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                                         t.CheckObsoleteness (context, c.Location);
 199                                 }
 200
 201                                 ConstraintChecker.Check (context, t, c.Location);
 202                         }
 203                 }
 204
 205                 //
 206                 // Resolve the constraints types with only possible early checks, return
 207                 // value `false' is reserved for recursive failure
 208                 //
 209                 public bool Resolve (IMemberContext context, TypeParameter tp)
 210                 {
 211                         if (resolved)
 212                                 return true;
 213
 214                         if (resolving)
 215                                 return false;
 216
 217                         resolving = true;
 218                         var spec = tp.Type;
 219                         List<TypeParameterSpec> tparam_types = null;
 220                         bool iface_found = false;
 221
 222                         spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;
 223
 224                         for (int i = 0; i < constraints.Count; ++i) {
 225                                 var constraint = constraints[i];
 226
 227                                 if (constraint is SpecialContraintExpr) {
 228                                         spec.SpecialConstraint |= ((SpecialContraintExpr) constraint).Constraint;
 229                                         if (spec.HasSpecialStruct)
 230                                                 spec.BaseType = context.Module.Compiler.BuiltinTypes.ValueType;
 231
 232                                         // Set to null as it does not have a type
 233                                         constraints[i] = null;
 234                                         continue;
 235                                 }
 236
 237                                 var type = constraint.ResolveAsType (context);
 238                                 if (type == null)
 239                                         continue;
 240
 241                                 if (type.Arity > 0 && ((InflatedTypeSpec) type).HasDynamicArgument ()) {
 242                                         context.Module.Compiler.Report.Error (1968, constraint.Location,
 243                                                 "A constraint cannot be the dynamic type `{0}'", type.GetSignatureForError ());
 244                                         continue;
 245                                 }
 246
 247                                 if (!context.CurrentMemberDefinition.IsAccessibleAs (type)) {
 248                                         context.Module.Compiler.Report.SymbolRelatedToPreviousError (type);
 249                                         context.Module.Compiler.Report.Error (703, loc,
 250                                                 "Inconsistent accessibility: constraint type `{0}' is less accessible than `{1}'",
 251                                                 type.GetSignatureForError (), context.GetSignatureForError ());
 252                                 }
 253
 254                                 if (type.IsInterface) {
 255                                         if (!spec.AddInterface (type)) {
 256                                                 context.Module.Compiler.Report.Error (405, constraint.Location,
 257                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 258                                         }
 259
 260                                         iface_found = true;
 261                                         continue;
 262                                 }
 263
 264                                 var constraint_tp = type as TypeParameterSpec;
 265                                 if (constraint_tp != null) {
 266                                         if (tparam_types == null) {
 267                                                 tparam_types = new List<TypeParameterSpec> (2);
 268                                         } else if (tparam_types.Contains (constraint_tp)) {
 269                                                 context.Module.Compiler.Report.Error (405, constraint.Location,
 270                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 271                                                 continue;
 272                                         }
 273
 274                                         //
 275                                         // Checks whether each generic method parameter constraint type
 276                                         // is valid with respect to T
 277                                         //
 278                                         if (tp.IsMethodTypeParameter) {
 279                                                 VarianceDecl.CheckTypeVariance (type, Variance.Contravariant, context);
 280                                         }
 281
 282                                         var tp_def = constraint_tp.MemberDefinition as TypeParameter;
 283                                         if (tp_def != null && !tp_def.ResolveConstraints (context)) {
 284                                                 context.Module.Compiler.Report.Error (454, constraint.Location,
 285                                                         "Circular constraint dependency involving `{0}' and `{1}'",
 286                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 287                                                 continue;
 288                                         }
 289
 290                                         //
 291                                         // Checks whether there are no conflicts between type parameter constraints
 292                                         //
 293                                         // class Foo<T, U>
 294                                         //      where T : A
 295                                         //      where U : B, T
 296                                         //
 297                                         // A and B are not convertible and only 1 class constraint is allowed
 298                                         //
 299                                         if (constraint_tp.HasTypeConstraint) {
 300                                                 if (spec.HasTypeConstraint || spec.HasSpecialStruct) {
 301                                                         if (!CheckConflictingInheritedConstraint (spec, constraint_tp.BaseType, context, constraint.Location))
 302                                                                 continue;
 303                                                 } else {
 304                                                         for (int ii = 0; ii < tparam_types.Count; ++ii) {
 305                                                                 if (!tparam_types[ii].HasTypeConstraint)
 306                                                                         continue;
 307
 308                                                                 if (!CheckConflictingInheritedConstraint (spec, tparam_types[ii].BaseType, constraint_tp.BaseType, context, constraint.Location))
 309                                                                         break;
 310                                                         }
 311                                                 }
 312                                         }
 313
 314                                         if (constraint_tp.TypeArguments != null) {
 315                                                 var eb = constraint_tp.GetEffectiveBase ();
 316                                                 if (eb != null && !CheckConflictingInheritedConstraint (spec, eb, spec.BaseType, context, constraint.Location))
 317                                                         break;
 318                                         }
 319
 320                                         if (constraint_tp.HasSpecialStruct) {
 321                                                 context.Module.Compiler.Report.Error (456, constraint.Location,
 322                                                         "Type parameter `{0}' has the `struct' constraint, so it cannot be used as a constraint for `{1}'",
 323                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 324                                                 continue;
 325                                         }
 326
 327                                         tparam_types.Add (constraint_tp);
 328                                         continue;
 329                                 }
 330
 331                                 if (iface_found || spec.HasTypeConstraint) {
 332                                         context.Module.Compiler.Report.Error (406, constraint.Location,
 333                                                 "The class type constraint `{0}' must be listed before any other constraints. Consider moving type constraint to the beginning of the constraint list",
 334                                                 type.GetSignatureForError ());
 335                                 }
 336
 337                                 if (spec.HasSpecialStruct || spec.HasSpecialClass) {
 338                                         context.Module.Compiler.Report.Error (450, constraint.Location,
 339                                                 "`{0}': cannot specify both a constraint class and the `class' or `struct' constraint",
 340                                                 type.GetSignatureForError ());
 341                                 }
 342
 343                                 switch (type.BuiltinType) {
 344                                 case BuiltinTypeSpec.Type.Array:
 345                                 case BuiltinTypeSpec.Type.Delegate:
 346                                 case BuiltinTypeSpec.Type.MulticastDelegate:
 347                                 case BuiltinTypeSpec.Type.Enum:
 348                                 case BuiltinTypeSpec.Type.ValueType:
 349                                 case BuiltinTypeSpec.Type.Object:
 350                                         context.Module.Compiler.Report.Error (702, constraint.Location,
 351                                                 "A constraint cannot be special class `{0}'", type.GetSignatureForError ());
 352                                         continue;
 353                                 case BuiltinTypeSpec.Type.Dynamic:
 354                                         context.Module.Compiler.Report.Error (1967, constraint.Location,
 355                                                 "A constraint cannot be the dynamic type");
 356                                         continue;
 357                                 }
 358
 359                                 if (type.IsSealed || !type.IsClass) {
 360                                         context.Module.Compiler.Report.Error (701, loc,
 361                                                 "`{0}' is not a valid constraint. A constraint must be an interface, a non-sealed class or a type parameter",
 362                                                 type.GetSignatureForError ());
 363                                         continue;
 364                                 }
 365
 366                                 if (type.IsStatic) {
 367                                         context.Module.Compiler.Report.Error (717, constraint.Location,
 368                                                 "`{0}' is not a valid constraint. Static classes cannot be used as constraints",
 369                                                 type.GetSignatureForError ());
 370                                 }
 371
 372                                 spec.BaseType = type;
 373                         }
 374
 375                         if (tparam_types != null)
 376                                 spec.TypeArguments = tparam_types.ToArray ();
 377
 378                         resolving = false;
 379                         resolved = true;
 380                         return true;
 381                 }
 382
 383                 public void VerifyClsCompliance (Report report)
 384                 {
 385                         foreach (var c in constraints)
 386                         {
 387                                 if (c == null)
 388                                         continue;
 389
 390                                 if (!c.Type.IsCLSCompliant ()) {
 391                                         report.SymbolRelatedToPreviousError (c.Type);
 392                                         report.Warning (3024, 1, loc, "Constraint type `{0}' is not CLS-compliant",
 393                                                 c.Type.GetSignatureForError ());
 394                                 }
 395                         }
 396                 }
 397         }
 398
 399         //
 400         // A type parameter for a generic type or generic method definition
 401         //
 402         public class TypeParameter : MemberCore, ITypeDefinition
 403         {
 404                 static readonly string[] attribute_target = { "type parameter" };
 405
 406                 Constraints constraints;
 407                 GenericTypeParameterBuilder builder;
 408                 readonly TypeParameterSpec spec;
 409
 410                 public TypeParameter (int index, MemberName name, Constraints constraints, Attributes attrs, Variance Variance)
 411                         : base (null, name, attrs)
 412                 {
 413                         this.constraints = constraints;
 414                         this.spec = new TypeParameterSpec (null, index, this, SpecialConstraint.None, Variance, null);
 415                 }
 416
 417                 //
 418                 // Used by parser
 419                 //
 420                 public TypeParameter (MemberName name, Attributes attrs, VarianceDecl variance)
 421                         : base (null, name, attrs)
 422                 {
 423                         var var = variance == null ? Variance.None : variance.Variance;
 424                         this.spec = new TypeParameterSpec (null, -1, this, SpecialConstraint.None, var, null);
 425                         this.VarianceDecl = variance;
 426                 }
 427
 428                 public TypeParameter (TypeParameterSpec spec, TypeSpec parentSpec, MemberName name, Attributes attrs)
 429                         : base (null, name, attrs)
 430                 {
 431                         this.spec = new TypeParameterSpec (parentSpec, spec.DeclaredPosition, this, spec.SpecialConstraint, spec.Variance, null) {
 432                                 BaseType = spec.BaseType,
 433                                 InterfacesDefined = spec.InterfacesDefined,
 434                                 TypeArguments = spec.TypeArguments
 435                         };
 436                 }
 437
 438                 #region Properties
 439
 440                 public override AttributeTargets AttributeTargets {
 441                         get {
 442                                 return AttributeTargets.GenericParameter;
 443                         }
 444                 }
 445
 446                 public Constraints Constraints {
 447                         get {
 448                                 return constraints;
 449                         }
 450                         set {
 451                                 constraints = value;
 452                         }
 453                 }
 454
 455                 public IAssemblyDefinition DeclaringAssembly {
 456                         get     {
 457                                 return Module.DeclaringAssembly;
 458                         }
 459                 }
 460
 461                 public override string DocCommentHeader {
 462                         get {
 463                                 throw new InvalidOperationException (
 464                                         "Unexpected attempt to get doc comment from " + this.GetType ());
 465                         }
 466                 }
 467
 468                 bool ITypeDefinition.IsComImport {
 469                         get {
 470                                 return false;
 471                         }
 472                 }
 473
 474                 bool ITypeDefinition.IsPartial {
 475                         get {
 476                                 return false;
 477                         }
 478                 }
 479
 480                 public bool IsMethodTypeParameter {
 481                         get {
 482                                 return spec.IsMethodOwned;
 483                         }
 484                 }
 485
 486                 bool ITypeDefinition.IsTypeForwarder {
 487                         get {
 488                                 return false;
 489                         }
 490                 }
 491
 492                 bool ITypeDefinition.IsCyclicTypeForwarder {
 493                         get {
 494                                 return false;
 495                         }
 496                 }
 497
 498                 public string Name {
 499                         get {
 500                                 return MemberName.Name;
 501                         }
 502                 }
 503
 504                 public string Namespace {
 505                         get {
 506                                 return null;
 507                         }
 508                 }
 509
 510                 public TypeParameterSpec Type {
 511                         get {
 512                                 return spec;
 513                         }
 514                 }
 515
 516                 public int TypeParametersCount {
 517                         get {
 518                                 return 0;
 519                         }
 520                 }
 521
 522                 public TypeParameterSpec[] TypeParameters {
 523                         get {
 524                                 return null;
 525                         }
 526                 }
 527
 528                 public override string[] ValidAttributeTargets {
 529                         get {
 530                                 return attribute_target;
 531                         }
 532                 }
 533
 534                 public Variance Variance {
 535                         get {
 536                                 return spec.Variance;
 537                         }
 538                 }
 539
 540                 public VarianceDecl VarianceDecl { get; private set; }
 541
 542                 #endregion
 543
 544                 //
 545                 // This is called for each part of a partial generic type definition.
