 Name, target.GetSignatureForError ());
3833                 }
3834
3835                 public static bool IsExtensionMethodArgument (Expression expr)
3836                 {
3837                         //
3838                         // LAMESPEC: No details about which expressions are not allowed
3839                         //
3840                         return !(expr is TypeExpr) && !(expr is BaseThis);
3841                 }
3842
3843                 /// <summary>
3844                 ///   Find the Applicable Function Members (7.4.2.1)
3845                 ///
3846                 ///   me: Method Group expression with the members to select.
3847                 ///       it might contain constructors or methods (or anything
3848                 ///       that maps to a method).
3849                 ///
3850                 ///   Arguments: ArrayList containing resolved Argument objects.
3851                 ///
3852                 ///   loc: The location if we want an error to be reported, or a Null
3853                 ///        location for "probing" purposes.
3854                 ///
3855                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
3856                 ///            that is the best match of me on Arguments.
3857                 ///
3858                 /// </summary>
3859                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
3860                 {
3861                         // TODO: causes issues with probing mode, remove explicit Kind check
3862                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
3863                                 return this;
3864
3865                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
3866                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
3867                                 r.BaseMembersProvider = this;
3868                                 r.InstanceQualifier = this;
3869                         }
3870
3871                         if (cerrors != null)
3872                                 r.CustomErrors = cerrors;
3873
3874                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
3875                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
3876                         if (best_candidate == null)
3877                                 return r.BestCandidateIsDynamic ? this : null;
3878
3879                         // Overload resolver had to create a new method group, all checks bellow have already been executed
3880                         if (r.BestCandidateNewMethodGroup != null)
3881                                 return r.BestCandidateNewMethodGroup;
3882
3883                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
3884                                 if (InstanceExpression != null) {
3885                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
3886                                                 InstanceExpression = null;
3887                                         } else {
3888                                                 if (best_candidate.IsStatic && simple_name != null) {
3889                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
3890                                                 }
3891
3892                                                 InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup | ResolveFlags.Type);
3893                                         }
3894                                 }
3895
3896                                 ResolveInstanceExpression (ec, null);
3897                         }
3898
3899                         var base_override = CandidateToBaseOverride (ec, best_candidate);
3900                         if (base_override == best_candidate) {
3901                                 best_candidate_return = r.BestCandidateReturnType;
3902                         } else {
3903                                 best_candidate = base_override;
3904                                 best_candidate_return = best_candidate.ReturnType;
3905                         }
3906
3907                         if (best_candidate.IsGeneric && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0 && TypeParameterSpec.HasAnyTypeParameterConstrained (best_candidate.GenericDefinition)) {
3908                                 ConstraintChecker cc = new ConstraintChecker (ec);
3909                                 cc.CheckAll (best_candidate.GetGenericMethodDefinition (), best_candidate.TypeArguments, best_candidate.Constraints, loc);
3910                         }
3911
3912                         //
3913                         // Additional check for possible imported base override method which
3914                         // could not be done during IsOverrideMethodBaseTypeAccessible
3915                         //
3916                         if (best_candidate.IsVirtual && (best_candidate.DeclaringType.Modifiers & Modifiers.PROTECTED) != 0 &&
3917                                 best_candidate.MemberDefinition.IsImported && !best_candidate.DeclaringType.IsAccessible (ec)) {
3918                                 ec.Report.SymbolRelatedToPreviousError (best_candidate);
3919                                 ErrorIsInaccesible (ec, best_candidate.GetSignatureForError (), loc);
3920                         }
3921
3922                         // Speed up the check by not doing it on disallowed targets
3923                         if (best_candidate_return.Kind == MemberKind.Void && best_candidate.IsConditionallyExcluded (ec))
3924                                 Methods = Excluded;
3925
3926                         return this;
3927                 }
3928
3929                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3930                 {
3931                         var fe = left as FieldExpr;
3932                         if (fe != null) {
3933                                 //
3934                                 // Using method-group on struct fields makes the struct assigned. I am not sure
3935                                 // why but that's what .net does
3936                                 //
3937                                 fe.Spec.MemberDefinition.SetIsAssigned ();
3938                         }
3939
3940                         simple_name = original;
3941                         return base.ResolveMemberAccess (ec, left, original);
3942                 }
3943
3944                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
3945                 {
3946                         type_arguments = ta;
3947                 }
3948
3949                 #region IBaseMembersProvider Members
3950
3951                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3952                 {
3953                         return baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
3954                 }
3955
3956                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3957                 {
3958                         if (queried_type == member.DeclaringType)
3959                                 return null;
3960
3961                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
3962                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
3963                 }
3964
3965                 //
3966                 // Extension methods lookup after ordinary methods candidates failed to apply
3967                 //
3968                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3969                 {
3970                         if (InstanceExpression == null || InstanceExpression.eclass == ExprClass.Type)
3971                                 return null;
3972
3973                         if (!IsExtensionMethodArgument (InstanceExpression))
3974                                 return null;
3975
3976                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3977                         var methods = rc.LookupExtensionMethod (InstanceExpression.Type, Methods[0].Name, arity);
3978                         if (methods == null)
3979                                 return null;
3980
3981                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
3982                         emg.SetTypeArguments (rc, type_arguments);
3983                         return emg;
3984                 }
3985
3986                 #endregion
3987         }
3988
3989         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
3990         {
3991                 public ConstructorInstanceQualifier (TypeSpec type)
3992                         : this ()
3993                 {
3994                         InstanceType = type;
3995                 }
3996
3997                 public TypeSpec InstanceType { get; private set; }
3998
3999                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
4000                 {
4001                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
4002                 }
4003         }
4004
4005         public struct OverloadResolver
4006         {
4007                 [Flags]
4008                 public enum Restrictions
4009                 {
4010                         None = 0,
4011                         DelegateInvoke = 1,
4012                         ProbingOnly     = 1 << 1,
4013                         CovariantDelegate = 1 << 2,
4014                         NoBaseMembers = 1 << 3,
4015                         BaseMembersIncluded = 1 << 4
4016                 }
4017
4018                 public interface IBaseMembersProvider
4019                 {
4020                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
4021                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
4022                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
4023                 }
4024
4025                 public interface IErrorHandler
4026                 {
4027                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
4028                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
4029                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
4030                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
4031                 }
4032
4033                 public interface IInstanceQualifier
4034                 {
4035                         TypeSpec InstanceType { get; }
4036                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
4037                 }
4038
4039                 sealed class NoBaseMembers : IBaseMembersProvider
4040                 {
4041                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
4042
4043                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
4044                         {
4045                                 return null;
4046                         }
4047
4048                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
4049                         {
4050                                 return null;
4051                         }
4052
4053                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
4054                         {
4055                                 return null;
4056                         }
4057                 }
4058
4059                 struct AmbiguousCandidate
4060                 {
4061                         public readonly MemberSpec Member;
4062                         public readonly bool Expanded;
4063                         public readonly AParametersCollection Parameters;
4064
4065                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
4066                         {
4067                                 Member = member;
4068                                 Parameters = parameters;
4069                                 Expanded = expanded;
4070                         }
4071                 }
4072
4073                 Location loc;
4074                 IList<MemberSpec> members;
4075                 TypeArguments type_arguments;
4076                 IBaseMembersProvider base_provider;
4077                 IErrorHandler custom_errors;
4078                 IInstanceQualifier instance_qualifier;
4079                 Restrictions restrictions;
4080                 MethodGroupExpr best_candidate_extension_group;
4081                 TypeSpec best_candidate_return_type;
4082
4083                 SessionReportPrinter lambda_conv_msgs;
4084
4085                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
4086                         : this (members, null, restrictions, loc)
4087                 {
4088                 }
4089
4090                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
4091                         : this ()
4092                 {
4093                         if (members == null || members.Count == 0)
4094                                 throw new ArgumentException ("empty members set");
4095
4096                         this.members = members;
4097                         this.loc = loc;
4098                         type_arguments = targs;
4099                         this.restrictions = restrictions;
4100                         if (IsDelegateInvoke)
4101                                 this.restrictions |= Restrictions.NoBaseMembers;
4102
4103                         base_provider = NoBaseMembers.Instance;
4104                 }
4105
4106                 #region Properties
4107
4108                 public IBaseMembersProvider BaseMembersProvider {
4109                         get {
4110                                 return base_provider;
4111                         }
4112                         set {
4113                                 base_provider = value;
4114                         }
4115                 }
4116
4117                 public bool BestCandidateIsDynamic { get; set; }
4118
4119                 //
4120                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
4121                 //
4122                 public MethodGroupExpr BestCandidateNewMethodGroup {
4123                         get {
4124                                 return best_candidate_extension_group;
4125                         }
4126                 }
4127
4128                 //
4129                 // Return type can be different between best candidate and closest override
4130                 //
4131                 public TypeSpec BestCandidateReturnType {
4132                         get {
4133                                 return best_candidate_return_type;
4134                         }
4135                 }
4136
4137                 public IErrorHandler CustomErrors {
4138                         get {
4139                                 return custom_errors;
4140                         }
4141                         set {
4142                                 custom_errors = value;
4143                         }
4144                 }
4145
4146                 TypeSpec DelegateType {
4147                         get {
4148                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
4149                                         throw new InternalErrorException ("Not running in delegate mode", loc);
4150
4151                                 return members [0].DeclaringType;
4152                         }
4153                 }
4154
4155                 public IInstanceQualifier InstanceQualifier {
4156                         get {
4157                                 return instance_qualifier;
4158                         }
4159                         set {
4160                                 instance_qualifier = value;
4161                         }
4162                 }
4163
4164                 bool IsProbingOnly {
4165                         get {
4166                                 return (restrictions & Restrictions.ProbingOnly) != 0;
4167                         }
4168                 }
4169
4170                 bool IsDelegateInvoke {
4171                         get {
4172                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
4173                         }
4174                 }
4175
4176                 #endregion
4177
4178                 //
4179                 //  7.4.3.3  Better conversion from expression
4180                 //  Returns :   1    if a->p is better,
4181                 //              2    if a->q is better,
4182                 //              0 if neither is better
4183                 //
4184                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
4185                 {
4186                         TypeSpec argument_type = a.Type;
4187
4188                         //
4189                         // If argument is an anonymous function
4190                         //
4191                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
4192                                 //
4193                                 // p and q are delegate types or expression tree types
4194                                 //
4195                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
4196                                         if (q.MemberDefinition != p.MemberDefinition) {
4197                                                 return 0;
4198                                         }
4199
4200                                         //
4201                                         // Uwrap delegate from Expression<T>
4202                                         //
4203                                         q = TypeManager.GetTypeArguments (q)[0];
4204                                         p = TypeManager.GetTypeArguments (p)[0];
4205                                 }
4206
4207                                 var p_m = Delegate.GetInvokeMethod (p);
4208                                 var q_m = Delegate.GetInvokeMethod (q);
4209
4210                                 //
4211                                 // With identical parameter lists
4212                                 //
4213                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
4214                                         return 0;
4215
4216                                 var orig_p = p;
4217                                 p = p_m.ReturnType;
4218                                 var orig_q = q;
4219                                 q = q_m.ReturnType;
4220
4221                                 //
4222                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4223                                 //
4224                                 if (p.Kind == MemberKind.Void) {
4225                                         return q.Kind != MemberKind.Void ? 2 : 0;
4226                                 }
4227
4228                                 //
4229                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4230                                 //
4231                                 if (q.Kind == MemberKind.Void) {
