mcs/mcs/generic.cs

   1 //
   2 // generic.cs: Generics support
   3 //
   4 // Authors: Martin Baulig (martin@ximian.com)
   5 //          Miguel de Icaza (miguel@ximian.com)
   6 //          Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Dual licensed under the terms of the MIT X11 or GNU GPL
   9 //
  10 // Copyright 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
  11 // Copyright 2004-2008 Novell, Inc
  12 // Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
  13 //
  14
  15 using System;
  16 using System.Collections.Generic;
  17 using System.Text;
  18 using System.Linq;
  19
  20 #if STATIC
  21 using MetaType = IKVM.Reflection.Type;
  22 using IKVM.Reflection;
  23 using IKVM.Reflection.Emit;
  24 #else
  25 using MetaType = System.Type;
  26 using System.Reflection;
  27 using System.Reflection.Emit;
  28 #endif
  29
  30 namespace Mono.CSharp {
  31         public class VarianceDecl
  32         {
  33                 public VarianceDecl (Variance variance, Location loc)
  34                 {
  35                         this.Variance = variance;
  36                         this.Location = loc;
  37                 }
  38
  39                 public Variance Variance { get; private set; }
  40                 public Location Location { get; private set; }
  41
  42                 public static Variance CheckTypeVariance (TypeSpec t, Variance expected, IMemberContext member)
  43                 {
  44                         var tp = t as TypeParameterSpec;
  45                         if (tp != null) {
  46                                 var v = tp.Variance;
  47                                 if (expected == Variance.None && v != expected ||
  48                                         expected == Variance.Covariant && v == Variance.Contravariant ||
  49                                         expected == Variance.Contravariant && v == Variance.Covariant) {
  50                                         ((TypeParameter) tp.MemberDefinition).ErrorInvalidVariance (member, expected);
  51                                 }
  52
  53                                 return expected;
  54                         }
  55
  56                         if (t.TypeArguments.Length > 0) {
  57                                 var targs_definition = t.MemberDefinition.TypeParameters;
  58                                 TypeSpec[] targs = TypeManager.GetTypeArguments (t);
  59                                 for (int i = 0; i < targs.Length; ++i) {
  60                                         var v = targs_definition[i].Variance;
  61                                         CheckTypeVariance (targs[i], (Variance) ((int) v * (int) expected), member);
  62                                 }
  63
  64                                 return expected;
  65                         }
  66
  67                         var ac = t as ArrayContainer;
  68                         if (ac != null)
  69                                 return CheckTypeVariance (ac.Element, expected, member);
  70
  71                         return Variance.None;
  72                 }
  73         }
  74
  75         public enum Variance
  76         {
  77                 //
  78                 // Don't add or modify internal values, they are used as -/+ calculation signs
  79                 //
  80                 None                    = 0,
  81                 Covariant               = 1,
  82                 Contravariant   = -1
  83         }
  84
  85         [Flags]
  86         public enum SpecialConstraint
  87         {
  88                 None            = 0,
  89                 Constructor = 1 << 2,
  90                 Class           = 1 << 3,
  91                 Struct          = 1 << 4
  92         }
  93
  94         public class SpecialContraintExpr : FullNamedExpression
  95         {
  96                 public SpecialContraintExpr (SpecialConstraint constraint, Location loc)
  97                 {
  98                         this.loc = loc;
  99                         this.Constraint = constraint;
 100                 }
 101
 102                 public SpecialConstraint Constraint { get; private set; }
 103
 104                 protected override Expression DoResolve (ResolveContext rc)
 105                 {
 106                         throw new NotImplementedException ();
 107                 }
 108
 109                 public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext mc, bool allowUnboundTypeArguments)
 110                 {
 111                         throw new NotImplementedException ();
 112                 }
 113         }
 114
 115         //
 116         // A set of parsed constraints for a type parameter
 117         //
 118         public class Constraints
 119         {
 120                 readonly SimpleMemberName tparam;
 121                 readonly List<FullNamedExpression> constraints;
 122                 readonly Location loc;
 123                 bool resolved;
 124                 bool resolving;
 125
 126                 public Constraints (SimpleMemberName tparam, List<FullNamedExpression> constraints, Location loc)
 127                 {
 128                         this.tparam = tparam;
 129                         this.constraints = constraints;
 130                         this.loc = loc;
 131                 }
 132
 133                 #region Properties
 134
 135                 public List<FullNamedExpression> TypeExpressions {
 136                         get {
 137                                 return constraints;
 138                         }
 139                 }
 140
 141                 public Location Location {
 142                         get {
 143                                 return loc;
 144                         }
 145                 }
 146
 147                 public SimpleMemberName TypeParameter {
 148                         get {
 149                                 return tparam;
 150                         }
 151                 }
 152
 153                 #endregion
 154
 155                 public static bool CheckConflictingInheritedConstraint (TypeParameterSpec spec, TypeSpec bb, IMemberContext context, Location loc)
 156                 {
 157                         if (spec.HasSpecialClass && bb.IsStruct) {
 158                                 context.Module.Compiler.Report.Error (455, loc,
 159                                         "Type parameter `{0}' inherits conflicting constraints `{1}' and `{2}'",
 160                                         spec.Name, "class", bb.GetSignatureForError ());
 161
 162                                 return false;
 163                         }
 164
 165                         return CheckConflictingInheritedConstraint (spec, spec.BaseType, bb, context, loc);
 166                 }
 167
 168                 static bool CheckConflictingInheritedConstraint (TypeParameterSpec spec, TypeSpec ba, TypeSpec bb, IMemberContext context, Location loc)
 169                 {
 170                         if (ba == bb)
 171                                 return true;
 172
 173                         if (TypeSpec.IsBaseClass (ba, bb, false) || TypeSpec.IsBaseClass (bb, ba, false))
 174                                 return true;
 175
 176                         Error_ConflictingConstraints (context, spec, ba, bb, loc);
 177                         return false;
 178                 }
 179
 180                 public static void Error_ConflictingConstraints (IMemberContext context, TypeParameterSpec tp, TypeSpec ba, TypeSpec bb, Location loc)
 181                 {
 182                         context.Module.Compiler.Report.Error (455, loc,
 183                                 "Type parameter `{0}' inherits conflicting constraints `{1}' and `{2}'",
 184                                 tp.Name, ba.GetSignatureForError (), bb.GetSignatureForError ());
 185                 }
 186
 187                 public void CheckGenericConstraints (IMemberContext context, bool obsoleteCheck)
 188                 {
 189                         foreach (var c in constraints) {
 190                                 if (c == null)
 191                                         continue;
 192
 193                                 var t = c.Type;
 194                                 if (t == null)
 195                                         continue;
 196
 197                                 if (obsoleteCheck) {
 198                                         ObsoleteAttribute obsolete_attr = t.GetAttributeObsolete ();
 199                                         if (obsolete_attr != null)
 200                                                 AttributeTester.Report_ObsoleteMessage (obsolete_attr, t.GetSignatureForError (), c.Location, context.Module.Compiler.Report);
 201                                 }
 202
 203                                 ConstraintChecker.Check (context, t, c.Location);
 204                         }
 205                 }
 206
 207                 //
 208                 // Resolve the constraints types with only possible early checks, return
 209                 // value `false' is reserved for recursive failure
 210                 //
 211                 public bool Resolve (IMemberContext context, TypeParameter tp)
 212                 {
 213                         if (resolved)
 214                                 return true;
 215
 216                         if (resolving)
 217                                 return false;
 218
 219                         resolving = true;
 220                         var spec = tp.Type;
 221                         List<TypeParameterSpec> tparam_types = null;
 222                         bool iface_found = false;
 223
 224                         spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;
 225
 226                         for (int i = 0; i < constraints.Count; ++i) {
 227                                 var constraint = constraints[i];
 228
 229                                 if (constraint is SpecialContraintExpr) {
 230                                         spec.SpecialConstraint |= ((SpecialContraintExpr) constraint).Constraint;
 231                                         if (spec.HasSpecialStruct)
 232                                                 spec.BaseType = context.Module.Compiler.BuiltinTypes.ValueType;
 233
 234                                         // Set to null as it does not have a type
 235                                         constraints[i] = null;
 236                                         continue;
 237                                 }
 238
 239                                 var type = constraint.ResolveAsType (context);
 240                                 if (type == null)
 241                                         continue;
 242
 243                                 if (type.Arity > 0 && ((InflatedTypeSpec) type).HasDynamicArgument ()) {
 244                                         context.Module.Compiler.Report.Error (1968, constraint.Location,
 245                                                 "A constraint cannot be the dynamic type `{0}'", type.GetSignatureForError ());
 246                                         continue;
 247                                 }
 248
 249                                 if (!context.CurrentMemberDefinition.IsAccessibleAs (type)) {
 250                                         context.Module.Compiler.Report.SymbolRelatedToPreviousError (type);
 251                                         context.Module.Compiler.Report.Error (703, loc,
 252                                                 "Inconsistent accessibility: constraint type `{0}' is less accessible than `{1}'",
 253                                                 type.GetSignatureForError (), context.GetSignatureForError ());
 254                                 }
 255
 256                                 if (type.IsInterface) {
 257                                         if (!spec.AddInterface (type)) {
 258                                                 context.Module.Compiler.Report.Error (405, constraint.Location,
 259                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 260                                         }
 261
 262                                         iface_found = true;
 263                                         continue;
 264                                 }
 265
 266                                 var constraint_tp = type as TypeParameterSpec;
 267                                 if (constraint_tp != null) {
 268                                         if (tparam_types == null) {
 269                                                 tparam_types = new List<TypeParameterSpec> (2);
 270                                         } else if (tparam_types.Contains (constraint_tp)) {
 271                                                 context.Module.Compiler.Report.Error (405, constraint.Location,
 272                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 273                                                 continue;
 274                                         }
 275
 276                                         //
 277                                         // Checks whether each generic method parameter constraint type
 278                                         // is valid with respect to T
 279                                         //
 280                                         if (tp.IsMethodTypeParameter) {
 281                                                 VarianceDecl.CheckTypeVariance (type, Variance.Contravariant, context);
 282                                         }
 283
 284                                         var tp_def = constraint_tp.MemberDefinition as TypeParameter;
 285                                         if (tp_def != null && !tp_def.ResolveConstraints (context)) {
 286                                                 context.Module.Compiler.Report.Error (454, constraint.Location,
 287                                                         "Circular constraint dependency involving `{0}' and `{1}'",
 288                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 289                                                 continue;
 290                                         }
 291
 292                                         //
 293                                         // Checks whether there are no conflicts between type parameter constraints
 294                                         //
 295                                         // class Foo<T, U>
 296                                         //      where T : A
 297                                         //      where U : B, T
 298                                         //
 299                                         // A and B are not convertible and only 1 class constraint is allowed
 300                                         //
 301                                         if (constraint_tp.HasTypeConstraint) {
 302                                                 if (spec.HasTypeConstraint || spec.HasSpecialStruct) {
 303                                                         if (!CheckConflictingInheritedConstraint (spec, constraint_tp.BaseType, context, constraint.Location))
 304                                                                 continue;
 305                                                 } else {
 306                                                         for (int ii = 0; ii < tparam_types.Count; ++ii) {
 307                                                                 if (!tparam_types[ii].HasTypeConstraint)
 308                                                                         continue;
 309
 310                                                                 if (!CheckConflictingInheritedConstraint (spec, tparam_types[ii].BaseType, constraint_tp.BaseType, context, constraint.Location))
 311                                                                         break;
 312                                                         }
 313                                                 }
 314                                         }
 315
 316                                         if (constraint_tp.TypeArguments != null) {
 317                                                 var eb = constraint_tp.GetEffectiveBase ();
 318                                                 if (eb != null && !CheckConflictingInheritedConstraint (spec, eb, spec.BaseType, context, constraint.Location))
 319                                                         break;
 320                                         }
 321
 322                                         if (constraint_tp.HasSpecialStruct) {
 323                                                 context.Module.Compiler.Report.Error (456, constraint.Location,
 324                                                         "Type parameter `{0}' has the `struct' constraint, so it cannot be used as a constraint for `{1}'",
 325                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 326                                                 continue;
 327                                         }
 328
 329                                         tparam_types.Add (constraint_tp);
 330                                         continue;
 331                                 }
 332
 333                                 if (iface_found || spec.HasTypeConstraint) {
 334                                         context.Module.Compiler.Report.Error (406, constraint.Location,
 335                                                 "The class type constraint `{0}' must be listed before any other constraints. Consider moving type constraint to the beginning of the constraint list",
 336                                                 type.GetSignatureForError ());
 337                                 }
 338
 339                                 if (spec.HasSpecialStruct || spec.HasSpecialClass) {
 340                                         context.Module.Compiler.Report.Error (450, constraint.Location,
 341                                                 "`{0}': cannot specify both a constraint class and the `class' or `struct' constraint",
 342                                                 type.GetSignatureForError ());
 343                                 }
 344
 345                                 switch (type.BuiltinType) {
 346                                 case BuiltinTypeSpec.Type.Array:
 347                                 case BuiltinTypeSpec.Type.Delegate:
 348                                 case BuiltinTypeSpec.Type.MulticastDelegate:
 349                                 case BuiltinTypeSpec.Type.Enum:
 350                                 case BuiltinTypeSpec.Type.ValueType:
 351                                 case BuiltinTypeSpec.Type.Object:
 352                                         context.Module.Compiler.Report.Error (702, constraint.Location,
 353                                                 "A constraint cannot be special class `{0}'", type.GetSignatureForError ());
 354                                         continue;
 355                                 case BuiltinTypeSpec.Type.Dynamic:
 356                                         context.Module.Compiler.Report.Error (1967, constraint.Location,
 357                                                 "A constraint cannot be the dynamic type");
 358                                         continue;
 359                                 }
 360
 361                                 if (type.IsSealed || !type.IsClass) {
 362                                         context.Module.Compiler.Report.Error (701, loc,
 363                                                 "`{0}' is not a valid constraint. A constraint must be an interface, a non-sealed class or a type parameter",
 364                                                 type.GetSignatureForError ());
 365                                         continue;
 366                                 }
 367
 368                                 if (type.IsStatic) {
 369                                         context.Module.Compiler.Report.Error (717, constraint.Location,
 370                                                 "`{0}' is not a valid constraint. Static classes cannot be used as constraints",
 371                                                 type.GetSignatureForError ());
 372                                 }
 373
 374                                 spec.BaseType = type;
 375                         }
 376
 377                         if (tparam_types != null)
 378                                 spec.TypeArguments = tparam_types.ToArray ();
 379
 380                         resolving = false;
 381                         resolved = true;
 382                         return true;
 383                 }
 384
 385                 public void VerifyClsCompliance (Report report)
 386                 {
 387                         foreach (var c in constraints)
 388                         {
 389                                 if (c == null)
 390                                         continue;
 391
 392                                 if (!c.Type.IsCLSCompliant ()) {
 393                                         report.SymbolRelatedToPreviousError (c.Type);
 394                                         report.Warning (3024, 1, loc, "Constraint type `{0}' is not CLS-compliant",
 395                                                 c.Type.GetSignatureForError ());
 396                                 }
 397                         }
 398                 }
 399         }
 400
 401         //
 402         // A type parameter for a generic type or generic method definition
 403         //
 404         public class TypeParameter : MemberCore, ITypeDefinition
 405         {
 406                 static readonly string[] attribute_target = { "type parameter" };
 407
 408                 Constraints constraints;
 409                 GenericTypeParameterBuilder builder;
 410                 readonly TypeParameterSpec spec;
 411
 412                 public TypeParameter (int index, MemberName name, Constraints constraints, Attributes attrs, Variance Variance)
 413                         : base (null, name, attrs)
 414                 {
 415                         this.constraints = constraints;
 416                         this.spec = new TypeParameterSpec (null, index, this, SpecialConstraint.None, Variance, null);
 417                 }
 418
 419                 //
 420                 // Used by parser
 421                 //
 422                 public TypeParameter (MemberName name, Attributes attrs, VarianceDecl variance)
 423                         : base (null, name, attrs)
 424                 {
 425                         var var = variance == null ? Variance.None : variance.Variance;
 426                         this.spec = new TypeParameterSpec (null, -1, this, SpecialConstraint.None, var, null);
 427                         this.VarianceDecl = variance;
 428                 }
 429
 430                 public TypeParameter (TypeParameterSpec spec, TypeSpec parentSpec, MemberName name, Attributes attrs)
 431                         : base (null, name, attrs)
 432                 {
 433                         this.spec = new TypeParameterSpec (parentSpec, spec.DeclaredPosition, spec.MemberDefinition, spec.SpecialConstraint, spec.Variance, null) {
 434                                 BaseType = spec.BaseType,
 435                                 InterfacesDefined = spec.InterfacesDefined,
 436                                 TypeArguments = spec.TypeArguments
 437                         };
 438                 }
 439
 440                 #region Properties
 441
 442                 public override AttributeTargets AttributeTargets {
 443                         get {
 444                                 return AttributeTargets.GenericParameter;
 445                         }
 446                 }
 447
 448                 public Constraints Constraints {
 449                         get {
 450                                 return constraints;
 451                         }
 452                         set {
 453                                 constraints = value;
 454                         }
 455                 }
 456
 457                 public IAssemblyDefinition DeclaringAssembly {
 458                         get     {
 459                                 return Module.DeclaringAssembly;
 460                         }
 461                 }
 462
 463                 public override string DocCommentHeader {
 464                         get {
 465                                 throw new InvalidOperationException (
 466                                         "Unexpected attempt to get doc comment from " + this.GetType ());
 467                         }
 468                 }
 469
 470                 bool ITypeDefinition.IsComImport {
 471                         get {
 472                                 return false;
 473                         }
 474                 }
 475
 476                 bool ITypeDefinition.IsPartial {
 477                         get {
 478                                 return false;
 479                         }
 480                 }
 481
 482                 public bool IsMethodTypeParameter {
 483                         get {
 484                                 return spec.IsMethodOwned;
 485                         }
 486                 }
 487
 488                 bool ITypeDefinition.IsTypeForwarder {
 489                         get {
 490                                 return false;
 491                         }
 492                 }
 493
 494                 bool ITypeDefinition.IsCyclicTypeForwarder {
 495                         get {
 496                                 return false;
 497                         }
 498                 }
 499
 500                 public string Name {
 501                         get {
 502                                 return MemberName.Name;
 503                         }
 504                 }
 505
 506                 public string Namespace {
 507                         get {
 508                                 return null;
 509                         }
 510                 }
 511
 512                 public TypeParameterSpec Type {
 513                         get {
 514                                 return spec;
 515                         }
 516                 }
 517
 518                 public int TypeParametersCount {
 519                         get {
 520                                 return 0;
 521                         }
 522                 }
 523
 524                 public TypeParameterSpec[] TypeParameters {
 525                         get {
 526                                 return null;
 527                         }
 528                 }
 529
 530                 public override string[] ValidAttributeTargets {
 531                         get {
 532                                 return attribute_target;
 533                         }
 534                 }
 535
 536                 public Variance Variance {
 537                         get {
 538                                 return spec.Variance;
 539                         }
 540                 }
 541
 542                 public VarianceDecl VarianceDecl { get; private set; }
 543
 544                 #endregion
 545
 546                 //
 547                 // This is called for each part of a partial generic type definition.
