mcs/mcs/assign.cs

   1 //
   2 // assign.cs: Assignments.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Martin Baulig (martin@ximian.com)
   7 //   Marek Safar (marek.safar@gmail.com)
   8 //
   9 // Dual licensed under the terms of the MIT X11 or GNU GPL
  10 //
  11 // Copyright 2001, 2002, 2003 Ximian, Inc.
  12 // Copyright 2004-2008 Novell, Inc
  13 // Copyright 2011 Xamarin Inc
  14 //
  15 using System;
  16
  17 #if STATIC
  18 using IKVM.Reflection.Emit;
  19 #else
  20 using System.Reflection.Emit;
  21 #endif
  22
  23 namespace Mono.CSharp {
  24
  25         /// <summary>
  26         ///   This interface is implemented by expressions that can be assigned to.
  27         /// </summary>
  28         /// <remarks>
  29         ///   This interface is implemented by Expressions whose values can not
  30         ///   store the result on the top of the stack.
  31         ///
  32         ///   Expressions implementing this (Properties, Indexers and Arrays) would
  33         ///   perform an assignment of the Expression "source" into its final
  34         ///   location.
  35         ///
  36         ///   No values on the top of the stack are expected to be left by
  37         ///   invoking this method.
  38         /// </remarks>
  39         public interface IAssignMethod {
  40                 //
  41                 // This is an extra version of Emit. If leave_copy is `true'
  42                 // A copy of the expression will be left on the stack at the
  43                 // end of the code generated for EmitAssign
  44                 //
  45                 void Emit (EmitContext ec, bool leave_copy);
  46
  47                 //
  48                 // This method does the assignment
  49                 // `source' will be stored into the location specified by `this'
  50                 // if `leave_copy' is true, a copy of `source' will be left on the stack
  51                 // if `prepare_for_load' is true, when `source' is emitted, there will
  52                 // be data on the stack that it can use to compuatate its value. This is
  53                 // for expressions like a [f ()] ++, where you can't call `f ()' twice.
  54                 //
  55                 void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound);
  56
  57                 /*
  58                 For simple assignments, this interface is very simple, EmitAssign is called with source
  59                 as the source expression and leave_copy and prepare_for_load false.
  60
  61                 For compound assignments it gets complicated.
  62
  63                 EmitAssign will be called as before, however, prepare_for_load will be
  64                 true. The @source expression will contain an expression
  65                 which calls Emit. So, the calls look like:
  66
  67                 this.EmitAssign (ec, source, false, true) ->
  68                         source.Emit (ec); ->
  69                                 [...] ->
  70                                         this.Emit (ec, false); ->
  71                                         end this.Emit (ec, false); ->
  72                                 end [...]
  73                         end source.Emit (ec);
  74                 end this.EmitAssign (ec, source, false, true)
  75
  76
  77                 When prepare_for_load is true, EmitAssign emits a `token' on the stack that
  78                 Emit will use for its state.
  79
  80                 Let's take FieldExpr as an example. assume we are emitting f ().y += 1;
  81
  82                 Here is the call tree again. This time, each call is annotated with the IL
  83                 it produces:
  84
  85                 this.EmitAssign (ec, source, false, true)
  86                         call f
  87                         dup
  88
  89                         Binary.Emit ()
  90                                 this.Emit (ec, false);
  91                                 ldfld y
  92                                 end this.Emit (ec, false);
  93
  94                                 IntConstant.Emit ()
  95                                 ldc.i4.1
  96                                 end IntConstant.Emit
  97
  98                                 add
  99                         end Binary.Emit ()
 100
 101                         stfld
 102                 end this.EmitAssign (ec, source, false, true)
 103
 104                 Observe two things:
 105                         1) EmitAssign left a token on the stack. It was the result of f ().