4232                                         return p.Kind != MemberKind.Void ? 1: 0;
4233                                 }
4234
4235                                 var am = (AnonymousMethodExpression) a.Expr;
4236
4237                                 //
4238                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
4239                                 // better conversion is performed between underlying types Y1 and Y2
4240                                 //
4241                                 if (p.IsGenericTask || q.IsGenericTask) {
4242                                         if (am.Block.IsAsync && p.IsGenericTask && q.IsGenericTask) {
4243                                                 q = q.TypeArguments[0];
4244                                                 p = p.TypeArguments[0];
4245                                         }
4246                                 } else if (q != p) {
4247                                         //
4248                                         // LAMESPEC: Lambda expression returning dynamic type has identity (better) conversion to delegate returning object type
4249                                         //
4250                                         if (q.BuiltinType == BuiltinTypeSpec.Type.Object) {
4251                                                 var am_rt = am.InferReturnType (ec, null, orig_q);
4252                                                 if (am_rt != null && am_rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4253                                                         return 2;
4254                                         } else if (p.BuiltinType == BuiltinTypeSpec.Type.Object) {
4255                                                 var am_rt = am.InferReturnType (ec, null, orig_p);
4256                                                 if (am_rt != null && am_rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4257                                                         return 1;
4258                                         }
4259                                 }
4260
4261                                 //
4262                                 // The parameters are identicial and return type is not void, use better type conversion
4263                                 // on return type to determine better one
4264                                 //
4265                         } else {
4266                                 if (argument_type == p)
4267                                         return 1;
4268
4269                                 if (argument_type == q)
4270                                         return 2;
4271                         }
4272
4273                         return BetterTypeConversion (ec, p, q);
4274                 }
4275
4276                 //
4277                 // 7.4.3.4  Better conversion from type
4278                 //
4279                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
4280                 {
4281                         if (p == null || q == null)
4282                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
4283
4284                         switch (p.BuiltinType) {
4285                         case BuiltinTypeSpec.Type.Int:
4286                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4287                                         return 1;
4288                                 break;
4289                         case BuiltinTypeSpec.Type.Long:
4290                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4291                                         return 1;
4292                                 break;
4293                         case BuiltinTypeSpec.Type.SByte:
4294                                 switch (q.BuiltinType) {
4295                                 case BuiltinTypeSpec.Type.Byte:
4296                                 case BuiltinTypeSpec.Type.UShort:
4297                                 case BuiltinTypeSpec.Type.UInt:
4298                                 case BuiltinTypeSpec.Type.ULong:
4299                                         return 1;
4300                                 }
4301                                 break;
4302                         case BuiltinTypeSpec.Type.Short:
4303                                 switch (q.BuiltinType) {
4304                                 case BuiltinTypeSpec.Type.UShort:
4305                                 case BuiltinTypeSpec.Type.UInt:
4306                                 case BuiltinTypeSpec.Type.ULong:
4307                                         return 1;
4308                                 }
4309                                 break;
4310                         case BuiltinTypeSpec.Type.Dynamic:
4311                                 // Dynamic is never better
4312                                 return 2;
4313                         }
4314
4315                         switch (q.BuiltinType) {
4316                         case BuiltinTypeSpec.Type.Int:
4317                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4318                                         return 2;
4319                                 break;
4320                         case BuiltinTypeSpec.Type.Long:
4321                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4322                                         return 2;
4323                                 break;
4324                         case BuiltinTypeSpec.Type.SByte:
4325                                 switch (p.BuiltinType) {
4326                                 case BuiltinTypeSpec.Type.Byte:
4327                                 case BuiltinTypeSpec.Type.UShort:
4328                                 case BuiltinTypeSpec.Type.UInt:
4329                                 case BuiltinTypeSpec.Type.ULong:
4330                                         return 2;
4331                                 }
4332                                 break;
4333                         case BuiltinTypeSpec.Type.Short:
4334                                 switch (p.BuiltinType) {
4335                                 case BuiltinTypeSpec.Type.UShort:
4336                                 case BuiltinTypeSpec.Type.UInt:
4337                                 case BuiltinTypeSpec.Type.ULong:
4338                                         return 2;
4339                                 }
4340                                 break;
4341                         case BuiltinTypeSpec.Type.Dynamic:
4342                                 // Dynamic is never better
4343                                 return 1;
4344                         }
4345
4346                         // FIXME: handle lifted operators
4347
4348                         // TODO: this is expensive
4349                         Expression p_tmp = new EmptyExpression (p);
4350                         Expression q_tmp = new EmptyExpression (q);
4351
4352                         bool p_to_q = Convert.ImplicitConversionExists (ec, p_tmp, q);
4353                         bool q_to_p = Convert.ImplicitConversionExists (ec, q_tmp, p);
4354
4355                         if (p_to_q && !q_to_p)
4356                                 return 1;
4357
4358                         if (q_to_p && !p_to_q)
4359                                 return 2;
4360
4361                         return 0;
4362                 }
4363
4364                 /// <summary>
4365                 ///   Determines "Better function" between candidate
4366                 ///   and the current best match
4367                 /// </summary>
4368                 /// <remarks>
4369                 ///    Returns a boolean indicating :
4370                 ///     false if candidate ain't better
4371                 ///     true  if candidate is better than the current best match
4372                 /// </remarks>
4373                 static bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
4374                         MemberSpec best, AParametersCollection bparam, bool best_params)
4375                 {
4376                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
4377                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
4378
4379                         bool better_at_least_one = false;
4380                         bool are_equivalent = true;
4381                         int args_count = args == null ? 0 : args.Count;
4382                         int j = 0;
4383                         Argument a = null;
4384                         TypeSpec ct, bt;
4385                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
4386                                 a = args[j];
4387
4388                                 // Default arguments are ignored for better decision
4389                                 if (a.IsDefaultArgument)
4390                                         break;
4391
4392                                 //
4393                                 // When comparing named argument the parameter type index has to be looked up
4394                                 // in original parameter set (override version for virtual members)
4395                                 //
4396                                 NamedArgument na = a as NamedArgument;
4397                                 if (na != null) {
4398                                         int idx = cparam.GetParameterIndexByName (na.Name);
4399                                         ct = candidate_pd.Types[idx];
4400                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4401                                                 ct = TypeManager.GetElementType (ct);
4402
4403                                         idx = bparam.GetParameterIndexByName (na.Name);
4404                                         bt = best_pd.Types[idx];
4405                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4406                                                 bt = TypeManager.GetElementType (bt);
4407                                 } else {
4408                                         ct = candidate_pd.Types[c_idx];
4409                                         bt = best_pd.Types[b_idx];
4410
4411                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
4412                                                 ct = TypeManager.GetElementType (ct);
4413                                                 --c_idx;
4414                                         }
4415
4416                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
4417                                                 bt = TypeManager.GetElementType (bt);
4418                                                 --b_idx;
4419                                         }
4420                                 }
4421
4422                                 if (TypeSpecComparer.IsEqual (ct, bt))
4423                                         continue;
4424
4425                                 are_equivalent = false;
4426                                 int result = BetterExpressionConversion (ec, a, ct, bt);
4427
4428                                 // for each argument, the conversion to 'ct' should be no worse than
4429                                 // the conversion to 'bt'.
4430                                 if (result == 2)
4431                                         return false;
4432
4433                                 // for at least one argument, the conversion to 'ct' should be better than
4434                                 // the conversion to 'bt'.
4435                                 if (result != 0)
4436                                         better_at_least_one = true;
4437                         }
4438
4439                         if (better_at_least_one)
4440                                 return true;
4441
4442                         //
4443                         // Tie-breaking rules are applied only for equivalent parameter types
4444                         //
4445                         if (!are_equivalent)
4446                                 return false;
4447
4448                         //
4449                         // If candidate is applicable in its normal form and best has a params array and is applicable
4450                         // only in its expanded form, then candidate is better
4451                         //
4452                         if (candidate_params != best_params)
4453                                 return !candidate_params;
4454
4455                         //
4456                         // We have not reached end of parameters list due to params or used default parameters
4457                         //
4458                         if (j < candidate_pd.Count && j < best_pd.Count) {
4459                                 var cand_param = candidate_pd.FixedParameters [j];
4460                                 var best_param = best_pd.FixedParameters [j];
4461
4462                                 if (candidate_pd.Count == best_pd.Count) {
4463                                         //
4464                                         // LAMESPEC:
4465                                         //
4466                                         // void Foo (params int[]) is better than void Foo (int i = 0) for Foo ()
4467                                         // void Foo (string[] s, string value = null) is better than Foo (string s, params string[]) for Foo (null)
4468                                         //
4469                                         if (cand_param.HasDefaultValue != best_param.HasDefaultValue)
4470                                                 return !candidate_params;
4471                                 } else {
4472                                         //
4473                                         // Neither is better when not all arguments are provided
4474                                         //
4475                                         // void Foo (string s, int i = 0) <-> Foo (string s, int i = 0, int i2 = 0)
4476                                         // void Foo (string s, int i = 0) <-> Foo (string s, byte i = 0)
4477                                         // void Foo (string s, params int[]) <-> Foo (string s, params byte[])
4478                                         //
4479                                         if (cand_param.HasDefaultValue && best_param.HasDefaultValue)
4480                                                 return false;
4481                                 }
4482                         }
4483
4484                         if (candidate_pd.Count != best_pd.Count)
4485                                 return candidate_pd.Count < best_pd.Count;
4486
4487                         //
4488                         // One is a non-generic method and second is a generic method, then non-generic is better
4489                         //
4490                         if (best.IsGeneric != candidate.IsGeneric)
4491                                 return best.IsGeneric;
4492
4493                         //
4494                         // Both methods have the same number of parameters, and the parameters have equal types
4495                         // Pick the "more specific" signature using rules over original (non-inflated) types
4496                         //
4497                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
4498                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
4499
4500                         bool specific_at_least_once = false;
4501                         for (j = 0; j < args_count; ++j) {
4502                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
4503                                 if (na != null) {
4504                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
4505                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
4506                                 } else {
4507                                         ct = candidate_def_pd.Types[j];
4508                                         bt = best_def_pd.Types[j];
4509                                 }
4510
4511                                 if (ct == bt)
4512                                         continue;
4513                                 TypeSpec specific = MoreSpecific (ct, bt);
4514                                 if (specific == bt)
4515                                         return false;
4516                                 if (specific == ct)
4517                                         specific_at_least_once = true;
4518                         }
4519
4520                         if (specific_at_least_once)
4521                                 return true;
4522
4523                         return false;
4524                 }
4525
4526                 static bool CheckInflatedArguments (MethodSpec ms)
4527                 {
4528                         if (!TypeParameterSpec.HasAnyTypeParameterTypeConstrained (ms.GenericDefinition))
4529                                 return true;
4530
4531                         // Setup constraint checker for probing only
4532                         ConstraintChecker cc = new ConstraintChecker (null);
4533
4534                         var mp = ms.Parameters.Types;
4535                         for (int i = 0; i < mp.Length; ++i) {
4536                                 var type = mp[i] as InflatedTypeSpec;
4537                                 if (type == null)
4538                                         continue;
4539
4540                                 var targs = type.TypeArguments;
4541                                 if (targs.Length == 0)
4542                                         continue;
4543
4544                                 // TODO: Checking inflated MVAR arguments should be enough
4545                                 if (!cc.CheckAll (type.GetDefinition (), targs, type.Constraints, Location.Null))
4546                                         return false;
4547                         }
4548
4549                         return true;
4550                 }
4551
4552                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4553                 {
4554                         rc.Report.Error (1729, loc,
4555                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4556                                 type.GetSignatureForError (), argCount.ToString ());
4557                 }
4558
4559                 //
4560                 // Determines if the candidate method is applicable to the given set of arguments
4561                 // There could be two different set of parameters for same candidate where one
4562                 // is the closest override for default values and named arguments checks and second
4563                 // one being the virtual base for the parameter types and modifiers.
