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 (!pe.PropertyInfo.HasSet || !pe.PropertyInfo.Set.IsAccessible (rc))
2868                                                                         break;
2869
2870                                                                 pe.Setter = pe.PropertyInfo.Set;
2871                                                         }
2872                                                 }
2873                                         }
2874
2875                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2876                                         // TODO: Should go to MemberAccess
2877                                         me = me.ResolveMemberAccess (rc, null, null);
2878
2879                                         if (Arity > 0) {
2880                                                 targs.Resolve (rc, false);
2881                                                 me.SetTypeArguments (rc, targs);
2882                                         }
2883
2884                                         return me;
2885                                 }
2886
2887                                 //
2888                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2889                                 //
2890                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2891                                         if (IsPossibleTypeOrNamespace (rc)) {
2892                                                 return ResolveAsTypeOrNamespace (rc, false);
2893                                         }
2894                                 }
2895
2896                                 var expr = NamespaceContainer.LookupStaticUsings (rc, Name, Arity, loc);
2897                                 if (expr != null) {
2898                                         if (Arity > 0) {
2899                                                 targs.Resolve (rc, false);
2900
2901                                                 var me = expr as MemberExpr;
2902                                                 if (me != null)
2903                                                         me.SetTypeArguments (rc, targs);
2904                                         }
2905                                         return expr;
2906                                 }
2907
2908                                 if ((restrictions & MemberLookupRestrictions.NameOfExcluded) == 0 && Name == "nameof")
2909                                         return new NameOf (this);
2910
2911                                 if (errorMode) {
2912                                         if (variable_found) {
2913                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2914                                         } else {
2915                                                 if (Arity > 0) {
2916                                                         var tparams = rc.CurrentTypeParameters;
2917                                                         if (tparams != null) {
2918                                                                 if (tparams.Find (Name) != null) {
2919                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2920                                                                         return null;
2921                                                                 }
2922                                                         }
2923
2924                                                         var ct = rc.CurrentType;
2925                                                         do {
2926                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2927                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2928                                                                                 if (ctp.Name == Name) {
2929                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2930                                                                                         return null;
2931                                                                                 }
2932                                                                         }
2933                                                                 }
2934
2935                                                                 ct = ct.DeclaringType;
2936                                                         } while (ct != null);
2937                                                 }
2938
2939                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2940                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2941                                                         if (e != null) {
2942                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2943                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2944                                                                 return e;
2945                                                         }
2946                                                 } else {
2947                                                         var me = MemberLookup (rc, false, rc.CurrentType, Name, Arity, restrictions & ~MemberLookupRestrictions.InvocableOnly, loc) as MemberExpr;
2948                                                         if (me != null) {
2949                                                                 Error_UnexpectedKind (rc, me, "method group", me.KindName, loc);
2950                                                                 return ErrorExpression.Instance;
2951                                                         }
2952                                                 }
2953
2954                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2955                                                 if (e != null) {
2956                                                         if (e.Type.Arity != Arity && (restrictions & MemberLookupRestrictions.IgnoreArity) == 0) {
2957                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, loc);
2958                                                                 return e;
2959                                                         }
2960
2961                                                         if (e is TypeExpr) {
2962                                                                 // TypeExpression does not have correct location
2963                                                                 if (e is TypeExpression)
2964                                                                         e = new TypeExpression (e.Type, loc);
2965
2966                                                                 return e;
2967                                                         }
2968                                                 }
2969
2970                                                 Error_NameDoesNotExist (rc);
2971                                         }
2972
2973                                         return ErrorExpression.Instance;
2974                                 }
2975
2976                                 if (rc.Module.Evaluator != null) {
2977                                         var fi = rc.Module.Evaluator.LookupField (Name);
2978                                         if (fi != null)
2979                                                 return new FieldExpr (fi.Item1, loc);
2980                                 }
2981
2982                                 lookup_arity = 0;
2983                                 errorMode = true;
2984                         }
2985                 }
2986
2987                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side)
2988                 {
2989                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2990
2991                         if (e == null)
2992                                 return null;
2993
2994                         if (e is FullNamedExpression && e.eclass != ExprClass.Unresolved) {
2995                                 Error_UnexpectedKind (ec, e, "variable", e.ExprClassName, loc);
2996                                 return e;
2997                         }
2998
2999                         if (right_side != null) {
3000                                 e = e.ResolveLValue (ec, right_side);
3001                         } else {
3002                                 e = e.Resolve (ec);
3003                         }
3004
3005                         return e;
3006                 }
3007
3008                 public override object Accept (StructuralVisitor visitor)
3009                 {
3010                         return visitor.Visit (this);
3011                 }
3012         }
3013
3014         /// <summary>
3015         ///   Represents a namespace or a type.  The name of the class was inspired by
3016         ///   section 10.8.1 (Fully Qualified Names).
3017         /// </summary>
3018         public abstract class FullNamedExpression : Expression
3019         {
3020                 protected override void CloneTo (CloneContext clonectx, Expression target)
3021                 {
3022                         // Do nothing, most unresolved type expressions cannot be
3023                         // resolved to different type
3024                 }
3025
3026                 public override bool ContainsEmitWithAwait ()
3027                 {
3028                         return false;
3029                 }
3030
3031                 public override Expression CreateExpressionTree (ResolveContext ec)
3032                 {
3033                         throw new NotSupportedException ("ET");
3034                 }
3035
3036                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments);
3037
3038                 //
3039                 // This is used to resolve the expression as a type, a null
3040                 // value will be returned if the expression is not a type
3041                 // reference
3042                 //
3043                 public override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
3044                 {
3045                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc, allowUnboundTypeArguments);
3046
3047                         if (fne == null)
3048                                 return null;
3049
3050                         TypeExpr te = fne as TypeExpr;
3051                         if (te == null) {
3052                                 Error_UnexpectedKind (mc, fne, "type", fne.ExprClassName, loc);
3053                                 return null;
3054                         }
3055
3056                         te.loc = loc;
3057
3058                         type = te.Type;
3059
3060                         var dep = type.GetMissingDependencies ();
3061                         if (dep != null) {
3062                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
3063                         }
3064
3065                         if (type.Kind == MemberKind.Void) {
3066                                 mc.Module.Compiler.Report.Error (673, loc, "System.Void cannot be used from C#. Consider using `void'");
3067                         }
3068
3069                         //
3070                         // Obsolete checks cannot be done when resolving base context as they
3071                         // require type dependencies to be set but we are in process of resolving them
3072                         //
3073                         if (!(mc is TypeDefinition.BaseContext) && !(mc is UsingAliasNamespace.AliasContext)) {
3074                                 ObsoleteAttribute obsolete_attr = type.GetAttributeObsolete ();
3075                                 if (obsolete_attr != null && !mc.IsObsolete) {
3076                                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location, mc.Module.Compiler.Report);
3077                                 }
3078                         }
3079
3080                         return type;
3081                 }
3082
3083
3084                 public override void Emit (EmitContext ec)
3085                 {
3086                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
3087                                 GetSignatureForError ());
3088                 }
3089         }
3090
3091         /// <summary>
3092         ///   Expression that evaluates to a type
3093         /// </summary>
3094         public abstract class TypeExpr : FullNamedExpression
3095         {
3096                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
3097                 {
3098                         ResolveAsType (mc);
3099                         return this;
3100                 }
3101
3102                 protected sealed override Expression DoResolve (ResolveContext ec)
3103                 {
3104                         ResolveAsType (ec);
3105                         return this;
3106                 }
3107
3108                 public override bool Equals (object obj)
3109                 {
3110                         TypeExpr tobj = obj as TypeExpr;
3111                         if (tobj == null)
3112                                 return false;
3113
3114                         return Type == tobj.Type;
3115                 }
3116
3117                 public override int GetHashCode ()
3118                 {
3119                         return Type.GetHashCode ();
3120                 }
3121         }
3122
3123         /// <summary>
3124         ///   Fully resolved Expression that already evaluated to a type
3125         /// </summary>
3126         public class TypeExpression : TypeExpr
3127         {
3128                 public TypeExpression (TypeSpec t, Location l)
3129                 {
3130                         Type = t;
3131                         eclass = ExprClass.Type;
3132                         loc = l;
3133                 }
3134
3135                 public sealed override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
3136                 {
3137                         return type;
3138                 }
3139         }
3140
3141         public class NamespaceExpression : FullNamedExpression
3142         {
3143                 readonly Namespace ns;
3144
3145                 public NamespaceExpression (Namespace ns, Location loc)
3146                 {
3147                         this.ns = ns;
3148                         this.Type = InternalType.Namespace;
3149                         this.eclass = ExprClass.Namespace;
3150                         this.loc = loc;
3151                 }
3152
3153                 public Namespace Namespace {
3154                         get {
3155                                 return ns;
3156                         }
3157                 }
3158
3159                 protected override Expression DoResolve (ResolveContext rc)
3160                 {
3161                         throw new NotImplementedException ();
3162                 }
3163
3164                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
3165                 {
3166                         return this;
3167                 }
3168
3169                 public void Error_NamespaceDoesNotExist (IMemberContext ctx, string name, int arity, Location loc)
3170                 {
3171                         var retval = Namespace.LookupType (ctx, name, arity, LookupMode.IgnoreAccessibility, loc);
3172                         if (retval != null) {
3173 //                              ctx.Module.Compiler.Report.SymbolRelatedToPreviousError (retval.MemberDefinition);
3174                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
3175                                 return;
3176                         }
3177
3178                         retval = Namespace.LookupType (ctx, name, -System.Math.Max (1, arity), LookupMode.Probing, loc);
3179                         if (retval != null) {
3180                                 Error_TypeArgumentsCannotBeUsed (ctx, retval, loc);
3181                                 return;
3182                         }
3183
3184                         Namespace ns;
3185                         if (arity > 0 && Namespace.TryGetNamespace (name, out ns)) {
3186                                 Error_TypeArgumentsCannotBeUsed (ctx, ExprClassName, ns.GetSignatureForError (), loc);
3187                                 return;
3188                         }
3189
3190                         string assembly = null;
3191                         string possible_name = Namespace.GetSignatureForError () + "." + name;
3192
3193                         // Only assembly unique name should be added
3194                         switch (possible_name) {
3195                         case "System.Drawing":
3196                         case "System.Web.Services":
3197                         case "System.Web":
3198                         case "System.Data":
3199                         case "System.Configuration":
3200                         case "System.Data.Services":
3201                         case "System.DirectoryServices":
3202                         case "System.Json":
3203                         case "System.Net.Http":
3204                         case "System.Numerics":
3205                         case "System.Runtime.Caching":
3206                         case "System.ServiceModel":
3207                         case "System.Transactions":
3208                         case "System.Web.Routing":
3209                         case "System.Xml.Linq":
3210                         case "System.Xml":
3211                                 assembly = possible_name;
3212                                 break;
3213
3214                         case "System.Linq":
3215                         case "System.Linq.Expressions":
3216                                 assembly = "System.Core";
3217                                 break;
3218
3219                         case "System.Windows.Forms":
3220                         case "System.Windows.Forms.Layout":
3221                                 assembly = "System.Windows.Forms";
3222                                 break;
3223                         }
3224
3225                         assembly = assembly == null ? "an" : "`" + assembly + "'";
3226
3227                         if (Namespace is GlobalRootNamespace) {
3228                                 ctx.Module.Compiler.Report.Error (400, loc,
3229                                         "The type or namespace name `{0}' could not be found in the global namespace. Are you missing {1} assembly reference?",
3230                                         name, assembly);
3231                         } else {
3232                                 ctx.Module.Compiler.Report.Error (234, loc,
3233                                         "The type or namespace name `{0}' does not exist in the namespace `{1}'. Are you missing {2} assembly reference?",
3234                                         name, GetSignatureForError (), assembly);
3235                         }
3236                 }
3237
3238                 public override string GetSignatureForError ()
3239                 {
3240                         return ns.GetSignatureForError ();
3241                 }
3242
3243                 public FullNamedExpression LookupTypeOrNamespace (IMemberContext ctx, string name, int arity, LookupMode mode, Location loc)
3244                 {
3245                         return ns.LookupTypeOrNamespace (ctx, name, arity, mode, loc);
3246                 }
3247
3248                 public override string ToString ()
3249                 {
3250                         return Namespace.Name;
3251                 }
3252     }
3253
3254         /// <summary>
3255         ///   This class denotes an expression which evaluates to a member
3256         ///   of a struct or a class.
