mcs/mcs/delegate.cs

   1 //
   2 // delegate.cs: Delegate Handler
   3 //
   4 // Authors:
   5 //     Ravi Pratap (ravi@ximian.com)
   6 //     Miguel de Icaza (miguel@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 Ximian, Inc (http://www.ximian.com)
  12 // Copyright 2003-2009 Novell, Inc (http://www.novell.com)
  13 //
  14
  15 using System;
  16
  17 #if STATIC
  18 using IKVM.Reflection;
  19 using IKVM.Reflection.Emit;
  20 #else
  21 using System.Reflection;
  22 using System.Reflection.Emit;
  23 #endif
  24
  25 namespace Mono.CSharp {
  26
  27         //
  28         // Delegate container implementation
  29         //
  30         public class Delegate : TypeContainer, IParametersMember
  31         {
  32                 FullNamedExpression ReturnType;
  33                 readonly ParametersCompiled parameters;
  34
  35                 Constructor Constructor;
  36                 Method InvokeBuilder;
  37                 Method BeginInvokeBuilder;
  38                 Method EndInvokeBuilder;
  39
  40                 static readonly string[] attribute_targets = new string [] { "type", "return" };
  41
  42                 public static readonly string InvokeMethodName = "Invoke";
  43
  44                 Expression instance_expr;
  45                 ReturnParameter return_attributes;
  46
  47                 const Modifiers MethodModifiers = Modifiers.PUBLIC | Modifiers.VIRTUAL;
  48
  49                 const Modifiers AllowedModifiers =
  50                         Modifiers.NEW |
  51                         Modifiers.PUBLIC |
  52                         Modifiers.PROTECTED |
  53                         Modifiers.INTERNAL |
  54                         Modifiers.UNSAFE |
  55                         Modifiers.PRIVATE;
  56
  57                 public Delegate (NamespaceContainer ns, DeclSpace parent, FullNamedExpression type,
  58                                  Modifiers mod_flags, MemberName name, ParametersCompiled param_list,
  59                                  Attributes attrs)
  60                         : base (ns, parent, name, attrs, MemberKind.Delegate)
  61
  62                 {
  63                         this.ReturnType = type;
  64                         ModFlags        = ModifiersExtensions.Check (AllowedModifiers, mod_flags,
  65                                                            IsTopLevel ? Modifiers.INTERNAL :
  66                                                            Modifiers.PRIVATE, name.Location, Report);
  67                         parameters      = param_list;
  68                         spec = new TypeSpec (Kind, null, this, null, ModFlags | Modifiers.SEALED);
  69                 }
  70
  71                 #region Properties
  72                 public TypeSpec MemberType {
  73                         get {
  74                                 return ReturnType.Type;
  75                         }
  76                 }
  77
  78                 public AParametersCollection Parameters {
  79                         get {
  80                                 return parameters;
  81                         }
  82                 }
  83                 #endregion
  84
  85                 public override void Accept (StructuralVisitor visitor)
  86                 {
  87                         visitor.Visit (this);
  88                 }
  89
  90                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
  91                 {
  92                         if (a.Target == AttributeTargets.ReturnValue) {
  93                                 if (return_attributes == null)
  94                                         return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);
  95
  96                                 return_attributes.ApplyAttributeBuilder (a, ctor, cdata, pa);
  97                                 return;
  98                         }
  99
 100                         base.ApplyAttributeBuilder (a, ctor, cdata, pa);
 101                 }
 102
 103                 public override AttributeTargets AttributeTargets {
 104                         get {
 105                                 return AttributeTargets.Delegate;
 106                         }
 107                 }
 108
 109                 protected override bool DoDefineMembers ()
 110                 {
 111                         var builtin_types = Compiler.BuiltinTypes;
 112
 113                         var ctor_parameters = ParametersCompiled.CreateFullyResolved (
 114                                 new [] {
 115                                         new Parameter (new TypeExpression (builtin_types.Object, Location), "object", Parameter.Modifier.NONE, null, Location),
 116                                         new Parameter (new TypeExpression (builtin_types.IntPtr, Location), "method", Parameter.Modifier.NONE, null, Location)
 117                                 },
 118                                 new [] {