4564                 //
4565                 // A return value rates candidate method compatibility,
4566                 // 0 = the best, int.MaxValue = the worst
4567                 // -1 = fatal error
4568                 //
4569                 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)
4570                 {
4571                         // Parameters of most-derived type used mainly for named and optional parameters
4572                         var pd = pm.Parameters;
4573
4574                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4575                         // params modifier instead of most-derived type
4576                         var cpd = ((IParametersMember) candidate).Parameters;
4577                         int param_count = pd.Count;
4578                         int optional_count = 0;
4579                         int score;
4580                         Arguments orig_args = arguments;
4581
4582                         if (arg_count != param_count) {
4583                                 //
4584                                 // No arguments expansion when doing exact match for delegates
4585                                 //
4586                                 if ((restrictions & Restrictions.CovariantDelegate) == 0) {
4587                                         for (int i = 0; i < pd.Count; ++i) {
4588                                                 if (pd.FixedParameters[i].HasDefaultValue) {
4589                                                         optional_count = pd.Count - i;
4590                                                         break;
4591                                                 }
4592                                         }
4593                                 }
4594
4595                                 if (optional_count != 0) {
4596                                         // Readjust expected number when params used
4597                                         if (cpd.HasParams) {
4598                                                 optional_count--;
4599                                                 if (arg_count < param_count)
4600                                                         param_count--;
4601                                         } else if (arg_count > param_count) {
4602                                                 int args_gap = System.Math.Abs (arg_count - param_count);
4603                                                 return int.MaxValue - 10000 + args_gap;
4604                                         } else if (arg_count < param_count - optional_count) {
4605                                                 int args_gap = System.Math.Abs (param_count - optional_count - arg_count);
4606                                                 return int.MaxValue - 10000 + args_gap;
4607                                         }
4608                                 } else if (arg_count != param_count) {
4609                                         int args_gap = System.Math.Abs (arg_count - param_count);
4610                                         if (!cpd.HasParams)
4611                                                 return int.MaxValue - 10000 + args_gap;
4612                                         if (arg_count < param_count - 1)
4613                                                 return int.MaxValue - 10000 + args_gap;
4614                                 }
4615
4616                                 // Resize to fit optional arguments
4617                                 if (optional_count != 0) {
4618                                         if (arguments == null) {
4619                                                 arguments = new Arguments (optional_count);
4620                                         } else {
4621                                                 // Have to create a new container, so the next run can do same
4622                                                 var resized = new Arguments (param_count);
4623                                                 resized.AddRange (arguments);
4624                                                 arguments = resized;
4625                                         }
4626
4627                                         for (int i = arg_count; i < param_count; ++i)
4628                                                 arguments.Add (null);
4629                                 }
4630                         }
4631
4632                         if (arg_count > 0) {
4633                                 //
4634                                 // Shuffle named arguments to the right positions if there are any
4635                                 //
4636                                 if (arguments[arg_count - 1] is NamedArgument) {
4637                                         arg_count = arguments.Count;
4638
4639                                         for (int i = 0; i < arg_count; ++i) {
4640                                                 bool arg_moved = false;
4641                                                 while (true) {
4642                                                         NamedArgument na = arguments[i] as NamedArgument;
4643                                                         if (na == null)
4644                                                                 break;
4645
4646                                                         int index = pd.GetParameterIndexByName (na.Name);
4647
4648                                                         // Named parameter not found
4649                                                         if (index < 0)
4650                                                                 return (i + 1) * 3;
4651
4652                                                         // already reordered
4653                                                         if (index == i)
4654                                                                 break;
4655
4656                                                         Argument temp;
4657                                                         if (index >= param_count) {
4658                                                                 // When using parameters which should not be available to the user
4659                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
4660                                                                         break;
4661
4662                                                                 arguments.Add (null);
4663                                                                 ++arg_count;
4664                                                                 temp = null;
4665                                                         } else {
4666                                                                 temp = arguments[index];
4667
4668                                                                 // The slot has been taken by positional argument
4669                                                                 if (temp != null && !(temp is NamedArgument))
4670                                                                         break;
4671                                                         }
4672
4673                                                         if (!arg_moved) {
4674                                                                 arguments = arguments.MarkOrderedArgument (na);
4675                                                                 arg_moved = true;
4676                                                         }
4677
4678                                                         if (arguments == orig_args) {
4679                                                                 arguments = new Arguments (orig_args.Count);
4680                                                                 arguments.AddRange (orig_args);
4681                                                         }
4682
4683                                                         arguments[index] = arguments[i];
4684                                                         arguments[i] = temp;
4685
4686                                                         if (temp == null)
4687                                                                 break;
4688                                                 }
4689                                         }
4690                                 } else {
4691                                         arg_count = arguments.Count;
4692                                 }
4693                         } else if (arguments != null) {
4694                                 arg_count = arguments.Count;
4695                         }
4696
4697                         //
4698                         // Don't do any expensive checks when the candidate cannot succeed
4699                         //
4700                         if (arg_count != param_count && !cpd.HasParams)
4701                                 return (param_count - arg_count) * 2 + 1;
4702
4703                         var dep = candidate.GetMissingDependencies ();
4704                         if (dep != null) {
4705                                 ImportedTypeDefinition.Error_MissingDependency (ec, dep, loc);
4706                                 return -1;
4707                         }
4708
4709                         //
4710                         // 1. Handle generic method using type arguments when specified or type inference
4711                         //
4712                         TypeSpec[] ptypes;
4713                         var ms = candidate as MethodSpec;
4714                         if (ms != null && ms.IsGeneric) {
4715                                 if (type_arguments != null) {
4716                                         var g_args_count = ms.Arity;
4717                                         if (g_args_count != type_arguments.Count)
4718                                                 return int.MaxValue - 20000 + System.Math.Abs (type_arguments.Count - g_args_count);
4719
4720                                         if (type_arguments.Arguments != null)
4721                                                 ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
4722                                 } else {
4723                                         //
4724                                         // Deploy custom error reporting for infered anonymous expression or lambda methods. When
4725                                         // probing lambda methods keep all errors reported in separate set and once we are done and no best
4726                                         // candidate was found use the set to report more details about what was wrong with lambda body.
4727                                         // The general idea is to distinguish between code errors and errors caused by
4728                                         // trial-and-error type inference
4729                                         //
4730                                         if (lambda_conv_msgs == null) {
4731                                                 for (int i = 0; i < arg_count; i++) {
4732                                                         Argument a = arguments[i];
4733                                                         if (a == null)
4734                                                                 continue;
4735
4736                                                         var am = a.Expr as AnonymousMethodExpression;
4737                                                         if (am != null) {
4738                                                                 if (lambda_conv_msgs == null)
4739                                                                         lambda_conv_msgs = new SessionReportPrinter ();
4740
4741                                                                 am.TypeInferenceReportPrinter = lambda_conv_msgs;
4742                                                         }
4743                                                 }
4744                                         }
4745
4746                                         var ti = new TypeInference (arguments);
4747                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
4748
4749                                         if (i_args == null)
4750                                                 return ti.InferenceScore - 20000;
4751
4752                                         //
4753                                         // Clear any error messages when the result was success
4754                                         //
4755                                         if (lambda_conv_msgs != null)
4756                                                 lambda_conv_msgs.ClearSession ();
4757
4758                                         if (i_args.Length != 0) {
4759                                                 ms = ms.MakeGenericMethod (ec, i_args);
4760                                         }
4761                                 }
4762
4763                                 //
4764                                 // Type arguments constraints have to match for the method to be applicable
4765                                 //
4766                                 if (!CheckInflatedArguments (ms)) {
4767                                         candidate = ms;
4768                                         return int.MaxValue - 25000;
4769                                 }
4770
4771                                 //
4772                                 // We have a generic return type and at same time the method is override which
4773                                 // means we have to also inflate override return type in case the candidate is
4774                                 // best candidate and override return type is different to base return type.
4775                                 //
4776                                 // virtual Foo<T, object> with override Foo<T, dynamic>
4777                                 //
4778                                 if (candidate != pm) {
4779                                         MethodSpec override_ms = (MethodSpec) pm;
4780                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
4781                                         returnType = inflator.Inflate (returnType);
4782                                 } else {
4783                                         returnType = ms.ReturnType;
4784                                 }
4785
4786                                 candidate = ms;
4787                                 pd = ms.Parameters;
4788                                 ptypes = pd.Types;
4789                         } else {
4790                                 if (type_arguments != null)
4791                                         return int.MaxValue - 15000;
4792
4793                                 ptypes = cpd.Types;
4794                         }
4795
4796                         //
4797                         // 2. Each argument has to be implicitly convertible to method parameter
4798                         //
4799                         Parameter.Modifier p_mod = 0;
4800                         TypeSpec pt = null;
4801
4802                         for (int i = 0; i < arg_count; i++) {
4803                                 Argument a = arguments[i];
4804                                 if (a == null) {
4805                                         var fp = pd.FixedParameters[i];
4806                                         if (!fp.HasDefaultValue) {
4807                                                 arguments = orig_args;
4808                                                 return arg_count * 2 + 2;
4809                                         }
4810
4811                                         //
4812                                         // Get the default value expression, we can use the same expression
4813                                         // if the type matches
4814                                         //
4815                                         Expression e = fp.DefaultValue;
4816                                         if (e != null) {
4817                                                 e = ResolveDefaultValueArgument (ec, ptypes[i], e, loc);
4818                                                 if (e == null) {
4819                                                         // Restore for possible error reporting
4820                                                         for (int ii = i; ii < arg_count; ++ii)
4821                                                                 arguments.RemoveAt (i);
4822
4823                                                         return (arg_count - i) * 2 + 1;
4824                                                 }
4825                                         }
4826
4827                                         if ((fp.ModFlags & Parameter.Modifier.CallerMask) != 0) {
4828                                                 //
4829                                                 // LAMESPEC: Attributes can be mixed together with build-in priority
4830                                                 //
4831                                                 if ((fp.ModFlags & Parameter.Modifier.CallerLineNumber) != 0) {
4832                                                         e = new IntLiteral (ec.BuiltinTypes, loc.Row, loc);
4833                                                 } else if ((fp.ModFlags & Parameter.Modifier.CallerFilePath) != 0) {
4834                                                         e = new StringLiteral (ec.BuiltinTypes, loc.NameFullPath, loc);
4835                                                 } else if (ec.MemberContext.CurrentMemberDefinition != null) {
4836                                                         e = new StringLiteral (ec.BuiltinTypes, ec.MemberContext.CurrentMemberDefinition.GetCallerMemberName (), loc);
4837                                                 }
4838                                         }
4839
4840                                         arguments[i] = new Argument (e, Argument.AType.Default);
4841                                         continue;
4842                                 }
4843
4844                                 if (p_mod != Parameter.Modifier.PARAMS) {
4845                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
4846                                         pt = ptypes [i];
4847                                 } else if (!params_expanded_form) {
4848                                         params_expanded_form = true;
4849                                         pt = ((ElementTypeSpec) pt).Element;
4850                                         i -= 2;
4851                                         continue;
4852                                 }
4853
4854                                 score = 1;
4855                                 if (!params_expanded_form) {
4856                                         if (a.ArgType == Argument.AType.ExtensionType) {
4857                                                 //
4858                                                 // Indentity, implicit reference or boxing conversion must exist for the extension parameter
4859                                                 //
4860                                                 // LAMESPEC: or implicit type parameter conversion
4861                                                 //
4862                                                 var at = a.Type;
4863                                                 if (at == pt || TypeSpecComparer.IsEqual (at, pt) ||
4864                                                         Convert.ImplicitReferenceConversionExists (at, pt, false) ||
4865                                                         Convert.ImplicitBoxingConversion (null, at, pt) != null) {
4866                                                         score = 0;
4867                                                         continue;
4868                                                 }
4869                                         } else {
4870                                                 score = IsArgumentCompatible (ec, a, p_mod, pt);
4871
4872                                                 if (score < 0)
4873                                                         dynamicArgument = true;
4874                                         }
4875                                 }
4876
4877                                 //
4878                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
4879                                 //
4880                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
4881                                         if (!params_expanded_form) {
4882                                                 pt = ((ElementTypeSpec) pt).Element;
4883                                         }
4884
4885                                         if (score > 0)
4886                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
4887
4888                                         if (score < 0) {
4889                                                 params_expanded_form = true;
4890                                                 dynamicArgument = true;
4891                                         } else if (score == 0 || arg_count > pd.Count) {
4892                                                 params_expanded_form = true;
4893                                         }
4894                                 }
4895
4896                                 if (score > 0) {
4897                                         if (params_expanded_form)
4898                                                 ++score;
4899                                         return (arg_count - i) * 2 + score;
4900                                 }
4901                         }
4902
4903                         //
4904                         // Restore original arguments for dynamic binder to keep the intention of original source code
4905                         //
4906                         if (dynamicArgument)
4907                                 arguments = orig_args;
4908
4909                         return 0;
4910                 }
4911
4912                 public static Expression ResolveDefaultValueArgument (ResolveContext ec, TypeSpec ptype, Expression e, Location loc)
4913                 {
4914                         if (e is Constant && e.Type == ptype)
4915                                 return e;
4916
4917                         //
4918                         // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
4919                         //
4920                         if (e == EmptyExpression.MissingValue && ptype.BuiltinType == BuiltinTypeSpec.Type.Object || ptype.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
4921                                 e = new MemberAccess (new MemberAccess (new MemberAccess (
4922                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
4923                         } else if (e is Constant) {
4924                                 //
4925                                 // Handles int to int? conversions, DefaultParameterValue check
4926                                 //
4927                                 e = Convert.ImplicitConversionStandard (ec, e, ptype, loc);
4928                                 if (e == null)