 546                 //
 547                 // If partial type parameters constraints are not null and we don't
 548                 // already have constraints they become our constraints. If we already
 549                 // have constraints, we must check that they're same.
 550                 //
 551                 public bool AddPartialConstraints (TypeDefinition part, TypeParameter tp)
 552                 {
 553                         if (builder == null)
 554                                 throw new InvalidOperationException ();
 555
 556                         var new_constraints = tp.constraints;
 557                         if (new_constraints == null)
 558                                 return true;
 559
 560                         // TODO: could create spec only
 561                         //tp.Define (null, -1, part.Definition);
 562                         tp.spec.DeclaringType = part.Definition;
 563                         if (!tp.ResolveConstraints (part))
 564                                 return false;
 565
 566                         if (constraints != null)
 567                                 return spec.HasSameConstraintsDefinition (tp.Type);
 568
 569                         // Copy constraint from resolved part to partial container
 570                         spec.SpecialConstraint = tp.spec.SpecialConstraint;
 571                         spec.InterfacesDefined = tp.spec.InterfacesDefined;
 572                         spec.TypeArguments = tp.spec.TypeArguments;
 573                         spec.BaseType = tp.spec.BaseType;
 574
 575                         return true;
 576                 }
 577
 578                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 579                 {
 580                         builder.SetCustomAttribute ((ConstructorInfo) ctor.GetMetaInfo (), cdata);
 581                 }
 582
 583                 public void CheckGenericConstraints (bool obsoleteCheck)
 584                 {
 585                         if (constraints != null)
 586                                 constraints.CheckGenericConstraints (this, obsoleteCheck);
 587                 }
 588
 589                 public TypeParameter CreateHoistedCopy (TypeSpec declaringSpec)
 590                 {
 591                         return new TypeParameter (spec, declaringSpec, MemberName, null);
 592                 }
 593
 594                 public override bool Define ()
 595                 {
 596                         return true;
 597                 }
 598
 599                 //
 600                 // This is the first method which is called during the resolving
 601                 // process; we're called immediately after creating the type parameters
 602                 // with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
 603                 // MethodBuilder).
 604                 //
 605                 public void Create (TypeSpec declaringType, TypeContainer parent)
 606                 {
 607                         if (builder != null)
 608                                 throw new InternalErrorException ();
 609
 610                         // Needed to get compiler reference
 611                         this.Parent = parent;
 612                         spec.DeclaringType = declaringType;
 613                 }
 614
 615                 public void Define (GenericTypeParameterBuilder type)
 616                 {
 617                         this.builder = type;
 618                         spec.SetMetaInfo (type);
 619                 }
 620
 621                 public void Define (TypeParameter tp)
 622                 {
 623                         builder = tp.builder;
 624                 }
 625
 626                 public void EmitConstraints (GenericTypeParameterBuilder builder)
 627                 {
 628                         var attr = GenericParameterAttributes.None;
 629                         if (spec.Variance == Variance.Contravariant)
 630                                 attr |= GenericParameterAttributes.Contravariant;
 631                         else if (spec.Variance == Variance.Covariant)
 632                                 attr |= GenericParameterAttributes.Covariant;
 633
 634                         if (spec.HasSpecialClass)
 635                                 attr |= GenericParameterAttributes.ReferenceTypeConstraint;
 636                         else if (spec.HasSpecialStruct)
 637                                 attr |= GenericParameterAttributes.NotNullableValueTypeConstraint | GenericParameterAttributes.DefaultConstructorConstraint;
 638
 639                         if (spec.HasSpecialConstructor)
 640                                 attr |= GenericParameterAttributes.DefaultConstructorConstraint;
 641
 642                         if (spec.BaseType.BuiltinType != BuiltinTypeSpec.Type.Object)
 643                                 builder.SetBaseTypeConstraint (spec.BaseType.GetMetaInfo ());
 644
 645                         if (spec.InterfacesDefined != null)
 646                                 builder.SetInterfaceConstraints (spec.InterfacesDefined.Select (l => l.GetMetaInfo ()).ToArray ());
 647
 648                         if (spec.TypeArguments != null) {
 649                                 var meta_constraints = new List<MetaType> (spec.TypeArguments.Length);
 650                                 foreach (var c in spec.TypeArguments) {
 651                                         //
 652                                         // Inflated type parameters can collide with base type constraint, don't
 653                                         // emit any such type parameter.
 654                                         //
 655                                         if (c.IsClass && spec.BaseType.BuiltinType != BuiltinTypeSpec.Type.Object)
 656                                                 continue;
 657
 658                                         meta_constraints.Add (c.GetMetaInfo ());
 659                                 }
 660
 661                                 builder.SetInterfaceConstraints (meta_constraints.ToArray ());
 662                         }
 663
 664                         builder.SetGenericParameterAttributes (attr);
 665                 }
 666
 667                 public override void Emit ()
 668                 {
 669                         EmitConstraints (builder);
 670
 671                         if (OptAttributes != null)
 672                                 OptAttributes.Emit ();
 673
 674                         base.Emit ();
 675                 }
 676
 677                 public void ErrorInvalidVariance (IMemberContext mc, Variance expected)
 678                 {
 679                         Report.SymbolRelatedToPreviousError (mc.CurrentMemberDefinition);
 680                         string input_variance = Variance == Variance.Contravariant ? "contravariant" : "covariant";
 681                         string gtype_variance;
 682                         switch (expected) {
 683                         case Variance.Contravariant: gtype_variance = "contravariantly"; break;
 684                         case Variance.Covariant: gtype_variance = "covariantly"; break;
 685                         default: gtype_variance = "invariantly"; break;
 686                         }
 687
 688                         Delegate d = mc as Delegate;
 689                         string parameters = d != null ? d.Parameters.GetSignatureForError () : "";
 690
 691                         Report.Error (1961, Location,
 692                                 "The {2} type parameter `{0}' must be {3} valid on `{1}{4}'",
 693                                         GetSignatureForError (), mc.GetSignatureForError (), input_variance, gtype_variance, parameters);
 694                 }
 695
 696                 public TypeSpec GetAttributeCoClass ()
 697                 {
 698                         return null;
 699                 }
 700
 701                 public string GetAttributeDefaultMember ()
 702                 {
 703                         throw new NotSupportedException ();
 704                 }
 705
 706                 public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
 707                 {
 708                         throw new NotSupportedException ();
 709                 }
 710
 711                 public override string GetSignatureForDocumentation ()
 712                 {
 713                         throw new NotImplementedException ();
 714                 }
 715
 716                 public override string GetSignatureForError ()
 717                 {
 718                         return MemberName.Name;
 719                 }
 720
 721                 bool ITypeDefinition.IsInternalAsPublic (IAssemblyDefinition assembly)
 722                 {
 723                         return spec.MemberDefinition.DeclaringAssembly == assembly;
 724                 }
 725
 726                 public void LoadMembers (TypeSpec declaringType, bool onlyTypes, ref MemberCache cache)
 727                 {
 728                         throw new NotSupportedException ("Not supported for compiled definition");
 729                 }
 730
 731                 //
 732                 // Resolves all type parameter constraints
 733                 //
 734                 public bool ResolveConstraints (IMemberContext context)
 735                 {
 736                         if (constraints != null)
 737                                 return constraints.Resolve (context, this);
 738
 739                         if (spec.BaseType == null)
 740                                 spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;
 741
 742                         return true;
 743                 }
 744
 745                 public override bool IsClsComplianceRequired ()
 746                 {
 747                         return false;
 748                 }
 749
 750                 public new void VerifyClsCompliance ()
 751                 {
 752                         if (constraints != null)
 753                                 constraints.VerifyClsCompliance (Report);
 754                 }
 755
 756                 public void WarningParentNameConflict (TypeParameter conflict)
 757                 {
 758                         conflict.Report.SymbolRelatedToPreviousError (conflict.Location, null);
 759                         conflict.Report.Warning (693, 3, Location,
 760                                 "Type parameter `{0}' has the same name as the type parameter from outer type `{1}'",
 761                                 GetSignatureForError (), conflict.CurrentType.GetSignatureForError ());
 762                 }
 763         }
 764
 765         [System.Diagnostics.DebuggerDisplay ("{DisplayDebugInfo()}")]
 766         public class TypeParameterSpec : TypeSpec
 767         {
 768                 public static readonly new TypeParameterSpec[] EmptyTypes = new TypeParameterSpec[0];
 769
 770                 Variance variance;
 771                 SpecialConstraint spec;
 772                 int tp_pos;
 773                 TypeSpec[] targs;
 774                 TypeSpec[] ifaces_defined;
 775                 TypeSpec effective_base;
 776                 MemberCache interface_cache;
 777
 778                 //
 779                 // Creates type owned type parameter
 780                 //
 781                 public TypeParameterSpec (TypeSpec declaringType, int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
 782                         : base (MemberKind.TypeParameter, declaringType, definition, info, Modifiers.PUBLIC)
 783                 {
 784                         this.variance = variance;
 785                         this.spec = spec;
 786                         state &= ~StateFlags.Obsolete_Undetected;
 787                         tp_pos = index;
 788                 }
 789
 790                 //
 791                 // Creates method owned type parameter
 792                 //
 793                 public TypeParameterSpec (int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
 794                         : this (null, index, definition, spec, variance, info)
 795                 {
 796                 }
 797
 798                 #region Properties
 799
 800                 public int DeclaredPosition {
 801                         get {
 802                                 return tp_pos;
 803                         }
 804                         set {
 805                                 tp_pos = value;
 806                         }
 807                 }
 808
 809                 public bool HasSpecialConstructor {
 810                         get {
 811                                 return (spec & SpecialConstraint.Constructor) != 0;
 812                         }
 813                 }
 814
 815                 public bool HasSpecialClass {
 816                         get {
 817                                 return (spec & SpecialConstraint.Class) != 0;
 818                         }
 819                 }
 820
 821                 public bool HasSpecialStruct {
 822                         get {
 823                                 return (spec & SpecialConstraint.Struct) != 0;
 824                         }
 825                 }
 826
 827                 public bool HasAnyTypeConstraint {
 828                         get {
 829                                 return (spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0 || ifaces != null || targs != null || HasTypeConstraint;
 830                         }
 831                 }
 832
 833                 public bool HasTypeConstraint {
 834                         get {
 835                                 var bt = BaseType.BuiltinType;
 836                                 return bt != BuiltinTypeSpec.Type.Object && bt != BuiltinTypeSpec.Type.ValueType;
 837                         }
 838                 }
 839
 840                 public override IList<TypeSpec> Interfaces {
 841                         get {
 842                                 if ((state & StateFlags.InterfacesExpanded) == 0) {
 843                                         if (ifaces != null) {
 844                                                 if (ifaces_defined == null)
 845                                                         ifaces_defined = ifaces.ToArray ();
 846
 847                                                 for (int i = 0; i < ifaces_defined.Length; ++i ) {
 848                                                         var iface_type = ifaces_defined[i];
 849                                                         var td = iface_type.MemberDefinition as TypeDefinition;
 850                                                         if (td != null)
 851                                                                 td.DoExpandBaseInterfaces ();
 852
 853                                                         if (iface_type.Interfaces != null) {
 854                                                                 for (int ii = 0; ii < iface_type.Interfaces.Count; ++ii) {
 855                                                                         var ii_iface_type = iface_type.Interfaces [ii];
 856                                                                         AddInterface (ii_iface_type);
 857                                                                 }
 858                                                         }
 859                                                 }
 860                                         } else if (ifaces_defined == null) {
 861                                                 ifaces_defined = ifaces == null ? TypeSpec.EmptyTypes : ifaces.ToArray ();
 862                                         }
 863
 864                                         //
 865                                         // Include all base type interfaces too, see ImportTypeBase for details
 866                                         //
 867                                         if (BaseType != null) {
 868                                                 var td = BaseType.MemberDefinition as TypeDefinition;
 869                                                 if (td != null)
 870                                                         td.DoExpandBaseInterfaces ();
 871
 872                                                 if (BaseType.Interfaces != null) {
 873                                                         foreach (var iface in BaseType.Interfaces) {
 874                                                                 AddInterface (iface);
 875                                                         }
 876                                                 }
 877                                         }
 878
 879                                         state |= StateFlags.InterfacesExpanded;
 880                                 }
 881
 882                                 return ifaces;
 883                         }
 884                 }
 885
 886                 public MemberCache InterfaceCache {
 887                         get {
 888                                 return interface_cache;
 889                         }
 890                 }
 891
 892                 //
 893                 // Unexpanded interfaces list
 894                 //
 895                 public TypeSpec[] InterfacesDefined {
 896                         get {
 897                                 if (ifaces_defined == null) {
 898                                         ifaces_defined = ifaces == null ? TypeSpec.EmptyTypes : ifaces.ToArray ();
 899                                 }
 900
 901                                 return ifaces_defined.Length == 0 ? null : ifaces_defined;
 902                         }
 903                         set {
