mcs/mcs/ecore.cs

   1 //
   2 // ecore.cs: Core of the Expression representation for the intermediate tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Copyright 2001, 2002, 2003 Ximian, Inc.
   9 // Copyright 2003-2008 Novell, Inc.
  10 // Copyright 2011-2012 Xamarin Inc.
  11 //
  12 //
  13
  14 using System;
  15 using System.Collections.Generic;
  16 using System.Text;
  17 using SLE = System.Linq.Expressions;
  18 using System.Linq;
  19
  20 #if STATIC
  21 using IKVM.Reflection;
  22 using IKVM.Reflection.Emit;
  23 #else
  24 using System.Reflection;
  25 using System.Reflection.Emit;
  26 #endif
  27
  28 namespace Mono.CSharp {
  29
  30         /// <remarks>
  31         ///   The ExprClass class contains the is used to pass the
  32         ///   classification of an expression (value, variable, namespace,
  33         ///   type, method group, property access, event access, indexer access,
  34         ///   nothing).
  35         /// </remarks>
  36         public enum ExprClass : byte {
  37                 Unresolved      = 0,
  38
  39                 Value,
  40                 Variable,
  41                 Namespace,
  42                 Type,
  43                 TypeParameter,
  44                 MethodGroup,
  45                 PropertyAccess,
  46                 EventAccess,
  47                 IndexerAccess,
  48                 Nothing,
  49         }
  50
  51         /// <remarks>
  52         ///   This is used to tell Resolve in which types of expressions we're
  53         ///   interested.
  54         /// </remarks>
  55         [Flags]
  56         public enum ResolveFlags {
  57                 // Returns Value, Variable, PropertyAccess, EventAccess or IndexerAccess.
  58                 VariableOrValue         = 1,
  59
  60                 // Returns a type expression.
  61                 Type                    = 1 << 1,
  62
  63                 // Returns a method group.
  64                 MethodGroup             = 1 << 2,
  65
  66                 TypeParameter   = 1 << 3,
  67
  68                 // Mask of all the expression class flags.
  69                 MaskExprClass = VariableOrValue | Type | MethodGroup | TypeParameter,
  70         }
  71
  72         //
  73         // This is just as a hint to AddressOf of what will be done with the
  74         // address.
  75         [Flags]
  76         public enum AddressOp {
  77                 Store = 1,
  78                 Load  = 2,
  79                 LoadStore = 3
  80         };
  81
  82         /// <summary>
  83         ///   This interface is implemented by variables
  84         /// </summary>
  85         public interface IMemoryLocation {
  86                 /// <summary>
  87                 ///   The AddressOf method should generate code that loads
  88                 ///   the address of the object and leaves it on the stack.
  89                 ///
  90                 ///   The `mode' argument is used to notify the expression
  91                 ///   of whether this will be used to read from the address or
  92                 ///   write to the address.
  93                 ///
  94                 ///   This is just a hint that can be used to provide good error
  95                 ///   reporting, and should have no other side effects.
  96                 /// </summary>
  97                 void AddressOf (EmitContext ec, AddressOp mode);
  98         }
  99
 100         //
 101         // An expressions resolved as a direct variable reference
 102         //
 103         public interface IVariableReference : IFixedExpression
 104         {
 105                 bool IsHoisted { get; }
 106                 string Name { get; }
 107                 VariableInfo VariableInfo { get; }
 108
 109                 void SetHasAddressTaken ();
 110         }
 111
 112         //
 113         // Implemented by an expression which could be or is always
 114         // fixed
 115         //
 116         public interface IFixedExpression
 117         {
 118                 bool IsFixed { get; }
 119         }
 120
 121         public interface IExpressionCleanup
 122         {
 123                 void EmitCleanup (EmitContext ec);
 124         }
 125
 126         /// <remarks>
 127         ///   Base class for expressions
 128         /// </remarks>
 129         public abstract class Expression {
 130                 public ExprClass eclass;
 131                 protected TypeSpec type;
 132                 protected Location loc;
 133
 134                 public TypeSpec Type {
 135                         get { return type; }
 136                         set { type = value; }
 137                 }
 138
 139                 public virtual bool IsSideEffectFree {
 140                         get {
 141                                 return false;
 142                         }
 143                 }
 144
 145                 public Location Location {
 146                         get { return loc; }
 147                 }
 148
 149                 public virtual bool IsNull {
 150                         get {
 151                                 return false;
 152                         }
 153                 }
 154
 155                 //
 156                 // Used to workaround parser limitation where we cannot get
 157                 // start of statement expression location
 158                 //
 159                 public virtual Location StartLocation {
 160                         get {
 161                                 return loc;
 162                         }
 163                 }
 164
 165                 public virtual MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
 166                 {
 167                         //
 168                         // Return method-group expression when the expression can be used as
 169                         // lambda replacement. A good example is array sorting where instead of
 170                         // code like
 171                         //
 172                         //  Array.Sort (s, (a, b) => String.Compare (a, b));
 173                         //
 174                         // we can use method group directly
 175                         //
 176                         //  Array.Sort (s, String.Compare);
 177                         //
 178                         // Correct overload will be used because we do the reduction after
 179                         // best candidate was found.
 180                         //
 181                         return null;
 182                 }
 183
 184                 //
 185                 // Returns true when the expression during Emit phase breaks stack
 186                 // by using await expression
 187                 //
 188                 public virtual bool ContainsEmitWithAwait ()
 189                 {
 190                         return false;
 191                 }
 192
 193                 /// <summary>
 194                 ///   Performs semantic analysis on the Expression
 195                 /// </summary>
 196                 ///
 197                 /// <remarks>
 198                 ///   The Resolve method is invoked to perform the semantic analysis
 199                 ///   on the node.
 200                 ///
 201                 ///   The return value is an expression (it can be the
 202                 ///   same expression in some cases) or a new
 203                 ///   expression that better represents this node.
 204                 ///
 205                 ///   For example, optimizations of Unary (LiteralInt)
 206                 ///   would return a new LiteralInt with a negated
 207                 ///   value.
 208                 ///
 209                 ///   If there is an error during semantic analysis,
 210                 ///   then an error should be reported (using Report)
 211                 ///   and a null value should be returned.
 212                 ///
 213                 ///   There are two side effects expected from calling
 214                 ///   Resolve(): the the field variable "eclass" should
 215                 ///   be set to any value of the enumeration
 216                 ///   `ExprClass' and the type variable should be set
 217                 ///   to a valid type (this is the type of the
 218                 ///   expression).
 219                 /// </remarks>
 220                 protected abstract Expression DoResolve (ResolveContext rc);
 221
 222                 public virtual Expression DoResolveLValue (ResolveContext rc, Expression right_side)
 223                 {
 224                         return null;
 225                 }
 226
 227                 //
 228                 // This is used if the expression should be resolved as a type or namespace name.
 229                 // the default implementation fails.
 230                 //
 231                 public virtual TypeSpec ResolveAsType (IMemberContext mc)
 232                 {
 233                         ResolveContext ec = new ResolveContext (mc);
 234                         Expression e = Resolve (ec);
 235                         if (e != null)
 236                                 e.Error_UnexpectedKind (ec, ResolveFlags.Type, loc);
 237
 238                         return null;
 239                 }
 240
 241                 public static void ErrorIsInaccesible (IMemberContext rc, string member, Location loc)
 242                 {
 243                         rc.Module.Compiler.Report.Error (122, loc, "`{0}' is inaccessible due to its protection level", member);
 244                 }
 245
 246                 public void Error_ExpressionMustBeConstant (ResolveContext rc, Location loc, string e_name)
 247                 {
 248                         rc.Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
 249                 }
 250
 251                 public void Error_ConstantCanBeInitializedWithNullOnly (ResolveContext rc, TypeSpec type, Location loc, string name)
 252                 {
 253                         rc.Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
 254                                 name, type.GetSignatureForError ());
 255                 }
 256
 257                 protected virtual void Error_InvalidExpressionStatement (Report report, Location loc)
 258                 {
 259                         report.Error (201, loc, "Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement");
 260                 }
 261
 262                 public void Error_InvalidExpressionStatement (BlockContext bc)
 263                 {
 264                         Error_InvalidExpressionStatement (bc.Report, loc);
 265                 }
 266
 267                 public void Error_InvalidExpressionStatement (Report report)
 268                 {
 269                         Error_InvalidExpressionStatement (report, loc);
 270                 }
 271
 272                 public static void Error_VoidInvalidInTheContext (Location loc, Report Report)
 273                 {
 274                         Report.Error (1547, loc, "Keyword `void' cannot be used in this context");
 275                 }
 276
 277                 public virtual void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
 278                 {
 279                         Error_ValueCannotBeConvertedCore (ec, loc, target, expl);
 280                 }
 281
 282                 protected void Error_ValueCannotBeConvertedCore (ResolveContext ec, Location loc, TypeSpec target, bool expl)
 283                 {
 284                         // The error was already reported as CS1660
 285                         if (type == InternalType.AnonymousMethod)
 286                                 return;
 287
 288                         if (type == InternalType.ErrorType || target == InternalType.ErrorType)
 289                                 return;
 290
 291                         string from_type = type.GetSignatureForError ();
 292                         string to_type = target.GetSignatureForError ();
 293                         if (from_type == to_type) {
 294                                 from_type = type.GetSignatureForErrorIncludingAssemblyName ();
 295                                 to_type = target.GetSignatureForErrorIncludingAssemblyName ();
 296                         }
 297
 298                         if (expl) {
 299                                 ec.Report.Error (30, loc, "Cannot convert type `{0}' to `{1}'",
 300                                         from_type, to_type);
 301                                 return;
 302                         }
 303
 304                         ec.Report.DisableReporting ();
 305                         bool expl_exists = Convert.ExplicitConversion (ec, this, target, Location.Null) != null;
 306                         ec.Report.EnableReporting ();
 307
 308                         if (expl_exists) {
 309                                 ec.Report.Error (266, loc,
 310                                         "Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
 311                                         from_type, to_type);
 312                         } else {
 313                                 ec.Report.Error (29, loc, "Cannot implicitly convert type `{0}' to `{1}'",
 314                                         from_type, to_type);
 315                         }
 316                 }
 317
 318                 public void Error_TypeArgumentsCannotBeUsed (IMemberContext context, MemberSpec member, Location loc)
 319                 {
 320                         // Better message for possible generic expressions
 321                         if (member != null && (member.Kind & MemberKind.GenericMask) != 0) {
 322                                 var report = context.Module.Compiler.Report;
 323                                 report.SymbolRelatedToPreviousError (member);
 324                                 if (member is TypeSpec)
 325                                         member = ((TypeSpec) member).GetDefinition ();
 326                                 else
 327                                         member = ((MethodSpec) member).GetGenericMethodDefinition ();
 328
 329                                 string name = member.Kind == MemberKind.Method ? "method" : "type";
 330                                 if (member.IsGeneric) {
 331                                         report.Error (305, loc, "Using the generic {0} `{1}' requires `{2}' type argument(s)",
 332                                                 name, member.GetSignatureForError (), member.Arity.ToString ());
 333                                 } else {
 334                                         report.Error (308, loc, "The non-generic {0} `{1}' cannot be used with the type arguments",
 335                                                 name, member.GetSignatureForError ());
 336                                 }
 337                         } else {
 338                                 Error_TypeArgumentsCannotBeUsed (context, ExprClassName, GetSignatureForError (), loc);
 339                         }
 340                 }
 341
 342                 public static void Error_TypeArgumentsCannotBeUsed (IMemberContext context, string exprType, string name, Location loc)
 343                 {
 344                         context.Module.Compiler.Report.Error (307, loc, "The {0} `{1}' cannot be used with type arguments",
 345                                 exprType, name);
 346                 }
 347
 348                 protected virtual void Error_TypeDoesNotContainDefinition (ResolveContext ec, TypeSpec type, string name)
 349                 {
 350                         Error_TypeDoesNotContainDefinition (ec, loc, type, name);
 351                 }
 352
 353                 public static void Error_TypeDoesNotContainDefinition (ResolveContext ec, Location loc, TypeSpec type, string name)
 354                 {
 355                         ec.Report.SymbolRelatedToPreviousError (type);
 356                         ec.Report.Error (117, loc, "`{0}' does not contain a definition for `{1}'",
 357                                 type.GetSignatureForError (), name);
 358                 }
 359
 360                 public virtual void Error_ValueAssignment (ResolveContext rc, Expression rhs)
 361                 {
 362                         if (rhs == EmptyExpression.LValueMemberAccess || rhs == EmptyExpression.LValueMemberOutAccess) {
 363                                 // Already reported as CS1612
 364                         } else if (rhs == EmptyExpression.OutAccess) {
 365                                 rc.Report.Error (1510, loc, "A ref or out argument must be an assignable variable");
 366                         } else {
 367                                 rc.Report.Error (131, loc, "The left-hand side of an assignment must be a variable, a property or an indexer");
 368                         }
 369                 }
 370
 371                 protected void Error_VoidPointerOperation (ResolveContext rc)
 372                 {
 373                         rc.Report.Error (242, loc, "The operation in question is undefined on void pointers");
 374                 }
 375
 376                 public static void Warning_UnreachableExpression (ResolveContext rc, Location loc)
 377                 {
 378                         rc.Report.Warning (429, 4, loc, "Unreachable expression code detected");
 379                 }
 380
 381                 public ResolveFlags ExprClassToResolveFlags {
 382                         get {
 383                                 switch (eclass) {
 384                                 case ExprClass.Type:
 385                                 case ExprClass.Namespace:
 386                                         return ResolveFlags.Type;
 387
 388                                 case ExprClass.MethodGroup:
 389                                         return ResolveFlags.MethodGroup;
 390
 391                                 case ExprClass.TypeParameter:
 392                                         return ResolveFlags.TypeParameter;
 393
 394                                 case ExprClass.Value:
 395                                 case ExprClass.Variable:
 396                                 case ExprClass.PropertyAccess:
 397                                 case ExprClass.EventAccess:
 398                                 case ExprClass.IndexerAccess:
 399                                         return ResolveFlags.VariableOrValue;
 400
 401                                 default:
 402                                         throw new InternalErrorException (loc.ToString () + " " +  GetType () + " ExprClass is Invalid after resolve");
 403                                 }
 404                         }
 405                 }
 406
 407                 //
 408                 // Implements identical simple name and type-name resolution
 409                 //
 410                 public Expression ProbeIdenticalTypeName (ResolveContext rc, Expression left, SimpleName name)
 411                 {
 412                         var t = left.Type;
 413                         if (t.Kind == MemberKind.InternalCompilerType || t is ElementTypeSpec || t.Arity > 0)
 414                                 return left;
 415
 416                         // In a member access of the form E.I, if E is a single identifier, and if the meaning of E as a simple-name is
 417                         // a constant, field, property, local variable, or parameter with the same type as the meaning of E as a type-name
 418
 419                         if (left is MemberExpr || left is VariableReference) {
 420                                 var identical_type = rc.LookupNamespaceOrType (name.Name, 0, LookupMode.Probing, loc) as TypeExpr;
 421                                 if (identical_type != null && identical_type.Type == left.Type)
 422                                         return identical_type;
 423                         }
 424
 425                         return left;
 426                 }
 427
 428                 public virtual string GetSignatureForError ()
 429                 {
 430                         return type.GetDefinition ().GetSignatureForError ();
 431                 }
 432
 433                 /// <summary>
 434                 ///   Resolves an expression and performs semantic analysis on it.
 435                 /// </summary>
 436                 ///
 437                 /// <remarks>
 438                 ///   Currently Resolve wraps DoResolve to perform sanity
 439                 ///   checking and assertion checking on what we expect from Resolve.
 440                 /// </remarks>
 441                 public Expression Resolve (ResolveContext ec, ResolveFlags flags)
 442                 {
 443                         if (eclass != ExprClass.Unresolved) {
 444                                 if ((flags & ExprClassToResolveFlags) == 0) {
 445                                         Error_UnexpectedKind (ec, flags, loc);
 446                                         return null;
 447                                 }
 448
 449                                 return this;
 450                         }
 451
 452                         Expression e;
 453                         try {
 454                                 e = DoResolve (ec);
 455
 456                                 if (e == null)
 457                                         return null;
 458
 459                                 if ((flags & e.ExprClassToResolveFlags) == 0) {
 460                                         e.Error_UnexpectedKind (ec, flags, loc);
 461                                         return null;
 462                                 }
 463
 464                                 if (e.type == null)
 465                                         throw new InternalErrorException ("Expression `{0}' didn't set its type in DoResolve", e.GetType ());
 466
 467                                 return e;
 468                         } catch (Exception ex) {
 469                                 if (loc.IsNull || ec.Module.Compiler.Settings.DebugFlags > 0 || ex is CompletionResult || ec.Report.IsDisabled || ex is FatalException ||
 470                                         ec.Report.Printer is NullReportPrinter)
 471                                         throw;
 472
 473                                 ec.Report.Error (584, loc, "Internal compiler error: {0}", ex.Message);
 474                                 return ErrorExpression.Instance;        // TODO: Add location
 475                         }
 476                 }
 477
 478                 /// <summary>
 479                 ///   Resolves an expression and performs semantic analysis on it.
 480                 /// </summary>
 481                 public Expression Resolve (ResolveContext rc)
 482                 {
 483                         return Resolve (rc, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup);
 484                 }
 485
 486                 /// <summary>
 487                 ///   Resolves an expression for LValue assignment
 488                 /// </summary>
 489                 ///
 490                 /// <remarks>
 491                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 492                 ///   checking and assertion checking on what we expect from Resolve
 493                 /// </remarks>
 494                 public Expression ResolveLValue (ResolveContext ec, Expression right_side)
 495                 {
 496                         int errors = ec.Report.Errors;
 497                         bool out_access = right_side == EmptyExpression.OutAccess;
 498
 499                         Expression e = DoResolveLValue (ec, right_side);
 500
 501                         if (e != null && out_access && !(e is IMemoryLocation)) {
 502                                 // FIXME: There's no problem with correctness, the 'Expr = null' handles that.
 503                                 //        Enabling this 'throw' will "only" result in deleting useless code elsewhere,
 504
 505                                 //throw new InternalErrorException ("ResolveLValue didn't return an IMemoryLocation: " +
 506                                 //                                e.GetType () + " " + e.GetSignatureForError ());
 507                                 e = null;
 508                         }
 509
 510                         if (e == null) {
 511                                 if (errors == ec.Report.Errors) {
 512                                         Error_ValueAssignment (ec, right_side);
 513                                 }
 514                                 return null;
 515                         }
 516
 517                         if (e.eclass == ExprClass.Unresolved)
 518                                 throw new Exception ("Expression " + e + " ExprClass is Invalid after resolve");
 519
 520                         if ((e.type == null) && !(e is GenericTypeExpr))
 521                                 throw new Exception ("Expression " + e + " did not set its type after Resolve");
 522
 523                         return e;
 524                 }
 525
 526                 public Constant ResolveLabelConstant (ResolveContext rc)
 527                 {
 528                         var expr = Resolve (rc);
 529                         if (expr == null)
 530                                 return null;
 531
 532                         Constant c = expr as Constant;
 533                         if (c == null) {
 534                                 if (expr.type != InternalType.ErrorType)
 535                                         rc.Report.Error (150, expr.StartLocation, "A constant value is expected");
 536
 537                                 return null;
 538                         }
 539
 540                         return c;
 541                 }
 542
 543                 public virtual void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
 544                 {
 545                         rc.Module.Compiler.Report.Error (182, loc,
 546                                 "An attribute argument must be a constant expression, typeof expression or array creation expression");
 547                 }
 548
 549                 /// <summary>
 550                 ///   Emits the code for the expression
 551                 /// </summary>
 552                 ///
 553                 /// <remarks>
 554                 ///   The Emit method is invoked to generate the code
 555                 ///   for the expression.
 556                 /// </remarks>
 557                 public abstract void Emit (EmitContext ec);
 558
 559
 560                 // Emit code to branch to @target if this expression is equivalent to @on_true.
 561                 // The default implementation is to emit the value, and then emit a brtrue or brfalse.
 562                 // Subclasses can provide more efficient implementations, but those MUST be equivalent,
 563                 // including the use of conditional branches.  Note also that a branch MUST be emitted
 564                 public virtual void EmitBranchable (EmitContext ec, Label target, bool on_true)
 565                 {
 566                         Emit (ec);
 567                         ec.Emit (on_true ? OpCodes.Brtrue : OpCodes.Brfalse, target);
 568                 }
 569
 570                 // Emit this expression for its side effects, not for its value.
 571                 // The default implementation is to emit the value, and then throw it away.
 572                 // Subclasses can provide more efficient implementations, but those MUST be equivalent
 573                 public virtual void EmitSideEffect (EmitContext ec)
 574                 {
 575                         Emit (ec);
 576                         ec.Emit (OpCodes.Pop);
 577                 }
 578
 579                 //
 580                 // Emits the expression into temporary field variable. The method
 581                 // should be used for await expressions only
 582                 //
 583                 public virtual Expression EmitToField (EmitContext ec)
 584                 {
 585                         //
 586                         // This is the await prepare Emit method. When emitting code like
 587                         // a + b we emit code like
 588                         //
 589                         // a.Emit ()
 590                         // b.Emit ()
 591                         // Opcodes.Add
 592                         //
 593                         // For await a + await b we have to interfere the flow to keep the
 594                         // stack clean because await yields from the expression. The emit
 595                         // then changes to
 596                         //
 597                         // a = a.EmitToField () // a is changed to temporary field access
 598                         // b = b.EmitToField ()
 599                         // a.Emit ()
 600                         // b.Emit ()
 601                         // Opcodes.Add
 602                         //
 603                         //
 604                         // The idea is to emit expression and leave the stack empty with
 605                         // result value still available.
 606                         //
 607                         // Expressions should override this default implementation when
 608                         // optimized version can be provided (e.g. FieldExpr)
 609                         //
 610                         //
 611                         // We can optimize for side-effect free expressions, they can be
 612                         // emitted out of order
 613                         //
 614                         if (IsSideEffectFree)
 615                                 return this;
 616
 617                         bool needs_temporary = ContainsEmitWithAwait ();
 618                         if (!needs_temporary)
 619                                 ec.EmitThis ();
 620
 621                         // Emit original code
 622                         var field = EmitToFieldSource (ec);
 623                         if (field == null) {
 624                                 //
 625                                 // Store the result to temporary field when we
 626                                 // cannot load `this' directly
 627                                 //
 628                                 field = ec.GetTemporaryField (type);
 629                                 if (needs_temporary) {
 630                                         //
 631                                         // Create temporary local (we cannot load `this' before Emit)
 632                                         //
 633                                         var temp = ec.GetTemporaryLocal (type);
 634                                         ec.Emit (OpCodes.Stloc, temp);
 635
 636                                         ec.EmitThis ();
 637                                         ec.Emit (OpCodes.Ldloc, temp);
 638                                         field.EmitAssignFromStack (ec);
 639
 640                                         ec.FreeTemporaryLocal (temp, type);
 641                                 } else {
 642                                         field.EmitAssignFromStack (ec);
 643                                 }
 644                         }
 645
 646                         return field;
 647                 }
 648
 649                 protected virtual FieldExpr EmitToFieldSource (EmitContext ec)
 650                 {
 651                         //
 652                         // Default implementation calls Emit method
 653                         //
 654                         Emit (ec);
 655                         return null;
 656                 }
 657
 658                 protected static void EmitExpressionsList (EmitContext ec, List<Expression> expressions)
 659                 {
 660                         if (ec.HasSet (BuilderContext.Options.AsyncBody)) {
 661                                 bool contains_await = false;
 662
 663                                 for (int i = 1; i < expressions.Count; ++i) {
 664                                         if (expressions[i].ContainsEmitWithAwait ()) {
 665                                                 contains_await = true;
 666                                                 break;
 667                                         }
 668                                 }
 669
 670                                 if (contains_await) {
 671                                         for (int i = 0; i < expressions.Count; ++i) {
 672                                                 expressions[i] = expressions[i].EmitToField (ec);
 673                                         }
 674                                 }
 675                         }
 676
 677                         for (int i = 0; i < expressions.Count; ++i) {
 678                                 expressions[i].Emit (ec);
 679                         }
 680                 }
 681
 682                 /// <summary>
 683                 ///   Protected constructor.  Only derivate types should
 684                 ///   be able to be created
 685                 /// </summary>
 686
 687                 protected Expression ()
 688                 {
 689                 }
 690
 691                 /// <summary>
 692                 ///   Returns a fully formed expression after a MemberLookup
 693                 /// </summary>
 694                 ///
 695                 static Expression ExprClassFromMemberInfo (MemberSpec spec, Location loc)
 696                 {
 697                         if (spec is EventSpec)
 698                                 return new EventExpr ((EventSpec) spec, loc);
 699                         if (spec is ConstSpec)
 700                                 return new ConstantExpr ((ConstSpec) spec, loc);
 701                         if (spec is FieldSpec)
 702                                 return new FieldExpr ((FieldSpec) spec, loc);
 703                         if (spec is PropertySpec)
 704                                 return new PropertyExpr ((PropertySpec) spec, loc);
 705                         if (spec is TypeSpec)
 706                                 return new TypeExpression (((TypeSpec) spec), loc);
 707
 708                         return null;
 709                 }
 710
 711                 public static MethodSpec ConstructorLookup (ResolveContext rc, TypeSpec type, ref Arguments args, Location loc)
 712                 {
 713                         var ctors = MemberCache.FindMembers (type, Constructor.ConstructorName, true);
 714                         if (ctors == null) {
 715                                 switch (type.Kind) {
 716                                 case MemberKind.Struct:
 717                                         rc.Report.SymbolRelatedToPreviousError (type);
 718                                         // Report meaningful error for struct as they always have default ctor in C# context
 719                                         OverloadResolver.Error_ConstructorMismatch (rc, type, args == null ? 0 : args.Count, loc);
 720                                         break;
 721                                 case MemberKind.MissingType:
 722                                 case MemberKind.InternalCompilerType:
 723                                         break;
 724                                 default:
 725                                         rc.Report.SymbolRelatedToPreviousError (type);
 726                                         rc.Report.Error (143, loc, "The class `{0}' has no constructors defined",
 727                                                 type.GetSignatureForError ());
 728                                         break;
 729                                 }
 730
 731                                 return null;
 732                         }
 733
 734                         var r = new OverloadResolver (ctors, OverloadResolver.Restrictions.NoBaseMembers, loc);
 735                         if (!rc.HasSet (ResolveContext.Options.BaseInitializer)) {
 736                                 r.InstanceQualifier = new ConstructorInstanceQualifier (type);
 737                         }
 738
 739                         return r.ResolveMember<MethodSpec> (rc, ref args);
 740                 }
 741
 742                 [Flags]
 743                 public enum MemberLookupRestrictions
 744                 {
 745                         None = 0,
 746                         InvocableOnly = 1,
 747                         ExactArity = 1 << 2,
 748                         ReadAccess = 1 << 3
 749                 }
 750
 751                 //
 752                 // Lookup type `queried_type' for code in class `container_type' with a qualifier of
 753                 // `qualifier_type' or null to lookup members in the current class.
 754                 //
 755                 public static Expression MemberLookup (IMemberContext rc, bool errorMode, TypeSpec queried_type, string name, int arity, MemberLookupRestrictions restrictions, Location loc)
 756                 {
 757                         var members = MemberCache.FindMembers (queried_type, name, false);
 758                         if (members == null)
 759                                 return null;
 760
 761                         MemberSpec non_method = null;
 762                         MemberSpec ambig_non_method = null;
 763                         do {
 764                                 for (int i = 0; i < members.Count; ++i) {
 765                                         var member = members[i];
 766
 767                                         // HACK: for events because +=/-= can appear at same class only, should use OverrideToBase there
 768                                         if ((member.Modifiers & Modifiers.OVERRIDE) != 0 && member.Kind != MemberKind.Event)
 769                                                 continue;
 770
 771                                         if ((member.Modifiers & Modifiers.BACKING_FIELD) != 0 || member.Kind == MemberKind.Operator)
 772                                                 continue;
 773
 774                                         if ((arity > 0 || (restrictions & MemberLookupRestrictions.ExactArity) != 0) && member.Arity != arity)
 775                                                 continue;
 776
 777                                         if (!errorMode) {
 778                                                 if (!member.IsAccessible (rc))
 779                                                         continue;
 780
 781                                                 //
 782                                                 // With runtime binder we can have a situation where queried type is inaccessible
 783                                                 // because it came via dynamic object, the check about inconsisted accessibility
 784                                                 // had no effect as the type was unknown during compilation
 785                                                 //
 786                                                 // class A {
 787                                                 //              private class N { }
 788                                                 //
 789                                                 //              public dynamic Foo ()
 790                                                 //              {
 791                                                 //                      return new N ();
 792                                                 //              }
 793                                                 //      }
 794                                                 //
 795                                                 if (rc.Module.Compiler.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
 796                                                         continue;
 797                                         }
 798
 799                                         if ((restrictions & MemberLookupRestrictions.InvocableOnly) != 0) {
 800                                                 if (member is MethodSpec) {
 801                                                         //
 802                                                         // Interface members that are hidden by class members are removed from the set. This
 803                                                         // step only has an effect if T is a type parameter and T has both an effective base
 804                                                         // class other than object and a non-empty effective interface set
 805                                                         //
 806                                                         var tps = queried_type as TypeParameterSpec;
 807                                                         if (tps != null && tps.HasTypeConstraint)
 808                                                                 members = RemoveHiddenTypeParameterMethods (members);
 809
 810                                                         return new MethodGroupExpr (members, queried_type, loc);
 811                                                 }
 812
 813                                                 if (!Invocation.IsMemberInvocable (member))
 814                                                         continue;
 815                                         }
 816
 817                                         if (non_method == null || member is MethodSpec || non_method.IsNotCSharpCompatible) {
 818                                                 non_method = member;
 819                                         } else if (!errorMode && !member.IsNotCSharpCompatible) {
 820                                                 //
 821                                                 // Interface members that are hidden by class members are removed from the set when T is a type parameter and
 822                                                 // T has both an effective base class other than object and a non-empty effective interface set.
 823                                                 //
 824                                                 // The spec has more complex rules but we simply remove all members declared in an interface declaration.