4929                                         return null;
4930                         } else {
4931                                 e = new DefaultValueExpression (new TypeExpression (ptype, loc), loc);
4932                         }
4933
4934                         return e.Resolve (ec);
4935                 }
4936
4937                 //
4938                 // Tests argument compatibility with the parameter
4939                 // The possible return values are
4940                 // 0 - success
4941                 // 1 - modifier mismatch
4942                 // 2 - type mismatch
4943                 // -1 - dynamic binding required
4944                 //
4945                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
4946                 {
4947                         //
4948                         // Types have to be identical when ref or out modifer
4949                         // is used and argument is not of dynamic type
4950                         //
4951                         if (((argument.Modifier | param_mod) & Parameter.Modifier.RefOutMask) != 0) {
4952                                 if (argument.Type != parameter) {
4953                                         //
4954                                         // Do full equality check after quick path
4955                                         //
4956                                         if (!TypeSpecComparer.IsEqual (argument.Type, parameter)) {
4957                                                 //
4958                                                 // Using dynamic for ref/out parameter can still succeed at runtime
4959                                                 //
4960                                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4961                                                         return -1;
4962
4963                                                 return 2;
4964                                         }
4965                                 }
4966
4967                                 if ((argument.Modifier & Parameter.Modifier.RefOutMask) != (param_mod & Parameter.Modifier.RefOutMask)) {
4968                                         //
4969                                         // Using dynamic for ref/out parameter can still succeed at runtime
4970                                         //
4971                                         if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4972                                                 return -1;
4973
4974                                         return 1;
4975                                 }
4976
4977                         } else {
4978                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
4979                                         return -1;
4980
4981                                 //
4982                                 // Use implicit conversion in all modes to return same candidates when the expression
4983                                 // is used as argument or delegate conversion
4984                                 //
4985                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
4986                                         return parameter.IsDelegate && argument.Expr is AnonymousMethodExpression ? 2 : 3;
4987                                 }
4988                         }
4989
4990                         return 0;
4991                 }
4992
4993                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
4994                 {
4995                         if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
4996                                 return q;
4997                         if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
4998                                 return p;
4999
5000                         var ac_p = p as ArrayContainer;
5001                         if (ac_p != null) {
5002                                 var ac_q = q as ArrayContainer;
5003                                 if (ac_q == null)
5004                                         return null;
5005
5006                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
5007                                 if (specific == ac_p.Element)
5008                                         return p;
5009                                 if (specific == ac_q.Element)
5010                                         return q;
5011                         } else if (p.IsGeneric && q.IsGeneric) {
5012                                 var pargs = TypeManager.GetTypeArguments (p);
5013                                 var qargs = TypeManager.GetTypeArguments (q);
5014
5015                                 bool p_specific_at_least_once = false;
5016                                 bool q_specific_at_least_once = false;
5017
5018                                 for (int i = 0; i < pargs.Length; i++) {
5019                                         TypeSpec specific = MoreSpecific (pargs[i], qargs[i]);
5020                                         if (specific == pargs[i])
5021                                                 p_specific_at_least_once = true;
5022                                         if (specific == qargs[i])
5023                                                 q_specific_at_least_once = true;
5024                                 }
5025
5026                                 if (p_specific_at_least_once && !q_specific_at_least_once)
5027                                         return p;
5028                                 if (!p_specific_at_least_once && q_specific_at_least_once)
5029                                         return q;
5030                         }
5031
5032                         return null;
5033                 }
5034
5035                 //
5036                 // Find the best method from candidate list
5037                 //
5038                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
5039                 {
5040                         List<AmbiguousCandidate> ambiguous_candidates = null;
5041
5042                         MemberSpec best_candidate;
5043                         Arguments best_candidate_args = null;
5044                         bool best_candidate_params = false;
5045                         bool best_candidate_dynamic = false;
5046                         int best_candidate_rate;
5047                         IParametersMember best_parameter_member = null;
5048
5049                         int args_count = args != null ? args.Count : 0;
5050
5051                         Arguments candidate_args = args;
5052                         bool error_mode = false;
5053                         MemberSpec invocable_member = null;
5054
5055                         while (true) {
5056                                 best_candidate = null;
5057                                 best_candidate_rate = int.MaxValue;
5058
5059                                 var type_members = members;
5060                                 do {
5061                                         for (int i = 0; i < type_members.Count; ++i) {
5062                                                 var member = type_members[i];
5063
5064                                                 //
5065                                                 // Methods in a base class are not candidates if any method in a derived
5066                                                 // class is applicable
5067                                                 //
5068                                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
5069                                                         continue;
5070
5071                                                 if (!error_mode) {
5072                                                         if (!member.IsAccessible (rc))
5073                                                                 continue;
5074
5075                                                         if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
5076                                                                 continue;
5077
5078                                                         if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5079                                                                 instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
5080                                                                 continue;
5081                                                         }
5082                                                 }
5083
5084                                                 IParametersMember pm = member as IParametersMember;
5085                                                 if (pm == null) {
5086                                                         //
5087                                                         // Will use it later to report ambiguity between best method and invocable member
5088                                                         //
5089                                                         if (Invocation.IsMemberInvocable (member))
5090                                                                 invocable_member = member;
5091
5092                                                         continue;
5093                                                 }
5094
5095                                                 //
5096                                                 // Overload resolution is looking for base member but using parameter names
5097                                                 // and default values from the closest member. That means to do expensive lookup
5098                                                 // for the closest override for virtual or abstract members
5099                                                 //
5100                                                 if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
5101                                                         var override_params = base_provider.GetOverrideMemberParameters (member);
5102                                                         if (override_params != null)
5103                                                                 pm = override_params;
5104                                                 }
5105
5106                                                 //
5107                                                 // Check if the member candidate is applicable
5108                                                 //
5109                                                 bool params_expanded_form = false;
5110                                                 bool dynamic_argument = false;
5111                                                 TypeSpec rt = pm.MemberType;
5112                                                 int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt);
5113
5114                                                 if (lambda_conv_msgs != null)
5115                                                         lambda_conv_msgs.EndSession ();
5116
5117                                                 //
5118                                                 // How does it score compare to others
5119                                                 //
5120                                                 if (candidate_rate < best_candidate_rate) {
5121
5122                                                         // Fatal error (missing dependency), cannot continue
5123                                                         if (candidate_rate < 0)
5124                                                                 return null;
5125
5126                                                         best_candidate_rate = candidate_rate;
5127                                                         best_candidate = member;
5128                                                         best_candidate_args = candidate_args;
5129                                                         best_candidate_params = params_expanded_form;
5130                                                         best_candidate_dynamic = dynamic_argument;
5131                                                         best_parameter_member = pm;
5132                                                         best_candidate_return_type = rt;
5133                                                 } else if (candidate_rate == 0) {
5134                                                         //
5135                                                         // The member look is done per type for most operations but sometimes
5136                                                         // it's not possible like for binary operators overload because they
5137                                                         // are unioned between 2 sides
5138                                                         //
5139                                                         if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
5140                                                                 if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
5141                                                                         continue;
5142                                                         }
5143
5144                                                         bool is_better;
5145                                                         if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5146                                                                 //
5147                                                                 // We pack all interface members into top level type which makes the overload resolution
5148                                                                 // more complicated for interfaces. We compensate it by removing methods with same
5149                                                                 // signature when building the cache hence this path should not really be hit often
5150                                                                 //
5151                                                                 // Example:
5152                                                                 // interface IA { void Foo (int arg); }
5153                                                                 // interface IB : IA { void Foo (params int[] args); }
5154                                                                 //
5155                                                                 // IB::Foo is the best overload when calling IB.Foo (1)
5156                                                                 //
5157                                                                 is_better = true;
5158                                                                 if (ambiguous_candidates != null) {
5159                                                                         foreach (var amb_cand in ambiguous_candidates) {
5160                                                                                 if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5161                                                                                         continue;
5162                                                                                 }
5163
5164                                                                                 is_better = false;
5165                                                                                 break;
5166                                                                         }
5167
5168                                                                         if (is_better)
5169                                                                                 ambiguous_candidates = null;
5170                                                                 }
5171                                                         } else {
5172                                                                 // Is the new candidate better
5173                                                                 is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
5174                                                         }
5175
5176                                                         if (is_better) {
5177                                                                 best_candidate = member;
5178                                                                 best_candidate_args = candidate_args;
5179                                                                 best_candidate_params = params_expanded_form;
5180                                                                 best_candidate_dynamic = dynamic_argument;
5181                                                                 best_parameter_member = pm;
5182                                                                 best_candidate_return_type = rt;
5183                                                         } else {
5184                                                                 // It's not better but any other found later could be but we are not sure yet
5185                                                                 if (ambiguous_candidates == null)
5186                                                                         ambiguous_candidates = new List<AmbiguousCandidate> ();
5187
5188                                                                 ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
5189                                                         }
5190                                                 }
5191
5192                                                 // Restore expanded arguments
5193                                                 candidate_args = args;
5194                                         }
5195                                 } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType.BaseType)) != null);
5196
5197                                 //
5198                                 // We've found exact match
5199                                 //
5200                                 if (best_candidate_rate == 0)
5201                                         break;
5202
5203                                 //
5204                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
5205                                 //
5206                                 if (!error_mode) {
5207                                         var emg = base_provider.LookupExtensionMethod (rc);
5208                                         if (emg != null) {
5209                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
5210                                                 if (emg != null) {
5211                                                         best_candidate_extension_group = emg;
5212                                                         return (T) (MemberSpec) emg.BestCandidate;
5213                                                 }
5214                                         }
5215                                 }
5216
5217                                 // Don't run expensive error reporting mode for probing
5218                                 if (IsProbingOnly)
5219                                         return null;
5220
5221                                 if (error_mode)
5222                                         break;
5223
5224                                 if (lambda_conv_msgs != null && !lambda_conv_msgs.IsEmpty)
5225                                         break;
5226
5227                                 lambda_conv_msgs = null;
5228                                 error_mode = true;
5229                         }
5230
5231                         //
5232                         // No best member match found, report an error
5233                         //
5234                         if (best_candidate_rate != 0 || error_mode) {
5235                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
5236                                 return null;
5237                         }
5238
5239                         if (best_candidate_dynamic) {
5240                                 if (args[0].ArgType == Argument.AType.ExtensionType) {
5241                                         rc.Report.Error (1973, loc,
5242                                                 "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",
5243                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
5244                                 }
5245
5246                                 //
5247                                 // Check type constraints only when explicit type arguments are used
5248                                 //
5249                                 if (best_candidate.IsGeneric && type_arguments != null) {
5250                                         MethodSpec bc = best_candidate as MethodSpec;
5251                                         if (bc != null && TypeParameterSpec.HasAnyTypeParameterConstrained (bc.GenericDefinition)) {
5252                                                 ConstraintChecker cc = new ConstraintChecker (rc);
5253                                                 cc.CheckAll (bc.GetGenericMethodDefinition (), bc.TypeArguments, bc.Constraints, loc);
5254                                         }
5255                                 }
5256
5257                                 BestCandidateIsDynamic = true;
5258                                 return null;
5259                         }
5260
5261                         //
5262                         // These flags indicates we are running delegate probing conversion. No need to
5263                         // do more expensive checks
5264                         //
5265                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
5266                                 return (T) best_candidate;
5267
5268                         if (ambiguous_candidates != null) {
5269                                 //
5270                                 // Now check that there are no ambiguities i.e the selected method
5271                                 // should be better than all the others
5272                                 //
5273                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
5274                                         var candidate = ambiguous_candidates [ix];
5275
5276                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
5277                                                 var ambiguous = candidate.Member;
5278                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
5279                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
5280                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
5281                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
5282                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
5283                                                 }
5284
5285                                                 return (T) best_candidate;
5286                                         }
5287                                 }
5288                         }
5289
5290                         if (invocable_member != null && !IsProbingOnly) {
5291                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5292                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