 106                         2) This token was used by Emit
 107
 108                 leave_copy (in both EmitAssign and Emit) tells the compiler to leave a copy
 109                 of the expression at that point in evaluation. This is used for pre/post inc/dec
 110                 and for a = x += y. Let's do the above example with leave_copy true in EmitAssign
 111
 112                 this.EmitAssign (ec, source, true, true)
 113                         call f
 114                         dup
 115
 116                         Binary.Emit ()
 117                                 this.Emit (ec, false);
 118                                 ldfld y
 119                                 end this.Emit (ec, false);
 120
 121                                 IntConstant.Emit ()
 122                                 ldc.i4.1
 123                                 end IntConstant.Emit
 124
 125                                 add
 126                         end Binary.Emit ()
 127
 128                         dup
 129                         stloc temp
 130                         stfld
 131                         ldloc temp
 132                 end this.EmitAssign (ec, source, true, true)
 133
 134                 And with it true in Emit
 135
 136                 this.EmitAssign (ec, source, false, true)
 137                         call f
 138                         dup
 139
 140                         Binary.Emit ()
 141                                 this.Emit (ec, true);
 142                                 ldfld y
 143                                 dup
 144                                 stloc temp
 145                                 end this.Emit (ec, true);
 146
 147                                 IntConstant.Emit ()
 148                                 ldc.i4.1
 149                                 end IntConstant.Emit
 150
 151                                 add
 152                         end Binary.Emit ()
 153
 154                         stfld
 155                         ldloc temp
 156                 end this.EmitAssign (ec, source, false, true)
 157
 158                 Note that these two examples are what happens for ++x and x++, respectively.
 159                 */
 160         }
 161
 162         /// <summary>
 163         ///   An Expression to hold a temporary value.
 164         /// </summary>
 165         /// <remarks>
 166         ///   The LocalTemporary class is used to hold temporary values of a given
 167         ///   type to "simulate" the expression semantics. The local variable is
 168         ///   never captured.
 169         ///
 170         ///   The local temporary is used to alter the normal flow of code generation
 171         ///   basically it creates a local variable, and its emit instruction generates
 172         ///   code to access this value, return its address or save its value.
 173         ///
 174         ///   If `is_address' is true, then the value that we store is the address to the
 175         ///   real value, and not the value itself.
 176         ///
 177         ///   This is needed for a value type, because otherwise you just end up making a
 178         ///   copy of the value on the stack and modifying it. You really need a pointer
 179         ///   to the origional value so that you can modify it in that location. This
 180         ///   Does not happen with a class because a class is a pointer -- so you always
 181         ///   get the indirection.
 182         ///
 183         /// </remarks>
 184         public class LocalTemporary : Expression, IMemoryLocation, IAssignMethod {
 185                 LocalBuilder builder;
 186
 187                 public LocalTemporary (TypeSpec t)
 188                 {
 189                         type = t;
 190                         eclass = ExprClass.Value;
 191                 }
 192
 193                 public LocalTemporary (LocalBuilder b, TypeSpec t)
 194                         : this (t)
 195                 {
 196                         builder = b;
 197                 }
 198
 199                 public void Release (EmitContext ec)
 200                 {
 201                         ec.FreeTemporaryLocal (builder, type);
 202                         builder = null;
 203                 }
 204
 205                 public override bool ContainsEmitWithAwait ()
 206                 {
 207                         return false;
 208                 }
 209
 210                 public override Expression CreateExpressionTree (ResolveContext ec)
 211                 {
 212                         Arguments args = new Arguments (1);
 213                         args.Add (new Argument (this));
 214                         return CreateExpressionFactoryCall (ec, "Constant", args);
 215                 }
 216
 217                 protected override Expression DoResolve (ResolveContext ec)
 218                 {
 219                         return this;
 220                 }
 221
 222                 public override Expression DoResolveLValue (ResolveContext ec, Expression right_side)
 223                 {
 224                         return this;
 225                 }
 226
 227                 public override void Emit (EmitContext ec)
 228                 {
 229                         if (builder == null)
 230                                 throw new InternalErrorException ("Emit without Store, or after Release");
 231
 232                         ec.Emit (OpCodes.Ldloc, builder);
 233                 }
 234
 235                 #region IAssignMethod Members
 236
 237                 public void Emit (EmitContext ec, bool leave_copy)
 238                 {
 239                         Emit (ec);
 240
 241                         if (leave_copy)
 242                                 Emit (ec);
 243                 }
 244
 245                 public void EmitAssign (EmitContext ec, Expression source, bool leave_copy, bool isCompound)
 246                 {
 247                         if (isCompound)
 248                                 throw new NotImplementedException ();
 249
 250                         source.Emit (ec);
 251
 252                         Store (ec);
 253
 254                         if (leave_copy)
 255                                 Emit (ec);
 256                 }
 257
 258                 #endregion
 259
 260                 public LocalBuilder Builder {
 261                         get { return builder; }
 262                 }
 263
 264                 public void Store (EmitContext ec)
 265                 {
 266                         if (builder == null)
 267                                 builder = ec.GetTemporaryLocal (type);
 268
 269                         ec.Emit (OpCodes.Stloc, builder);
 270                 }
 271
 272                 public void AddressOf (EmitContext ec, AddressOp mode)
 273                 {
 274                         if (builder == null)
 275                                 builder = ec.GetTemporaryLocal (type);
 276
 277                         if (builder.LocalType.IsByRef) {
 278                                 //
 279                                 // if is_address, than this is just the address anyways,
 280                                 // so we just return this.