 904                                 ifaces_defined = value;
 905                                 if (value != null && value.Length != 0)
 906                                         ifaces = new List<TypeSpec> (value);
 907                         }
 908                 }
 909
 910                 public bool IsConstrained {
 911                         get {
 912                                 return spec != SpecialConstraint.None || ifaces != null || targs != null || HasTypeConstraint;
 913                         }
 914                 }
 915
 916                 //
 917                 // Returns whether the type parameter is known to be a reference type
 918                 //
 919                 public new bool IsReferenceType {
 920                         get {
 921                                 if ((spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
 922                                         return (spec & SpecialConstraint.Class) != 0;
 923
 924                                 //
 925                                 // Full check is needed (see IsValueType for details)
 926                                 //
 927                                 if (HasTypeConstraint && TypeSpec.IsReferenceType (BaseType))
 928                                         return true;
 929
 930                                 if (targs != null) {
 931                                         foreach (var ta in targs) {
 932                                                 //
 933                                                 // Secondary special constraints are ignored (I am not sure why)
 934                                                 //
 935                                                 var tp = ta as TypeParameterSpec;
 936                                                 if (tp != null && (tp.spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
 937                                                         continue;
 938
 939                                                 if (TypeSpec.IsReferenceType (ta))
 940                                                         return true;
 941                                         }
 942                                 }
 943
 944                                 return false;
 945                         }
 946                 }
 947
 948                 //
 949                 // Returns whether the type parameter is known to be a value type
 950                 //
 951                 public new bool IsValueType {
 952                         get {
 953                                 //
 954                                 // Even if structs/enums cannot be used directly as constraints
 955                                 // they can apear as constraint type when inheriting base constraint
 956                                 // which has dependant type parameter constraint which has been
 957                                 // inflated using value type
 958                                 //
 959                                 // class A : B<int> { override void Foo<U> () {} }
 960                                 // class B<T> { virtual void Foo<U> () where U : T {} }
 961                                 //
 962                                 if (HasSpecialStruct)
 963                                         return true;
 964
 965                                 if (targs != null) {
 966                                         foreach (var ta in targs) {
 967                                                 if (TypeSpec.IsValueType (ta))
 968                                                         return true;
 969                                         }
 970                                 }
 971
 972                                 return false;
 973                         }
 974                 }
 975
 976                 public override string Name {
 977                         get {
 978                                 return definition.Name;
 979                         }
 980                 }
 981
 982                 public bool IsMethodOwned {
 983                         get {
 984                                 return DeclaringType == null;
 985                         }
 986                 }
 987
 988                 public SpecialConstraint SpecialConstraint {
 989                         get {
 990                                 return spec;
 991                         }
 992                         set {
 993                                 spec = value;
 994                         }
 995                 }
 996
 997                 //
 998                 // Types used to inflate the generic type
 999                 //
1000                 public new TypeSpec[] TypeArguments {
1001                         get {
1002                                 return targs;
1003                         }
1004                         set {
1005                                 targs = value;
1006                         }
1007                 }
1008
1009                 public Variance Variance {
1010                         get {
1011                                 return variance;
1012                         }
1013                 }
1014
1015                 #endregion
1016
1017                 public string DisplayDebugInfo ()
1018                 {
1019                         var s = GetSignatureForError ();
1020                         return IsMethodOwned ? s + "!!" : s + "!";
1021                 }
1022
1023                 //
1024                 // Finds effective base class. The effective base class is always a class-type
1025                 //
1026                 public TypeSpec GetEffectiveBase ()
1027                 {
1028                         if (HasSpecialStruct)
1029                                 return BaseType;
1030
1031                         //
1032                         // If T has a class-type constraint C but no type-parameter constraints, its effective base class is C
1033                         //
1034                         if (BaseType != null && targs == null) {
1035                                 //
1036                                 // 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.
1037                                 //
1038                                 // LAMESPEC: Is System.ValueType always the most specific base type in this case?
1039                                 //
1040                                 // Note: This can never happen in an explicitly given constraint, but may occur when the constraints of a generic method
1041                                 // are implicitly inherited by an overriding method declaration or an explicit implementation of an interface method.
1042                                 //
1043                                 return BaseType.IsStruct ? BaseType.BaseType : BaseType;
1044                         }
1045
1046                         if (effective_base != null)
1047                                 return effective_base;
1048
1049                         var types = new TypeSpec [HasTypeConstraint ? targs.Length + 1 : targs.Length];
1050
1051                         for (int i = 0; i < targs.Length; ++i) {
1052                                 var t = targs [i];
1053
1054                                 // Same issue as above, inherited constraints can be of struct type
1055                                 if (t.IsStruct) {
1056                                         types [i] = t.BaseType;
1057                                         continue;
1058                                 }
1059
1060                                 var tps = t as TypeParameterSpec;
1061                                 types [i] = tps != null ? tps.GetEffectiveBase () : t;
1062                         }
1063
1064                         if (HasTypeConstraint)
1065                                 types [types.Length - 1] = BaseType;
1066
1067                         return effective_base = Convert.FindMostEncompassedType (types);
1068                 }
1069
1070                 public override string GetSignatureForDocumentation (bool explicitName)
1071                 {
1072                         if (explicitName)
1073                                 return Name;
1074
1075                         var prefix = IsMethodOwned ? "``" : "`";
1076                         return prefix + DeclaredPosition;
1077                 }
1078
1079                 public override string GetSignatureForError ()
1080                 {
1081                         return Name;
1082                 }
1083
1084                 //
1085                 // Constraints have to match by definition but not position, used by
1086                 // partial classes or methods
1087                 //
1088                 public bool HasSameConstraintsDefinition (TypeParameterSpec other)
1089                 {
1090                         if (spec != other.spec)
1091                                 return false;
1092
1093                         if (BaseType != other.BaseType)
1094                                 return false;
1095
1096                         if (!TypeSpecComparer.Override.IsSame (InterfacesDefined, other.InterfacesDefined))
1097                                 return false;
1098
1099                         if (!TypeSpecComparer.Override.IsSame (targs, other.targs))
1100                                 return false;
1101
1102                         return true;
1103                 }
1104
1105                 //
1106                 // Constraints have to match by using same set of types, used by
1107                 // implicit interface implementation
1108                 //
1109                 public bool HasSameConstraintsImplementation (TypeParameterSpec other)
1110                 {
1111                         if (spec != other.spec)
1112                                 return false;
1113
1114                         //
1115                         // It can be same base type or inflated type parameter
1116                         //
1117                         // interface I<T> { void Foo<U> where U : T; }
1118                         // class A : I<int> { void Foo<X> where X : int {} }
1119                         //
1120                         bool found;
1121                         if (!TypeSpecComparer.Override.IsEqual (BaseType, other.BaseType)) {
1122                                 found = false;
1123                                 if (other.targs != null) {
1124                                         foreach (var otarg in other.targs) {
1125                                                 if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
1126                                                         found = true;
1127                                                         break;
1128                                                 }
1129                                         }
1130                                 } else if (targs != null) {
1131                                         foreach (var targ in targs) {
1132                                                 if (TypeSpecComparer.Override.IsEqual (targ, other.BaseType)) {
1133                                                         found = true;
1134                                                         break;
1135                                                 }
1136                                         }
1137                                 }
1138
1139                                 if (!found)
1140                                         return false;
1141                         }
1142
1143                         // Check interfaces implementation -> definition
1144                         if (InterfacesDefined != null) {
1145                                 //
1146                                 // Iterate over inflated interfaces
1147                                 //
1148                                 foreach (var iface in InterfacesDefined) {
1149                                         found = false;
1150                                         if (other.InterfacesDefined != null) {
1151                                                 foreach (var oiface in other.Interfaces) {
1152                                                         if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
1153                                                                 found = true;
1154                                                                 break;
1155                                                         }
1156                                                 }
1157                                         }
1158
1159                                         if (found)
1160                                                 continue;
1161
1162                                         if (other.targs != null) {
1163                                                 foreach (var otarg in other.targs) {
1164                                                         if (TypeSpecComparer.Override.IsEqual (iface, otarg)) {
1165                                                                 found = true;
1166                                                                 break;
1167                                                         }
1168                                                 }
1169                                         }
1170
1171                                         if (!found)
1172                                                 return false;
1173                                 }
1174                         }
1175
1176                         // Check interfaces implementation <- definition
1177                         if (other.InterfacesDefined != null) {
1178                                 //
1179                                 // Iterate over inflated interfaces
1180                                 //
1181                                 foreach (var oiface in other.InterfacesDefined) {
1182                                         found = false;
1183
1184                                         if (InterfacesDefined != null) {
1185                                                 foreach (var iface in Interfaces) {
1186                                                         if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
1187                                                                 found = true;
1188                                                                 break;
1189                                                         }
1190                                                 }
1191                                         } else if (targs != null) {
1192                                                 foreach (var targ in targs) {
1193                                                         if (TypeSpecComparer.Override.IsEqual (targ, oiface)) {
1194                                                                 found = true;
1195                                                                 break;
1196                                                         }
1197                                                 }
1198                                         }
1199
1200                                         if (!found)
1201                                                 return false;
1202                                 }
1203                         }
1204
1205                         // Check type parameters implementation -> definition
1206                         if (targs != null) {
1207                                 foreach (var targ in targs) {
1208                                         found = false;
1209
1210                                         if (other.targs != null) {
1211                                                 foreach (var otarg in other.targs) {
1212                                                         if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
1213                                                                 found = true;
1214                                                                 break;
1215                                                         }
1216                                                 }
1217                                         }
1218
1219                                         if (other.InterfacesDefined != null && !found) {
1220                                                 foreach (var iface in other.Interfaces) {
1221                                                         if (TypeSpecComparer.Override.IsEqual (iface, targ)) {
1222                                                                 found = true;
1223                                                                 break;
1224                                                         }
1225                                                 }
1226                                         }
1227
1228                                         if (!found)
1229                                                 found = TypeSpecComparer.Override.IsEqual (targ, other.BaseType);
1230
1231                                         if (!found)
1232                                                 return false;
1233                                 }
1234                         }
1235
1236                         // Check type parameters implementation <- definition
1237                         if (other.targs != null) {
1238                                 foreach (var otarg in other.targs) {
1239                                         // Ignore inflated type arguments, were checked above
1240                                         if (!otarg.IsGenericParameter)
1241                                                 continue;
1242
1243                                         if (targs == null)
1244                                                 return false;