 548                 //
 549                 // If partial type parameters constraints are not null and we don't
 550                 // already have constraints they become our constraints. If we already
 551                 // have constraints, we must check that they're same.
 552                 //
 553                 public bool AddPartialConstraints (TypeDefinition part, TypeParameter tp)
 554                 {
 555                         if (builder == null)
 556                                 throw new InvalidOperationException ();
 557
 558                         var new_constraints = tp.constraints;
 559                         if (new_constraints == null)
 560                                 return true;
 561
 562                         // TODO: could create spec only
 563                         //tp.Define (null, -1, part.Definition);
 564                         tp.spec.DeclaringType = part.Definition;
 565                         if (!tp.ResolveConstraints (part))
 566                                 return false;
 567
 568                         if (constraints != null)
 569                                 return spec.HasSameConstraintsDefinition (tp.Type);
 570
 571                         // Copy constraint from resolved part to partial container
 572                         spec.SpecialConstraint = tp.spec.SpecialConstraint;
 573                         spec.InterfacesDefined = tp.spec.InterfacesDefined;
 574                         spec.TypeArguments = tp.spec.TypeArguments;
 575                         spec.BaseType = tp.spec.BaseType;
 576
 577                         return true;
 578                 }
 579
 580                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 581                 {
 582                         builder.SetCustomAttribute ((ConstructorInfo) ctor.GetMetaInfo (), cdata);
 583                 }
 584
 585                 public void CheckGenericConstraints (bool obsoleteCheck)
 586                 {
 587                         if (constraints != null)
 588                                 constraints.CheckGenericConstraints (this, obsoleteCheck);
 589                 }
 590
 591                 public TypeParameter CreateHoistedCopy (TypeSpec declaringSpec)
 592                 {
 593                         return new TypeParameter (spec, declaringSpec, MemberName, null);
 594                 }
 595
 596                 public override bool Define ()
 597                 {
 598                         return true;
 599                 }
 600
 601                 //
 602                 // This is the first method which is called during the resolving
 603                 // process; we're called immediately after creating the type parameters
 604                 // with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
 605                 // MethodBuilder).
 606                 //
 607                 public void Create (TypeSpec declaringType, TypeContainer parent)
 608                 {
 609                         if (builder != null)
 610                                 throw new InternalErrorException ();
 611
 612                         // Needed to get compiler reference
 613                         this.Parent = parent;
 614                         spec.DeclaringType = declaringType;
 615                 }
 616
 617                 public void Define (GenericTypeParameterBuilder type)
 618                 {
 619                         this.builder = type;
 620                         spec.SetMetaInfo (type);
 621                 }
 622
 623                 public void Define (TypeParameter tp)
 624                 {
 625                         builder = tp.builder;
 626                 }
 627
 628                 public void EmitConstraints (GenericTypeParameterBuilder builder)
 629                 {
 630                         var attr = GenericParameterAttributes.None;
 631                         if (spec.Variance == Variance.Contravariant)
 632                                 attr |= GenericParameterAttributes.Contravariant;
 633                         else if (spec.Variance == Variance.Covariant)
 634                                 attr |= GenericParameterAttributes.Covariant;
 635
 636                         if (spec.HasSpecialClass)
 637                                 attr |= GenericParameterAttributes.ReferenceTypeConstraint;
 638                         else if (spec.HasSpecialStruct)
 639                                 attr |= GenericParameterAttributes.NotNullableValueTypeConstraint | GenericParameterAttributes.DefaultConstructorConstraint;
 640
 641                         if (spec.HasSpecialConstructor)
 642                                 attr |= GenericParameterAttributes.DefaultConstructorConstraint;
 643
 644                         if (spec.BaseType.BuiltinType != BuiltinTypeSpec.Type.Object)
 645                                 builder.SetBaseTypeConstraint (spec.BaseType.GetMetaInfo ());
 646
 647                         if (spec.InterfacesDefined != null)
 648                                 builder.SetInterfaceConstraints (spec.InterfacesDefined.Select (l => l.GetMetaInfo ()).ToArray ());
 649
 650                         if (spec.TypeArguments != null) {
 651                                 var meta_constraints = new List<MetaType> (spec.TypeArguments.Length);
 652                                 foreach (var c in spec.TypeArguments) {
 653                                         //
 654                                         // Inflated type parameters can collide with special constraint types, don't
 655                                         // emit any such type parameter.
 656                                         //
 657                                         if (c.BuiltinType == BuiltinTypeSpec.Type.Object || c.BuiltinType == BuiltinTypeSpec.Type.ValueType)
 658                                                 continue;
 659
 660                                         meta_constraints.Add (c.GetMetaInfo ());
 661                                 }
 662
 663                                 builder.SetInterfaceConstraints (meta_constraints.ToArray ());
 664                         }
 665
 666                         builder.SetGenericParameterAttributes (attr);
 667                 }
 668
 669                 public override void Emit ()
 670                 {
 671                         EmitConstraints (builder);
 672
 673                         if (OptAttributes != null)
 674                                 OptAttributes.Emit ();
 675
 676                         base.Emit ();
 677                 }
 678
 679                 public void ErrorInvalidVariance (IMemberContext mc, Variance expected)
 680                 {
 681                         Report.SymbolRelatedToPreviousError (mc.CurrentMemberDefinition);
 682                         string input_variance = Variance == Variance.Contravariant ? "contravariant" : "covariant";
 683                         string gtype_variance;
 684                         switch (expected) {
 685                         case Variance.Contravariant: gtype_variance = "contravariantly"; break;
 686                         case Variance.Covariant: gtype_variance = "covariantly"; break;
 687                         default: gtype_variance = "invariantly"; break;
 688                         }
 689
 690                         Delegate d = mc as Delegate;
 691                         string parameters = d != null ? d.Parameters.GetSignatureForError () : "";
 692
 693                         Report.Error (1961, Location,
 694                                 "The {2} type parameter `{0}' must be {3} valid on `{1}{4}'",
 695                                         GetSignatureForError (), mc.GetSignatureForError (), input_variance, gtype_variance, parameters);
 696                 }
 697
 698                 public TypeSpec GetAttributeCoClass ()
 699                 {
 700                         return null;
 701                 }
 702
 703                 public string GetAttributeDefaultMember ()
 704                 {
 705                         throw new NotSupportedException ();
 706                 }
 707
 708                 public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
 709                 {
 710                         throw new NotSupportedException ();
 711                 }
 712
 713                 public override string GetSignatureForDocumentation ()
 714                 {
 715                         throw new NotImplementedException ();
 716                 }
 717
 718                 public override string GetSignatureForError ()
 719                 {
 720                         return MemberName.Name;
 721                 }
 722
 723                 bool ITypeDefinition.IsInternalAsPublic (IAssemblyDefinition assembly)
 724                 {
 725                         return spec.MemberDefinition.DeclaringAssembly == assembly;
 726                 }
 727
 728                 public void LoadMembers (TypeSpec declaringType, bool onlyTypes, ref MemberCache cache)
 729                 {
 730                         throw new NotSupportedException ("Not supported for compiled definition");
 731                 }
 732
 733                 //
 734                 // Resolves all type parameter constraints
 735                 //
 736                 public bool ResolveConstraints (IMemberContext context)
 737                 {
 738                         if (constraints != null)
 739                                 return constraints.Resolve (context, this);
 740
 741                         if (spec.BaseType == null)
 742                                 spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;
 743
 744                         return true;
 745                 }
 746
 747                 public override bool IsClsComplianceRequired ()
 748                 {
 749                         return false;
 750                 }
 751
 752                 public new void VerifyClsCompliance ()
 753                 {
 754                         if (constraints != null)
 755                                 constraints.VerifyClsCompliance (Report);
 756                 }
 757
 758                 public void WarningParentNameConflict (TypeParameter conflict)
 759                 {
 760                         conflict.Report.SymbolRelatedToPreviousError (conflict.Location, null);
 761                         conflict.Report.Warning (693, 3, Location,
 762                                 "Type parameter `{0}' has the same name as the type parameter from outer type `{1}'",
 763                                 GetSignatureForError (), conflict.CurrentType.GetSignatureForError ());
 764                 }
 765         }
 766
 767         [System.Diagnostics.DebuggerDisplay ("{DisplayDebugInfo()}")]
 768         public class TypeParameterSpec : TypeSpec
 769         {
 770                 public static readonly new TypeParameterSpec[] EmptyTypes = new TypeParameterSpec[0];
 771
 772                 Variance variance;
 773                 SpecialConstraint spec;
 774                 int tp_pos;
 775                 TypeSpec[] targs;
 776                 TypeSpec[] ifaces_defined;
 777                 TypeSpec effective_base;
 778
 779                 //
 780                 // Creates type owned type parameter
 781                 //
 782                 public TypeParameterSpec (TypeSpec declaringType, int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
 783                         : base (MemberKind.TypeParameter, declaringType, definition, info, Modifiers.PUBLIC)
 784                 {
 785                         this.variance = variance;
 786                         this.spec = spec;
 787                         state &= ~StateFlags.Obsolete_Undetected;
 788                         tp_pos = index;
 789                 }
 790
 791                 //
 792                 // Creates method owned type parameter
 793                 //
 794                 public TypeParameterSpec (int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
 795                         : this (null, index, definition, spec, variance, info)
 796                 {
 797                 }
 798
 799                 #region Properties
 800
 801                 public int DeclaredPosition {
 802                         get {
 803                                 return tp_pos;
 804                         }
 805                         set {
 806                                 tp_pos = value;
 807                         }
 808                 }
 809
 810                 public bool HasSpecialConstructor {
 811                         get {
 812                                 return (spec & SpecialConstraint.Constructor) != 0;
 813                         }
 814                 }
 815
 816                 public bool HasSpecialClass {
 817                         get {
 818                                 return (spec & SpecialConstraint.Class) != 0;
 819                         }
 820                 }
 821
 822                 public bool HasSpecialStruct {
 823                         get {
 824                                 return (spec & SpecialConstraint.Struct) != 0;
 825                         }
 826                 }
 827
 828                 public bool HasAnyTypeConstraint {
 829                         get {
 830                                 return (spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0 || ifaces != null || targs != null || HasTypeConstraint;
 831                         }
 832                 }
 833
 834                 public bool HasTypeConstraint {
 835                         get {
 836                                 var bt = BaseType.BuiltinType;
 837                                 return bt != BuiltinTypeSpec.Type.Object && bt != BuiltinTypeSpec.Type.ValueType;
 838                         }
 839                 }
 840
 841                 public override IList<TypeSpec> Interfaces {
 842                         get {
 843                                 if ((state & StateFlags.InterfacesExpanded) == 0) {
 844                                         if (ifaces != null) {
 845                                                 if (ifaces_defined == null)
 846                                                         ifaces_defined = ifaces.ToArray ();
 847
 848                                                 for (int i = 0; i < ifaces_defined.Length; ++i ) {
 849                                                         var iface_type = ifaces_defined[i];
 850                                                         var td = iface_type.MemberDefinition as TypeDefinition;
 851                                                         if (td != null)
 852                                                                 td.DoExpandBaseInterfaces ();
 853
 854                                                         if (iface_type.Interfaces != null) {
 855                                                                 for (int ii = 0; ii < iface_type.Interfaces.Count; ++ii) {
 856                                                                         var ii_iface_type = iface_type.Interfaces [ii];
 857                                                                         AddInterface (ii_iface_type);
 858                                                                 }
 859                                                         }
 860                                                 }
 861                                         } else if (ifaces_defined == null) {
 862                                                 ifaces_defined = ifaces == null ? TypeSpec.EmptyTypes : ifaces.ToArray ();
 863                                         }
 864
 865                                         //
 866                                         // Include all base type interfaces too, see ImportTypeBase for details
 867                                         //
 868                                         if (BaseType != null) {
 869                                                 var td = BaseType.MemberDefinition as TypeDefinition;
 870                                                 if (td != null)
 871                                                         td.DoExpandBaseInterfaces ();
 872
 873                                                 if (BaseType.Interfaces != null) {
 874                                                         foreach (var iface in BaseType.Interfaces) {
 875                                                                 AddInterface (iface);
 876                                                         }
 877                                                 }
 878                                         }
 879
 880                                         state |= StateFlags.InterfacesExpanded;
 881                                 }
 882
 883                                 return ifaces;
 884                         }
 885                 }
 886
 887                 //
 888                 // Unexpanded interfaces list
 889                 //
 890                 public TypeSpec[] InterfacesDefined {
 891                         get {
 892                                 if (ifaces_defined == null) {
 893                                         ifaces_defined = ifaces == null ? TypeSpec.EmptyTypes : ifaces.ToArray ();
 894                                 }
 895
 896                                 return ifaces_defined.Length == 0 ? null : ifaces_defined;
 897                         }
 898                         set {
 899                                 ifaces_defined = value;
 900                                 if (value != null && value.Length != 0)
 901                                         ifaces = new List<TypeSpec> (value);
 902                         }
 903                 }
 904
 905                 public bool IsConstrained {
 906                         get {
 907                                 return spec != SpecialConstraint.None || ifaces != null || targs != null || HasTypeConstraint;
 908                         }
 909                 }
 910
 911                 //
 912                 // Returns whether the type parameter is known to be a reference type
 913                 //
 914                 public new bool IsReferenceType {
 915                         get {
 916                                 if ((spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
 917                                         return (spec & SpecialConstraint.Class) != 0;
 918
 919                                 //
 920                                 // Full check is needed (see IsValueType for details)
 921                                 //
 922                                 if (HasTypeConstraint && TypeSpec.IsReferenceType (BaseType))
 923                                         return true;
 924
 925                                 if (targs != null) {
 926                                         foreach (var ta in targs) {
 927                                                 //
 928                                                 // Secondary special constraints are ignored (I am not sure why)
 929                                                 //
 930                                                 var tp = ta as TypeParameterSpec;
 931                                                 if (tp != null && (tp.spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
 932                                                         continue;
 933
 934                                                 if (TypeSpec.IsReferenceType (ta))
 935                                                         return true;
 936                                         }
 937                                 }
 938
 939                                 return false;
 940                         }
 941                 }
 942
 943                 //
 944                 // Returns whether the type parameter is known to be a value type
 945                 //
 946                 public new bool IsValueType {
 947                         get {
 948                                 //
 949                                 // Even if structs/enums cannot be used directly as constraints
 950                                 // they can apear as constraint type when inheriting base constraint
 951                                 // which has dependant type parameter constraint which has been
 952                                 // inflated using value type
 953                                 //
 954                                 // class A : B<int> { override void Foo<U> () {} }
 955                                 // class B<T> { virtual void Foo<U> () where U : T {} }
 956                                 //
 957                                 if (HasSpecialStruct)
 958                                         return true;
 959
 960                                 if (targs != null) {
 961                                         foreach (var ta in targs) {
 962                                                 if (TypeSpec.IsValueType (ta))
 963                                                         return true;
 964                                         }
 965                                 }
 966
 967                                 return false;
 968                         }
 969                 }
 970
 971                 public override string Name {
 972                         get {
 973                                 return definition.Name;
 974                         }
 975                 }
 976
 977                 public bool IsMethodOwned {
 978                         get {
 979                                 return DeclaringType == null;
 980                         }
 981                 }
 982
 983                 public SpecialConstraint SpecialConstraint {
 984                         get {
 985                                 return spec;
 986                         }
 987                         set {
 988                                 spec = value;
 989                         }
 990                 }
 991
 992                 //
 993                 // Types used to inflate the generic type
 994                 //
 995                 public new TypeSpec[] TypeArguments {
 996                         get {
 997                                 return targs;
 998                         }
 999                         set {
1000                                 targs = value;
1001                         }
1002                 }
1003
1004                 public Variance Variance {
1005                         get {
1006                                 return variance;
1007                         }
1008                 }
1009
1010                 #endregion
1011
1012                 public string DisplayDebugInfo ()
1013                 {
1014                         var s = GetSignatureForError ();
1015                         return IsMethodOwned ? s + "!!" : s + "!";
1016                 }
1017
1018                 //
1019                 // Finds effective base class. The effective base class is always a class-type
1020                 //
1021                 public TypeSpec GetEffectiveBase ()
1022                 {
1023                         if (HasSpecialStruct)
1024                                 return BaseType;
1025
1026                         //
1027                         // If T has a class-type constraint C but no type-parameter constraints, its effective base class is C
1028                         //
1029                         if (BaseType != null && targs == null) {
1030                                 //
1031                                 // If T has a constraint V that is a value-type, use instead the most specific base type of V that is a class-type.