 281                                 //
 282                                 ec.Emit (OpCodes.Ldloc, builder);
 283                         } else {
 284                                 ec.Emit (OpCodes.Ldloca, builder);
 285                         }
 286                 }
 287         }
 288
 289         /// <summary>
 290         ///   The Assign node takes care of assigning the value of source into
 291         ///   the expression represented by target.
 292         /// </summary>
 293         public abstract class Assign : ExpressionStatement {
 294                 protected Expression target, source;
 295
 296                 protected Assign (Expression target, Expression source, Location loc)
 297                 {
 298                         this.target = target;
 299                         this.source = source;
 300                         this.loc = loc;
 301                 }
 302
 303                 public Expression Target {
 304                         get { return target; }
 305                 }
 306
 307                 public Expression Source {
 308                         get {
 309                                 return source;
 310                         }
 311                 }
 312
 313                 public override Location StartLocation {
 314                         get {
 315                                 return target.StartLocation;
 316                         }
 317                 }
 318
 319                 public override bool ContainsEmitWithAwait ()
 320                 {
 321                         return target.ContainsEmitWithAwait () || source.ContainsEmitWithAwait ();
 322                 }
 323
 324                 public override Expression CreateExpressionTree (ResolveContext ec)
 325                 {
 326                         ec.Report.Error (832, loc, "An expression tree cannot contain an assignment operator");
 327                         return null;
 328                 }
 329
 330                 protected override Expression DoResolve (ResolveContext ec)
 331                 {
 332                         bool ok = true;
 333                         source = source.Resolve (ec);
 334
 335                         if (source == null) {
 336                                 ok = false;
 337                                 source = EmptyExpression.Null;
 338                         }
 339
 340                         target = target.ResolveLValue (ec, source);
 341
 342                         if (target == null || !ok)
 343                                 return null;
 344
 345                         TypeSpec target_type = target.Type;
 346                         TypeSpec source_type = source.Type;
 347
 348                         eclass = ExprClass.Value;
 349                         type = target_type;
 350
 351                         if (!(target is IAssignMethod)) {
 352                                 target.Error_ValueAssignment (ec, source);
 353                                 return null;
 354                         }
 355
 356                         if (target_type != source_type) {
 357                                 Expression resolved = ResolveConversions (ec);
 358
 359                                 if (resolved != this)
 360                                         return resolved;
 361                         }
 362
 363                         return this;
 364                 }
 365
 366 #if NET_4_0 || MONODROID
 367                 public override System.Linq.Expressions.Expression MakeExpression (BuilderContext ctx)
 368                 {
 369                         var tassign = target as IDynamicAssign;
 370                         if (tassign == null)
 371                                 throw new InternalErrorException (target.GetType () + " does not support dynamic assignment");
 372
 373                         var target_object = tassign.MakeAssignExpression (ctx, source);
 374
 375                         //
 376                         // Some hacking is needed as DLR does not support void type and requires
 377                         // always have object convertible return type to support caching and chaining
 378                         //
 379                         // We do this by introducing an explicit block which returns RHS value when
 380                         // available or null
 381                         //
 382                         if (target_object.NodeType == System.Linq.Expressions.ExpressionType.Block)
 383                                 return target_object;
 384
 385                         System.Linq.Expressions.UnaryExpression source_object;
 386                         if (ctx.HasSet (BuilderContext.Options.CheckedScope)) {
 387                                 source_object = System.Linq.Expressions.Expression.ConvertChecked (source.MakeExpression (ctx), target_object.Type);
 388                         } else {