1245
1246                                         found = false;
1247                                         foreach (var targ in targs) {
1248                                                 if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
1249                                                         found = true;
1250                                                         break;
1251                                                 }
1252                                         }
1253
1254                                         if (!found)
1255                                                 return false;
1256                                 }
1257                         }
1258
1259                         return true;
1260                 }
1261
1262                 public static TypeParameterSpec[] InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec[] tparams)
1263                 {
1264                         return InflateConstraints (tparams, l => l, inflator);
1265                 }
1266
1267                 public static TypeParameterSpec[] InflateConstraints<T> (TypeParameterSpec[] tparams, Func<T, TypeParameterInflator> inflatorFactory, T arg)
1268                 {
1269                         TypeParameterSpec[] constraints = null;
1270                         TypeParameterInflator? inflator = null;
1271
1272                         for (int i = 0; i < tparams.Length; ++i) {
1273                                 var tp = tparams[i];
1274                                 if (tp.HasTypeConstraint || tp.InterfacesDefined != null || tp.TypeArguments != null) {
1275                                         if (constraints == null) {
1276                                                 constraints = new TypeParameterSpec[tparams.Length];
1277                                                 Array.Copy (tparams, constraints, constraints.Length);
1278                                         }
1279
1280                                         //
1281                                         // Using a factory to avoid possibly expensive inflator build up
1282                                         //
1283                                         if (inflator == null)
1284                                                 inflator = inflatorFactory (arg);
1285
1286                                         constraints[i] = (TypeParameterSpec) constraints[i].InflateMember (inflator.Value);
1287                                 }
1288                         }
1289
1290                         if (constraints == null)
1291                                 constraints = tparams;
1292
1293                         return constraints;
1294                 }
1295
1296                 public void InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec tps)
1297                 {
1298                         tps.BaseType = inflator.Inflate (BaseType);
1299
1300                         var defined = InterfacesDefined;
1301                         if (defined != null) {
1302                                 tps.ifaces_defined = new TypeSpec[defined.Length];
1303                                 for (int i = 0; i < defined.Length; ++i)
1304                                         tps.ifaces_defined [i] = inflator.Inflate (defined[i]);
1305                         } else if (ifaces_defined == TypeSpec.EmptyTypes) {
1306                                 tps.ifaces_defined = TypeSpec.EmptyTypes;
1307                         }
1308
1309                         var ifaces = Interfaces;
1310                         if (ifaces != null) {
1311                                 tps.ifaces = new List<TypeSpec> (ifaces.Count);
1312                                 for (int i = 0; i < ifaces.Count; ++i)
1313                                         tps.ifaces.Add (inflator.Inflate (ifaces[i]));
1314                                 tps.state |= StateFlags.InterfacesExpanded;
1315                         }
1316
1317                         if (targs != null) {
1318                                 tps.targs = new TypeSpec[targs.Length];
1319                                 for (int i = 0; i < targs.Length; ++i)
1320                                         tps.targs[i] = inflator.Inflate (targs[i]);
1321                         }
1322                 }
1323
1324                 public override MemberSpec InflateMember (TypeParameterInflator inflator)
1325                 {
1326                         var tps = (TypeParameterSpec) MemberwiseClone ();
1327 #if DEBUG
1328                         tps.ID += 1000000;
1329 #endif
1330
1331                         InflateConstraints (inflator, tps);
1332                         return tps;
1333                 }
1334
1335                 //
1336                 // Populates type parameter members using type parameter constraints
1337                 // The trick here is to be called late enough but not too late to
1338                 // populate member cache with all members from other types
1339                 //
1340                 protected override void InitializeMemberCache (bool onlyTypes)
1341                 {
1342                         cache = new MemberCache ();
1343
1344                         if (targs != null) {
1345                                 foreach (var ta in targs) {
1346                                         var tps = ta as TypeParameterSpec;
1347                                         var b_type = tps == null ? ta : tps.GetEffectiveBase ();
1348
1349                                         //
1350                                         // Find the most specific type when base type was inflated from base constraints
1351                                         //
1352                                         if (b_type != null && !b_type.IsStructOrEnum && TypeSpec.IsBaseClass (b_type, BaseType, false))
1353                                                 BaseType = b_type;
1354                                 }
1355                         }
1356
1357                         //
1358                         // For a type parameter the membercache is the union of the sets of members of the types
1359                         // specified as a primary constraint or secondary constraint
1360                         //
1361                         bool has_user_base_type = false;
1362                         if (BaseType.BuiltinType != BuiltinTypeSpec.Type.Object && BaseType.BuiltinType != BuiltinTypeSpec.Type.ValueType) {
1363                                 cache.AddBaseType (BaseType);
1364                                 has_user_base_type = true;
1365                         }
1366
1367                         if (InterfacesDefined != null) {
1368                                 var icache = cache;
1369                                 if (has_user_base_type) {
1370                                         //
1371                                         // type-parameter lookup rules are more complicated that other types lookup rules.
1372                                         // Effective base class and its base types member have priority over interface
1373                                         // constraints which means we cannot lookup interface members before class members
1374                                         // hence we setup secondary cache for such cases.
1375                                         //
1376                                         interface_cache = new MemberCache ();
1377                                         icache = interface_cache;
1378                                 }
1379
1380                                 foreach (var iface_type in InterfacesDefined) {
1381                                         icache.AddInterface (iface_type);
1382                                 }
1383                         }
1384
1385                         //
1386                         // Import interfaces after base type to match behavior from ordinary classes
1387                         //
1388                         if (targs != null) {
1389                                 foreach (var ta in targs) {
1390                                         var tps = ta as TypeParameterSpec;
1391                                         var ifaces = tps == null ? ta.Interfaces : tps.InterfacesDefined;
1392
1393                                         if (ifaces != null) {
1394                                                 var icache = cache;
1395                                                 if (has_user_base_type) {
1396                                                         interface_cache = new MemberCache ();
1397                                                         icache = interface_cache;
1398                                                 }
1399
1400                                                 foreach (var iface_type in ifaces) {
1401                                                         icache.AddInterface (iface_type);
1402                                                 }
1403                                         }
1404                                 }
1405                         }
1406                 }
1407
1408                 public bool IsConvertibleToInterface (TypeSpec iface)
1409                 {
1410                         if (Interfaces != null) {
1411                                 foreach (var t in Interfaces) {
1412                                         if (t == iface)
1413                                                 return true;
1414                                 }
1415                         }
1416
1417                         if (TypeArguments != null) {
1418                                 foreach (var t in TypeArguments) {
1419                                         var tps = t as TypeParameterSpec;
1420                                         if (tps != null) {
1421                                                 if (tps.IsConvertibleToInterface (iface))
1422                                                         return true;
1423
1424                                                 continue;
1425                                         }
1426
1427                                         if (t.ImplementsInterface (iface, false))
1428                                                 return true;
1429                                 }
1430                         }
1431
1432                         return false;
1433                 }
1434
1435                 public static bool HasAnyTypeParameterTypeConstrained (IGenericMethodDefinition md)
1436                 {
1437                         var tps = md.TypeParameters;
1438                         for (int i = 0; i < md.TypeParametersCount; ++i) {
1439                                 if (tps[i].HasAnyTypeConstraint) {
1440                                         return true;
1441                                 }
1442                         }
1443
1444                         return false;
1445                 }
1446
1447                 public static bool HasAnyTypeParameterConstrained (IGenericMethodDefinition md)
1448                 {
1449                         var tps = md.TypeParameters;
1450                         for (int i = 0; i < md.TypeParametersCount; ++i) {
1451                                 if (tps[i].IsConstrained) {
1452                                         return true;
1453                                 }
1454                         }
1455
1456                         return false;
1457                 }
1458
1459                 public bool HasDependencyOn (TypeSpec type)
1460                 {
1461                         if (TypeArguments != null) {
1462                                 foreach (var targ in TypeArguments) {
1463                                         if (TypeSpecComparer.Override.IsEqual (targ, type))
1464                                                 return true;
1465
1466                                         var tps = targ as TypeParameterSpec;
1467                                         if (tps != null && tps.HasDependencyOn (type))
1468                                                 return true;
1469                                 }
1470                         }
1471
1472                         return false;
1473                 }
1474
1475                 public override TypeSpec Mutate (TypeParameterMutator mutator)
1476                 {
1477                         return mutator.Mutate (this);
1478                 }
1479         }
1480
1481         public struct TypeParameterInflator
1482         {
1483                 readonly TypeSpec type;
1484                 readonly TypeParameterSpec[] tparams;
1485                 readonly TypeSpec[] targs;
1486                 readonly IModuleContext context;
1487
1488                 public TypeParameterInflator (TypeParameterInflator nested, TypeSpec type)
1489                         : this (nested.context, type, nested.tparams, nested.targs)
1490                 {
1491                 }
1492
1493                 public TypeParameterInflator (IModuleContext context, TypeSpec type, TypeParameterSpec[] tparams, TypeSpec[] targs)
1494                 {
1495                         if (tparams.Length != targs.Length)
1496                                 throw new ArgumentException ("Invalid arguments");
1497
1498                         this.context = context;
1499                         this.tparams = tparams;
1500                         this.targs = targs;
1501                         this.type = type;
1502                 }
1503
1504                 #region Properties
1505
1506                 public IModuleContext Context {
1507                         get {
1508                                 return context;
1509                         }
1510                 }
1511
1512                 public TypeSpec TypeInstance {
1513                         get {
1514                                 return type;
1515                         }
1516                 }
1517
1518                 //
1519                 // Type parameters to inflate
1520                 //
1521                 public TypeParameterSpec[] TypeParameters {
1522                         get {
1523                                 return tparams;
1524                         }
1525                 }
1526
1527                 #endregion
1528
1529                 public TypeSpec Inflate (TypeSpec type)
1530                 {
1531                         var tp = type as TypeParameterSpec;
1532                         if (tp != null)
1533                                 return Inflate (tp);
1534
1535                         var ec = type as ElementTypeSpec;
1536                         if (ec != null) {
1537                                 var et = Inflate (ec.Element);
1538                                 if (et != ec.Element) {
1539                                         var ac = ec as ArrayContainer;
1540                                         if (ac != null)
1541                                                 return ArrayContainer.MakeType (context.Module, et, ac.Rank);
1542
1543                                         if (ec is PointerContainer)
1544                                                 return PointerContainer.MakeType (context.Module, et);
1545
1546                                         throw new NotImplementedException ();
1547                                 }
1548
1549                                 return ec;
1550                         }
1551
1552                         if (type.Kind == MemberKind.MissingType)
1553                                 return type;
1554
1555                         //
1556                         // When inflating a nested type, inflate its parent first
1557                         // in case it's using same type parameters (was inflated within the type)
1558                         //
1559                         TypeSpec[] targs;
1560                         int i = 0;
1561                         if (type.IsNested) {
1562                                 var parent = Inflate (type.DeclaringType);
1563
1564                                 //
1565                                 // Keep the inflated type arguments
1566                                 //
1567                                 targs = type.TypeArguments;
1568
1569                                 //
1570                                 // When inflating imported nested type used inside same declaring type, we get TypeSpec
1571                                 // because the import cache helps us to catch it. However, that means we have to look at
1572                                 // type definition to get type argument (they are in fact type parameter in this case)
1573                                 //
1574                                 if (targs.Length == 0 && type.Arity > 0)
1575                                         targs = type.MemberDefinition.TypeParameters;
1576
1577                                 //
1578                                 // Parent was inflated, find the same type on inflated type
1579                                 // to use same cache for nested types on same generic parent
1580                                 //
1581                                 type = MemberCache.FindNestedType (parent, type.Name, type.Arity, false);
1582
1583                                 //
1584                                 // Handle the tricky case where parent shares local type arguments
1585                                 // which means inflating inflated type
1586                                 //
1587                                 // class Test<T> {
1588                                 //              public static Nested<T> Foo () { return null; }
1589                                 //
1590                                 //              public class Nested<U> {}