1032                                 //
1033                                 // LAMESPEC: Is System.ValueType always the most specific base type in this case?
1034                                 //
1035                                 // Note: This can never happen in an explicitly given constraint, but may occur when the constraints of a generic method
1036                                 // are implicitly inherited by an overriding method declaration or an explicit implementation of an interface method.
1037                                 //
1038                                 return BaseType.IsStruct ? BaseType.BaseType : BaseType;
1039                         }
1040
1041                         if (effective_base != null)
1042                                 return effective_base;
1043
1044                         var types = new TypeSpec [HasTypeConstraint ? targs.Length + 1 : targs.Length];
1045
1046                         for (int i = 0; i < targs.Length; ++i) {
1047                                 var t = targs [i];
1048
1049                                 // Same issue as above, inherited constraints can be of struct type
1050                                 if (t.IsStruct) {
1051                                         types [i] = t.BaseType;
1052                                         continue;
1053                                 }
1054
1055                                 var tps = t as TypeParameterSpec;
1056                                 types [i] = tps != null ? tps.GetEffectiveBase () : t;
1057                         }
1058
1059                         if (HasTypeConstraint)
1060                                 types [types.Length - 1] = BaseType;
1061
1062                         return effective_base = Convert.FindMostEncompassedType (types);
1063                 }
1064
1065                 public override string GetSignatureForDocumentation (bool explicitName)
1066                 {
1067                         if (explicitName)
1068                                 return Name;
1069
1070                         var prefix = IsMethodOwned ? "``" : "`";
1071                         return prefix + DeclaredPosition;
1072                 }
1073
1074                 public override string GetSignatureForError ()
1075                 {
1076                         return Name;
1077                 }
1078
1079                 //
1080                 // Constraints have to match by definition but not position, used by
1081                 // partial classes or methods
1082                 //
1083                 public bool HasSameConstraintsDefinition (TypeParameterSpec other)
1084                 {
1085                         if (spec != other.spec)
1086                                 return false;
1087
1088                         if (BaseType != other.BaseType)
1089                                 return false;
1090
1091                         if (!TypeSpecComparer.Override.IsSame (InterfacesDefined, other.InterfacesDefined))
1092                                 return false;
1093
1094                         if (!TypeSpecComparer.Override.IsSame (targs, other.targs))
1095                                 return false;
1096
1097                         return true;
1098                 }
1099
1100                 //
1101                 // Constraints have to match by using same set of types, used by
1102                 // implicit interface implementation
1103                 //
1104                 public bool HasSameConstraintsImplementation (TypeParameterSpec other)
1105                 {
1106                         if (spec != other.spec)
1107                                 return false;
1108
1109                         //
1110                         // It can be same base type or inflated type parameter
1111                         //
1112                         // interface I<T> { void Foo<U> where U : T; }
1113                         // class A : I<int> { void Foo<X> where X : int {} }
1114                         //
1115                         bool found;
1116                         if (!TypeSpecComparer.Override.IsEqual (BaseType, other.BaseType)) {
1117                                 found = false;
1118                                 if (other.targs != null) {
1119                                         foreach (var otarg in other.targs) {
1120                                                 if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
1121                                                         found = true;
1122                                                         break;
1123                                                 }
1124                                         }
1125                                 } else if (targs != null) {
1126                                         foreach (var targ in targs) {
1127                                                 if (TypeSpecComparer.Override.IsEqual (targ, other.BaseType)) {
1128                                                         found = true;
1129                                                         break;
1130                                                 }
1131                                         }
1132                                 }
1133
1134                                 if (!found)
1135                                         return false;
1136                         }
1137
1138                         // Check interfaces implementation -> definition
1139                         if (InterfacesDefined != null) {
1140                                 //
1141                                 // Iterate over inflated interfaces
1142                                 //
1143                                 foreach (var iface in Interfaces) {
1144                                         found = false;
1145                                         if (other.InterfacesDefined != null) {
1146                                                 foreach (var oiface in other.Interfaces) {
1147                                                         if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
1148                                                                 found = true;
1149                                                                 break;
1150                                                         }
1151                                                 }
1152                                         }
1153
1154                                         if (found)
1155                                                 continue;
1156
1157                                         if (other.targs != null) {
1158                                                 foreach (var otarg in other.targs) {
1159                                                         if (TypeSpecComparer.Override.IsEqual (iface, otarg)) {
1160                                                                 found = true;
1161                                                                 break;
1162                                                         }
1163                                                 }
1164                                         }
1165
1166                                         if (!found)
1167                                                 return false;
1168                                 }
1169                         }
1170
1171                         // Check interfaces implementation <- definition
1172                         if (other.InterfacesDefined != null) {
1173                                 //
1174                                 // Iterate over inflated interfaces
1175                                 //
1176                                 foreach (var oiface in other.Interfaces) {
1177                                         found = false;
1178
1179                                         if (InterfacesDefined != null) {
1180                                                 foreach (var iface in Interfaces) {
1181                                                         if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
1182                                                                 found = true;
1183                                                                 break;
1184                                                         }
1185                                                 }
1186                                         } else if (targs != null) {
1187                                                 foreach (var targ in targs) {
1188                                                         if (TypeSpecComparer.Override.IsEqual (targ, oiface)) {
1189                                                                 found = true;
1190                                                                 break;
1191                                                         }
1192                                                 }
1193                                         }
1194
1195                                         if (!found)
1196                                                 return false;
1197                                 }
1198                         }
1199
1200                         // Check type parameters implementation -> definition
1201                         if (targs != null) {
1202                                 foreach (var targ in targs) {
1203                                         found = false;
1204
1205                                         if (other.targs != null) {
1206                                                 foreach (var otarg in other.targs) {
1207                                                         if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
1208                                                                 found = true;
1209                                                                 break;
1210                                                         }
1211                                                 }
1212                                         }
1213
1214                                         if (other.InterfacesDefined != null && !found) {
1215                                                 foreach (var iface in other.Interfaces) {
1216                                                         if (TypeSpecComparer.Override.IsEqual (iface, targ)) {
1217                                                                 found = true;
1218                                                                 break;
1219                                                         }
1220                                                 }
1221                                         }
1222
1223                                         if (!found)
1224                                                 found = TypeSpecComparer.Override.IsEqual (targ, other.BaseType);
1225
1226                                         if (!found)
1227                                                 return false;
1228                                 }
1229                         }
1230
1231                         // Check type parameters implementation <- definition
1232                         if (other.targs != null) {
1233                                 foreach (var otarg in other.targs) {
1234                                         // Ignore inflated type arguments, were checked above
1235                                         if (!otarg.IsGenericParameter)
1236                                                 continue;
1237
1238                                         if (targs == null)
1239                                                 return false;
1240
1241                                         found = false;
1242                                         foreach (var targ in targs) {
1243                                                 if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
1244                                                         found = true;
1245                                                         break;
1246                                                 }
1247                                         }
1248
1249                                         if (!found)
1250                                                 return false;
1251                                 }
1252                         }
1253
1254                         return true;
1255                 }
1256
1257                 public static TypeParameterSpec[] InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec[] tparams)
1258                 {
1259                         return InflateConstraints (tparams, l => l, inflator);
1260                 }
1261
1262                 public static TypeParameterSpec[] InflateConstraints<T> (TypeParameterSpec[] tparams, Func<T, TypeParameterInflator> inflatorFactory, T arg)
1263                 {
1264                         TypeParameterSpec[] constraints = null;
1265                         TypeParameterInflator? inflator = null;
1266
1267                         for (int i = 0; i < tparams.Length; ++i) {
1268                                 var tp = tparams[i];
1269                                 if (tp.HasTypeConstraint || tp.InterfacesDefined != null || tp.TypeArguments != null) {
1270                                         if (constraints == null) {
1271                                                 constraints = new TypeParameterSpec[tparams.Length];
1272                                                 Array.Copy (tparams, constraints, constraints.Length);
1273                                         }
1274
1275                                         //
1276                                         // Using a factory to avoid possibly expensive inflator build up
1277                                         //
1278                                         if (inflator == null)
1279                                                 inflator = inflatorFactory (arg);
1280
1281                                         constraints[i] = (TypeParameterSpec) constraints[i].InflateMember (inflator.Value);
1282                                 }
1283                         }
1284
1285                         if (constraints == null)
1286                                 constraints = tparams;
1287
1288                         return constraints;
1289                 }
1290
1291                 public void InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec tps)
1292                 {
1293                         tps.BaseType = inflator.Inflate (BaseType);
1294
1295                         var defined = InterfacesDefined;
1296                         if (defined != null) {
1297                                 tps.ifaces_defined = new TypeSpec[defined.Length];
1298                                 for (int i = 0; i < defined.Length; ++i)
1299                                         tps.ifaces_defined [i] = inflator.Inflate (defined[i]);
1300                         } else if (ifaces_defined == TypeSpec.EmptyTypes) {
1301                                 tps.ifaces_defined = TypeSpec.EmptyTypes;
1302                         }
1303
1304                         var ifaces = Interfaces;
1305                         if (ifaces != null) {
1306                                 tps.ifaces = new List<TypeSpec> (ifaces.Count);
1307                                 for (int i = 0; i < ifaces.Count; ++i)
1308                                         tps.ifaces.Add (inflator.Inflate (ifaces[i]));
1309                                 tps.state |= StateFlags.InterfacesExpanded;
1310                         }
1311
1312                         if (targs != null) {
1313                                 tps.targs = new TypeSpec[targs.Length];
1314                                 for (int i = 0; i < targs.Length; ++i)
1315                                         tps.targs[i] = inflator.Inflate (targs[i]);
1316                         }
1317                 }
1318
1319                 public override MemberSpec InflateMember (TypeParameterInflator inflator)
1320                 {
1321                         var tps = (TypeParameterSpec) MemberwiseClone ();
1322 #if DEBUG
1323                         tps.ID += 1000000;
1324 #endif
1325
1326                         InflateConstraints (inflator, tps);
1327                         return tps;
1328                 }
1329
1330                 //
1331                 // Populates type parameter members using type parameter constraints
1332                 // The trick here is to be called late enough but not too late to
1333                 // populate member cache with all members from other types
1334                 //
1335                 protected override void InitializeMemberCache (bool onlyTypes)
1336                 {
1337                         cache = new MemberCache ();
1338
1339                         //
1340                         // For a type parameter the membercache is the union of the sets of members of the types
1341                         // specified as a primary constraint or secondary constraint
1342                         //
1343                         if (BaseType.BuiltinType != BuiltinTypeSpec.Type.Object && BaseType.BuiltinType != BuiltinTypeSpec.Type.ValueType)
1344                                 cache.AddBaseType (BaseType);
1345
1346                         if (InterfacesDefined != null) {
1347                                 foreach (var iface_type in InterfacesDefined) {
1348                                         cache.AddInterface (iface_type);
1349                                 }
1350                         }
1351
1352                         if (targs != null) {
1353                                 foreach (var ta in targs) {
1354                                         var tps = ta as TypeParameterSpec;
1355                                         IList<TypeSpec> ifaces;
1356                                         TypeSpec b_type;
1357                                         if (tps != null) {
1358                                                 b_type = tps.GetEffectiveBase ();
1359                                                 ifaces = tps.InterfacesDefined;
1360                                         } else {
1361                                                 b_type = ta;
1362                                                 ifaces = ta.Interfaces;
1363                                         }
1364
1365                                         //
1366                                         // Don't add base type which was inflated from base constraints but it's not valid
1367                                         // in C# context
1368                                         //
1369                                         if (b_type != null && b_type.BuiltinType != BuiltinTypeSpec.Type.Object && b_type.BuiltinType != BuiltinTypeSpec.Type.ValueType && !b_type.IsStructOrEnum)
1370                                                 cache.AddBaseType (b_type);
1371
1372                                         if (ifaces != null) {
1373                                                 foreach (var iface_type in ifaces) {
1374                                                         cache.AddInterface (iface_type);
1375                                                 }
1376                                         }
1377                                 }
1378                         }
1379                 }
1380
1381                 public bool IsConvertibleToInterface (TypeSpec iface)
1382                 {
1383                         if (Interfaces != null) {
1384                                 foreach (var t in Interfaces) {
1385                                         if (t == iface)
1386                                                 return true;
1387                                 }
1388                         }
1389
1390                         if (TypeArguments != null) {
1391                                 foreach (var t in TypeArguments) {
1392                                         var tps = t as TypeParameterSpec;
1393                                         if (tps != null) {
1394                                                 if (tps.IsConvertibleToInterface (iface))
1395                                                         return true;
1396
1397                                                 continue;
1398                                         }
1399
1400                                         if (t.ImplementsInterface (iface, false))
1401                                                 return true;
1402                                 }
1403                         }
1404
1405                         return false;
1406                 }
1407
1408                 public static bool HasAnyTypeParameterTypeConstrained (IGenericMethodDefinition md)
1409                 {
1410                         var tps = md.TypeParameters;
1411                         for (int i = 0; i < md.TypeParametersCount; ++i) {
1412                                 if (tps[i].HasAnyTypeConstraint) {
1413                                         return true;
1414                                 }
1415                         }
1416
1417                         return false;
1418                 }
1419
1420                 public static bool HasAnyTypeParameterConstrained (IGenericMethodDefinition md)
1421                 {
1422                         var tps = md.TypeParameters;
1423                         for (int i = 0; i < md.TypeParametersCount; ++i) {
1424                                 if (tps[i].IsConstrained) {
1425                                         return true;
1426                                 }
1427                         }
1428
1429                         return false;
1430                 }
1431
1432                 public bool HasDependencyOn (TypeSpec type)
1433                 {
1434                         if (TypeArguments != null) {
1435                                 foreach (var targ in TypeArguments) {
1436                                         if (TypeSpecComparer.Override.IsEqual (targ, type))
1437                                                 return true;
1438
1439                                         var tps = targ as TypeParameterSpec;
1440                                         if (tps != null && tps.HasDependencyOn (type))
1441                                                 return true;
1442                                 }
1443                         }
1444
1445                         return false;
1446                 }
1447
1448                 public override TypeSpec Mutate (TypeParameterMutator mutator)
1449                 {
1450                         return mutator.Mutate (this);
1451                 }
1452         }
1453
1454         public struct TypeParameterInflator
1455         {
1456                 readonly TypeSpec type;
1457                 readonly TypeParameterSpec[] tparams;
1458                 readonly TypeSpec[] targs;