 825                                                 //
 826                                                 var tps = queried_type as TypeParameterSpec;
 827                                                 if (tps != null && tps.HasTypeConstraint) {
 828                                                         if (non_method.DeclaringType.IsClass && member.DeclaringType.IsInterface)
 829                                                                 continue;
 830
 831                                                         if (non_method.DeclaringType.IsInterface && member.DeclaringType.IsInterface) {
 832                                                                 non_method = member;
 833                                                                 continue;
 834                                                         }
 835                                                 }
 836
 837                                                 ambig_non_method = member;
 838                                         }
 839                                 }
 840
 841                                 if (non_method != null) {
 842                                         if (ambig_non_method != null && rc != null) {
 843                                                 var report = rc.Module.Compiler.Report;
 844                                                 report.SymbolRelatedToPreviousError (non_method);
 845                                                 report.SymbolRelatedToPreviousError (ambig_non_method);
 846                                                 report.Error (229, loc, "Ambiguity between `{0}' and `{1}'",
 847                                                         non_method.GetSignatureForError (), ambig_non_method.GetSignatureForError ());
 848                                         }
 849
 850                                         if (non_method is MethodSpec)
 851                                                 return new MethodGroupExpr (members, queried_type, loc);
 852
 853                                         return ExprClassFromMemberInfo (non_method, loc);
 854                                 }
 855
 856                                 if (members[0].DeclaringType.BaseType == null)
 857                                         members = null;
 858                                 else
 859                                         members = MemberCache.FindMembers (members[0].DeclaringType.BaseType, name, false);
 860
 861                         } while (members != null);
 862
 863                         return null;
 864                 }
 865
 866                 static IList<MemberSpec> RemoveHiddenTypeParameterMethods (IList<MemberSpec> members)
 867                 {
 868                         if (members.Count < 2)
 869                                 return members;
 870
 871                         //
 872                         // If M is a method, then all non-method members declared in an interface declaration
 873                         // are removed from the set, and all methods with the same signature as M declared in
 874                         // an interface declaration are removed from the set
 875                         //
 876
 877                         bool copied = false;
 878                         for (int i = 0; i < members.Count; ++i) {
 879                                 var method = members[i] as MethodSpec;
 880                                 if (method == null) {
 881                                         if (!copied) {
 882                                                 copied = true;
 883                                                 members = new List<MemberSpec> (members);
 884                                         }
 885
 886                                         members.RemoveAt (i--);
 887                                         continue;
 888                                 }
 889
 890                                 if (!method.DeclaringType.IsInterface)
 891                                         continue;
 892
 893                                 for (int ii = 0; ii < members.Count; ++ii) {
 894                                         var candidate = members[ii] as MethodSpec;
 895                                         if (candidate == null || !candidate.DeclaringType.IsClass)
 896                                                 continue;
 897
 898                                         if (!TypeSpecComparer.Override.IsEqual (candidate.Parameters, method.Parameters))
 899                                                 continue;
 900
 901                                         if (!copied) {
 902                                                 copied = true;
 903                                                 members = new List<MemberSpec> (members);
 904                                         }
 905
 906                                         members.RemoveAt (i--);
 907                                         break;
 908                                 }
 909                         }
 910
 911                         return members;
 912                 }
 913
 914                 protected virtual void Error_NegativeArrayIndex (ResolveContext ec, Location loc)
 915                 {
 916                         throw new NotImplementedException ();
 917                 }
 918
 919                 public virtual void Error_OperatorCannotBeApplied (ResolveContext rc, Location loc, string oper, TypeSpec t)
 920                 {
 921                         if (t == InternalType.ErrorType)
 922                                 return;
 923
 924                         rc.Report.Error (23, loc, "The `{0}' operator cannot be applied to operand of type `{1}'",
 925                                 oper, t.GetSignatureForError ());
 926                 }
 927
 928                 protected void Error_PointerInsideExpressionTree (ResolveContext ec)
 929                 {
 930                         ec.Report.Error (1944, loc, "An expression tree cannot contain an unsafe pointer operation");
 931                 }
 932
 933                 public virtual void FlowAnalysis (FlowAnalysisContext fc)
 934                 {
 935                 }
 936
 937                 /// <summary>
 938                 ///   Returns an expression that can be used to invoke operator true
 939                 ///   on the expression if it exists.
 940                 /// </summary>
 941                 protected static Expression GetOperatorTrue (ResolveContext ec, Expression e, Location loc)
 942                 {
 943                         return GetOperatorTrueOrFalse (ec, e, true, loc);
 944                 }
 945
 946                 /// <summary>
 947                 ///   Returns an expression that can be used to invoke operator false
 948                 ///   on the expression if it exists.
 949                 /// </summary>
 950                 protected static Expression GetOperatorFalse (ResolveContext ec, Expression e, Location loc)
 951                 {
 952                         return GetOperatorTrueOrFalse (ec, e, false, loc);
 953                 }
 954
 955                 static Expression GetOperatorTrueOrFalse (ResolveContext ec, Expression e, bool is_true, Location loc)
 956                 {
 957                         var op = is_true ? Operator.OpType.True : Operator.OpType.False;
 958                         var methods = MemberCache.GetUserOperator (e.type, op, false);
 959                         if (methods == null)
 960                                 return null;
 961
 962                         Arguments arguments = new Arguments (1);
 963                         arguments.Add (new Argument (e));
 964
 965                         var res = new OverloadResolver (methods, OverloadResolver.Restrictions.BaseMembersIncluded | OverloadResolver.Restrictions.NoBaseMembers, loc);
 966                         var oper = res.ResolveOperator (ec, ref arguments);
 967
 968                         if (oper == null)
 969                                 return null;
 970
 971                         return new UserOperatorCall (oper, arguments, null, loc);
 972                 }
 973
 974                 public virtual string ExprClassName
 975                 {
 976                         get {
 977                                 switch (eclass){
 978                                 case ExprClass.Unresolved:
 979                                         return "Unresolved";
 980                                 case ExprClass.Value:
 981                                         return "value";
 982                                 case ExprClass.Variable:
 983                                         return "variable";
 984                                 case ExprClass.Namespace:
 985                                         return "namespace";
 986                                 case ExprClass.Type:
 987                                         return "type";
 988                                 case ExprClass.MethodGroup:
 989                                         return "method group";
 990                                 case ExprClass.PropertyAccess:
 991                                         return "property access";
 992                                 case ExprClass.EventAccess:
 993                                         return "event access";
 994                                 case ExprClass.IndexerAccess:
 995                                         return "indexer access";
 996                                 case ExprClass.Nothing:
 997                                         return "null";
 998                                 case ExprClass.TypeParameter:
 999                                         return "type parameter";
1000                                 }
1001                                 throw new Exception ("Should not happen");
1002                         }
1003                 }
1004
1005                 /// <summary>
1006                 ///   Reports that we were expecting `expr' to be of class `expected'
1007                 /// </summary>
1008                 public static void Error_UnexpectedKind (IMemberContext ctx, Expression memberExpr, string expected, string was, Location loc)
1009                 {
1010                         var name = memberExpr.GetSignatureForError ();
1011
1012                         ctx.Module.Compiler.Report.Error (118, loc, "`{0}' is a `{1}' but a `{2}' was expected", name, was, expected);
1013                 }
1014
1015                 public virtual void Error_UnexpectedKind (ResolveContext ec, ResolveFlags flags, Location loc)
1016                 {
1017                         string [] valid = new string [4];
1018                         int count = 0;
1019
1020                         if ((flags & ResolveFlags.VariableOrValue) != 0) {
1021                                 valid [count++] = "variable";
1022                                 valid [count++] = "value";
1023                         }
1024
1025                         if ((flags & ResolveFlags.Type) != 0)
1026                                 valid [count++] = "type";
1027
1028                         if ((flags & ResolveFlags.MethodGroup) != 0)
1029                                 valid [count++] = "method group";
1030
1031                         if (count == 0)
1032                                 valid [count++] = "unknown";
1033
1034                         StringBuilder sb = new StringBuilder (valid [0]);
1035                         for (int i = 1; i < count - 1; i++) {
1036                                 sb.Append ("', `");
1037                                 sb.Append (valid [i]);
1038                         }
1039                         if (count > 1) {
1040                                 sb.Append ("' or `");
1041                                 sb.Append (valid [count - 1]);
1042                         }
1043
1044                         ec.Report.Error (119, loc,
1045                                 "Expression denotes a `{0}', where a `{1}' was expected", ExprClassName, sb.ToString ());
1046                 }
1047
1048                 public static void UnsafeError (ResolveContext ec, Location loc)
1049                 {
1050                         UnsafeError (ec.Report, loc);
1051                 }
1052
1053                 public static void UnsafeError (Report Report, Location loc)
1054                 {
1055                         Report.Error (214, loc, "Pointers and fixed size buffers may only be used in an unsafe context");
1056                 }
1057
1058                 //
1059                 // Converts `source' to an int, uint, long or ulong.
1060                 //
1061                 protected Expression ConvertExpressionToArrayIndex (ResolveContext ec, Expression source, bool pointerArray = false)
1062                 {
1063                         var btypes = ec.BuiltinTypes;
1064
1065                         if (source.type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
1066                                 Arguments args = new Arguments (1);
1067                                 args.Add (new Argument (source));
1068                                 return new DynamicConversion (btypes.Int, CSharpBinderFlags.ConvertArrayIndex, args, loc).Resolve (ec);
1069                         }
1070
1071                         Expression converted;
1072
1073                         using (ec.Set (ResolveContext.Options.CheckedScope)) {
1074                                 converted = Convert.ImplicitConversion (ec, source, btypes.Int, source.loc);
1075                                 if (converted == null)
1076                                         converted = Convert.ImplicitConversion (ec, source, btypes.UInt, source.loc);
1077                                 if (converted == null)
1078                                         converted = Convert.ImplicitConversion (ec, source, btypes.Long, source.loc);
1079                                 if (converted == null)
1080                                         converted = Convert.ImplicitConversion (ec, source, btypes.ULong, source.loc);
1081
1082                                 if (converted == null) {
1083                                         source.Error_ValueCannotBeConverted (ec, btypes.Int, false);
1084                                         return null;
1085                                 }
1086                         }
1087
1088                         if (pointerArray)
1089                                 return converted;
1090
1091                         //
1092                         // Only positive constants are allowed at compile time
1093                         //
1094                         Constant c = converted as Constant;
1095                         if (c != null && c.IsNegative)
1096                                 Error_NegativeArrayIndex (ec, source.loc);
1097
1098                         // No conversion needed to array index
1099                         if (converted.Type.BuiltinType == BuiltinTypeSpec.Type.Int)
1100                                 return converted;
1101
1102                         return new ArrayIndexCast (converted, btypes.Int).Resolve (ec);
1103                 }
1104
1105                 //
1106                 // Derived classes implement this method by cloning the fields that
1107                 // could become altered during the Resolve stage
1108                 //
1109                 // Only expressions that are created for the parser need to implement
1110                 // this.
1111                 //
1112                 protected virtual void CloneTo (CloneContext clonectx, Expression target)
1113                 {
1114                         throw new NotImplementedException (
1115                                 String.Format (
1116                                         "CloneTo not implemented for expression {0}", this.GetType ()));
1117                 }
1118
1119                 //
1120                 // Clones an expression created by the parser.
1121                 //
1122                 // We only support expressions created by the parser so far, not
1123                 // expressions that have been resolved (many more classes would need
1124                 // to implement CloneTo).
1125                 //
1126                 // This infrastructure is here merely for Lambda expressions which
1127                 // compile the same code using different type values for the same
1128                 // arguments to find the correct overload
1129                 //
1130                 public virtual Expression Clone (CloneContext clonectx)
1131                 {
1132                         Expression cloned = (Expression) MemberwiseClone ();
1133                         CloneTo (clonectx, cloned);
1134
1135                         return cloned;
1136                 }
1137
1138                 //
1139                 // Implementation of expression to expression tree conversion
1140                 //
1141                 public abstract Expression CreateExpressionTree (ResolveContext ec);
1142
1143                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, Arguments args)
1144                 {
1145                         return CreateExpressionFactoryCall (ec, name, null, args, loc);
1146                 }
1147
1148                 protected Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args)
1149                 {
1150                         return CreateExpressionFactoryCall (ec, name, typeArguments, args, loc);
1151                 }
1152
1153                 public static Expression CreateExpressionFactoryCall (ResolveContext ec, string name, TypeArguments typeArguments, Arguments args, Location loc)
1154                 {
1155                         return new Invocation (new MemberAccess (CreateExpressionTypeExpression (ec, loc), name, typeArguments, loc), args);
1156                 }
1157
1158                 protected static TypeExpr CreateExpressionTypeExpression (ResolveContext ec, Location loc)
1159                 {
1160                         var t = ec.Module.PredefinedTypes.Expression.Resolve ();
1161                         if (t == null)
1162                                 return null;
1163
1164                         return new TypeExpression (t, loc);
1165                 }
1166
1167                 //
1168                 // Implemented by all expressions which support conversion from
1169                 // compiler expression to invokable runtime expression. Used by
1170                 // dynamic C# binder.
1171                 //
1172                 public virtual SLE.Expression MakeExpression (BuilderContext ctx)
1173                 {
1174                         throw new NotImplementedException ("MakeExpression for " + GetType ());
1175                 }
1176
1177                 public virtual object Accept (StructuralVisitor visitor)
1178                 {
1179                         return visitor.Visit (this);
1180                 }
1181         }
1182
1183         /// <summary>
1184         ///   This is just a base class for expressions that can
1185         ///   appear on statements (invocations, object creation,
1186         ///   assignments, post/pre increment and decrement).  The idea
1187         ///   being that they would support an extra Emition interface that
1188         ///   does not leave a result on the stack.
1189         /// </summary>
1190         public abstract class ExpressionStatement : Expression
1191         {
1192                 public virtual void MarkReachable (Reachability rc)
1193                 {
1194                 }
1195
1196                 public ExpressionStatement ResolveStatement (BlockContext ec)
1197                 {
1198                         Expression e = Resolve (ec);
1199                         if (e == null)
1200                                 return null;
1201
1202                         ExpressionStatement es = e as ExpressionStatement;
1203                         if (es == null || e is AnonymousMethodBody)
1204                                 Error_InvalidExpressionStatement (ec);
1205
1206                         //
1207                         // This is quite expensive warning, try to limit the damage
1208                         //
1209                         if (MemberAccess.IsValidDotExpression (e.Type) && !(e is Assign || e is Await)) {
1210                                 WarningAsyncWithoutWait (ec, e);
1211                         }
1212
1213                         return es;
1214                 }
1215
1216                 static void WarningAsyncWithoutWait (BlockContext bc, Expression e)
1217                 {
1218                         if (bc.CurrentAnonymousMethod is AsyncInitializer) {
1219                                 var awaiter = new AwaitStatement.AwaitableMemberAccess (e) {
1220                                         ProbingMode = true
1221                                 };
1222
1223                                 //
1224                                 // Need to do full resolve because GetAwaiter can be extension method
1225                                 // available only in this context
1226                                 //
1227                                 var mg = awaiter.Resolve (bc) as MethodGroupExpr;
1228                                 if (mg == null)
1229                                         return;
1230
1231                                 var arguments = new Arguments (0);
1232                                 mg = mg.OverloadResolve (bc, ref arguments, null, OverloadResolver.Restrictions.ProbingOnly);
1233                                 if (mg == null)
1234                                         return;
1235
1236                                 //
1237                                 // Use same check rules as for real await
1238                                 //
1239                                 var awaiter_definition = bc.Module.GetAwaiter (mg.BestCandidateReturnType);
1240                                 if (!awaiter_definition.IsValidPattern || !awaiter_definition.INotifyCompletion)
1241                                         return;
1242
1243                                 bc.Report.Warning (4014, 1, e.Location,
1244                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator");
1245                                 return;
1246                         }
1247
1248                         var inv = e as Invocation;
1249                         if (inv != null && inv.MethodGroup != null && inv.MethodGroup.BestCandidate.IsAsync) {
1250                                 // The warning won't be reported for imported methods to maintain warning compatiblity with csc
1251                                 bc.Report.Warning (4014, 1, e.Location,
1252                                         "The statement is not awaited and execution of current method continues before the call is completed. Consider using `await' operator or calling `Wait' method");
1253                                 return;
1254                         }
1255                 }
1256
1257                 /// <summary>
1258                 ///   Requests the expression to be emitted in a `statement'
1259                 ///   context.  This means that no new value is left on the
1260                 ///   stack after invoking this method (constrasted with
1261                 ///   Emit that will always leave a value on the stack).
1262                 /// </summary>
1263                 public abstract void EmitStatement (EmitContext ec);
1264
1265                 public override void EmitSideEffect (EmitContext ec)
1266                 {
1267                         EmitStatement (ec);
1268                 }
1269         }
1270
1271         /// <summary>
1272         ///   This kind of cast is used to encapsulate the child
1273         ///   whose type is child.Type into an expression that is
1274         ///   reported to return "return_type".  This is used to encapsulate
1275         ///   expressions which have compatible types, but need to be dealt
1276         ///   at higher levels with.
1277         ///
1278         ///   For example, a "byte" expression could be encapsulated in one
1279         ///   of these as an "unsigned int".  The type for the expression
1280         ///   would be "unsigned int".
1281         ///
1282         /// </summary>
1283         public abstract class TypeCast : Expression
1284         {
1285                 protected readonly Expression child;
1286
1287                 protected TypeCast (Expression child, TypeSpec return_type)
1288                 {
1289                         eclass = child.eclass;
1290                         loc = child.Location;
1291                         type = return_type;
1292                         this.child = child;
1293                 }
1294
1295                 public Expression Child {
1296                         get {
1297                                 return child;
1298                         }
1299                 }
1300
1301                 public override bool ContainsEmitWithAwait ()
1302                 {
1303                         return child.ContainsEmitWithAwait ();
1304                 }
1305
1306                 public override Expression CreateExpressionTree (ResolveContext ec)
1307                 {
1308                         Arguments args = new Arguments (2);
1309                         args.Add (new Argument (child.CreateExpressionTree (ec)));
1310                         args.Add (new Argument (new TypeOf (type, loc)));
1311
1312                         if (type.IsPointer || child.Type.IsPointer)
1313                                 Error_PointerInsideExpressionTree (ec);
1314
1315                         return CreateExpressionFactoryCall (ec, ec.HasSet (ResolveContext.Options.CheckedScope) ? "ConvertChecked" : "Convert", args);
1316                 }
1317
1318                 protected override Expression DoResolve (ResolveContext ec)
1319                 {
1320                         // This should never be invoked, we are born in fully
1321                         // initialized state.
1322
1323                         return this;
1324                 }
1325
1326                 public override void Emit (EmitContext ec)
1327                 {
1328                         child.Emit (ec);
1329                 }
1330
1331                 public override void FlowAnalysis (FlowAnalysisContext fc)
1332                 {
1333                         child.FlowAnalysis (fc);
1334                 }
1335
1336                 public override SLE.Expression MakeExpression (BuilderContext ctx)
1337                 {
1338 #if STATIC
1339                         return base.MakeExpression (ctx);
1340 #else
1341                         return ctx.HasSet (BuilderContext.Options.CheckedScope) ?
1342                                 SLE.Expression.ConvertChecked (child.MakeExpression (ctx), type.GetMetaInfo ()) :
1343                                 SLE.Expression.Convert (child.MakeExpression (ctx), type.GetMetaInfo ());
1344 #endif
1345                 }
1346
1347                 protected override void CloneTo (CloneContext clonectx, Expression t)
1348                 {
1349                         // Nothing to clone
1350                 }
1351
1352                 public override bool IsNull {
1353                         get { return child.IsNull; }
1354                 }
1355         }
1356
1357         public class EmptyCast : TypeCast {
1358                 EmptyCast (Expression child, TypeSpec target_type)
1359                         : base (child, target_type)
1360                 {
1361                 }
1362
1363                 public static Expression Create (Expression child, TypeSpec type)
1364                 {
1365                         Constant c = child as Constant;
1366                         if (c != null) {
1367                                 var enum_constant = c as EnumConstant;
1368                                 if (enum_constant != null)
1369                                         c = enum_constant.Child;
1370
1371                                 if (!(c is ReducedExpression.ReducedConstantExpression)) {
1372                                         if (c.Type == type)
1373                                                 return c;
1374
1375                                         var res = c.ConvertImplicitly (type);
1376                                         if (res != null)
1377                                                 return res;
1378                                 }
1379                         }
1380
1381                         EmptyCast e = child as EmptyCast;
1382                         if (e != null)
1383                                 return new EmptyCast (e.child, type);
1384
1385                         return new EmptyCast (child, type);
1386                 }
1387
1388                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1389                 {
1390                         child.EmitBranchable (ec, label, on_true);
1391                 }
1392
1393                 public override void EmitSideEffect (EmitContext ec)
1394                 {
1395                         child.EmitSideEffect (ec);
1396                 }
1397         }
1398
1399         //
1400         // Used for predefined type user operator (no obsolete check, etc.)
1401         //
1402         public class OperatorCast : TypeCast
1403         {
1404                 readonly MethodSpec conversion_operator;
1405
1406                 public OperatorCast (Expression expr, TypeSpec target_type)
1407                         : this (expr, target_type, target_type, false)
1408                 {
1409                 }
1410
1411                 public OperatorCast (Expression expr, TypeSpec target_type, bool find_explicit)
1412                         : this (expr, target_type, target_type, find_explicit)
1413                 {
1414                 }
1415
1416                 public OperatorCast (Expression expr, TypeSpec declaringType, TypeSpec returnType, bool isExplicit)
1417                         : base (expr, returnType)
1418                 {
1419                         var op = isExplicit ? Operator.OpType.Explicit : Operator.OpType.Implicit;
1420                         var mi = MemberCache.GetUserOperator (declaringType, op, true);
1421
1422                         if (mi != null) {
1423                                 foreach (MethodSpec oper in mi) {
1424                                         if (oper.ReturnType != returnType)
1425                                                 continue;
1426
1427                                         if (oper.Parameters.Types[0] == expr.Type) {
1428                                                 conversion_operator = oper;
1429                                                 return;
1430                                         }
1431                                 }
1432                         }
1433
1434                         throw new InternalErrorException ("Missing predefined user operator between `{0}' and `{1}'",
1435                                 returnType.GetSignatureForError (), expr.Type.GetSignatureForError ());
1436                 }
1437
1438                 public override void Emit (EmitContext ec)
1439                 {
1440                         child.Emit (ec);
1441                         ec.Emit (OpCodes.Call, conversion_operator);
1442                 }
1443         }
1444
1445         //
1446         // Constant specialization of EmptyCast.
1447         // We need to special case this since an empty cast of
1448         // a constant is still a constant.
1449         //
1450         public class EmptyConstantCast : Constant
1451         {
1452                 public readonly Constant child;
1453
1454                 public EmptyConstantCast (Constant child, TypeSpec type)
1455                         : base (child.Location)
1456                 {
1457                         if (child == null)
1458                                 throw new ArgumentNullException ("child");
1459
1460                         this.child = child;
1461                         this.eclass = child.eclass;
1462                         this.type = type;
1463                 }
1464
1465                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1466                 {
1467                         if (child.Type == target_type)
1468                                 return child;
1469
1470                         // FIXME: check that 'type' can be converted to 'target_type' first
1471                         return child.ConvertExplicitly (in_checked_context, target_type);
1472                 }
1473
1474                 public override Expression CreateExpressionTree (ResolveContext ec)
1475                 {
1476                         Arguments args = Arguments.CreateForExpressionTree (ec, null,
1477                                 child.CreateExpressionTree (ec),
1478                                 new TypeOf (type, loc));
1479
1480                         if (type.IsPointer)
1481                                 Error_PointerInsideExpressionTree (ec);
1482
1483                         return CreateExpressionFactoryCall (ec, "Convert", args);
1484                 }
1485
1486                 public override bool IsDefaultValue {
1487                         get { return child.IsDefaultValue; }
1488                 }
1489
1490                 public override bool IsNegative {
1491                         get { return child.IsNegative; }
1492                 }
1493
1494                 public override bool IsNull {
1495                         get { return child.IsNull; }
1496                 }
1497
1498                 public override bool IsOneInteger {
1499                         get { return child.IsOneInteger; }
1500                 }
1501
1502                 public override bool IsSideEffectFree {
1503                         get {
1504                                 return child.IsSideEffectFree;
1505                         }
1506                 }
1507
1508                 public override bool IsZeroInteger {
1509                         get { return child.IsZeroInteger; }
1510                 }
1511
1512                 public override void Emit (EmitContext ec)
1513                 {
1514                         child.Emit (ec);
1515                 }
1516
1517                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1518                 {
1519                         child.EmitBranchable (ec, label, on_true);
1520
1521                         // Only to make verifier happy
1522                         if (TypeManager.IsGenericParameter (type) && child.IsNull)
1523                                 ec.Emit (OpCodes.Unbox_Any, type);
1524                 }
1525
1526                 public override void EmitSideEffect (EmitContext ec)
1527                 {
1528                         child.EmitSideEffect (ec);
1529                 }
1530
1531                 public override object GetValue ()
1532                 {
1533                         return child.GetValue ();
1534                 }
1535
1536                 public override string GetValueAsLiteral ()
1537                 {
1538                         return child.GetValueAsLiteral ();
1539                 }
1540
1541                 public override long GetValueAsLong ()
1542                 {
1543                         return child.GetValueAsLong ();
1544                 }
1545
1546                 public override Constant ConvertImplicitly (TypeSpec target_type)
1547                 {
1548                         if (type == target_type)
1549                                 return this;
1550
1551                         // FIXME: Do we need to check user conversions?
1552                         if (!Convert.ImplicitStandardConversionExists (this, target_type))
1553                                 return null;
1554
1555                         return child.ConvertImplicitly (target_type);
1556                 }
1557         }
1558
1559         /// <summary>
1560         ///  This class is used to wrap literals which belong inside Enums
1561         /// </summary>
1562         public class EnumConstant : Constant
1563         {
1564                 public Constant Child;
1565
1566                 public EnumConstant (Constant child, TypeSpec enum_type)
1567                         : base (child.Location)
1568                 {
1569                         this.Child = child;
1570
1571                         this.eclass = ExprClass.Value;
1572                         this.type = enum_type;
1573                 }
1574
1575                 protected EnumConstant (Location loc)
1576                         : base (loc)
1577                 {
1578                 }
1579
1580                 public override void Emit (EmitContext ec)
1581                 {
1582                         Child.Emit (ec);
1583                 }
1584
1585                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1586                 {
1587                         Child.EncodeAttributeValue (rc, enc, Child.Type);
1588                 }
1589
1590                 public override void EmitBranchable (EmitContext ec, Label label, bool on_true)
1591                 {
1592                         Child.EmitBranchable (ec, label, on_true);
1593                 }
1594
1595                 public override void EmitSideEffect (EmitContext ec)
1596                 {
1597                         Child.EmitSideEffect (ec);
1598                 }
1599
1600                 public override string GetSignatureForError()
1601                 {
1602                         return Type.GetSignatureForError ();
1603                 }
1604
1605                 public override object GetValue ()
1606                 {
1607                         return Child.GetValue ();
1608                 }
1609
1610 #if !STATIC
1611                 public override object GetTypedValue ()
1612                 {
1613                         //
1614                         // The method can be used in dynamic context only (on closed types)
1615                         //
1616                         // System.Enum.ToObject cannot be called on dynamic types
1617                         // EnumBuilder has to be used, but we cannot use EnumBuilder
1618                         // because it does not properly support generics
1619                         //
1620                         return System.Enum.ToObject (type.GetMetaInfo (), Child.GetValue ());
1621                 }
1622 #endif
1623
1624                 public override string GetValueAsLiteral ()
1625                 {
1626                         return Child.GetValueAsLiteral ();
1627                 }
1628
1629                 public override long GetValueAsLong ()
1630                 {
1631                         return Child.GetValueAsLong ();
1632                 }
1633
1634                 public EnumConstant Increment()
1635                 {
1636                         return new EnumConstant (((IntegralConstant) Child).Increment (), type);
1637                 }
1638
1639                 public override bool IsDefaultValue {
1640                         get {
1641                                 return Child.IsDefaultValue;
1642                         }
1643                 }
1644
1645                 public override bool IsSideEffectFree {
1646                         get {
1647                                 return Child.IsSideEffectFree;
1648                         }
1649                 }
1650
1651                 public override bool IsZeroInteger {
1652                         get { return Child.IsZeroInteger; }
1653                 }
1654
1655                 public override bool IsNegative {
1656                         get {
1657                                 return Child.IsNegative;
1658                         }
1659                 }
1660
1661                 public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
1662                 {
1663                         if (Child.Type == target_type)
1664                                 return Child;
1665
1666                         return Child.ConvertExplicitly (in_checked_context, target_type);
1667                 }
1668
1669                 public override Constant ConvertImplicitly (TypeSpec type)
1670                 {
1671                         if (this.type == type) {
1672                                 return this;
1673                         }
1674
1675                         if (!Convert.ImplicitStandardConversionExists (this, type)){
1676                                 return null;
1677                         }
1678
1679                         return Child.ConvertImplicitly (type);
1680                 }
1681         }
1682
1683         /// <summary>
1684         ///   This kind of cast is used to encapsulate Value Types in objects.
1685         ///
1686         ///   The effect of it is to box the value type emitted by the previous
1687         ///   operation.
1688         /// </summary>
1689         public class BoxedCast : TypeCast {
1690
1691                 public BoxedCast (Expression expr, TypeSpec target_type)
1692                         : base (expr, target_type)
1693                 {
1694                         eclass = ExprClass.Value;
1695                 }
1696
1697                 protected override Expression DoResolve (ResolveContext ec)
1698                 {
1699                         // This should never be invoked, we are born in fully
1700                         // initialized state.
1701
1702                         return this;
1703                 }
1704
1705                 public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
1706                 {
1707                         // Only boxing to object type is supported
1708                         if (targetType.BuiltinType != BuiltinTypeSpec.Type.Object) {
1709                                 base.EncodeAttributeValue (rc, enc, targetType);
1710                                 return;
1711                         }
1712
1713                         enc.Encode (child.Type);
1714                         child.EncodeAttributeValue (rc, enc, child.Type);
1715                 }
1716
1717                 public override void Emit (EmitContext ec)
1718                 {
1719                         base.Emit (ec);
1720
1721                         ec.Emit (OpCodes.Box, child.Type);
1722                 }
1723
1724                 public override void EmitSideEffect (EmitContext ec)
1725                 {
1726                         // boxing is side-effectful, since it involves runtime checks, except when boxing to Object or ValueType
1727                         // so, we need to emit the box+pop instructions in most cases
1728                         if (child.Type.IsStruct &&
1729                             (type.BuiltinType == BuiltinTypeSpec.Type.Object || type.BuiltinType == BuiltinTypeSpec.Type.ValueType))
1730                                 child.EmitSideEffect (ec);
1731                         else
1732                                 base.EmitSideEffect (ec);
1733                 }
1734         }
1735
1736         public class UnboxCast : TypeCast {
1737                 public UnboxCast (Expression expr, TypeSpec return_type)
1738                         : base (expr, return_type)
1739                 {
1740                 }
1741
1742                 protected override Expression DoResolve (ResolveContext ec)
1743                 {
1744                         // This should never be invoked, we are born in fully
1745                         // initialized state.
1746
1747                         return this;
1748                 }
1749
1750                 public override void Emit (EmitContext ec)
1751                 {
1752                         base.Emit (ec);
1753
1754                         ec.Emit (OpCodes.Unbox_Any, type);
1755                 }
1756         }
1757
1758         /// <summary>
1759         ///   This is used to perform explicit numeric conversions.
1760         ///
1761         ///   Explicit numeric conversions might trigger exceptions in a checked
1762         ///   context, so they should generate the conv.ovf opcodes instead of
1763         ///   conv opcodes.
1764         /// </summary>
1765         public class ConvCast : TypeCast {
1766                 public enum Mode : byte {
1767                         I1_U1, I1_U2, I1_U4, I1_U8, I1_CH,
1768                         U1_I1, U1_CH,
1769                         I2_I1, I2_U1, I2_U2, I2_U4, I2_U8, I2_CH,
1770                         U2_I1, U2_U1, U2_I2, U2_CH,
1771                         I4_I1, I4_U1, I4_I2, I4_U2, I4_U4, I4_U8, I4_CH,
1772                         U4_I1, U4_U1, U4_I2, U4_U2, U4_I4, U4_CH,
1773                         I8_I1, I8_U1, I8_I2, I8_U2, I8_I4, I8_U4, I8_U8, I8_CH, I8_I,
1774                         U8_I1, U8_U1, U8_I2, U8_U2, U8_I4, U8_U4, U8_I8, U8_CH, U8_I,
1775                         CH_I1, CH_U1, CH_I2,
1776                         R4_I1, R4_U1, R4_I2, R4_U2, R4_I4, R4_U4, R4_I8, R4_U8, R4_CH,
1777                         R8_I1, R8_U1, R8_I2, R8_U2, R8_I4, R8_U4, R8_I8, R8_U8, R8_CH, R8_R4,
1778                         I_I8,
1779                 }
1780
1781                 Mode mode;
1782
1783                 public ConvCast (Expression child, TypeSpec return_type, Mode m)
1784                         : base (child, return_type)
1785                 {
1786                         mode = m;
1787                 }
1788
1789                 protected override Expression DoResolve (ResolveContext ec)
1790                 {
1791                         // This should never be invoked, we are born in fully
1792                         // initialized state.