 119                                         builtin_types.Object,
 120                                         builtin_types.IntPtr
 121                                 }
 122                         );
 123
 124                         Constructor = new Constructor (this, Constructor.ConstructorName,
 125                                 Modifiers.PUBLIC, null, ctor_parameters, null, Location);
 126                         Constructor.Define ();
 127
 128                         //
 129                         // Here the various methods like Invoke, BeginInvoke etc are defined
 130                         //
 131                         // First, call the `out of band' special method for
 132                         // defining recursively any types we need:
 133                         //
 134                         var p = parameters;
 135
 136                         if (!p.Resolve (this))
 137                                 return false;
 138
 139                         //
 140                         // Invoke method
 141                         //
 142
 143                         // Check accessibility
 144                         foreach (var partype in p.Types) {
 145                                 if (!IsAccessibleAs (partype)) {
 146                                         Report.SymbolRelatedToPreviousError (partype);
 147                                         Report.Error (59, Location,
 148                                                 "Inconsistent accessibility: parameter type `{0}' is less accessible than delegate `{1}'",
 149                                                 TypeManager.CSharpName (partype), GetSignatureForError ());
 150                                 }
 151                         }
 152
 153                         var ret_type = ReturnType.ResolveAsType (this);
 154                         if (ret_type == null)
 155                                 return false;
 156
 157                         //
 158                         // We don't have to check any others because they are all
 159                         // guaranteed to be accessible - they are standard types.
 160                         //
 161                         if (!IsAccessibleAs (ret_type)) {
 162                                 Report.SymbolRelatedToPreviousError (ret_type);
 163                                 Report.Error (58, Location,
 164                                                   "Inconsistent accessibility: return type `" +
 165                                                   TypeManager.CSharpName (ret_type) + "' is less " +
 166                                                   "accessible than delegate `" + GetSignatureForError () + "'");
 167                                 return false;
 168                         }
 169
 170                         CheckProtectedModifier ();
 171
 172                         if (Compiler.Settings.StdLib && ret_type.IsSpecialRuntimeType) {
 173                                 Method.Error1599 (Location, ret_type, Report);
 174                                 return false;
 175                         }
 176
 177                         TypeManager.CheckTypeVariance (ret_type, Variance.Covariant, this);
 178
 179                         InvokeBuilder = new Method (this, null, ReturnType, MethodModifiers, new MemberName (InvokeMethodName), p, null);
 180                         InvokeBuilder.Define ();
 181
 182                         //
 183                         // Don't emit async method for compiler generated delegates (e.g. dynamic site containers)
 184                         //
 185                         if (!IsCompilerGenerated) {
 186                                 DefineAsyncMethods (Parameters.CallingConvention);
 187                         }
 188
 189                         return true;
 190                 }
 191
 192                 void DefineAsyncMethods (CallingConventions cc)
 193                 {
 194                         var iasync_result = Module.PredefinedTypes.IAsyncResult;
 195                         var async_callback = Module.PredefinedTypes.AsyncCallback;
 196
 197                         //
 198                         // It's ok when async types don't exist, the delegate will have Invoke method only
 199                         //
 200                         if (!iasync_result.Define () || !async_callback.Define ())
 201                                 return;
 202
 203                         //
 204                         // BeginInvoke
 205                         //
 206                         ParametersCompiled async_parameters;
 207                         if (Parameters.Count == 0) {
 208                                 async_parameters = ParametersCompiled.EmptyReadOnlyParameters;
 209                         } else {
 210                                 var compiled = new Parameter[Parameters.Count];
 211                                 for (int i = 0; i < compiled.Length; ++i) {