1459                 readonly IModuleContext context;
1460
1461                 public TypeParameterInflator (TypeParameterInflator nested, TypeSpec type)
1462                         : this (nested.context, type, nested.tparams, nested.targs)
1463                 {
1464                 }
1465
1466                 public TypeParameterInflator (IModuleContext context, TypeSpec type, TypeParameterSpec[] tparams, TypeSpec[] targs)
1467                 {
1468                         if (tparams.Length != targs.Length)
1469                                 throw new ArgumentException ("Invalid arguments");
1470
1471                         this.context = context;
1472                         this.tparams = tparams;
1473                         this.targs = targs;
1474                         this.type = type;
1475                 }
1476
1477                 #region Properties
1478
1479                 public IModuleContext Context {
1480                         get {
1481                                 return context;
1482                         }
1483                 }
1484
1485                 public TypeSpec TypeInstance {
1486                         get {
1487                                 return type;
1488                         }
1489                 }
1490
1491                 //
1492                 // Type parameters to inflate
1493                 //
1494                 public TypeParameterSpec[] TypeParameters {
1495                         get {
1496                                 return tparams;
1497                         }
1498                 }
1499
1500                 #endregion
1501
1502                 public TypeSpec Inflate (TypeSpec type)
1503                 {
1504                         var tp = type as TypeParameterSpec;
1505                         if (tp != null)
1506                                 return Inflate (tp);
1507
1508                         var ec = type as ElementTypeSpec;
1509                         if (ec != null) {
1510                                 var et = Inflate (ec.Element);
1511                                 if (et != ec.Element) {
1512                                         var ac = ec as ArrayContainer;
1513                                         if (ac != null)
1514                                                 return ArrayContainer.MakeType (context.Module, et, ac.Rank);
1515
1516                                         if (ec is PointerContainer)
1517                                                 return PointerContainer.MakeType (context.Module, et);
1518
1519                                         throw new NotImplementedException ();
1520                                 }
1521
1522                                 return ec;
1523                         }
1524
1525                         if (type.Kind == MemberKind.MissingType)
1526                                 return type;
1527
1528                         //
1529                         // When inflating a nested type, inflate its parent first
1530                         // in case it's using same type parameters (was inflated within the type)
1531                         //
1532                         TypeSpec[] targs;
1533                         int i = 0;
1534                         if (type.IsNested) {
1535                                 var parent = Inflate (type.DeclaringType);
1536
1537                                 //
1538                                 // Keep the inflated type arguments
1539                                 //
1540                                 targs = type.TypeArguments;
1541
1542                                 //
1543                                 // When inflating imported nested type used inside same declaring type, we get TypeSpec
1544                                 // because the import cache helps us to catch it. However, that means we have to look at
1545                                 // type definition to get type argument (they are in fact type parameter in this case)
1546                                 //
1547                                 if (targs.Length == 0 && type.Arity > 0)
1548                                         targs = type.MemberDefinition.TypeParameters;
1549
1550                                 //
1551                                 // Parent was inflated, find the same type on inflated type
1552                                 // to use same cache for nested types on same generic parent
1553                                 //
1554                                 type = MemberCache.FindNestedType (parent, type.Name, type.Arity);
1555
1556                                 //
1557                                 // Handle the tricky case where parent shares local type arguments
1558                                 // which means inflating inflated type
1559                                 //
1560                                 // class Test<T> {
1561                                 //              public static Nested<T> Foo () { return null; }
1562                                 //
1563                                 //              public class Nested<U> {}
1564                                 //      }
1565                                 //
1566                                 //  return type of Test<string>.Foo() has to be Test<string>.Nested<string>
1567                                 //
1568                                 if (targs.Length > 0) {
1569                                         var inflated_targs = new TypeSpec[targs.Length];
1570                                         for (; i < targs.Length; ++i)
1571                                                 inflated_targs[i] = Inflate (targs[i]);
1572
1573                                         type = type.MakeGenericType (context, inflated_targs);
1574                                 }
1575
1576                                 return type;
1577                         }
1578
1579                         // Nothing to do for non-generic type
1580                         if (type.Arity == 0)
1581                                 return type;
1582
1583                         targs = new TypeSpec[type.Arity];
1584
1585                         //
1586                         // Inflating using outside type arguments, var v = new Foo<int> (), class Foo<T> {}
1587                         //
1588                         if (type is InflatedTypeSpec) {
1589                                 for (; i < targs.Length; ++i)
1590                                         targs[i] = Inflate (type.TypeArguments[i]);
1591
1592                                 type = type.GetDefinition ();
1593                         } else {
1594                                 //
1595                                 // Inflating parent using inside type arguments, class Foo<T> { ITest<T> foo; }
1596                                 //
1597                                 var args = type.MemberDefinition.TypeParameters;
1598                                 foreach (var ds_tp in args)
1599                                         targs[i++] = Inflate (ds_tp);
1600                         }
1601
1602                         return type.MakeGenericType (context, targs);
1603                 }
1604
1605                 public TypeSpec Inflate (TypeParameterSpec tp)
1606                 {
1607                         for (int i = 0; i < tparams.Length; ++i)
1608                                 if (tparams [i] == tp)
1609                                         return targs[i];
1610
1611                         // This can happen when inflating nested types
1612                         // without type arguments specified
1613                         return tp;
1614                 }
1615         }
1616
1617         //
1618         // Before emitting any code we have to change all MVAR references to VAR
1619         // when the method is of generic type and has hoisted variables
1620         //
1621         public class TypeParameterMutator
1622         {
1623                 readonly TypeParameters mvar;
1624                 readonly TypeParameters var;
1625                 readonly TypeParameterSpec[] src;
1626                 Dictionary<TypeSpec, TypeSpec> mutated_typespec;
1627
1628                 public TypeParameterMutator (TypeParameters mvar, TypeParameters var)
1629                 {
1630                         if (mvar.Count != var.Count)
1631                                 throw new ArgumentException ();
1632
1633                         this.mvar = mvar;
1634                         this.var = var;
1635                 }
1636
1637                 public TypeParameterMutator (TypeParameterSpec[] srcVar, TypeParameters destVar)
1638                 {
1639                         if (srcVar.Length != destVar.Count)
1640                                 throw new ArgumentException ();
1641
1642                         this.src = srcVar;
1643                         this.var = destVar;
1644                 }
1645
1646                 #region Properties
1647
1648                 public TypeParameters MethodTypeParameters {
1649                         get {
1650                                 return mvar;
1651                         }
1652                 }
1653
1654                 #endregion
1655
1656                 public static TypeSpec GetMemberDeclaringType (TypeSpec type)
1657                 {
1658                         if (type is InflatedTypeSpec) {
1659                                 if (type.DeclaringType == null)
1660                                         return type.GetDefinition ();
1661
1662                                 var parent = GetMemberDeclaringType (type.DeclaringType);
1663                                 type = MemberCache.GetMember<TypeSpec> (parent, type);
1664                         }
1665
1666                         return type;
1667                 }
1668
1669                 public TypeSpec Mutate (TypeSpec ts)
1670                 {
1671                         TypeSpec value;
1672                         if (mutated_typespec != null && mutated_typespec.TryGetValue (ts, out value))
1673                                 return value;
1674
1675                         value = ts.Mutate (this);
1676                         if (mutated_typespec == null)
1677                                 mutated_typespec = new Dictionary<TypeSpec, TypeSpec> ();
1678
1679                         mutated_typespec.Add (ts, value);
1680                         return value;
1681                 }
1682
1683                 public TypeParameterSpec Mutate (TypeParameterSpec tp)
1684                 {
1685                         if (mvar != null) {
1686                                 for (int i = 0; i < mvar.Count; ++i) {
1687                                         if (mvar[i].Type == tp)
1688                                                 return var[i].Type;
1689                                 }
1690                         } else {
1691                                 for (int i = 0; i < src.Length; ++i) {
1692                                         if (src[i] == tp)
1693                                                 return var[i].Type;
1694                                 }
1695                         }
1696
1697                         return tp;
1698                 }
1699
1700                 public TypeSpec[] Mutate (TypeSpec[] targs)
1701                 {
1702                         TypeSpec[] mutated = new TypeSpec[targs.Length];
1703                         bool changed = false;
1704                         for (int i = 0; i < targs.Length; ++i) {
1705                                 mutated[i] = Mutate (targs[i]);
1706                                 changed |= targs[i] != mutated[i];
1707                         }
1708
1709                         return changed ? mutated : targs;
1710                 }
1711         }
1712
1713         /// <summary>
1714         ///   A TypeExpr which already resolved to a type parameter.
1715         /// </summary>
1716         public class TypeParameterExpr : TypeExpression
1717         {
1718                 public TypeParameterExpr (TypeParameter type_parameter, Location loc)
1719                         : base (type_parameter.Type, loc)
1720                 {
1721                         this.eclass = ExprClass.TypeParameter;
1722                 }
1723         }
1724
1725         public class InflatedTypeSpec : TypeSpec
1726         {
1727                 TypeSpec[] targs;
1728                 TypeParameterSpec[] constraints;
1729                 readonly TypeSpec open_type;
1730                 readonly IModuleContext context;
1731
1732                 public InflatedTypeSpec (IModuleContext context, TypeSpec openType, TypeSpec declaringType, TypeSpec[] targs)
1733                         : base (openType.Kind, declaringType, openType.MemberDefinition, null, openType.Modifiers)
1734                 {
1735                         if (targs == null)
1736                                 throw new ArgumentNullException ("targs");
1737
1738                         this.state &= ~SharedStateFlags;
1739                         this.state |= (openType.state & SharedStateFlags);
1740
1741                         this.context = context;
1742                         this.open_type = openType;
1743                         this.targs = targs;
1744
1745                         foreach (var arg in targs) {
1746                                 if (arg.HasDynamicElement || arg.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
1747                                         state |= StateFlags.HasDynamicElement;
1748                                         break;
1749                                 }
1750                         }
1751
1752                         if (open_type.Kind == MemberKind.MissingType)
1753                                 MemberCache = MemberCache.Empty;
1754
1755                         if ((open_type.Modifiers & Modifiers.COMPILER_GENERATED) != 0)
1756                                 state |= StateFlags.ConstraintsChecked;
1757                 }
1758
1759                 #region Properties
1760
1761                 public override TypeSpec BaseType {
1762                         get {
1763                                 if (cache == null || (state & StateFlags.PendingBaseTypeInflate) != 0)
1764                                         InitializeMemberCache (true);
1765
1766                                 return base.BaseType;
1767                         }
1768                 }
1769
1770                 //
1771                 // Inflated type parameters with constraints array, mapping with type arguments is based on index
1772                 //
1773                 public TypeParameterSpec[] Constraints {
1774                         get {
1775                                 if (constraints == null) {
1776                                         constraints = TypeParameterSpec.InflateConstraints (MemberDefinition.TypeParameters, l => l.CreateLocalInflator (context), this);
1777                                 }
1778
1779                                 return constraints;
1780                         }
1781                 }
1782
1783                 //
1784                 // Used to cache expensive constraints validation on constructed types
1785                 //
1786                 public bool HasConstraintsChecked {
1787                         get {
1788                                 return (state & StateFlags.ConstraintsChecked) != 0;
1789                         }
1790                         set {
1791                                 state = value ? state | StateFlags.ConstraintsChecked : state & ~StateFlags.ConstraintsChecked;
1792                         }
1793                 }
1794
1795                 public override IList<TypeSpec> Interfaces {
1796                         get {
1797                                 if (cache == null)
1798                                         InitializeMemberCache (true);
1799
1800                                 return base.Interfaces;
1801                         }
1802                 }
1803
1804                 public override bool IsExpressionTreeType {
1805                         get {
1806                                 return (open_type.state & StateFlags.InflatedExpressionType) != 0;
1807                         }
1808                 }
1809
1810                 public override bool IsArrayGenericInterface {
1811                         get {
1812                                 return (open_type.state & StateFlags.GenericIterateInterface) != 0;
1813                         }
1814                 }
1815
1816                 public override bool IsGenericTask {
1817                         get {
1818                                 return (open_type.state & StateFlags.GenericTask) != 0;
1819                         }
1820                 }
1821
1822                 public override bool IsNullableType {
1823                         get {
1824                                 return (open_type.state & StateFlags.InflatedNullableType) != 0;
1825                         }
1826                 }
1827
1828                 //
1829                 // Types used to inflate the generic  type
1830                 //
1831                 public override TypeSpec[] TypeArguments {
1832                         get {
1833                                 return targs;
1834                         }
1835                 }
1836
1837                 #endregion
1838
1839                 public override bool AddInterface (TypeSpec iface)
1840                 {
1841                         var inflator = CreateLocalInflator (context);
1842                         iface = inflator.Inflate (iface);
1843                         if (iface == null)
1844                                 return false;
1845
1846                         return base.AddInterface (iface);
1847                 }
1848
1849                 public static bool ContainsTypeParameter (TypeSpec type)
1850                 {
1851                         if (type.Kind == MemberKind.TypeParameter)
1852                                 return true;
1853
1854                         var element_container = type as ElementTypeSpec;
1855                         if (element_container != null)
1856                                 return ContainsTypeParameter (element_container.Element);
1857
1858                         foreach (var t in type.TypeArguments) {
1859                                 if (ContainsTypeParameter (t)) {
1860                                         return true;
1861                                 }
1862                         }
1863
1864                         return false;
1865                 }
1866
1867                 public TypeParameterInflator CreateLocalInflator (IModuleContext context)
1868                 {
1869                         TypeParameterSpec[] tparams_full;
1870                         TypeSpec[] targs_full = targs;
1871                         if (IsNested) {
1872                                 //
1873                                 // Special case is needed when we are inflating an open type (nested type definition)
1874                                 // on inflated parent. Consider following case
1875                                 //
1876                                 // Foo<T>.Bar<U> => Foo<string>.Bar<U>
1877                                 //
1878                                 // Any later inflation of Foo<string>.Bar<U> has to also inflate T if used inside Bar<U>
1879                                 //
1880                                 List<TypeSpec> merged_targs = null;
1881                                 List<TypeParameterSpec> merged_tparams = null;
1882
1883                                 var type = DeclaringType;
1884
1885                                 do {
1886                                         if (type.TypeArguments.Length > 0) {
1887                                                 if (merged_targs == null) {
1888                                                         merged_targs = new List<TypeSpec> ();
1889                                                         merged_tparams = new List<TypeParameterSpec> ();
1890                                                         if (targs.Length > 0) {
1891                                                                 merged_targs.AddRange (targs);
1892                                                                 merged_tparams.AddRange (open_type.MemberDefinition.TypeParameters);
1893                                                         }
1894                                                 }
1895                                                 merged_tparams.AddRange (type.MemberDefinition.TypeParameters);
1896                                                 merged_targs.AddRange (type.TypeArguments);
1897                                         }
1898                                         type = type.DeclaringType;
1899                                 } while (type != null);
1900
1901                                 if (merged_targs != null) {
1902                                         // Type arguments are not in the right order but it should not matter in this case
1903                                         targs_full = merged_targs.ToArray ();
1904                                         tparams_full = merged_tparams.ToArray ();
1905                                 } else if (targs.Length == 0) {
1906                                         tparams_full = TypeParameterSpec.EmptyTypes;
1907                                 } else {
1908                                         tparams_full = open_type.MemberDefinition.TypeParameters;
1909                                 }
1910                         } else if (targs.Length == 0) {
1911                                 tparams_full = TypeParameterSpec.EmptyTypes;
1912                         } else {
1913                                 tparams_full = open_type.MemberDefinition.TypeParameters;
1914                         }
1915
1916                         return new TypeParameterInflator (context, this, tparams_full, targs_full);
1917                 }
1918
1919                 MetaType CreateMetaInfo ()
1920                 {
1921                         //
1922                         // Converts nested type arguments into right order
1923                         // Foo<string, bool>.Bar<int> => string, bool, int
1924                         //
1925                         var all = new List<MetaType> ();
1926                         TypeSpec type = this;
1927                         TypeSpec definition = type;
1928                         do {
1929                                 if (type.GetDefinition().IsGeneric) {
1930                                         all.InsertRange (0,
1931                                                 type.TypeArguments != TypeSpec.EmptyTypes ?