3257         /// </summary>
3258         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
3259         {
3260                 protected bool conditional_access_receiver;
3261
3262                 //
3263                 // An instance expression associated with this member, if it's a
3264                 // non-static member
3265                 //
3266                 public Expression InstanceExpression;
3267
3268                 /// <summary>
3269                 ///   The name of this member.
3270                 /// </summary>
3271                 public abstract string Name {
3272                         get;
3273                 }
3274
3275                 //
3276                 // When base.member is used
3277                 //
3278                 public bool IsBase {
3279                         get { return InstanceExpression is BaseThis; }
3280                 }
3281
3282                 /// <summary>
3283                 ///   Whether this is an instance member.
3284                 /// </summary>
3285                 public abstract bool IsInstance {
3286                         get;
3287                 }
3288
3289                 /// <summary>
3290                 ///   Whether this is a static member.
3291                 /// </summary>
3292                 public abstract bool IsStatic {
3293                         get;
3294                 }
3295
3296                 public abstract string KindName {
3297                         get;
3298                 }
3299
3300                 public bool ConditionalAccess { get; set; }
3301
3302                 protected abstract TypeSpec DeclaringType {
3303                         get;
3304                 }
3305
3306                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
3307                         get {
3308                                 return InstanceExpression.Type;
3309                         }
3310                 }
3311
3312                 //
3313                 // Converts best base candidate for virtual method starting from QueriedBaseType
3314                 //
3315                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
3316                 {
3317                         //
3318                         // Only when base.member is used and method is virtual
3319                         //
3320                         if (!IsBase)
3321                                 return method;
3322
3323                         //
3324                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
3325                         // means for base.member access we have to find the closest match after we found best candidate
3326                         //
3327                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
3328                                 //
3329                                 // The method could already be what we are looking for
3330                                 //
3331                                 TypeSpec[] targs = null;
3332                                 if (method.DeclaringType != InstanceExpression.Type) {
3333                                         //
3334                                         // Candidate can have inflated MVAR parameters and we need to find
3335                                         // base match for original definition not inflated parameter types
3336                                         //
3337                                         var parameters = method.Parameters;
3338                                         if (method.Arity > 0) {
3339                                                 parameters = ((IParametersMember) method.MemberDefinition).Parameters;
3340                                                 var inflated = method.DeclaringType as InflatedTypeSpec;
3341                                                 if (inflated != null) {
3342                                                         parameters = parameters.Inflate (inflated.CreateLocalInflator (rc));
3343                                                 }
3344                                         }
3345
3346                                         var filter = new MemberFilter (method.Name, method.Arity, MemberKind.Method, parameters, null);
3347                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as MethodSpec;
3348                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
3349                                                 if (base_override.IsGeneric)
3350                                                         targs = method.TypeArguments;
3351
3352                                                 method = base_override;
3353                                         }
3354                                 }
3355
3356                                 //
3357                                 // When base access is used inside anonymous method/iterator/etc we need to
3358                                 // get back to the context of original type. We do it by emiting proxy
3359                                 // method in original class and rewriting base call to this compiler
3360                                 // generated method call which does the actual base invocation. This may
3361                                 // introduce redundant storey but with `this' only but it's tricky to avoid
3362                                 // at this stage as we don't know what expressions follow base
3363                                 //
3364                                 if (rc.CurrentAnonymousMethod != null) {
3365                                         if (targs == null && method.IsGeneric) {
3366                                                 targs = method.TypeArguments;
3367                                                 method = method.GetGenericMethodDefinition ();
3368                                         }
3369
3370                                         if (method.Parameters.HasArglist)
3371                                                 throw new NotImplementedException ("__arglist base call proxy");
3372
3373                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
3374
3375                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
3376                                         // get/set member expressions second call would fail to proxy because left expression
3377                                         // would be of 'this' and not 'base' because we share InstanceExpression for get/set
3378                                         // FIXME: The async check is another hack but will probably fail with mutators
3379                                         if (rc.CurrentType.IsStruct || rc.CurrentAnonymousMethod.Storey is AsyncTaskStorey)
3380                                                 InstanceExpression = new This (loc).Resolve (rc);
3381                                 }
3382
3383                                 if (targs != null)
3384                                         method = method.MakeGenericMethod (rc, targs);
3385                         }
3386
3387                         //
3388                         // Only base will allow this invocation to happen.
3389                         //
3390                         if (method.IsAbstract) {
3391                                 rc.Report.SymbolRelatedToPreviousError (method);
3392                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
3393                         }
3394
3395                         return method;
3396                 }
3397
3398                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3399                 {
3400                         if (InstanceExpression == null)
3401                                 return;
3402
3403                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
3404                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
3405                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
3406                                 }
3407                         }
3408                 }
3409
3410                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3411                 {
3412                         if (InstanceExpression == null)
3413                                 return true;
3414
3415                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
3416                 }
3417
3418                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
3419                 {
3420                         var ct = rc.CurrentType;
3421                         if (ct == qualifier)
3422                                 return true;
3423
3424                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
3425                                 return true;
3426
3427                         qualifier = qualifier.GetDefinition ();
3428                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
3429                                 return false;
3430                         }
3431
3432                         return true;
3433                 }
3434
3435                 public override bool ContainsEmitWithAwait ()
3436                 {
3437                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
3438                 }
3439
3440                 public override bool HasConditionalAccess ()
3441                 {
3442                         return ConditionalAccess || (InstanceExpression != null && InstanceExpression.HasConditionalAccess ());
3443                 }
3444
3445                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
3446                 {
3447                         do {
3448                                 type = type.GetDefinition ();
3449
3450                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
3451                                         return true;
3452
3453                                 type = type.DeclaringType;
3454                         } while (type != null);
3455
3456                         return false;
3457                 }
3458
3459                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
3460                 {
3461                         if (InstanceExpression != null) {
3462                                 InstanceExpression = InstanceExpression.Resolve (rc);
3463                                 CheckProtectedMemberAccess (rc, member);
3464                         }
3465
3466                         if (member.MemberType.IsPointer && !rc.IsUnsafe) {
3467                                 UnsafeError (rc, loc);
3468                         }
3469
3470                         var dep = member.GetMissingDependencies ();
3471                         if (dep != null) {
3472                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
3473                         }
3474
3475                         if (!rc.IsObsolete) {
3476                                 ObsoleteAttribute oa = member.GetAttributeObsolete ();
3477                                 if (oa != null)
3478                                         AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
3479                         }
3480
3481                         if (!(member is FieldSpec))
3482                                 member.MemberDefinition.SetIsUsed ();
3483                 }
3484
3485                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
3486                 {
3487                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
3488                 }
3489
3490                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
3491                 {
3492                         rc.Report.SymbolRelatedToPreviousError (member);
3493                         rc.Report.Error (1540, loc,
3494                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
3495                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3496                 }
3497
3498                 public override void FlowAnalysis (FlowAnalysisContext fc)
3499                 {
3500                         if (InstanceExpression != null) {
3501                                 InstanceExpression.FlowAnalysis (fc);
3502
3503                                 if (ConditionalAccess) {
3504                                         fc.BranchConditionalAccessDefiniteAssignment ();
3505                                 }
3506                         }
3507                 }
3508
3509                 protected void ResolveConditionalAccessReceiver (ResolveContext rc)
3510                 {
3511                         if (!rc.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
3512                                 if (HasConditionalAccess ()) {
3513                                         conditional_access_receiver = true;
3514                                         rc.Set (ResolveContext.Options.ConditionalAccessReceiver);
3515                                 }
3516                         }
3517                 }
3518
3519                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
3520                 {
3521                         if (!ResolveInstanceExpressionCore (rc, rhs))
3522                                 return false;
3523
3524                         //
3525                         // Check intermediate value modification which won't have any effect
3526                         //
3527                         if (rhs != null && TypeSpec.IsValueType (InstanceExpression.Type)) {
3528                                 var fexpr = InstanceExpression as FieldExpr;
3529                                 if (fexpr != null) {
3530                                         if (!fexpr.Spec.IsReadOnly || rc.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
3531                                                 return true;
3532
3533                                         if (fexpr.IsStatic) {
3534                                                 rc.Report.Error (1650, loc, "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
3535                                                         fexpr.GetSignatureForError ());
3536                                         } else {
3537                                                 rc.Report.Error (1648, loc, "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
3538                                                         fexpr.GetSignatureForError ());
3539                                         }
3540
3541                                         return true;
3542                                 }
3543
3544                                 if (InstanceExpression is PropertyExpr || InstanceExpression is IndexerExpr || InstanceExpression is Invocation) {
3545                                         if (rc.CurrentInitializerVariable != null) {
3546                                                 rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
3547                                                         InstanceExpression.Type.GetSignatureForError (), InstanceExpression.GetSignatureForError ());
3548                                         } else {
3549                                                 rc.Report.Error (1612, loc,
3550                                                         "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
3551                                                         InstanceExpression.GetSignatureForError ());
3552                                         }
3553
3554                                         return true;
3555                                 }
3556
3557                                 var lvr = InstanceExpression as LocalVariableReference;
3558                                 if (lvr != null) {
3559
3560                                         if (!lvr.local_info.IsReadonly)
3561                                                 return true;
3562
3563                                         rc.Report.Error (1654, loc, "Cannot assign to members of `{0}' because it is a `{1}'",
3564                                                 InstanceExpression.GetSignatureForError (), lvr.local_info.GetReadOnlyContext ());
3565                                 }
3566                         }
3567
3568                         return true;
3569                 }
3570
3571                 bool ResolveInstanceExpressionCore (ResolveContext rc, Expression rhs)
3572                 {
3573                         if (IsStatic) {
3574                                 if (InstanceExpression != null) {
3575                                         if (InstanceExpression is TypeExpr) {
3576                                                 var t = InstanceExpression.Type;
3577                                                 do {
3578                                                         ObsoleteAttribute oa = t.GetAttributeObsolete ();
3579                                                         if (oa != null && !rc.IsObsolete) {
3580                                                                 AttributeTester.Report_ObsoleteMessage (oa, t.GetSignatureForError (), loc, rc.Report);
3581                                                         }