1591                                 //      }
1592                                 //
1593                                 //  return type of Test<string>.Foo() has to be Test<string>.Nested<string>
1594                                 //
1595                                 if (targs.Length > 0) {
1596                                         var inflated_targs = new TypeSpec[targs.Length];
1597                                         for (; i < targs.Length; ++i)
1598                                                 inflated_targs[i] = Inflate (targs[i]);
1599
1600                                         type = type.MakeGenericType (context, inflated_targs);
1601                                 }
1602
1603                                 return type;
1604                         }
1605
1606                         // Nothing to do for non-generic type
1607                         if (type.Arity == 0)
1608                                 return type;
1609
1610                         targs = new TypeSpec[type.Arity];
1611
1612                         //
1613                         // Inflating using outside type arguments, var v = new Foo<int> (), class Foo<T> {}
1614                         //
1615                         if (type is InflatedTypeSpec) {
1616                                 for (; i < targs.Length; ++i)
1617                                         targs[i] = Inflate (type.TypeArguments[i]);
1618
1619                                 type = type.GetDefinition ();
1620                         } else {
1621                                 //
1622                                 // Inflating parent using inside type arguments, class Foo<T> { ITest<T> foo; }
1623                                 //
1624                                 var args = type.MemberDefinition.TypeParameters;
1625                                 foreach (var ds_tp in args)
1626                                         targs[i++] = Inflate (ds_tp);
1627                         }
1628
1629                         return type.MakeGenericType (context, targs);
1630                 }
1631
1632                 public TypeSpec Inflate (TypeParameterSpec tp)
1633                 {
1634                         for (int i = 0; i < tparams.Length; ++i)
1635                                 if (tparams [i] == tp)
1636                                         return targs[i];
1637
1638                         // This can happen when inflating nested types
1639                         // without type arguments specified
1640                         return tp;
1641                 }
1642         }
1643
1644         //
1645         // Before emitting any code we have to change all MVAR references to VAR
1646         // when the method is of generic type and has hoisted variables
1647         //
1648         public class TypeParameterMutator
1649         {
1650                 readonly TypeParameters mvar;
1651                 readonly TypeParameters var;
1652                 readonly TypeParameterSpec[] src;
1653                 Dictionary<TypeSpec, TypeSpec> mutated_typespec;
1654
1655                 public TypeParameterMutator (TypeParameters mvar, TypeParameters var)
1656                 {
1657                         if (mvar.Count != var.Count)
1658                                 throw new ArgumentException ();
1659
1660                         this.mvar = mvar;
1661                         this.var = var;
1662                 }
1663
1664                 public TypeParameterMutator (TypeParameterSpec[] srcVar, TypeParameters destVar)
1665                 {
1666                         if (srcVar.Length != destVar.Count)
1667                                 throw new ArgumentException ();
1668
1669                         this.src = srcVar;
1670                         this.var = destVar;
1671                 }
1672
1673                 #region Properties
1674
1675                 public TypeParameters MethodTypeParameters {
1676                         get {
1677                                 return mvar;
1678                         }
1679                 }
1680
1681                 #endregion
1682
1683                 public static TypeSpec GetMemberDeclaringType (TypeSpec type)
1684                 {
1685                         if (type is InflatedTypeSpec) {
1686                                 if (type.DeclaringType == null)
1687                                         return type.GetDefinition ();
1688
1689                                 var parent = GetMemberDeclaringType (type.DeclaringType);
1690                                 type = MemberCache.GetMember<TypeSpec> (parent, type);
1691                         }
1692
1693                         return type;
1694                 }
1695
1696                 public TypeSpec Mutate (TypeSpec ts)
1697                 {
1698                         TypeSpec value;
1699                         if (mutated_typespec != null && mutated_typespec.TryGetValue (ts, out value))
1700                                 return value;
1701
1702                         value = ts.Mutate (this);
1703                         if (mutated_typespec == null)
1704                                 mutated_typespec = new Dictionary<TypeSpec, TypeSpec> ();
1705
1706                         mutated_typespec.Add (ts, value);
1707                         return value;
1708                 }
1709
1710                 public TypeParameterSpec Mutate (TypeParameterSpec tp)
1711                 {
1712                         if (mvar != null) {
1713                                 for (int i = 0; i < mvar.Count; ++i) {
1714                                         if (mvar[i].Type == tp)
1715                                                 return var[i].Type;
1716                                 }
1717                         } else {
1718                                 for (int i = 0; i < src.Length; ++i) {
1719                                         if (src[i] == tp)
1720                                                 return var[i].Type;
1721                                 }
1722                         }
1723
1724                         return tp;
1725                 }
1726
1727                 public TypeSpec[] Mutate (TypeSpec[] targs)
1728                 {
1729                         TypeSpec[] mutated = new TypeSpec[targs.Length];
1730                         bool changed = false;
1731                         for (int i = 0; i < targs.Length; ++i) {
1732                                 mutated[i] = Mutate (targs[i]);
1733                                 changed |= targs[i] != mutated[i];
1734                         }
1735
1736                         return changed ? mutated : targs;
1737                 }
1738         }
1739
1740         /// <summary>
1741         ///   A TypeExpr which already resolved to a type parameter.
1742         /// </summary>
1743         public class TypeParameterExpr : TypeExpression
1744         {
1745                 public TypeParameterExpr (TypeParameter type_parameter, Location loc)
1746                         : base (type_parameter.Type, loc)
1747                 {
1748                         this.eclass = ExprClass.TypeParameter;
1749                 }
1750         }
1751
1752         public class InflatedTypeSpec : TypeSpec
1753         {
1754                 TypeSpec[] targs;
1755                 TypeParameterSpec[] constraints;
1756                 readonly TypeSpec open_type;
1757                 readonly IModuleContext context;
1758
1759                 public InflatedTypeSpec (IModuleContext context, TypeSpec openType, TypeSpec declaringType, TypeSpec[] targs)
1760                         : base (openType.Kind, declaringType, openType.MemberDefinition, null, openType.Modifiers)
1761                 {
1762                         if (targs == null)
1763                                 throw new ArgumentNullException ("targs");
1764
1765                         this.state &= ~SharedStateFlags;
1766                         this.state |= (openType.state & SharedStateFlags);
1767
1768                         this.context = context;
1769                         this.open_type = openType;
1770                         this.targs = targs;
1771
1772                         foreach (var arg in targs) {
1773                                 if (arg.HasDynamicElement || arg.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
1774                                         state |= StateFlags.HasDynamicElement;
1775                                         break;
1776                                 }
1777                         }
1778
1779                         if (open_type.Kind == MemberKind.MissingType)
1780                                 MemberCache = MemberCache.Empty;
1781
1782                         if ((open_type.Modifiers & Modifiers.COMPILER_GENERATED) != 0)
1783                                 state |= StateFlags.ConstraintsChecked;
1784                 }
1785
1786                 #region Properties
1787
1788                 public override TypeSpec BaseType {
1789                         get {
1790                                 if (cache == null || (state & StateFlags.PendingBaseTypeInflate) != 0)
1791                                         InitializeMemberCache (true);
1792
1793                                 return base.BaseType;
1794                         }
1795                 }
1796
1797                 //
1798                 // Inflated type parameters with constraints array, mapping with type arguments is based on index
1799                 //
1800                 public TypeParameterSpec[] Constraints {
1801                         get {
1802                                 if (constraints == null) {
1803                                         constraints = TypeParameterSpec.InflateConstraints (MemberDefinition.TypeParameters, l => l.CreateLocalInflator (context), this);
1804                                 }
1805
1806                                 return constraints;
1807                         }
1808                 }
1809
1810                 //
1811                 // Used to cache expensive constraints validation on constructed types
1812                 //
1813                 public bool HasConstraintsChecked {
1814                         get {
1815                                 return (state & StateFlags.ConstraintsChecked) != 0;
1816                         }
1817                         set {
1818                                 state = value ? state | StateFlags.ConstraintsChecked : state & ~StateFlags.ConstraintsChecked;
1819                         }
1820                 }
1821
1822                 public override IList<TypeSpec> Interfaces {
1823                         get {
1824                                 if (cache == null)
1825                                         InitializeMemberCache (true);
1826
1827                                 return base.Interfaces;
1828                         }
1829                 }
1830
1831                 public override bool IsExpressionTreeType {
1832                         get {
1833                                 return (open_type.state & StateFlags.InflatedExpressionType) != 0;
1834                         }
1835                 }
1836
1837                 public override bool IsArrayGenericInterface {
1838                         get {
1839                                 return (open_type.state & StateFlags.GenericIterateInterface) != 0;
1840                         }
1841                 }
1842
1843                 public override bool IsGenericTask {
1844                         get {
1845                                 return (open_type.state & StateFlags.GenericTask) != 0;
1846                         }
1847                 }
1848
1849                 public override bool IsNullableType {
1850                         get {
1851                                 return (open_type.state & StateFlags.InflatedNullableType) != 0;
1852                         }
1853                 }
1854
1855                 //
1856                 // Types used to inflate the generic  type
1857                 //
1858                 public override TypeSpec[] TypeArguments {
1859                         get {
1860                                 return targs;
1861                         }
1862                 }
1863
1864                 #endregion
1865
1866                 public override bool AddInterface (TypeSpec iface)
1867                 {
1868                         var inflator = CreateLocalInflator (context);
1869                         iface = inflator.Inflate (iface);
1870                         if (iface == null)
1871                                 return false;
1872
1873                         return base.AddInterface (iface);
1874                 }
1875
1876                 public static bool ContainsTypeParameter (TypeSpec type)
1877                 {
1878                         if (type.Kind == MemberKind.TypeParameter)
1879                                 return true;
1880
1881                         var element_container = type as ElementTypeSpec;
1882                         if (element_container != null)
1883                                 return ContainsTypeParameter (element_container.Element);
1884
1885                         foreach (var t in type.TypeArguments) {
1886                                 if (ContainsTypeParameter (t)) {
1887                                         return true;
1888                                 }
1889                         }
1890
1891                         return false;
1892                 }
1893
1894                 public TypeParameterInflator CreateLocalInflator (IModuleContext context)
1895                 {
1896                         TypeParameterSpec[] tparams_full;
1897                         TypeSpec[] targs_full = targs;
1898                         if (IsNested) {
1899                                 //
1900                                 // Special case is needed when we are inflating an open type (nested type definition)
1901                                 // on inflated parent. Consider following case
1902                                 //
1903                                 // Foo<T>.Bar<U> => Foo<string>.Bar<U>
1904                                 //
1905                                 // Any later inflation of Foo<string>.Bar<U> has to also inflate T if used inside Bar<U>
1906                                 //
1907                                 List<TypeSpec> merged_targs = null;
1908                                 List<TypeParameterSpec> merged_tparams = null;
1909
1910                                 var type = DeclaringType;
1911
1912                                 do {
1913                                         if (type.TypeArguments.Length > 0) {
1914                                                 if (merged_targs == null) {
1915                                                         merged_targs = new List<TypeSpec> ();
1916                                                         merged_tparams = new List<TypeParameterSpec> ();
1917                                                         if (targs.Length > 0) {
1918                                                                 merged_targs.AddRange (targs);
1919                                                                 merged_tparams.AddRange (open_type.MemberDefinition.TypeParameters);
1920                                                         }
1921                                                 }
1922                                                 merged_tparams.AddRange (type.MemberDefinition.TypeParameters);
1923                                                 merged_targs.AddRange (type.TypeArguments);
1924                                         }
1925                                         type = type.DeclaringType;
1926                                 } while (type != null);
1927
1928                                 if (merged_targs != null) {
1929                                         // Type arguments are not in the right order but it should not matter in this case
1930                                         targs_full = merged_targs.ToArray ();
1931                                         tparams_full = merged_tparams.ToArray ();
1932                                 } else if (targs.Length == 0) {
1933                                         tparams_full = TypeParameterSpec.EmptyTypes;
1934                                 } else {
1935                                         tparams_full = open_type.MemberDefinition.TypeParameters;
1936                                 }
1937                         } else if (targs.Length == 0) {
1938                                 tparams_full = TypeParameterSpec.EmptyTypes;
1939                         } else {
1940                                 tparams_full = open_type.MemberDefinition.TypeParameters;
1941                         }
1942
1943                         return new TypeParameterInflator (context, this, tparams_full, targs_full);
1944                 }
1945
1946                 MetaType CreateMetaInfo ()
1947                 {
1948                         //
1949                         // Converts nested type arguments into right order
1950                         // Foo<string, bool>.Bar<int> => string, bool, int
1951                         //
1952                         var all = new List<MetaType> ();
1953                         TypeSpec type = this;
1954                         TypeSpec definition = type;
1955                         do {
1956                                 if (type.GetDefinition().IsGeneric) {
1957                                         all.InsertRange (0,
1958                                                 type.TypeArguments != TypeSpec.EmptyTypes ?