1932                                                 type.TypeArguments.Select (l => l.GetMetaInfo ()) :
1933                                                 type.MemberDefinition.TypeParameters.Select (l => l.GetMetaInfo ()));
1934                                 }
1935
1936                                 definition = definition.GetDefinition ();
1937                                 type = type.DeclaringType;
1938                         } while (type != null);
1939
1940                         return definition.GetMetaInfo ().MakeGenericType (all.ToArray ());
1941                 }
1942
1943                 public override ObsoleteAttribute GetAttributeObsolete ()
1944                 {
1945                         return open_type.GetAttributeObsolete ();
1946                 }
1947
1948                 protected override bool IsNotCLSCompliant (out bool attrValue)
1949                 {
1950                         if (base.IsNotCLSCompliant (out attrValue))
1951                                 return true;
1952
1953                         foreach (var ta in TypeArguments) {
1954                                 if (ta.MemberDefinition.CLSAttributeValue == false)
1955                                         return true;
1956                         }
1957
1958                         return false;
1959                 }
1960
1961                 public override TypeSpec GetDefinition ()
1962                 {
1963                         return open_type;
1964                 }
1965
1966                 public override MetaType GetMetaInfo ()
1967                 {
1968                         if (info == null)
1969                                 info = CreateMetaInfo ();
1970
1971                         return info;
1972                 }
1973
1974                 public override string GetSignatureForError ()
1975                 {
1976                         if (IsNullableType)
1977                                 return targs[0].GetSignatureForError () + "?";
1978
1979                         return base.GetSignatureForError ();
1980                 }
1981
1982                 protected override string GetTypeNameSignature ()
1983                 {
1984                         if (targs.Length == 0 || MemberDefinition is AnonymousTypeClass)
1985                                 return null;
1986
1987                         return "<" + TypeManager.CSharpName (targs) + ">";
1988                 }
1989
1990                 public bool HasDynamicArgument ()
1991                 {
1992                         for (int i = 0; i < targs.Length; ++i) {
1993                                 var item = targs[i];
1994
1995                                 if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
1996                                         return true;
1997
1998                                 if (item is InflatedTypeSpec) {
1999                                         if (((InflatedTypeSpec) item).HasDynamicArgument ())
2000                                                 return true;
2001
2002                                         continue;
2003                                 }
2004
2005                                 if (item.IsArray) {
2006                                         while (item.IsArray) {
2007                                                 item = ((ArrayContainer) item).Element;
2008                                         }
2009
2010                                         if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2011                                                 return true;
2012                                 }
2013                         }
2014
2015                         return false;
2016                 }
2017
2018                 protected override void InitializeMemberCache (bool onlyTypes)
2019                 {
2020                         if (cache == null) {
2021                                 var open_cache = onlyTypes ? open_type.MemberCacheTypes : open_type.MemberCache;
2022
2023                                 // Surprisingly, calling MemberCache on open type could meantime create cache on this type
2024                                 // for imported type parameter constraints referencing nested type of this declaration
2025                                 if (cache == null)
2026                                         cache = new MemberCache (open_cache);
2027                         }
2028
2029                         var inflator = CreateLocalInflator (context);
2030
2031                         //
2032                         // Two stage inflate due to possible nested types recursive
2033                         // references
2034                         //
2035                         // class A<T> {
2036                         //    B b;
2037                         //    class B {
2038                         //      T Value;
2039                         //    }
2040                         // }
2041                         //
2042                         // When resolving type of `b' members of `B' cannot be
2043                         // inflated because are not yet available in membercache
2044                         //
2045                         if ((state & StateFlags.PendingMemberCacheMembers) == 0) {
2046                                 open_type.MemberCacheTypes.InflateTypes (cache, inflator);
2047
2048                                 //
2049                                 // Inflate any implemented interfaces
2050                                 //
2051                                 if (open_type.Interfaces != null) {
2052                                         ifaces = new List<TypeSpec> (open_type.Interfaces.Count);
2053                                         foreach (var iface in open_type.Interfaces) {
2054                                                 var iface_inflated = inflator.Inflate (iface);
2055                                                 if (iface_inflated == null)
2056                                                         continue;
2057
2058                                                 base.AddInterface (iface_inflated);
2059                                         }
2060                                 }
2061
2062                                 //
2063                                 // Handles the tricky case of recursive nested base generic type
2064                                 //
2065                                 // class A<T> : Base<A<T>.Nested> {
2066                                 //    class Nested {}
2067                                 // }
2068                                 //
2069                                 // When inflating A<T>. base type is not yet known, secondary
2070                                 // inflation is required (not common case) once base scope
2071                                 // is known
2072                                 //
2073                                 if (open_type.BaseType == null) {
2074                                         if (IsClass)
2075                                                 state |= StateFlags.PendingBaseTypeInflate;
2076                                 } else {
2077                                         BaseType = inflator.Inflate (open_type.BaseType);
2078                                 }
2079                         } else if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2080                                 //
2081                                 // It can happen when resolving base type without being defined
2082                                 // which is not allowed to happen and will always lead to an error
2083                                 //
2084                                 // class B { class N {} }
2085                                 // class A<T> : A<B.N> {}
2086                                 //
2087                                 if (open_type.BaseType == null)
2088                                         return;
2089
2090                                 BaseType = inflator.Inflate (open_type.BaseType);
2091                                 state &= ~StateFlags.PendingBaseTypeInflate;
2092                         }
2093
2094                         if (onlyTypes) {
2095                                 state |= StateFlags.PendingMemberCacheMembers;
2096                                 return;
2097                         }
2098
2099                         var tc = open_type.MemberDefinition as TypeDefinition;
2100                         if (tc != null && !tc.HasMembersDefined) {
2101                                 //
2102                                 // Inflating MemberCache with undefined members
2103                                 //
2104                                 return;
2105                         }
2106
2107                         if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2108                                 BaseType = inflator.Inflate (open_type.BaseType);
2109                                 state &= ~StateFlags.PendingBaseTypeInflate;
2110                         }
2111
2112                         state &= ~StateFlags.PendingMemberCacheMembers;
2113                         open_type.MemberCache.InflateMembers (cache, open_type, inflator);
2114                 }
2115
2116                 public override TypeSpec Mutate (TypeParameterMutator mutator)
2117                 {
2118                         var targs = TypeArguments;
2119                         if (targs != null)
2120                                 targs = mutator.Mutate (targs);
2121
2122                         var decl = DeclaringType;
2123                         if (IsNested && DeclaringType.IsGenericOrParentIsGeneric)
2124                                 decl = mutator.Mutate (decl);
2125
2126                         if (targs == TypeArguments && decl == DeclaringType)
2127                                 return this;
2128
2129                         var mutated = (InflatedTypeSpec) MemberwiseClone ();
2130                         if (decl != DeclaringType) {
2131                                 // Gets back MethodInfo in case of metaInfo was inflated
2132                                 //mutated.info = MemberCache.GetMember<TypeSpec> (DeclaringType.GetDefinition (), this).info;
2133
2134                                 mutated.declaringType = decl;
2135                                 mutated.state |= StateFlags.PendingMetaInflate;
2136                         }
2137
2138                         if (targs != null) {
2139                                 mutated.targs = targs;
2140                                 mutated.info = null;
2141                         }
2142
2143                         return mutated;
2144                 }
2145         }
2146
2147
2148         //
2149         // Tracks the type arguments when instantiating a generic type. It's used
2150         // by both type arguments and type parameters
2151         //
2152         public class TypeArguments
2153         {
2154                 List<FullNamedExpression> args;
2155                 TypeSpec[] atypes;
2156
2157                 public TypeArguments (params FullNamedExpression[] types)
2158                 {
2159                         this.args = new List<FullNamedExpression> (types);
2160                 }
2161
2162                 public void Add (FullNamedExpression type)
2163                 {
2164                         args.Add (type);
2165                 }
2166
2167                 /// <summary>
2168                 ///   We may only be used after Resolve() is called and return the fully
2169                 ///   resolved types.
2170                 /// </summary>
2171                 // TODO: Not needed, just return type from resolve
2172                 public TypeSpec[] Arguments {
2173                         get {
2174                                 return atypes;
2175                         }
2176                         set {
2177                                 atypes = value;
2178                         }
2179                 }
2180
2181                 public int Count {
2182                         get {
2183                                 return args.Count;
2184                         }
2185                 }
2186
2187                 public virtual bool IsEmpty {
2188                         get {
2189                                 return false;
2190                         }
2191                 }
2192
2193                 public List<FullNamedExpression> TypeExpressions {
2194                         get {
2195                                 return this.args;
2196                         }
2197                 }
2198
2199                 public string GetSignatureForError()
2200                 {
2201                         StringBuilder sb = new StringBuilder ();
2202                         for (int i = 0; i < Count; ++i) {
2203                                 var expr = args[i];
2204                                 if (expr != null)
2205                                         sb.Append (expr.GetSignatureForError ());
2206
2207                                 if (i + 1 < Count)
2208                                         sb.Append (',');
2209                         }
2210
2211                         return sb.ToString ();
2212                 }
2213
2214                 /// <summary>
2215                 ///   Resolve the type arguments.
2216                 /// </summary>
2217                 public virtual bool Resolve (IMemberContext ec, bool allowUnbound)
2218                 {
2219                         if (atypes != null)
2220                             return true;
2221
2222                         int count = args.Count;
2223                         bool ok = true;
2224
2225                         atypes = new TypeSpec [count];
2226
2227                         var errors = ec.Module.Compiler.Report.Errors;
2228
2229                         for (int i = 0; i < count; i++){
2230                                 var te = args[i].ResolveAsType (ec);
2231                                 if (te == null) {
2232                                         ok = false;
2233                                         continue;
2234                                 }
2235
2236                                 atypes[i] = te;
2237
2238                                 if (te.IsStatic) {
2239                                         ec.Module.Compiler.Report.Error (718, args[i].Location, "`{0}': static classes cannot be used as generic arguments",
2240                                                 te.GetSignatureForError ());
2241                                         ok = false;
2242                                 }
2243
2244                                 if (te.IsPointer || te.IsSpecialRuntimeType) {
2245                                         ec.Module.Compiler.Report.Error (306, args[i].Location,
2246                                                 "The type `{0}' may not be used as a type argument",
2247                                                 te.GetSignatureForError ());
2248                                         ok = false;
2249                                 }
2250                         }
2251
2252                         if (!ok || errors != ec.Module.Compiler.Report.Errors)
2253                                 atypes = null;
2254
2255                         return ok;
2256                 }
2257
2258                 public TypeArguments Clone ()
2259                 {
2260                         TypeArguments copy = new TypeArguments ();
2261                         foreach (var ta in args)
2262                                 copy.args.Add (ta);
2263
2264                         return copy;
2265                 }
2266         }
2267
2268         public class UnboundTypeArguments : TypeArguments
2269         {
2270                 Location loc;
2271
2272                 public UnboundTypeArguments (int arity, Location loc)
2273                         : base (new FullNamedExpression[arity])
2274                 {
2275                         this.loc = loc;
2276                 }
2277
2278                 public override bool IsEmpty {
2279                         get {
2280                                 return true;
2281                         }
2282                 }
2283
2284                 public override bool Resolve (IMemberContext mc, bool allowUnbound)
2285                 {
2286                         if (!allowUnbound) {
2287                                 mc.Module.Compiler.Report.Error (7003, loc, "Unbound generic name is not valid in this context");
2288                         }
2289
2290                         // Nothing to be resolved
2291                         return true;
2292                 }
2293         }
2294
2295         public class TypeParameters
2296         {
2297                 List<TypeParameter> names;
2298                 TypeParameterSpec[] types;
2299
2300                 public TypeParameters ()
2301                 {
2302                         names = new List<TypeParameter> ();
2303                 }
2304
2305                 public TypeParameters (int count)
2306                 {
2307                         names = new List<TypeParameter> (count);
2308                 }
2309
2310                 #region Properties
2311
2312                 public int Count {
2313                         get {
2314                                 return names.Count;
2315                         }
2316                 }
2317
2318                 public TypeParameterSpec[] Types {
2319                         get {
2320                                 return types;
2321                         }
2322                 }
2323
2324                 #endregion
2325
2326                 public void Add (TypeParameter tparam)
2327                 {
2328                         names.Add (tparam);
2329                 }
2330
2331                 public void Add (TypeParameters tparams)
2332                 {
2333                         names.AddRange (tparams.names);
2334                 }
2335
2336                 public void Create (TypeSpec declaringType, int parentOffset, TypeContainer parent)
2337                 {
2338                         types = new TypeParameterSpec[Count];
2339                         for (int i = 0; i < types.Length; ++i) {
2340                                 var tp = names[i];
2341
2342                                 tp.Create (declaringType, parent);
2343                                 types[i] = tp.Type;
2344                                 types[i].DeclaredPosition = i + parentOffset;
2345
2346                                 if (tp.Variance != Variance.None && !(declaringType != null && (declaringType.Kind == MemberKind.Interface || declaringType.Kind == MemberKind.Delegate))) {
2347                                         parent.Compiler.Report.Error (1960, tp.Location, "Variant type parameters can only be used with interfaces and delegates");
2348                                 }
2349                         }
2350                 }
2351
2352                 public void Define (GenericTypeParameterBuilder[] builders)
2353                 {
2354                         for (int i = 0; i < types.Length; ++i) {
2355                                 var tp = names[i];
2356                                 tp.Define (builders [types [i].DeclaredPosition]);
2357                         }
2358                 }
2359
2360                 public TypeParameter this[int index] {
2361                         get {
2362                                 return names [index];
2363                         }
2364                         set {
2365                                 names[index] = value;
2366                         }
2367                 }
2368
2369                 public TypeParameter Find (string name)
2370                 {
2371                         foreach (var tp in names) {
2372                                 if (tp.Name == name)
2373                                         return tp;
2374                         }
2375
2376                         return null;
2377                 }
2378
2379                 public string[] GetAllNames ()
2380                 {
2381                         return names.Select (l => l.Name).ToArray ();
2382                 }
2383
2384                 public string GetSignatureForError ()
2385                 {
2386                         StringBuilder sb = new StringBuilder ();
2387                         for (int i = 0; i < Count; ++i) {
2388                                 if (i > 0)
2389                                         sb.Append (',');
2390
2391                                 var name = names[i];
2392                                 if (name != null)
2393                                         sb.Append (name.GetSignatureForError ());
2394                         }
2395
2396                         return sb.ToString ();
2397                 }
2398
2399
2400                 public void CheckPartialConstraints (Method part)
2401                 {
2402                         var partTypeParameters = part.CurrentTypeParameters;
2403
2404                         for (int i = 0; i < Count; i++) {
2405                                 var tp_a = names[i];
2406                                 var tp_b = partTypeParameters [i];
2407                                 if (tp_a.Constraints == null) {
2408                                         if (tp_b.Constraints == null)
2409                                                 continue;
2410                                 } else if (tp_b.Constraints != null && tp_a.Type.HasSameConstraintsDefinition (tp_b.Type)) {
2411                                         continue;
2412                                 }
2413
2414                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition.Location, "");
2415                                 part.Compiler.Report.Error (761, part.Location,
2416                                         "Partial method declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2417                                         part.GetSignatureForError (), partTypeParameters[i].GetSignatureForError ());
2418                         }
2419                 }
2420
2421                 public void UpdateConstraints (TypeDefinition part)
2422                 {
2423                         var partTypeParameters = part.MemberName.TypeParameters;
2424
2425                         for (int i = 0; i < Count; i++) {
2426                                 var tp = names [i];
2427                                 if (tp.AddPartialConstraints (part, partTypeParameters [i]))
2428                                         continue;
2429
2430                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition);
2431                                 part.Compiler.Report.Error (265, part.Location,
2432                                         "Partial declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2433                                         part.GetSignatureForError (), tp.GetSignatureForError ());
2434                         }
2435                 }
2436
2437                 public void VerifyClsCompliance ()
2438                 {
2439                         foreach (var tp in names) {
2440                                 tp.VerifyClsCompliance ();
2441                         }
2442                 }
2443         }
2444
2445         //
2446         // A type expression of generic type with type arguments
2447         //
2448         class GenericTypeExpr : TypeExpr
2449         {
2450                 TypeArguments args;
2451                 TypeSpec open_type;
2452
2453                 /// <summary>
2454                 ///   Instantiate the generic type `t' with the type arguments `args'.