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                                 ObsoleteAttribute oa = best_candidate.GetAttributeObsolete ();
5619                                 if (oa != null && !rc.IsObsolete)
5620                                         AttributeTester.Report_ObsoleteMessage (oa, best_candidate.GetSignatureForError (), loc, rc.Report);
5621
5622                                 best_candidate.MemberDefinition.SetIsUsed ();
5623                         }
5624
5625                         args = best_candidate_args;
5626                         return (T) best_candidate;
5627                 }
5628
5629                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
5630                 {
5631                         return ResolveMember<MethodSpec> (rc, ref args);
5632                 }
5633
5634                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
5635                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
5636                 {
5637                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
5638                                 return;
5639
5640                         if (a.Type == InternalType.ErrorType)
5641                                 return;
5642
5643                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
5644                                 ec.Report.SymbolRelatedToPreviousError (method);
5645                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
5646                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have `ref' or `out' modifier",
5647                                                 TypeManager.CSharpSignature (method));
5648                                         return;
5649                                 }
5650                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
5651                                           TypeManager.CSharpSignature (method));
5652                         } else if (IsDelegateInvoke) {
5653                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
5654                                         DelegateType.GetSignatureForError ());
5655                         } else {
5656                                 ec.Report.SymbolRelatedToPreviousError (method);
5657                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
5658                                         method.GetSignatureForError ());
5659                         }
5660
5661                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
5662
5663                         string index = (idx + 1).ToString ();
5664                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
5665                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
5666                                         ec.Report.Error (1615, a.Expr.Location, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
5667                                                 index, Parameter.GetModifierSignature (a.Modifier));
5668                                 else
5669                                         ec.Report.Error (1620, a.Expr.Location, "Argument `#{0}' is missing `{1}' modifier",
5670                                                 index, Parameter.GetModifierSignature (mod));
5671                         } else {
5672                                 string p1 = a.GetSignatureForError ();
5673                                 string p2 = paramType.GetSignatureForError ();
5674
5675                                 if (p1 == p2) {
5676                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
5677                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
5678                                 }
5679
5680                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
5681                                         p1 = Parameter.GetModifierSignature (a.Modifier) + " " + p1;
5682                                         p2 = Parameter.GetModifierSignature (a.Modifier) + " " + p2;
5683                                 }
5684
5685                                 ec.Report.Error (1503, a.Expr.Location,
5686                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
5687                         }
5688                 }
5689
5690                 //
5691                 // We have failed to find exact match so we return error info about the closest match
5692                 //
5693                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
5694                 {
5695                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
5696                         int arg_count = args == null ? 0 : args.Count;
5697
5698                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
5699                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
5700                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, loc);
5701                                 return;
5702                         }
5703
5704                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
5705                                 return;
5706                         }
5707
5708
5709                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5710                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
5711                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
5712                         }
5713
5714                         //
5715                         // For candidates which match on parameters count report more details about incorrect arguments
5716                         //
5717                         if (pm != null) {
5718                                 if (pm.Parameters.Count == arg_count || params_expanded || HasUnfilledParams (best_candidate, pm, args)) {
5719                                         // Reject any inaccessible member
5720                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
5721                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5722                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
5723                                                 return;
5724                                         }
5725
5726                                         var ms = best_candidate as MethodSpec;
5727                                         if (ms != null && ms.IsGeneric) {
5728                                                 bool constr_ok = true;
5729                                                 if (ms.TypeArguments != null)
5730                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
5731
5732                                                 if (ta_count == 0 && ms.TypeArguments == null) {
5733                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
5734                                                                 return;
5735
5736                                                         if (constr_ok) {
5737                                                                 rc.Report.Error (411, loc,
5738                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
5739                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
5740                                                         }
5741
5742                                                         return;
5743                                                 }
5744                                         }
5745
5746                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
5747                                         return;
5748                                 }
5749                         }
5750
5751                         //
5752                         // We failed to find any method with correct argument count, report best candidate
5753                         //
5754                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
5755                                 return;
5756
5757                         if (best_candidate.Kind == MemberKind.Constructor) {
5758                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5759                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
5760                         } else if (IsDelegateInvoke) {
5761                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
5762                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
5763                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
5764                         } else {
5765                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
5766                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5767                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
5768                                         name, arg_count.ToString ());
5769                         }
5770                 }
5771
5772                 static bool HasUnfilledParams (MemberSpec best_candidate, IParametersMember pm, Arguments args)
5773                 {
5774                         var p = ((IParametersMember)best_candidate).Parameters;
5775                         if (!p.HasParams)
5776                                 return false;
5777
5778                         string name = null;
5779                         for (int i = p.Count - 1; i != 0; --i) {
5780                                 var fp = p.FixedParameters [i];
5781                                 if ((fp.ModFlags & Parameter.Modifier.PARAMS) == 0)
5782                                         continue;
5783
5784                                 name = fp.Name;
5785                                 break;
5786                         }
5787
5788                         if (args == null)
5789                                 return false;
5790
5791                         foreach (var arg in args) {
5792                                 var na = arg as NamedArgument;
5793                                 if (na == null)
5794                                         continue;
5795
5796                                 if (na.Name == name) {
5797                                         name = null;
5798                                         break;
5799                                 }
5800                         }
5801
5802                         if (name == null)
5803                                 return false;
5804
5805                         return args.Count + 1 == pm.Parameters.Count;
5806                 }
5807
5808                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
5809                 {
5810                         var pd = pm.Parameters;
5811                         var cpd = ((IParametersMember) member).Parameters;
5812                         var ptypes = cpd.Types;
5813
5814                         Parameter.Modifier p_mod = 0;
5815                         TypeSpec pt = null;
5816                         int a_idx = 0, a_pos = 0;
5817                         Argument a = null;
5818                         ArrayInitializer params_initializers = null;
5819                         bool has_unsafe_arg = pm.MemberType.IsPointer;
5820                         int arg_count = args == null ? 0 : args.Count;
5821
5822                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
5823                                 a = args[a_idx];
5824                                 if (a == null)
5825                                         continue;
5826
5827                                 if (p_mod != Parameter.Modifier.PARAMS) {
5828                                         p_mod = cpd.FixedParameters [a_idx].ModFlags;
5829                                         pt = ptypes[a_idx];
5830                                         has_unsafe_arg |= pt.IsPointer;
5831
5832                                         if (p_mod == Parameter.Modifier.PARAMS) {
5833                                                 if (chose_params_expanded) {
5834                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
5835                                                         pt = TypeManager.GetElementType (pt);
5836                                                 }
5837                                         }
5838                                 }
5839
5840                                 //
5841                                 // Types have to be identical when ref or out modifer is used
5842                                 //
5843                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
5844                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
5845                                                 break;
5846
5847                                         var arg_type = a.Type;
5848                                         if (arg_type == pt)
5849                                                 continue;
5850
5851                                         if (arg_type == InternalType.VarOutType) {
5852                                                 //
5853                                                 // Set underlying variable type based on parameter type
5854                                                 //
5855                                                 ((DeclarationExpression)a.Expr).Variable.Type = pt;
5856                                                 continue;
5857                                         }
5858
5859                                         if (!TypeSpecComparer.IsEqual (arg_type, pt))
5860                                                 break;
5861                                 }
5862
5863                                 NamedArgument na = a as NamedArgument;
5864                                 if (na != null) {
5865                                         int name_index = pd.GetParameterIndexByName (na.Name);
5866                                         if (name_index < 0 || name_index >= pd.Count) {
5867                                                 if (IsDelegateInvoke) {
5868                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5869                                                         ec.Report.Error (1746, na.Location,
5870                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
5871                                                                 DelegateType.GetSignatureForError (), na.Name);
5872                                                 } else {
5873                                                         ec.Report.SymbolRelatedToPreviousError (member);
5874                                                         ec.Report.Error (1739, na.Location,
5875                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
5876                                                                 TypeManager.CSharpSignature (member), na.Name);
5877                                                 }
5878                                         } else if (args[name_index] != a && args[name_index] != null) {
5879                                                 if (IsDelegateInvoke)
5880                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5881                                                 else
5882                                                         ec.Report.SymbolRelatedToPreviousError (member);
5883
5884                                                 ec.Report.Error (1744, na.Location,
5885                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
5886                                                         na.Name);
5887                                         }
5888                                 }
5889
5890                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
5891                                         continue;
5892
5893                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
5894                                         if (a.IsExtensionType) {
5895                                                 // TODO: Should report better message type, something similar to CS1928/1929 instead of
5896                                                 // CS1061 but that still better than confusing CS0123
5897                                                 var ma = new MemberAccess (a.Expr, member.Name, loc);
5898                                                 ma.Error_TypeDoesNotContainDefinition (ec, a.Expr.Type, ma.Name);
5899                                         } else {
5900                                                 custom_errors.NoArgumentMatch (ec, member);
5901                                         }
5902                                         return false;
5903                                 }
5904
5905                                 Expression conv;
5906                                 if (a.IsExtensionType) {
5907                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
5908                                                 conv = a.Expr;
5909                                         } else {
5910                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
5911                                                 if (conv == null)
5912                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
5913                                         }
5914                                 } else {