 212                                         var p = parameters[i];
 213                                         compiled[i] = new Parameter (new TypeExpression (parameters.Types[i], Location),
 214                                                 p.Name,
 215                                                 p.ModFlags & (Parameter.Modifier.REF | Parameter.Modifier.OUT),
 216                                                 p.OptAttributes == null ? null : p.OptAttributes.Clone (), Location);
 217                                 }
 218
 219                                 async_parameters = new ParametersCompiled (compiled);
 220                         }
 221
 222                         async_parameters = ParametersCompiled.MergeGenerated (Compiler, async_parameters, false,
 223                                 new Parameter[] {
 224                                         new Parameter (new TypeExpression (async_callback.TypeSpec, Location), "callback", Parameter.Modifier.NONE, null, Location),
 225                                         new Parameter (new TypeExpression (Compiler.BuiltinTypes.Object, Location), "object", Parameter.Modifier.NONE, null, Location)
 226                                 },
 227                                 new [] {
 228                                         async_callback.TypeSpec,
 229                                         Compiler.BuiltinTypes.Object
 230                                 }
 231                         );
 232
 233                         BeginInvokeBuilder = new Method (this, null,
 234                                 new TypeExpression (iasync_result.TypeSpec, Location), MethodModifiers,
 235                                 new MemberName ("BeginInvoke"), async_parameters, null);
 236                         BeginInvokeBuilder.Define ();
 237
 238                         //
 239                         // EndInvoke is a bit more interesting, all the parameters labeled as
 240                         // out or ref have to be duplicated here.
 241                         //
 242
 243                         //
 244                         // Define parameters, and count out/ref parameters
 245                         //
 246                         ParametersCompiled end_parameters;
 247                         int out_params = 0;
 248
 249                         foreach (Parameter p in Parameters.FixedParameters) {
 250                                 if ((p.ModFlags & Parameter.Modifier.ISBYREF) != 0)
 251                                         ++out_params;
 252                         }
 253
 254                         if (out_params > 0) {
 255                                 Parameter[] end_params = new Parameter[out_params];
 256
 257                                 int param = 0;
 258                                 for (int i = 0; i < Parameters.FixedParameters.Length; ++i) {
 259                                         Parameter p = parameters [i];
 260                                         if ((p.ModFlags & Parameter.Modifier.ISBYREF) == 0)
 261                                                 continue;
 262
 263                                         end_params [param++] = new Parameter (new TypeExpression (p.Type, Location),
 264                                                 p.Name,
 265                                                 p.ModFlags & (Parameter.Modifier.REF | Parameter.Modifier.OUT),
 266                                                 p.OptAttributes == null ? null : p.OptAttributes.Clone (), Location);
 267                                 }
 268
 269                                 end_parameters = new ParametersCompiled (end_params);
 270                         } else {
 271                                 end_parameters = ParametersCompiled.EmptyReadOnlyParameters;
 272                         }
 273
 274                         end_parameters = ParametersCompiled.MergeGenerated (Compiler, end_parameters, false,
 275                                 new Parameter (
 276                                         new TypeExpression (iasync_result.TypeSpec, Location),
 277                                         "result", Parameter.Modifier.NONE, null, Location),
 278                                 iasync_result.TypeSpec);
 279
 280                         //
 281                         // Create method, define parameters, register parameters with type system
 282                         //
 283                         EndInvokeBuilder = new Method (this, null, ReturnType, MethodModifiers, new MemberName ("EndInvoke"), end_parameters, null);
 284                         EndInvokeBuilder.Define ();
 285                 }
 286
 287                 public override void DefineConstants ()
 288                 {
 289                         if (!Parameters.IsEmpty) {
 290                                 parameters.ResolveDefaultValues (this);
 291                         }
 292                 }
 293
 294                 public override void EmitType ()