1959                                                 type.TypeArguments.Select (l => l.GetMetaInfo ()) :
1960                                                 type.MemberDefinition.TypeParameters.Select (l => l.GetMetaInfo ()));
1961                                 }
1962
1963                                 definition = definition.GetDefinition ();
1964                                 type = type.DeclaringType;
1965                         } while (type != null);
1966
1967                         return definition.GetMetaInfo ().MakeGenericType (all.ToArray ());
1968                 }
1969
1970                 public override void CheckObsoleteness (IMemberContext mc, Location loc)
1971                 {
1972                         base.CheckObsoleteness (mc, loc);
1973
1974                         foreach (var ta in TypeArguments)
1975                                 ta.CheckObsoleteness (mc, loc);
1976                 }
1977
1978                 public override ObsoleteAttribute GetAttributeObsolete ()
1979                 {
1980                         return open_type.GetAttributeObsolete ();
1981                 }
1982
1983                 protected override bool IsNotCLSCompliant (out bool attrValue)
1984                 {
1985                         if (base.IsNotCLSCompliant (out attrValue))
1986                                 return true;
1987
1988                         foreach (var ta in TypeArguments) {
1989                                 if (ta.MemberDefinition.CLSAttributeValue == false)
1990                                         return true;
1991                         }
1992
1993                         return false;
1994                 }
1995
1996                 public override TypeSpec GetDefinition ()
1997                 {
1998                         return open_type;
1999                 }
2000
2001                 public override MetaType GetMetaInfo ()
2002                 {
2003                         if (info == null)
2004                                 info = CreateMetaInfo ();
2005
2006                         return info;
2007                 }
2008
2009                 public override string GetSignatureForError ()
2010                 {
2011                         if (IsNullableType)
2012                                 return targs[0].GetSignatureForError () + "?";
2013
2014                         return base.GetSignatureForError ();
2015                 }
2016
2017                 protected override string GetTypeNameSignature ()
2018                 {
2019                         if (targs.Length == 0 || MemberDefinition is AnonymousTypeClass)
2020                                 return null;
2021
2022                         return "<" + TypeManager.CSharpName (targs) + ">";
2023                 }
2024
2025                 public bool HasDynamicArgument ()
2026                 {
2027                         for (int i = 0; i < targs.Length; ++i) {
2028                                 var item = targs[i];
2029
2030                                 if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2031                                         return true;
2032
2033                                 if (item is InflatedTypeSpec) {
2034                                         if (((InflatedTypeSpec) item).HasDynamicArgument ())
2035                                                 return true;
2036
2037                                         continue;
2038                                 }
2039
2040                                 if (item.IsArray) {
2041                                         while (item.IsArray) {
2042                                                 item = ((ArrayContainer) item).Element;
2043                                         }
2044
2045                                         if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2046                                                 return true;
2047                                 }
2048                         }
2049
2050                         return false;
2051                 }
2052
2053                 protected override void InitializeMemberCache (bool onlyTypes)
2054                 {
2055                         if (cache == null) {
2056                                 var open_cache = onlyTypes ? open_type.MemberCacheTypes : open_type.MemberCache;
2057
2058                                 // Surprisingly, calling MemberCache on open type could meantime create cache on this type
2059                                 // for imported type parameter constraints referencing nested type of this declaration
2060                                 if (cache == null)
2061                                         cache = new MemberCache (open_cache);
2062                         }
2063
2064                         var inflator = CreateLocalInflator (context);
2065
2066                         //
2067                         // Two stage inflate due to possible nested types recursive
2068                         // references
2069                         //
2070                         // class A<T> {
2071                         //    B b;
2072                         //    class B {
2073                         //      T Value;
2074                         //    }
2075                         // }
2076                         //
2077                         // When resolving type of `b' members of `B' cannot be
2078                         // inflated because are not yet available in membercache
2079                         //
2080                         if ((state & StateFlags.PendingMemberCacheMembers) == 0) {
2081                                 open_type.MemberCacheTypes.InflateTypes (cache, inflator);
2082
2083                                 //
2084                                 // Inflate any implemented interfaces
2085                                 //
2086                                 if (open_type.Interfaces != null) {
2087                                         ifaces = new List<TypeSpec> (open_type.Interfaces.Count);
2088                                         foreach (var iface in open_type.Interfaces) {
2089                                                 var iface_inflated = inflator.Inflate (iface);
2090                                                 if (iface_inflated == null)
2091                                                         continue;
2092
2093                                                 base.AddInterface (iface_inflated);
2094                                         }
2095                                 }
2096
2097                                 //
2098                                 // Handles the tricky case of recursive nested base generic type
2099                                 //
2100                                 // class A<T> : Base<A<T>.Nested> {
2101                                 //    class Nested {}
2102                                 // }
2103                                 //
2104                                 // When inflating A<T>. base type is not yet known, secondary
2105                                 // inflation is required (not common case) once base scope
2106                                 // is known
2107                                 //
2108                                 if (open_type.BaseType == null) {
2109                                         if (IsClass)
2110                                                 state |= StateFlags.PendingBaseTypeInflate;
2111                                 } else {
2112                                         BaseType = inflator.Inflate (open_type.BaseType);
2113                                 }
2114                         } else if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2115                                 //
2116                                 // It can happen when resolving base type without being defined
2117                                 // which is not allowed to happen and will always lead to an error
2118                                 //
2119                                 // class B { class N {} }
2120                                 // class A<T> : A<B.N> {}
2121                                 //
2122                                 if (open_type.BaseType == null)
2123                                         return;
2124
2125                                 BaseType = inflator.Inflate (open_type.BaseType);
2126                                 state &= ~StateFlags.PendingBaseTypeInflate;
2127                         }
2128
2129                         if (onlyTypes) {
2130                                 state |= StateFlags.PendingMemberCacheMembers;
2131                                 return;
2132                         }
2133
2134                         var tc = open_type.MemberDefinition as TypeDefinition;
2135                         if (tc != null && !tc.HasMembersDefined) {
2136                                 //
2137                                 // Inflating MemberCache with undefined members
2138                                 //
2139                                 return;
2140                         }
2141
2142                         if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2143                                 BaseType = inflator.Inflate (open_type.BaseType);
2144                                 state &= ~StateFlags.PendingBaseTypeInflate;
2145                         }
2146
2147                         state &= ~StateFlags.PendingMemberCacheMembers;
2148                         open_type.MemberCache.InflateMembers (cache, open_type, inflator);
2149                 }
2150
2151                 public override TypeSpec Mutate (TypeParameterMutator mutator)
2152                 {
2153                         var targs = TypeArguments;
2154                         if (targs != null)
2155                                 targs = mutator.Mutate (targs);
2156
2157                         var decl = DeclaringType;
2158                         if (IsNested && DeclaringType.IsGenericOrParentIsGeneric)
2159                                 decl = mutator.Mutate (decl);
2160
2161                         if (targs == TypeArguments && decl == DeclaringType)
2162                                 return this;
2163
2164                         var mutated = (InflatedTypeSpec) MemberwiseClone ();
2165 #if DEBUG
2166                         mutated.ID += 1000000;
2167 #endif
2168
2169                         if (decl != DeclaringType) {
2170                                 // Gets back MethodInfo in case of metaInfo was inflated
2171                                 //mutated.info = MemberCache.GetMember<TypeSpec> (DeclaringType.GetDefinition (), this).info;
2172
2173                                 mutated.declaringType = decl;
2174                                 mutated.state |= StateFlags.PendingMetaInflate;
2175                         }
2176
2177                         if (targs != null) {
2178                                 mutated.targs = targs;
2179                                 mutated.info = null;
2180                         }
2181
2182                         return mutated;
2183                 }
2184         }
2185
2186
2187         //
2188         // Tracks the type arguments when instantiating a generic type. It's used
2189         // by both type arguments and type parameters
2190         //
2191         public class TypeArguments
2192         {
2193                 List<FullNamedExpression> args;
2194                 TypeSpec[] atypes;
2195
2196                 public TypeArguments (params FullNamedExpression[] types)
2197                 {
2198                         this.args = new List<FullNamedExpression> (types);
2199                 }
2200
2201                 public void Add (FullNamedExpression type)
2202                 {
2203                         args.Add (type);
2204                 }
2205
2206                 /// <summary>
2207                 ///   We may only be used after Resolve() is called and return the fully
2208                 ///   resolved types.
2209                 /// </summary>
2210                 // TODO: Not needed, just return type from resolve
2211                 public TypeSpec[] Arguments {
2212                         get {
2213                                 return atypes;
2214                         }
2215                         set {
2216                                 atypes = value;
2217                         }
2218                 }
2219
2220                 public int Count {
2221                         get {
2222                                 return args.Count;
2223                         }
2224                 }
2225
2226                 public virtual bool IsEmpty {
2227                         get {
2228                                 return false;
2229                         }
2230                 }
2231
2232                 public List<FullNamedExpression> TypeExpressions {
2233                         get {
2234                                 return this.args;
2235                         }
2236                 }
2237
2238                 public string GetSignatureForError()
2239                 {
2240                         StringBuilder sb = new StringBuilder ();
2241                         for (int i = 0; i < Count; ++i) {
2242                                 var expr = args[i];
2243                                 if (expr != null)
2244                                         sb.Append (expr.GetSignatureForError ());
2245
2246                                 if (i + 1 < Count)
2247                                         sb.Append (',');
2248                         }
2249
2250                         return sb.ToString ();
2251                 }
2252
2253                 /// <summary>
2254                 ///   Resolve the type arguments.