5293                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
5294                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
5295                         }
5296
5297                         //
5298                         // And now check if the arguments are all
5299                         // compatible, perform conversions if
5300                         // necessary etc. and return if everything is
5301                         // all right
5302                         //
5303                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
5304                                 return null;
5305
5306                         if (best_candidate == null)
5307                                 return null;
5308
5309                         //
5310                         // Don't run possibly expensive checks in probing mode
5311                         //
5312                         if (!IsProbingOnly && !rc.IsInProbingMode) {
5313                                 //
5314                                 // Check ObsoleteAttribute on the best method
5315                                 //
5316                                 ObsoleteAttribute oa = best_candidate.GetAttributeObsolete ();
5317                                 if (oa != null && !rc.IsObsolete)
5318                                         AttributeTester.Report_ObsoleteMessage (oa, best_candidate.GetSignatureForError (), loc, rc.Report);
5319
5320                                 best_candidate.MemberDefinition.SetIsUsed ();
5321                         }
5322
5323                         args = best_candidate_args;
5324                         return (T) best_candidate;
5325                 }
5326
5327                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
5328                 {
5329                         return ResolveMember<MethodSpec> (rc, ref args);
5330                 }
5331
5332                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
5333                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
5334                 {
5335                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
5336                                 return;
5337
5338                         if (a.Type == InternalType.ErrorType)
5339                                 return;
5340
5341                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
5342                                 ec.Report.SymbolRelatedToPreviousError (method);
5343                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
5344                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have `ref' or `out' modifier",
5345                                                 TypeManager.CSharpSignature (method));
5346                                         return;
5347                                 }
5348                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
5349                                           TypeManager.CSharpSignature (method));
5350                         } else if (IsDelegateInvoke) {
5351                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
5352                                         DelegateType.GetSignatureForError ());
5353                         } else {
5354                                 ec.Report.SymbolRelatedToPreviousError (method);
5355                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
5356                                         method.GetSignatureForError ());
5357                         }
5358
5359                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
5360
5361                         string index = (idx + 1).ToString ();
5362                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
5363                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
5364                                         ec.Report.Error (1615, a.Expr.Location, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
5365                                                 index, Parameter.GetModifierSignature (a.Modifier));
5366                                 else
5367                                         ec.Report.Error (1620, a.Expr.Location, "Argument `#{0}' is missing `{1}' modifier",
5368                                                 index, Parameter.GetModifierSignature (mod));
5369                         } else {
5370                                 string p1 = a.GetSignatureForError ();
5371                                 string p2 = paramType.GetSignatureForError ();
5372
5373                                 if (p1 == p2) {
5374                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
5375                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
5376                                 }
5377
5378                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
5379                                         p1 = Parameter.GetModifierSignature (a.Modifier) + " " + p1;
5380                                         p2 = Parameter.GetModifierSignature (a.Modifier) + " " + p2;
5381                                 }
5382
5383                                 ec.Report.Error (1503, a.Expr.Location,
5384                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
5385                         }
5386                 }
5387
5388                 //
5389                 // We have failed to find exact match so we return error info about the closest match
5390                 //
5391                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
5392                 {
5393                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
5394                         int arg_count = args == null ? 0 : args.Count;
5395
5396                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
5397                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
5398                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, loc);
5399                                 return;
5400                         }
5401
5402                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
5403                                 return;
5404                         }
5405
5406
5407                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5408                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
5409                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
5410                         }
5411
5412                         //
5413                         // For candidates which match on parameters count report more details about incorrect arguments
5414                         //
5415                         if (pm != null) {
5416                                 int unexpanded_count = ((IParametersMember) best_candidate).Parameters.HasParams ? pm.Parameters.Count - 1 : pm.Parameters.Count;
5417                                 if (pm.Parameters.Count == arg_count || params_expanded || unexpanded_count == arg_count) {
5418                                         // Reject any inaccessible member
5419                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
5420                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5421                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
5422                                                 return;
5423                                         }
5424
5425                                         var ms = best_candidate as MethodSpec;
5426                                         if (ms != null && ms.IsGeneric) {
5427                                                 bool constr_ok = true;
5428                                                 if (ms.TypeArguments != null)
5429                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
5430
5431                                                 if (ta_count == 0 && ms.TypeArguments == null) {
5432                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
5433                                                                 return;
5434
5435                                                         if (constr_ok) {
5436                                                                 rc.Report.Error (411, loc,
5437                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
5438                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
5439                                                         }
5440
5441                                                         return;
5442                                                 }
5443                                         }
5444
5445                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
5446                                         return;
5447                                 }
5448                         }
5449
5450                         //
5451                         // We failed to find any method with correct argument count, report best candidate
5452                         //
5453                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
5454                                 return;
5455
5456                         if (best_candidate.Kind == MemberKind.Constructor) {
5457                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5458                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
5459                         } else if (IsDelegateInvoke) {
5460                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
5461                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
5462                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
5463                         } else {
5464                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
5465                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5466                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
5467                                         name, arg_count.ToString ());
5468                         }
5469                 }
5470
5471                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
5472                 {
5473                         var pd = pm.Parameters;
5474                         TypeSpec[] ptypes = ((IParametersMember) member).Parameters.Types;
5475
5476                         Parameter.Modifier p_mod = 0;
5477                         TypeSpec pt = null;
5478                         int a_idx = 0, a_pos = 0;
5479                         Argument a = null;
5480                         ArrayInitializer params_initializers = null;
5481                         bool has_unsafe_arg = pm.MemberType.IsPointer;
5482                         int arg_count = args == null ? 0 : args.Count;
5483
5484                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
5485                                 a = args[a_idx];
5486                                 if (a == null)
5487                                         continue;
5488
5489                                 if (p_mod != Parameter.Modifier.PARAMS) {
5490                                         p_mod = pd.FixedParameters[a_idx].ModFlags;
5491                                         pt = ptypes[a_idx];
5492                                         has_unsafe_arg |= pt.IsPointer;
5493
5494                                         if (p_mod == Parameter.Modifier.PARAMS) {
5495                                                 if (chose_params_expanded) {
5496                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
5497                                                         pt = TypeManager.GetElementType (pt);
5498                                                 }
5499                                         }
5500                                 }
5501
5502                                 //
5503                                 // Types have to be identical when ref or out modifer is used
5504                                 //
5505                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
5506                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
5507                                                 break;
5508
5509                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt))
5510                                                 continue;
5511
5512                                         break;
5513                                 }
5514
5515                                 NamedArgument na = a as NamedArgument;
5516                                 if (na != null) {
5517                                         int name_index = pd.GetParameterIndexByName (na.Name);
5518                                         if (name_index < 0 || name_index >= pd.Count) {
5519                                                 if (IsDelegateInvoke) {
5520                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5521                                                         ec.Report.Error (1746, na.Location,
5522                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
5523                                                                 DelegateType.GetSignatureForError (), na.Name);
5524                                                 } else {
5525                                                         ec.Report.SymbolRelatedToPreviousError (member);
5526                                                         ec.Report.Error (1739, na.Location,
5527                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
5528                                                                 TypeManager.CSharpSignature (member), na.Name);
5529                                                 }
5530                                         } else if (args[name_index] != a && args[name_index] != null) {
5531                                                 if (IsDelegateInvoke)
5532                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5533                                                 else
5534                                                         ec.Report.SymbolRelatedToPreviousError (member);
5535
5536                                                 ec.Report.Error (1744, na.Location,
5537                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
5538                                                         na.Name);
5539                                         }
5540                                 }
5541
5542                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
5543                                         continue;
5544
5545                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
5546                                         custom_errors.NoArgumentMatch (ec, member);
5547                                         return false;
5548                                 }
5549
5550                                 Expression conv;
5551                                 if (a.ArgType == Argument.AType.ExtensionType) {
5552                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
5553                                                 conv = a.Expr;
5554                                         } else {
5555                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
5556                                                 if (conv == null)
5557                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
5558                                         }
5559                                 } else {
5560                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
5561                                 }
5562
5563                                 if (conv == null)
5564                                         break;
5565
5566                                 //
5567                                 // Convert params arguments to an array initializer
5568                                 //
5569                                 if (params_initializers != null) {
5570                                         // we choose to use 'a.Expr' rather than 'conv' so that
5571                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
5572                                         params_initializers.Add (a.Expr);
5573                                         args.RemoveAt (a_idx--);
5574                                         --arg_count;
5575                                         a.Expr = conv;
5576                                         continue;
5577                                 }
5578
5579                                 // Update the argument with the implicit conversion
5580                                 a.Expr = conv;
5581                         }
5582
5583                         if (a_idx != arg_count) {
5584                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
5585                                 return false;
5586                         }
5587
5588                         //
5589                         // Fill not provided arguments required by params modifier
5590                         //
5591                         if (params_initializers == null && pd.HasParams && arg_count + 1 == pd.Count) {
5592                                 if (args == null)
5593                                         args = new Arguments (1);
5594
5595                                 pt = ptypes[pd.Count - 1];
5596                                 pt = TypeManager.GetElementType (pt);
5597                                 has_unsafe_arg |= pt.IsPointer;
5598                                 params_initializers = new ArrayInitializer (0, loc);
5599                         }
5600
5601                         //
5602                         // Append an array argument with all params arguments
5603                         //
5604                         if (params_initializers != null) {
5605                                 args.Add (new Argument (
5606                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
5607                                 arg_count++;
5608                         }
5609
5610                         if (has_unsafe_arg && !ec.IsUnsafe) {
5611                                 Expression.UnsafeError (ec, loc);
5612                         }
5613
5614                         //
5615                         // We could infer inaccesible type arguments
5616                         //
5617                         if (type_arguments == null && member.IsGeneric) {
5618                                 var ms = (MethodSpec) member;
5619                                 foreach (var ta in ms.TypeArguments) {
5620                                         if (!ta.IsAccessible (ec)) {
5621                                                 ec.Report.SymbolRelatedToPreviousError (ta);
5622                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
5623                                                 break;
5624                                         }
5625                                 }
5626                         }
5627
5628                         return true;
5629                 }
5630         }
5631
5632         public class ConstantExpr : MemberExpr
5633         {
5634                 readonly ConstSpec constant;
5635
5636                 public ConstantExpr (ConstSpec constant, Location loc)
5637                 {
5638                         this.constant = constant;
5639                         this.loc = loc;
5640                 }
5641
5642                 public override string Name {
5643                         get { throw new NotImplementedException (); }
5644                 }
5645
5646                 public override string KindName {
5647                         get { return "constant"; }
5648                 }
5649
5650                 public override bool IsInstance {
5651                         get { return !IsStatic; }
5652                 }
5653
5654                 public override bool IsStatic {
5655                         get { return true; }
5656                 }
5657
5658                 protected override TypeSpec DeclaringType {
5659                         get { return constant.DeclaringType; }
5660                 }
5661
5662                 public override Expression CreateExpressionTree (ResolveContext ec)
5663                 {
5664                         throw new NotSupportedException ("ET");
5665                 }
5666
5667                 protected override Expression DoResolve (ResolveContext rc)
5668                 {
5669                         ResolveInstanceExpression (rc, null);
5670                         DoBestMemberChecks (rc, constant);
5671
5672                         var c = constant.GetConstant (rc);
5673
5674                         // Creates reference expression to the constant value
5675                         return Constant.CreateConstantFromValue (constant.MemberType, c.GetValue (), loc);
5676                 }
5677
5678                 public override void Emit (EmitContext ec)
5679                 {
5680                         throw new NotSupportedException ();
5681                 }
5682
5683                 public override string GetSignatureForError ()
5684                 {
5685                         return constant.GetSignatureForError ();
5686                 }
5687
5688                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5689                 {
5690                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
5691                 }
5692         }
5693
5694         //
5695         // Fully resolved expression that references a Field
5696         //
5697         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
5698         {
5699                 protected FieldSpec spec;
5700                 VariableInfo variable_info;
5701
5702                 LocalTemporary temp;
5703                 bool prepared;
5704
5705                 protected FieldExpr (Location l)
5706                 {
5707                         loc = l;
5708                 }
5709
5710                 public FieldExpr (FieldSpec spec, Location loc)
5711                 {
5712                         this.spec = spec;
5713                         this.loc = loc;
5714
5715                         type = spec.MemberType;
5716                 }
5717
5718                 public FieldExpr (FieldBase fi, Location l)
5719                         : this (fi.Spec, l)
5720                 {
5721                 }
5722
5723                 #region Properties
5724
5725                 public override string Name {
5726                         get {
5727                                 return spec.Name;
5728                         }
5729                 }
5730
5731                 public bool IsHoisted {
5732                         get {
5733                                 IVariableReference hv = InstanceExpression as IVariableReference;
5734                                 return hv != null && hv.IsHoisted;
5735                         }
5736                 }
5737
5738                 public override bool IsInstance {
5739                         get {
5740                                 return !spec.IsStatic;
5741                         }
5742                 }
5743
5744                 public override bool IsStatic {
5745                         get {
5746                                 return spec.IsStatic;
5747                         }
5748                 }
5749
5750                 public override string KindName {
5751                         get { return "field"; }