2455                 ///   Use this constructor if you already know the fully resolved
2456                 ///   generic type.
2457                 /// </summary>
2458                 public GenericTypeExpr (TypeSpec open_type, TypeArguments args, Location l)
2459                 {
2460                         this.open_type = open_type;
2461                         loc = l;
2462                         this.args = args;
2463                 }
2464
2465                 public override string GetSignatureForError ()
2466                 {
2467                         return type.GetSignatureForError ();
2468                 }
2469
2470                 public override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
2471                 {
2472                         if (eclass != ExprClass.Unresolved)
2473                                 return type;
2474
2475                         if (!args.Resolve (mc, allowUnboundTypeArguments))
2476                                 return null;
2477
2478                         TypeSpec[] atypes = args.Arguments;
2479                         if (atypes == null)
2480                                 return null;
2481
2482                         //
2483                         // Now bind the parameters
2484                         //
2485                         var inflated = open_type.MakeGenericType (mc, atypes);
2486                         type = inflated;
2487                         eclass = ExprClass.Type;
2488
2489                         //
2490                         // The constraints can be checked only when full type hierarchy is known
2491                         //
2492                         if (!inflated.HasConstraintsChecked && mc.Module.HasTypesFullyDefined) {
2493                                 var constraints = inflated.Constraints;
2494                                 if (constraints != null) {
2495                                         var cc = new ConstraintChecker (mc);
2496                                         if (cc.CheckAll (open_type, atypes, constraints, loc)) {
2497                                                 inflated.HasConstraintsChecked = true;
2498                                         }
2499                                 }
2500                         }
2501
2502                         return type;
2503                 }
2504
2505                 public override bool Equals (object obj)
2506                 {
2507                         GenericTypeExpr cobj = obj as GenericTypeExpr;
2508                         if (cobj == null)
2509                                 return false;
2510
2511                         if ((type == null) || (cobj.type == null))
2512                                 return false;
2513
2514                         return type == cobj.type;
2515                 }
2516
2517                 public override int GetHashCode ()
2518                 {
2519                         return base.GetHashCode ();
2520                 }
2521         }
2522
2523         //
2524         // Generic type with unbound type arguments, used for typeof (G<,,>)
2525         //
2526         class GenericOpenTypeExpr : TypeExpression
2527         {
2528                 public GenericOpenTypeExpr (TypeSpec type, /*UnboundTypeArguments args,*/ Location loc)
2529                         : base (type.GetDefinition (), loc)
2530                 {
2531                 }
2532         }
2533
2534         struct ConstraintChecker
2535         {
2536                 IMemberContext mc;
2537                 bool recursive_checks;
2538
2539                 public ConstraintChecker (IMemberContext ctx)
2540                 {
2541                         this.mc = ctx;
2542                         recursive_checks = false;
2543                 }
2544
2545                 //
2546                 // Checks the constraints of open generic type against type
2547                 // arguments. This version is used for types which could not be
2548                 // checked immediatelly during construction because the type
2549                 // hierarchy was not yet fully setup (before Emit phase)
2550                 //
2551                 public static bool Check (IMemberContext mc, TypeSpec type, Location loc)
2552                 {
2553                         //
2554                         // Check declaring type first if there is any
2555                         //
2556                         if (type.DeclaringType != null && !Check (mc, type.DeclaringType, loc))
2557                                 return false;
2558
2559                         while (type is ElementTypeSpec)
2560                                 type = ((ElementTypeSpec) type).Element;
2561
2562                         if (type.Arity == 0)
2563                                 return true;
2564
2565                         var gtype = type as InflatedTypeSpec;
2566                         if (gtype == null)
2567                                 return true;
2568
2569                         var constraints = gtype.Constraints;
2570                         if (constraints == null)
2571                                 return true;
2572
2573                         if (gtype.HasConstraintsChecked)
2574                                 return true;
2575
2576                         var cc = new ConstraintChecker (mc);
2577                         cc.recursive_checks = true;
2578
2579                         if (cc.CheckAll (gtype.GetDefinition (), type.TypeArguments, constraints, loc)) {
2580                                 gtype.HasConstraintsChecked = true;
2581                                 return true;
2582                         }
2583
2584                         return false;
2585                 }
2586
2587                 //
2588                 // Checks all type arguments againts type parameters constraints
2589                 // NOTE: It can run in probing mode when `this.mc' is null
2590                 //
2591                 public bool CheckAll (MemberSpec context, TypeSpec[] targs, TypeParameterSpec[] tparams, Location loc)
2592                 {
2593                         if (targs == null)
2594                                 return true;
2595
2596                         for (int i = 0; i < tparams.Length; i++) {
2597                                 var targ = targs[i];
2598                                 if (!CheckConstraint (context, targ, tparams [i], loc))
2599                                         return false;
2600
2601                                 if (!recursive_checks)
2602                                         continue;
2603
2604                                 if (!Check (mc, targ, loc))
2605                                         return false;
2606                         }
2607
2608                         return true;
2609                 }
2610
2611                 bool CheckConstraint (MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, Location loc)
2612                 {
2613                         //
2614                         // First, check the `class' and `struct' constraints.
2615                         //
2616                         if (tparam.HasSpecialClass && !TypeSpec.IsReferenceType (atype)) {
2617                                 if (mc != null) {
2618                                         mc.Module.Compiler.Report.Error (452, loc,
2619                                                 "The type `{0}' must be a reference type in order to use it as type parameter `{1}' in the generic type or method `{2}'",
2620                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2621                                 }
2622
2623                                 return false;
2624                         }
2625
2626                         if (tparam.HasSpecialStruct && (!TypeSpec.IsValueType (atype) || atype.IsNullableType)) {
2627                                 if (mc != null) {
2628                                         mc.Module.Compiler.Report.Error (453, loc,
2629                                                 "The type `{0}' must be a non-nullable value type in order to use it as type parameter `{1}' in the generic type or method `{2}'",
2630                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2631                                 }
2632
2633                                 return false;
2634                         }
2635
2636                         bool ok = true;
2637
2638                         //
2639                         // Check the class constraint
2640                         //
2641                         if (tparam.HasTypeConstraint) {
2642                                 if (!CheckConversion (mc, context, atype, tparam, tparam.BaseType, loc)) {
2643                                         if (mc == null)
2644                                                 return false;
2645
2646                                         ok = false;
2647                                 }
2648                         }
2649
2650                         //
2651                         // Check the interfaces constraints
2652                         //
2653                         if (tparam.InterfacesDefined != null) {
2654                                 foreach (TypeSpec iface in tparam.InterfacesDefined) {
2655                                         if (!CheckConversion (mc, context, atype, tparam, iface, loc)) {
2656                                                 if (mc == null)
2657                                                         return false;
2658
2659                                                 ok = false;
2660                                                 break;
2661                                         }
2662                                 }
2663                         }
2664
2665                         //
2666                         // Check the type parameter constraint
2667                         //
2668                         if (tparam.TypeArguments != null) {
2669                                 foreach (var ta in tparam.TypeArguments) {
2670                                         if (!CheckConversion (mc, context, atype, tparam, ta, loc)) {
2671                                                 if (mc == null)
2672                                                         return false;
2673
2674                                                 ok = false;
2675                                                 break;
2676                                         }
2677                                 }
2678                         }
2679
2680                         //
2681                         // Finally, check the constructor constraint.
2682                         //
2683                         if (!tparam.HasSpecialConstructor)
2684                                 return ok;
2685
2686                         if (!HasDefaultConstructor (atype)) {
2687                                 if (mc != null) {
2688                                         mc.Module.Compiler.Report.SymbolRelatedToPreviousError (atype);
2689                                         mc.Module.Compiler.Report.Error (310, loc,
2690                                                 "The type `{0}' must have a public parameterless constructor in order to use it as parameter `{1}' in the generic type or method `{2}'",
2691                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2692                                 }
2693                                 return false;
2694                         }
2695
2696                         return ok;
2697                 }
2698
2699                 static bool HasDynamicTypeArgument (TypeSpec[] targs)
2700                 {
2701                         for (int i = 0; i < targs.Length; ++i) {
2702                                 var targ = targs [i];
2703                                 if (targ.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2704                                         return true;
2705
2706                                 if (HasDynamicTypeArgument (targ.TypeArguments))
2707                                         return true;
2708                         }
2709
2710                         return false;
2711                 }
2712
2713                 bool CheckConversion (IMemberContext mc, MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, TypeSpec ttype, Location loc)
2714                 {
2715                         if (atype == ttype)
2716                                 return true;
2717
2718                         if (atype.IsGenericParameter) {
2719                                 var tps = (TypeParameterSpec) atype;
2720                                 if (tps.HasDependencyOn (ttype))
2721                                         return true;
2722
2723                                 if (Convert.ImplicitTypeParameterConversion (null, tps, ttype) != null)
2724                                         return true;
2725
2726                         } else if (TypeSpec.IsValueType (atype)) {
2727                                 if (atype.IsNullableType) {
2728                                         //
2729                                         // LAMESPEC: Only identity or base type ValueType or Object satisfy nullable type
2730                                         //
2731                                         if (TypeSpec.IsBaseClass (atype, ttype, false))
2732                                                 return true;
2733                                 } else {
2734                                         if (Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2735                                                 return true;
2736                                 }
2737                         } else {
2738                                 if (Convert.ImplicitReferenceConversionExists (atype, ttype) || Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2739                                         return true;
2740                         }
2741
2742                         if (mc != null) {
2743                                 mc.Module.Compiler.Report.SymbolRelatedToPreviousError (tparam);
2744                                 if (atype.IsGenericParameter) {
2745                                         mc.Module.Compiler.Report.Error (314, loc,
2746                                                 "The type `{0}' cannot be used as type parameter `{1}' in the generic type or method `{2}'. There is no boxing or type parameter conversion from `{0}' to `{3}'",
2747                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2748                                 } else if (TypeSpec.IsValueType (atype)) {
2749                                         if (atype.IsNullableType) {
2750                                                 if (ttype.IsInterface) {
2751                                                         mc.Module.Compiler.Report.Error (313, loc,
2752                                                                 "The type `{0}' cannot be used as type parameter `{1}' in the generic type or method `{2}'. The nullable type `{0}' never satisfies interface constraint `{3}'",
2753                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2754                                                 } else {
2755                                                         mc.Module.Compiler.Report.Error (312, loc,
2756                                                                 "The type `{0}' cannot be used as type parameter `{1}' in the generic type or method `{2}'. The nullable type `{0}' does not satisfy constraint `{3}'",
2757                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2758                                                 }
2759                                         } else {
2760                                                 mc.Module.Compiler.Report.Error (315, loc,
2761                                                         "The type `{0}' cannot be used as type parameter `{1}' in the generic type or method `{2}'. There is no boxing conversion from `{0}' to `{3}'",
2762                                                         atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2763                                         }
2764                                 } else {
2765                                         mc.Module.Compiler.Report.Error (311, loc,
2766                                                 "The type `{0}' cannot be used as type parameter `{1}' in the generic type or method `{2}'. There is no implicit reference conversion from `{0}' to `{3}'",
2767                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2768                                 }
2769                         }
2770
2771                         return false;
2772                 }
2773
2774                 static bool HasDefaultConstructor (TypeSpec atype)
2775                 {
2776                         var tp = atype as TypeParameterSpec;
2777                         if (tp != null) {
2778                                 return tp.HasSpecialConstructor || tp.HasSpecialStruct;
2779                         }
2780
2781                         if (atype.IsStruct || atype.IsEnum)
2782                                 return true;
2783
2784                         if (atype.IsAbstract)
2785                                 return false;
2786
2787                         var tdef = atype.GetDefinition ();
2788
2789                         var found = MemberCache.FindMember (tdef,
2790                                 MemberFilter.Constructor (ParametersCompiled.EmptyReadOnlyParameters),
2791                                 BindingRestriction.DeclaredOnly | BindingRestriction.InstanceOnly);
2792
2793                         return found != null && (found.Modifiers & Modifiers.PUBLIC) != 0;
2794                 }
2795         }
2796
2797         //
2798         // Implements C# type inference
2799         //
2800         class TypeInference
2801         {
2802                 //
2803                 // Tracks successful rate of type inference
2804                 //
2805                 int score;
2806                 readonly Arguments arguments;
2807                 readonly int arg_count;
2808
2809                 public TypeInference (Arguments arguments)
2810                 {
2811                         this.arguments = arguments;
2812                         if (arguments != null)
2813                                 arg_count = arguments.Count;
2814                 }
2815
2816                 public int InferenceScore {
2817                         get {
2818                                 return score;
2819                         }
2820                 }
2821
2822                 public TypeSpec[] InferMethodArguments (ResolveContext ec, MethodSpec method)
2823                 {
2824                         var method_generic_args = method.GenericDefinition.TypeParameters;
2825                         TypeInferenceContext context = new TypeInferenceContext (method_generic_args);
2826                         if (!context.UnfixedVariableExists)
2827                                 return TypeSpec.EmptyTypes;
2828
2829                         AParametersCollection pd = method.Parameters;
2830                         if (!InferInPhases (ec, context, pd))
2831                                 return null;
2832
2833                         return context.InferredTypeArguments;
2834                 }
2835
2836                 //
2837                 // Implements method type arguments inference
2838                 //
2839                 bool InferInPhases (ResolveContext ec, TypeInferenceContext tic, AParametersCollection methodParameters)
2840                 {
2841                         int params_arguments_start;
2842                         if (methodParameters.HasParams) {
2843                                 params_arguments_start = methodParameters.Count - 1;
2844                         } else {
2845                                 params_arguments_start = arg_count;
2846                         }
2847
2848                         TypeSpec [] ptypes = methodParameters.Types;
2849
2850                         //
2851                         // The first inference phase
2852                         //
2853                         TypeSpec method_parameter = null;
2854                         for (int i = 0; i < arg_count; i++) {
2855                                 Argument a = arguments [i];
2856                                 if (a == null)
2857                                         continue;
2858
2859                                 if (i < params_arguments_start) {
2860                                         method_parameter = methodParameters.Types [i];
2861                                 } else if (i == params_arguments_start) {
2862                                         if (arg_count == params_arguments_start + 1 && TypeManager.HasElementType (a.Type))
2863                                                 method_parameter = methodParameters.Types [params_arguments_start];
2864                                         else
2865                                                 method_parameter = TypeManager.GetElementType (methodParameters.Types [params_arguments_start]);
2866
2867                                         ptypes = (TypeSpec[]) ptypes.Clone ();
2868                                         ptypes [i] = method_parameter;
2869                                 }
2870
2871                                 //