 295                 {
 296                         if (ReturnType.Type != null) {
 297                                 if (ReturnType.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 298                                         return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);
 299                                         Module.PredefinedAttributes.Dynamic.EmitAttribute (return_attributes.Builder);
 300                                 } else if (ReturnType.Type.HasDynamicElement) {
 301                                         return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);
 302                                         Module.PredefinedAttributes.Dynamic.EmitAttribute (return_attributes.Builder, ReturnType.Type, Location);
 303                                 }
 304
 305                                 ConstraintChecker.Check (this, ReturnType.Type, ReturnType.Location);
 306                         }
 307
 308                         Constructor.ParameterInfo.ApplyAttributes (this, Constructor.ConstructorBuilder);
 309                         Constructor.ConstructorBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
 310
 311                         parameters.CheckConstraints (this);
 312                         parameters.ApplyAttributes (this, InvokeBuilder.MethodBuilder);
 313                         InvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
 314
 315                         if (BeginInvokeBuilder != null) {
 316                                 BeginInvokeBuilder.ParameterInfo.ApplyAttributes (this, BeginInvokeBuilder.MethodBuilder);
 317                                 EndInvokeBuilder.ParameterInfo.ApplyAttributes (this, EndInvokeBuilder.MethodBuilder);
 318
 319                                 BeginInvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
 320                                 EndInvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
 321                         }
 322
 323                         if (OptAttributes != null) {
 324                                 OptAttributes.Emit ();
 325                         }
 326
 327                         base.Emit ();
 328                 }
 329
 330                 protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
 331                 {
 332                         base_type = Compiler.BuiltinTypes.MulticastDelegate;
 333                         base_class = null;
 334                         return null;
 335                 }
 336
 337                 protected override TypeAttributes TypeAttr {
 338                         get {
 339                                 return ModifiersExtensions.TypeAttr (ModFlags, IsTopLevel) |
 340                                         TypeAttributes.Class | TypeAttributes.Sealed |
 341                                         base.TypeAttr;
 342                         }
 343                 }
 344
 345                 public override string[] ValidAttributeTargets {
 346                         get {
 347                                 return attribute_targets;
 348                         }
 349                 }
 350
 351                 //TODO: duplicate
 352                 protected override bool VerifyClsCompliance ()
 353                 {
 354                         if (!base.VerifyClsCompliance ()) {
 355                                 return false;
 356                         }
 357
 358                         parameters.VerifyClsCompliance (this);
 359
 360                         if (!InvokeBuilder.MemberType.IsCLSCompliant ()) {
 361                                 Report.Warning (3002, 1, Location, "Return type of `{0}' is not CLS-compliant",
 362                                         GetSignatureForError ());
 363                         }
 364                         return true;
 365                 }
 366
 367
 368                 public static MethodSpec GetConstructor (TypeSpec delType)
 369                 {
 370                         var ctor = MemberCache.FindMember (delType, MemberFilter.Constructor (null), BindingRestriction.DeclaredOnly);
 371                         return (MethodSpec) ctor;
 372                 }
 373
 374                 //
 375                 // Returns the "Invoke" from a delegate type
 376                 //
 377                 public static MethodSpec GetInvokeMethod (TypeSpec delType)
 378                 {
 379                         var invoke = MemberCache.FindMember (delType,
 380                                 MemberFilter.Method (InvokeMethodName, 0, null, null),
 381                                 BindingRestriction.DeclaredOnly);
 382
 383                         return (MethodSpec) invoke;
 384                 }
 385
 386                 public static AParametersCollection GetParameters (TypeSpec delType)
 387                 {
 388                         var invoke_mb = GetInvokeMethod (delType);
 389                         return invoke_mb.Parameters;