5752                 }
5753
5754                 public FieldSpec Spec {
5755                         get {
5756                                 return spec;
5757                         }
5758                 }
5759
5760                 protected override TypeSpec DeclaringType {
5761                         get {
5762                                 return spec.DeclaringType;
5763                         }
5764                 }
5765
5766                 public VariableInfo VariableInfo {
5767                         get {
5768                                 return variable_info;
5769                         }
5770                 }
5771
5772 #endregion
5773
5774                 public override string GetSignatureForError ()
5775                 {
5776                         return spec.GetSignatureForError ();
5777                 }
5778
5779                 public bool IsMarshalByRefAccess (ResolveContext rc)
5780                 {
5781                         // Checks possible ldflda of field access expression
5782                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
5783                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
5784                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
5785                 }
5786
5787                 public void SetHasAddressTaken ()
5788                 {
5789                         IVariableReference vr = InstanceExpression as IVariableReference;
5790                         if (vr != null) {
5791                                 vr.SetHasAddressTaken ();
5792                         }
5793                 }
5794
5795                 protected override void CloneTo (CloneContext clonectx, Expression target)
5796                 {
5797                         var t = (FieldExpr) target;
5798
5799                         if (InstanceExpression != null)
5800                                 t.InstanceExpression = InstanceExpression.Clone (clonectx);
5801                 }
5802
5803                 public override Expression CreateExpressionTree (ResolveContext ec)
5804                 {
5805                         return CreateExpressionTree (ec, true);
5806                 }
5807
5808                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
5809                 {
5810                         Arguments args;
5811                         Expression instance;
5812
5813                         if (InstanceExpression == null) {
5814                                 instance = new NullLiteral (loc);
5815                         } else if (convertInstance) {
5816                                 instance = InstanceExpression.CreateExpressionTree (ec);
5817                         } else {
5818                                 args = new Arguments (1);
5819                                 args.Add (new Argument (InstanceExpression));
5820                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
5821                         }
5822
5823                         args = Arguments.CreateForExpressionTree (ec, null,
5824                                 instance,
5825                                 CreateTypeOfExpression ());
5826
5827                         return CreateExpressionFactoryCall (ec, "Field", args);
5828                 }
5829
5830                 public Expression CreateTypeOfExpression ()
5831                 {
5832                         return new TypeOfField (spec, loc);
5833                 }
5834
5835                 protected override Expression DoResolve (ResolveContext ec)
5836                 {
5837                         spec.MemberDefinition.SetIsUsed ();
5838
5839                         return DoResolve (ec, null);
5840                 }
5841
5842                 Expression DoResolve (ResolveContext ec, Expression rhs)
5843                 {
5844                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
5845
5846                         if (rhs != this) {
5847                                 if (ResolveInstanceExpression (ec, rhs)) {
5848                                         // Resolve the field's instance expression while flow analysis is turned
5849                                         // off: when accessing a field "a.b", we must check whether the field
5850                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
5851
5852                                         if (lvalue_instance) {
5853                                                 bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
5854
5855                                                 Expression right_side =
5856                                                         out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
5857
5858                                                 InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
5859                                         } else {
5860                                                 InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
5861                                         }
5862
5863                                         if (InstanceExpression == null)
5864                                                 return null;
5865                                 }
5866
5867                                 DoBestMemberChecks (ec, spec);
5868                         }
5869
5870                         var fb = spec as FixedFieldSpec;
5871                         IVariableReference var = InstanceExpression as IVariableReference;
5872
5873                         if (fb != null) {
5874                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5875                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
5876                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
5877                                 }
5878
5879                                 if (InstanceExpression.eclass != ExprClass.Variable) {
5880                                         ec.Report.SymbolRelatedToPreviousError (spec);
5881                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
5882                                                 TypeManager.GetFullNameSignature (spec));
5883                                 } else if (var != null && var.IsHoisted) {
5884                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
5885                                 }
5886
5887                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
5888                         }
5889
5890                         //
5891                         // Set flow-analysis variable info for struct member access. It will be check later
5892                         // for precise error reporting
5893                         //
5894                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
5895                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
5896                         }
5897
5898                         eclass = ExprClass.Variable;
5899                         return this;
5900                 }
5901
5902                 public void SetFieldAssigned (FlowAnalysisContext fc)
5903                 {
5904                         if (!IsInstance)
5905                                 return;
5906
5907                         bool lvalue_instance = spec.DeclaringType.IsStruct;
5908                         if (lvalue_instance) {
5909                                 var var = InstanceExpression as IVariableReference;
5910                                 if (var != null && var.VariableInfo != null) {
5911                                         fc.SetStructFieldAssigned (var.VariableInfo, Name);
5912                                 }
5913                         }
5914
5915                         var fe = InstanceExpression as FieldExpr;
5916                         if (fe != null) {
5917                                 Expression instance;
5918
5919                                 do {
5920                                         instance = fe.InstanceExpression;
5921                                         var fe_instance = instance as FieldExpr;
5922                                         if ((fe_instance != null && !fe_instance.IsStatic) || instance is LocalVariableReference) {
5923                                                 if (TypeSpec.IsReferenceType (fe.Type) && instance.Type.IsStruct) {
5924                                                         var var = InstanceExpression as IVariableReference;
5925                                                         if (var != null && var.VariableInfo == null) {
5926                                                                 var var_inst = instance as IVariableReference;
5927                                                                 if (var_inst == null || (var_inst.VariableInfo != null && !fc.IsDefinitelyAssigned (var_inst.VariableInfo)))
5928                                                                         fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5929                                                         }
5930                                                 }
5931
5932                                                 if (fe_instance != null) {
5933                                                         fe = fe_instance;
5934                                                         continue;
5935                                                 }
5936                                         }
5937
5938                                         break;
5939                                 } while (true);
5940
5941                                 if (instance != null && TypeSpec.IsReferenceType (instance.Type))
5942                                         instance.FlowAnalysis (fc);
5943                         } else {
5944                                 if (TypeSpec.IsReferenceType (InstanceExpression.Type))
5945                                         InstanceExpression.FlowAnalysis (fc);
5946                         }
5947                 }
5948
5949                 Expression Error_AssignToReadonly (ResolveContext rc, Expression right_side)
5950                 {
5951                         // The return value is always null.  Returning a value simplifies calling code.
5952
5953                         if (right_side == EmptyExpression.OutAccess) {
5954                                 if (IsStatic) {
5955                                         rc.Report.Error (199, loc, "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5956                                                 GetSignatureForError ());
5957                                 } else {
5958                                         rc.Report.Error (192, loc, "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5959                                                 GetSignatureForError ());
5960                                 }
5961
5962                                 return null;
5963                         }
5964
5965                         if (right_side == EmptyExpression.LValueMemberAccess) {
5966                                 // Already reported as CS1648/CS1650
5967                                 return null;
5968                         }
5969
5970                         if (right_side == EmptyExpression.LValueMemberOutAccess) {
5971                                 if (IsStatic) {
5972                                         rc.Report.Error (1651, loc, "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5973                                                 GetSignatureForError ());
5974                                 } else {
5975                                         rc.Report.Error (1649, loc, "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5976                                                 GetSignatureForError ());
5977                                 }
5978                                 return null;
5979                         }
5980
5981                         if (IsStatic) {
5982                                 rc.Report.Error (198, loc, "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5983                                         GetSignatureForError ());
5984                         } else {
5985                                 rc.Report.Error (191, loc, "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
5986                                         GetSignatureForError ());
5987                         }
5988
5989                         return null;
5990                 }
5991
5992                 override public Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5993                 {
5994                         if (spec is FixedFieldSpec) {
5995                                 // It could be much better error message but we want to be error compatible
5996                                 Error_ValueAssignment (ec, right_side);
5997                         }
5998
5999                         Expression e = DoResolve (ec, right_side);
6000
6001                         if (e == null)
6002                                 return null;
6003
6004                         spec.MemberDefinition.SetIsAssigned ();
6005
6006                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
6007                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
6008                                 ec.Report.Warning (420, 1, loc,
6009                                         "`{0}': A volatile field references will not be treated as volatile",
6010                                         spec.GetSignatureForError ());
6011                         }
6012
6013                         if (spec.IsReadOnly) {
6014                                 // InitOnly fields can only be assigned in constructors or initializers
6015                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
6016                                         return Error_AssignToReadonly (ec, right_side);
6017
6018                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
6019
6020                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
6021                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
6022                                                 return Error_AssignToReadonly (ec, right_side);
6023                                         // static InitOnly fields cannot be assigned-to in an instance constructor
6024                                         if (IsStatic && !ec.IsStatic)
6025                                                 return Error_AssignToReadonly (ec, right_side);
6026                                         // instance constructors can't modify InitOnly fields of other instances of the same type
6027                                         if (!IsStatic && !(InstanceExpression is This))
6028                                                 return Error_AssignToReadonly (ec, right_side);
6029                                 }
6030                         }
6031
6032                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
6033                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
6034                                 ec.Report.Warning (197, 1, loc,
6035                                                 "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",
6036                                                 GetSignatureForError ());
6037                         }
6038
6039                         eclass = ExprClass.Variable;
6040                         return this;
6041                 }
6042
6043                 public override void FlowAnalysis (FlowAnalysisContext fc)
6044                 {
6045                         var var = InstanceExpression as IVariableReference;
6046                         if (var != null) {
6047                                 var vi = var.VariableInfo;
6048                                 if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, Name)) {
6049                                         fc.Report.Error (170, loc, "Use of possibly unassigned field `{0}'", Name);
6050                                         return;
6051                                 }
6052
6053                                 if (TypeSpec.IsValueType (InstanceExpression.Type))
6054                                         return;
6055                         }
6056
6057                         base.FlowAnalysis (fc);
6058                 }
6059
6060                 public override int GetHashCode ()
6061                 {
6062                         return spec.GetHashCode ();
6063                 }
6064
6065                 public bool IsFixed {
6066                         get {
6067                                 //
6068                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
6069                                 //
6070                                 IVariableReference variable = InstanceExpression as IVariableReference;
6071                                 if (variable != null)
6072                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
6073
6074                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6075                                 return fe != null && fe.IsFixed;
6076                         }
6077                 }
6078
6079                 public override bool Equals (object obj)
6080                 {
6081                         FieldExpr fe = obj as FieldExpr;
6082                         if (fe == null)
6083                                 return false;
6084
6085                         if (spec != fe.spec)
6086                                 return false;
6087
6088                         if (InstanceExpression == null || fe.InstanceExpression == null)
6089                                 return true;
6090
6091                         return InstanceExpression.Equals (fe.InstanceExpression);
6092                 }
6093
6094                 public void Emit (EmitContext ec, bool leave_copy)
6095                 {
6096                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6097
6098                         if (IsStatic){
6099                                 if (is_volatile)
6100                                         ec.Emit (OpCodes.Volatile);
6101
6102                                 ec.Emit (OpCodes.Ldsfld, spec);
6103                         } else {
6104                                 if (!prepared)
6105                                         EmitInstance (ec, false);
6106
6107                                 // Optimization for build-in types
6108                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
6109                                         ec.EmitLoadFromPtr (type);
6110                                 } else {
6111                                         var ff = spec as FixedFieldSpec;
6112                                         if (ff != null) {
6113                                                 ec.Emit (OpCodes.Ldflda, spec);
6114                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
6115                                         } else {
6116                                                 if (is_volatile)
6117                                                         ec.Emit (OpCodes.Volatile);
6118
6119                                                 ec.Emit (OpCodes.Ldfld, spec);
6120                                         }
6121                                 }
6122                         }
6123
6124                         if (leave_copy) {
6125                                 ec.Emit (OpCodes.Dup);
6126                                 if (!IsStatic) {
6127                                         temp = new LocalTemporary (this.Type);
6128                                         temp.Store (ec);
6129                                 }
6130                         }
6131                 }
6132
6133                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6134                 {
6135                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
6136                         if (isCompound && !(source is DynamicExpressionStatement)) {
6137                                 if (has_await_source) {
6138                                         if (IsInstance)
6139                                                 InstanceExpression = InstanceExpression.EmitToField (ec);
6140                                 } else {
6141                                         prepared = true;
6142                                 }
6143                         }
6144
6145                         if (IsInstance) {
6146                                 if (has_await_source)
6147                                         source = source.EmitToField (ec);
6148
6149                                 EmitInstance (ec, prepared);
6150                         }
6151
6152                         source.Emit (ec);
6153
6154                         if (leave_copy) {
6155                                 ec.Emit (OpCodes.Dup);
6156                                 if (!IsStatic) {
6157                                         temp = new LocalTemporary (this.Type);
6158                                         temp.Store (ec);
6159                                 }
6160                         }
6161
6162                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
6163                                 ec.Emit (OpCodes.Volatile);
6164
6165                         spec.MemberDefinition.SetIsAssigned ();
6166
6167                         if (IsStatic)
6168                                 ec.Emit (OpCodes.Stsfld, spec);
6169                         else
6170                                 ec.Emit (OpCodes.Stfld, spec);
6171
6172                         if (temp != null) {
6173                                 temp.Emit (ec);
6174                                 temp.Release (ec);
6175                                 temp = null;
6176                         }
6177                 }
6178
6179                 //
6180                 // Emits store to field with prepared values on stack
6181                 //
6182                 public void EmitAssignFromStack (EmitContext ec)
6183                 {
6184                         if (IsStatic) {
6185                                 ec.Emit (OpCodes.Stsfld, spec);
6186                         } else {
6187                                 ec.Emit (OpCodes.Stfld, spec);
6188                         }
6189                 }
6190
6191                 public override void Emit (EmitContext ec)
6192                 {
6193                         Emit (ec, false);
6194                 }
6195
6196                 public override void EmitSideEffect (EmitContext ec)
6197                 {
6198                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6199
6200                         if (is_volatile) // || is_marshal_by_ref ())
6201                                 base.EmitSideEffect (ec);
6202                 }
6203
6204                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
6205                 {
6206                         if ((mode & AddressOp.Store) != 0)
6207                                 spec.MemberDefinition.SetIsAssigned ();
6208                         if ((mode & AddressOp.Load) != 0)
6209                                 spec.MemberDefinition.SetIsUsed ();
6210
6211                         //
6212                         // Handle initonly fields specially: make a copy and then
6213                         // get the address of the copy.