2255                 /// </summary>
2256                 public virtual bool Resolve (IMemberContext ec, bool allowUnbound)
2257                 {
2258                         if (atypes != null)
2259                             return true;
2260
2261                         int count = args.Count;
2262                         bool ok = true;
2263
2264                         atypes = new TypeSpec [count];
2265
2266                         var errors = ec.Module.Compiler.Report.Errors;
2267
2268                         for (int i = 0; i < count; i++){
2269                                 var te = args[i].ResolveAsType (ec);
2270                                 if (te == null) {
2271                                         ok = false;
2272                                         continue;
2273                                 }
2274
2275                                 atypes[i] = te;
2276
2277                                 if (te.IsStatic) {
2278                                         ec.Module.Compiler.Report.Error (718, args[i].Location, "`{0}': static classes cannot be used as generic arguments",
2279                                                 te.GetSignatureForError ());
2280                                         ok = false;
2281                                 }
2282
2283                                 if (te.IsPointer || te.IsSpecialRuntimeType) {
2284                                         ec.Module.Compiler.Report.Error (306, args[i].Location,
2285                                                 "The type `{0}' may not be used as a type argument",
2286                                                 te.GetSignatureForError ());
2287                                         ok = false;
2288                                 }
2289                         }
2290
2291                         if (!ok || errors != ec.Module.Compiler.Report.Errors)
2292                                 atypes = null;
2293
2294                         return ok;
2295                 }
2296
2297                 public TypeArguments Clone ()
2298                 {
2299                         TypeArguments copy = new TypeArguments ();
2300                         foreach (var ta in args)
2301                                 copy.args.Add (ta);
2302
2303                         return copy;
2304                 }
2305         }
2306
2307         public class UnboundTypeArguments : TypeArguments
2308         {
2309                 Location loc;
2310
2311                 public UnboundTypeArguments (int arity, Location loc)
2312                         : base (new FullNamedExpression[arity])
2313                 {
2314                         this.loc = loc;
2315                 }
2316
2317                 public override bool IsEmpty {
2318                         get {
2319                                 return true;
2320                         }
2321                 }
2322
2323                 public override bool Resolve (IMemberContext mc, bool allowUnbound)
2324                 {
2325                         if (!allowUnbound) {
2326                                 mc.Module.Compiler.Report.Error (7003, loc, "Unbound generic name is not valid in this context");
2327                         }
2328
2329                         // Nothing to be resolved
2330                         return true;
2331                 }
2332         }
2333
2334         public class TypeParameters
2335         {
2336                 List<TypeParameter> names;
2337                 TypeParameterSpec[] types;
2338
2339                 public TypeParameters ()
2340                 {
2341                         names = new List<TypeParameter> ();
2342                 }
2343
2344                 public TypeParameters (int count)
2345                 {
2346                         names = new List<TypeParameter> (count);
2347                 }
2348
2349                 #region Properties
2350
2351                 public int Count {
2352                         get {
2353                                 return names.Count;
2354                         }
2355                 }
2356
2357                 public TypeParameterSpec[] Types {
2358                         get {
2359                                 return types;
2360                         }
2361                 }
2362
2363                 #endregion
2364
2365                 public void Add (TypeParameter tparam)
2366                 {
2367                         names.Add (tparam);
2368                 }
2369
2370                 public void Add (TypeParameters tparams)
2371                 {
2372                         names.AddRange (tparams.names);
2373                 }
2374
2375                 public void Create (TypeSpec declaringType, int parentOffset, TypeContainer parent)
2376                 {
2377                         types = new TypeParameterSpec[Count];
2378                         for (int i = 0; i < types.Length; ++i) {
2379                                 var tp = names[i];
2380
2381                                 tp.Create (declaringType, parent);
2382                                 types[i] = tp.Type;
2383                                 types[i].DeclaredPosition = i + parentOffset;
2384
2385                                 if (tp.Variance != Variance.None && !(declaringType != null && (declaringType.Kind == MemberKind.Interface || declaringType.Kind == MemberKind.Delegate))) {
2386                                         parent.Compiler.Report.Error (1960, tp.Location, "Variant type parameters can only be used with interfaces and delegates");
2387                                 }
2388                         }
2389                 }
2390
2391                 public void Define (GenericTypeParameterBuilder[] builders)
2392                 {
2393                         for (int i = 0; i < types.Length; ++i) {
2394                                 var tp = names[i];
2395                                 tp.Define (builders [types [i].DeclaredPosition]);
2396                         }
2397                 }
2398
2399                 public TypeParameter this[int index] {
2400                         get {
2401                                 return names [index];
2402                         }
2403                         set {
2404                                 names[index] = value;
2405                         }
2406                 }
2407
2408                 public TypeParameter Find (string name)
2409                 {
2410                         foreach (var tp in names) {
2411                                 if (tp.Name == name)
2412                                         return tp;
2413                         }
2414
2415                         return null;
2416                 }
2417
2418                 public string[] GetAllNames ()
2419                 {
2420                         return names.Select (l => l.Name).ToArray ();
2421                 }
2422
2423                 public string GetSignatureForError ()
2424                 {
2425                         StringBuilder sb = new StringBuilder ();
2426                         for (int i = 0; i < Count; ++i) {
2427                                 if (i > 0)
2428                                         sb.Append (',');
2429
2430                                 var name = names[i];
2431                                 if (name != null)
2432                                         sb.Append (name.GetSignatureForError ());
2433                         }
2434
2435                         return sb.ToString ();
2436                 }
2437
2438
2439                 public void CheckPartialConstraints (Method part)
2440                 {
2441                         var partTypeParameters = part.CurrentTypeParameters;
2442
2443                         for (int i = 0; i < Count; i++) {
2444                                 var tp_a = names[i];
2445                                 var tp_b = partTypeParameters [i];
2446                                 if (tp_a.Constraints == null) {
2447                                         if (tp_b.Constraints == null)
2448                                                 continue;
2449                                 } else if (tp_b.Constraints != null && tp_a.Type.HasSameConstraintsDefinition (tp_b.Type)) {
2450                                         continue;
2451                                 }
2452
2453                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition.Location, "");
2454                                 part.Compiler.Report.Error (761, part.Location,
2455                                         "Partial method declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2456                                         part.GetSignatureForError (), partTypeParameters[i].GetSignatureForError ());
2457                         }
2458                 }
2459
2460                 public void UpdateConstraints (TypeDefinition part)
2461                 {
2462                         var partTypeParameters = part.MemberName.TypeParameters;
2463
2464                         for (int i = 0; i < Count; i++) {
2465                                 var tp = names [i];
2466                                 if (tp.AddPartialConstraints (part, partTypeParameters [i]))
2467                                         continue;
2468
2469                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition);
2470                                 part.Compiler.Report.Error (265, part.Location,
2471                                         "Partial declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2472                                         part.GetSignatureForError (), tp.GetSignatureForError ());
2473                         }
2474                 }
2475
2476                 public void VerifyClsCompliance ()
2477                 {
2478                         foreach (var tp in names) {
2479                                 tp.VerifyClsCompliance ();
2480                         }
2481                 }
2482         }
2483
2484         //
2485         // A type expression of generic type with type arguments
2486         //
2487         class GenericTypeExpr : TypeExpr
2488         {
2489                 TypeArguments args;
2490                 TypeSpec open_type;
2491
2492                 /// <summary>
2493                 ///   Instantiate the generic type `t' with the type arguments `args'.
2494                 ///   Use this constructor if you already know the fully resolved
2495                 ///   generic type.
2496                 /// </summary>
2497                 public GenericTypeExpr (TypeSpec open_type, TypeArguments args, Location l)
2498                 {
2499                         this.open_type = open_type;
2500                         loc = l;
2501                         this.args = args;
2502                 }
2503
2504                 public override string GetSignatureForError ()
2505                 {
2506                         return type.GetSignatureForError ();
2507                 }
2508
2509                 public override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
2510                 {
2511                         if (eclass != ExprClass.Unresolved)
2512                                 return type;
2513
2514                         if (!args.Resolve (mc, allowUnboundTypeArguments))
2515                                 return null;
2516
2517                         TypeSpec[] atypes = args.Arguments;
2518                         if (atypes == null)
2519                                 return null;
2520
2521                         //
2522                         // Now bind the parameters
2523                         //
2524                         var inflated = open_type.MakeGenericType (mc, atypes);
2525                         type = inflated;
2526                         eclass = ExprClass.Type;
2527
2528                         //
2529                         // The constraints can be checked only when full type hierarchy is known
2530                         //
2531                         if (!inflated.HasConstraintsChecked && mc.Module.HasTypesFullyDefined) {
2532                                 var constraints = inflated.Constraints;
2533                                 if (constraints != null) {
2534                                         var cc = new ConstraintChecker (mc);
2535                                         if (cc.CheckAll (open_type, atypes, constraints, loc)) {
2536                                                 inflated.HasConstraintsChecked = true;
2537                                         }
2538                                 }
2539                         }
2540
2541                         return type;
2542                 }
2543
2544                 public override bool Equals (object obj)
2545                 {
2546                         GenericTypeExpr cobj = obj as GenericTypeExpr;
2547                         if (cobj == null)
2548                                 return false;
2549
2550                         if ((type == null) || (cobj.type == null))
2551                                 return false;
2552
2553                         return type == cobj.type;
2554                 }
2555
2556                 public override int GetHashCode ()
2557                 {
2558                         return base.GetHashCode ();
2559                 }
2560         }
2561
2562         //
2563         // Generic type with unbound type arguments, used for typeof (G<,,>)
2564         //
2565         class GenericOpenTypeExpr : TypeExpression
2566         {
2567                 public GenericOpenTypeExpr (TypeSpec type, /*UnboundTypeArguments args,*/ Location loc)
2568                         : base (type.GetDefinition (), loc)
2569                 {
2570                 }
2571         }
2572
2573         struct ConstraintChecker
2574         {
2575                 IMemberContext mc;
2576                 bool recursive_checks;
2577
2578                 public ConstraintChecker (IMemberContext ctx)
2579                 {
2580                         this.mc = ctx;
2581                         recursive_checks = false;
2582                 }
2583
2584                 //
2585                 // Checks the constraints of open generic type against type
2586                 // arguments. This version is used for types which could not be
2587                 // checked immediatelly during construction because the type
2588                 // hierarchy was not yet fully setup (before Emit phase)
2589                 //
2590                 public static bool Check (IMemberContext mc, TypeSpec type, Location loc)
2591                 {
2592                         //
2593                         // Check declaring type first if there is any
2594                         //
2595                         if (type.DeclaringType != null && !Check (mc, type.DeclaringType, loc))
2596                                 return false;
2597
2598                         while (type is ElementTypeSpec)
2599                                 type = ((ElementTypeSpec) type).Element;
2600
2601                         if (type.Arity == 0)
2602                                 return true;
2603
2604                         var gtype = type as InflatedTypeSpec;
2605                         if (gtype == null)
2606                                 return true;
2607
2608                         var constraints = gtype.Constraints;
2609                         if (constraints == null)
2610                                 return true;
2611
2612                         if (gtype.HasConstraintsChecked)
2613                                 return true;
2614
2615                         var cc = new ConstraintChecker (mc);
2616                         cc.recursive_checks = true;
2617
2618                         if (cc.CheckAll (gtype.GetDefinition (), type.TypeArguments, constraints, loc)) {
2619                                 gtype.HasConstraintsChecked = true;
2620                                 return true;
2621                         }
2622
2623                         return false;
2624                 }
2625
2626                 //
2627                 // Checks all type arguments againts type parameters constraints
2628                 // NOTE: It can run in probing mode when `this.mc' is null
2629                 //
2630                 public bool CheckAll (MemberSpec context, TypeSpec[] targs, TypeParameterSpec[] tparams, Location loc)
2631                 {
2632                         if (targs == null)
2633                                 return true;
2634
2635                         for (int i = 0; i < tparams.Length; i++) {
2636                                 var targ = targs[i];
2637                                 if (!CheckConstraint (context, targ, tparams [i], loc))
2638                                         return false;
2639
2640                                 if (!recursive_checks)
2641                                         continue;
2642
2643                                 if (!Check (mc, targ, loc))
2644                                         return false;
2645                         }
2646
2647                         return true;
2648                 }
2649
2650                 bool CheckConstraint (MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, Location loc)
2651                 {
2652                         //
2653                         // First, check the `class' and `struct' constraints.