1793
1794                         return this;
1795                 }
1796
1797                 public override string ToString ()
1798                 {
1799                         return String.Format ("ConvCast ({0}, {1})", mode, child);
1800                 }
1801
1802                 public override void Emit (EmitContext ec)
1803                 {
1804                         base.Emit (ec);
1805                         Emit (ec, mode);
1806                 }
1807
1808                 public static void Emit (EmitContext ec, Mode mode)
1809                 {
1810                         if (ec.HasSet (EmitContext.Options.CheckedScope)) {
1811                                 switch (mode){
1812                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1813                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1814                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1815                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1816                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1817
1818                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1819                                 case Mode.U1_CH: /* nothing */ break;
1820
1821                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1822                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1823                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1824                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1825                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1826                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1827
1828                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1829                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1830                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1831                                 case Mode.U2_CH: /* nothing */ break;
1832
1833                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1834                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1835                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1836                                 case Mode.I4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1837                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1838                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1839                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1840
1841                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1842                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1843                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1844                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1845                                 case Mode.U4_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1846                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1847
1848                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1849                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1850                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1851                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1852                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1853                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1854                                 case Mode.I8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1855                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1856                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_Ovf_U); break;
1857
1858                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1859                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1860                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1861                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1862                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_Ovf_I4_Un); break;
1863                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_Ovf_U4_Un); break;
1864                                 case Mode.U8_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1865                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_Ovf_U2_Un); break;
1866                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_Ovf_U_Un); break;
1867
1868                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_Ovf_I1_Un); break;
1869                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_Ovf_U1_Un); break;
1870                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_Ovf_I2_Un); break;
1871
1872                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1873                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1874                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1875                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1876                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1877                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1878                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1879                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1880                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1881
1882                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_Ovf_I1); break;
1883                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_Ovf_U1); break;
1884                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_Ovf_I2); break;
1885                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1886                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_Ovf_I4); break;
1887                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_Ovf_U4); break;
1888                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_Ovf_I8); break;
1889                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_Ovf_U8); break;
1890                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_Ovf_U2); break;
1891                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1892
1893                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_Ovf_I8_Un); break;
1894                                 }
1895                         } else {
1896                                 switch (mode){
1897                                 case Mode.I1_U1: ec.Emit (OpCodes.Conv_U1); break;
1898                                 case Mode.I1_U2: ec.Emit (OpCodes.Conv_U2); break;
1899                                 case Mode.I1_U4: ec.Emit (OpCodes.Conv_U4); break;
1900                                 case Mode.I1_U8: ec.Emit (OpCodes.Conv_I8); break;
1901                                 case Mode.I1_CH: ec.Emit (OpCodes.Conv_U2); break;
1902
1903                                 case Mode.U1_I1: ec.Emit (OpCodes.Conv_I1); break;
1904                                 case Mode.U1_CH: ec.Emit (OpCodes.Conv_U2); break;
1905
1906                                 case Mode.I2_I1: ec.Emit (OpCodes.Conv_I1); break;
1907                                 case Mode.I2_U1: ec.Emit (OpCodes.Conv_U1); break;
1908                                 case Mode.I2_U2: ec.Emit (OpCodes.Conv_U2); break;
1909                                 case Mode.I2_U4: ec.Emit (OpCodes.Conv_U4); break;
1910                                 case Mode.I2_U8: ec.Emit (OpCodes.Conv_I8); break;
1911                                 case Mode.I2_CH: ec.Emit (OpCodes.Conv_U2); break;
1912
1913                                 case Mode.U2_I1: ec.Emit (OpCodes.Conv_I1); break;
1914                                 case Mode.U2_U1: ec.Emit (OpCodes.Conv_U1); break;
1915                                 case Mode.U2_I2: ec.Emit (OpCodes.Conv_I2); break;
1916                                 case Mode.U2_CH: /* nothing */ break;
1917
1918                                 case Mode.I4_I1: ec.Emit (OpCodes.Conv_I1); break;
1919                                 case Mode.I4_U1: ec.Emit (OpCodes.Conv_U1); break;
1920                                 case Mode.I4_I2: ec.Emit (OpCodes.Conv_I2); break;
1921                                 case Mode.I4_U4: /* nothing */ break;
1922                                 case Mode.I4_U2: ec.Emit (OpCodes.Conv_U2); break;
1923                                 case Mode.I4_U8: ec.Emit (OpCodes.Conv_I8); break;
1924                                 case Mode.I4_CH: ec.Emit (OpCodes.Conv_U2); break;
1925
1926                                 case Mode.U4_I1: ec.Emit (OpCodes.Conv_I1); break;
1927                                 case Mode.U4_U1: ec.Emit (OpCodes.Conv_U1); break;
1928                                 case Mode.U4_I2: ec.Emit (OpCodes.Conv_I2); break;
1929                                 case Mode.U4_U2: ec.Emit (OpCodes.Conv_U2); break;
1930                                 case Mode.U4_I4: /* nothing */ break;
1931                                 case Mode.U4_CH: ec.Emit (OpCodes.Conv_U2); break;
1932
1933                                 case Mode.I8_I1: ec.Emit (OpCodes.Conv_I1); break;
1934                                 case Mode.I8_U1: ec.Emit (OpCodes.Conv_U1); break;
1935                                 case Mode.I8_I2: ec.Emit (OpCodes.Conv_I2); break;
1936                                 case Mode.I8_U2: ec.Emit (OpCodes.Conv_U2); break;
1937                                 case Mode.I8_I4: ec.Emit (OpCodes.Conv_I4); break;
1938                                 case Mode.I8_U4: ec.Emit (OpCodes.Conv_U4); break;
1939                                 case Mode.I8_U8: /* nothing */ break;
1940                                 case Mode.I8_CH: ec.Emit (OpCodes.Conv_U2); break;
1941                                 case Mode.I8_I: ec.Emit (OpCodes.Conv_U); break;
1942
1943                                 case Mode.U8_I1: ec.Emit (OpCodes.Conv_I1); break;
1944                                 case Mode.U8_U1: ec.Emit (OpCodes.Conv_U1); break;
1945                                 case Mode.U8_I2: ec.Emit (OpCodes.Conv_I2); break;
1946                                 case Mode.U8_U2: ec.Emit (OpCodes.Conv_U2); break;
1947                                 case Mode.U8_I4: ec.Emit (OpCodes.Conv_I4); break;
1948                                 case Mode.U8_U4: ec.Emit (OpCodes.Conv_U4); break;
1949                                 case Mode.U8_I8: /* nothing */ break;
1950                                 case Mode.U8_CH: ec.Emit (OpCodes.Conv_U2); break;
1951                                 case Mode.U8_I: ec.Emit (OpCodes.Conv_U); break;
1952
1953                                 case Mode.CH_I1: ec.Emit (OpCodes.Conv_I1); break;
1954                                 case Mode.CH_U1: ec.Emit (OpCodes.Conv_U1); break;
1955                                 case Mode.CH_I2: ec.Emit (OpCodes.Conv_I2); break;
1956
1957                                 case Mode.R4_I1: ec.Emit (OpCodes.Conv_I1); break;
1958                                 case Mode.R4_U1: ec.Emit (OpCodes.Conv_U1); break;
1959                                 case Mode.R4_I2: ec.Emit (OpCodes.Conv_I2); break;
1960                                 case Mode.R4_U2: ec.Emit (OpCodes.Conv_U2); break;
1961                                 case Mode.R4_I4: ec.Emit (OpCodes.Conv_I4); break;
1962                                 case Mode.R4_U4: ec.Emit (OpCodes.Conv_U4); break;
1963                                 case Mode.R4_I8: ec.Emit (OpCodes.Conv_I8); break;
1964                                 case Mode.R4_U8: ec.Emit (OpCodes.Conv_U8); break;
1965                                 case Mode.R4_CH: ec.Emit (OpCodes.Conv_U2); break;
1966
1967                                 case Mode.R8_I1: ec.Emit (OpCodes.Conv_I1); break;
1968                                 case Mode.R8_U1: ec.Emit (OpCodes.Conv_U1); break;
1969                                 case Mode.R8_I2: ec.Emit (OpCodes.Conv_I2); break;
1970                                 case Mode.R8_U2: ec.Emit (OpCodes.Conv_U2); break;
1971                                 case Mode.R8_I4: ec.Emit (OpCodes.Conv_I4); break;
1972                                 case Mode.R8_U4: ec.Emit (OpCodes.Conv_U4); break;
1973                                 case Mode.R8_I8: ec.Emit (OpCodes.Conv_I8); break;
1974                                 case Mode.R8_U8: ec.Emit (OpCodes.Conv_U8); break;
1975                                 case Mode.R8_CH: ec.Emit (OpCodes.Conv_U2); break;
1976                                 case Mode.R8_R4: ec.Emit (OpCodes.Conv_R4); break;
1977
1978                                 case Mode.I_I8: ec.Emit (OpCodes.Conv_U8); break;
1979                                 }
1980                         }
1981                 }
1982         }
1983
1984         class OpcodeCast : TypeCast
1985         {
1986                 readonly OpCode op;
1987
1988                 public OpcodeCast (Expression child, TypeSpec return_type, OpCode op)
1989                         : base (child, return_type)
1990                 {
1991                         this.op = op;
1992                 }
1993
1994                 protected override Expression DoResolve (ResolveContext ec)
1995                 {
1996                         // This should never be invoked, we are born in fully
1997                         // initialized state.
1998
1999                         return this;
2000                 }
2001
2002                 public override void Emit (EmitContext ec)
2003                 {
2004                         base.Emit (ec);
2005                         ec.Emit (op);
2006                 }
2007
2008                 public TypeSpec UnderlyingType {
2009                         get { return child.Type; }
2010                 }
2011         }
2012
2013         //
2014         // Opcode casts expression with 2 opcodes but only
2015         // single expression tree node
2016         //
2017         class OpcodeCastDuplex : OpcodeCast
2018         {
2019                 readonly OpCode second;
2020
2021                 public OpcodeCastDuplex (Expression child, TypeSpec returnType, OpCode first, OpCode second)
2022                         : base (child, returnType, first)
2023                 {
2024                         this.second = second;
2025                 }
2026
2027                 public override void Emit (EmitContext ec)
2028                 {
2029                         base.Emit (ec);
2030                         ec.Emit (second);
2031                 }
2032         }
2033
2034         /// <summary>
2035         ///   This kind of cast is used to encapsulate a child and cast it
2036         ///   to the class requested
2037         /// </summary>
2038         public sealed class ClassCast : TypeCast {
2039                 readonly bool forced;
2040
2041                 public ClassCast (Expression child, TypeSpec return_type)
2042                         : base (child, return_type)
2043                 {
2044                 }
2045
2046                 public ClassCast (Expression child, TypeSpec return_type, bool forced)
2047                         : base (child, return_type)
2048                 {
2049                         this.forced = forced;
2050                 }
2051
2052                 public override void Emit (EmitContext ec)
2053                 {
2054                         base.Emit (ec);
2055
2056                         bool gen = TypeManager.IsGenericParameter (child.Type);
2057                         if (gen)
2058                                 ec.Emit (OpCodes.Box, child.Type);
2059
2060                         if (type.IsGenericParameter) {
2061                                 ec.Emit (OpCodes.Unbox_Any, type);
2062                                 return;
2063                         }
2064
2065                         if (gen && !forced)
2066                                 return;
2067
2068                         ec.Emit (OpCodes.Castclass, type);
2069                 }
2070         }
2071
2072         //
2073         // Created during resolving pahse when an expression is wrapped or constantified
2074         // and original expression can be used later (e.g. for expression trees)
2075         //
2076         public class ReducedExpression : Expression
2077         {
2078                 public sealed class ReducedConstantExpression : EmptyConstantCast
2079                 {
2080                         readonly Expression orig_expr;
2081
2082                         public ReducedConstantExpression (Constant expr, Expression orig_expr)
2083                                 : base (expr, expr.Type)
2084                         {
2085                                 this.orig_expr = orig_expr;
2086                         }
2087
2088                         public Expression OriginalExpression {
2089                                 get {
2090                                         return orig_expr;
2091                                 }
2092                         }
2093
2094                         public override Constant ConvertImplicitly (TypeSpec target_type)
2095                         {
2096                                 Constant c = base.ConvertImplicitly (target_type);
2097                                 if (c != null)
2098                                         c = new ReducedConstantExpression (c, orig_expr);
2099
2100                                 return c;
2101                         }
2102
2103                         public override Expression CreateExpressionTree (ResolveContext ec)
2104                         {
2105                                 return orig_expr.CreateExpressionTree (ec);
2106                         }
2107
2108                         public override Constant ConvertExplicitly (bool in_checked_context, TypeSpec target_type)
2109                         {
2110                                 Constant c = base.ConvertExplicitly (in_checked_context, target_type);
2111                                 if (c != null)
2112                                         c = new ReducedConstantExpression (c, orig_expr);
2113                                 return c;
2114                         }
2115
2116                         public override void EncodeAttributeValue (IMemberContext rc, AttributeEncoder enc, TypeSpec targetType)
2117                         {
2118                                 //
2119                                 // LAMESPEC: Reduced conditional expression is allowed as an attribute argument
2120                                 //
2121                                 if (orig_expr is Conditional)
2122                                         child.EncodeAttributeValue (rc, enc, targetType);
2123                                 else
2124                                         base.EncodeAttributeValue (rc, enc, targetType);
2125                         }
2126                 }
2127
2128                 sealed class ReducedExpressionStatement : ExpressionStatement
2129                 {
2130                         readonly Expression orig_expr;
2131                         readonly ExpressionStatement stm;
2132
2133                         public ReducedExpressionStatement (ExpressionStatement stm, Expression orig)
2134                         {
2135                                 this.orig_expr = orig;
2136                                 this.stm = stm;
2137                                 this.eclass = stm.eclass;
2138                                 this.type = stm.Type;
2139
2140                                 this.loc = orig.Location;
2141                         }
2142
2143                         public override bool ContainsEmitWithAwait ()
2144                         {
2145                                 return stm.ContainsEmitWithAwait ();
2146                         }
2147
2148                         public override Expression CreateExpressionTree (ResolveContext ec)
2149                         {
2150                                 return orig_expr.CreateExpressionTree (ec);
2151                         }
2152
2153                         protected override Expression DoResolve (ResolveContext ec)
2154                         {
2155                                 return this;
2156                         }
2157
2158                         public override void Emit (EmitContext ec)
2159                         {
2160                                 stm.Emit (ec);
2161                         }
2162
2163                         public override void EmitStatement (EmitContext ec)
2164                         {
2165                                 stm.EmitStatement (ec);
2166                         }
2167
2168                         public override void FlowAnalysis (FlowAnalysisContext fc)
2169                         {
2170                                 stm.FlowAnalysis (fc);
2171                         }
2172                 }
2173
2174                 readonly Expression expr, orig_expr;
2175
2176                 private ReducedExpression (Expression expr, Expression orig_expr)
2177                 {
2178                         this.expr = expr;
2179                         this.eclass = expr.eclass;
2180                         this.type = expr.Type;
2181                         this.orig_expr = orig_expr;
2182                         this.loc = orig_expr.Location;
2183                 }
2184
2185                 #region Properties
2186
2187                 public override bool IsSideEffectFree {
2188                         get {
2189                                 return expr.IsSideEffectFree;
2190                         }
2191                 }
2192
2193                 public Expression OriginalExpression {
2194                         get {
2195                                 return orig_expr;
2196                         }
2197                 }
2198
2199                 #endregion
2200
2201                 public override bool ContainsEmitWithAwait ()
2202                 {
2203                         return expr.ContainsEmitWithAwait ();
2204                 }
2205
2206                 //
2207                 // Creates fully resolved expression switcher
2208                 //
2209                 public static Constant Create (Constant expr, Expression original_expr)
2210                 {
2211                         if (expr.eclass == ExprClass.Unresolved)
2212                                 throw new ArgumentException ("Unresolved expression");
2213
2214                         return new ReducedConstantExpression (expr, original_expr);
2215                 }
2216
2217                 public static ExpressionStatement Create (ExpressionStatement s, Expression orig)
2218                 {
2219                         return new ReducedExpressionStatement (s, orig);
2220                 }
2221
2222                 public static Expression Create (Expression expr, Expression original_expr)
2223                 {
2224                         return Create (expr, original_expr, true);
2225                 }
2226
2227                 //
2228                 // Creates unresolved reduce expression. The original expression has to be
2229                 // already resolved. Created expression is constant based based on `expr'
2230                 // value unless canBeConstant is used
2231                 //
2232                 public static Expression Create (Expression expr, Expression original_expr, bool canBeConstant)
2233                 {
2234                         if (canBeConstant) {
2235                                 Constant c = expr as Constant;
2236                                 if (c != null)
2237                                         return Create (c, original_expr);
2238                         }
2239
2240                         ExpressionStatement s = expr as ExpressionStatement;
2241                         if (s != null)
2242                                 return Create (s, original_expr);
2243
2244                         if (expr.eclass == ExprClass.Unresolved)
2245                                 throw new ArgumentException ("Unresolved expression");
2246
2247                         return new ReducedExpression (expr, original_expr);
2248                 }
2249
2250                 public override Expression CreateExpressionTree (ResolveContext ec)
2251                 {
2252                         return orig_expr.CreateExpressionTree (ec);
2253                 }
2254
2255                 protected override Expression DoResolve (ResolveContext ec)
2256                 {
2257                         return this;
2258                 }
2259
2260                 public override void Emit (EmitContext ec)
2261                 {
2262                         expr.Emit (ec);
2263                 }
2264
2265                 public override Expression EmitToField (EmitContext ec)
2266                 {
2267                         return expr.EmitToField(ec);
2268                 }
2269
2270                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2271                 {
2272                         expr.EmitBranchable (ec, target, on_true);
2273                 }
2274
2275                 public override void FlowAnalysis (FlowAnalysisContext fc)
2276                 {
2277                         expr.FlowAnalysis (fc);
2278                 }
2279
2280                 public override SLE.Expression MakeExpression (BuilderContext ctx)
2281                 {
2282                         return orig_expr.MakeExpression (ctx);
2283                 }
2284         }
2285
2286         //
2287         // Standard composite pattern
2288         //
2289         public abstract class CompositeExpression : Expression
2290         {
2291                 protected Expression expr;
2292
2293                 protected CompositeExpression (Expression expr)
2294                 {
2295                         this.expr = expr;
2296                         this.loc = expr.Location;
2297                 }
2298
2299                 public override bool ContainsEmitWithAwait ()
2300                 {
2301                         return expr.ContainsEmitWithAwait ();
2302                 }
2303
2304                 public override Expression CreateExpressionTree (ResolveContext rc)
2305                 {
2306                         return expr.CreateExpressionTree (rc);
2307                 }
2308
2309                 public Expression Child {
2310                         get { return expr; }
2311                 }
2312
2313                 protected override Expression DoResolve (ResolveContext rc)
2314                 {
2315                         expr = expr.Resolve (rc);
2316                         if (expr != null) {
2317                                 type = expr.Type;
2318                                 eclass = expr.eclass;
2319                         }
2320
2321                         return this;
2322                 }
2323
2324                 public override void Emit (EmitContext ec)
2325                 {
2326                         expr.Emit (ec);
2327                 }
2328
2329                 public override bool IsNull {
2330                         get { return expr.IsNull; }
2331                 }
2332         }
2333
2334         //
2335         // Base of expressions used only to narrow resolve flow
2336         //
2337         public abstract class ShimExpression : Expression
2338         {
2339                 protected Expression expr;
2340
2341                 protected ShimExpression (Expression expr)
2342                 {
2343                         this.expr = expr;
2344                 }
2345
2346                 public Expression Expr {
2347                         get {
2348                                 return expr;
2349                         }
2350                 }
2351
2352                 protected override void CloneTo (CloneContext clonectx, Expression t)
2353                 {
2354                         if (expr == null)
2355                                 return;
2356
2357                         ShimExpression target = (ShimExpression) t;
2358                         target.expr = expr.Clone (clonectx);
2359                 }
2360
2361                 public override bool ContainsEmitWithAwait ()
2362                 {
2363                         return expr.ContainsEmitWithAwait ();
2364                 }
2365
2366                 public override Expression CreateExpressionTree (ResolveContext ec)
2367                 {
2368                         throw new NotSupportedException ("ET");
2369                 }
2370
2371                 public override void Emit (EmitContext ec)
2372                 {
2373                         throw new InternalErrorException ("Missing Resolve call");
2374                 }
2375         }
2376
2377         public class UnreachableExpression : Expression
2378         {
2379                 public UnreachableExpression (Expression expr)
2380                 {
2381                         this.loc = expr.Location;
2382                 }
2383
2384                 public override Expression CreateExpressionTree (ResolveContext ec)
2385                 {
2386                         // TODO: is it ok
2387                         throw new NotImplementedException ();
2388                 }
2389
2390                 protected override Expression DoResolve (ResolveContext rc)
2391                 {
2392                         throw new NotSupportedException ();
2393                 }
2394
2395                 public override void FlowAnalysis (FlowAnalysisContext fc)
2396                 {
2397                         fc.Report.Warning (429, 4, loc, "Unreachable expression code detected");
2398                 }
2399
2400                 public override void Emit (EmitContext ec)
2401                 {
2402                 }
2403
2404                 public override void EmitBranchable (EmitContext ec, Label target, bool on_true)
2405                 {
2406                 }
2407         }
2408
2409         //
2410         // Unresolved type name expressions
2411         //
2412         public abstract class ATypeNameExpression : FullNamedExpression
2413         {
2414                 string name;
2415                 protected TypeArguments targs;
2416
2417                 protected ATypeNameExpression (string name, Location l)
2418                 {
2419                         this.name = name;
2420                         loc = l;
2421                 }
2422
2423                 protected ATypeNameExpression (string name, TypeArguments targs, Location l)
2424                 {
2425                         this.name = name;
2426                         this.targs = targs;
2427                         loc = l;
2428                 }
2429
2430                 protected ATypeNameExpression (string name, int arity, Location l)
2431                         : this (name, new UnboundTypeArguments (arity), l)
2432                 {
2433                 }
2434
2435                 #region Properties
2436
2437                 protected int Arity {
2438                         get {
2439                                 return targs == null ? 0 : targs.Count;
2440                         }
2441                 }
2442
2443                 public bool HasTypeArguments {
2444                         get {
2445                                 return targs != null && !targs.IsEmpty;
2446                         }
2447                 }
2448
2449                 public string Name {
2450                         get {
2451                                 return name;
2452                         }
2453                         set {
2454                                 name = value;
2455                         }
2456                 }
2457
2458                 public TypeArguments TypeArguments {
2459                         get {
2460                                 return targs;
2461                         }
2462                 }
2463
2464                 #endregion
2465
2466                 public override bool Equals (object obj)
2467                 {
2468                         ATypeNameExpression atne = obj as ATypeNameExpression;
2469                         return atne != null && atne.Name == Name &&
2470                                 (targs == null || targs.Equals (atne.targs));
2471                 }
2472
2473                 public override int GetHashCode ()
2474                 {
2475                         return Name.GetHashCode ();
2476                 }
2477
2478                 // TODO: Move it to MemberCore
2479                 public static string GetMemberType (MemberCore mc)
2480                 {
2481                         if (mc is Property)
2482                                 return "property";
2483                         if (mc is Indexer)
2484                                 return "indexer";
2485                         if (mc is FieldBase)
2486                                 return "field";
2487                         if (mc is MethodCore)
2488                                 return "method";
2489                         if (mc is EnumMember)
2490                                 return "enum";
2491                         if (mc is Event)
2492                                 return "event";
2493
2494                         return "type";
2495                 }
2496
2497                 public override string GetSignatureForError ()
2498                 {
2499                         if (targs != null) {
2500                                 return Name + "<" + targs.GetSignatureForError () + ">";
2501                         }
2502
2503                         return Name;
2504                 }
2505
2506                 public abstract Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restriction);
2507         }
2508
2509         /// <summary>
2510         ///   SimpleName expressions are formed of a single word and only happen at the beginning
2511         ///   of a dotted-name.
2512         /// </summary>
2513         public class SimpleName : ATypeNameExpression
2514         {
2515                 public SimpleName (string name, Location l)
2516                         : base (name, l)
2517                 {
2518                 }
2519
2520                 public SimpleName (string name, TypeArguments args, Location l)
2521                         : base (name, args, l)
2522                 {
2523                 }
2524
2525                 public SimpleName (string name, int arity, Location l)
2526                         : base (name, arity, l)
2527                 {
2528                 }
2529
2530                 public SimpleName GetMethodGroup ()
2531                 {
2532                         return new SimpleName (Name, targs, loc);
2533                 }
2534
2535                 protected override Expression DoResolve (ResolveContext rc)
2536                 {
2537                         return SimpleNameResolve (rc, null);
2538                 }
2539
2540                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
2541                 {
2542                         return SimpleNameResolve (ec, right_side);
2543                 }
2544
2545                 protected virtual void Error_TypeOrNamespaceNotFound (IMemberContext ctx)
2546                 {
2547                         if (ctx.CurrentType != null) {
2548                                 var member = MemberLookup (ctx, false, ctx.CurrentType, Name, 0, MemberLookupRestrictions.ExactArity, loc) as MemberExpr;
2549                                 if (member != null) {
2550                                         Error_UnexpectedKind (ctx, member, "type", member.KindName, loc);
2551                                         return;
2552                                 }
2553                         }
2554
2555                         var report = ctx.Module.Compiler.Report;
2556
2557                         var retval = ctx.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2558                         if (retval != null) {
2559                                 report.SymbolRelatedToPreviousError (retval.Type);
2560                                 ErrorIsInaccesible (ctx, retval.GetSignatureForError (), loc);
2561                                 return;
2562                         }
2563
2564                         retval = ctx.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2565                         if (retval != null) {
2566                                 Error_TypeArgumentsCannotBeUsed (ctx, retval.Type, loc);
2567                                 return;
2568                         }
2569
2570                         var ns_candidates = ctx.Module.GlobalRootNamespace.FindTypeNamespaces (ctx, Name, Arity);
2571                         if (ns_candidates != null) {
2572                                 if (ctx is UsingAliasNamespace.AliasContext) {
2573                                         report.Error (246, loc,
2574                                                 "The type or namespace name `{1}' could not be found. Consider using fully qualified name `{0}.{1}'",
2575                                                 ns_candidates[0], Name);
2576                                 } else {
2577                                         string usings = string.Join ("' or `", ns_candidates.ToArray ());
2578                                         report.Error (246, loc,
2579                                                 "The type or namespace name `{0}' could not be found. Are you missing `{1}' using directive?",
2580                                                 Name, usings);
2581                                 }
2582                         } else {
2583                                 report.Error (246, loc,
2584                                         "The type or namespace name `{0}' could not be found. Are you missing an assembly reference?",
2585                                         Name);
2586                         }
2587                 }
2588
2589                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2590                 {
2591                         FullNamedExpression fne = mc.LookupNamespaceOrType (Name, Arity, LookupMode.Normal, loc);
2592
2593                         if (fne != null) {
2594                                 if (fne.Type != null && Arity > 0) {
2595                                         if (HasTypeArguments) {
2596                                                 GenericTypeExpr ct = new GenericTypeExpr (fne.Type, targs, loc);
2597                                                 if (ct.ResolveAsType (mc) == null)
2598                                                         return null;
2599
2600                                                 return ct;
2601                                         }
2602
2603                                         return new GenericOpenTypeExpr (fne.Type, loc);
2604                                 }
2605
2606                                 //
2607                                 // dynamic namespace is ignored when dynamic is allowed (does not apply to types)
2608                                 //
2609                                 if (!(fne is Namespace))
2610                                         return fne;
2611                         }
2612
2613                         if (Arity == 0 && Name == "dynamic" && mc.Module.Compiler.Settings.Version > LanguageVersion.V_3) {
2614                                 if (!mc.Module.PredefinedAttributes.Dynamic.IsDefined) {
2615                                         mc.Module.Compiler.Report.Error (1980, Location,
2616                                                 "Dynamic keyword requires `{0}' to be defined. Are you missing System.Core.dll assembly reference?",
2617                                                 mc.Module.PredefinedAttributes.Dynamic.GetSignatureForError ());
2618                                 }
2619
2620                                 fne = new DynamicTypeExpr (loc);
2621                                 fne.ResolveAsType (mc);
2622                         }
2623
2624                         if (fne != null)
2625                                 return fne;
2626
2627                         Error_TypeOrNamespaceNotFound (mc);
2628                         return null;
2629                 }
2630
2631                 public bool IsPossibleTypeOrNamespace (IMemberContext mc)
2632                 {
2633                         return mc.LookupNamespaceOrType (Name, Arity, LookupMode.Probing, loc) != null;
2634                 }
2635
2636                 public override Expression LookupNameExpression (ResolveContext rc, MemberLookupRestrictions restrictions)
2637                 {
2638                         int lookup_arity = Arity;
2639                         bool errorMode = false;
2640                         Expression e;
2641                         Block current_block = rc.CurrentBlock;
2642                         INamedBlockVariable variable = null;
2643                         bool variable_found = false;
2644
2645                         while (true) {
2646                                 //
2647                                 // Stage 1: binding to local variables or parameters
2648                                 //
2649                                 // LAMESPEC: It should take invocableOnly into account but that would break csc compatibility
2650                                 //
2651                                 if (current_block != null && lookup_arity == 0) {
2652                                         if (current_block.ParametersBlock.TopBlock.GetLocalName (Name, current_block.Original, ref variable)) {
2653                                                 if (!variable.IsDeclared) {
2654                                                         // We found local name in accessible block but it's not
2655                                                         // initialized yet, maybe the user wanted to bind to something else
2656                                                         errorMode = true;
2657                                                         variable_found = true;
2658                                                 } else {
2659                                                         e = variable.CreateReferenceExpression (rc, loc);
2660                                                         if (e != null) {
2661                                                                 if (Arity > 0)
2662                                                                         Error_TypeArgumentsCannotBeUsed (rc, "variable", Name, loc);
2663
2664                                                                 return e;
2665                                                         }
2666                                                 }
2667                                         }
2668                                 }
2669
2670                                 //
2671                                 // Stage 2: Lookup members if we are inside a type up to top level type for nested types
2672                                 //
2673                                 TypeSpec member_type = rc.CurrentType;
2674                                 for (; member_type != null; member_type = member_type.DeclaringType) {
2675                                         e = MemberLookup (rc, errorMode, member_type, Name, lookup_arity, restrictions, loc);
2676                                         if (e == null)
2677                                                 continue;
2678
2679                                         var me = e as MemberExpr;
2680                                         if (me == null) {
2681                                                 // The name matches a type, defer to ResolveAsTypeStep
2682                                                 if (e is TypeExpr)
2683                                                         break;
2684
2685                                                 continue;
2686                                         }
2687
2688                                         if (errorMode) {
2689                                                 if (variable != null) {
2690                                                         if (me is FieldExpr || me is ConstantExpr || me is EventExpr || me is PropertyExpr) {
2691                                                                 rc.Report.Error (844, loc,
2692                                                                         "A local variable `{0}' cannot be used before it is declared. Consider renaming the local variable when it hides the member `{1}'",
2693                                                                         Name, me.GetSignatureForError ());
2694                                                         } else {
2695                                                                 break;
2696                                                         }
2697                                                 } else if (me is MethodGroupExpr || me is PropertyExpr || me is IndexerExpr) {
2698                                                         // Leave it to overload resolution to report correct error
2699                                                 } else {
2700                                                         // TODO: rc.Report.SymbolRelatedToPreviousError ()
2701                                                         ErrorIsInaccesible (rc, me.GetSignatureForError (), loc);
2702                                                 }
2703                                         } else {
2704                                                 // LAMESPEC: again, ignores InvocableOnly
2705                                                 if (variable != null) {
2706                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2707                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2708                                                 }
2709
2710                                                 //
2711                                                 // MemberLookup does not check accessors availability, this is actually needed for properties only
2712                                                 //
2713                                                 var pe = me as PropertyExpr;
2714                                                 if (pe != null) {
2715
2716                                                         // Break as there is no other overload available anyway
2717                                                         if ((restrictions & MemberLookupRestrictions.ReadAccess) != 0) {
2718                                                                 if (!pe.PropertyInfo.HasGet || !pe.PropertyInfo.Get.IsAccessible (rc))
2719                                                                         break;
2720
2721                                                                 pe.Getter = pe.PropertyInfo.Get;
2722                                                         } else {
2723                                                                 if (!pe.PropertyInfo.HasSet || !pe.PropertyInfo.Set.IsAccessible (rc))
2724                                                                         break;
2725
2726                                                                 pe.Setter = pe.PropertyInfo.Set;
2727                                                         }
2728                                                 }
2729                                         }
2730
2731                                         // TODO: It's used by EventExpr -> FieldExpr transformation only
2732                                         // TODO: Should go to MemberAccess
2733                                         me = me.ResolveMemberAccess (rc, null, null);
2734
2735                                         if (Arity > 0) {
2736                                                 targs.Resolve (rc);
2737                                                 me.SetTypeArguments (rc, targs);
2738                                         }
2739
2740                                         return me;
2741                                 }
2742
2743                                 //
2744                                 // Stage 3: Lookup nested types, namespaces and type parameters in the context
2745                                 //
2746                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0 && !variable_found) {
2747                                         if (IsPossibleTypeOrNamespace (rc)) {
2748                                                 if (variable != null) {
2749                                                         rc.Report.SymbolRelatedToPreviousError (variable.Location, Name);
2750                                                         rc.Report.Error (135, loc, "`{0}' conflicts with a declaration in a child block", Name);
2751                                                 }
2752
2753                                                 return ResolveAsTypeOrNamespace (rc);
2754                                         }
2755                                 }
2756
2757                                 if (errorMode) {
2758                                         if (variable_found) {
2759                                                 rc.Report.Error (841, loc, "A local variable `{0}' cannot be used before it is declared", Name);
2760                                         } else {
2761                                                 if (Arity > 0) {
2762                                                         var tparams = rc.CurrentTypeParameters;
2763                                                         if (tparams != null) {
2764                                                                 if (tparams.Find (Name) != null) {
2765                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2766                                                                         return null;
2767                                                                 }
2768                                                         }
2769
2770                                                         var ct = rc.CurrentType;
2771                                                         do {
2772                                                                 if (ct.MemberDefinition.TypeParametersCount > 0) {
2773                                                                         foreach (var ctp in ct.MemberDefinition.TypeParameters) {
2774                                                                                 if (ctp.Name == Name) {
2775                                                                                         Error_TypeArgumentsCannotBeUsed (rc, "type parameter", Name, loc);
2776                                                                                         return null;
2777                                                                                 }
2778                                                                         }
2779                                                                 }
2780
2781                                                                 ct = ct.DeclaringType;
2782                                                         } while (ct != null);
2783                                                 }
2784
2785                                                 if ((restrictions & MemberLookupRestrictions.InvocableOnly) == 0) {
2786                                                         e = rc.LookupNamespaceOrType (Name, Arity, LookupMode.IgnoreAccessibility, loc);
2787                                                         if (e != null) {
2788                                                                 rc.Report.SymbolRelatedToPreviousError (e.Type);
2789                                                                 ErrorIsInaccesible (rc, e.GetSignatureForError (), loc);
2790                                                                 return e;
2791                                                         }
2792                                                 } else {
2793                                                         var me = MemberLookup (rc, false, rc.CurrentType, Name, Arity, restrictions & ~MemberLookupRestrictions.InvocableOnly, loc) as MemberExpr;
2794                                                         if (me != null) {
2795                                                                 Error_UnexpectedKind (rc, me, "method group", me.KindName, loc);
2796                                                                 return ErrorExpression.Instance;
2797                                                         }
2798                                                 }
2799
2800                                                 e = rc.LookupNamespaceOrType (Name, -System.Math.Max (1, Arity), LookupMode.Probing, loc);
2801                                                 if (e != null) {
2802                                                         if (e.Type.Arity != Arity) {
2803                                                                 Error_TypeArgumentsCannotBeUsed (rc, e.Type, loc);
2804                                                                 return e;
2805                                                         }
2806
2807                                                         if (e is TypeExpr) {
2808                                                                 // TypeExpression does not have correct location
2809                                                                 if (e is TypeExpression)
2810                                                                         e = new TypeExpression (e.Type, loc);
2811
2812                                                                 return e;
2813                                                         }
2814                                                 }
2815
2816                                                 rc.Report.Error (103, loc, "The name `{0}' does not exist in the current context", Name);
2817                                         }
2818
2819                                         return ErrorExpression.Instance;
2820                                 }
2821
2822                                 if (rc.Module.Evaluator != null) {
2823                                         var fi = rc.Module.Evaluator.LookupField (Name);
2824                                         if (fi != null)
2825                                                 return new FieldExpr (fi.Item1, loc);
2826                                 }
2827
2828                                 lookup_arity = 0;
2829                                 errorMode = true;
2830                         }
2831                 }
2832
2833                 Expression SimpleNameResolve (ResolveContext ec, Expression right_side)
2834                 {
2835                         Expression e = LookupNameExpression (ec, right_side == null ? MemberLookupRestrictions.ReadAccess : MemberLookupRestrictions.None);
2836
2837                         if (e == null)
2838                                 return null;
2839
2840                         if (e is FullNamedExpression && e.eclass != ExprClass.Unresolved) {
2841                                 Error_UnexpectedKind (ec, e, "variable", e.ExprClassName, loc);
2842                                 return e;
2843                         }
2844
2845                         if (right_side != null) {
2846                                 e = e.ResolveLValue (ec, right_side);
2847                         } else {
2848                                 e = e.Resolve (ec);
2849                         }
2850
2851                         return e;
2852                 }
2853
2854                 public override object Accept (StructuralVisitor visitor)
2855                 {
2856                         return visitor.Visit (this);
2857                 }
2858         }
2859
2860         /// <summary>
2861         ///   Represents a namespace or a type.  The name of the class was inspired by
2862         ///   section 10.8.1 (Fully Qualified Names).