5915                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
5916                                 }
5917
5918                                 if (conv == null)
5919                                         break;
5920
5921                                 //
5922                                 // Convert params arguments to an array initializer
5923                                 //
5924                                 if (params_initializers != null) {
5925                                         // we choose to use 'a.Expr' rather than 'conv' so that
5926                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
5927                                         params_initializers.Add (a.Expr);
5928                                         args.RemoveAt (a_idx--);
5929                                         --arg_count;
5930                                         a.Expr = conv;
5931                                         continue;
5932                                 }
5933
5934                                 // Update the argument with the implicit conversion
5935                                 a.Expr = conv;
5936                         }
5937
5938                         if (a_idx != arg_count) {
5939                                 //
5940                                 // Convert all var out argument to error type for less confusing error reporting
5941                                 // when no matching overload is found
5942                                 //
5943                                 for (; a_idx < arg_count; a_idx++) {
5944                                         var arg = args [a_idx];
5945                                         if (arg == null)
5946                                                 continue;
5947
5948                                         if (arg.Type == InternalType.VarOutType) {
5949                                                 ((DeclarationExpression)arg.Expr).Variable.Type = InternalType.ErrorType;
5950                                         }
5951                                 }
5952
5953                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
5954                                 return false;
5955                         }
5956
5957                         //
5958                         // Fill not provided arguments required by params modifier
5959                         //
5960                         if (params_initializers == null && arg_count + 1 == pd.Count) {
5961                                 if (args == null)
5962                                         args = new Arguments (1);
5963
5964                                 pt = ptypes[pd.Count - 1];
5965                                 pt = TypeManager.GetElementType (pt);
5966                                 has_unsafe_arg |= pt.IsPointer;
5967                                 params_initializers = new ArrayInitializer (0, loc);
5968                         }
5969
5970                         //
5971                         // Append an array argument with all params arguments
5972                         //
5973                         if (params_initializers != null) {
5974                                 args.Add (new Argument (
5975                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
5976                                 arg_count++;
5977                         }
5978
5979                         if (has_unsafe_arg && !ec.IsUnsafe) {
5980                                 Expression.UnsafeError (ec, loc);
5981                         }
5982
5983                         //
5984                         // We could infer inaccesible type arguments
5985                         //
5986                         if (type_arguments == null && member.IsGeneric) {
5987                                 var ms = (MethodSpec) member;
5988                                 foreach (var ta in ms.TypeArguments) {
5989                                         if (!ta.IsAccessible (ec)) {
5990                                                 ec.Report.SymbolRelatedToPreviousError (ta);
5991                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
5992                                                 break;
5993                                         }
5994                                 }
5995                         }
5996
5997                         return true;
5998                 }
5999         }
6000
6001         public class ConstantExpr : MemberExpr
6002         {
6003                 readonly ConstSpec constant;
6004
6005                 public ConstantExpr (ConstSpec constant, Location loc)
6006                 {
6007                         this.constant = constant;
6008                         this.loc = loc;
6009                 }
6010
6011                 public override string Name {
6012                         get { throw new NotImplementedException (); }
6013                 }
6014
6015                 public override string KindName {
6016                         get { return "constant"; }
6017                 }
6018
6019                 public override bool IsInstance {
6020                         get { return !IsStatic; }
6021                 }
6022
6023                 public override bool IsStatic {
6024                         get { return true; }
6025                 }
6026
6027                 protected override TypeSpec DeclaringType {
6028                         get { return constant.DeclaringType; }
6029                 }
6030
6031                 public override Expression CreateExpressionTree (ResolveContext ec)
6032                 {
6033                         throw new NotSupportedException ("ET");
6034                 }
6035
6036                 protected override Expression DoResolve (ResolveContext rc)
6037                 {
6038                         ResolveInstanceExpression (rc, null);
6039                         DoBestMemberChecks (rc, constant);
6040
6041                         var c = constant.GetConstant (rc);
6042
6043                         // Creates reference expression to the constant value
6044                         return Constant.CreateConstantFromValue (constant.MemberType, c.GetValue (), loc);
6045                 }
6046
6047                 public override void Emit (EmitContext ec)
6048                 {
6049                         throw new NotSupportedException ();
6050                 }
6051
6052                 public override string GetSignatureForError ()
6053                 {
6054                         return constant.GetSignatureForError ();
6055                 }
6056
6057                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6058                 {
6059                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
6060                 }
6061         }
6062
6063         //
6064         // Fully resolved expression that references a Field
6065         //
6066         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
6067         {
6068                 protected FieldSpec spec;
6069                 VariableInfo variable_info;
6070
6071                 LocalTemporary temp;
6072                 bool prepared;
6073
6074                 protected FieldExpr (Location l)
6075                 {
6076                         loc = l;
6077                 }
6078
6079                 public FieldExpr (FieldSpec spec, Location loc)
6080                 {
6081                         this.spec = spec;
6082                         this.loc = loc;
6083
6084                         type = spec.MemberType;
6085                 }
6086
6087                 public FieldExpr (FieldBase fi, Location l)
6088                         : this (fi.Spec, l)
6089                 {
6090                 }
6091
6092                 #region Properties
6093
6094                 public override string Name {
6095                         get {
6096                                 return spec.Name;
6097                         }
6098                 }
6099
6100                 public bool IsHoisted {
6101                         get {
6102                                 IVariableReference hv = InstanceExpression as IVariableReference;
6103                                 return hv != null && hv.IsHoisted;
6104                         }
6105                 }
6106
6107                 public override bool IsInstance {
6108                         get {
6109                                 return !spec.IsStatic;
6110                         }
6111                 }
6112
6113                 public override bool IsStatic {
6114                         get {
6115                                 return spec.IsStatic;
6116                         }
6117                 }
6118
6119                 public override string KindName {
6120                         get { return "field"; }
6121                 }
6122
6123                 public FieldSpec Spec {
6124                         get {
6125                                 return spec;
6126                         }
6127                 }
6128
6129                 protected override TypeSpec DeclaringType {
6130                         get {
6131                                 return spec.DeclaringType;
6132                         }
6133                 }
6134
6135                 public VariableInfo VariableInfo {
6136                         get {
6137                                 return variable_info;
6138                         }
6139                 }
6140
6141 #endregion
6142
6143                 public override string GetSignatureForError ()
6144                 {
6145                         return spec.GetSignatureForError ();
6146                 }
6147
6148                 public bool IsMarshalByRefAccess (ResolveContext rc)
6149                 {
6150                         // Checks possible ldflda of field access expression
6151                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
6152                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
6153                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
6154                 }
6155
6156                 public void SetHasAddressTaken ()
6157                 {
6158                         IVariableReference vr = InstanceExpression as IVariableReference;
6159                         if (vr != null) {
6160                                 vr.SetHasAddressTaken ();
6161                         }
6162                 }
6163
6164                 protected override void CloneTo (CloneContext clonectx, Expression target)
6165                 {
6166                         var t = (FieldExpr) target;
6167
6168                         if (InstanceExpression != null)
6169                                 t.InstanceExpression = InstanceExpression.Clone (clonectx);
6170                 }
6171
6172                 public override Expression CreateExpressionTree (ResolveContext ec)
6173                 {
6174                         if (ConditionalAccess) {
6175                                 Error_NullShortCircuitInsideExpressionTree (ec);
6176                         }
6177
6178                         return CreateExpressionTree (ec, true);
6179                 }
6180
6181                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
6182                 {
6183                         Arguments args;
6184                         Expression instance;
6185
6186                         if (InstanceExpression == null) {
6187                                 instance = new NullLiteral (loc);
6188                         } else if (convertInstance) {
6189                                 instance = InstanceExpression.CreateExpressionTree (ec);
6190                         } else {
6191                                 args = new Arguments (1);
6192                                 args.Add (new Argument (InstanceExpression));
6193                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
6194                         }
6195
6196                         args = Arguments.CreateForExpressionTree (ec, null,
6197                                 instance,
6198                                 CreateTypeOfExpression ());
6199
6200                         return CreateExpressionFactoryCall (ec, "Field", args);
6201                 }
6202
6203                 public Expression CreateTypeOfExpression ()
6204                 {
6205                         return new TypeOfField (spec, loc);
6206                 }
6207
6208                 protected override Expression DoResolve (ResolveContext ec)
6209                 {
6210                         spec.MemberDefinition.SetIsUsed ();
6211
6212                         return DoResolve (ec, null);
6213                 }
6214
6215                 Expression DoResolve (ResolveContext ec, Expression rhs)
6216                 {
6217                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
6218
6219                         if (rhs != this) {
6220                                 ResolveConditionalAccessReceiver (ec);
6221
6222                                 if (ResolveInstanceExpression (ec, rhs)) {
6223                                         // Resolve the field's instance expression while flow analysis is turned
6224                                         // off: when accessing a field "a.b", we must check whether the field
6225                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
6226
6227                                         if (lvalue_instance) {
6228                                                 bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
6229
6230                                                 Expression right_side =
6231                                                         out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
6232
6233                                                 InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
6234                                         } else {
6235                                                 InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
6236                                         }
6237
6238                                         if (InstanceExpression == null)
6239                                                 return null;
6240                                 }
6241
6242                                 DoBestMemberChecks (ec, spec);
6243
6244                                 if (conditional_access_receiver)
6245                                         ec.With (ResolveContext.Options.ConditionalAccessReceiver, false);
6246                         }
6247
6248                         var fb = spec as FixedFieldSpec;
6249                         IVariableReference var = InstanceExpression as IVariableReference;
6250
6251                         if (fb != null) {
6252                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6253                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
6254                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
6255                                 }
6256
6257                                 if (InstanceExpression.eclass != ExprClass.Variable) {
6258                                         ec.Report.SymbolRelatedToPreviousError (spec);
6259                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
6260                                                 TypeManager.GetFullNameSignature (spec));
6261                                 } else if (var != null && var.IsHoisted) {
6262                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
6263                                 }
6264
6265                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
6266                         }
6267
6268                         //
6269                         // Set flow-analysis variable info for struct member access. It will be check later
6270                         // for precise error reporting
6271                         //
6272                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
6273                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
6274                         }
6275
6276                         if (ConditionalAccess) {
6277                                 if (conditional_access_receiver)
6278                                         type = LiftMemberType (ec, type);
6279
6280                                 if (InstanceExpression.IsNull)
6281                                         return Constant.CreateConstantFromValue (type, null, loc);
6282                         }
6283
6284                         eclass = ExprClass.Variable;
6285                         return this;
6286                 }
6287
6288                 public void SetFieldAssigned (FlowAnalysisContext fc)
6289                 {
6290                         if (!IsInstance)
6291                                 return;
6292
6293                         bool lvalue_instance = spec.DeclaringType.IsStruct;
6294                         if (lvalue_instance) {
6295                                 var var = InstanceExpression as IVariableReference;