2872                                 // When a lambda expression, an anonymous method
2873                                 // is used an explicit argument type inference takes a place
2874                                 //
2875                                 AnonymousMethodExpression am = a.Expr as AnonymousMethodExpression;
2876                                 if (am != null) {
2877                                         if (am.ExplicitTypeInference (tic, method_parameter))
2878                                                 ++score;
2879                                         continue;
2880                                 }
2881
2882                                 if (a.IsByRef) {
2883                                         score += tic.ExactInference (a.Type, method_parameter);
2884                                         continue;
2885                                 }
2886
2887                                 if (a.Expr.Type == InternalType.NullLiteral)
2888                                         continue;
2889
2890                                 if (TypeSpec.IsValueType (method_parameter)) {
2891                                         score += tic.LowerBoundInference (a.Type, method_parameter);
2892                                         continue;
2893                                 }
2894
2895                                 //
2896                                 // Otherwise an output type inference is made
2897                                 //
2898                                 score += tic.OutputTypeInference (ec, a.Expr, method_parameter);
2899                         }
2900
2901                         //
2902                         // Part of the second phase but because it happens only once
2903                         // we don't need to call it in cycle
2904                         //
2905                         bool fixed_any = false;
2906                         if (!tic.FixIndependentTypeArguments (ec, ptypes, ref fixed_any))
2907                                 return false;
2908
2909                         return DoSecondPhase (ec, tic, ptypes, !fixed_any);
2910                 }
2911
2912                 bool DoSecondPhase (ResolveContext ec, TypeInferenceContext tic, TypeSpec[] methodParameters, bool fixDependent)
2913                 {
2914                         bool fixed_any = false;
2915                         if (fixDependent && !tic.FixDependentTypes (ec, ref fixed_any))
2916                                 return false;
2917
2918                         // If no further unfixed type variables exist, type inference succeeds
2919                         if (!tic.UnfixedVariableExists)
2920                                 return true;
2921
2922                         if (!fixed_any && fixDependent)
2923                                 return false;
2924
2925                         // For all arguments where the corresponding argument output types
2926                         // contain unfixed type variables but the input types do not,
2927                         // an output type inference is made
2928                         for (int i = 0; i < arg_count; i++) {
2929
2930                                 // Align params arguments
2931                                 TypeSpec t_i = methodParameters [i >= methodParameters.Length ? methodParameters.Length - 1: i];
2932
2933                                 if (!t_i.IsDelegate) {
2934                                         if (!t_i.IsExpressionTreeType)
2935                                                 continue;
2936
2937                                         t_i = TypeManager.GetTypeArguments (t_i) [0];
2938                                 }
2939
2940                                 var mi = Delegate.GetInvokeMethod (t_i);
2941                                 TypeSpec rtype = mi.ReturnType;
2942
2943                                 if (tic.IsReturnTypeNonDependent (mi, rtype)) {
2944                                         // It can be null for default arguments
2945                                         if (arguments[i] == null)
2946                                                 continue;
2947
2948                                         score += tic.OutputTypeInference (ec, arguments[i].Expr, t_i);
2949                                 }
2950                         }
2951
2952
2953                         return DoSecondPhase (ec, tic, methodParameters, true);
2954                 }
2955         }
2956
2957         public class TypeInferenceContext
2958         {
2959                 protected enum BoundKind
2960                 {
2961                         Exact   = 0,
2962                         Lower   = 1,
2963                         Upper   = 2
2964                 }
2965
2966                 struct BoundInfo : IEquatable<BoundInfo>
2967                 {
2968                         public readonly TypeSpec Type;
2969                         public readonly BoundKind Kind;
2970
2971                         public BoundInfo (TypeSpec type, BoundKind kind)
2972                         {
2973                                 this.Type = type;
2974                                 this.Kind = kind;
2975                         }
2976
2977                         public override int GetHashCode ()
2978                         {
2979                                 return Type.GetHashCode ();
2980                         }
2981
2982                         public Expression GetTypeExpression ()
2983                         {
2984                                 return new TypeExpression (Type, Location.Null);
2985                         }
2986
2987                         #region IEquatable<BoundInfo> Members
2988
2989                         public bool Equals (BoundInfo other)
2990                         {
2991                                 return Type == other.Type && Kind == other.Kind;
2992                         }
2993
2994                         #endregion
2995                 }
2996
2997                 readonly TypeSpec[] tp_args;
2998                 readonly TypeSpec[] fixed_types;
2999                 readonly List<BoundInfo>[] bounds;
3000
3001                 // TODO MemberCache: Could it be TypeParameterSpec[] ??
3002                 public TypeInferenceContext (TypeSpec[] typeArguments)
3003                 {
3004                         if (typeArguments.Length == 0)
3005                                 throw new ArgumentException ("Empty generic arguments");
3006
3007                         fixed_types = new TypeSpec [typeArguments.Length];
3008                         for (int i = 0; i < typeArguments.Length; ++i) {
3009                                 if (typeArguments [i].IsGenericParameter) {
3010                                         if (bounds == null) {
3011                                                 bounds = new List<BoundInfo> [typeArguments.Length];
3012                                                 tp_args = new TypeSpec [typeArguments.Length];
3013                                         }
3014                                         tp_args [i] = typeArguments [i];
3015                                 } else {
3016                                         fixed_types [i] = typeArguments [i];
3017                                 }
3018                         }
3019                 }
3020
3021                 //
3022                 // Used together with AddCommonTypeBound fo implement
3023                 // 7.4.2.13 Finding the best common type of a set of expressions
3024                 //
3025                 public TypeInferenceContext ()
3026                 {
3027                         fixed_types = new TypeSpec [1];
3028                         tp_args = new TypeSpec [1];
3029                         tp_args[0] = InternalType.Arglist; // it can be any internal type
3030                         bounds = new List<BoundInfo> [1];
3031                 }
3032
3033                 public TypeSpec[] InferredTypeArguments {
3034                         get {
3035                                 return fixed_types;
3036                         }
3037                 }
3038
3039                 public void AddCommonTypeBound (TypeSpec type)
3040                 {
3041                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, false);
3042                 }
3043
3044                 public void AddCommonTypeBoundAsync (TypeSpec type)
3045                 {
3046                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, true);
3047                 }
3048
3049                 void AddToBounds (BoundInfo bound, int index, bool voidAllowed)
3050                 {
3051                         //
3052                         // Some types cannot be used as type arguments
3053                         //
3054                         if ((bound.Type.Kind == MemberKind.Void && !voidAllowed) || bound.Type.IsPointer || bound.Type.IsSpecialRuntimeType ||
3055                                 bound.Type == InternalType.MethodGroup || bound.Type == InternalType.AnonymousMethod || bound.Type == InternalType.VarOutType)
3056                                 return;
3057
3058                         var a = bounds [index];
3059                         if (a == null) {
3060                                 a = new List<BoundInfo> (2);
3061                                 a.Add (bound);
3062                                 bounds [index] = a;
3063                                 return;
3064                         }
3065
3066                         if (a.Contains (bound))
3067                                 return;
3068
3069                         a.Add (bound);
3070                 }
3071
3072                 bool AllTypesAreFixed (TypeSpec[] types)
3073                 {
3074                         foreach (TypeSpec t in types) {
3075                                 if (t.IsGenericParameter) {
3076                                         if (!IsFixed (t))
3077                                                 return false;
3078                                         continue;
3079                                 }
3080
3081                                 if (t.IsGeneric && !AllTypesAreFixed (t.TypeArguments))
3082                                         return false;
3083                         }
3084
3085                         return true;
3086                 }
3087
3088                 //
3089                 // 26.3.3.8 Exact Inference
3090                 //
3091                 public int ExactInference (TypeSpec u, TypeSpec v)
3092                 {
3093                         // If V is an array type
3094                         if (v.IsArray) {
3095                                 if (!u.IsArray)
3096                                         return 0;
3097
3098                                 var ac_u = (ArrayContainer) u;
3099                                 var ac_v = (ArrayContainer) v;
3100                                 if (ac_u.Rank != ac_v.Rank)
3101                                         return 0;
3102
3103                                 return ExactInference (ac_u.Element, ac_v.Element);
3104                         }
3105
3106                         // If V is constructed type and U is constructed type
3107                         if (TypeManager.IsGenericType (v)) {
3108                                 if (!TypeManager.IsGenericType (u) || v.MemberDefinition != u.MemberDefinition)
3109                                         return 0;
3110
3111                                 TypeSpec [] ga_u = TypeManager.GetTypeArguments (u);
3112                                 TypeSpec [] ga_v = TypeManager.GetTypeArguments (v);
3113                                 if (ga_u.Length != ga_v.Length)
3114                                         return 0;
3115
3116                                 int score = 0;
3117                                 for (int i = 0; i < ga_u.Length; ++i)
3118                                         score += ExactInference (ga_u [i], ga_v [i]);
3119
3120                                 return System.Math.Min (1, score);
3121                         }
3122
3123                         // If V is one of the unfixed type arguments
3124                         int pos = IsUnfixed (v);
3125                         if (pos == -1)
3126                                 return 0;
3127
3128                         AddToBounds (new BoundInfo (u, BoundKind.Exact), pos, false);
3129                         return 1;
3130                 }
3131
3132                 public bool FixAllTypes (ResolveContext ec)
3133                 {
3134                         for (int i = 0; i < tp_args.Length; ++i) {
3135                                 if (!FixType (ec, i))
3136                                         return false;
3137                         }
3138                         return true;
3139                 }
3140
3141                 //
3142                 // All unfixed type variables Xi are fixed for which all of the following hold:
3143                 // a, There is at least one type variable Xj that depends on Xi
3144                 // b, Xi has a non-empty set of bounds
3145                 //
3146                 public bool FixDependentTypes (ResolveContext ec, ref bool fixed_any)
3147                 {
3148                         for (int i = 0; i < tp_args.Length; ++i) {
3149                                 if (fixed_types[i] != null)
3150                                         continue;
3151
3152                                 if (bounds[i] == null)
3153                                         continue;
3154
3155                                 if (!FixType (ec, i))
3156                                         return false;
3157
3158                                 fixed_any = true;
3159                         }
3160
3161                         return true;
3162                 }
3163
3164                 //
3165                 // All unfixed type variables Xi which depend on no Xj are fixed
3166                 //
3167                 public bool FixIndependentTypeArguments (ResolveContext ec, TypeSpec[] methodParameters, ref bool fixed_any)
3168                 {
3169                         var types_to_fix = new List<TypeSpec> (tp_args);
3170                         for (int i = 0; i < methodParameters.Length; ++i) {
3171                                 TypeSpec t = methodParameters[i];
3172
3173                                 if (!t.IsDelegate) {
3174                                         if (!t.IsExpressionTreeType)
3175                                                 continue;
3176
3177                                         t =  TypeManager.GetTypeArguments (t) [0];
3178                                 }
3179
3180                                 if (t.IsGenericParameter)
3181                                         continue;
3182
3183                                 var invoke = Delegate.GetInvokeMethod (t);
3184                                 TypeSpec rtype = invoke.ReturnType;
3185                                 while (rtype.IsArray)
3186                                         rtype = ((ArrayContainer) rtype).Element;
3187
3188                                 if (!rtype.IsGenericParameter && !TypeManager.IsGenericType (rtype))
3189                                         continue;
3190
3191                                 // Remove dependent types, they cannot be fixed yet
3192                                 RemoveDependentTypes (types_to_fix, rtype);
3193                         }
3194
3195                         foreach (TypeSpec t in types_to_fix) {
3196                                 if (t == null)
3197                                         continue;
3198
3199                                 int idx = IsUnfixed (t);
3200                                 if (idx >= 0 && !FixType (ec, idx)) {
3201                                         return false;
3202                                 }
3203                         }
3204
3205                         fixed_any = types_to_fix.Count > 0;
3206                         return true;
3207                 }
3208
3209                 //
3210                 // 26.3.3.10 Fixing
3211                 //
3212                 public bool FixType (ResolveContext ec, int i)
3213                 {
3214                         // It's already fixed
3215                         if (fixed_types[i] != null)
3216                                 throw new InternalErrorException ("Type argument has been already fixed");
3217
3218                         var candidates = bounds [i];
3219                         if (candidates == null)
3220                                 return false;
3221
3222                         if (candidates.Count == 1) {
3223                                 TypeSpec t = candidates[0].Type;
3224                                 if (t == InternalType.NullLiteral)
3225                                         return false;
3226
3227                                 fixed_types [i] = t;
3228                                 return true;
3229                         }
3230
3231                         //
3232                         // The set of candidate types Uj starts out as the set of
3233                         // all types in the set of bounds for Xi
3234                         //
3235                         var applicable = new bool [candidates.Count];
3236                         for (int ci = 0; ci < applicable.Length; ++ci)
3237                                 applicable [ci] = true;
3238
3239                         for (int ci = 0; ci < applicable.Length; ++ci) {
3240                                 var bound = candidates [ci];
3241                                 int cii = 0;
3242
3243                                 switch (bound.Kind) {
3244                                 case BoundKind.Exact:
3245                                         for (; cii != applicable.Length; ++cii) {
3246                                                 if (ci == cii)
3247                                                         continue;
3248
3249                                                 if (!applicable[cii])
3250                                                         continue;
3251
3252                                                 //
3253                                                 // For each exact bound U of Xi all types Uj which are not identical
3254                                                 // to U are removed from the candidate set
3255                                                 //
3256                                                 if (candidates [cii].Type != bound.Type)
3257                                                         applicable[cii] = false;
3258                                         }
3259
3260                                         break;
3261                                 case BoundKind.Lower:
3262                                         for (; cii != applicable.Length; ++cii) {
3263                                                 if (ci == cii)
3264                                                         continue;
3265
3266                                                 if (!applicable[cii])
3267                                                         continue;
3268
3269                                                 //
3270                                                 // For each lower bound U of Xi all types Uj to which there is not an implicit conversion
3271                                                 // from U are removed from the candidate set
3272                                                 //
3273                                                 if (!Convert.ImplicitConversionExists (ec, bound.GetTypeExpression (), candidates [cii].Type)) {
3274                                                         applicable[cii] = false;
3275                                                 }
3276                                         }
3277
3278                                         break;
3279
3280                                 case BoundKind.Upper:
3281                                         for (; cii != applicable.Length; ++cii) {
3282                                                 if (ci == cii)
3283                                                         continue;
3284
3285                                                 if (!applicable[cii])
3286                                                         continue;
3287
3288                                                 //
3289                                                 // For each upper bound U of Xi all types Uj from which there is not an implicit conversion
3290                                                 // to U are removed from the candidate set
3291                                                 //
3292                                                 if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3293                                                         applicable[cii] = false;
3294                                         }
3295
3296                                         break;
3297                                 }
3298                         }
3299
3300                         TypeSpec best_candidate = null;
3301                         for (int ci = 0; ci < applicable.Length; ++ci) {
3302                                 if (!applicable[ci])
3303                                         continue;
3304
3305                                 var bound = candidates [ci];
3306                                 if (bound.Type == best_candidate)