 389                                 source_object = System.Linq.Expressions.Expression.Convert (source.MakeExpression (ctx), target_object.Type);
 390                         }
 391
 392                         return System.Linq.Expressions.Expression.Assign (target_object, source_object);
 393                 }
 394 #endif
 395                 protected virtual Expression ResolveConversions (ResolveContext ec)
 396                 {
 397                         source = Convert.ImplicitConversionRequired (ec, source, target.Type, source.Location);
 398                         if (source == null)
 399                                 return null;
 400
 401                         return this;
 402                 }
 403
 404                 void Emit (EmitContext ec, bool is_statement)
 405                 {
 406                         IAssignMethod t = (IAssignMethod) target;
 407                         t.EmitAssign (ec, source, !is_statement, this is CompoundAssign);
 408                 }
 409
 410                 public override void Emit (EmitContext ec)
 411                 {
 412                         Emit (ec, false);
 413                 }
 414
 415                 public override void EmitStatement (EmitContext ec)
 416                 {
 417                         Emit (ec, true);
 418                 }
 419
 420                 protected override void CloneTo (CloneContext clonectx, Expression t)
 421                 {
 422                         Assign _target = (Assign) t;
 423
 424                         _target.target = target.Clone (clonectx);
 425                         _target.source = source.Clone (clonectx);
 426                 }
 427
 428                 public override object Accept (StructuralVisitor visitor)
 429                 {
 430                         return visitor.Visit (this);
 431                 }
 432         }
 433
 434         public class SimpleAssign : Assign
 435         {
 436                 public SimpleAssign (Expression target, Expression source)
 437                         : this (target, source, target.Location)
 438                 {
 439                 }
 440
 441                 public SimpleAssign (Expression target, Expression source, Location loc)
 442                         : base (target, source, loc)
 443                 {
 444                 }
 445
 446                 bool CheckEqualAssign (Expression t)
 447                 {
 448                         if (source is Assign) {
 449                                 Assign a = (Assign) source;
 450                                 if (t.Equals (a.Target))
 451                                         return true;
 452                                 return a is SimpleAssign && ((SimpleAssign) a).CheckEqualAssign (t);
 453                         }
 454                         return t.Equals (source);
 455                 }
 456
 457                 protected override Expression DoResolve (ResolveContext ec)
 458                 {
 459                         Expression e = base.DoResolve (ec);
 460                         if (e == null || e != this)
 461                                 return e;
 462
 463                         if (CheckEqualAssign (target))
 464                                 ec.Report.Warning (1717, 3, loc, "Assignment made to same variable; did you mean to assign something else?");
 465
 466                         return this;
 467                 }
 468         }
 469
 470         public class RuntimeExplicitAssign : Assign
 471         {
 472                 public RuntimeExplicitAssign (Expression target, Expression source)
 473                         : base (target, source, target.Location)
 474                 {
 475                 }
 476
 477                 protected override Expression ResolveConversions (ResolveContext ec)
 478                 {
 479                         source = EmptyCast.Create (source, target.Type);
 480                         return this;
 481                 }
 482         }
 483
 484         //
 485         // Compiler generated assign
 486         //
 487         class CompilerAssign : Assign
 488         {
 489                 public CompilerAssign (Expression target, Expression source, Location loc)
 490                         : base (target, source, loc)
 491                 {
 492                         if (target.Type != null) {
 493                                 type = target.Type;
 494                                 eclass = ExprClass.Value;
 495                         }
 496                 }
 497
 498                 protected override Expression DoResolve (ResolveContext ec)
 499                 {
 500                         var expr = base.DoResolve (ec);
 501                         var vr = target as VariableReference;
 502                         if (vr != null && vr.VariableInfo != null)
 503                                 vr.VariableInfo.IsEverAssigned = false;
 504