2863         /// </summary>
2864         public abstract class FullNamedExpression : Expression
2865         {
2866                 protected override void CloneTo (CloneContext clonectx, Expression target)
2867                 {
2868                         // Do nothing, most unresolved type expressions cannot be
2869                         // resolved to different type
2870                 }
2871
2872                 public override bool ContainsEmitWithAwait ()
2873                 {
2874                         return false;
2875                 }
2876
2877                 public override Expression CreateExpressionTree (ResolveContext ec)
2878                 {
2879                         throw new NotSupportedException ("ET");
2880                 }
2881
2882                 public abstract FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc);
2883
2884                 //
2885                 // This is used to resolve the expression as a type, a null
2886                 // value will be returned if the expression is not a type
2887                 // reference
2888                 //
2889                 public override TypeSpec ResolveAsType (IMemberContext mc)
2890                 {
2891                         FullNamedExpression fne = ResolveAsTypeOrNamespace (mc);
2892
2893                         if (fne == null)
2894                                 return null;
2895
2896                         TypeExpr te = fne as TypeExpr;
2897                         if (te == null) {
2898                                 Error_UnexpectedKind (mc, fne, "type", fne.ExprClassName, loc);
2899                                 return null;
2900                         }
2901
2902                         te.loc = loc;
2903
2904                         type = te.Type;
2905
2906                         var dep = type.GetMissingDependencies ();
2907                         if (dep != null) {
2908                                 ImportedTypeDefinition.Error_MissingDependency (mc, dep, loc);
2909                         }
2910
2911                         if (type.Kind == MemberKind.Void) {
2912                                 mc.Module.Compiler.Report.Error (673, loc, "System.Void cannot be used from C#. Consider using `void'");
2913                         }
2914
2915                         //
2916                         // Obsolete checks cannot be done when resolving base context as they
2917                         // require type dependencies to be set but we are in process of resolving them
2918                         //
2919                         if (!(mc is TypeDefinition.BaseContext) && !(mc is UsingAliasNamespace.AliasContext)) {
2920                                 ObsoleteAttribute obsolete_attr = type.GetAttributeObsolete ();
2921                                 if (obsolete_attr != null && !mc.IsObsolete) {
2922                                         AttributeTester.Report_ObsoleteMessage (obsolete_attr, te.GetSignatureForError (), Location, mc.Module.Compiler.Report);
2923                                 }
2924                         }
2925
2926                         return type;
2927                 }
2928
2929
2930                 public override void Emit (EmitContext ec)
2931                 {
2932                         throw new InternalErrorException ("FullNamedExpression `{0}' found in resolved tree",
2933                                 GetSignatureForError ());
2934                 }
2935         }
2936
2937         /// <summary>
2938         ///   Expression that evaluates to a type
2939         /// </summary>
2940         public abstract class TypeExpr : FullNamedExpression
2941         {
2942                 public sealed override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc)
2943                 {
2944                         ResolveAsType (mc);
2945                         return this;
2946                 }
2947
2948                 protected sealed override Expression DoResolve (ResolveContext ec)
2949                 {
2950                         ResolveAsType (ec);
2951                         return this;
2952                 }
2953
2954                 public override bool Equals (object obj)
2955                 {
2956                         TypeExpr tobj = obj as TypeExpr;
2957                         if (tobj == null)
2958                                 return false;
2959
2960                         return Type == tobj.Type;
2961                 }
2962
2963                 public override int GetHashCode ()
2964                 {
2965                         return Type.GetHashCode ();
2966                 }
2967         }
2968
2969         /// <summary>
2970         ///   Fully resolved Expression that already evaluated to a type
2971         /// </summary>
2972         public class TypeExpression : TypeExpr
2973         {
2974                 public TypeExpression (TypeSpec t, Location l)
2975                 {
2976                         Type = t;
2977                         eclass = ExprClass.Type;
2978                         loc = l;
2979                 }
2980
2981                 public sealed override TypeSpec ResolveAsType (IMemberContext ec)
2982                 {
2983                         return type;
2984                 }
2985         }
2986
2987         /// <summary>
2988         ///   This class denotes an expression which evaluates to a member
2989         ///   of a struct or a class.
2990         /// </summary>
2991         public abstract class MemberExpr : Expression, OverloadResolver.IInstanceQualifier
2992         {
2993                 //
2994                 // An instance expression associated with this member, if it's a
2995                 // non-static member
2996                 //
2997                 public Expression InstanceExpression;
2998
2999                 /// <summary>
3000                 ///   The name of this member.
3001                 /// </summary>
3002                 public abstract string Name {
3003                         get;
3004                 }
3005
3006                 //
3007                 // When base.member is used
3008                 //
3009                 public bool IsBase {
3010                         get { return InstanceExpression is BaseThis; }
3011                 }
3012
3013                 /// <summary>
3014                 ///   Whether this is an instance member.
3015                 /// </summary>
3016                 public abstract bool IsInstance {
3017                         get;
3018                 }
3019
3020                 /// <summary>
3021                 ///   Whether this is a static member.
3022                 /// </summary>
3023                 public abstract bool IsStatic {
3024                         get;
3025                 }
3026
3027                 public abstract string KindName {
3028                         get;
3029                 }
3030
3031                 protected abstract TypeSpec DeclaringType {
3032                         get;
3033                 }
3034
3035                 TypeSpec OverloadResolver.IInstanceQualifier.InstanceType {
3036                         get {
3037                                 return InstanceExpression.Type;
3038                         }
3039                 }
3040
3041                 //
3042                 // Converts best base candidate for virtual method starting from QueriedBaseType
3043                 //
3044                 protected MethodSpec CandidateToBaseOverride (ResolveContext rc, MethodSpec method)
3045                 {
3046                         //
3047                         // Only when base.member is used and method is virtual
3048                         //
3049                         if (!IsBase)
3050                                 return method;
3051
3052                         //
3053                         // Overload resulution works on virtual or non-virtual members only (no overrides). That
3054                         // means for base.member access we have to find the closest match after we found best candidate
3055                         //
3056                         if ((method.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL | Modifiers.OVERRIDE)) != 0) {
3057                                 //
3058                                 // The method could already be what we are looking for
3059                                 //
3060                                 TypeSpec[] targs = null;
3061                                 if (method.DeclaringType != InstanceExpression.Type) {
3062                                         //
3063                                         // Candidate can have inflated MVAR parameters and we need to find
3064                                         // base match for original definition not inflated parameter types
3065                                         //
3066                                         var parameters = method.Parameters;
3067                                         if (method.Arity > 0) {
3068                                                 parameters = ((IParametersMember) method.MemberDefinition).Parameters;
3069                                                 var inflated = method.DeclaringType as InflatedTypeSpec;
3070                                                 if (inflated != null) {
3071                                                         parameters = parameters.Inflate (inflated.CreateLocalInflator (rc));
3072                                                 }
3073                                         }
3074
3075                                         var filter = new MemberFilter (method.Name, method.Arity, MemberKind.Method, parameters, null);
3076                                         var base_override = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as MethodSpec;
3077                                         if (base_override != null && base_override.DeclaringType != method.DeclaringType) {
3078                                                 if (base_override.IsGeneric)
3079                                                         targs = method.TypeArguments;
3080
3081                                                 method = base_override;
3082                                         }
3083                                 }
3084
3085                                 //
3086                                 // When base access is used inside anonymous method/iterator/etc we need to
3087                                 // get back to the context of original type. We do it by emiting proxy
3088                                 // method in original class and rewriting base call to this compiler
3089                                 // generated method call which does the actual base invocation. This may
3090                                 // introduce redundant storey but with `this' only but it's tricky to avoid
3091                                 // at this stage as we don't know what expressions follow base
3092                                 //
3093                                 if (rc.CurrentAnonymousMethod != null) {
3094                                         if (targs == null && method.IsGeneric) {
3095                                                 targs = method.TypeArguments;
3096                                                 method = method.GetGenericMethodDefinition ();
3097                                         }
3098
3099                                         if (method.Parameters.HasArglist)
3100                                                 throw new NotImplementedException ("__arglist base call proxy");
3101
3102                                         method = rc.CurrentMemberDefinition.Parent.PartialContainer.CreateHoistedBaseCallProxy (rc, method);
3103
3104                                         // Ideally this should apply to any proxy rewrite but in the case of unary mutators on
3105                                         // get/set member expressions second call would fail to proxy because left expression
3106                                         // would be of 'this' and not 'base' because we share InstanceExpression for get/set
3107                                         // FIXME: The async check is another hack but will probably fail with mutators
3108                                         if (rc.CurrentType.IsStruct || rc.CurrentAnonymousMethod.Storey is AsyncTaskStorey)
3109                                                 InstanceExpression = new This (loc).Resolve (rc);
3110                                 }
3111
3112                                 if (targs != null)
3113                                         method = method.MakeGenericMethod (rc, targs);
3114                         }
3115
3116                         //
3117                         // Only base will allow this invocation to happen.
3118                         //
3119                         if (method.IsAbstract) {
3120                                 rc.Report.SymbolRelatedToPreviousError (method);
3121                                 Error_CannotCallAbstractBase (rc, method.GetSignatureForError ());
3122                         }
3123
3124                         return method;
3125                 }
3126
3127                 protected void CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3128                 {
3129                         if (InstanceExpression == null)
3130                                 return;
3131
3132                         if ((member.Modifiers & Modifiers.PROTECTED) != 0 && !(InstanceExpression is This)) {
3133                                 if (!CheckProtectedMemberAccess (rc, member, InstanceExpression.Type)) {
3134                                         Error_ProtectedMemberAccess (rc, member, InstanceExpression.Type, loc);
3135                                 }
3136                         }
3137                 }
3138
3139                 bool OverloadResolver.IInstanceQualifier.CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3140                 {
3141                         if (InstanceExpression == null)
3142                                 return true;
3143
3144                         return InstanceExpression is This || CheckProtectedMemberAccess (rc, member, InstanceExpression.Type);
3145                 }
3146
3147                 public static bool CheckProtectedMemberAccess<T> (ResolveContext rc, T member, TypeSpec qualifier) where T : MemberSpec
3148                 {
3149                         var ct = rc.CurrentType;
3150                         if (ct == qualifier)
3151                                 return true;
3152
3153                         if ((member.Modifiers & Modifiers.INTERNAL) != 0 && member.DeclaringType.MemberDefinition.IsInternalAsPublic (ct.MemberDefinition.DeclaringAssembly))
3154                                 return true;
3155
3156                         qualifier = qualifier.GetDefinition ();
3157                         if (ct != qualifier && !IsSameOrBaseQualifier (ct, qualifier)) {
3158                                 return false;
3159                         }
3160
3161                         return true;
3162                 }
3163
3164                 public override bool ContainsEmitWithAwait ()
3165                 {
3166                         return InstanceExpression != null && InstanceExpression.ContainsEmitWithAwait ();
3167                 }
3168
3169                 static bool IsSameOrBaseQualifier (TypeSpec type, TypeSpec qtype)
3170                 {
3171                         do {
3172                                 type = type.GetDefinition ();
3173
3174                                 if (type == qtype || TypeManager.IsFamilyAccessible (qtype, type))
3175                                         return true;
3176
3177                                 type = type.DeclaringType;
3178                         } while (type != null);
3179
3180                         return false;
3181                 }
3182
3183                 protected void DoBestMemberChecks<T> (ResolveContext rc, T member) where T : MemberSpec, IInterfaceMemberSpec
3184                 {
3185                         if (InstanceExpression != null) {
3186                                 InstanceExpression = InstanceExpression.Resolve (rc);
3187                                 CheckProtectedMemberAccess (rc, member);
3188                         }
3189
3190                         if (member.MemberType.IsPointer && !rc.IsUnsafe) {
3191                                 UnsafeError (rc, loc);
3192                         }
3193
3194                         var dep = member.GetMissingDependencies ();
3195                         if (dep != null) {
3196                                 ImportedTypeDefinition.Error_MissingDependency (rc, dep, loc);
3197                         }
3198
3199                         if (!rc.IsObsolete) {
3200                                 ObsoleteAttribute oa = member.GetAttributeObsolete ();
3201                                 if (oa != null)
3202                                         AttributeTester.Report_ObsoleteMessage (oa, member.GetSignatureForError (), loc, rc.Report);
3203                         }
3204
3205                         if (!(member is FieldSpec))
3206                                 member.MemberDefinition.SetIsUsed ();
3207                 }
3208
3209                 protected virtual void Error_CannotCallAbstractBase (ResolveContext rc, string name)
3210                 {
3211                         rc.Report.Error (205, loc, "Cannot call an abstract base member `{0}'", name);
3212                 }
3213
3214                 public static void Error_ProtectedMemberAccess (ResolveContext rc, MemberSpec member, TypeSpec qualifier, Location loc)
3215                 {
3216                         rc.Report.SymbolRelatedToPreviousError (member);
3217                         rc.Report.Error (1540, loc,
3218                                 "Cannot access protected member `{0}' via a qualifier of type `{1}'. The qualifier must be of type `{2}' or derived from it",
3219                                 member.GetSignatureForError (), qualifier.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3220                 }
3221
3222                 public override void FlowAnalysis (FlowAnalysisContext fc)
3223                 {
3224                         if (InstanceExpression != null)
3225                                 InstanceExpression.FlowAnalysis (fc);
3226                 }
3227
3228                 public bool ResolveInstanceExpression (ResolveContext rc, Expression rhs)
3229                 {
3230                         if (!ResolveInstanceExpressionCore (rc, rhs))
3231                                 return false;
3232
3233                         //
3234                         // Check intermediate value modification which won't have any effect
3235                         //
3236                         if (rhs != null && InstanceExpression.Type.IsStruct) {
3237                                 var fexpr = InstanceExpression as FieldExpr;
3238                                 if (fexpr != null) {
3239                                         if (!fexpr.Spec.IsReadOnly || rc.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
3240                                                 return true;
3241
3242                                         if (fexpr.IsStatic) {
3243                                                 rc.Report.Error (1650, loc, "Fields of static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
3244                                                         fexpr.GetSignatureForError ());
3245                                         } else {
3246                                                 rc.Report.Error (1648, loc, "Members of readonly field `{0}' cannot be modified (except in a constructor or a variable initializer)",
3247                                                         fexpr.GetSignatureForError ());
3248                                         }
3249
3250                                         return true;
3251                                 }
3252
3253                                 if (InstanceExpression is PropertyExpr || InstanceExpression is IndexerExpr || InstanceExpression is Invocation) {
3254                                         if (rc.CurrentInitializerVariable != null) {
3255                                                 rc.Report.Error (1918, loc, "Members of value type `{0}' cannot be assigned using a property `{1}' object initializer",
3256                                                         InstanceExpression.Type.GetSignatureForError (), InstanceExpression.GetSignatureForError ());
3257                                         } else {
3258                                                 rc.Report.Error (1612, loc,
3259                                                         "Cannot modify a value type return value of `{0}'. Consider storing the value in a temporary variable",
3260                                                         InstanceExpression.GetSignatureForError ());
3261                                         }
3262
3263                                         return true;
3264                                 }
3265
3266                                 var lvr = InstanceExpression as LocalVariableReference;
3267                                 if (lvr != null) {
3268
3269                                         if (!lvr.local_info.IsReadonly)
3270                                                 return true;
3271
3272                                         rc.Report.Error (1654, loc, "Cannot assign to members of `{0}' because it is a `{1}'",
3273                                                 InstanceExpression.GetSignatureForError (), lvr.local_info.GetReadOnlyContext ());
3274                                 }
3275                         }
3276
3277                         return true;
3278                 }
3279
3280                 bool ResolveInstanceExpressionCore (ResolveContext rc, Expression rhs)
3281                 {
3282                         if (IsStatic) {
3283                                 if (InstanceExpression != null) {
3284                                         if (InstanceExpression is TypeExpr) {
3285                                                 var t = InstanceExpression.Type;
3286                                                 do {
3287                                                         ObsoleteAttribute oa = t.GetAttributeObsolete ();
3288                                                         if (oa != null && !rc.IsObsolete) {
3289                                                                 AttributeTester.Report_ObsoleteMessage (oa, t.GetSignatureForError (), loc, rc.Report);
3290                                                         }
3291
3292                                                         t = t.DeclaringType;
3293                                                 } while (t != null);
3294                                         } else {
3295                                                 var runtime_expr = InstanceExpression as RuntimeValueExpression;
3296                                                 if (runtime_expr == null || !runtime_expr.IsSuggestionOnly) {
3297                                                         rc.Report.Error (176, loc,
3298                                                                 "Static member `{0}' cannot be accessed with an instance reference, qualify it with a type name instead",
3299                                                                 GetSignatureForError ());
3300                                                 }
3301                                         }
3302
3303                                         InstanceExpression = null;
3304                                 }
3305
3306                                 return false;
3307                         }
3308
3309                         if (InstanceExpression == null || InstanceExpression is TypeExpr) {
3310                                 if (InstanceExpression != null || !This.IsThisAvailable (rc, true)) {
3311                                         if (rc.HasSet (ResolveContext.Options.FieldInitializerScope))
3312                                                 rc.Report.Error (236, loc,
3313                                                         "A field initializer cannot reference the nonstatic field, method, or property `{0}'",
3314                                                         GetSignatureForError ());
3315                                         else
3316                                                 rc.Report.Error (120, loc,
3317                                                         "An object reference is required to access non-static member `{0}'",
3318                                                         GetSignatureForError ());
3319
3320                                         InstanceExpression = new CompilerGeneratedThis (rc.CurrentType, loc).Resolve (rc);
3321                                         return false;
3322                                 }
3323
3324                                 if (!TypeManager.IsFamilyAccessible (rc.CurrentType, DeclaringType)) {
3325                                         rc.Report.Error (38, loc,
3326                                                 "Cannot access a nonstatic member of outer type `{0}' via nested type `{1}'",
3327                                                 DeclaringType.GetSignatureForError (), rc.CurrentType.GetSignatureForError ());
3328                                 }
3329
3330                                 InstanceExpression = new This (loc).Resolve (rc);
3331                                 return false;
3332                         }
3333
3334                         var me = InstanceExpression as MemberExpr;
3335                         if (me != null) {
3336                                 me.ResolveInstanceExpressionCore (rc, rhs);
3337
3338                                 var fe = me as FieldExpr;
3339                                 if (fe != null && fe.IsMarshalByRefAccess (rc)) {
3340                                         rc.Report.SymbolRelatedToPreviousError (me.DeclaringType);
3341                                         rc.Report.Warning (1690, 1, loc,
3342                                                 "Cannot call methods, properties, or indexers on `{0}' because it is a value type member of a marshal-by-reference class",
3343                                                 me.GetSignatureForError ());
3344                                 }
3345
3346                                 return true;
3347                         }
3348
3349                         //
3350                         // Additional checks for l-value member access
3351                         //
3352                         if (rhs != null) {
3353                                 if (InstanceExpression is UnboxCast) {
3354                                         rc.Report.Error (445, InstanceExpression.Location, "Cannot modify the result of an unboxing conversion");
3355                                 }
3356                         }
3357
3358                         return true;
3359                 }
3360
3361                 public virtual MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3362                 {
3363                         if (left != null && left.IsNull && TypeSpec.IsReferenceType (left.Type)) {
3364                                 ec.Report.Warning (1720, 1, left.Location,
3365                                         "Expression will always cause a `{0}'", "System.NullReferenceException");
3366                         }
3367
3368                         InstanceExpression = left;
3369                         return this;
3370                 }
3371
3372                 protected void EmitInstance (EmitContext ec, bool prepare_for_load)
3373                 {
3374                         TypeSpec instance_type = InstanceExpression.Type;
3375                         if (TypeSpec.IsValueType (instance_type)) {
3376                                 if (InstanceExpression is IMemoryLocation) {
3377                                         ((IMemoryLocation) InstanceExpression).AddressOf (ec, AddressOp.Load);
3378                                 } else {
3379                                         // Cannot release the temporary variable when its address
3380                                         // is required to be on stack for any parent
3381                                         LocalTemporary t = new LocalTemporary (instance_type);
3382                                         InstanceExpression.Emit (ec);
3383                                         t.Store (ec);
3384                                         t.AddressOf (ec, AddressOp.Store);
3385                                 }
3386                         } else {
3387                                 InstanceExpression.Emit (ec);
3388
3389                                 // Only to make verifier happy
3390                                 if (instance_type.IsGenericParameter && !(InstanceExpression is This) && TypeSpec.IsReferenceType (instance_type))
3391                                         ec.Emit (OpCodes.Box, instance_type);
3392                         }
3393
3394                         if (prepare_for_load)
3395                                 ec.Emit (OpCodes.Dup);
3396                 }
3397
3398                 public abstract void SetTypeArguments (ResolveContext ec, TypeArguments ta);
3399         }
3400
3401         public class ExtensionMethodCandidates
3402         {
3403                 readonly NamespaceContainer container;
3404                 readonly IList<MethodSpec> methods;
3405                 readonly int index;
3406                 readonly IMemberContext context;
3407
3408                 public ExtensionMethodCandidates (IMemberContext context, IList<MethodSpec> methods, NamespaceContainer nsContainer, int lookupIndex)
3409                 {
3410                         this.context = context;
3411                         this.methods = methods;
3412                         this.container = nsContainer;
3413                         this.index = lookupIndex;
3414                 }
3415
3416                 public NamespaceContainer Container {
3417                         get {
3418                                 return container;
3419                         }
3420                 }
3421
3422                 public IMemberContext Context {
3423                         get {
3424                                 return context;
3425                         }
3426                 }
3427
3428                 public int LookupIndex {
3429                         get {
3430                                 return index;
3431                         }
3432                 }
3433
3434                 public IList<MethodSpec> Methods {
3435                         get {
3436                                 return methods;
3437                         }
3438                 }
3439         }
3440
3441         //
3442         // Represents a group of extension method candidates for whole namespace
3443         //
3444         class ExtensionMethodGroupExpr : MethodGroupExpr, OverloadResolver.IErrorHandler
3445         {
3446                 ExtensionMethodCandidates candidates;
3447                 public Expression ExtensionExpression;
3448
3449                 public ExtensionMethodGroupExpr (ExtensionMethodCandidates candidates, Expression extensionExpr, Location loc)
3450                         : base (candidates.Methods.Cast<MemberSpec>().ToList (), extensionExpr.Type, loc)
3451                 {
3452                         this.candidates = candidates;
3453                         this.ExtensionExpression = extensionExpr;
3454                 }
3455
3456                 public override bool IsStatic {
3457                         get { return true; }
3458                 }
3459
3460                 //
3461                 // For extension methodgroup we are not looking for base members but parent
3462                 // namespace extension methods
3463                 //
3464                 public override IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3465                 {
3466                         // TODO: candidates are null only when doing error reporting, that's
3467                         // incorrect. We have to discover same extension methods in error mode
3468                         if (candidates == null)
3469                                 return null;
3470
3471                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3472
3473                         candidates = candidates.Container.LookupExtensionMethod (candidates.Context, ExtensionExpression.Type, Name, arity, candidates.LookupIndex);
3474                         if (candidates == null)
3475                                 return null;
3476
3477                         return candidates.Methods.Cast<MemberSpec> ().ToList ();
3478                 }
3479
3480                 public override MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3481                 {
3482                         // We are already here
3483                         return null;
3484                 }
3485
3486                 public override MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments arguments, OverloadResolver.IErrorHandler ehandler, OverloadResolver.Restrictions restr)
3487                 {
3488                         if (arguments == null)
3489                                 arguments = new Arguments (1);
3490
3491                         ExtensionExpression = ExtensionExpression.Resolve (ec);
3492                         if (ExtensionExpression == null)
3493                                 return null;
3494
3495                         var cand = candidates;
3496                         arguments.Insert (0, new Argument (ExtensionExpression, Argument.AType.ExtensionType));
3497                         var res = base.OverloadResolve (ec, ref arguments, ehandler ?? this, restr);
3498
3499                         // Restore candidates in case we are running in probing mode
3500                         candidates = cand;
3501
3502                         // Store resolved argument and restore original arguments
3503                         if (res == null) {
3504                                 // Clean-up modified arguments for error reporting
3505                                 arguments.RemoveAt (0);
3506                                 return null;
3507                         }
3508
3509                         var me = ExtensionExpression as MemberExpr;
3510                         if (me != null) {
3511                                 me.ResolveInstanceExpression (ec, null);
3512                                 var fe = me as FieldExpr;
3513                                 if (fe != null)
3514                                         fe.Spec.MemberDefinition.SetIsUsed ();
3515                         }
3516
3517                         InstanceExpression = null;
3518                         return this;
3519                 }
3520
3521                 #region IErrorHandler Members
3522
3523                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous)
3524                 {
3525                         return false;
3526                 }
3527
3528                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
3529                 {
3530                         rc.Report.SymbolRelatedToPreviousError (best);
3531                         rc.Report.Error (1928, loc,
3532                                 "Type `{0}' does not contain a member `{1}' and the best extension method overload `{2}' has some invalid arguments",
3533                                 queried_type.GetSignatureForError (), Name, best.GetSignatureForError ());
3534
3535                         if (index == 0) {
3536                                 rc.Report.Error (1929, loc,
3537                                         "Extension method instance type `{0}' cannot be converted to `{1}'",
3538                                         arg.Type.GetSignatureForError (), ((MethodSpec)best).Parameters.ExtensionMethodType.GetSignatureForError ());
3539                         }
3540
3541                         return true;
3542                 }
3543
3544                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
3545                 {
3546                         return false;
3547                 }
3548
3549                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
3550                 {
3551                         return false;
3552                 }
3553
3554                 #endregion
3555         }
3556
3557         /// <summary>
3558         ///   MethodGroupExpr represents a group of method candidates which
3559         ///   can be resolved to the best method overload
3560         /// </summary>
3561         public class MethodGroupExpr : MemberExpr, OverloadResolver.IBaseMembersProvider
3562         {
3563                 static readonly MemberSpec[] Excluded = new MemberSpec[0];
3564
3565                 protected IList<MemberSpec> Methods;
3566                 MethodSpec best_candidate;
3567                 TypeSpec best_candidate_return;
3568                 protected TypeArguments type_arguments;
3569
3570                 SimpleName simple_name;
3571                 protected TypeSpec queried_type;
3572
3573                 public MethodGroupExpr (IList<MemberSpec> mi, TypeSpec type, Location loc)
3574                 {
3575                         Methods = mi;
3576                         this.loc = loc;
3577                         this.type = InternalType.MethodGroup;
3578
3579                         eclass = ExprClass.MethodGroup;
3580                         queried_type = type;
3581                 }
3582
3583                 public MethodGroupExpr (MethodSpec m, TypeSpec type, Location loc)
3584                         : this (new MemberSpec[] { m }, type, loc)
3585                 {
3586                 }
3587
3588                 #region Properties
3589
3590                 public MethodSpec BestCandidate {
3591                         get {
3592                                 return best_candidate;
3593                         }
3594                 }
3595
3596                 public TypeSpec BestCandidateReturnType {
3597                         get {
3598                                 return best_candidate_return;
3599                         }
3600                 }
3601
3602                 public IList<MemberSpec> Candidates {
3603                         get {
3604                                 return Methods;
3605                         }
3606                 }
3607
3608                 protected override TypeSpec DeclaringType {
3609                         get {
3610                                 return queried_type;
3611                         }
3612                 }
3613
3614                 public bool IsConditionallyExcluded {
3615                         get {
3616                                 return Methods == Excluded;
3617                         }
3618                 }
3619
3620                 public override bool IsInstance {
3621                         get {
3622                                 if (best_candidate != null)
3623                                         return !best_candidate.IsStatic;
3624
3625                                 return false;
3626                         }
3627                 }
3628
3629                 public override bool IsSideEffectFree {
3630                         get {
3631                                 return InstanceExpression == null || InstanceExpression.IsSideEffectFree;
3632                         }
3633                 }
3634
3635                 public override bool IsStatic {
3636                         get {
3637                                 if (best_candidate != null)
3638                                         return best_candidate.IsStatic;
3639
3640                                 return false;
3641                         }
3642                 }
3643
3644                 public override string KindName {
3645                         get { return "method"; }
3646                 }
3647
3648                 public override string Name {
3649                         get {
3650                                 if (best_candidate != null)
3651                                         return best_candidate.Name;
3652
3653                                 // TODO: throw ?