6214                         //
6215                         bool need_copy;
6216                         if (spec.IsReadOnly){
6217                                 need_copy = true;
6218                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
6219                                         if (IsStatic){
6220                                                 if (ec.IsStatic)
6221                                                         need_copy = false;
6222                                         } else
6223                                                 need_copy = false;
6224                                 }
6225                         } else
6226                                 need_copy = false;
6227
6228                         if (need_copy) {
6229                                 Emit (ec);
6230                                 var temp = ec.GetTemporaryLocal (type);
6231                                 ec.Emit (OpCodes.Stloc, temp);
6232                                 ec.Emit (OpCodes.Ldloca, temp);
6233                                 ec.FreeTemporaryLocal (temp, type);
6234                                 return;
6235                         }
6236
6237
6238                         if (IsStatic){
6239                                 ec.Emit (OpCodes.Ldsflda, spec);
6240                         } else {
6241                                 if (!prepared)
6242                                         EmitInstance (ec, false);
6243                                 ec.Emit (OpCodes.Ldflda, spec);
6244                         }
6245                 }
6246
6247                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6248                 {
6249                         return MakeExpression (ctx);
6250                 }
6251
6252                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6253                 {
6254 #if STATIC
6255                         return base.MakeExpression (ctx);
6256 #else
6257                         return SLE.Expression.Field (
6258                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
6259                                 spec.GetMetaInfo ());
6260 #endif
6261                 }
6262
6263                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6264                 {
6265                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
6266                 }
6267         }
6268
6269
6270         //
6271         // Expression that evaluates to a Property.
6272         //
6273         // This is not an LValue because we need to re-write the expression. We
6274         // can not take data from the stack and store it.
6275         //
6276         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
6277         {
6278                 Arguments arguments;
6279
6280                 public PropertyExpr (PropertySpec spec, Location l)
6281                         : base (l)
6282                 {
6283                         best_candidate = spec;
6284                         type = spec.MemberType;
6285                 }
6286
6287                 #region Properties
6288
6289                 protected override Arguments Arguments {
6290                         get {
6291                                 return arguments;
6292                         }
6293                         set {
6294                                 arguments = value;
6295                         }
6296                 }
6297
6298                 protected override TypeSpec DeclaringType {
6299                         get {
6300                                 return best_candidate.DeclaringType;
6301                         }
6302                 }
6303
6304                 public override string Name {
6305                         get {
6306                                 return best_candidate.Name;
6307                         }
6308                 }
6309
6310                 public override bool IsInstance {
6311                         get {
6312                                 return !IsStatic;
6313                         }
6314                 }
6315
6316                 public override bool IsStatic {
6317                         get {
6318                                 return best_candidate.IsStatic;
6319                         }
6320                 }
6321
6322                 public override string KindName {
6323                         get { return "property"; }
6324                 }
6325
6326                 public PropertySpec PropertyInfo {
6327                         get {
6328                                 return best_candidate;
6329                         }
6330                 }
6331
6332                 #endregion
6333
6334                 public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
6335                 {
6336                         if (best_candidate == null || !(best_candidate.IsStatic || InstanceExpression is This))
6337                                 return null;
6338
6339                         var args_count = arguments == null ? 0 : arguments.Count;
6340                         if (args_count != body.Parameters.Count && args_count == 0)
6341                                 return null;
6342
6343                         var mg = MethodGroupExpr.CreatePredefined (best_candidate.Get, DeclaringType, loc);
6344                         mg.InstanceExpression = InstanceExpression;
6345
6346                         return mg;
6347                 }
6348
6349                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
6350                 {
6351                         return new PropertyExpr (spec, loc) {
6352                                 Getter = spec.Get,
6353                                 Setter = spec.Set
6354                         };
6355                 }
6356
6357                 public override Expression CreateExpressionTree (ResolveContext ec)
6358                 {
6359                         Arguments args;
6360                         if (IsSingleDimensionalArrayLength ()) {
6361                                 args = new Arguments (1);
6362                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6363                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
6364                         }
6365
6366                         args = new Arguments (2);
6367                         if (InstanceExpression == null)
6368                                 args.Add (new Argument (new NullLiteral (loc)));
6369                         else
6370                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6371                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
6372                         return CreateExpressionFactoryCall (ec, "Property", args);
6373                 }
6374
6375                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
6376                 {
6377                         DoResolveLValue (rc, null);
6378                         return new TypeOfMethod (Setter, loc);
6379                 }
6380
6381                 public override string GetSignatureForError ()
6382                 {
6383                         return best_candidate.GetSignatureForError ();
6384                 }
6385
6386                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6387                 {
6388 #if STATIC
6389                         return base.MakeExpression (ctx);
6390 #else
6391                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
6392 #endif
6393                 }
6394
6395                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6396                 {
6397 #if STATIC
6398                         return base.MakeExpression (ctx);
6399 #else
6400                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
6401 #endif
6402                 }
6403
6404                 void Error_PropertyNotValid (ResolveContext ec)
6405                 {
6406                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
6407                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
6408                                 GetSignatureForError ());
6409                 }
6410
6411                 bool IsSingleDimensionalArrayLength ()
6412                 {
6413                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
6414                                 return false;
6415
6416                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
6417                         return ac != null && ac.Rank == 1;
6418                 }
6419
6420                 public override void Emit (EmitContext ec, bool leave_copy)
6421                 {
6422                         //
6423                         // Special case: length of single dimension array property is turned into ldlen
6424                         //
6425                         if (IsSingleDimensionalArrayLength ()) {
6426                                 EmitInstance (ec, false);
6427                                 ec.Emit (OpCodes.Ldlen);
6428                                 ec.Emit (OpCodes.Conv_I4);
6429                                 return;
6430                         }
6431
6432                         base.Emit (ec, leave_copy);
6433                 }
6434
6435                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6436                 {
6437                         Arguments args;
6438                         LocalTemporary await_source_arg = null;
6439
6440                         if (isCompound && !(source is DynamicExpressionStatement)) {
6441                                 emitting_compound_assignment = true;
6442                                 source.Emit (ec);
6443
6444                                 if (has_await_arguments) {
6445                                         await_source_arg = new LocalTemporary (Type);
6446                                         await_source_arg.Store (ec);
6447
6448                                         args = new Arguments (1);
6449                                         args.Add (new Argument (await_source_arg));
6450
6451                                         if (leave_copy) {
6452                                                 temp = await_source_arg;
6453                                         }
6454
6455                                         has_await_arguments = false;
6456                                 } else {
6457                                         args = null;
6458
6459                                         if (leave_copy) {
6460                                                 ec.Emit (OpCodes.Dup);
6461                                                 temp = new LocalTemporary (this.Type);
6462                                                 temp.Store (ec);
6463                                         }
6464                                 }
6465                         } else {
6466                                 args = arguments ?? new Arguments (1);
6467
6468                                 if (leave_copy) {
6469                                         source.Emit (ec);
6470                                         temp = new LocalTemporary (this.Type);
6471                                         temp.Store (ec);
6472                                         args.Add (new Argument (temp));
6473                                 } else {
6474                                         args.Add (new Argument (source));
6475                                 }
6476                         }
6477
6478                         emitting_compound_assignment = false;
6479
6480                         var call = new CallEmitter ();
6481                         call.InstanceExpression = InstanceExpression;
6482                         if (args == null)
6483                                 call.InstanceExpressionOnStack = true;
6484
6485                         call.Emit (ec, Setter, args, loc);
6486
6487                         if (temp != null) {
6488                                 temp.Emit (ec);
6489                                 temp.Release (ec);
6490                         }
6491
6492                         if (await_source_arg != null) {
6493                                 await_source_arg.Release (ec);
6494                         }
6495                 }
6496
6497                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
6498                 {
6499                         eclass = ExprClass.PropertyAccess;
6500
6501                         if (best_candidate.IsNotCSharpCompatible) {
6502                                 Error_PropertyNotValid (rc);
6503                         }
6504
6505                         ResolveInstanceExpression (rc, right_side);
6506
6507                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
6508                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
6509                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
6510                                 if (p != null) {
6511                                         type = p.MemberType;
6512                                 }
6513                         }
6514
6515                         DoBestMemberChecks (rc, best_candidate);
6516
6517                         // Handling of com-imported properties with any number of default property parameters
6518                         if (best_candidate.HasGet && !best_candidate.Get.Parameters.IsEmpty) {
6519                                 var p = best_candidate.Get.Parameters;
6520                                 arguments = new Arguments (p.Count);
6521                                 for (int i = 0; i < p.Count; ++i) {
6522                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6523                                 }
6524                         } else if (best_candidate.HasSet && best_candidate.Set.Parameters.Count > 1) {
6525                                 var p = best_candidate.Set.Parameters;
6526                                 arguments = new Arguments (p.Count - 1);
6527                                 for (int i = 0; i < p.Count - 1; ++i) {
6528                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6529                                 }
6530                         }
6531
6532                         return this;
6533                 }
6534
6535                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6536                 {
6537                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
6538                 }
6539         }
6540
6541         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
6542         {
6543                 // getter and setter can be different for base calls
6544                 MethodSpec getter, setter;
6545                 protected T best_candidate;
6546
6547                 protected LocalTemporary temp;
6548                 protected bool emitting_compound_assignment;
6549                 protected bool has_await_arguments;
6550
6551                 protected PropertyOrIndexerExpr (Location l)
6552                 {
6553                         loc = l;
6554                 }
6555
6556                 #region Properties
6557
6558                 protected abstract Arguments Arguments { get; set; }
6559
6560                 public MethodSpec Getter {
6561                         get {
6562                                 return getter;
6563                         }
6564                         set {
6565                                 getter = value;
6566                         }
6567                 }
6568
6569                 public MethodSpec Setter {
6570                         get {
6571                                 return setter;
6572                         }
6573                         set {
6574                                 setter = value;
6575                         }
6576                 }
6577
6578                 #endregion
6579
6580                 protected override Expression DoResolve (ResolveContext ec)
6581                 {
6582                         if (eclass == ExprClass.Unresolved) {
6583                                 var expr = OverloadResolve (ec, null);
6584                                 if (expr == null)
6585                                         return null;
6586
6587                                 if (expr != this)
6588                                         return expr.Resolve (ec);
6589                         }
6590
6591                         if (!ResolveGetter (ec))
6592                                 return null;
6593
6594                         return this;
6595                 }
6596
6597                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6598                 {
6599                         if (right_side == EmptyExpression.OutAccess) {
6600                                 // TODO: best_candidate can be null at this point
6601                                 INamedBlockVariable variable = null;
6602                                 if (best_candidate != null && ec.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, ec.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
6603                                         ec.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
6604                                                 best_candidate.Name);
6605                                 } else {
6606                                         right_side.DoResolveLValue (ec, this);
6607                                 }
6608                                 return null;
6609                         }
6610
6611                         if (eclass == ExprClass.Unresolved) {
6612                                 var expr = OverloadResolve (ec, right_side);
6613                                 if (expr == null)
6614                                         return null;
6615
6616                                 if (expr != this)
6617                                         return expr.ResolveLValue (ec, right_side);
6618                         } else {
6619                                 ResolveInstanceExpression (ec, right_side);
6620                         }
6621
6622                         if (!ResolveSetter (ec))
6623                                 return null;
6624
6625                         return this;
6626                 }
6627
6628                 //
6629                 // Implements the IAssignMethod interface for assignments
6630                 //
6631                 public virtual void Emit (EmitContext ec, bool leave_copy)
6632                 {
6633                         var call = new CallEmitter ();
6634                         call.InstanceExpression = InstanceExpression;
6635                         if (has_await_arguments)