 505                         return expr;
 506                 }
 507
 508                 public void UpdateSource (Expression source)
 509                 {
 510                         base.source = source;
 511                 }
 512         }
 513
 514         //
 515         // Implements fields and events class initializers
 516         //
 517         public class FieldInitializer : Assign
 518         {
 519                 //
 520                 // Field initializers are tricky for partial classes. They have to
 521                 // share same constructor (block) for expression trees resolve but
 522                 // they have they own resolve scope
 523                 //
 524                 sealed class FieldInitializerContext : ResolveContext
 525                 {
 526                         ExplicitBlock ctor_block;
 527
 528                         public FieldInitializerContext (IMemberContext mc, ResolveContext constructorContext)
 529                                 : base (mc, Options.FieldInitializerScope | Options.ConstructorScope)
 530                         {
 531                                 this.ctor_block = constructorContext.CurrentBlock.Explicit;
 532                         }
 533
 534                         public override ExplicitBlock ConstructorBlock {
 535                                 get {
 536                                         return ctor_block;
 537                                 }
 538                         }
 539                 }
 540
 541                 //
 542                 // Keep resolved value because field initializers have their own rules
 543                 //
 544                 ExpressionStatement resolved;
 545                 FieldBase mc;
 546
 547                 public FieldInitializer (FieldBase mc, Expression expression, Location loc)
 548                         : base (new FieldExpr (mc.Spec, expression.Location), expression, loc)
 549                 {
 550                         this.mc = mc;
 551                         if (!mc.IsStatic)
 552                                 ((FieldExpr)target).InstanceExpression = new CompilerGeneratedThis (mc.CurrentType, expression.Location);
 553                 }
 554
 555                 public override Location StartLocation {
 556                         get {
 557                                 return loc;
 558                         }
 559                 }
 560
 561                 protected override Expression DoResolve (ResolveContext ec)
 562                 {
 563                         // Field initializer can be resolved (fail) many times
 564                         if (source == null)
 565                                 return null;
 566
 567                         if (resolved == null) {
 568                                 var ctx = new FieldInitializerContext (mc, ec);
 569                                 resolved = base.DoResolve (ctx) as ExpressionStatement;
 570                         }
 571
 572                         return resolved;
 573                 }
 574
 575                 public override void EmitStatement (EmitContext ec)
 576                 {
 577                         if (resolved == null)
 578                                 return;
 579
 580                         //
 581                         // Emit sequence symbol info even if we are in compiler generated
 582                         // block to allow debugging field initializers when constructor is
 583                         // compiler generated
 584                         //
 585                         if (ec.HasSet (BuilderContext.Options.OmitDebugInfo) && ec.HasMethodSymbolBuilder) {
 586                                 using (ec.With (BuilderContext.Options.OmitDebugInfo, false)) {
 587                                         ec.Mark (loc);
 588                                 }
 589                         }
 590
 591                         if (resolved != this)
 592                                 resolved.EmitStatement (ec);
 593                         else
 594                                 base.EmitStatement (ec);
 595                 }
 596
 597                 public bool IsDefaultInitializer {
 598                         get {
 599                                 Constant c = source as Constant;
 600                                 if (c == null)
 601                                         return false;
 602
 603                                 FieldExpr fe = (FieldExpr)target;
 604                                 return c.IsDefaultInitializer (fe.Type);
 605                         }
 606                 }
 607
 608                 public override bool IsSideEffectFree {
 609                         get {
 610                                 return source.IsSideEffectFree;
 611                         }
 612                 }
 613         }
 614
 615         //
 616         // This class is used for compound assignments.