3654                                 return Methods.First ().Name;
3655                         }
3656                 }
3657
3658                 #endregion
3659
3660                 //
3661                 // When best candidate is already know this factory can be used
3662                 // to avoid expensive overload resolution to be called
3663                 //
3664                 // NOTE: InstanceExpression has to be set manually
3665                 //
3666                 public static MethodGroupExpr CreatePredefined (MethodSpec best, TypeSpec queriedType, Location loc)
3667                 {
3668                         return new MethodGroupExpr (best, queriedType, loc) {
3669                                 best_candidate = best,
3670                                 best_candidate_return = best.ReturnType
3671                         };
3672                 }
3673
3674                 public override string GetSignatureForError ()
3675                 {
3676                         if (best_candidate != null)
3677                                 return best_candidate.GetSignatureForError ();
3678
3679                         return Methods.First ().GetSignatureForError ();
3680                 }
3681
3682                 public override Expression CreateExpressionTree (ResolveContext ec)
3683                 {
3684                         if (best_candidate == null) {
3685                                 ec.Report.Error (1953, loc, "An expression tree cannot contain an expression with method group");
3686                                 return null;
3687                         }
3688
3689                         if (IsConditionallyExcluded)
3690                                 ec.Report.Error (765, loc,
3691                                         "Partial methods with only a defining declaration or removed conditional methods cannot be used in an expression tree");
3692
3693                         return new TypeOfMethod (best_candidate, loc);
3694                 }
3695
3696                 protected override Expression DoResolve (ResolveContext ec)
3697                 {
3698                         this.eclass = ExprClass.MethodGroup;
3699
3700                         if (InstanceExpression != null) {
3701                                 InstanceExpression = InstanceExpression.Resolve (ec);
3702                                 if (InstanceExpression == null)
3703                                         return null;
3704                         }
3705
3706                         return this;
3707                 }
3708
3709                 public override void Emit (EmitContext ec)
3710                 {
3711                         throw new NotSupportedException ();
3712                 }
3713
3714                 public void EmitCall (EmitContext ec, Arguments arguments)
3715                 {
3716                         var call = new CallEmitter ();
3717                         call.InstanceExpression = InstanceExpression;
3718                         call.Emit (ec, best_candidate, arguments, loc);
3719                 }
3720
3721                 public override void Error_ValueCannotBeConverted (ResolveContext ec, TypeSpec target, bool expl)
3722                 {
3723                         ec.Report.Error (428, loc, "Cannot convert method group `{0}' to non-delegate type `{1}'. Consider using parentheses to invoke the method",
3724                                 Name, target.GetSignatureForError ());
3725                 }
3726
3727                 public static bool IsExtensionMethodArgument (Expression expr)
3728                 {
3729                         //
3730                         // LAMESPEC: No details about which expressions are not allowed
3731                         //
3732                         return !(expr is TypeExpr) && !(expr is BaseThis);
3733                 }
3734
3735                 /// <summary>
3736                 ///   Find the Applicable Function Members (7.4.2.1)
3737                 ///
3738                 ///   me: Method Group expression with the members to select.
3739                 ///       it might contain constructors or methods (or anything
3740                 ///       that maps to a method).
3741                 ///
3742                 ///   Arguments: ArrayList containing resolved Argument objects.
3743                 ///
3744                 ///   loc: The location if we want an error to be reported, or a Null
3745                 ///        location for "probing" purposes.
3746                 ///
3747                 ///   Returns: The MethodBase (either a ConstructorInfo or a MethodInfo)
3748                 ///            that is the best match of me on Arguments.
3749                 ///
3750                 /// </summary>
3751                 public virtual MethodGroupExpr OverloadResolve (ResolveContext ec, ref Arguments args, OverloadResolver.IErrorHandler cerrors, OverloadResolver.Restrictions restr)
3752                 {
3753                         // TODO: causes issues with probing mode, remove explicit Kind check
3754                         if (best_candidate != null && best_candidate.Kind == MemberKind.Destructor)
3755                                 return this;
3756
3757                         var r = new OverloadResolver (Methods, type_arguments, restr, loc);
3758                         if ((restr & OverloadResolver.Restrictions.NoBaseMembers) == 0) {
3759                                 r.BaseMembersProvider = this;
3760                                 r.InstanceQualifier = this;
3761                         }
3762
3763                         if (cerrors != null)
3764                                 r.CustomErrors = cerrors;
3765
3766                         // TODO: When in probing mode do IsApplicable only and when called again do VerifyArguments for full error reporting
3767                         best_candidate = r.ResolveMember<MethodSpec> (ec, ref args);
3768                         if (best_candidate == null)
3769                                 return r.BestCandidateIsDynamic ? this : null;
3770
3771                         // Overload resolver had to create a new method group, all checks bellow have already been executed
3772                         if (r.BestCandidateNewMethodGroup != null)
3773                                 return r.BestCandidateNewMethodGroup;
3774
3775                         if (best_candidate.Kind == MemberKind.Method && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0) {
3776                                 if (InstanceExpression != null) {
3777                                         if (best_candidate.IsExtensionMethod && args[0].Expr == InstanceExpression) {
3778                                                 InstanceExpression = null;
3779                                         } else {
3780                                                 if (best_candidate.IsStatic && simple_name != null) {
3781                                                         InstanceExpression = ProbeIdenticalTypeName (ec, InstanceExpression, simple_name);
3782                                                 }
3783
3784                                                 InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue | ResolveFlags.MethodGroup | ResolveFlags.Type);
3785                                         }
3786                                 }
3787
3788                                 ResolveInstanceExpression (ec, null);
3789                         }
3790
3791                         var base_override = CandidateToBaseOverride (ec, best_candidate);
3792                         if (base_override == best_candidate) {
3793                                 best_candidate_return = r.BestCandidateReturnType;
3794                         } else {
3795                                 best_candidate = base_override;
3796                                 best_candidate_return = best_candidate.ReturnType;
3797                         }
3798
3799                         if (best_candidate.IsGeneric && (restr & OverloadResolver.Restrictions.ProbingOnly) == 0 && TypeParameterSpec.HasAnyTypeParameterConstrained (best_candidate.GenericDefinition)) {
3800                                 ConstraintChecker cc = new ConstraintChecker (ec);
3801                                 cc.CheckAll (best_candidate.GetGenericMethodDefinition (), best_candidate.TypeArguments, best_candidate.Constraints, loc);
3802                         }
3803
3804                         //
3805                         // Additional check for possible imported base override method which
3806                         // could not be done during IsOverrideMethodBaseTypeAccessible
3807                         //
3808                         if (best_candidate.IsVirtual && (best_candidate.DeclaringType.Modifiers & Modifiers.PROTECTED) != 0 &&
3809                                 best_candidate.MemberDefinition.IsImported && !best_candidate.DeclaringType.IsAccessible (ec)) {
3810                                 ec.Report.SymbolRelatedToPreviousError (best_candidate);
3811                                 ErrorIsInaccesible (ec, best_candidate.GetSignatureForError (), loc);
3812                         }
3813
3814                         // Speed up the check by not doing it on disallowed targets
3815                         if (best_candidate_return.Kind == MemberKind.Void && best_candidate.IsConditionallyExcluded (ec))
3816                                 Methods = Excluded;
3817
3818                         return this;
3819                 }
3820
3821                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
3822                 {
3823                         var fe = left as FieldExpr;
3824                         if (fe != null) {
3825                                 //
3826                                 // Using method-group on struct fields makes the struct assigned. I am not sure
3827                                 // why but that's what .net does
3828                                 //
3829                                 fe.Spec.MemberDefinition.SetIsAssigned ();
3830                         }
3831
3832                         simple_name = original;
3833                         return base.ResolveMemberAccess (ec, left, original);
3834                 }
3835
3836                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
3837                 {
3838                         type_arguments = ta;
3839                 }
3840
3841                 #region IBaseMembersProvider Members
3842
3843                 public virtual IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3844                 {
3845                         return baseType == null ? null : MemberCache.FindMembers (baseType, Methods [0].Name, false);
3846                 }
3847
3848                 public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3849                 {
3850                         if (queried_type == member.DeclaringType)
3851                                 return null;
3852
3853                         return MemberCache.FindMember (queried_type, new MemberFilter ((MethodSpec) member),
3854                                 BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as IParametersMember;
3855                 }
3856
3857                 //
3858                 // Extension methods lookup after ordinary methods candidates failed to apply
3859                 //
3860                 public virtual MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3861                 {
3862                         if (InstanceExpression == null || InstanceExpression.eclass == ExprClass.Type)
3863                                 return null;
3864
3865                         if (!IsExtensionMethodArgument (InstanceExpression))
3866                                 return null;
3867
3868                         int arity = type_arguments == null ? 0 : type_arguments.Count;
3869                         var methods = rc.LookupExtensionMethod (InstanceExpression.Type, Methods[0].Name, arity);
3870                         if (methods == null)
3871                                 return null;
3872
3873                         var emg = new ExtensionMethodGroupExpr (methods, InstanceExpression, loc);
3874                         emg.SetTypeArguments (rc, type_arguments);
3875                         return emg;
3876                 }
3877
3878                 #endregion
3879         }
3880
3881         struct ConstructorInstanceQualifier : OverloadResolver.IInstanceQualifier
3882         {
3883                 public ConstructorInstanceQualifier (TypeSpec type)
3884                         : this ()
3885                 {
3886                         InstanceType = type;
3887                 }
3888
3889                 public TypeSpec InstanceType { get; private set; }
3890
3891                 public bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member)
3892                 {
3893                         return MemberExpr.CheckProtectedMemberAccess (rc, member, InstanceType);
3894                 }
3895         }
3896
3897         public struct OverloadResolver
3898         {
3899                 [Flags]
3900                 public enum Restrictions
3901                 {
3902                         None = 0,
3903                         DelegateInvoke = 1,
3904                         ProbingOnly     = 1 << 1,
3905                         CovariantDelegate = 1 << 2,
3906                         NoBaseMembers = 1 << 3,
3907                         BaseMembersIncluded = 1 << 4
3908                 }
3909
3910                 public interface IBaseMembersProvider
3911                 {
3912                         IList<MemberSpec> GetBaseMembers (TypeSpec baseType);
3913                         IParametersMember GetOverrideMemberParameters (MemberSpec member);
3914                         MethodGroupExpr LookupExtensionMethod (ResolveContext rc);
3915                 }
3916
3917                 public interface IErrorHandler
3918                 {
3919                         bool AmbiguousCandidates (ResolveContext rc, MemberSpec best, MemberSpec ambiguous);
3920                         bool ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument a, int index);
3921                         bool NoArgumentMatch (ResolveContext rc, MemberSpec best);
3922                         bool TypeInferenceFailed (ResolveContext rc, MemberSpec best);
3923                 }
3924
3925                 public interface IInstanceQualifier
3926                 {
3927                         TypeSpec InstanceType { get; }
3928                         bool CheckProtectedMemberAccess (ResolveContext rc, MemberSpec member);
3929                 }
3930
3931                 sealed class NoBaseMembers : IBaseMembersProvider
3932                 {
3933                         public static readonly IBaseMembersProvider Instance = new NoBaseMembers ();
3934
3935                         public IList<MemberSpec> GetBaseMembers (TypeSpec baseType)
3936                         {
3937                                 return null;
3938                         }
3939
3940                         public IParametersMember GetOverrideMemberParameters (MemberSpec member)
3941                         {
3942                                 return null;
3943                         }
3944
3945                         public MethodGroupExpr LookupExtensionMethod (ResolveContext rc)
3946                         {
3947                                 return null;
3948                         }
3949                 }
3950
3951                 struct AmbiguousCandidate
3952                 {
3953                         public readonly MemberSpec Member;
3954                         public readonly bool Expanded;
3955                         public readonly AParametersCollection Parameters;
3956
3957                         public AmbiguousCandidate (MemberSpec member, AParametersCollection parameters, bool expanded)
3958                         {
3959                                 Member = member;
3960                                 Parameters = parameters;
3961                                 Expanded = expanded;
3962                         }
3963                 }
3964
3965                 Location loc;
3966                 IList<MemberSpec> members;
3967                 TypeArguments type_arguments;
3968                 IBaseMembersProvider base_provider;
3969                 IErrorHandler custom_errors;
3970                 IInstanceQualifier instance_qualifier;
3971                 Restrictions restrictions;
3972                 MethodGroupExpr best_candidate_extension_group;
3973                 TypeSpec best_candidate_return_type;
3974
3975                 SessionReportPrinter lambda_conv_msgs;
3976
3977                 public OverloadResolver (IList<MemberSpec> members, Restrictions restrictions, Location loc)
3978                         : this (members, null, restrictions, loc)
3979                 {
3980                 }
3981
3982                 public OverloadResolver (IList<MemberSpec> members, TypeArguments targs, Restrictions restrictions, Location loc)
3983                         : this ()
3984                 {
3985                         if (members == null || members.Count == 0)
3986                                 throw new ArgumentException ("empty members set");
3987
3988                         this.members = members;
3989                         this.loc = loc;
3990                         type_arguments = targs;
3991                         this.restrictions = restrictions;
3992                         if (IsDelegateInvoke)
3993                                 this.restrictions |= Restrictions.NoBaseMembers;
3994
3995                         base_provider = NoBaseMembers.Instance;
3996                 }
3997
3998                 #region Properties
3999
4000                 public IBaseMembersProvider BaseMembersProvider {
4001                         get {
4002                                 return base_provider;
4003                         }
4004                         set {
4005                                 base_provider = value;
4006                         }
4007                 }
4008
4009                 public bool BestCandidateIsDynamic { get; set; }
4010
4011                 //
4012                 // Best candidate was found in newly created MethodGroupExpr, used by extension methods
4013                 //
4014                 public MethodGroupExpr BestCandidateNewMethodGroup {
4015                         get {
4016                                 return best_candidate_extension_group;
4017                         }
4018                 }
4019
4020                 //
4021                 // Return type can be different between best candidate and closest override
4022                 //
4023                 public TypeSpec BestCandidateReturnType {
4024                         get {
4025                                 return best_candidate_return_type;
4026                         }
4027                 }
4028
4029                 public IErrorHandler CustomErrors {
4030                         get {
4031                                 return custom_errors;
4032                         }
4033                         set {
4034                                 custom_errors = value;
4035                         }
4036                 }
4037
4038                 TypeSpec DelegateType {
4039                         get {
4040                                 if ((restrictions & Restrictions.DelegateInvoke) == 0)
4041                                         throw new InternalErrorException ("Not running in delegate mode", loc);
4042
4043                                 return members [0].DeclaringType;
4044                         }
4045                 }
4046
4047                 public IInstanceQualifier InstanceQualifier {
4048                         get {
4049                                 return instance_qualifier;
4050                         }
4051                         set {
4052                                 instance_qualifier = value;
4053                         }
4054                 }
4055
4056                 bool IsProbingOnly {
4057                         get {
4058                                 return (restrictions & Restrictions.ProbingOnly) != 0;
4059                         }
4060                 }
4061
4062                 bool IsDelegateInvoke {
4063                         get {
4064                                 return (restrictions & Restrictions.DelegateInvoke) != 0;
4065                         }
4066                 }
4067
4068                 #endregion
4069
4070                 //
4071                 //  7.4.3.3  Better conversion from expression
4072                 //  Returns :   1    if a->p is better,
4073                 //              2    if a->q is better,
4074                 //              0 if neither is better
4075                 //
4076                 static int BetterExpressionConversion (ResolveContext ec, Argument a, TypeSpec p, TypeSpec q)
4077                 {
4078                         TypeSpec argument_type = a.Type;
4079
4080                         //
4081                         // If argument is an anonymous function
4082                         //
4083                         if (argument_type == InternalType.AnonymousMethod && ec.Module.Compiler.Settings.Version > LanguageVersion.ISO_2) {
4084                                 //
4085                                 // p and q are delegate types or expression tree types
4086                                 //
4087                                 if (p.IsExpressionTreeType || q.IsExpressionTreeType) {
4088                                         if (q.MemberDefinition != p.MemberDefinition) {
4089                                                 return 0;
4090                                         }
4091
4092                                         //
4093                                         // Uwrap delegate from Expression<T>
4094                                         //
4095                                         q = TypeManager.GetTypeArguments (q)[0];
4096                                         p = TypeManager.GetTypeArguments (p)[0];
4097                                 }
4098
4099                                 var p_m = Delegate.GetInvokeMethod (p);
4100                                 var q_m = Delegate.GetInvokeMethod (q);
4101
4102                                 //
4103                                 // With identical parameter lists
4104                                 //
4105                                 if (!TypeSpecComparer.Equals (p_m.Parameters.Types, q_m.Parameters.Types))
4106                                         return 0;
4107
4108                                 var orig_p = p;
4109                                 p = p_m.ReturnType;
4110                                 var orig_q = q;
4111                                 q = q_m.ReturnType;
4112
4113                                 //
4114                                 // if p is void returning, and q has a return type Y, then C2 is the better conversion.
4115                                 //
4116                                 if (p.Kind == MemberKind.Void) {
4117                                         return q.Kind != MemberKind.Void ? 2 : 0;
4118                                 }
4119
4120                                 //
4121                                 // if p has a return type Y, and q is void returning, then C1 is the better conversion.
4122                                 //
4123                                 if (q.Kind == MemberKind.Void) {
4124                                         return p.Kind != MemberKind.Void ? 1: 0;
4125                                 }
4126
4127                                 var am = (AnonymousMethodExpression) a.Expr;
4128
4129                                 //
4130                                 // When anonymous method is an asynchronous, and P has a return type Task<Y1>, and Q has a return type Task<Y2>
4131                                 // better conversion is performed between underlying types Y1 and Y2
4132                                 //
4133                                 if (p.IsGenericTask || q.IsGenericTask) {
4134                                         if (am.Block.IsAsync && p.IsGenericTask && q.IsGenericTask) {
4135                                                 q = q.TypeArguments[0];
4136                                                 p = p.TypeArguments[0];
4137                                         }
4138                                 } else if (q != p) {
4139                                         //
4140                                         // LAMESPEC: Lambda expression returning dynamic type has identity (better) conversion to delegate returning object type
4141                                         //
4142                                         if (q.BuiltinType == BuiltinTypeSpec.Type.Object) {
4143                                                 var am_rt = am.InferReturnType (ec, null, orig_q);
4144                                                 if (am_rt != null && am_rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4145                                                         return 2;
4146                                         } else if (p.BuiltinType == BuiltinTypeSpec.Type.Object) {
4147                                                 var am_rt = am.InferReturnType (ec, null, orig_p);
4148                                                 if (am_rt != null && am_rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
4149                                                         return 1;
4150                                         }
4151                                 }
4152
4153                                 //
4154                                 // The parameters are identicial and return type is not void, use better type conversion
4155                                 // on return type to determine better one
4156                                 //
4157                         } else {
4158                                 if (argument_type == p)
4159                                         return 1;
4160
4161                                 if (argument_type == q)
4162                                         return 2;
4163                         }
4164
4165                         return BetterTypeConversion (ec, p, q);
4166                 }
4167
4168                 //
4169                 // 7.4.3.4  Better conversion from type
4170                 //
4171                 public static int BetterTypeConversion (ResolveContext ec, TypeSpec p, TypeSpec q)
4172                 {
4173                         if (p == null || q == null)
4174                                 throw new InternalErrorException ("BetterTypeConversion got a null conversion");
4175
4176                         switch (p.BuiltinType) {
4177                         case BuiltinTypeSpec.Type.Int:
4178                                 if (q.BuiltinType == BuiltinTypeSpec.Type.UInt || q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4179                                         return 1;
4180                                 break;
4181                         case BuiltinTypeSpec.Type.Long:
4182                                 if (q.BuiltinType == BuiltinTypeSpec.Type.ULong)
4183                                         return 1;
4184                                 break;
4185                         case BuiltinTypeSpec.Type.SByte:
4186                                 switch (q.BuiltinType) {
4187                                 case BuiltinTypeSpec.Type.Byte:
4188                                 case BuiltinTypeSpec.Type.UShort:
4189                                 case BuiltinTypeSpec.Type.UInt:
4190                                 case BuiltinTypeSpec.Type.ULong:
4191                                         return 1;
4192                                 }
4193                                 break;
4194                         case BuiltinTypeSpec.Type.Short:
4195                                 switch (q.BuiltinType) {
4196                                 case BuiltinTypeSpec.Type.UShort:
4197                                 case BuiltinTypeSpec.Type.UInt:
4198                                 case BuiltinTypeSpec.Type.ULong:
4199                                         return 1;
4200                                 }
4201                                 break;
4202                         case BuiltinTypeSpec.Type.Dynamic:
4203                                 // Dynamic is never better
4204                                 return 2;
4205                         }
4206
4207                         switch (q.BuiltinType) {
4208                         case BuiltinTypeSpec.Type.Int:
4209                                 if (p.BuiltinType == BuiltinTypeSpec.Type.UInt || p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4210                                         return 2;
4211                                 break;
4212                         case BuiltinTypeSpec.Type.Long:
4213                                 if (p.BuiltinType == BuiltinTypeSpec.Type.ULong)
4214                                         return 2;
4215                                 break;
4216                         case BuiltinTypeSpec.Type.SByte:
4217                                 switch (p.BuiltinType) {
4218                                 case BuiltinTypeSpec.Type.Byte:
4219                                 case BuiltinTypeSpec.Type.UShort:
4220                                 case BuiltinTypeSpec.Type.UInt:
4221                                 case BuiltinTypeSpec.Type.ULong:
4222                                         return 2;
4223                                 }
4224                                 break;
4225                         case BuiltinTypeSpec.Type.Short:
4226                                 switch (p.BuiltinType) {
4227                                 case BuiltinTypeSpec.Type.UShort:
4228                                 case BuiltinTypeSpec.Type.UInt:
4229                                 case BuiltinTypeSpec.Type.ULong:
4230                                         return 2;
4231                                 }
4232                                 break;
4233                         case BuiltinTypeSpec.Type.Dynamic:
4234                                 // Dynamic is never better
4235                                 return 1;
4236                         }
4237
4238                         // FIXME: handle lifted operators
4239
4240                         // TODO: this is expensive
4241                         Expression p_tmp = new EmptyExpression (p);
4242                         Expression q_tmp = new EmptyExpression (q);
4243
4244                         bool p_to_q = Convert.ImplicitConversionExists (ec, p_tmp, q);
4245                         bool q_to_p = Convert.ImplicitConversionExists (ec, q_tmp, p);
4246
4247                         if (p_to_q && !q_to_p)
4248                                 return 1;
4249
4250                         if (q_to_p && !p_to_q)
4251                                 return 2;
4252
4253                         return 0;
4254                 }
4255
4256                 /// <summary>
4257                 ///   Determines "Better function" between candidate
4258                 ///   and the current best match
4259                 /// </summary>
4260                 /// <remarks>
4261                 ///    Returns a boolean indicating :
4262                 ///     false if candidate ain't better
4263                 ///     true  if candidate is better than the current best match
4264                 /// </remarks>
4265                 static bool BetterFunction (ResolveContext ec, Arguments args, MemberSpec candidate, AParametersCollection cparam, bool candidate_params,
4266                         MemberSpec best, AParametersCollection bparam, bool best_params)
4267                 {
4268                         AParametersCollection candidate_pd = ((IParametersMember) candidate).Parameters;
4269                         AParametersCollection best_pd = ((IParametersMember) best).Parameters;
4270
4271                         bool better_at_least_one = false;
4272                         bool same = true;
4273                         int args_count = args == null ? 0 : args.Count;
4274                         int j = 0;
4275                         Argument a = null;
4276                         TypeSpec ct, bt;
4277                         for (int c_idx = 0, b_idx = 0; j < args_count; ++j, ++c_idx, ++b_idx) {
4278                                 a = args[j];
4279
4280                                 // Default arguments are ignored for better decision
4281                                 if (a.IsDefaultArgument)
4282                                         break;
4283
4284                                 //
4285                                 // When comparing named argument the parameter type index has to be looked up
4286                                 // in original parameter set (override version for virtual members)
4287                                 //
4288                                 NamedArgument na = a as NamedArgument;
4289                                 if (na != null) {
4290                                         int idx = cparam.GetParameterIndexByName (na.Name);
4291                                         ct = candidate_pd.Types[idx];
4292                                         if (candidate_params && candidate_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4293                                                 ct = TypeManager.GetElementType (ct);
4294
4295                                         idx = bparam.GetParameterIndexByName (na.Name);
4296                                         bt = best_pd.Types[idx];
4297                                         if (best_params && best_pd.FixedParameters[idx].ModFlags == Parameter.Modifier.PARAMS)
4298                                                 bt = TypeManager.GetElementType (bt);
4299                                 } else {
4300                                         ct = candidate_pd.Types[c_idx];
4301                                         bt = best_pd.Types[b_idx];
4302
4303                                         if (candidate_params && candidate_pd.FixedParameters[c_idx].ModFlags == Parameter.Modifier.PARAMS) {
4304                                                 ct = TypeManager.GetElementType (ct);
4305                                                 --c_idx;
4306                                         }
4307
4308                                         if (best_params && best_pd.FixedParameters[b_idx].ModFlags == Parameter.Modifier.PARAMS) {
4309                                                 bt = TypeManager.GetElementType (bt);
4310                                                 --b_idx;
4311                                         }
4312                                 }
4313
4314                                 if (TypeSpecComparer.IsEqual (ct, bt))
4315                                         continue;
4316
4317                                 same = false;
4318                                 int result = BetterExpressionConversion (ec, a, ct, bt);
4319
4320                                 // for each argument, the conversion to 'ct' should be no worse than
4321                                 // the conversion to 'bt'.
4322                                 if (result == 2)
4323                                         return false;
4324
4325                                 // for at least one argument, the conversion to 'ct' should be better than
4326                                 // the conversion to 'bt'.
4327                                 if (result != 0)
4328                                         better_at_least_one = true;
4329                         }
4330
4331                         if (better_at_least_one)
4332                                 return true;
4333
4334                         //
4335                         // This handles the case
4336                         //
4337                         //   Add (float f1, float f2, float f3);
4338                         //   Add (params decimal [] foo);
4339                         //
4340                         // The call Add (3, 4, 5) should be ambiguous.  Without this check, the
4341                         // first candidate would've chosen as better.
4342                         //
4343                         if (!same && !a.IsDefaultArgument)
4344                                 return false;
4345
4346                         //
4347                         // The two methods have equal non-optional parameter types, apply tie-breaking rules
4348                         //
4349
4350                         //
4351                         // This handles the following cases:
4352                         //
4353                         //  Foo (int i) is better than Foo (int i, long l = 0)
4354                         //  Foo (params int[] args) is better than Foo (int i = 0, params int[] args)
4355                         //  Foo (string s, params string[] args) is better than Foo (params string[] args)
4356                         //
4357                         // Prefer non-optional version
4358                         //
4359                         // LAMESPEC: Specification claims this should be done at last but the opposite is true
4360                         //
4361                         if (candidate_params == best_params && candidate_pd.Count != best_pd.Count) {
4362                                 if (j < candidate_pd.Count && candidate_pd.FixedParameters[j].HasDefaultValue)
4363                                         return false;
4364
4365                                 if (j < best_pd.Count && best_pd.FixedParameters[j].HasDefaultValue)
4366                                         return true;
4367
4368                                 return candidate_pd.Count >= best_pd.Count;
4369                         }
4370
4371                         //
4372                         // One is a non-generic method and second is a generic method, then non-generic is better
4373                         //
4374                         if (best.IsGeneric != candidate.IsGeneric)
4375                                 return best.IsGeneric;
4376
4377                         //
4378                         // This handles the following cases:
4379                         //
4380                         //   Trim () is better than Trim (params char[] chars)
4381                         //   Concat (string s1, string s2, string s3) is better than
4382                         //     Concat (string s1, params string [] srest)
4383                         //   Foo (int, params int [] rest) is better than Foo (params int [] rest)
4384                         //
4385                         // Prefer non-expanded version
4386                         //
4387                         if (candidate_params != best_params)
4388                                 return best_params;
4389
4390                         int candidate_param_count = candidate_pd.Count;
4391                         int best_param_count = best_pd.Count;
4392
4393                         if (candidate_param_count != best_param_count)
4394                                 // can only happen if (candidate_params && best_params)
4395                                 return candidate_param_count > best_param_count && best_pd.HasParams;
4396
4397                         //
4398                         // Both methods have the same number of parameters, and the parameters have equal types
4399                         // Pick the "more specific" signature using rules over original (non-inflated) types
4400                         //
4401                         var candidate_def_pd = ((IParametersMember) candidate.MemberDefinition).Parameters;
4402                         var best_def_pd = ((IParametersMember) best.MemberDefinition).Parameters;
4403
4404                         bool specific_at_least_once = false;
4405                         for (j = 0; j < args_count; ++j) {
4406                                 NamedArgument na = args_count == 0 ? null : args [j] as NamedArgument;
4407                                 if (na != null) {
4408                                         ct = candidate_def_pd.Types[cparam.GetParameterIndexByName (na.Name)];
4409                                         bt = best_def_pd.Types[bparam.GetParameterIndexByName (na.Name)];
4410                                 } else {
4411                                         ct = candidate_def_pd.Types[j];
4412                                         bt = best_def_pd.Types[j];
4413                                 }
4414
4415                                 if (ct == bt)
4416                                         continue;
4417                                 TypeSpec specific = MoreSpecific (ct, bt);
4418                                 if (specific == bt)
4419                                         return false;
4420                                 if (specific == ct)
4421                                         specific_at_least_once = true;
4422                         }
4423
4424                         if (specific_at_least_once)
4425                                 return true;
4426
4427                         return false;
4428                 }
4429
4430                 static bool CheckInflatedArguments (MethodSpec ms)
4431                 {
4432                         if (!TypeParameterSpec.HasAnyTypeParameterTypeConstrained (ms.GenericDefinition))
4433                                 return true;
4434
4435                         // Setup constraint checker for probing only
4436                         ConstraintChecker cc = new ConstraintChecker (null);
4437
4438                         var mp = ms.Parameters.Types;
4439                         for (int i = 0; i < mp.Length; ++i) {
4440                                 var type = mp[i] as InflatedTypeSpec;
4441                                 if (type == null)
4442                                         continue;
4443
4444                                 var targs = type.TypeArguments;
4445                                 if (targs.Length == 0)
4446                                         continue;
4447
4448                                 // TODO: Checking inflated MVAR arguments should be enough
4449                                 if (!cc.CheckAll (type.GetDefinition (), targs, type.Constraints, Location.Null))
4450                                         return false;
4451                         }
4452
4453                         return true;
4454                 }
4455
4456                 public static void Error_ConstructorMismatch (ResolveContext rc, TypeSpec type, int argCount, Location loc)
4457                 {
4458                         rc.Report.Error (1729, loc,
4459                                 "The type `{0}' does not contain a constructor that takes `{1}' arguments",
4460                                 type.GetSignatureForError (), argCount.ToString ());
4461                 }
4462
4463                 //
4464                 // Determines if the candidate method is applicable to the given set of arguments
4465                 // There could be two different set of parameters for same candidate where one
4466                 // is the closest override for default values and named arguments checks and second
4467                 // one being the virtual base for the parameter types and modifiers.