 390                 }
 391
 392                 //
 393                 // 15.2 Delegate compatibility
 394                 //
 395                 public static bool IsTypeCovariant (ResolveContext rc, TypeSpec a, TypeSpec b)
 396                 {
 397                         //
 398                         // For each value parameter (a parameter with no ref or out modifier), an
 399                         // identity conversion or implicit reference conversion exists from the
 400                         // parameter type in D to the corresponding parameter type in M
 401                         //
 402                         if (a == b)
 403                                 return true;
 404
 405                         if (rc.Module.Compiler.Settings.Version == LanguageVersion.ISO_1)
 406                                 return false;
 407
 408                         if (a.IsGenericParameter && b.IsGenericParameter)
 409                                 return a == b;
 410
 411                         return Convert.ImplicitReferenceConversionExists (a, b);
 412                 }
 413
 414                 public static string FullDelegateDesc (MethodSpec invoke_method)
 415                 {
 416                         return TypeManager.GetFullNameSignature (invoke_method).Replace (".Invoke", "");
 417                 }
 418
 419                 public Expression InstanceExpression {
 420                         get {
 421                                 return instance_expr;
 422                         }
 423                         set {
 424                                 instance_expr = value;
 425                         }
 426                 }
 427         }
 428
 429         //
 430         // Base class for `NewDelegate' and `ImplicitDelegateCreation'
 431         //
 432         public abstract class DelegateCreation : Expression, OverloadResolver.IErrorHandler
 433         {
 434                 protected MethodSpec constructor_method;
 435                 protected MethodGroupExpr method_group;
 436
 437                 public override bool ContainsEmitWithAwait ()
 438                 {
 439                         return false;
 440                 }
 441
 442                 public static Arguments CreateDelegateMethodArguments (AParametersCollection pd, TypeSpec[] types, Location loc)
 443                 {
 444                         Arguments delegate_arguments = new Arguments (pd.Count);
 445                         for (int i = 0; i < pd.Count; ++i) {
 446                                 Argument.AType atype_modifier;
 447                                 switch (pd.FixedParameters [i].ModFlags) {
 448                                 case Parameter.Modifier.REF:
 449                                         atype_modifier = Argument.AType.Ref;
 450                                         break;
 451                                 case Parameter.Modifier.OUT:
 452                                         atype_modifier = Argument.AType.Out;
 453                                         break;
 454                                 default:
 455                                         atype_modifier = 0;
 456                                         break;
 457                                 }
 458
 459                                 delegate_arguments.Add (new Argument (new TypeExpression (types [i], loc), atype_modifier));
 460                         }
 461
 462                         return delegate_arguments;
 463                 }
 464
 465                 public override Expression CreateExpressionTree (ResolveContext ec)
 466                 {
 467                         MemberAccess ma = new MemberAccess (new MemberAccess (new QualifiedAliasMember ("global", "System", loc), "Delegate", loc), "CreateDelegate", loc);
 468
 469                         Arguments args = new Arguments (3);
 470                         args.Add (new Argument (new TypeOf (type, loc)));
 471
 472                         if (method_group.InstanceExpression == null)
 473                                 args.Add (new Argument (new NullLiteral (loc)));
 474                         else
 475                                 args.Add (new Argument (method_group.InstanceExpression));
 476
 477                         args.Add (new Argument (method_group.CreateExpressionTree (ec)));
 478                         Expression e = new Invocation (ma, args).Resolve (ec);
 479                         if (e == null)
 480                                 return null;
 481
 482                         e = Convert.ExplicitConversion (ec, e, type, loc);
 483                         if (e == null)
 484                                 return null;
 485
 486                         return e.CreateExpressionTree (ec);
 487                 }
 488
 489                 protected override Expression DoResolve (ResolveContext ec)
 490                 {
 491                         constructor_method = Delegate.GetConstructor (type);