 617         //
 618         public class CompoundAssign : Assign
 619         {
 620                 // This is just a hack implemented for arrays only
 621                 public sealed class TargetExpression : Expression
 622                 {
 623                         readonly Expression child;
 624
 625                         public TargetExpression (Expression child)
 626                         {
 627                                 this.child = child;
 628                                 this.loc = child.Location;
 629                         }
 630
 631                         public override bool ContainsEmitWithAwait ()
 632                         {
 633                                 return child.ContainsEmitWithAwait ();
 634                         }
 635
 636                         public override Expression CreateExpressionTree (ResolveContext ec)
 637                         {
 638                                 throw new NotSupportedException ("ET");
 639                         }
 640
 641                         protected override Expression DoResolve (ResolveContext ec)
 642                         {
 643                                 type = child.Type;
 644                                 eclass = ExprClass.Value;
 645                                 return this;
 646                         }
 647
 648                         public override void Emit (EmitContext ec)
 649                         {
 650                                 child.Emit (ec);
 651                         }
 652
 653                         public override Expression EmitToField (EmitContext ec)
 654                         {
 655                                 return child.EmitToField (ec);
 656                         }
 657                 }
 658
 659                 // Used for underlying binary operator
 660                 readonly Binary.Operator op;
 661                 Expression right;
 662                 Expression left;
 663
 664                 public CompoundAssign (Binary.Operator op, Expression target, Expression source)
 665                         : base (target, source, target.Location)
 666                 {
 667                         right = source;
 668                         this.op = op;
 669                 }
 670
 671                 public CompoundAssign (Binary.Operator op, Expression target, Expression source, Expression left)
 672                         : this (op, target, source)
 673                 {
 674                         this.left = left;
 675                 }
 676
 677                 public Binary.Operator Operator {
 678                         get {
 679                                 return op;
 680                         }
 681                 }
 682
 683                 protected override Expression DoResolve (ResolveContext ec)
 684                 {
 685                         right = right.Resolve (ec);
 686                         if (right == null)
 687                                 return null;
 688
 689                         MemberAccess ma = target as MemberAccess;
 690                         using (ec.Set (ResolveContext.Options.CompoundAssignmentScope)) {
 691                                 target = target.Resolve (ec);
 692                         }
 693
 694                         if (target == null)
 695                                 return null;
 696
 697                         if (target is MethodGroupExpr){
 698                                 ec.Report.Error (1656, loc,
 699                                         "Cannot assign to `{0}' because it is a `{1}'",
 700                                         ((MethodGroupExpr)target).Name, target.ExprClassName);
 701                                 return null;
 702                         }
 703
 704                         var event_expr = target as EventExpr;
 705                         if (event_expr != null) {
 706                                 source = Convert.ImplicitConversionRequired (ec, right, target.Type, loc);
 707                                 if (source == null)
 708                                         return null;
 709
 710                                 Expression rside;
 711                                 if (op == Binary.Operator.Addition)
 712                                         rside = EmptyExpression.EventAddition;
 713                                 else if (op == Binary.Operator.Subtraction)
 714                                         rside = EmptyExpression.EventSubtraction;
 715                                 else
 716                                         rside = null;
 717
 718                                 target = target.ResolveLValue (ec, rside);
 719                                 if (target == null)
 720                                         return null;
 721
 722                                 eclass = ExprClass.Value;
 723                                 type = event_expr.Operator.ReturnType;
 724                                 return this;
 725                         }
 726
 727                         //
 728                         // Only now we can decouple the original source/target
 729                         // into a tree, to guarantee that we do not have side
 730                         // effects.
 731                         //
 732                         if (left == null)
 733                                 left = new TargetExpression (target);
 734
 735                         source = new Binary (op, left, right, true);
 736
 737                         if (target is DynamicMemberAssignable) {
 738                                 Arguments targs = ((DynamicMemberAssignable) target).Arguments;
 739                                 source = source.Resolve (ec);
 740
 741                                 Arguments args = new Arguments (targs.Count + 1);
 742                                 args.AddRange (targs);
 743                                 args.Add (new Argument (source));
 744
 745                                 var binder_flags = CSharpBinderFlags.ValueFromCompoundAssignment;
 746
 747                                 //
 748                                 // Compound assignment does target conversion using additional method
 749                                 // call, set checked context as the binary operation can overflow
 750                                 //
 751                                 if (ec.HasSet (ResolveContext.Options.CheckedScope))
 752                                         binder_flags |= CSharpBinderFlags.CheckedContext;
 753
 754                                 if (target is DynamicMemberBinder) {
 755                                         source = new DynamicMemberBinder (ma.Name, binder_flags, args, loc).Resolve (ec);
 756
 757                                         // Handles possible event addition/subtraction
 758                                         if (op == Binary.Operator.Addition || op == Binary.Operator.Subtraction) {
 759                                                 args = new Arguments (targs.Count + 1);
 760                                                 args.AddRange (targs);
 761                                                 args.Add (new Argument (right));
 762                                                 string method_prefix = op == Binary.Operator.Addition ?