4468                 //
4469                 // A return value rates candidate method compatibility,
4470                 // 0 = the best, int.MaxValue = the worst
4471                 // -1 = fatal error
4472                 //
4473                 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)
4474                 {
4475                         // Parameters of most-derived type used mainly for named and optional parameters
4476                         var pd = pm.Parameters;
4477
4478                         // Used for params modifier only, that's legacy of C# 1.0 which uses base type for
4479                         // params modifier instead of most-derived type
4480                         var cpd = ((IParametersMember) candidate).Parameters;
4481                         int param_count = pd.Count;
4482                         int optional_count = 0;
4483                         int score;
4484                         Arguments orig_args = arguments;
4485
4486                         if (arg_count != param_count) {
4487                                 //
4488                                 // No arguments expansion when doing exact match for delegates
4489                                 //
4490                                 if ((restrictions & Restrictions.CovariantDelegate) == 0) {
4491                                         for (int i = 0; i < pd.Count; ++i) {
4492                                                 if (pd.FixedParameters[i].HasDefaultValue) {
4493                                                         optional_count = pd.Count - i;
4494                                                         break;
4495                                                 }
4496                                         }
4497                                 }
4498
4499                                 if (optional_count != 0) {
4500                                         // Readjust expected number when params used
4501                                         if (cpd.HasParams) {
4502                                                 optional_count--;
4503                                                 if (arg_count < param_count)
4504                                                         param_count--;
4505                                         } else if (arg_count > param_count) {
4506                                                 int args_gap = System.Math.Abs (arg_count - param_count);
4507                                                 return int.MaxValue - 10000 + args_gap;
4508                                         } else if (arg_count < param_count - optional_count) {
4509                                                 int args_gap = System.Math.Abs (param_count - optional_count - arg_count);
4510                                                 return int.MaxValue - 10000 + args_gap;
4511                                         }
4512                                 } else if (arg_count != param_count) {
4513                                         int args_gap = System.Math.Abs (arg_count - param_count);
4514                                         if (!cpd.HasParams)
4515                                                 return int.MaxValue - 10000 + args_gap;
4516                                         if (arg_count < param_count - 1)
4517                                                 return int.MaxValue - 10000 + args_gap;
4518                                 }
4519
4520                                 // Resize to fit optional arguments
4521                                 if (optional_count != 0) {
4522                                         if (arguments == null) {
4523                                                 arguments = new Arguments (optional_count);
4524                                         } else {
4525                                                 // Have to create a new container, so the next run can do same
4526                                                 var resized = new Arguments (param_count);
4527                                                 resized.AddRange (arguments);
4528                                                 arguments = resized;
4529                                         }
4530
4531                                         for (int i = arg_count; i < param_count; ++i)
4532                                                 arguments.Add (null);
4533                                 }
4534                         }
4535
4536                         if (arg_count > 0) {
4537                                 //
4538                                 // Shuffle named arguments to the right positions if there are any
4539                                 //
4540                                 if (arguments[arg_count - 1] is NamedArgument) {
4541                                         arg_count = arguments.Count;
4542
4543                                         for (int i = 0; i < arg_count; ++i) {
4544                                                 bool arg_moved = false;
4545                                                 while (true) {
4546                                                         NamedArgument na = arguments[i] as NamedArgument;
4547                                                         if (na == null)
4548                                                                 break;
4549
4550                                                         int index = pd.GetParameterIndexByName (na.Name);
4551
4552                                                         // Named parameter not found
4553                                                         if (index < 0)
4554                                                                 return (i + 1) * 3;
4555
4556                                                         // already reordered
4557                                                         if (index == i)
4558                                                                 break;
4559
4560                                                         Argument temp;
4561                                                         if (index >= param_count) {
4562                                                                 // When using parameters which should not be available to the user
4563                                                                 if ((cpd.FixedParameters[index].ModFlags & Parameter.Modifier.PARAMS) == 0)
4564                                                                         break;
4565
4566                                                                 arguments.Add (null);
4567                                                                 ++arg_count;
4568                                                                 temp = null;
4569                                                         } else {
4570                                                                 temp = arguments[index];
4571
4572                                                                 // The slot has been taken by positional argument
4573                                                                 if (temp != null && !(temp is NamedArgument))
4574                                                                         break;
4575                                                         }
4576
4577                                                         if (!arg_moved) {
4578                                                                 arguments = arguments.MarkOrderedArgument (na);
4579                                                                 arg_moved = true;
4580                                                         }
4581
4582                                                         if (arguments == orig_args) {
4583                                                                 arguments = new Arguments (orig_args.Count);
4584                                                                 arguments.AddRange (orig_args);
4585                                                         }
4586
4587                                                         arguments[index] = arguments[i];
4588                                                         arguments[i] = temp;
4589
4590                                                         if (temp == null)
4591                                                                 break;
4592                                                 }
4593                                         }
4594                                 } else {
4595                                         arg_count = arguments.Count;
4596                                 }
4597                         } else if (arguments != null) {
4598                                 arg_count = arguments.Count;
4599                         }
4600
4601                         //
4602                         // Don't do any expensive checks when the candidate cannot succeed
4603                         //
4604                         if (arg_count != param_count && !cpd.HasParams)
4605                                 return (param_count - arg_count) * 2 + 1;
4606
4607                         var dep = candidate.GetMissingDependencies ();
4608                         if (dep != null) {
4609                                 ImportedTypeDefinition.Error_MissingDependency (ec, dep, loc);
4610                                 return -1;
4611                         }
4612
4613                         //
4614                         // 1. Handle generic method using type arguments when specified or type inference
4615                         //
4616                         TypeSpec[] ptypes;
4617                         var ms = candidate as MethodSpec;
4618                         if (ms != null && ms.IsGeneric) {
4619                                 if (type_arguments != null) {
4620                                         var g_args_count = ms.Arity;
4621                                         if (g_args_count != type_arguments.Count)
4622                                                 return int.MaxValue - 20000 + System.Math.Abs (type_arguments.Count - g_args_count);
4623
4624                                         ms = ms.MakeGenericMethod (ec, type_arguments.Arguments);
4625                                 } else {
4626                                         //
4627                                         // Deploy custom error reporting for infered anonymous expression or lambda methods. When
4628                                         // probing lambda methods keep all errors reported in separate set and once we are done and no best
4629                                         // candidate was found use the set to report more details about what was wrong with lambda body.
4630                                         // The general idea is to distinguish between code errors and errors caused by
4631                                         // trial-and-error type inference
4632                                         //
4633                                         if (lambda_conv_msgs == null) {
4634                                                 for (int i = 0; i < arg_count; i++) {
4635                                                         Argument a = arguments[i];
4636                                                         if (a == null)
4637                                                                 continue;
4638
4639                                                         var am = a.Expr as AnonymousMethodExpression;
4640                                                         if (am != null) {
4641                                                                 if (lambda_conv_msgs == null)
4642                                                                         lambda_conv_msgs = new SessionReportPrinter ();
4643
4644                                                                 am.TypeInferenceReportPrinter = lambda_conv_msgs;
4645                                                         }
4646                                                 }
4647                                         }
4648
4649                                         var ti = new TypeInference (arguments);
4650                                         TypeSpec[] i_args = ti.InferMethodArguments (ec, ms);
4651
4652                                         if (i_args == null)
4653                                                 return ti.InferenceScore - 20000;
4654
4655                                         //
4656                                         // Clear any error messages when the result was success
4657                                         //
4658                                         if (lambda_conv_msgs != null)
4659                                                 lambda_conv_msgs.ClearSession ();
4660
4661                                         if (i_args.Length != 0) {
4662                                                 ms = ms.MakeGenericMethod (ec, i_args);
4663                                         }
4664                                 }
4665
4666                                 //
4667                                 // Type arguments constraints have to match for the method to be applicable
4668                                 //
4669                                 if (!CheckInflatedArguments (ms)) {
4670                                         candidate = ms;
4671                                         return int.MaxValue - 25000;
4672                                 }
4673
4674                                 //
4675                                 // We have a generic return type and at same time the method is override which
4676                                 // means we have to also inflate override return type in case the candidate is
4677                                 // best candidate and override return type is different to base return type.
4678                                 //
4679                                 // virtual Foo<T, object> with override Foo<T, dynamic>
4680                                 //
4681                                 if (candidate != pm) {
4682                                         MethodSpec override_ms = (MethodSpec) pm;
4683                                         var inflator = new TypeParameterInflator (ec, ms.DeclaringType, override_ms.GenericDefinition.TypeParameters, ms.TypeArguments);
4684                                         returnType = inflator.Inflate (returnType);
4685                                 } else {
4686                                         returnType = ms.ReturnType;
4687                                 }
4688
4689                                 candidate = ms;
4690                                 pd = ms.Parameters;
4691                                 ptypes = pd.Types;
4692                         } else {
4693                                 if (type_arguments != null)
4694                                         return int.MaxValue - 15000;
4695
4696                                 ptypes = cpd.Types;
4697                         }
4698
4699                         //
4700                         // 2. Each argument has to be implicitly convertible to method parameter
4701                         //
4702                         Parameter.Modifier p_mod = 0;
4703                         TypeSpec pt = null;
4704
4705                         for (int i = 0; i < arg_count; i++) {
4706                                 Argument a = arguments[i];
4707                                 if (a == null) {
4708                                         var fp = pd.FixedParameters[i];
4709                                         if (!fp.HasDefaultValue) {
4710                                                 arguments = orig_args;
4711                                                 return arg_count * 2 + 2;
4712                                         }
4713
4714                                         //
4715                                         // Get the default value expression, we can use the same expression
4716                                         // if the type matches
4717                                         //
4718                                         Expression e = fp.DefaultValue;
4719                                         if (e != null) {
4720                                                 e = ResolveDefaultValueArgument (ec, ptypes[i], e, loc);
4721                                                 if (e == null) {
4722                                                         // Restore for possible error reporting
4723                                                         for (int ii = i; ii < arg_count; ++ii)
4724                                                                 arguments.RemoveAt (i);
4725
4726                                                         return (arg_count - i) * 2 + 1;
4727                                                 }
4728                                         }
4729
4730                                         if ((fp.ModFlags & Parameter.Modifier.CallerMask) != 0) {
4731                                                 //
4732                                                 // LAMESPEC: Attributes can be mixed together with build-in priority
4733                                                 //
4734                                                 if ((fp.ModFlags & Parameter.Modifier.CallerLineNumber) != 0) {
4735                                                         e = new IntLiteral (ec.BuiltinTypes, loc.Row, loc);
4736                                                 } else if ((fp.ModFlags & Parameter.Modifier.CallerFilePath) != 0) {
4737                                                         e = new StringLiteral (ec.BuiltinTypes, loc.NameFullPath, loc);
4738                                                 } else if (ec.MemberContext.CurrentMemberDefinition != null) {
4739                                                         e = new StringLiteral (ec.BuiltinTypes, ec.MemberContext.CurrentMemberDefinition.GetCallerMemberName (), loc);
4740                                                 }
4741                                         }
4742
4743                                         arguments[i] = new Argument (e, Argument.AType.Default);
4744                                         continue;
4745                                 }
4746
4747                                 if (p_mod != Parameter.Modifier.PARAMS) {
4748                                         p_mod = (pd.FixedParameters[i].ModFlags & ~Parameter.Modifier.PARAMS) | (cpd.FixedParameters[i].ModFlags & Parameter.Modifier.PARAMS);
4749                                         pt = ptypes [i];
4750                                 } else if (!params_expanded_form) {
4751                                         params_expanded_form = true;
4752                                         pt = ((ElementTypeSpec) pt).Element;
4753                                         i -= 2;
4754                                         continue;
4755                                 }
4756
4757                                 score = 1;
4758                                 if (!params_expanded_form) {
4759                                         if (a.ArgType == Argument.AType.ExtensionType) {
4760                                                 //
4761                                                 // Indentity, implicit reference or boxing conversion must exist for the extension parameter
4762                                                 //
4763                                                 // LAMESPEC: or implicit type parameter conversion
4764                                                 //
4765                                                 var at = a.Type;
4766                                                 if (at == pt || TypeSpecComparer.IsEqual (at, pt) ||
4767                                                         Convert.ImplicitReferenceConversionExists (at, pt, false) ||
4768                                                         Convert.ImplicitBoxingConversion (null, at, pt) != null) {
4769                                                         score = 0;
4770                                                         continue;
4771                                                 }
4772                                         } else {
4773                                                 score = IsArgumentCompatible (ec, a, p_mod, pt);
4774
4775                                                 if (score < 0)
4776                                                         dynamicArgument = true;
4777                                         }
4778                                 }
4779
4780                                 //
4781                                 // It can be applicable in expanded form (when not doing exact match like for delegates)
4782                                 //
4783                                 if (score != 0 && (p_mod & Parameter.Modifier.PARAMS) != 0 && (restrictions & Restrictions.CovariantDelegate) == 0) {
4784                                         if (!params_expanded_form) {
4785                                                 pt = ((ElementTypeSpec) pt).Element;
4786                                         }
4787
4788                                         if (score > 0)
4789                                                 score = IsArgumentCompatible (ec, a, Parameter.Modifier.NONE, pt);
4790
4791                                         if (score < 0) {
4792                                                 params_expanded_form = true;
4793                                                 dynamicArgument = true;
4794                                         } else if (score == 0 || arg_count > pd.Count) {
4795                                                 params_expanded_form = true;
4796                                         }
4797                                 }
4798
4799                                 if (score > 0) {
4800                                         if (params_expanded_form)
4801                                                 ++score;
4802                                         return (arg_count - i) * 2 + score;
4803                                 }
4804                         }
4805
4806                         //
4807                         // When params parameter has no argument it will be provided later if the method is the best candidate
4808                         //
4809                         if (arg_count + 1 == pd.Count && (cpd.FixedParameters [arg_count].ModFlags & Parameter.Modifier.PARAMS) != 0)
4810                                 params_expanded_form = true;
4811
4812                         //
4813                         // Restore original arguments for dynamic binder to keep the intention of original source code
4814                         //
4815                         if (dynamicArgument)
4816                                 arguments = orig_args;
4817
4818                         return 0;
4819                 }
4820
4821                 public static Expression ResolveDefaultValueArgument (ResolveContext ec, TypeSpec ptype, Expression e, Location loc)
4822                 {
4823                         if (e is Constant && e.Type == ptype)
4824                                 return e;
4825
4826                         //
4827                         // LAMESPEC: No idea what the exact rules are for System.Reflection.Missing.Value instead of null
4828                         //
4829                         if (e == EmptyExpression.MissingValue && ptype.BuiltinType == BuiltinTypeSpec.Type.Object || ptype.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
4830                                 e = new MemberAccess (new MemberAccess (new MemberAccess (
4831                                         new QualifiedAliasMember (QualifiedAliasMember.GlobalAlias, "System", loc), "Reflection", loc), "Missing", loc), "Value", loc);
4832                         } else if (e is Constant) {
4833                                 //
4834                                 // Handles int to int? conversions, DefaultParameterValue check
4835                                 //
4836                                 e = Convert.ImplicitConversionStandard (ec, e, ptype, loc);
4837                                 if (e == null)
4838                                         return null;
4839                         } else {
4840                                 e = new DefaultValueExpression (new TypeExpression (ptype, loc), loc);
4841                         }
4842
4843                         return e.Resolve (ec);
4844                 }
4845
4846                 //
4847                 // Tests argument compatibility with the parameter
4848                 // The possible return values are
4849                 // 0 - success
4850                 // 1 - modifier mismatch
4851                 // 2 - type mismatch
4852                 // -1 - dynamic binding required
4853                 //
4854                 int IsArgumentCompatible (ResolveContext ec, Argument argument, Parameter.Modifier param_mod, TypeSpec parameter)
4855                 {
4856                         //
4857                         // Types have to be identical when ref or out modifer
4858                         // is used and argument is not of dynamic type
4859                         //
4860                         if (((argument.Modifier | param_mod) & Parameter.Modifier.RefOutMask) != 0) {
4861                                 if (argument.Type != parameter) {
4862                                         //
4863                                         // Do full equality check after quick path
4864                                         //
4865                                         if (!TypeSpecComparer.IsEqual (argument.Type, parameter)) {
4866                                                 //
4867                                                 // Using dynamic for ref/out parameter can still succeed at runtime
4868                                                 //
4869                                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4870                                                         return -1;
4871
4872                                                 return 2;
4873                                         }
4874                                 }
4875
4876                                 if ((argument.Modifier & Parameter.Modifier.RefOutMask) != (param_mod & Parameter.Modifier.RefOutMask)) {
4877                                         //
4878                                         // Using dynamic for ref/out parameter can still succeed at runtime
4879                                         //
4880                                         if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (argument.Modifier & Parameter.Modifier.RefOutMask) == 0 && (restrictions & Restrictions.CovariantDelegate) == 0)
4881                                                 return -1;
4882
4883                                         return 1;
4884                                 }
4885
4886                         } else {
4887                                 if (argument.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic && (restrictions & Restrictions.CovariantDelegate) == 0)
4888                                         return -1;
4889
4890                                 //
4891                                 // Use implicit conversion in all modes to return same candidates when the expression
4892                                 // is used as argument or delegate conversion
4893                                 //
4894                                 if (!Convert.ImplicitConversionExists (ec, argument.Expr, parameter)) {
4895                                         return parameter.IsDelegate && argument.Expr is AnonymousMethodExpression ? 2 : 3;
4896                                 }
4897                         }
4898
4899                         return 0;
4900                 }
4901
4902                 static TypeSpec MoreSpecific (TypeSpec p, TypeSpec q)
4903                 {
4904                         if (TypeManager.IsGenericParameter (p) && !TypeManager.IsGenericParameter (q))
4905                                 return q;
4906                         if (!TypeManager.IsGenericParameter (p) && TypeManager.IsGenericParameter (q))
4907                                 return p;
4908
4909                         var ac_p = p as ArrayContainer;
4910                         if (ac_p != null) {
4911                                 var ac_q = q as ArrayContainer;
4912                                 if (ac_q == null)
4913                                         return null;
4914
4915                                 TypeSpec specific = MoreSpecific (ac_p.Element, ac_q.Element);
4916                                 if (specific == ac_p.Element)
4917                                         return p;
4918                                 if (specific == ac_q.Element)
4919                                         return q;
4920                         } else if (p.IsGeneric && q.IsGeneric) {
4921                                 var pargs = TypeManager.GetTypeArguments (p);
4922                                 var qargs = TypeManager.GetTypeArguments (q);
4923
4924                                 bool p_specific_at_least_once = false;
4925                                 bool q_specific_at_least_once = false;
4926
4927                                 for (int i = 0; i < pargs.Length; i++) {
4928                                         TypeSpec specific = MoreSpecific (pargs[i], qargs[i]);
4929                                         if (specific == pargs[i])
4930                                                 p_specific_at_least_once = true;
4931                                         if (specific == qargs[i])
4932                                                 q_specific_at_least_once = true;
4933                                 }
4934
4935                                 if (p_specific_at_least_once && !q_specific_at_least_once)
4936                                         return p;
4937                                 if (!p_specific_at_least_once && q_specific_at_least_once)
4938                                         return q;
4939                         }
4940
4941                         return null;
4942                 }
4943
4944                 //
4945                 // Find the best method from candidate list
4946                 //
4947                 public T ResolveMember<T> (ResolveContext rc, ref Arguments args) where T : MemberSpec, IParametersMember
4948                 {
4949                         List<AmbiguousCandidate> ambiguous_candidates = null;
4950
4951                         MemberSpec best_candidate;
4952                         Arguments best_candidate_args = null;
4953                         bool best_candidate_params = false;
4954                         bool best_candidate_dynamic = false;
4955                         int best_candidate_rate;
4956                         IParametersMember best_parameter_member = null;
4957
4958                         int args_count = args != null ? args.Count : 0;
4959
4960                         Arguments candidate_args = args;
4961                         bool error_mode = false;
4962                         MemberSpec invocable_member = null;
4963
4964                         while (true) {
4965                                 best_candidate = null;
4966                                 best_candidate_rate = int.MaxValue;
4967
4968                                 var type_members = members;
4969                                 do {
4970                                         for (int i = 0; i < type_members.Count; ++i) {
4971                                                 var member = type_members[i];
4972
4973                                                 //
4974                                                 // Methods in a base class are not candidates if any method in a derived
4975                                                 // class is applicable
4976                                                 //
4977                                                 if ((member.Modifiers & Modifiers.OVERRIDE) != 0)
4978                                                         continue;
4979
4980                                                 if (!error_mode) {
4981                                                         if (!member.IsAccessible (rc))
4982                                                                 continue;
4983
4984                                                         if (rc.IsRuntimeBinder && !member.DeclaringType.IsAccessible (rc))
4985                                                                 continue;
4986
4987                                                         if ((member.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
4988                                                                 instance_qualifier != null && !instance_qualifier.CheckProtectedMemberAccess (rc, member)) {
4989                                                                 continue;
4990                                                         }
4991                                                 }
4992
4993                                                 IParametersMember pm = member as IParametersMember;
4994                                                 if (pm == null) {
4995                                                         //
4996                                                         // Will use it later to report ambiguity between best method and invocable member
4997                                                         //
4998                                                         if (Invocation.IsMemberInvocable (member))
4999                                                                 invocable_member = member;
5000
5001                                                         continue;
5002                                                 }
5003
5004                                                 //
5005                                                 // Overload resolution is looking for base member but using parameter names
5006                                                 // and default values from the closest member. That means to do expensive lookup
5007                                                 // for the closest override for virtual or abstract members
5008                                                 //
5009                                                 if ((member.Modifiers & (Modifiers.VIRTUAL | Modifiers.ABSTRACT)) != 0) {
5010                                                         var override_params = base_provider.GetOverrideMemberParameters (member);
5011                                                         if (override_params != null)
5012                                                                 pm = override_params;
5013                                                 }
5014
5015                                                 //
5016                                                 // Check if the member candidate is applicable
5017                                                 //
5018                                                 bool params_expanded_form = false;
5019                                                 bool dynamic_argument = false;
5020                                                 TypeSpec rt = pm.MemberType;
5021                                                 int candidate_rate = IsApplicable (rc, ref candidate_args, args_count, ref member, pm, ref params_expanded_form, ref dynamic_argument, ref rt);
5022
5023                                                 if (lambda_conv_msgs != null)
5024                                                         lambda_conv_msgs.EndSession ();
5025
5026                                                 //
5027                                                 // How does it score compare to others
5028                                                 //
5029                                                 if (candidate_rate < best_candidate_rate) {
5030
5031                                                         // Fatal error (missing dependency), cannot continue
5032                                                         if (candidate_rate < 0)
5033                                                                 return null;
5034
5035                                                         best_candidate_rate = candidate_rate;
5036                                                         best_candidate = member;
5037                                                         best_candidate_args = candidate_args;
5038                                                         best_candidate_params = params_expanded_form;
5039                                                         best_candidate_dynamic = dynamic_argument;
5040                                                         best_parameter_member = pm;
5041                                                         best_candidate_return_type = rt;
5042                                                 } else if (candidate_rate == 0) {
5043                                                         //
5044                                                         // The member look is done per type for most operations but sometimes
5045                                                         // it's not possible like for binary operators overload because they
5046                                                         // are unioned between 2 sides
5047                                                         //
5048                                                         if ((restrictions & Restrictions.BaseMembersIncluded) != 0) {
5049                                                                 if (TypeSpec.IsBaseClass (best_candidate.DeclaringType, member.DeclaringType, true))
5050                                                                         continue;
5051                                                         }
5052
5053                                                         bool is_better;
5054                                                         if (best_candidate.DeclaringType.IsInterface && member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5055                                                                 //
5056                                                                 // We pack all interface members into top level type which makes the overload resolution
5057                                                                 // more complicated for interfaces. We compensate it by removing methods with same
5058                                                                 // signature when building the cache hence this path should not really be hit often
5059                                                                 //
5060                                                                 // Example:
5061                                                                 // interface IA { void Foo (int arg); }
5062                                                                 // interface IB : IA { void Foo (params int[] args); }
5063                                                                 //
5064                                                                 // IB::Foo is the best overload when calling IB.Foo (1)
5065                                                                 //
5066                                                                 is_better = true;
5067                                                                 if (ambiguous_candidates != null) {
5068                                                                         foreach (var amb_cand in ambiguous_candidates) {
5069                                                                                 if (member.DeclaringType.ImplementsInterface (best_candidate.DeclaringType, false)) {
5070                                                                                         continue;
5071                                                                                 }
5072
5073                                                                                 is_better = false;
5074                                                                                 break;
5075                                                                         }
5076
5077                                                                         if (is_better)
5078                                                                                 ambiguous_candidates = null;
5079                                                                 }
5080                                                         } else {
5081                                                                 // Is the new candidate better
5082                                                                 is_better = BetterFunction (rc, candidate_args, member, pm.Parameters, params_expanded_form, best_candidate, best_parameter_member.Parameters, best_candidate_params);
5083                                                         }
5084
5085                                                         if (is_better) {
5086                                                                 best_candidate = member;
5087                                                                 best_candidate_args = candidate_args;
5088                                                                 best_candidate_params = params_expanded_form;
5089                                                                 best_candidate_dynamic = dynamic_argument;
5090                                                                 best_parameter_member = pm;
5091                                                                 best_candidate_return_type = rt;
5092                                                         } else {
5093                                                                 // It's not better but any other found later could be but we are not sure yet
5094                                                                 if (ambiguous_candidates == null)
5095                                                                         ambiguous_candidates = new List<AmbiguousCandidate> ();
5096
5097                                                                 ambiguous_candidates.Add (new AmbiguousCandidate (member, pm.Parameters, params_expanded_form));
5098                                                         }
5099                                                 }
5100
5101                                                 // Restore expanded arguments
5102                                                 candidate_args = args;
5103                                         }
5104                                 } while (best_candidate_rate != 0 && (type_members = base_provider.GetBaseMembers (type_members[0].DeclaringType.BaseType)) != null);
5105
5106                                 //
5107                                 // We've found exact match
5108                                 //
5109                                 if (best_candidate_rate == 0)
5110                                         break;
5111
5112                                 //
5113                                 // Try extension methods lookup when no ordinary method match was found and provider enables it
5114                                 //
5115                                 if (!error_mode) {
5116                                         var emg = base_provider.LookupExtensionMethod (rc);
5117                                         if (emg != null) {
5118                                                 emg = emg.OverloadResolve (rc, ref args, null, restrictions);
5119                                                 if (emg != null) {
5120                                                         best_candidate_extension_group = emg;
5121                                                         return (T) (MemberSpec) emg.BestCandidate;
5122                                                 }
5123                                         }
5124                                 }
5125
5126                                 // Don't run expensive error reporting mode for probing
5127                                 if (IsProbingOnly)
5128                                         return null;
5129
5130                                 if (error_mode)
5131                                         break;
5132
5133                                 if (lambda_conv_msgs != null && !lambda_conv_msgs.IsEmpty)
5134                                         break;
5135
5136                                 lambda_conv_msgs = null;
5137                                 error_mode = true;
5138                         }
5139
5140                         //
5141                         // No best member match found, report an error
5142                         //
5143                         if (best_candidate_rate != 0 || error_mode) {
5144                                 ReportOverloadError (rc, best_candidate, best_parameter_member, best_candidate_args, best_candidate_params);
5145                                 return null;
5146                         }
5147
5148                         if (best_candidate_dynamic) {
5149                                 if (args[0].ArgType == Argument.AType.ExtensionType) {
5150                                         rc.Report.Error (1973, loc,
5151                                                 "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",
5152                                                 args [0].Type.GetSignatureForError (), best_candidate.Name, best_candidate.GetSignatureForError ());
5153                                 }
5154
5155                                 //
5156                                 // Check type constraints only when explicit type arguments are used
5157                                 //
5158                                 if (best_candidate.IsGeneric && type_arguments != null) {
5159                                         MethodSpec bc = best_candidate as MethodSpec;
5160                                         if (bc != null && TypeParameterSpec.HasAnyTypeParameterConstrained (bc.GenericDefinition)) {
5161                                                 ConstraintChecker cc = new ConstraintChecker (rc);
5162                                                 cc.CheckAll (bc.GetGenericMethodDefinition (), bc.TypeArguments, bc.Constraints, loc);
5163                                         }
5164                                 }
5165
5166                                 BestCandidateIsDynamic = true;
5167                                 return null;
5168                         }
5169
5170                         //
5171                         // These flags indicates we are running delegate probing conversion. No need to
5172                         // do more expensive checks
5173                         //
5174                         if ((restrictions & (Restrictions.ProbingOnly | Restrictions.CovariantDelegate)) == (Restrictions.CovariantDelegate | Restrictions.ProbingOnly))
5175                                 return (T) best_candidate;
5176
5177                         if (ambiguous_candidates != null) {
5178                                 //
5179                                 // Now check that there are no ambiguities i.e the selected method
5180                                 // should be better than all the others
5181                                 //
5182                                 for (int ix = 0; ix < ambiguous_candidates.Count; ix++) {
5183                                         var candidate = ambiguous_candidates [ix];
5184
5185                                         if (!BetterFunction (rc, best_candidate_args, best_candidate, best_parameter_member.Parameters, best_candidate_params, candidate.Member, candidate.Parameters, candidate.Expanded)) {
5186                                                 var ambiguous = candidate.Member;
5187                                                 if (custom_errors == null || !custom_errors.AmbiguousCandidates (rc, best_candidate, ambiguous)) {
5188                                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
5189                                                         rc.Report.SymbolRelatedToPreviousError (ambiguous);
5190                                                         rc.Report.Error (121, loc, "The call is ambiguous between the following methods or properties: `{0}' and `{1}'",
5191                                                                 best_candidate.GetSignatureForError (), ambiguous.GetSignatureForError ());
5192                                                 }
5193
5194                                                 return (T) best_candidate;
5195                                         }
5196                                 }
5197                         }
5198
5199                         if (invocable_member != null && !IsProbingOnly) {
5200                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5201                                 rc.Report.SymbolRelatedToPreviousError (invocable_member);
5202                                 rc.Report.Warning (467, 2, loc, "Ambiguity between method `{0}' and invocable non-method `{1}'. Using method group",
5203                                         best_candidate.GetSignatureForError (), invocable_member.GetSignatureForError ());
5204                         }
5205
5206                         //
5207                         // And now check if the arguments are all
5208                         // compatible, perform conversions if
5209                         // necessary etc. and return if everything is
5210                         // all right
5211                         //
5212                         if (!VerifyArguments (rc, ref best_candidate_args, best_candidate, best_parameter_member, best_candidate_params))
5213                                 return null;
5214
5215                         if (best_candidate == null)
5216                                 return null;
5217
5218                         //
5219                         // Don't run possibly expensive checks in probing mode
5220                         //
5221                         if (!IsProbingOnly && !rc.IsInProbingMode) {
5222                                 //
5223                                 // Check ObsoleteAttribute on the best method
5224                                 //