6296                                 if (var != null && var.VariableInfo != null) {
6297                                         fc.SetStructFieldAssigned (var.VariableInfo, Name);
6298                                 }
6299                         }
6300
6301                         var fe = InstanceExpression as FieldExpr;
6302                         if (fe != null) {
6303                                 Expression instance;
6304
6305                                 do {
6306                                         instance = fe.InstanceExpression;
6307                                         var fe_instance = instance as FieldExpr;
6308                                         if ((fe_instance != null && !fe_instance.IsStatic) || instance is LocalVariableReference) {
6309                                                 if (TypeSpec.IsReferenceType (fe.Type) && instance.Type.IsStruct) {
6310                                                         var var = InstanceExpression as IVariableReference;
6311                                                         if (var != null && var.VariableInfo == null) {
6312                                                                 var var_inst = instance as IVariableReference;
6313                                                                 if (var_inst == null || (var_inst.VariableInfo != null && !fc.IsDefinitelyAssigned (var_inst.VariableInfo)))
6314                                                                         fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
6315                                                         }
6316                                                 }
6317
6318                                                 if (fe_instance != null) {
6319                                                         fe = fe_instance;
6320                                                         continue;
6321                                                 }
6322                                         }
6323
6324                                         break;
6325                                 } while (true);
6326
6327                                 if (instance != null && TypeSpec.IsReferenceType (instance.Type))
6328                                         instance.FlowAnalysis (fc);
6329                         } else {
6330                                 if (TypeSpec.IsReferenceType (InstanceExpression.Type))
6331                                         InstanceExpression.FlowAnalysis (fc);
6332                         }
6333                 }
6334
6335                 Expression Error_AssignToReadonly (ResolveContext rc, Expression right_side)
6336                 {
6337                         // The return value is always null.  Returning a value simplifies calling code.
6338
6339                         if (right_side == EmptyExpression.OutAccess) {
6340                                 if (IsStatic) {
6341                                         rc.Report.Error (199, loc, "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6342                                                 GetSignatureForError ());
6343                                 } else {
6344                                         rc.Report.Error (192, loc, "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6345                                                 GetSignatureForError ());
6346                                 }
6347
6348                                 return null;
6349                         }
6350
6351                         if (right_side == EmptyExpression.LValueMemberAccess) {
6352                                 // Already reported as CS1648/CS1650
6353                                 return null;
6354                         }
6355
6356                         if (right_side == EmptyExpression.LValueMemberOutAccess) {
6357                                 if (IsStatic) {
6358                                         rc.Report.Error (1651, loc, "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
6359                                                 GetSignatureForError ());
6360                                 } else {
6361                                         rc.Report.Error (1649, loc, "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
6362                                                 GetSignatureForError ());
6363                                 }
6364                                 return null;
6365                         }
6366
6367                         if (IsStatic) {
6368                                 rc.Report.Error (198, loc, "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
6369                                         GetSignatureForError ());
6370                         } else {
6371                                 rc.Report.Error (191, loc, "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
6372                                         GetSignatureForError ());
6373                         }
6374
6375                         return null;
6376                 }
6377
6378                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6379                 {
6380                         if (ConditionalAccess)
6381                                 Error_NullPropagatingLValue (ec);
6382
6383                         if (spec is FixedFieldSpec) {
6384                                 // It could be much better error message but we want to be error compatible
6385                                 Error_ValueAssignment (ec, right_side);
6386                         }
6387
6388                         Expression e = DoResolve (ec, right_side);
6389
6390                         if (e == null)
6391                                 return null;
6392
6393                         spec.MemberDefinition.SetIsAssigned ();
6394
6395                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
6396                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
6397                                 ec.Report.Warning (420, 1, loc,
6398                                         "`{0}': A volatile field references will not be treated as volatile",
6399                                         spec.GetSignatureForError ());
6400                         }
6401
6402                         if (spec.IsReadOnly) {
6403                                 // InitOnly fields can only be assigned in constructors or initializers
6404                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
6405                                         return Error_AssignToReadonly (ec, right_side);
6406
6407                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
6408
6409                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
6410                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
6411                                                 return Error_AssignToReadonly (ec, right_side);
6412                                         // static InitOnly fields cannot be assigned-to in an instance constructor
6413                                         if (IsStatic && !ec.IsStatic)
6414                                                 return Error_AssignToReadonly (ec, right_side);
6415                                         // instance constructors can't modify InitOnly fields of other instances of the same type
6416                                         if (!IsStatic && !(InstanceExpression is This))
6417                                                 return Error_AssignToReadonly (ec, right_side);
6418                                 }
6419                         }
6420
6421                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
6422                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
6423                                 ec.Report.Warning (197, 1, loc,
6424                                                 "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",
6425                                                 GetSignatureForError ());
6426                         }
6427
6428                         eclass = ExprClass.Variable;
6429                         return this;
6430                 }
6431
6432                 public override void FlowAnalysis (FlowAnalysisContext fc)
6433                 {
6434                         var var = InstanceExpression as IVariableReference;
6435                         if (var != null) {
6436                                 var vi = var.VariableInfo;
6437                                 if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, Name)) {
6438                                         fc.Report.Error (170, loc, "Use of possibly unassigned field `{0}'", Name);
6439                                         return;
6440                                 }
6441
6442                                 if (TypeSpec.IsValueType (InstanceExpression.Type) && InstanceExpression is VariableReference)
6443                                         return;
6444                         }
6445
6446                         base.FlowAnalysis (fc);
6447
6448                         if (conditional_access_receiver)
6449                                 fc.ConditionalAccessEnd ();
6450                 }
6451
6452                 public override int GetHashCode ()
6453                 {
6454                         return spec.GetHashCode ();
6455                 }
6456
6457                 public bool IsFixed {
6458                         get {
6459                                 //
6460                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
6461                                 //
6462                                 IVariableReference variable = InstanceExpression as IVariableReference;
6463                                 if (variable != null)
6464                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
6465
6466                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
6467                                 return fe != null && fe.IsFixed;
6468                         }
6469                 }
6470
6471                 public override bool Equals (object obj)
6472                 {
6473                         FieldExpr fe = obj as FieldExpr;
6474                         if (fe == null)
6475                                 return false;
6476
6477                         if (spec != fe.spec)
6478                                 return false;
6479
6480                         if (InstanceExpression == null || fe.InstanceExpression == null)
6481                                 return true;
6482
6483                         return InstanceExpression.Equals (fe.InstanceExpression);
6484                 }
6485
6486                 public void Emit (EmitContext ec, bool leave_copy)
6487                 {
6488                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6489
6490                         if (IsStatic){
6491                                 if (is_volatile)
6492                                         ec.Emit (OpCodes.Volatile);
6493
6494                                 ec.Emit (OpCodes.Ldsfld, spec);
6495                         } else {
6496                                 if (!prepared) {
6497                                         if (conditional_access_receiver)
6498                                                 ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
6499
6500                                         EmitInstance (ec, false);
6501                                 }
6502
6503                                 // Optimization for build-in types
6504                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
6505                                         ec.EmitLoadFromPtr (type);
6506                                 } else {
6507                                         var ff = spec as FixedFieldSpec;
6508                                         if (ff != null) {
6509                                                 ec.Emit (OpCodes.Ldflda, spec);
6510                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
6511                                         } else {
6512                                                 if (is_volatile)
6513                                                         ec.Emit (OpCodes.Volatile);
6514
6515                                                 ec.Emit (OpCodes.Ldfld, spec);
6516                                         }
6517                                 }
6518
6519                                 if (conditional_access_receiver) {
6520                                         ec.CloseConditionalAccess (type.IsNullableType && type != spec.MemberType ? type : null);
6521                                 }
6522                         }
6523
6524                         if (leave_copy) {
6525                                 ec.Emit (OpCodes.Dup);
6526                                 if (!IsStatic) {
6527                                         temp = new LocalTemporary (this.Type);
6528                                         temp.Store (ec);
6529                                 }
6530                         }
6531                 }
6532
6533                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6534                 {
6535                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
6536                         if (isCompound && !(source is DynamicExpressionStatement) && !has_await_source) {
6537                                 prepared = true;
6538                         }
6539
6540                         if (IsInstance) {
6541                                 if (ConditionalAccess)
6542                                         throw new NotImplementedException ("null operator assignment");
6543
6544                                 if (has_await_source)
6545                                         source = source.EmitToField (ec);
6546
6547                                 EmitInstance (ec, prepared);
6548                         }
6549
6550                         source.Emit (ec);
6551
6552                         if (leave_copy || ec.NotifyEvaluatorOnStore) {
6553                                 ec.Emit (OpCodes.Dup);
6554                                 if (!IsStatic) {
6555                                         temp = new LocalTemporary (this.Type);
6556                                         temp.Store (ec);
6557                                 }
6558                         }
6559
6560                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
6561                                 ec.Emit (OpCodes.Volatile);
6562
6563                         spec.MemberDefinition.SetIsAssigned ();
6564
6565                         if (IsStatic)
6566                                 ec.Emit (OpCodes.Stsfld, spec);
6567                         else
6568                                 ec.Emit (OpCodes.Stfld, spec);
6569
6570                         if (ec.NotifyEvaluatorOnStore) {
6571                                 if (!IsStatic)
6572                                         throw new NotImplementedException ("instance field write");
6573
6574                                 if (leave_copy)
6575                                         ec.Emit (OpCodes.Dup);
6576
6577                                 ec.Module.Evaluator.EmitValueChangedCallback (ec, Name, type, loc);
6578                         }
6579
6580                         if (temp != null) {
6581                                 temp.Emit (ec);
6582                                 temp.Release (ec);
6583                                 temp = null;
6584                         }
6585                 }
6586
6587                 //
6588                 // Emits store to field with prepared values on stack
6589                 //
6590                 public void EmitAssignFromStack (EmitContext ec)
6591                 {
6592                         if (IsStatic) {
6593                                 ec.Emit (OpCodes.Stsfld, spec);
6594                         } else {
6595                                 ec.Emit (OpCodes.Stfld, spec);
6596                         }
6597                 }
6598
6599                 public override void Emit (EmitContext ec)
6600                 {
6601                         Emit (ec, false);
6602                 }
6603
6604                 public override void EmitSideEffect (EmitContext ec)
6605                 {
6606                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6607
6608                         if (is_volatile) // || is_marshal_by_ref ())
6609                                 base.EmitSideEffect (ec);
6610                 }
6611
6612                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
6613                 {
6614                         if ((mode & AddressOp.Store) != 0)
6615                                 spec.MemberDefinition.SetIsAssigned ();
6616                         if ((mode & AddressOp.Load) != 0)
6617                                 spec.MemberDefinition.SetIsUsed ();
6618
6619                         //
6620                         // Handle initonly fields specially: make a copy and then
6621                         // get the address of the copy.
