mcs/mcs/ecore.cs

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