5225                                 ObsoleteAttribute oa = best_candidate.GetAttributeObsolete ();
5226                                 if (oa != null && !rc.IsObsolete)
5227                                         AttributeTester.Report_ObsoleteMessage (oa, best_candidate.GetSignatureForError (), loc, rc.Report);
5228
5229                                 best_candidate.MemberDefinition.SetIsUsed ();
5230                         }
5231
5232                         args = best_candidate_args;
5233                         return (T) best_candidate;
5234                 }
5235
5236                 public MethodSpec ResolveOperator (ResolveContext rc, ref Arguments args)
5237                 {
5238                         return ResolveMember<MethodSpec> (rc, ref args);
5239                 }
5240
5241                 void ReportArgumentMismatch (ResolveContext ec, int idx, MemberSpec method,
5242                                                                                                         Argument a, AParametersCollection expected_par, TypeSpec paramType)
5243                 {
5244                         if (custom_errors != null && custom_errors.ArgumentMismatch (ec, method, a, idx))
5245                                 return;
5246
5247                         if (a.Type == InternalType.ErrorType)
5248                                 return;
5249
5250                         if (a is CollectionElementInitializer.ElementInitializerArgument) {
5251                                 ec.Report.SymbolRelatedToPreviousError (method);
5252                                 if ((expected_par.FixedParameters[idx].ModFlags & Parameter.Modifier.RefOutMask) != 0) {
5253                                         ec.Report.Error (1954, loc, "The best overloaded collection initalizer method `{0}' cannot have `ref' or `out' modifier",
5254                                                 TypeManager.CSharpSignature (method));
5255                                         return;
5256                                 }
5257                                 ec.Report.Error (1950, loc, "The best overloaded collection initalizer method `{0}' has some invalid arguments",
5258                                           TypeManager.CSharpSignature (method));
5259                         } else if (IsDelegateInvoke) {
5260                                 ec.Report.Error (1594, loc, "Delegate `{0}' has some invalid arguments",
5261                                         DelegateType.GetSignatureForError ());
5262                         } else {
5263                                 ec.Report.SymbolRelatedToPreviousError (method);
5264                                 ec.Report.Error (1502, loc, "The best overloaded method match for `{0}' has some invalid arguments",
5265                                         method.GetSignatureForError ());
5266                         }
5267
5268                         Parameter.Modifier mod = idx >= expected_par.Count ? 0 : expected_par.FixedParameters[idx].ModFlags;
5269
5270                         string index = (idx + 1).ToString ();
5271                         if (((mod & Parameter.Modifier.RefOutMask) ^ (a.Modifier & Parameter.Modifier.RefOutMask)) != 0) {
5272                                 if ((mod & Parameter.Modifier.RefOutMask) == 0)
5273                                         ec.Report.Error (1615, a.Expr.Location, "Argument `#{0}' does not require `{1}' modifier. Consider removing `{1}' modifier",
5274                                                 index, Parameter.GetModifierSignature (a.Modifier));
5275                                 else
5276                                         ec.Report.Error (1620, a.Expr.Location, "Argument `#{0}' is missing `{1}' modifier",
5277                                                 index, Parameter.GetModifierSignature (mod));
5278                         } else {
5279                                 string p1 = a.GetSignatureForError ();
5280                                 string p2 = paramType.GetSignatureForError ();
5281
5282                                 if (p1 == p2) {
5283                                         p1 = a.Type.GetSignatureForErrorIncludingAssemblyName ();
5284                                         p2 = paramType.GetSignatureForErrorIncludingAssemblyName ();
5285                                 }
5286
5287                                 if ((mod & Parameter.Modifier.RefOutMask) != 0) {
5288                                         p1 = Parameter.GetModifierSignature (a.Modifier) + " " + p1;
5289                                         p2 = Parameter.GetModifierSignature (a.Modifier) + " " + p2;
5290                                 }
5291
5292                                 ec.Report.Error (1503, a.Expr.Location,
5293                                         "Argument `#{0}' cannot convert `{1}' expression to type `{2}'", index, p1, p2);
5294                         }
5295                 }
5296
5297                 //
5298                 // We have failed to find exact match so we return error info about the closest match
5299                 //
5300                 void ReportOverloadError (ResolveContext rc, MemberSpec best_candidate, IParametersMember pm, Arguments args, bool params_expanded)
5301                 {
5302                         int ta_count = type_arguments == null ? 0 : type_arguments.Count;
5303                         int arg_count = args == null ? 0 : args.Count;
5304
5305                         if (ta_count != best_candidate.Arity && (ta_count > 0 || ((IParametersMember) best_candidate).Parameters.IsEmpty)) {
5306                                 var mg = new MethodGroupExpr (new [] { best_candidate }, best_candidate.DeclaringType, loc);
5307                                 mg.Error_TypeArgumentsCannotBeUsed (rc, best_candidate, loc);
5308                                 return;
5309                         }
5310
5311                         if (lambda_conv_msgs != null && lambda_conv_msgs.Merge (rc.Report.Printer)) {
5312                                 return;
5313                         }
5314
5315
5316                         if ((best_candidate.Modifiers & (Modifiers.PROTECTED | Modifiers.STATIC)) == Modifiers.PROTECTED &&
5317                                 InstanceQualifier != null && !InstanceQualifier.CheckProtectedMemberAccess (rc, best_candidate)) {
5318                                 MemberExpr.Error_ProtectedMemberAccess (rc, best_candidate, InstanceQualifier.InstanceType, loc);
5319                         }
5320
5321                         //
5322                         // For candidates which match on parameters count report more details about incorrect arguments
5323                         //
5324                         if (pm != null) {
5325                                 int unexpanded_count = ((IParametersMember) best_candidate).Parameters.HasParams ? pm.Parameters.Count - 1 : pm.Parameters.Count;
5326                                 if (pm.Parameters.Count == arg_count || params_expanded || unexpanded_count == arg_count) {
5327                                         // Reject any inaccessible member
5328                                         if (!best_candidate.IsAccessible (rc) || !best_candidate.DeclaringType.IsAccessible (rc)) {
5329                                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5330                                                 Expression.ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
5331                                                 return;
5332                                         }
5333
5334                                         var ms = best_candidate as MethodSpec;
5335                                         if (ms != null && ms.IsGeneric) {
5336                                                 bool constr_ok = true;
5337                                                 if (ms.TypeArguments != null)
5338                                                         constr_ok = new ConstraintChecker (rc.MemberContext).CheckAll (ms.GetGenericMethodDefinition (), ms.TypeArguments, ms.Constraints, loc);
5339
5340                                                 if (ta_count == 0 && ms.TypeArguments == null) {
5341                                                         if (custom_errors != null && custom_errors.TypeInferenceFailed (rc, best_candidate))
5342                                                                 return;
5343
5344                                                         if (constr_ok) {
5345                                                                 rc.Report.Error (411, loc,
5346                                                                         "The type arguments for method `{0}' cannot be inferred from the usage. Try specifying the type arguments explicitly",
5347                                                                         ms.GetGenericMethodDefinition ().GetSignatureForError ());
5348                                                         }
5349
5350                                                         return;
5351                                                 }
5352                                         }
5353
5354                                         VerifyArguments (rc, ref args, best_candidate, pm, params_expanded);
5355                                         return;
5356                                 }
5357                         }
5358
5359                         //
5360                         // We failed to find any method with correct argument count, report best candidate
5361                         //
5362                         if (custom_errors != null && custom_errors.NoArgumentMatch (rc, best_candidate))
5363                                 return;
5364
5365                         if (best_candidate.Kind == MemberKind.Constructor) {
5366                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5367                                 Error_ConstructorMismatch (rc, best_candidate.DeclaringType, arg_count, loc);
5368                         } else if (IsDelegateInvoke) {
5369                                 rc.Report.SymbolRelatedToPreviousError (DelegateType);
5370                                 rc.Report.Error (1593, loc, "Delegate `{0}' does not take `{1}' arguments",
5371                                         DelegateType.GetSignatureForError (), arg_count.ToString ());
5372                         } else {
5373                                 string name = best_candidate.Kind == MemberKind.Indexer ? "this" : best_candidate.Name;
5374                                 rc.Report.SymbolRelatedToPreviousError (best_candidate);
5375                                 rc.Report.Error (1501, loc, "No overload for method `{0}' takes `{1}' arguments",
5376                                         name, arg_count.ToString ());
5377                         }
5378                 }
5379
5380                 bool VerifyArguments (ResolveContext ec, ref Arguments args, MemberSpec member, IParametersMember pm, bool chose_params_expanded)
5381                 {
5382                         var pd = pm.Parameters;
5383                         TypeSpec[] ptypes = ((IParametersMember) member).Parameters.Types;
5384
5385                         Parameter.Modifier p_mod = 0;
5386                         TypeSpec pt = null;
5387                         int a_idx = 0, a_pos = 0;
5388                         Argument a = null;
5389                         ArrayInitializer params_initializers = null;
5390                         bool has_unsafe_arg = pm.MemberType.IsPointer;
5391                         int arg_count = args == null ? 0 : args.Count;
5392
5393                         for (; a_idx < arg_count; a_idx++, ++a_pos) {
5394                                 a = args[a_idx];
5395                                 if (a == null)
5396                                         continue;
5397
5398                                 if (p_mod != Parameter.Modifier.PARAMS) {
5399                                         p_mod = pd.FixedParameters[a_idx].ModFlags;
5400                                         pt = ptypes[a_idx];
5401                                         has_unsafe_arg |= pt.IsPointer;
5402
5403                                         if (p_mod == Parameter.Modifier.PARAMS) {
5404                                                 if (chose_params_expanded) {
5405                                                         params_initializers = new ArrayInitializer (arg_count - a_idx, a.Expr.Location);
5406                                                         pt = TypeManager.GetElementType (pt);
5407                                                 }
5408                                         }
5409                                 }
5410
5411                                 //
5412                                 // Types have to be identical when ref or out modifer is used
5413                                 //
5414                                 if (((a.Modifier | p_mod) & Parameter.Modifier.RefOutMask) != 0) {
5415                                         if ((a.Modifier & Parameter.Modifier.RefOutMask) != (p_mod & Parameter.Modifier.RefOutMask))
5416                                                 break;
5417
5418                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt))
5419                                                 continue;
5420
5421                                         break;
5422                                 }
5423
5424                                 NamedArgument na = a as NamedArgument;
5425                                 if (na != null) {
5426                                         int name_index = pd.GetParameterIndexByName (na.Name);
5427                                         if (name_index < 0 || name_index >= pd.Count) {
5428                                                 if (IsDelegateInvoke) {
5429                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5430                                                         ec.Report.Error (1746, na.Location,
5431                                                                 "The delegate `{0}' does not contain a parameter named `{1}'",
5432                                                                 DelegateType.GetSignatureForError (), na.Name);
5433                                                 } else {
5434                                                         ec.Report.SymbolRelatedToPreviousError (member);
5435                                                         ec.Report.Error (1739, na.Location,
5436                                                                 "The best overloaded method match for `{0}' does not contain a parameter named `{1}'",
5437                                                                 TypeManager.CSharpSignature (member), na.Name);
5438                                                 }
5439                                         } else if (args[name_index] != a && args[name_index] != null) {
5440                                                 if (IsDelegateInvoke)
5441                                                         ec.Report.SymbolRelatedToPreviousError (DelegateType);
5442                                                 else
5443                                                         ec.Report.SymbolRelatedToPreviousError (member);
5444
5445                                                 ec.Report.Error (1744, na.Location,
5446                                                         "Named argument `{0}' cannot be used for a parameter which has positional argument specified",
5447                                                         na.Name);
5448                                         }
5449                                 }
5450
5451                                 if (a.Expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
5452                                         continue;
5453
5454                                 if ((restrictions & Restrictions.CovariantDelegate) != 0 && !Delegate.IsTypeCovariant (ec, a.Expr.Type, pt)) {
5455                                         custom_errors.NoArgumentMatch (ec, member);
5456                                         return false;
5457                                 }
5458
5459                                 Expression conv;
5460                                 if (a.ArgType == Argument.AType.ExtensionType) {
5461                                         if (a.Expr.Type == pt || TypeSpecComparer.IsEqual (a.Expr.Type, pt)) {
5462                                                 conv = a.Expr;
5463                                         } else {
5464                                                 conv = Convert.ImplicitReferenceConversion (a.Expr, pt, false);
5465                                                 if (conv == null)
5466                                                         conv = Convert.ImplicitBoxingConversion (a.Expr, a.Expr.Type, pt);
5467                                         }
5468                                 } else {
5469                                         conv = Convert.ImplicitConversion (ec, a.Expr, pt, loc);
5470                                 }
5471
5472                                 if (conv == null)
5473                                         break;
5474
5475                                 //
5476                                 // Convert params arguments to an array initializer
5477                                 //
5478                                 if (params_initializers != null) {
5479                                         // we choose to use 'a.Expr' rather than 'conv' so that
5480                                         // we don't hide the kind of expression we have (esp. CompoundAssign.Helper)
5481                                         params_initializers.Add (a.Expr);
5482                                         args.RemoveAt (a_idx--);
5483                                         --arg_count;
5484                                         a.Expr = conv;
5485                                         continue;
5486                                 }
5487
5488                                 // Update the argument with the implicit conversion
5489                                 a.Expr = conv;
5490                         }
5491
5492                         if (a_idx != arg_count) {
5493                                 ReportArgumentMismatch (ec, a_pos, member, a, pd, pt);
5494                                 return false;
5495                         }
5496
5497                         //
5498                         // Fill not provided arguments required by params modifier
5499                         //
5500                         if (params_initializers == null && pd.HasParams && arg_count + 1 == pd.Count) {
5501                                 if (args == null)
5502                                         args = new Arguments (1);
5503
5504                                 pt = ptypes[pd.Count - 1];
5505                                 pt = TypeManager.GetElementType (pt);
5506                                 has_unsafe_arg |= pt.IsPointer;
5507                                 params_initializers = new ArrayInitializer (0, loc);
5508                         }
5509
5510                         //
5511                         // Append an array argument with all params arguments
5512                         //
5513                         if (params_initializers != null) {
5514                                 args.Add (new Argument (
5515                                         new ArrayCreation (new TypeExpression (pt, loc), params_initializers, loc).Resolve (ec)));
5516                                 arg_count++;
5517                         }
5518
5519                         if (has_unsafe_arg && !ec.IsUnsafe) {
5520                                 Expression.UnsafeError (ec, loc);
5521                         }
5522
5523                         //
5524                         // We could infer inaccesible type arguments
5525                         //
5526                         if (type_arguments == null && member.IsGeneric) {
5527                                 var ms = (MethodSpec) member;
5528                                 foreach (var ta in ms.TypeArguments) {
5529                                         if (!ta.IsAccessible (ec)) {
5530                                                 ec.Report.SymbolRelatedToPreviousError (ta);
5531                                                 Expression.ErrorIsInaccesible (ec, member.GetSignatureForError (), loc);
5532                                                 break;
5533                                         }
5534                                 }
5535                         }
5536
5537                         return true;
5538                 }
5539         }
5540
5541         public class ConstantExpr : MemberExpr
5542         {
5543                 readonly ConstSpec constant;
5544
5545                 public ConstantExpr (ConstSpec constant, Location loc)
5546                 {
5547                         this.constant = constant;
5548                         this.loc = loc;
5549                 }
5550
5551                 public override string Name {
5552                         get { throw new NotImplementedException (); }
5553                 }
5554
5555                 public override string KindName {
5556                         get { return "constant"; }
5557                 }
5558
5559                 public override bool IsInstance {
5560                         get { return !IsStatic; }
5561                 }
5562
5563                 public override bool IsStatic {
5564                         get { return true; }
5565                 }
5566
5567                 protected override TypeSpec DeclaringType {
5568                         get { return constant.DeclaringType; }
5569                 }
5570
5571                 public override Expression CreateExpressionTree (ResolveContext ec)
5572                 {
5573                         throw new NotSupportedException ("ET");
5574                 }
5575
5576                 protected override Expression DoResolve (ResolveContext rc)
5577                 {
5578                         ResolveInstanceExpression (rc, null);
5579                         DoBestMemberChecks (rc, constant);
5580
5581                         var c = constant.GetConstant (rc);
5582
5583                         // Creates reference expression to the constant value
5584                         return Constant.CreateConstantFromValue (constant.MemberType, c.GetValue (), loc);
5585                 }
5586
5587                 public override void Emit (EmitContext ec)
5588                 {
5589                         throw new NotSupportedException ();
5590                 }
5591
5592                 public override string GetSignatureForError ()
5593                 {
5594                         return constant.GetSignatureForError ();
5595                 }
5596
5597                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
5598                 {
5599                         Error_TypeArgumentsCannotBeUsed (ec, "constant", GetSignatureForError (), loc);
5600                 }
5601         }
5602
5603         //
5604         // Fully resolved expression that references a Field
5605         //
5606         public class FieldExpr : MemberExpr, IDynamicAssign, IMemoryLocation, IVariableReference
5607         {
5608                 protected FieldSpec spec;
5609                 VariableInfo variable_info;
5610
5611                 LocalTemporary temp;
5612                 bool prepared;
5613
5614                 protected FieldExpr (Location l)
5615                 {
5616                         loc = l;
5617                 }
5618
5619                 public FieldExpr (FieldSpec spec, Location loc)
5620                 {
5621                         this.spec = spec;
5622                         this.loc = loc;
5623
5624                         type = spec.MemberType;
5625                 }
5626
5627                 public FieldExpr (FieldBase fi, Location l)
5628                         : this (fi.Spec, l)
5629                 {
5630                 }
5631
5632                 #region Properties
5633
5634                 public override string Name {
5635                         get {
5636                                 return spec.Name;
5637                         }
5638                 }
5639
5640                 public bool IsHoisted {
5641                         get {
5642                                 IVariableReference hv = InstanceExpression as IVariableReference;
5643                                 return hv != null && hv.IsHoisted;
5644                         }
5645                 }
5646
5647                 public override bool IsInstance {
5648                         get {
5649                                 return !spec.IsStatic;
5650                         }
5651                 }
5652
5653                 public override bool IsStatic {
5654                         get {
5655                                 return spec.IsStatic;
5656                         }
5657                 }
5658
5659                 public override string KindName {
5660                         get { return "field"; }
5661                 }
5662
5663                 public FieldSpec Spec {
5664                         get {
5665                                 return spec;
5666                         }
5667                 }
5668
5669                 protected override TypeSpec DeclaringType {
5670                         get {
5671                                 return spec.DeclaringType;
5672                         }
5673                 }
5674
5675                 public VariableInfo VariableInfo {
5676                         get {
5677                                 return variable_info;
5678                         }
5679                 }
5680
5681 #endregion
5682
5683                 public override string GetSignatureForError ()
5684                 {
5685                         return spec.GetSignatureForError ();
5686                 }
5687
5688                 public bool IsMarshalByRefAccess (ResolveContext rc)
5689                 {
5690                         // Checks possible ldflda of field access expression
5691                         return !spec.IsStatic && TypeSpec.IsValueType (spec.MemberType) && !(InstanceExpression is This) &&
5692                                 rc.Module.PredefinedTypes.MarshalByRefObject.Define () &&
5693                                 TypeSpec.IsBaseClass (spec.DeclaringType, rc.Module.PredefinedTypes.MarshalByRefObject.TypeSpec, false);
5694                 }
5695
5696                 public void SetHasAddressTaken ()
5697                 {
5698                         IVariableReference vr = InstanceExpression as IVariableReference;
5699                         if (vr != null) {
5700                                 vr.SetHasAddressTaken ();
5701                         }
5702                 }
5703
5704                 public override Expression CreateExpressionTree (ResolveContext ec)
5705                 {
5706                         return CreateExpressionTree (ec, true);
5707                 }
5708
5709                 public Expression CreateExpressionTree (ResolveContext ec, bool convertInstance)
5710                 {
5711                         Arguments args;
5712                         Expression instance;
5713
5714                         if (InstanceExpression == null) {
5715                                 instance = new NullLiteral (loc);
5716                         } else if (convertInstance) {
5717                                 instance = InstanceExpression.CreateExpressionTree (ec);
5718                         } else {
5719                                 args = new Arguments (1);
5720                                 args.Add (new Argument (InstanceExpression));
5721                                 instance = CreateExpressionFactoryCall (ec, "Constant", args);
5722                         }
5723
5724                         args = Arguments.CreateForExpressionTree (ec, null,
5725                                 instance,
5726                                 CreateTypeOfExpression ());
5727
5728                         return CreateExpressionFactoryCall (ec, "Field", args);
5729                 }
5730
5731                 public Expression CreateTypeOfExpression ()
5732                 {
5733                         return new TypeOfField (spec, loc);
5734                 }
5735
5736                 protected override Expression DoResolve (ResolveContext ec)
5737                 {
5738                         spec.MemberDefinition.SetIsUsed ();
5739
5740                         return DoResolve (ec, null);
5741                 }
5742
5743                 Expression DoResolve (ResolveContext ec, Expression rhs)
5744                 {
5745                         bool lvalue_instance = rhs != null && IsInstance && spec.DeclaringType.IsStruct;
5746
5747                         if (rhs != this) {
5748                                 if (ResolveInstanceExpression (ec, rhs)) {
5749                                         // Resolve the field's instance expression while flow analysis is turned
5750                                         // off: when accessing a field "a.b", we must check whether the field
5751                                         // "a.b" is initialized, not whether the whole struct "a" is initialized.
5752
5753                                         if (lvalue_instance) {
5754                                                 bool out_access = rhs == EmptyExpression.OutAccess || rhs == EmptyExpression.LValueMemberOutAccess;
5755
5756                                                 Expression right_side =
5757                                                         out_access ? EmptyExpression.LValueMemberOutAccess : EmptyExpression.LValueMemberAccess;
5758
5759                                                 InstanceExpression = InstanceExpression.ResolveLValue (ec, right_side);
5760                                         } else {
5761                                                 InstanceExpression = InstanceExpression.Resolve (ec, ResolveFlags.VariableOrValue);
5762                                         }
5763
5764                                         if (InstanceExpression == null)
5765                                                 return null;
5766                                 }
5767
5768                                 DoBestMemberChecks (ec, spec);
5769                         }
5770
5771                         var fb = spec as FixedFieldSpec;
5772                         IVariableReference var = InstanceExpression as IVariableReference;
5773
5774                         if (fb != null) {
5775                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5776                                 if (!ec.HasSet (ResolveContext.Options.FixedInitializerScope) && (fe == null || !fe.IsFixed)) {
5777                                         ec.Report.Error (1666, loc, "You cannot use fixed size buffers contained in unfixed expressions. Try using the fixed statement");
5778                                 }
5779
5780                                 if (InstanceExpression.eclass != ExprClass.Variable) {
5781                                         ec.Report.SymbolRelatedToPreviousError (spec);
5782                                         ec.Report.Error (1708, loc, "`{0}': Fixed size buffers can only be accessed through locals or fields",
5783                                                 TypeManager.GetFullNameSignature (spec));
5784                                 } else if (var != null && var.IsHoisted) {
5785                                         AnonymousMethodExpression.Error_AddressOfCapturedVar (ec, var, loc);
5786                                 }
5787
5788                                 return new FixedBufferPtr (this, fb.ElementType, loc).Resolve (ec);
5789                         }
5790
5791                         //
5792                         // Set flow-analysis variable info for struct member access. It will be check later
5793                         // for precise error reporting
5794                         //
5795                         if (var != null && var.VariableInfo != null && InstanceExpression.Type.IsStruct) {
5796                                 variable_info = var.VariableInfo.GetStructFieldInfo (Name);
5797                         }
5798
5799                         eclass = ExprClass.Variable;
5800                         return this;
5801                 }
5802
5803                 public void SetFieldAssigned (FlowAnalysisContext fc)
5804                 {
5805                         if (!IsInstance)
5806                                 return;
5807
5808                         bool lvalue_instance = spec.DeclaringType.IsStruct;
5809                         if (lvalue_instance) {
5810                                 var var = InstanceExpression as IVariableReference;
5811                                 if (var != null && var.VariableInfo != null) {
5812                                         fc.SetStructFieldAssigned (var.VariableInfo, Name);
5813                                 }
5814                         }
5815
5816                         var fe = InstanceExpression as FieldExpr;
5817                         if (fe != null) {
5818                                 Expression instance;
5819
5820                                 do {
5821                                         instance = fe.InstanceExpression;
5822                                         var fe_instance = instance as FieldExpr;
5823                                         if ((fe_instance != null && !fe_instance.IsStatic) || instance is LocalVariableReference) {
5824                                                 if (TypeSpec.IsReferenceType (fe.Type) && instance.Type.IsStruct) {
5825                                                         var var = InstanceExpression as IVariableReference;
5826                                                         if (var != null && var.VariableInfo == null) {
5827                                                                 var var_inst = instance as IVariableReference;
5828                                                                 if (var_inst == null || (var_inst.VariableInfo != null && !fc.IsDefinitelyAssigned (var_inst.VariableInfo)))
5829                                                                         fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5830                                                         }
5831                                                 }
5832
5833                                                 if (fe_instance != null) {
5834                                                         fe = fe_instance;
5835                                                         continue;
5836                                                 }
5837                                         }
5838
5839                                         break;
5840                                 } while (true);
5841
5842                                 if (instance != null && TypeSpec.IsReferenceType (instance.Type))
5843                                         instance.FlowAnalysis (fc);
5844                         } else {
5845                                 if (TypeSpec.IsReferenceType (InstanceExpression.Type))
5846                                         InstanceExpression.FlowAnalysis (fc);
5847                         }
5848                 }
5849
5850
5851                 public void VerifyAssignedStructField (FlowAnalysisContext fc)
5852                 {
5853                         var fe = this;
5854
5855                         do {
5856                                 var var = fe.InstanceExpression as IVariableReference;
5857                                 if (var != null) {
5858                                         var vi = var.VariableInfo;
5859
5860                                         if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, fe.Name) && !fe.type.IsStruct) {
5861                                                 fc.Report.Warning (1060, 1, fe.loc, "Use of possibly unassigned field `{0}'", fe.Name);
5862                                         }
5863                                 }
5864
5865                                 fe = fe.InstanceExpression as FieldExpr;
5866
5867                         } while (fe != null);
5868                 }
5869
5870                 Expression Error_AssignToReadonly (ResolveContext rc, Expression right_side)
5871                 {
5872                         // The return value is always null.  Returning a value simplifies calling code.
5873
5874                         if (right_side == EmptyExpression.OutAccess) {
5875                                 if (IsStatic) {
5876                                         rc.Report.Error (199, loc, "A static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5877                                                 GetSignatureForError ());
5878                                 } else {
5879                                         rc.Report.Error (192, loc, "A readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5880                                                 GetSignatureForError ());
5881                                 }
5882
5883                                 return null;
5884                         }
5885
5886                         if (right_side == EmptyExpression.LValueMemberAccess) {
5887                                 // Already reported as CS1648/CS1650
5888                                 return null;
5889                         }
5890
5891                         if (right_side == EmptyExpression.LValueMemberOutAccess) {
5892                                 if (IsStatic) {
5893                                         rc.Report.Error (1651, loc, "Fields of static readonly field `{0}' cannot be passed ref or out (except in a static constructor)",
5894                                                 GetSignatureForError ());
5895                                 } else {
5896                                         rc.Report.Error (1649, loc, "Members of readonly field `{0}' cannot be passed ref or out (except in a constructor)",
5897                                                 GetSignatureForError ());
5898                                 }
5899                                 return null;
5900                         }
5901
5902                         if (IsStatic) {
5903                                 rc.Report.Error (198, loc, "A static readonly field `{0}' cannot be assigned to (except in a static constructor or a variable initializer)",
5904                                         GetSignatureForError ());
5905                         } else {
5906                                 rc.Report.Error (191, loc, "A readonly field `{0}' cannot be assigned to (except in a constructor or a variable initializer)",
5907                                         GetSignatureForError ());
5908                         }
5909
5910                         return null;
5911                 }
5912
5913                 override public Expression DoResolveLValue (ResolveContext ec, Expression right_side)
5914                 {
5915                         if (spec is FixedFieldSpec) {
5916                                 // It could be much better error message but we want to be error compatible
5917                                 Error_ValueAssignment (ec, right_side);
5918                         }
5919
5920                         Expression e = DoResolve (ec, right_side);
5921
5922                         if (e == null)
5923                                 return null;
5924
5925                         spec.MemberDefinition.SetIsAssigned ();
5926
5927                         if ((right_side == EmptyExpression.UnaryAddress || right_side == EmptyExpression.OutAccess) &&
5928                                         (spec.Modifiers & Modifiers.VOLATILE) != 0) {
5929                                 ec.Report.Warning (420, 1, loc,
5930                                         "`{0}': A volatile field references will not be treated as volatile",
5931                                         spec.GetSignatureForError ());
5932                         }
5933
5934                         if (spec.IsReadOnly) {
5935                                 // InitOnly fields can only be assigned in constructors or initializers
5936                                 if (!ec.HasAny (ResolveContext.Options.FieldInitializerScope | ResolveContext.Options.ConstructorScope))
5937                                         return Error_AssignToReadonly (ec, right_side);
5938
5939                                 if (ec.HasSet (ResolveContext.Options.ConstructorScope)) {
5940
5941                                         // InitOnly fields cannot be assigned-to in a different constructor from their declaring type
5942                                         if (ec.CurrentMemberDefinition.Parent.PartialContainer.Definition != spec.DeclaringType.GetDefinition ())
5943                                                 return Error_AssignToReadonly (ec, right_side);
5944                                         // static InitOnly fields cannot be assigned-to in an instance constructor
5945                                         if (IsStatic && !ec.IsStatic)
5946                                                 return Error_AssignToReadonly (ec, right_side);
5947                                         // instance constructors can't modify InitOnly fields of other instances of the same type
5948                                         if (!IsStatic && !(InstanceExpression is This))
5949                                                 return Error_AssignToReadonly (ec, right_side);
5950                                 }
5951                         }
5952
5953                         if (right_side == EmptyExpression.OutAccess && IsMarshalByRefAccess (ec)) {
5954                                 ec.Report.SymbolRelatedToPreviousError (spec.DeclaringType);
5955                                 ec.Report.Warning (197, 1, loc,
5956                                                 "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",
5957                                                 GetSignatureForError ());
5958                         }
5959
5960                         eclass = ExprClass.Variable;
5961                         return this;
5962                 }
5963
5964                 public override void FlowAnalysis (FlowAnalysisContext fc)
5965                 {
5966                         var var = InstanceExpression as IVariableReference;
5967                         if (var != null) {
5968                                 var vi = var.VariableInfo;
5969                                 if (vi != null && !fc.IsStructFieldDefinitelyAssigned (vi, Name)) {
5970                                         fc.Report.Error (170, loc, "Use of possibly unassigned field `{0}'", Name);
5971                                         return;
5972                                 }
5973
5974                                 if (TypeSpec.IsValueType (InstanceExpression.Type))
5975                                         return;
5976                         }
5977
5978                         base.FlowAnalysis (fc);
5979                 }
5980
5981                 public override int GetHashCode ()
5982                 {
5983                         return spec.GetHashCode ();
5984                 }
5985
5986                 public bool IsFixed {
5987                         get {
5988                                 //
5989                                 // A variable of the form V.I is fixed when V is a fixed variable of a struct type
5990                                 //
5991                                 IVariableReference variable = InstanceExpression as IVariableReference;
5992                                 if (variable != null)
5993                                         return InstanceExpression.Type.IsStruct && variable.IsFixed;
5994
5995                                 IFixedExpression fe = InstanceExpression as IFixedExpression;
5996                                 return fe != null && fe.IsFixed;
5997                         }
5998                 }
5999
6000                 public override bool Equals (object obj)
6001                 {
6002                         FieldExpr fe = obj as FieldExpr;
6003                         if (fe == null)
6004                                 return false;
6005
6006                         if (spec != fe.spec)
6007                                 return false;
6008
6009                         if (InstanceExpression == null || fe.InstanceExpression == null)
6010                                 return true;
6011
6012                         return InstanceExpression.Equals (fe.InstanceExpression);
6013                 }
6014
6015                 public void Emit (EmitContext ec, bool leave_copy)
6016                 {
6017                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6018
6019                         if (IsStatic){
6020                                 if (is_volatile)
6021                                         ec.Emit (OpCodes.Volatile);
6022
6023                                 ec.Emit (OpCodes.Ldsfld, spec);
6024                         } else {
6025                                 if (!prepared)
6026                                         EmitInstance (ec, false);
6027
6028                                 // Optimization for build-in types
6029                                 if (type.IsStruct && type == ec.CurrentType && InstanceExpression.Type == type) {
6030                                         ec.EmitLoadFromPtr (type);
6031                                 } else {
6032                                         var ff = spec as FixedFieldSpec;
6033                                         if (ff != null) {
6034                                                 ec.Emit (OpCodes.Ldflda, spec);
6035                                                 ec.Emit (OpCodes.Ldflda, ff.Element);
6036                                         } else {
6037                                                 if (is_volatile)
6038                                                         ec.Emit (OpCodes.Volatile);
6039
6040                                                 ec.Emit (OpCodes.Ldfld, spec);
6041                                         }
6042                                 }
6043                         }
6044
6045                         if (leave_copy) {
6046                                 ec.Emit (OpCodes.Dup);
6047                                 if (!IsStatic) {
6048                                         temp = new LocalTemporary (this.Type);
6049                                         temp.Store (ec);
6050                                 }
6051                         }
6052                 }
6053
6054                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6055                 {
6056                         bool has_await_source = ec.HasSet (BuilderContext.Options.AsyncBody) && source.ContainsEmitWithAwait ();
6057                         if (isCompound && !(source is DynamicExpressionStatement)) {
6058                                 if (has_await_source) {
6059                                         if (IsInstance)
6060                                                 InstanceExpression = InstanceExpression.EmitToField (ec);
6061                                 } else {
6062                                         prepared = true;
6063                                 }
6064                         }
6065
6066                         if (IsInstance) {
6067                                 if (has_await_source)
6068                                         source = source.EmitToField (ec);
6069
6070                                 EmitInstance (ec, prepared);
6071                         }
6072
6073                         source.Emit (ec);
6074
6075                         if (leave_copy) {
6076                                 ec.Emit (OpCodes.Dup);
6077                                 if (!IsStatic) {
6078                                         temp = new LocalTemporary (this.Type);
6079                                         temp.Store (ec);
6080                                 }
6081                         }
6082
6083                         if ((spec.Modifiers & Modifiers.VOLATILE) != 0)
6084                                 ec.Emit (OpCodes.Volatile);
6085
6086                         spec.MemberDefinition.SetIsAssigned ();
6087
6088                         if (IsStatic)
6089                                 ec.Emit (OpCodes.Stsfld, spec);
6090                         else
6091                                 ec.Emit (OpCodes.Stfld, spec);
6092
6093                         if (temp != null) {
6094                                 temp.Emit (ec);
6095                                 temp.Release (ec);
6096                                 temp = null;
6097                         }
6098                 }
6099
6100                 //
6101                 // Emits store to field with prepared values on stack
6102                 //
6103                 public void EmitAssignFromStack (EmitContext ec)
6104                 {
6105                         if (IsStatic) {
6106                                 ec.Emit (OpCodes.Stsfld, spec);
6107                         } else {
6108                                 ec.Emit (OpCodes.Stfld, spec);
6109                         }
6110                 }
6111
6112                 public override void Emit (EmitContext ec)
6113                 {
6114                         Emit (ec, false);
6115                 }
6116
6117                 public override void EmitSideEffect (EmitContext ec)
6118                 {
6119                         bool is_volatile = (spec.Modifiers & Modifiers.VOLATILE) != 0;
6120
6121                         if (is_volatile) // || is_marshal_by_ref ())
6122                                 base.EmitSideEffect (ec);
6123                 }
6124
6125                 public virtual void AddressOf (EmitContext ec, AddressOp mode)
6126                 {
6127                         if ((mode & AddressOp.Store) != 0)
6128                                 spec.MemberDefinition.SetIsAssigned ();
6129                         if ((mode & AddressOp.Load) != 0)
6130                                 spec.MemberDefinition.SetIsUsed ();
6131
6132                         //
6133                         // Handle initonly fields specially: make a copy and then
6134                         // get the address of the copy.