6622                         //
6623                         bool need_copy;
6624                         if (spec.IsReadOnly){
6625                                 need_copy = true;
6626                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
6627                                         if (IsStatic){
6628                                                 if (ec.IsStatic)
6629                                                         need_copy = false;
6630                                         } else
6631                                                 need_copy = false;
6632                                 }
6633                         } else
6634                                 need_copy = false;
6635
6636                         if (need_copy) {
6637                                 Emit (ec);
6638                                 var temp = ec.GetTemporaryLocal (type);
6639                                 ec.Emit (OpCodes.Stloc, temp);
6640                                 ec.Emit (OpCodes.Ldloca, temp);
6641                                 return;
6642                         }
6643
6644
6645                         if (IsStatic){
6646                                 ec.Emit (OpCodes.Ldsflda, spec);
6647                         } else {
6648                                 if (!prepared)
6649                                         EmitInstance (ec, false);
6650                                 ec.Emit (OpCodes.Ldflda, spec);
6651                         }
6652                 }
6653
6654                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6655                 {
6656                         return MakeExpression (ctx);
6657                 }
6658
6659                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6660                 {
6661 #if STATIC
6662                         return base.MakeExpression (ctx);
6663 #else
6664                         return SLE.Expression.Field (
6665                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
6666                                 spec.GetMetaInfo ());
6667 #endif
6668                 }
6669
6670                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6671                 {
6672                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
6673                 }
6674         }
6675
6676
6677         //
6678         // Expression that evaluates to a Property.
6679         //
6680         // This is not an LValue because we need to re-write the expression. We
6681         // can not take data from the stack and store it.
6682         //
6683         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
6684         {
6685                 Arguments arguments;
6686                 FieldExpr backing_field;
6687
6688                 public PropertyExpr (PropertySpec spec, Location l)
6689                         : base (l)
6690                 {
6691                         best_candidate = spec;
6692                         type = spec.MemberType;
6693                 }
6694
6695                 #region Properties
6696
6697                 protected override Arguments Arguments {
6698                         get {
6699                                 return arguments;
6700                         }
6701                         set {
6702                                 arguments = value;
6703                         }
6704                 }
6705
6706                 protected override TypeSpec DeclaringType {
6707                         get {
6708                                 return best_candidate.DeclaringType;
6709                         }
6710                 }
6711
6712                 public override string Name {
6713                         get {
6714                                 return best_candidate.Name;
6715                         }
6716                 }
6717
6718                 public bool IsAutoPropertyAccess {
6719                         get {
6720                                 var prop = best_candidate.MemberDefinition as Property;
6721                                 return prop != null && prop.BackingField != null;
6722                         }
6723                 }
6724
6725                 public override bool IsInstance {
6726                         get {
6727                                 return !IsStatic;
6728                         }
6729                 }
6730
6731                 public override bool IsStatic {
6732                         get {
6733                                 return best_candidate.IsStatic;
6734                         }
6735                 }
6736
6737                 public override string KindName {
6738                         get { return "property"; }
6739                 }
6740
6741                 public PropertySpec PropertyInfo {
6742                         get {
6743                                 return best_candidate;
6744                         }
6745                 }
6746
6747                 #endregion
6748
6749                 public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
6750                 {
6751                         if (best_candidate == null || !(best_candidate.IsStatic || InstanceExpression is This))
6752                                 return null;
6753
6754                         var args_count = arguments == null ? 0 : arguments.Count;
6755                         if (args_count != body.Parameters.Count && args_count == 0)
6756                                 return null;
6757
6758                         var mg = MethodGroupExpr.CreatePredefined (best_candidate.Get, DeclaringType, loc);
6759                         mg.InstanceExpression = InstanceExpression;
6760
6761                         return mg;
6762                 }
6763
6764                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
6765                 {
6766                         return new PropertyExpr (spec, loc) {
6767                                 Getter = spec.Get,
6768                                 Setter = spec.Set
6769                         };
6770                 }
6771
6772                 public override Expression CreateExpressionTree (ResolveContext ec)
6773                 {
6774                         if (ConditionalAccess) {
6775                                 Error_NullShortCircuitInsideExpressionTree (ec);
6776                         }
6777
6778                         Arguments args;
6779                         if (IsSingleDimensionalArrayLength ()) {
6780                                 args = new Arguments (1);
6781                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6782                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
6783                         }
6784
6785                         args = new Arguments (2);
6786                         if (InstanceExpression == null)
6787                                 args.Add (new Argument (new NullLiteral (loc)));
6788                         else
6789                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6790                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
6791                         return CreateExpressionFactoryCall (ec, "Property", args);
6792                 }
6793
6794                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
6795                 {
6796                         DoResolveLValue (rc, null);
6797                         return new TypeOfMethod (Setter, loc);
6798                 }
6799
6800                 public override string GetSignatureForError ()
6801                 {
6802                         return best_candidate.GetSignatureForError ();
6803                 }
6804
6805                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6806                 {
6807 #if STATIC
6808                         return base.MakeExpression (ctx);
6809 #else
6810                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
6811 #endif
6812                 }
6813
6814                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6815                 {
6816 #if STATIC
6817                         return base.MakeExpression (ctx);
6818 #else
6819                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
6820 #endif
6821                 }
6822
6823                 void Error_PropertyNotValid (ResolveContext ec)
6824                 {
6825                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
6826                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
6827                                 GetSignatureForError ());
6828                 }
6829
6830                 bool IsSingleDimensionalArrayLength ()
6831                 {
6832                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
6833                                 return false;
6834
6835                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
6836                         return ac != null && ac.Rank == 1;
6837                 }
6838
6839                 public override void Emit (EmitContext ec, bool leave_copy)
6840                 {
6841                         //
6842                         // Special case: length of single dimension array property is turned into ldlen
6843                         //
6844                         if (IsSingleDimensionalArrayLength ()) {
6845                                 if (conditional_access_receiver) {
6846                                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
6847                                 }
6848
6849                                 EmitInstance (ec, false);
6850
6851                                 ec.Emit (OpCodes.Ldlen);
6852                                 ec.Emit (OpCodes.Conv_I4);
6853
6854                                 if (conditional_access_receiver) {
6855                                         ec.CloseConditionalAccess (type);
6856                                 }
6857
6858                                 return;
6859                         }
6860
6861                         base.Emit (ec, leave_copy);
6862                 }
6863
6864                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6865                 {
6866                         if (backing_field != null) {
6867                                 backing_field.EmitAssign (ec, source, false, false);
6868                                 return;
6869                         }
6870
6871                         Arguments args;
6872                         LocalTemporary await_source_arg = null;
6873
6874                         if (isCompound && !(source is DynamicExpressionStatement)) {
6875                                 emitting_compound_assignment = true;
6876                                 source.Emit (ec);
6877
6878                                 if (has_await_arguments) {
6879                                         await_source_arg = new LocalTemporary (Type);
6880                                         await_source_arg.Store (ec);
6881
6882                                         args = new Arguments (1);
6883                                         args.Add (new Argument (await_source_arg));
6884
6885                                         if (leave_copy) {
6886                                                 temp = await_source_arg;
6887                                         }
6888
6889                                         has_await_arguments = false;
6890                                 } else {
6891                                         args = null;
6892
6893                                         if (leave_copy) {
6894                                                 ec.Emit (OpCodes.Dup);
6895                                                 temp = new LocalTemporary (this.Type);
6896                                                 temp.Store (ec);
6897                                         }
6898                                 }
6899                         } else {
6900                                 args = arguments ?? new Arguments (1);
6901
6902                                 if (leave_copy) {
6903                                         source.Emit (ec);
6904                                         temp = new LocalTemporary (this.Type);
6905                                         temp.Store (ec);
6906                                         args.Add (new Argument (temp));
6907                                 } else {
6908                                         args.Add (new Argument (source));
6909                                 }
6910                         }
6911
6912                         emitting_compound_assignment = false;
6913
6914                         var call = new CallEmitter ();
6915                         call.InstanceExpression = InstanceExpression;
6916                         if (args == null)
6917                                 call.InstanceExpressionOnStack = true;
6918
6919                         if (ConditionalAccess) {
6920                                 call.ConditionalAccess = true;
6921                         }
6922
6923                         if (leave_copy)
6924                                 call.Emit (ec, Setter, args, loc);
6925                         else
6926                                 call.EmitStatement (ec, Setter, args, loc);
6927
6928                         if (temp != null) {
6929                                 temp.Emit (ec);
6930                                 temp.Release (ec);
6931                         }
6932
6933                         if (await_source_arg != null) {
6934                                 await_source_arg.Release (ec);
6935                         }
6936                 }
6937
6938                 public override void FlowAnalysis (FlowAnalysisContext fc)
6939                 {
6940                         var prop = best_candidate.MemberDefinition as Property;
6941                         if (prop != null && prop.BackingField != null) {
6942                                 var var = InstanceExpression as IVariableReference;
6943                                 if (var != null) {
6944                                         var vi = var.VariableInfo;
6945                                         if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, prop.BackingField.Name)) {
6946                                                 fc.Report.Error (8079, loc, "Use of possibly unassigned auto-implemented property `{0}'", Name);
6947                                                 return;
6948                                         }
6949
6950                                         if (TypeSpec.IsValueType (InstanceExpression.Type) && InstanceExpression is VariableReference)
6951                                                 return;
6952                                 }