 492
 493                         var invoke_method = Delegate.GetInvokeMethod (type);
 494
 495                         Arguments arguments = CreateDelegateMethodArguments (invoke_method.Parameters, invoke_method.Parameters.Types, loc);
 496                         method_group = method_group.OverloadResolve (ec, ref arguments, this, OverloadResolver.Restrictions.CovariantDelegate);
 497                         if (method_group == null)
 498                                 return null;
 499
 500                         var delegate_method = method_group.BestCandidate;
 501
 502                         if (delegate_method.DeclaringType.IsNullableType) {
 503                                 ec.Report.Error (1728, loc, "Cannot create delegate from method `{0}' because it is a member of System.Nullable<T> type",
 504                                         delegate_method.GetSignatureForError ());
 505                                 return null;
 506                         }
 507
 508                         Invocation.IsSpecialMethodInvocation (ec, delegate_method, loc);
 509
 510                         ExtensionMethodGroupExpr emg = method_group as ExtensionMethodGroupExpr;
 511                         if (emg != null) {
 512                                 method_group.InstanceExpression = emg.ExtensionExpression;
 513                                 TypeSpec e_type = emg.ExtensionExpression.Type;
 514                                 if (TypeSpec.IsValueType (e_type)) {
 515                                         ec.Report.Error (1113, loc, "Extension method `{0}' of value type `{1}' cannot be used to create delegates",
 516                                                 delegate_method.GetSignatureForError (), TypeManager.CSharpName (e_type));
 517                                 }
 518                         }
 519
 520                         TypeSpec rt = delegate_method.ReturnType;
 521                         if (!Delegate.IsTypeCovariant (ec, rt, invoke_method.ReturnType)) {
 522                                 Expression ret_expr = new TypeExpression (rt, loc);
 523                                 Error_ConversionFailed (ec, delegate_method, ret_expr);
 524                         }
 525
 526                         if (delegate_method.IsConditionallyExcluded (ec.Module.Compiler, loc)) {
 527                                 ec.Report.SymbolRelatedToPreviousError (delegate_method);
 528                                 MethodOrOperator m = delegate_method.MemberDefinition as MethodOrOperator;
 529                                 if (m != null && m.IsPartialDefinition) {
 530                                         ec.Report.Error (762, loc, "Cannot create delegate from partial method declaration `{0}'",
 531                                                 delegate_method.GetSignatureForError ());
 532                                 } else {
 533                                         ec.Report.Error (1618, loc, "Cannot create delegate with `{0}' because it has a Conditional attribute",
 534                                                 TypeManager.CSharpSignature (delegate_method));
 535                                 }
 536                         }
 537
 538                         var expr = method_group.InstanceExpression;
 539                         if (expr != null && (expr.Type.IsGenericParameter || !TypeSpec.IsReferenceType (expr.Type)))
 540                                 method_group.InstanceExpression = new BoxedCast (expr, ec.BuiltinTypes.Object);
 541
 542                         eclass = ExprClass.Value;
 543                         return this;
 544                 }
 545
 546                 public override void Emit (EmitContext ec)
 547                 {
 548                         if (method_group.InstanceExpression == null)
 549                                 ec.EmitNull ();
 550                         else
 551                                 method_group.InstanceExpression.Emit (ec);
 552
 553                         var delegate_method = method_group.BestCandidate;
 554
 555                         // Any delegate must be sealed
 556                         if (!delegate_method.DeclaringType.IsDelegate && delegate_method.IsVirtual && !method_group.IsBase) {
 557                                 ec.Emit (OpCodes.Dup);
 558                                 ec.Emit (OpCodes.Ldvirtftn, delegate_method);
 559                         } else {
 560                                 ec.Emit (OpCodes.Ldftn, delegate_method);
 561                         }
 562
 563                         ec.Emit (OpCodes.Newobj, constructor_method);
 564                 }
 565
 566                 void Error_ConversionFailed (ResolveContext ec, MethodSpec method, Expression return_type)
 567                 {
 568                         var invoke_method = Delegate.GetInvokeMethod (type);
 569                         string member_name = method_group.InstanceExpression != null ?