6636                                 call.HasAwaitArguments = true;
6637                         else
6638                                 call.DuplicateArguments = emitting_compound_assignment;
6639
6640                         call.Emit (ec, Getter, Arguments, loc);
6641
6642                         if (call.HasAwaitArguments) {
6643                                 InstanceExpression = call.InstanceExpression;
6644                                 Arguments = call.EmittedArguments;
6645                                 has_await_arguments = true;
6646                         }
6647
6648                         if (leave_copy) {
6649                                 ec.Emit (OpCodes.Dup);
6650                                 temp = new LocalTemporary (Type);
6651                                 temp.Store (ec);
6652                         }
6653                 }
6654
6655                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
6656
6657                 public override void Emit (EmitContext ec)
6658                 {
6659                         Emit (ec, false);
6660                 }
6661
6662                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
6663                 {
6664                         has_await_arguments = true;
6665                         Emit (ec, false);
6666                         return null;
6667                 }
6668
6669                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
6670
6671                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
6672
6673                 bool ResolveGetter (ResolveContext rc)
6674                 {
6675                         if (!best_candidate.HasGet) {
6676                                 if (InstanceExpression != EmptyExpression.Null) {
6677                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
6678                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
6679                                                 best_candidate.GetSignatureForError ());
6680                                         return false;
6681                                 }
6682                         } else if (!best_candidate.Get.IsAccessible (rc) || !best_candidate.Get.DeclaringType.IsAccessible (rc)) {
6683                                 if (best_candidate.HasDifferentAccessibility) {
6684                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6685                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
6686                                                 TypeManager.CSharpSignature (best_candidate));
6687                                 } else {
6688                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6689                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
6690                                 }
6691                         }
6692
6693                         if (best_candidate.HasDifferentAccessibility) {
6694                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
6695                         }
6696
6697                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
6698                         return true;
6699                 }
6700
6701                 bool ResolveSetter (ResolveContext rc)
6702                 {
6703                         if (!best_candidate.HasSet) {
6704                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
6705                                         GetSignatureForError ());
6706                                 return false;
6707                         }
6708
6709                         if (!best_candidate.Set.IsAccessible (rc) || !best_candidate.Set.DeclaringType.IsAccessible (rc)) {
6710                                 if (best_candidate.HasDifferentAccessibility) {
6711                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6712                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
6713                                                 GetSignatureForError ());
6714                                 } else {
6715                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6716                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
6717                                 }
6718                         }
6719
6720                         if (best_candidate.HasDifferentAccessibility)
6721                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
6722
6723                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
6724                         return true;
6725                 }
6726         }
6727
6728         /// <summary>
6729         ///   Fully resolved expression that evaluates to an Event
6730         /// </summary>
6731         public class EventExpr : MemberExpr, IAssignMethod
6732         {
6733                 readonly EventSpec spec;
6734                 MethodSpec op;
6735
6736                 public EventExpr (EventSpec spec, Location loc)
6737                 {
6738                         this.spec = spec;
6739                         this.loc = loc;
6740                 }
6741
6742                 #region Properties
6743
6744                 protected override TypeSpec DeclaringType {
6745                         get {
6746                                 return spec.DeclaringType;
6747                         }
6748                 }
6749
6750                 public override string Name {
6751                         get {
6752                                 return spec.Name;
6753                         }
6754                 }
6755
6756                 public override bool IsInstance {
6757                         get {
6758                                 return !spec.IsStatic;
6759                         }
6760                 }
6761
6762                 public override bool IsStatic {
6763                         get {
6764                                 return spec.IsStatic;
6765                         }
6766                 }
6767
6768                 public override string KindName {
6769                         get { return "event"; }
6770                 }
6771
6772                 public MethodSpec Operator {
6773                         get {
6774                                 return op;
6775                         }
6776                 }
6777
6778                 #endregion
6779
6780                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
6781                 {
6782                         //
6783                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
6784                         //
6785                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6786                                 if (spec.BackingField != null &&
6787                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
6788
6789                                         spec.MemberDefinition.SetIsUsed ();
6790
6791                                         if (!ec.IsObsolete) {
6792                                                 ObsoleteAttribute oa = spec.GetAttributeObsolete ();
6793                                                 if (oa != null)
6794                                                         AttributeTester.Report_ObsoleteMessage (oa, spec.GetSignatureForError (), loc, ec.Report);
6795                                         }
6796
6797                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
6798                                                 Error_AssignmentEventOnly (ec);
6799
6800                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
6801
6802                                         InstanceExpression = null;
6803
6804                                         return ml.ResolveMemberAccess (ec, left, original);
6805                                 }
6806                         }
6807
6808                         return base.ResolveMemberAccess (ec, left, original);
6809                 }
6810
6811                 public override Expression CreateExpressionTree (ResolveContext ec)
6812                 {
6813                         throw new NotSupportedException ("ET");
6814                 }
6815
6816                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6817                 {
6818                         if (right_side == EmptyExpression.EventAddition) {
6819                                 op = spec.AccessorAdd;
6820                         } else if (right_side == EmptyExpression.EventSubtraction) {
6821                                 op = spec.AccessorRemove;
6822                         }
6823
6824                         if (op == null) {
6825                                 Error_AssignmentEventOnly (ec);
6826                                 return null;
6827                         }
6828
6829                         op = CandidateToBaseOverride (ec, op);
6830                         return this;
6831                 }
6832
6833                 protected override Expression DoResolve (ResolveContext ec)
6834                 {
6835                         eclass = ExprClass.EventAccess;
6836                         type = spec.MemberType;
6837
6838                         ResolveInstanceExpression (ec, null);
6839
6840                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6841                                 Error_AssignmentEventOnly (ec);
6842                         }
6843
6844                         DoBestMemberChecks (ec, spec);
6845                         return this;
6846                 }
6847
6848                 public override void Emit (EmitContext ec)
6849                 {
6850                         throw new NotSupportedException ();
6851                         //Error_CannotAssign ();
6852                 }
6853
6854                 #region IAssignMethod Members
6855
6856                 public void Emit (EmitContext ec, bool leave_copy)
6857                 {
6858                         throw new NotImplementedException ();
6859                 }
6860
6861                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6862                 {
6863                         if (leave_copy || !isCompound)
6864                                 throw new NotImplementedException ("EventExpr::EmitAssign");
6865
6866                         Arguments args = new Arguments (1);
6867                         args.Add (new Argument (source));
6868
6869                         var call = new CallEmitter ();
6870                         call.InstanceExpression = InstanceExpression;
6871                         call.Emit (ec, op, args, loc);
6872                 }
6873
6874                 #endregion
6875
6876                 void Error_AssignmentEventOnly (ResolveContext ec)
6877                 {
6878                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
6879                                 ec.Report.Error (79, loc,
6880                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
6881                                         GetSignatureForError ());
6882                         } else {
6883                                 ec.Report.Error (70, loc,
6884                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
6885                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
6886                         }
6887                 }
6888
6889                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
6890                 {
6891                         name = name.Substring (0, name.LastIndexOf ('.'));
6892                         base.Error_CannotCallAbstractBase (rc, name);
6893                 }
6894
6895                 public override string GetSignatureForError ()
6896                 {
6897                         return TypeManager.CSharpSignature (spec);
6898                 }
6899
6900                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6901                 {
6902                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
6903                 }
6904         }
6905
6906         public class TemporaryVariableReference : VariableReference
6907         {
6908                 public class Declarator : Statement
6909                 {
6910                         TemporaryVariableReference variable;
6911
6912                         public Declarator (TemporaryVariableReference variable)
6913                         {
6914                                 this.variable = variable;
6915                                 loc = variable.loc;
6916                         }
6917
6918                         protected override void DoEmit (EmitContext ec)
6919                         {
6920                                 variable.li.CreateBuilder (ec);
6921                         }
6922
6923                         public override void Emit (EmitContext ec)
6924                         {
6925                                 // Don't create sequence point
6926                                 DoEmit (ec);
6927                         }
6928
6929                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6930                         {
6931                                 return false;
6932                         }
6933
6934                         protected override void CloneTo (CloneContext clonectx, Statement target)
6935                         {
6936                                 // Nothing
6937                         }
6938                 }
6939
6940                 LocalVariable li;
6941
6942                 public TemporaryVariableReference (LocalVariable li, Location loc)
6943                 {
6944                         this.li = li;
6945                         this.type = li.Type;
6946                         this.loc = loc;
6947                 }
6948
6949                 public override bool IsLockedByStatement {
6950                         get {
6951                                 return false;
6952                         }
6953                         set {
6954                         }
6955                 }
6956
6957                 public LocalVariable LocalInfo {
6958                     get {
6959                         return li;
6960                     }
6961                 }
6962
6963                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc)
6964                 {
6965                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc);
6966                         return new TemporaryVariableReference (li, loc);
6967                 }
6968
6969                 protected override Expression DoResolve (ResolveContext ec)
6970                 {
6971                         eclass = ExprClass.Variable;
6972
6973                         //
6974                         // Don't capture temporary variables except when using
6975                         // state machine redirection and block yields
6976                         //
6977                         if (ec.CurrentAnonymousMethod is StateMachineInitializer &&
6978                                 (ec.CurrentBlock.Explicit.HasYield || ec.CurrentBlock.Explicit.HasAwait) &&
6979                                 ec.IsVariableCapturingRequired) {
6980                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
6981                                 storey.CaptureLocalVariable (ec, li);
6982                         }
6983
6984                         return this;
6985                 }
6986
6987                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6988                 {
6989                         return Resolve (ec);
6990                 }
6991
6992                 public override void Emit (EmitContext ec)
6993                 {
6994                         li.CreateBuilder (ec);
6995
6996                         Emit (ec, false);
6997                 }
6998
6999                 public void EmitAssign (EmitContext ec, Expression source)
7000                 {
7001                         li.CreateBuilder (ec);
7002
7003                         EmitAssign (ec, source, false, false);
7004                 }
7005
7006                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
7007                 {
7008                         return li.HoistedVariant;
7009                 }
7010
7011                 public override bool IsFixed {
7012                         get { return true; }
7013                 }
7014
7015                 public override bool IsRef {
7016                         get { return false; }
7017                 }
7018
7019                 public override string Name {
7020                         get { throw new NotImplementedException (); }
7021                 }
7022
7023                 public override void SetHasAddressTaken ()
7024                 {
7025                         throw new NotImplementedException ();
7026                 }
7027
7028                 protected override ILocalVariable Variable {
7029                         get { return li; }
7030                 }
7031
7032                 public override VariableInfo VariableInfo {
7033                         get { return null; }
7034                 }
7035         }
7036
7037         ///
7038         /// Handles `var' contextual keyword; var becomes a keyword only
7039         /// if no type called var exists in a variable scope
7040         ///
7041         class VarExpr : SimpleName
7042         {
7043                 public VarExpr (Location loc)
7044                         : base ("var", loc)
7045                 {
7046                 }
7047
7048                 public bool InferType (ResolveContext ec, Expression right_side)
7049                 {
7050                         if (type != null)
7051                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
7052
7053                         type = right_side.Type;
7054                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
7055                                 ec.Report.Error (815, loc,
7056                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
7057                                         type.GetSignatureForError ());
7058                                 return false;
7059                         }
7060
7061                         eclass = ExprClass.Variable;
7062                         return true;
7063                 }
7064
7065                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
7066                 {
7067                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
7068                                 base.Error_TypeOrNamespaceNotFound (ec);
7069                         else
7070                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
7071                 }
7072         }
7073 }