6953                         }
6954
6955                         base.FlowAnalysis (fc);
6956
6957                         if (conditional_access_receiver)
6958                                 fc.ConditionalAccessEnd ();
6959                 }
6960
6961                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
6962                 {
6963                         eclass = ExprClass.PropertyAccess;
6964
6965                         if (best_candidate.IsNotCSharpCompatible) {
6966                                 Error_PropertyNotValid (rc);
6967                         }
6968
6969                         ResolveInstanceExpression (rc, right_side);
6970
6971                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
6972                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
6973                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
6974                                 if (p != null) {
6975                                         type = p.MemberType;
6976                                 }
6977                         }
6978
6979                         DoBestMemberChecks (rc, best_candidate);
6980
6981                         // Handling of com-imported properties with any number of default property parameters
6982                         if (best_candidate.HasGet && !best_candidate.Get.Parameters.IsEmpty) {
6983                                 var p = best_candidate.Get.Parameters;
6984                                 arguments = new Arguments (p.Count);
6985                                 for (int i = 0; i < p.Count; ++i) {
6986                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6987                                 }
6988                         } else if (best_candidate.HasSet && best_candidate.Set.Parameters.Count > 1) {
6989                                 var p = best_candidate.Set.Parameters;
6990                                 arguments = new Arguments (p.Count - 1);
6991                                 for (int i = 0; i < p.Count - 1; ++i) {
6992                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6993                                 }
6994                         }
6995
6996                         return this;
6997                 }
6998
6999                 protected override bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7000                 {
7001                         var prop = best_candidate.MemberDefinition as Property;
7002                         if (prop == null)
7003                                 return false;
7004
7005                         if (!rc.HasSet (ResolveContext.Options.ConstructorScope))
7006                                 return false;
7007
7008                         var spec = prop.BackingField;
7009                         if (spec == null)
7010                                 return false;
7011
7012                         if (rc.IsStatic != spec.IsStatic)
7013                                 return false;
7014
7015                         if (!spec.IsStatic && (!(InstanceExpression is This) || InstanceExpression is BaseThis))
7016                                 return false;
7017
7018                         backing_field = new FieldExpr (prop.BackingField, loc);
7019                         backing_field.ResolveLValue (rc, rhs);
7020                         return true;
7021                 }
7022
7023                 public void SetBackingFieldAssigned (FlowAnalysisContext fc)
7024                 {
7025                         if (backing_field != null) {
7026                                 backing_field.SetFieldAssigned (fc);
7027                                 return;
7028                         }
7029
7030                         if (!IsAutoPropertyAccess)
7031                                 return;
7032
7033                         var prop = best_candidate.MemberDefinition as Property;
7034                         if (prop != null && prop.BackingField != null) {
7035                                 bool lvalue_instance = best_candidate.DeclaringType.IsStruct;
7036                                 if (lvalue_instance) {
7037                                         var var = InstanceExpression as IVariableReference;
7038                                         if (var != null && var.VariableInfo != null) {
7039                                                 fc.SetStructFieldAssigned (var.VariableInfo, prop.BackingField.Name);
7040                                         }
7041                                 }
7042                         }
7043                 }
7044
7045                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7046                 {
7047                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
7048                 }
7049         }
7050
7051         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
7052         {
7053                 // getter and setter can be different for base calls
7054                 MethodSpec getter, setter;
7055                 protected T best_candidate;
7056
7057                 protected LocalTemporary temp;
7058                 protected bool emitting_compound_assignment;
7059                 protected bool has_await_arguments;
7060
7061                 protected PropertyOrIndexerExpr (Location l)
7062                 {
7063                         loc = l;
7064                 }
7065
7066                 #region Properties
7067
7068                 protected abstract Arguments Arguments { get; set; }
7069
7070                 public MethodSpec Getter {
7071                         get {
7072                                 return getter;
7073                         }
7074                         set {
7075                                 getter = value;
7076                         }
7077                 }
7078
7079                 public MethodSpec Setter {
7080                         get {
7081                                 return setter;
7082                         }
7083                         set {
7084                                 setter = value;
7085                         }
7086                 }
7087
7088                 #endregion
7089
7090                 protected override Expression DoResolve (ResolveContext ec)
7091                 {
7092                         if (eclass == ExprClass.Unresolved) {
7093                                 ResolveConditionalAccessReceiver (ec);
7094
7095                                 var expr = OverloadResolve (ec, null);
7096                                 if (expr == null)
7097                                         return null;
7098
7099                                 if (expr != this)
7100                                         return expr.Resolve (ec);
7101
7102                                 if (conditional_access_receiver) {
7103                                         type = LiftMemberType (ec, type);
7104                                         ec.With (ResolveContext.Options.ConditionalAccessReceiver, false);
7105                                 }
7106                         }
7107
7108                         if (!ResolveGetter (ec))
7109                                 return null;
7110
7111                         return this;
7112                 }
7113
7114                 public override Expression DoResolveLValue (ResolveContext rc, Expression right_side)
7115                 {
7116                         if (ConditionalAccess)
7117                                 Error_NullPropagatingLValue (rc);
7118
7119                         if (right_side == EmptyExpression.OutAccess) {
7120                                 // TODO: best_candidate can be null at this point
7121                                 INamedBlockVariable variable = null;
7122                                 if (best_candidate != null && rc.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, rc.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
7123                                         rc.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
7124                                                 best_candidate.Name);
7125                                 } else {
7126                                         right_side.DoResolveLValue (rc, this);
7127                                 }
7128                                 return null;
7129                         }
7130
7131                         if (eclass == ExprClass.Unresolved) {
7132                                 var expr = OverloadResolve (rc, right_side);
7133                                 if (expr == null)
7134                                         return null;
7135
7136                                 if (expr != this)
7137                                         return expr.ResolveLValue (rc, right_side);
7138                         } else {
7139                                 ResolveInstanceExpression (rc, right_side);
7140                         }
7141
7142                         if (!best_candidate.HasSet) {
7143                                 if (ResolveAutopropertyAssignment (rc, right_side))
7144                                         return this;
7145
7146                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
7147                                         GetSignatureForError ());
7148                                 return null;
7149                         }
7150
7151                         if (!best_candidate.Set.IsAccessible (rc) || !best_candidate.Set.DeclaringType.IsAccessible (rc)) {
7152                                 if (best_candidate.HasDifferentAccessibility) {
7153                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7154                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
7155                                                 GetSignatureForError ());
7156                                 } else {
7157                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
7158                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
7159                                 }
7160                         }
7161
7162                         if (best_candidate.HasDifferentAccessibility)
7163                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
7164
7165                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
7166                         return this;
7167                 }
7168
7169                 void EmitConditionalAccess (EmitContext ec, ref CallEmitter call, MethodSpec method, Arguments arguments)
7170                 {
7171                         ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7172
7173                         call.Emit (ec, method, arguments, loc);
7174
7175                         ec.CloseConditionalAccess (method.ReturnType != type && type.IsNullableType ? type : null);
7176                 }
7177
7178                 //
7179                 // Implements the IAssignMethod interface for assignments
7180                 //
7181                 public virtual void Emit (EmitContext ec, bool leave_copy)
7182                 {
7183                         var call = new CallEmitter ();
7184                         call.ConditionalAccess = ConditionalAccess;
7185                         call.InstanceExpression = InstanceExpression;
7186                         if (has_await_arguments)
7187                                 call.HasAwaitArguments = true;
7188                         else
7189                                 call.DuplicateArguments = emitting_compound_assignment;
7190
7191                         if (conditional_access_receiver)
7192                                 EmitConditionalAccess (ec, ref call, Getter, Arguments);
7193                         else
7194                                 call.Emit (ec, Getter, Arguments, loc);
7195
7196                         if (call.HasAwaitArguments) {
7197                                 InstanceExpression = call.InstanceExpression;
7198                                 Arguments = call.EmittedArguments;
7199                                 has_await_arguments = true;
7200                         }
7201
7202                         if (leave_copy) {
7203                                 ec.Emit (OpCodes.Dup);
7204                                 temp = new LocalTemporary (Type);
7205                                 temp.Store (ec);
7206                         }
7207                 }
7208
7209                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
7210
7211                 public override void Emit (EmitContext ec)
7212                 {
7213                         Emit (ec, false);
7214                 }
7215
7216                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
7217                 {
7218                         has_await_arguments = true;
7219                         Emit (ec, false);
7220                         return null;
7221                 }
7222
7223                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
7224
7225                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
7226
7227                 bool ResolveGetter (ResolveContext rc)
7228                 {
7229                         if (!best_candidate.HasGet) {
7230                                 if (InstanceExpression != EmptyExpression.Null) {
7231                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
7232                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
7233                                                 best_candidate.GetSignatureForError ());
7234                                         return false;
7235                                 }
7236                         } else if (!best_candidate.Get.IsAccessible (rc) || !best_candidate.Get.DeclaringType.IsAccessible (rc)) {
7237                                 if (best_candidate.HasDifferentAccessibility) {
7238                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7239                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
7240                                                 TypeManager.CSharpSignature (best_candidate));
7241                                 } else {
7242                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
7243                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
7244                                 }
7245                         }
7246
7247                         if (best_candidate.HasDifferentAccessibility) {
7248                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
7249                         }
7250
7251                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
7252                         return true;
7253                 }
7254
7255                 protected virtual bool ResolveAutopropertyAssignment (ResolveContext rc, Expression rhs)