 763                                                         Event.AEventAccessor.AddPrefix : Event.AEventAccessor.RemovePrefix;
 764
 765                                                 var invoke = DynamicInvocation.CreateSpecialNameInvoke (
 766                                                         new MemberAccess (right, method_prefix + ma.Name, loc), args, loc).Resolve (ec);
 767
 768                                                 args = new Arguments (targs.Count);
 769                                                 args.AddRange (targs);
 770                                                 source = new DynamicEventCompoundAssign (ma.Name, args,
 771                                                         (ExpressionStatement) source, (ExpressionStatement) invoke, loc).Resolve (ec);
 772                                         }
 773                                 } else {
 774                                         source = new DynamicIndexBinder (binder_flags, args, loc).Resolve (ec);
 775                                 }
 776
 777                                 return source;
 778                         }
 779
 780                         return base.DoResolve (ec);
 781                 }
 782
 783                 protected override Expression ResolveConversions (ResolveContext ec)
 784                 {
 785                         //
 786                         // LAMESPEC: Under dynamic context no target conversion is happening
 787                         // This allows more natual dynamic behaviour but breaks compatibility
 788                         // with static binding
 789                         //
 790                         if (target is RuntimeValueExpression)
 791                                 return this;
 792
 793                         TypeSpec target_type = target.Type;
 794
 795                         //
 796                         // 1. the return type is implicitly convertible to the type of target
 797                         //
 798                         if (Convert.ImplicitConversionExists (ec, source, target_type)) {
 799                                 source = Convert.ImplicitConversion (ec, source, target_type, loc);
 800                                 return this;
 801                         }
 802
 803                         //
 804                         // Otherwise, if the selected operator is a predefined operator
 805                         //
 806                         Binary b = source as Binary;
 807                         if (b == null && source is ReducedExpression)
 808                                 b = ((ReducedExpression) source).OriginalExpression as Binary;
 809
 810                         if (b != null) {
 811                                 //
 812                                 // 2a. the operator is a shift operator
 813                                 //
 814                                 // 2b. the return type is explicitly convertible to the type of x, and
 815                                 // y is implicitly convertible to the type of x
 816                                 //
 817                                 if ((b.Oper & Binary.Operator.ShiftMask) != 0 ||
 818                                         Convert.ImplicitConversionExists (ec, right, target_type)) {
 819                                         source = Convert.ExplicitConversion (ec, source, target_type, loc);
 820                                         return this;
 821                                 }
 822                         }
 823
 824                         if (source.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 825                                 Arguments arg = new Arguments (1);
 826                                 arg.Add (new Argument (source));
 827                                 return new SimpleAssign (target, new DynamicConversion (target_type, CSharpBinderFlags.ConvertExplicit, arg, loc), loc).Resolve (ec);
 828                         }
 829
 830                         right.Error_ValueCannotBeConverted (ec, target_type, false);
 831                         return null;
 832                 }
 833
 834                 protected override void CloneTo (CloneContext clonectx, Expression t)
 835                 {
 836                         CompoundAssign ctarget = (CompoundAssign) t;
 837
 838                         ctarget.right = ctarget.source = source.Clone (clonectx);
 839                         ctarget.target = target.Clone (clonectx);
 840                 }
 841
 842                 public override object Accept (StructuralVisitor visitor)
 843                 {
 844                         return visitor.Visit (this);
 845                 }
 846         }
 847 }