 570                                 Delegate.FullDelegateDesc (method) :
 571                                 TypeManager.GetFullNameSignature (method);
 572
 573                         ec.Report.SymbolRelatedToPreviousError (type);
 574                         ec.Report.SymbolRelatedToPreviousError (method);
 575                         if (ec.Module.Compiler.Settings.Version == LanguageVersion.ISO_1) {
 576                                 ec.Report.Error (410, loc, "A method or delegate `{0} {1}' parameters and return type must be same as delegate `{2} {3}' parameters and return type",
 577                                         TypeManager.CSharpName (method.ReturnType), member_name,
 578                                         TypeManager.CSharpName (invoke_method.ReturnType), Delegate.FullDelegateDesc (invoke_method));
 579                                 return;
 580                         }
 581
 582                         if (return_type == null) {
 583                                 ec.Report.Error (123, loc, "A method or delegate `{0}' parameters do not match delegate `{1}' parameters",
 584                                         member_name, Delegate.FullDelegateDesc (invoke_method));
 585                                 return;
 586                         }
 587
 588                         ec.Report.Error (407, loc, "A method or delegate `{0} {1}' return type does not match delegate `{2} {3}' return type",
 589                                 return_type.GetSignatureForError (), member_name,
 590                                 TypeManager.CSharpName (invoke_method.ReturnType), Delegate.FullDelegateDesc (invoke_method));
 591                 }
 592
 593                 public static bool ImplicitStandardConversionExists (ResolveContext ec, MethodGroupExpr mg, TypeSpec target_type)
 594                 {
 595 //                      if (target_type == TypeManager.delegate_type || target_type == TypeManager.multicast_delegate_type)
 596 //                              return false;
 597
 598                         var invoke = Delegate.GetInvokeMethod (target_type);
 599
 600                         Arguments arguments = CreateDelegateMethodArguments (invoke.Parameters, invoke.Parameters.Types, mg.Location);
 601                         return mg.OverloadResolve (ec, ref arguments, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly) != null;
 602                 }
 603
 604                 #region IErrorHandler Members
 605
 606                 bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext ec, MemberSpec best, MemberSpec ambiguous)
 607                 {
 608                         return false;
 609                 }
 610
 611                 bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
 612                 {
 613                         Error_ConversionFailed (rc, best as MethodSpec, null);
 614                         return true;
 615                 }
 616
 617                 bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
 618                 {
 619                         Error_ConversionFailed (rc, best as MethodSpec, null);
 620                         return true;
 621                 }
 622
 623                 bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
 624                 {
 625                         return false;
 626                 }
 627
 628                 #endregion
 629         }
 630
 631         //
 632         // Created from the conversion code
 633         //
 634         public class ImplicitDelegateCreation : DelegateCreation
 635         {
 636                 ImplicitDelegateCreation (TypeSpec t, MethodGroupExpr mg, Location l)
 637                 {
 638                         type = t;
 639                         this.method_group = mg;
 640                         loc = l;
 641                 }
 642
 643                 static public Expression Create (ResolveContext ec, MethodGroupExpr mge,
 644                                                  TypeSpec target_type, Location loc)
 645                 {
 646                         ImplicitDelegateCreation d = new ImplicitDelegateCreation (target_type, mge, loc);
 647                         return d.DoResolve (ec);
 648                 }
 649         }
 650
 651         //
 652         // A delegate-creation-expression, invoked from the `New' class
 653         //
 654         public class NewDelegate : DelegateCreation
 655         {
 656                 public Arguments Arguments;
 657
 658                 //
 659                 // This constructor is invoked from the `New' expression
 660                 //
 661                 public NewDelegate (TypeSpec type, Arguments Arguments, Location loc)
 662                 {
 663                         this.type = type;
 664                         this.Arguments = Arguments;
 665                         this.loc  = loc;
 666                 }
 667
 668                 protected override Expression DoResolve (ResolveContext ec)
 669                 {
 670                         if (Arguments == null || Arguments.Count != 1) {
 671                                 ec.Report.Error (149, loc, "Method name expected");
 672                                 return null;
 673                         }
 674
 675                         Argument a = Arguments [0];
 676                         if (!a.ResolveMethodGroup (ec))