7256                 {
7257                         return false;
7258                 }
7259         }
7260
7261         /// <summary>
7262         ///   Fully resolved expression that evaluates to an Event
7263         /// </summary>
7264         public class EventExpr : MemberExpr, IAssignMethod
7265         {
7266                 readonly EventSpec spec;
7267                 MethodSpec op;
7268
7269                 public EventExpr (EventSpec spec, Location loc)
7270                 {
7271                         this.spec = spec;
7272                         this.loc = loc;
7273                 }
7274
7275                 #region Properties
7276
7277                 protected override TypeSpec DeclaringType {
7278                         get {
7279                                 return spec.DeclaringType;
7280                         }
7281                 }
7282
7283                 public override string Name {
7284                         get {
7285                                 return spec.Name;
7286                         }
7287                 }
7288
7289                 public override bool IsInstance {
7290                         get {
7291                                 return !spec.IsStatic;
7292                         }
7293                 }
7294
7295                 public override bool IsStatic {
7296                         get {
7297                                 return spec.IsStatic;
7298                         }
7299                 }
7300
7301                 public override string KindName {
7302                         get { return "event"; }
7303                 }
7304
7305                 public MethodSpec Operator {
7306                         get {
7307                                 return op;
7308                         }
7309                 }
7310
7311                 #endregion
7312
7313                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
7314                 {
7315                         //
7316                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
7317                         //
7318                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7319                                 if (spec.BackingField != null &&
7320                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
7321
7322                                         spec.MemberDefinition.SetIsUsed ();
7323
7324                                         if (!ec.IsObsolete) {
7325                                                 ObsoleteAttribute oa = spec.GetAttributeObsolete ();
7326                                                 if (oa != null)
7327                                                         AttributeTester.Report_ObsoleteMessage (oa, spec.GetSignatureForError (), loc, ec.Report);
7328                                         }
7329
7330                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
7331                                                 Error_AssignmentEventOnly (ec);
7332
7333                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
7334
7335                                         InstanceExpression = null;
7336
7337                                         return ml.ResolveMemberAccess (ec, left, original);
7338                                 }
7339                         }
7340
7341                         return base.ResolveMemberAccess (ec, left, original);
7342                 }
7343
7344                 public override Expression CreateExpressionTree (ResolveContext ec)
7345                 {
7346                         throw new NotSupportedException ("ET");
7347                 }
7348
7349                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7350                 {
7351                         if (right_side == EmptyExpression.EventAddition) {
7352                                 op = spec.AccessorAdd;
7353                         } else if (right_side == EmptyExpression.EventSubtraction) {
7354                                 op = spec.AccessorRemove;
7355                         }
7356
7357                         if (op == null) {
7358                                 Error_AssignmentEventOnly (ec);
7359                                 return null;
7360                         }
7361
7362                         if (ConditionalAccess)
7363                                 Error_NullPropagatingLValue (ec);
7364
7365                         op = CandidateToBaseOverride (ec, op);
7366                         return this;
7367                 }
7368
7369                 protected override Expression DoResolve (ResolveContext ec)
7370                 {
7371                         eclass = ExprClass.EventAccess;
7372                         type = spec.MemberType;
7373
7374                         ResolveInstanceExpression (ec, null);
7375
7376                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
7377                                 Error_AssignmentEventOnly (ec);
7378                         }
7379
7380                         DoBestMemberChecks (ec, spec);
7381                         return this;
7382                 }
7383
7384                 public override void Emit (EmitContext ec)
7385                 {
7386                         throw new NotSupportedException ();
7387                         //Error_CannotAssign ();
7388                 }
7389
7390                 #region IAssignMethod Members
7391
7392                 public void Emit (EmitContext ec, bool leave_copy)
7393                 {
7394                         throw new NotImplementedException ();
7395                 }
7396
7397                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
7398                 {
7399                         if (leave_copy || !isCompound)
7400                                 throw new NotImplementedException ("EventExpr::EmitAssign");
7401
7402                         Arguments args = new Arguments (1);
7403                         args.Add (new Argument (source));
7404
7405                         // TODO: Wrong, needs receiver
7406 //                      if (NullShortCircuit) {
7407 //                              ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
7408 //                      }
7409
7410                         var call = new CallEmitter ();
7411                         call.InstanceExpression = InstanceExpression;
7412                         call.ConditionalAccess = ConditionalAccess;
7413                         call.EmitStatement (ec, op, args, loc);
7414
7415 //                      if (NullShortCircuit)
7416 //                              ec.CloseConditionalAccess (null);
7417                 }
7418
7419                 #endregion
7420
7421                 void Error_AssignmentEventOnly (ResolveContext ec)
7422                 {
7423                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
7424                                 ec.Report.Error (79, loc,
7425                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
7426                                         GetSignatureForError ());
7427                         } else {
7428                                 ec.Report.Error (70, loc,
7429                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
7430                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
7431                         }
7432                 }
7433
7434                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
7435                 {
7436                         name = name.Substring (0, name.LastIndexOf ('.'));
7437                         base.Error_CannotCallAbstractBase (rc, name);
7438                 }
7439
7440                 public override string GetSignatureForError ()
7441                 {
7442                         return TypeManager.CSharpSignature (spec);
7443                 }
7444
7445                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
7446                 {
7447                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
7448                 }
7449         }
7450
7451         public class TemporaryVariableReference : VariableReference
7452         {
7453                 public class Declarator : Statement
7454                 {
7455                         TemporaryVariableReference variable;
7456
7457                         public Declarator (TemporaryVariableReference variable)
7458                         {
7459                                 this.variable = variable;
7460                                 loc = variable.loc;
7461                         }
7462
7463                         protected override void DoEmit (EmitContext ec)
7464                         {
7465                                 variable.li.CreateBuilder (ec);
7466                         }
7467
7468                         public override void Emit (EmitContext ec)
7469                         {
7470                                 // Don't create sequence point
7471                                 DoEmit (ec);
7472                         }
7473
7474                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
7475                         {
7476                                 return false;
7477                         }
7478
7479                         protected override void CloneTo (CloneContext clonectx, Statement target)
7480                         {
7481                                 // Nothing
7482                         }
7483                 }
7484
7485                 LocalVariable li;
7486
7487                 public TemporaryVariableReference (LocalVariable li, Location loc)
7488                 {
7489                         this.li = li;
7490                         this.type = li.Type;
7491                         this.loc = loc;
7492                 }
7493
7494                 public override bool IsLockedByStatement {
7495                         get {
7496                                 return false;
7497                         }
7498                         set {
7499                         }
7500                 }
7501
7502                 public LocalVariable LocalInfo {
7503                     get {
7504                         return li;
7505                     }
7506                 }
7507
7508                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc)
7509                 {
7510                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc);
7511                         return new TemporaryVariableReference (li, loc);
7512                 }
7513
7514                 protected override Expression DoResolve (ResolveContext ec)
7515                 {
7516                         eclass = ExprClass.Variable;
7517
7518                         //
7519                         // Don't capture temporary variables except when using
7520                         // state machine redirection and block yields
7521                         //
7522                         if (ec.CurrentAnonymousMethod is StateMachineInitializer &&
7523                                 (ec.CurrentBlock.Explicit.HasYield || ec.CurrentBlock.Explicit.HasAwait) &&
7524                                 ec.IsVariableCapturingRequired) {
7525                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
7526                                 storey.CaptureLocalVariable (ec, li);
7527                         }
7528
7529                         return this;
7530                 }
7531
7532                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
7533                 {
7534                         return Resolve (ec);
7535                 }
7536
7537                 public override void Emit (EmitContext ec)
7538                 {
7539                         li.CreateBuilder (ec);
7540
7541                         Emit (ec, false);
7542                 }
7543
7544                 public void EmitAssign (EmitContext ec, Expression source)
7545                 {
7546                         li.CreateBuilder (ec);
7547
7548                         EmitAssign (ec, source, false, false);
7549                 }
7550
7551                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
7552                 {
7553                         return li.HoistedVariant;
7554                 }
7555
7556                 public override bool IsFixed {
7557                         get { return true; }
7558                 }
7559
7560                 public override bool IsRef {
7561                         get { return false; }
7562                 }
7563
7564                 public override string Name {
7565                         get { throw new NotImplementedException (); }
7566                 }
7567
7568                 public override void SetHasAddressTaken ()
7569                 {
7570                         throw new NotImplementedException ();
7571                 }
7572
7573                 protected override ILocalVariable Variable {
7574                         get { return li; }
7575                 }
7576
7577                 public override VariableInfo VariableInfo {
7578                         get { return null; }
7579                 }
7580         }
7581
7582         ///
7583         /// Handles `var' contextual keyword; var becomes a keyword only
7584         /// if no type called var exists in a variable scope
7585         ///
7586         class VarExpr : SimpleName
7587         {
7588                 public VarExpr (Location loc)
7589                         : base ("var", loc)
7590                 {
7591                 }
7592
7593                 public bool InferType (ResolveContext ec, Expression right_side)
7594                 {
7595                         if (type != null)
7596                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
7597
7598                         type = right_side.Type;
7599                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
7600                                 ec.Report.Error (815, loc,
7601                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
7602                                         type.GetSignatureForError ());
7603                                 return false;
7604                         }
7605
7606                         eclass = ExprClass.Variable;
7607                         return true;
7608                 }
7609
7610                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
7611                 {
7612                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
7613                                 base.Error_TypeOrNamespaceNotFound (ec);
7614                         else
7615                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
7616                 }
7617         }
7618 }