6135                         //
6136                         bool need_copy;
6137                         if (spec.IsReadOnly){
6138                                 need_copy = true;
6139                                 if (ec.HasSet (EmitContext.Options.ConstructorScope) && spec.DeclaringType == ec.CurrentType) {
6140                                         if (IsStatic){
6141                                                 if (ec.IsStatic)
6142                                                         need_copy = false;
6143                                         } else
6144                                                 need_copy = false;
6145                                 }
6146                         } else
6147                                 need_copy = false;
6148
6149                         if (need_copy) {
6150                                 Emit (ec);
6151                                 var temp = ec.GetTemporaryLocal (type);
6152                                 ec.Emit (OpCodes.Stloc, temp);
6153                                 ec.Emit (OpCodes.Ldloca, temp);
6154                                 ec.FreeTemporaryLocal (temp, type);
6155                                 return;
6156                         }
6157
6158
6159                         if (IsStatic){
6160                                 ec.Emit (OpCodes.Ldsflda, spec);
6161                         } else {
6162                                 if (!prepared)
6163                                         EmitInstance (ec, false);
6164                                 ec.Emit (OpCodes.Ldflda, spec);
6165                         }
6166                 }
6167
6168                 public SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6169                 {
6170                         return MakeExpression (ctx);
6171                 }
6172
6173                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6174                 {
6175 #if STATIC
6176                         return base.MakeExpression (ctx);
6177 #else
6178                         return SLE.Expression.Field (
6179                                 IsStatic ? null : InstanceExpression.MakeExpression (ctx),
6180                                 spec.GetMetaInfo ());
6181 #endif
6182                 }
6183
6184                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6185                 {
6186                         Error_TypeArgumentsCannotBeUsed (ec, "field", GetSignatureForError (), loc);
6187                 }
6188         }
6189
6190
6191         //
6192         // Expression that evaluates to a Property.
6193         //
6194         // This is not an LValue because we need to re-write the expression. We
6195         // can not take data from the stack and store it.
6196         //
6197         sealed class PropertyExpr : PropertyOrIndexerExpr<PropertySpec>
6198         {
6199                 Arguments arguments;
6200
6201                 public PropertyExpr (PropertySpec spec, Location l)
6202                         : base (l)
6203                 {
6204                         best_candidate = spec;
6205                         type = spec.MemberType;
6206                 }
6207
6208                 #region Properties
6209
6210                 protected override Arguments Arguments {
6211                         get {
6212                                 return arguments;
6213                         }
6214                         set {
6215                                 arguments = value;
6216                         }
6217                 }
6218
6219                 protected override TypeSpec DeclaringType {
6220                         get {
6221                                 return best_candidate.DeclaringType;
6222                         }
6223                 }
6224
6225                 public override string Name {
6226                         get {
6227                                 return best_candidate.Name;
6228                         }
6229                 }
6230
6231                 public override bool IsInstance {
6232                         get {
6233                                 return !IsStatic;
6234                         }
6235                 }
6236
6237                 public override bool IsStatic {
6238                         get {
6239                                 return best_candidate.IsStatic;
6240                         }
6241                 }
6242
6243                 public override string KindName {
6244                         get { return "property"; }
6245                 }
6246
6247                 public PropertySpec PropertyInfo {
6248                         get {
6249                                 return best_candidate;
6250                         }
6251                 }
6252
6253                 #endregion
6254
6255                 public override MethodGroupExpr CanReduceLambda (AnonymousMethodBody body)
6256                 {
6257                         if (best_candidate == null || !(best_candidate.IsStatic || InstanceExpression is This))
6258                                 return null;
6259
6260                         var args_count = arguments == null ? 0 : arguments.Count;
6261                         if (args_count != body.Parameters.Count && args_count == 0)
6262                                 return null;
6263
6264                         var mg = MethodGroupExpr.CreatePredefined (best_candidate.Get, DeclaringType, loc);
6265                         mg.InstanceExpression = InstanceExpression;
6266
6267                         return mg;
6268                 }
6269
6270                 public static PropertyExpr CreatePredefined (PropertySpec spec, Location loc)
6271                 {
6272                         return new PropertyExpr (spec, loc) {
6273                                 Getter = spec.Get,
6274                                 Setter = spec.Set
6275                         };
6276                 }
6277
6278                 public override Expression CreateExpressionTree (ResolveContext ec)
6279                 {
6280                         Arguments args;
6281                         if (IsSingleDimensionalArrayLength ()) {
6282                                 args = new Arguments (1);
6283                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6284                                 return CreateExpressionFactoryCall (ec, "ArrayLength", args);
6285                         }
6286
6287                         args = new Arguments (2);
6288                         if (InstanceExpression == null)
6289                                 args.Add (new Argument (new NullLiteral (loc)));
6290                         else
6291                                 args.Add (new Argument (InstanceExpression.CreateExpressionTree (ec)));
6292                         args.Add (new Argument (new TypeOfMethod (Getter, loc)));
6293                         return CreateExpressionFactoryCall (ec, "Property", args);
6294                 }
6295
6296                 public Expression CreateSetterTypeOfExpression (ResolveContext rc)
6297                 {
6298                         DoResolveLValue (rc, null);
6299                         return new TypeOfMethod (Setter, loc);
6300                 }
6301
6302                 public override string GetSignatureForError ()
6303                 {
6304                         return best_candidate.GetSignatureForError ();
6305                 }
6306
6307                 public override SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source)
6308                 {
6309 #if STATIC
6310                         return base.MakeExpression (ctx);
6311 #else
6312                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Setter.GetMetaInfo ());
6313 #endif
6314                 }
6315
6316                 public override SLE.Expression MakeExpression (BuilderContext ctx)
6317                 {
6318 #if STATIC
6319                         return base.MakeExpression (ctx);
6320 #else
6321                         return SLE.Expression.Property (InstanceExpression.MakeExpression (ctx), (MethodInfo) Getter.GetMetaInfo ());
6322 #endif
6323                 }
6324
6325                 void Error_PropertyNotValid (ResolveContext ec)
6326                 {
6327                         ec.Report.SymbolRelatedToPreviousError (best_candidate);
6328                         ec.Report.Error (1546, loc, "Property or event `{0}' is not supported by the C# language",
6329                                 GetSignatureForError ());
6330                 }
6331
6332                 bool IsSingleDimensionalArrayLength ()
6333                 {
6334                         if (best_candidate.DeclaringType.BuiltinType != BuiltinTypeSpec.Type.Array || !best_candidate.HasGet || Name != "Length")
6335                                 return false;
6336
6337                         ArrayContainer ac = InstanceExpression.Type as ArrayContainer;
6338                         return ac != null && ac.Rank == 1;
6339                 }
6340
6341                 public override void Emit (EmitContext ec, bool leave_copy)
6342                 {
6343                         //
6344                         // Special case: length of single dimension array property is turned into ldlen
6345                         //
6346                         if (IsSingleDimensionalArrayLength ()) {
6347                                 EmitInstance (ec, false);
6348                                 ec.Emit (OpCodes.Ldlen);
6349                                 ec.Emit (OpCodes.Conv_I4);
6350                                 return;
6351                         }
6352
6353                         base.Emit (ec, leave_copy);
6354                 }
6355
6356                 public override void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6357                 {
6358                         Arguments args;
6359                         LocalTemporary await_source_arg = null;
6360
6361                         if (isCompound && !(source is DynamicExpressionStatement)) {
6362                                 emitting_compound_assignment = true;
6363                                 source.Emit (ec);
6364
6365                                 if (has_await_arguments) {
6366                                         await_source_arg = new LocalTemporary (Type);
6367                                         await_source_arg.Store (ec);
6368
6369                                         args = new Arguments (1);
6370                                         args.Add (new Argument (await_source_arg));
6371
6372                                         if (leave_copy) {
6373                                                 temp = await_source_arg;
6374                                         }
6375
6376                                         has_await_arguments = false;
6377                                 } else {
6378                                         args = null;
6379
6380                                         if (leave_copy) {
6381                                                 ec.Emit (OpCodes.Dup);
6382                                                 temp = new LocalTemporary (this.Type);
6383                                                 temp.Store (ec);
6384                                         }
6385                                 }
6386                         } else {
6387                                 args = arguments ?? new Arguments (1);
6388
6389                                 if (leave_copy) {
6390                                         source.Emit (ec);
6391                                         temp = new LocalTemporary (this.Type);
6392                                         temp.Store (ec);
6393                                         args.Add (new Argument (temp));
6394                                 } else {
6395                                         args.Add (new Argument (source));
6396                                 }
6397                         }
6398
6399                         emitting_compound_assignment = false;
6400
6401                         var call = new CallEmitter ();
6402                         call.InstanceExpression = InstanceExpression;
6403                         if (args == null)
6404                                 call.InstanceExpressionOnStack = true;
6405
6406                         call.Emit (ec, Setter, args, loc);
6407
6408                         if (temp != null) {
6409                                 temp.Emit (ec);
6410                                 temp.Release (ec);
6411                         }
6412
6413                         if (await_source_arg != null) {
6414                                 await_source_arg.Release (ec);
6415                         }
6416                 }
6417
6418                 protected override Expression OverloadResolve (ResolveContext rc, Expression right_side)
6419                 {
6420                         eclass = ExprClass.PropertyAccess;
6421
6422                         if (best_candidate.IsNotCSharpCompatible) {
6423                                 Error_PropertyNotValid (rc);
6424                         }
6425
6426                         ResolveInstanceExpression (rc, right_side);
6427
6428                         if ((best_candidate.Modifiers & (Modifiers.ABSTRACT | Modifiers.VIRTUAL)) != 0 && best_candidate.DeclaringType != InstanceExpression.Type) {
6429                                 var filter = new MemberFilter (best_candidate.Name, 0, MemberKind.Property, null, null);
6430                                 var p = MemberCache.FindMember (InstanceExpression.Type, filter, BindingRestriction.InstanceOnly | BindingRestriction.OverrideOnly) as PropertySpec;
6431                                 if (p != null) {
6432                                         type = p.MemberType;
6433                                 }
6434                         }
6435
6436                         DoBestMemberChecks (rc, best_candidate);
6437
6438                         // Handling of com-imported properties with any number of default property parameters
6439                         if (best_candidate.HasGet && !best_candidate.Get.Parameters.IsEmpty) {
6440                                 var p = best_candidate.Get.Parameters;
6441                                 arguments = new Arguments (p.Count);
6442                                 for (int i = 0; i < p.Count; ++i) {
6443                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6444                                 }
6445                         } else if (best_candidate.HasSet && best_candidate.Set.Parameters.Count > 1) {
6446                                 var p = best_candidate.Set.Parameters;
6447                                 arguments = new Arguments (p.Count - 1);
6448                                 for (int i = 0; i < p.Count - 1; ++i) {
6449                                         arguments.Add (new Argument (OverloadResolver.ResolveDefaultValueArgument (rc, p.Types [i], p.FixedParameters [i].DefaultValue, loc)));
6450                                 }
6451                         }
6452
6453                         return this;
6454                 }
6455
6456                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6457                 {
6458                         Error_TypeArgumentsCannotBeUsed (ec, "property", GetSignatureForError (), loc);
6459                 }
6460         }
6461
6462         abstract class PropertyOrIndexerExpr<T> : MemberExpr, IDynamicAssign where T : PropertySpec
6463         {
6464                 // getter and setter can be different for base calls
6465                 MethodSpec getter, setter;
6466                 protected T best_candidate;
6467
6468                 protected LocalTemporary temp;
6469                 protected bool emitting_compound_assignment;
6470                 protected bool has_await_arguments;
6471
6472                 protected PropertyOrIndexerExpr (Location l)
6473                 {
6474                         loc = l;
6475                 }
6476
6477                 #region Properties
6478
6479                 protected abstract Arguments Arguments { get; set; }
6480
6481                 public MethodSpec Getter {
6482                         get {
6483                                 return getter;
6484                         }
6485                         set {
6486                                 getter = value;
6487                         }
6488                 }
6489
6490                 public MethodSpec Setter {
6491                         get {
6492                                 return setter;
6493                         }
6494                         set {
6495                                 setter = value;
6496                         }
6497                 }
6498
6499                 #endregion
6500
6501                 protected override Expression DoResolve (ResolveContext ec)
6502                 {
6503                         if (eclass == ExprClass.Unresolved) {
6504                                 var expr = OverloadResolve (ec, null);
6505                                 if (expr == null)
6506                                         return null;
6507
6508                                 if (expr != this)
6509                                         return expr.Resolve (ec);
6510                         }
6511
6512                         if (!ResolveGetter (ec))
6513                                 return null;
6514
6515                         return this;
6516                 }
6517
6518                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6519                 {
6520                         if (right_side == EmptyExpression.OutAccess) {
6521                                 // TODO: best_candidate can be null at this point
6522                                 INamedBlockVariable variable = null;
6523                                 if (best_candidate != null && ec.CurrentBlock.ParametersBlock.TopBlock.GetLocalName (best_candidate.Name, ec.CurrentBlock, ref variable) && variable is Linq.RangeVariable) {
6524                                         ec.Report.Error (1939, loc, "A range variable `{0}' may not be passes as `ref' or `out' parameter",
6525                                                 best_candidate.Name);
6526                                 } else {
6527                                         right_side.DoResolveLValue (ec, this);
6528                                 }
6529                                 return null;
6530                         }
6531
6532                         if (eclass == ExprClass.Unresolved) {
6533                                 var expr = OverloadResolve (ec, right_side);
6534                                 if (expr == null)
6535                                         return null;
6536
6537                                 if (expr != this)
6538                                         return expr.ResolveLValue (ec, right_side);
6539                         } else {
6540                                 ResolveInstanceExpression (ec, right_side);
6541                         }
6542
6543                         if (!ResolveSetter (ec))
6544                                 return null;
6545
6546                         return this;
6547                 }
6548
6549                 //
6550                 // Implements the IAssignMethod interface for assignments
6551                 //
6552                 public virtual void Emit (EmitContext ec, bool leave_copy)
6553                 {
6554                         var call = new CallEmitter ();
6555                         call.InstanceExpression = InstanceExpression;
6556                         if (has_await_arguments)
6557                                 call.HasAwaitArguments = true;
6558                         else
6559                                 call.DuplicateArguments = emitting_compound_assignment;
6560
6561                         call.Emit (ec, Getter, Arguments, loc);
6562
6563                         if (call.HasAwaitArguments) {
6564                                 InstanceExpression = call.InstanceExpression;
6565                                 Arguments = call.EmittedArguments;
6566                                 has_await_arguments = true;
6567                         }
6568
6569                         if (leave_copy) {
6570                                 ec.Emit (OpCodes.Dup);
6571                                 temp = new LocalTemporary (Type);
6572                                 temp.Store (ec);
6573                         }
6574                 }
6575
6576                 public abstract void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
6577
6578                 public override void Emit (EmitContext ec)
6579                 {
6580                         Emit (ec, false);
6581                 }
6582
6583                 protected override FieldExpr EmitToFieldSource (EmitContext ec)
6584                 {
6585                         has_await_arguments = true;
6586                         Emit (ec, false);
6587                         return null;
6588                 }
6589
6590                 public abstract SLE.Expression MakeAssignExpression (BuilderContext ctx, Expression source);
6591
6592                 protected abstract Expression OverloadResolve (ResolveContext rc, Expression right_side);
6593
6594                 bool ResolveGetter (ResolveContext rc)
6595                 {
6596                         if (!best_candidate.HasGet) {
6597                                 if (InstanceExpression != EmptyExpression.Null) {
6598                                         rc.Report.SymbolRelatedToPreviousError (best_candidate);
6599                                         rc.Report.Error (154, loc, "The property or indexer `{0}' cannot be used in this context because it lacks the `get' accessor",
6600                                                 best_candidate.GetSignatureForError ());
6601                                         return false;
6602                                 }
6603                         } else if (!best_candidate.Get.IsAccessible (rc) || !best_candidate.Get.DeclaringType.IsAccessible (rc)) {
6604                                 if (best_candidate.HasDifferentAccessibility) {
6605                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6606                                         rc.Report.Error (271, loc, "The property or indexer `{0}' cannot be used in this context because the get accessor is inaccessible",
6607                                                 TypeManager.CSharpSignature (best_candidate));
6608                                 } else {
6609                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Get);
6610                                         ErrorIsInaccesible (rc, best_candidate.Get.GetSignatureForError (), loc);
6611                                 }
6612                         }
6613
6614                         if (best_candidate.HasDifferentAccessibility) {
6615                                 CheckProtectedMemberAccess (rc, best_candidate.Get);
6616                         }
6617
6618                         getter = CandidateToBaseOverride (rc, best_candidate.Get);
6619                         return true;
6620                 }
6621
6622                 bool ResolveSetter (ResolveContext rc)
6623                 {
6624                         if (!best_candidate.HasSet) {
6625                                 rc.Report.Error (200, loc, "Property or indexer `{0}' cannot be assigned to (it is read-only)",
6626                                         GetSignatureForError ());
6627                                 return false;
6628                         }
6629
6630                         if (!best_candidate.Set.IsAccessible (rc) || !best_candidate.Set.DeclaringType.IsAccessible (rc)) {
6631                                 if (best_candidate.HasDifferentAccessibility) {
6632                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6633                                         rc.Report.Error (272, loc, "The property or indexer `{0}' cannot be used in this context because the set accessor is inaccessible",
6634                                                 GetSignatureForError ());
6635                                 } else {
6636                                         rc.Report.SymbolRelatedToPreviousError (best_candidate.Set);
6637                                         ErrorIsInaccesible (rc, best_candidate.GetSignatureForError (), loc);
6638                                 }
6639                         }
6640
6641                         if (best_candidate.HasDifferentAccessibility)
6642                                 CheckProtectedMemberAccess (rc, best_candidate.Set);
6643
6644                         setter = CandidateToBaseOverride (rc, best_candidate.Set);
6645                         return true;
6646                 }
6647         }
6648
6649         /// <summary>
6650         ///   Fully resolved expression that evaluates to an Event
6651         /// </summary>
6652         public class EventExpr : MemberExpr, IAssignMethod
6653         {
6654                 readonly EventSpec spec;
6655                 MethodSpec op;
6656
6657                 public EventExpr (EventSpec spec, Location loc)
6658                 {
6659                         this.spec = spec;
6660                         this.loc = loc;
6661                 }
6662
6663                 #region Properties
6664
6665                 protected override TypeSpec DeclaringType {
6666                         get {
6667                                 return spec.DeclaringType;
6668                         }
6669                 }
6670
6671                 public override string Name {
6672                         get {
6673                                 return spec.Name;
6674                         }
6675                 }
6676
6677                 public override bool IsInstance {
6678                         get {
6679                                 return !spec.IsStatic;
6680                         }
6681                 }
6682
6683                 public override bool IsStatic {
6684                         get {
6685                                 return spec.IsStatic;
6686                         }
6687                 }
6688
6689                 public override string KindName {
6690                         get { return "event"; }
6691                 }
6692
6693                 public MethodSpec Operator {
6694                         get {
6695                                 return op;
6696                         }
6697                 }
6698
6699                 #endregion
6700
6701                 public override MemberExpr ResolveMemberAccess (ResolveContext ec, Expression left, SimpleName original)
6702                 {
6703                         //
6704                         // If the event is local to this class and we are not lhs of +=/-= we transform ourselves into a FieldExpr
6705                         //
6706                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6707                                 if (spec.BackingField != null &&
6708                                         (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition))) {
6709
6710                                         spec.MemberDefinition.SetIsUsed ();
6711
6712                                         if (!ec.IsObsolete) {
6713                                                 ObsoleteAttribute oa = spec.GetAttributeObsolete ();
6714                                                 if (oa != null)
6715                                                         AttributeTester.Report_ObsoleteMessage (oa, spec.GetSignatureForError (), loc, ec.Report);
6716                                         }
6717
6718                                         if ((spec.Modifiers & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
6719                                                 Error_AssignmentEventOnly (ec);
6720
6721                                         FieldExpr ml = new FieldExpr (spec.BackingField, loc);
6722
6723                                         InstanceExpression = null;
6724
6725                                         return ml.ResolveMemberAccess (ec, left, original);
6726                                 }
6727                         }
6728
6729                         return base.ResolveMemberAccess (ec, left, original);
6730                 }
6731
6732                 public override Expression CreateExpressionTree (ResolveContext ec)
6733                 {
6734                         throw new NotSupportedException ("ET");
6735                 }
6736
6737                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6738                 {
6739                         if (right_side == EmptyExpression.EventAddition) {
6740                                 op = spec.AccessorAdd;
6741                         } else if (right_side == EmptyExpression.EventSubtraction) {
6742                                 op = spec.AccessorRemove;
6743                         }
6744
6745                         if (op == null) {
6746                                 Error_AssignmentEventOnly (ec);
6747                                 return null;
6748                         }
6749
6750                         op = CandidateToBaseOverride (ec, op);
6751                         return this;
6752                 }
6753
6754                 protected override Expression DoResolve (ResolveContext ec)
6755                 {
6756                         eclass = ExprClass.EventAccess;
6757                         type = spec.MemberType;
6758
6759                         ResolveInstanceExpression (ec, null);
6760
6761                         if (!ec.HasSet (ResolveContext.Options.CompoundAssignmentScope)) {
6762                                 Error_AssignmentEventOnly (ec);
6763                         }
6764
6765                         DoBestMemberChecks (ec, spec);
6766                         return this;
6767                 }
6768
6769                 public override void Emit (EmitContext ec)
6770                 {
6771                         throw new NotSupportedException ();
6772                         //Error_CannotAssign ();
6773                 }
6774
6775                 #region IAssignMethod Members
6776
6777                 public void Emit (EmitContext ec, bool leave_copy)
6778                 {
6779                         throw new NotImplementedException ();
6780                 }
6781
6782                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
6783                 {
6784                         if (leave_copy || !isCompound)
6785                                 throw new NotImplementedException ("EventExpr::EmitAssign");
6786
6787                         Arguments args = new Arguments (1);
6788                         args.Add (new Argument (source));
6789
6790                         var call = new CallEmitter ();
6791                         call.InstanceExpression = InstanceExpression;
6792                         call.Emit (ec, op, args, loc);
6793                 }
6794
6795                 #endregion
6796
6797                 void Error_AssignmentEventOnly (ResolveContext ec)
6798                 {
6799                         if (spec.DeclaringType == ec.CurrentType || TypeManager.IsNestedChildOf (ec.CurrentType, spec.DeclaringType.MemberDefinition)) {
6800                                 ec.Report.Error (79, loc,
6801                                         "The event `{0}' can only appear on the left hand side of `+=' or `-=' operator",
6802                                         GetSignatureForError ());
6803                         } else {
6804                                 ec.Report.Error (70, loc,
6805                                         "The event `{0}' can only appear on the left hand side of += or -= when used outside of the type `{1}'",
6806                                         GetSignatureForError (), spec.DeclaringType.GetSignatureForError ());
6807                         }
6808                 }
6809
6810                 protected override void Error_CannotCallAbstractBase (ResolveContext rc, string name)
6811                 {
6812                         name = name.Substring (0, name.LastIndexOf ('.'));
6813                         base.Error_CannotCallAbstractBase (rc, name);
6814                 }
6815
6816                 public override string GetSignatureForError ()
6817                 {
6818                         return TypeManager.CSharpSignature (spec);
6819                 }
6820
6821                 public override void SetTypeArguments (ResolveContext ec, TypeArguments ta)
6822                 {
6823                         Error_TypeArgumentsCannotBeUsed (ec, "event", GetSignatureForError (), loc);
6824                 }
6825         }
6826
6827         public class TemporaryVariableReference : VariableReference
6828         {
6829                 public class Declarator : Statement
6830                 {
6831                         TemporaryVariableReference variable;
6832
6833                         public Declarator (TemporaryVariableReference variable)
6834                         {
6835                                 this.variable = variable;
6836                                 loc = variable.loc;
6837                         }
6838
6839                         protected override void DoEmit (EmitContext ec)
6840                         {
6841                                 variable.li.CreateBuilder (ec);
6842                         }
6843
6844                         public override void Emit (EmitContext ec)
6845                         {
6846                                 // Don't create sequence point
6847                                 DoEmit (ec);
6848                         }
6849
6850                         protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
6851                         {
6852                                 return false;
6853                         }
6854
6855                         protected override void CloneTo (CloneContext clonectx, Statement target)
6856                         {
6857                                 // Nothing
6858                         }
6859                 }
6860
6861                 LocalVariable li;
6862
6863                 public TemporaryVariableReference (LocalVariable li, Location loc)
6864                 {
6865                         this.li = li;
6866                         this.type = li.Type;
6867                         this.loc = loc;
6868                 }
6869
6870                 public override bool IsLockedByStatement {
6871                         get {
6872                                 return false;
6873                         }
6874                         set {
6875                         }
6876                 }
6877
6878                 public LocalVariable LocalInfo {
6879                     get {
6880                         return li;
6881                     }
6882                 }
6883
6884                 public static TemporaryVariableReference Create (TypeSpec type, Block block, Location loc)
6885                 {
6886                         var li = LocalVariable.CreateCompilerGenerated (type, block, loc);
6887                         return new TemporaryVariableReference (li, loc);
6888                 }
6889
6890                 protected override Expression DoResolve (ResolveContext ec)
6891                 {
6892                         eclass = ExprClass.Variable;
6893
6894                         //
6895                         // Don't capture temporary variables except when using
6896                         // state machine redirection and block yields
6897                         //
6898                         if (ec.CurrentAnonymousMethod is StateMachineInitializer &&
6899                                 (ec.CurrentBlock.Explicit.HasYield || ec.CurrentBlock.Explicit.HasAwait) &&
6900                                 ec.IsVariableCapturingRequired) {
6901                                 AnonymousMethodStorey storey = li.Block.Explicit.CreateAnonymousMethodStorey (ec);
6902                                 storey.CaptureLocalVariable (ec, li);
6903                         }
6904
6905                         return this;
6906                 }
6907
6908                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
6909                 {
6910                         return Resolve (ec);
6911                 }
6912
6913                 public override void Emit (EmitContext ec)
6914                 {
6915                         li.CreateBuilder (ec);
6916
6917                         Emit (ec, false);
6918                 }
6919
6920                 public void EmitAssign (EmitContext ec, Expression source)
6921                 {
6922                         li.CreateBuilder (ec);
6923
6924                         EmitAssign (ec, source, false, false);
6925                 }
6926
6927                 public override HoistedVariable GetHoistedVariable (AnonymousExpression ae)
6928                 {
6929                         return li.HoistedVariant;
6930                 }
6931
6932                 public override bool IsFixed {
6933                         get { return true; }
6934                 }
6935
6936                 public override bool IsRef {
6937                         get { return false; }
6938                 }
6939
6940                 public override string Name {
6941                         get { throw new NotImplementedException (); }
6942                 }
6943
6944                 public override void SetHasAddressTaken ()
6945                 {
6946                         throw new NotImplementedException ();
6947                 }
6948
6949                 protected override ILocalVariable Variable {
6950                         get { return li; }
6951                 }
6952
6953                 public override VariableInfo VariableInfo {
6954                         get { return null; }
6955                 }
6956         }
6957
6958         ///
6959         /// Handles `var' contextual keyword; var becomes a keyword only
6960         /// if no type called var exists in a variable scope
6961         ///
6962         class VarExpr : SimpleName
6963         {
6964                 public VarExpr (Location loc)
6965                         : base ("var", loc)
6966                 {
6967                 }
6968
6969                 public bool InferType (ResolveContext ec, Expression right_side)
6970                 {
6971                         if (type != null)
6972                                 throw new InternalErrorException ("An implicitly typed local variable could not be redefined");
6973
6974                         type = right_side.Type;
6975                         if (type == InternalType.NullLiteral || type.Kind == MemberKind.Void || type == InternalType.AnonymousMethod || type == InternalType.MethodGroup) {
6976                                 ec.Report.Error (815, loc,
6977                                         "An implicitly typed local variable declaration cannot be initialized with `{0}'",
6978                                         type.GetSignatureForError ());
6979                                 return false;
6980                         }
6981
6982                         eclass = ExprClass.Variable;
6983                         return true;
6984                 }
6985
6986                 protected override void Error_TypeOrNamespaceNotFound (IMemberContext ec)
6987                 {
6988                         if (ec.Module.Compiler.Settings.Version < LanguageVersion.V_3)
6989                                 base.Error_TypeOrNamespaceNotFound (ec);
6990                         else
6991                                 ec.Module.Compiler.Report.Error (825, loc, "The contextual keyword `var' may only appear within a local variable declaration");
6992                 }
6993         }
6994 }