3307                                         continue;
3308
3309                                 int cii = 0;
3310                                 for (; cii < applicable.Length; ++cii) {
3311                                         if (ci == cii)
3312                                                 continue;
3313
3314                                         if (!applicable[cii])
3315                                                 continue;
3316
3317                                         if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3318                                                 break;
3319                                 }
3320
3321                                 if (cii != applicable.Length)
3322                                         continue;
3323
3324                                 //
3325                                 // We already have the best candidate, break if it's different (non-unique)
3326                                 //
3327                                 // Dynamic is never ambiguous as we prefer dynamic over other best candidate types
3328                                 //
3329                                 if (best_candidate != null) {
3330
3331                                         if (best_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3332                                                 continue;
3333
3334                                         if (bound.Type.BuiltinType != BuiltinTypeSpec.Type.Dynamic && best_candidate != bound.Type)
3335                                                 return false;
3336                                 }
3337
3338                                 best_candidate = bound.Type;
3339                         }
3340
3341                         if (best_candidate == null)
3342                                 return false;
3343
3344                         fixed_types[i] = best_candidate;
3345                         return true;
3346                 }
3347
3348                 public bool HasBounds (int pos)
3349                 {
3350                         return bounds[pos] != null;
3351                 }
3352
3353                 //
3354                 // Uses inferred or partially infered types to inflate delegate type argument. Returns
3355                 // null when type parameter has not been fixed
3356                 //
3357                 public TypeSpec InflateGenericArgument (IModuleContext context, TypeSpec parameter)
3358                 {
3359                         var tp = parameter as TypeParameterSpec;
3360                         if (tp != null) {
3361                                 //
3362                                 // Type inference works on generic arguments (MVAR) only
3363                                 //
3364                                 if (!tp.IsMethodOwned)
3365                                         return parameter;
3366
3367                                 //
3368                                 // Ensure the type parameter belongs to same container
3369                                 //
3370                                 if (tp.DeclaredPosition < tp_args.Length && tp_args[tp.DeclaredPosition] == parameter)
3371                                         return fixed_types[tp.DeclaredPosition] ?? parameter;
3372
3373                                 return parameter;
3374                         }
3375
3376                         var gt = parameter as InflatedTypeSpec;
3377                         if (gt != null) {
3378                                 var inflated_targs = new TypeSpec [gt.TypeArguments.Length];
3379                                 for (int ii = 0; ii < inflated_targs.Length; ++ii) {
3380                                         var inflated = InflateGenericArgument (context, gt.TypeArguments [ii]);
3381                                         if (inflated == null)
3382                                                 return null;
3383
3384                                         inflated_targs[ii] = inflated;
3385                                 }
3386
3387                                 return gt.GetDefinition ().MakeGenericType (context, inflated_targs);
3388                         }
3389
3390                         var ac = parameter as ArrayContainer;
3391                         if (ac != null) {
3392                                 var inflated = InflateGenericArgument (context, ac.Element);
3393                                 if (inflated != ac.Element)
3394                                         return ArrayContainer.MakeType (context.Module, inflated);
3395                         }
3396
3397                         return parameter;
3398                 }
3399
3400                 //
3401                 // Tests whether all delegate input arguments are fixed and generic output type
3402                 // requires output type inference
3403                 //
3404                 public bool IsReturnTypeNonDependent (MethodSpec invoke, TypeSpec returnType)
3405                 {
3406                         AParametersCollection d_parameters = invoke.Parameters;
3407
3408                         if (d_parameters.IsEmpty)
3409                                 return true;
3410
3411                         while (returnType.IsArray)
3412                                 returnType = ((ArrayContainer) returnType).Element;
3413
3414                         if (returnType.IsGenericParameter) {
3415                                 if (IsFixed (returnType))
3416                                     return false;
3417                         } else if (TypeManager.IsGenericType (returnType)) {
3418                                 TypeSpec[] g_args = TypeManager.GetTypeArguments (returnType);
3419
3420                                 // At least one unfixed return type has to exist
3421                                 if (AllTypesAreFixed (g_args))
3422                                         return false;
3423                         } else {
3424                                 return false;
3425                         }
3426
3427                         // All generic input arguments have to be fixed
3428                         return AllTypesAreFixed (d_parameters.Types);
3429                 }
3430
3431                 bool IsFixed (TypeSpec type)
3432                 {
3433                         return IsUnfixed (type) == -1;
3434                 }
3435
3436                 int IsUnfixed (TypeSpec type)
3437                 {
3438                         if (!type.IsGenericParameter)
3439                                 return -1;
3440
3441                         for (int i = 0; i < tp_args.Length; ++i) {
3442                                 if (tp_args[i] == type) {
3443                                         if (fixed_types[i] != null)
3444                                                 break;
3445
3446                                         return i;
3447                                 }
3448                         }
3449
3450                         return -1;
3451                 }
3452
3453                 //
3454                 // 26.3.3.9 Lower-bound Inference
3455                 //
3456                 public int LowerBoundInference (TypeSpec u, TypeSpec v)
3457                 {
3458                         return LowerBoundInference (u, v, false);
3459                 }
3460
3461                 //
3462                 // Lower-bound (false) or Upper-bound (true) inference based on inversed argument
3463                 //
3464                 int LowerBoundInference (TypeSpec u, TypeSpec v, bool inversed)
3465                 {
3466                         // If V is one of the unfixed type arguments
3467                         int pos = IsUnfixed (v);
3468                         if (pos != -1) {
3469                                 AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos, false);
3470                                 return 1;
3471                         }
3472
3473                         // If U is an array type
3474                         var u_ac = u as ArrayContainer;
3475                         if (u_ac != null) {
3476                                 var v_ac = v as ArrayContainer;
3477                                 if (v_ac != null) {
3478                                         if (u_ac.Rank != v_ac.Rank)
3479                                                 return 0;
3480
3481                                         if (TypeSpec.IsValueType (u_ac.Element))
3482                                                 return ExactInference (u_ac.Element, v_ac.Element);
3483
3484                                         return LowerBoundInference (u_ac.Element, v_ac.Element, inversed);
3485                                 }
3486
3487                                 if (u_ac.Rank != 1 || !v.IsArrayGenericInterface)
3488                                         return 0;
3489
3490                                 var v_i = TypeManager.GetTypeArguments (v) [0];
3491                                 if (TypeSpec.IsValueType (u_ac.Element))
3492                                         return ExactInference (u_ac.Element, v_i);
3493
3494                                 return LowerBoundInference (u_ac.Element, v_i);
3495                         }
3496
3497                         if (v.IsGenericOrParentIsGeneric) {
3498                                 //
3499                                 // if V is a constructed type C<V1..Vk> and there is a unique type C<U1..Uk>
3500                                 // such that U is identical to, inherits from (directly or indirectly),
3501                                 // or implements (directly or indirectly) C<U1..Uk>
3502                                 //
3503                                 var u_candidates = new List<TypeSpec> ();
3504                                 var open_v = v.MemberDefinition;
3505
3506                                 for (TypeSpec t = u; t != null; t = t.BaseType) {
3507                                         if (open_v == t.MemberDefinition)
3508                                                 u_candidates.Add (t);
3509
3510                                         //
3511                                         // Using this trick for dynamic type inference, the spec says the type arguments are "unknown" but
3512                                         // that would complicate the process a lot, instead I treat them as dynamic
3513                                         //
3514                                         if (t.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3515                                                 u_candidates.Add (t);
3516                                 }
3517
3518                                 if (u.Interfaces != null) {
3519                                         foreach (var iface in u.Interfaces) {
3520                                                 if (open_v == iface.MemberDefinition)
3521                                                         u_candidates.Add (iface);
3522                                         }
3523                                 }
3524
3525                                 TypeSpec[] unique_candidate_targs = null;
3526                                 var ga_v = TypeSpec.GetAllTypeArguments (v);
3527                                 foreach (TypeSpec u_candidate in u_candidates) {
3528                                         //
3529                                         // The unique set of types U1..Uk means that if we have an interface I<T>,
3530                                         // class U : I<int>, I<long> then no type inference is made when inferring
3531                                         // type I<T> by applying type U because T could be int or long
3532                                         //
3533                                         if (unique_candidate_targs != null) {
3534                                                 TypeSpec[] second_unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3535                                                 if (TypeSpecComparer.Equals (unique_candidate_targs, second_unique_candidate_targs)) {
3536                                                         unique_candidate_targs = second_unique_candidate_targs;
3537                                                         continue;
3538                                                 }
3539
3540                                                 //
3541                                                 // Break when candidate arguments are ambiguous
3542                                                 //
3543                                                 return 0;
3544                                         }
3545
3546                                         //
3547                                         // A candidate is dynamic type expression, to simplify things use dynamic
3548                                         // for all type parameter of this type. For methods like this one
3549                                         //
3550                                         // void M<T, U> (IList<T>, IList<U[]>)
3551                                         //
3552                                         // dynamic becomes both T and U when the arguments are of dynamic type
3553                                         //
3554                                         if (u_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
3555                                                 unique_candidate_targs = new TypeSpec[ga_v.Length];
3556                                                 for (int i = 0; i < unique_candidate_targs.Length; ++i)
3557                                                         unique_candidate_targs[i] = u_candidate;
3558                                         } else {
3559                                                 unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3560                                         }
3561                                 }
3562
3563                                 if (unique_candidate_targs != null) {
3564                                         int score = 0;
3565                                         int tp_index = -1;
3566                                         TypeParameterSpec[] tps = null;
3567
3568                                         for (int i = 0; i < unique_candidate_targs.Length; ++i) {
3569                                                 if (tp_index < 0) {
3570                                                         while (v.Arity == 0)
3571                                                                 v = v.DeclaringType;
3572
3573                                                         tps = v.MemberDefinition.TypeParameters;
3574                                                         tp_index = tps.Length - 1;
3575                                                 }
3576
3577                                                 Variance variance = tps [tp_index--].Variance;
3578
3579                                                 TypeSpec u_i = unique_candidate_targs [i];
3580                                                 if (variance == Variance.None || TypeSpec.IsValueType (u_i)) {
3581                                                         if (ExactInference (u_i, ga_v [i]) == 0)
3582                                                                 ++score;
3583                                                 } else {
3584                                                         bool upper_bound = (variance == Variance.Contravariant && !inversed) ||
3585                                                                 (variance == Variance.Covariant && inversed);
3586
3587                                                         if (LowerBoundInference (u_i, ga_v [i], upper_bound) == 0)
3588                                                                 ++score;
3589                                                 }
3590                                         }
3591
3592                                         return score;
3593                                 }
3594                         }
3595
3596                         return 0;
3597                 }
3598
3599                 //
3600                 // 26.3.3.6 Output Type Inference
3601                 //
3602                 public int OutputTypeInference (ResolveContext ec, Expression e, TypeSpec t)
3603                 {
3604                         // If e is a lambda or anonymous method with inferred return type
3605                         AnonymousMethodExpression ame = e as AnonymousMethodExpression;
3606                         if (ame != null) {
3607                                 TypeSpec rt = ame.InferReturnType (ec, this, t);
3608                                 var invoke = Delegate.GetInvokeMethod (t);
3609
3610                                 if (rt == null) {
3611                                         AParametersCollection pd = invoke.Parameters;
3612                                         return ame.Parameters.Count == pd.Count ? 1 : 0;
3613                                 }
3614
3615                                 TypeSpec rtype = invoke.ReturnType;
3616                                 return LowerBoundInference (rt, rtype) + 1;
3617                         }
3618
3619                         //
3620                         // if E is a method group and T is a delegate type or expression tree type
3621                         // return type Tb with parameter types T1..Tk and return type Tb, and overload
3622                         // resolution of E with the types T1..Tk yields a single method with return type U,
3623                         // then a lower-bound inference is made from U for Tb.
3624                         //
3625                         if (e is MethodGroupExpr) {
3626                                 if (!t.IsDelegate) {
3627                                         if (!t.IsExpressionTreeType)
3628                                                 return 0;
3629
3630                                         t = TypeManager.GetTypeArguments (t)[0];
3631                                 }
3632
3633                                 var invoke = Delegate.GetInvokeMethod (t);
3634                                 TypeSpec rtype = invoke.ReturnType;
3635
3636                                 if (!IsReturnTypeNonDependent (invoke, rtype))
3637                                         return 0;
3638
3639                                 // LAMESPEC: Standard does not specify that all methodgroup arguments
3640                                 // has to be fixed but it does not specify how to do recursive type inference
3641                                 // either. We choose the simple option and infer return type only
3642                                 // if all delegate generic arguments are fixed.
3643                                 TypeSpec[] param_types = new TypeSpec [invoke.Parameters.Count];
3644                                 for (int i = 0; i < param_types.Length; ++i) {
3645                                         var inflated = InflateGenericArgument (ec, invoke.Parameters.Types[i]);
3646                                         if (inflated == null)
3647                                                 return 0;
3648
3649                                         param_types[i] = inflated;
3650                                 }
3651
3652                                 MethodGroupExpr mg = (MethodGroupExpr) e;
3653                                 Arguments args = DelegateCreation.CreateDelegateMethodArguments (ec, invoke.Parameters, param_types, e.Location);
3654                                 mg = mg.OverloadResolve (ec, ref args, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly);
3655                                 if (mg == null)
3656                                         return 0;
3657
3658                                 return LowerBoundInference (mg.BestCandidateReturnType, rtype) + 1;
3659                         }
3660
3661                         //
3662                         // if e is an expression with type U, then
3663                         // a lower-bound inference is made from U for T
3664                         //
3665                         return LowerBoundInference (e.Type, t) * 2;
3666                 }
3667
3668                 void RemoveDependentTypes (List<TypeSpec> types, TypeSpec returnType)
3669                 {
3670                         int idx = IsUnfixed (returnType);
3671                         if (idx >= 0) {
3672                                 types [idx] = null;
3673                                 return;
3674                         }
3675
3676                         if (TypeManager.IsGenericType (returnType)) {
3677                                 foreach (TypeSpec t in TypeManager.GetTypeArguments (returnType)) {
3678                                         RemoveDependentTypes (types, t);
3679                                 }
3680                         }
3681                 }
3682
3683                 public bool UnfixedVariableExists {
3684                         get {
3685                                 foreach (TypeSpec ut in fixed_types) {
3686                                         if (ut == null)
3687                                                 return true;
3688                                 }
3689
3690                                 return false;
3691                         }
3692                 }
3693         }
3694 }