 677                                 return null;
 678
 679                         Expression e = a.Expr;
 680
 681                         AnonymousMethodExpression ame = e as AnonymousMethodExpression;
 682                         if (ame != null && ec.Module.Compiler.Settings.Version != LanguageVersion.ISO_1) {
 683                                 e = ame.Compatible (ec, type);
 684                                 if (e == null)
 685                                         return null;
 686
 687                                 return e.Resolve (ec);
 688                         }
 689
 690                         method_group = e as MethodGroupExpr;
 691                         if (method_group == null) {
 692                                 if (e.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 693                                         e = Convert.ImplicitConversionRequired (ec, e, type, loc);
 694                                 } else if (!e.Type.IsDelegate) {
 695                                         e.Error_UnexpectedKind (ec, ResolveFlags.MethodGroup | ResolveFlags.Type, loc);
 696                                         return null;
 697                                 }
 698
 699                                 //
 700                                 // An argument is not a method but another delegate
 701                                 //
 702                                 method_group = new MethodGroupExpr (Delegate.GetInvokeMethod (e.Type), e.Type, loc);
 703                                 method_group.InstanceExpression = e;
 704                         }
 705
 706                         return base.DoResolve (ec);
 707                 }
 708         }
 709
 710         //
 711         // Invocation converted to delegate Invoke call
 712         //
 713         class DelegateInvocation : ExpressionStatement
 714         {
 715                 readonly Expression InstanceExpr;
 716                 Arguments arguments;
 717                 MethodSpec method;
 718
 719                 public DelegateInvocation (Expression instance_expr, Arguments args, Location loc)
 720                 {
 721                         this.InstanceExpr = instance_expr;
 722                         this.arguments = args;
 723                         this.loc = loc;
 724                 }
 725
 726                 public override bool ContainsEmitWithAwait ()
 727                 {
 728                         return InstanceExpr.ContainsEmitWithAwait () || (arguments != null && arguments.ContainsEmitWithAwait ());
 729                 }
 730
 731                 public override Expression CreateExpressionTree (ResolveContext ec)
 732                 {
 733                         Arguments args = Arguments.CreateForExpressionTree (ec, this.arguments,
 734                                 InstanceExpr.CreateExpressionTree (ec));
 735
 736                         return CreateExpressionFactoryCall (ec, "Invoke", args);
 737                 }
 738
 739                 protected override Expression DoResolve (ResolveContext ec)
 740                 {
 741                         TypeSpec del_type = InstanceExpr.Type;
 742                         if (del_type == null)
 743                                 return null;
 744
 745                         //
 746                         // Do only core overload resolution the rest of the checks has been
 747                         // done on primary expression
 748                         //
 749                         method = Delegate.GetInvokeMethod (del_type);
 750                         var res = new OverloadResolver (new MemberSpec[] { method }, OverloadResolver.Restrictions.DelegateInvoke, loc);
 751                         var valid = res.ResolveMember<MethodSpec> (ec, ref arguments);
 752                         if (valid == null && !res.BestCandidateIsDynamic)
 753                                 return null;
 754
 755                         type = method.ReturnType;
 756                         eclass = ExprClass.Value;
 757                         return this;
 758                 }
 759
 760                 public override void Emit (EmitContext ec)
 761                 {
 762                         //
 763                         // Invocation on delegates call the virtual Invoke member
 764                         // so we are always `instance' calls
 765                         //
 766                         var call = new CallEmitter ();
 767                         call.InstanceExpression = InstanceExpr;
 768                         call.EmitPredefined (ec, method, arguments);
 769                 }
 770
 771                 public override void EmitStatement (EmitContext ec)
 772                 {
 773                         Emit (ec);
 774                         //
 775                         // Pop the return value if there is one
 776                         //
 777                         if (type.Kind != MemberKind.Void)
 778                                 ec.Emit (OpCodes.Pop);
 779                 }
 780
 781                 public override System.Linq.Expressions.Expression MakeExpression (BuilderContext ctx)
 782                 {
 783                         return Invocation.MakeExpression (ctx, InstanceExpr, method, arguments);
 784                 }
 785         }
 786 }