2654                         //
2655                         if (tparam.HasSpecialClass && !TypeSpec.IsReferenceType (atype)) {
2656                                 if (mc != null) {
2657                                         mc.Module.Compiler.Report.Error (452, loc,
2658                                                 "The type `{0}' must be a reference type in order to use it as type parameter `{1}' in the generic type or method `{2}'",
2659                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2660                                 }
2661
2662                                 return false;
2663                         }
2664
2665                         if (tparam.HasSpecialStruct && (!TypeSpec.IsValueType (atype) || atype.IsNullableType)) {
2666                                 if (mc != null) {
2667                                         mc.Module.Compiler.Report.Error (453, loc,
2668                                                 "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}'",
2669                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2670                                 }
2671
2672                                 return false;
2673                         }
2674
2675                         bool ok = true;
2676
2677                         //
2678                         // Check the class constraint
2679                         //
2680                         if (tparam.HasTypeConstraint) {
2681                                 if (!CheckConversion (mc, context, atype, tparam, tparam.BaseType, loc)) {
2682                                         if (mc == null)
2683                                                 return false;
2684
2685                                         ok = false;
2686                                 }
2687                         }
2688
2689                         //
2690                         // Check the interfaces constraints
2691                         //
2692                         if (tparam.InterfacesDefined != null) {
2693                                 foreach (TypeSpec iface in tparam.InterfacesDefined) {
2694                                         if (!CheckConversion (mc, context, atype, tparam, iface, loc)) {
2695                                                 if (mc == null)
2696                                                         return false;
2697
2698                                                 ok = false;
2699                                                 break;
2700                                         }
2701                                 }
2702                         }
2703
2704                         //
2705                         // Check the type parameter constraint
2706                         //
2707                         if (tparam.TypeArguments != null) {
2708                                 foreach (var ta in tparam.TypeArguments) {
2709                                         if (!CheckConversion (mc, context, atype, tparam, ta, loc)) {
2710                                                 if (mc == null)
2711                                                         return false;
2712
2713                                                 ok = false;
2714                                                 break;
2715                                         }
2716                                 }
2717                         }
2718
2719                         //
2720                         // Finally, check the constructor constraint.
2721                         //
2722                         if (!tparam.HasSpecialConstructor)
2723                                 return ok;
2724
2725                         if (!HasDefaultConstructor (atype)) {
2726                                 if (mc != null) {
2727                                         mc.Module.Compiler.Report.SymbolRelatedToPreviousError (atype);
2728                                         mc.Module.Compiler.Report.Error (310, loc,
2729                                                 "The type `{0}' must have a public parameterless constructor in order to use it as parameter `{1}' in the generic type or method `{2}'",
2730                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2731                                 }
2732                                 return false;
2733                         }
2734
2735                         return ok;
2736                 }
2737
2738                 static bool HasDynamicTypeArgument (TypeSpec[] targs)
2739                 {
2740                         for (int i = 0; i < targs.Length; ++i) {
2741                                 var targ = targs [i];
2742                                 if (targ.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2743                                         return true;
2744
2745                                 if (HasDynamicTypeArgument (targ.TypeArguments))
2746                                         return true;
2747                         }
2748
2749                         return false;
2750                 }
2751
2752                 bool CheckConversion (IMemberContext mc, MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, TypeSpec ttype, Location loc)
2753                 {
2754                         if (atype == ttype)
2755                                 return true;
2756
2757                         if (atype.IsGenericParameter) {
2758                                 var tps = (TypeParameterSpec) atype;
2759                                 if (tps.HasDependencyOn (ttype))
2760                                         return true;
2761
2762                                 if (Convert.ImplicitTypeParameterConversion (null, tps, ttype) != null)
2763                                         return true;
2764
2765                         } else if (TypeSpec.IsValueType (atype)) {
2766                                 if (atype.IsNullableType) {
2767                                         //
2768                                         // LAMESPEC: Only identity or base type ValueType or Object satisfy nullable type
2769                                         //
2770                                         if (TypeSpec.IsBaseClass (atype, ttype, false))
2771                                                 return true;
2772                                 } else {
2773                                         if (Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2774                                                 return true;
2775                                 }
2776                         } else {
2777                                 if (Convert.ImplicitReferenceConversionExists (atype, ttype) || Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2778                                         return true;
2779                         }
2780
2781                         if (mc != null) {
2782                                 mc.Module.Compiler.Report.SymbolRelatedToPreviousError (tparam);
2783                                 if (atype.IsGenericParameter) {
2784                                         mc.Module.Compiler.Report.Error (314, loc,
2785                                                 "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}'",
2786                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2787                                 } else if (TypeSpec.IsValueType (atype)) {
2788                                         if (atype.IsNullableType) {
2789                                                 if (ttype.IsInterface) {
2790                                                         mc.Module.Compiler.Report.Error (313, loc,
2791                                                                 "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}'",
2792                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2793                                                 } else {
2794                                                         mc.Module.Compiler.Report.Error (312, loc,
2795                                                                 "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}'",
2796                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2797                                                 }
2798                                         } else {
2799                                                 mc.Module.Compiler.Report.Error (315, loc,
2800                                                         "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}'",
2801                                                         atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2802                                         }
2803                                 } else {
2804                                         mc.Module.Compiler.Report.Error (311, loc,
2805                                                 "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}'",
2806                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2807                                 }
2808                         }
2809
2810                         return false;
2811                 }
2812
2813                 static bool HasDefaultConstructor (TypeSpec atype)
2814                 {
2815                         var tp = atype as TypeParameterSpec;
2816                         if (tp != null) {
2817                                 return tp.HasSpecialConstructor || tp.HasSpecialStruct;
2818                         }
2819
2820                         if (atype.IsStruct || atype.IsEnum)
2821                                 return true;
2822
2823                         if (atype.IsAbstract)
2824                                 return false;
2825
2826                         var tdef = atype.GetDefinition ();
2827
2828                         var found = MemberCache.FindMember (tdef,
2829                                 MemberFilter.Constructor (ParametersCompiled.EmptyReadOnlyParameters),
2830                                 BindingRestriction.DeclaredOnly | BindingRestriction.InstanceOnly);
2831
2832                         return found != null && (found.Modifiers & Modifiers.PUBLIC) != 0;
2833                 }
2834         }
2835
2836         //
2837         // Implements C# type inference
2838         //
2839         class TypeInference
2840         {
2841                 //
2842                 // Tracks successful rate of type inference
2843                 //
2844                 int score;
2845                 readonly Arguments arguments;
2846                 readonly int arg_count;
2847
2848                 public TypeInference (Arguments arguments)
2849                 {
2850                         this.arguments = arguments;
2851                         if (arguments != null)
2852                                 arg_count = arguments.Count;
2853                 }
2854
2855                 public int InferenceScore {
2856                         get {
2857                                 return score;
2858                         }
2859                 }
2860
2861                 public TypeSpec[] InferMethodArguments (ResolveContext ec, MethodSpec method)
2862                 {
2863                         var method_generic_args = method.GenericDefinition.TypeParameters;
2864                         TypeInferenceContext context = new TypeInferenceContext (method_generic_args);
2865                         if (!context.UnfixedVariableExists)
2866                                 return TypeSpec.EmptyTypes;
2867
2868                         AParametersCollection pd = method.Parameters;
2869                         if (!InferInPhases (ec, context, pd))
2870                                 return null;
2871
2872                         return context.InferredTypeArguments;
2873                 }
2874
2875                 //
2876                 // Implements method type arguments inference
2877                 //
2878                 bool InferInPhases (ResolveContext ec, TypeInferenceContext tic, AParametersCollection methodParameters)
2879                 {
2880                         int params_arguments_start;
2881                         if (methodParameters.HasParams) {
2882                                 params_arguments_start = methodParameters.Count - 1;
2883                         } else {
2884                                 params_arguments_start = arg_count;
2885                         }
2886
2887                         TypeSpec [] ptypes = methodParameters.Types;
2888
2889                         //
2890                         // The first inference phase
2891                         //
2892                         TypeSpec method_parameter = null;
2893                         for (int i = 0; i < arg_count; i++) {
2894                                 Argument a = arguments [i];
2895                                 if (a == null)
2896                                         continue;
2897
2898                                 if (i < params_arguments_start) {
2899                                         method_parameter = methodParameters.Types [i];
2900                                 } else if (i == params_arguments_start) {
2901                                         if (arg_count == params_arguments_start + 1 && TypeManager.HasElementType (a.Type))
2902                                                 method_parameter = methodParameters.Types [params_arguments_start];
2903                                         else
2904                                                 method_parameter = TypeManager.GetElementType (methodParameters.Types [params_arguments_start]);
2905
2906                                         ptypes = (TypeSpec[]) ptypes.Clone ();
2907                                         ptypes [i] = method_parameter;
2908                                 }
2909
2910                                 //
2911                                 // When a lambda expression, an anonymous method
2912                                 // is used an explicit argument type inference takes a place
2913                                 //
2914                                 AnonymousMethodExpression am = a.Expr as AnonymousMethodExpression;
2915                                 if (am != null) {
2916                                         if (am.ExplicitTypeInference (tic, method_parameter))
2917                                                 ++score;
2918                                         continue;
2919                                 }
2920
2921                                 if (a.IsByRef) {
2922                                         score += tic.ExactInference (a.Type, method_parameter);
2923                                         continue;
2924                                 }
2925
2926                                 if (a.Expr.Type == InternalType.NullLiteral)
2927                                         continue;
2928
2929                                 if (TypeSpec.IsValueType (method_parameter)) {
2930                                         score += tic.LowerBoundInference (a.Type, method_parameter);
2931                                         continue;
2932                                 }
2933
2934                                 //
2935                                 // Otherwise an output type inference is made
2936                                 //
2937                                 score += tic.OutputTypeInference (ec, a.Expr, method_parameter);
2938                         }
2939
2940                         //
2941                         // Part of the second phase but because it happens only once
2942                         // we don't need to call it in cycle
2943                         //
2944                         bool fixed_any = false;
2945                         if (!tic.FixIndependentTypeArguments (ec, ptypes, ref fixed_any))
2946                                 return false;
2947
2948                         return DoSecondPhase (ec, tic, ptypes, !fixed_any);
2949                 }
2950
2951                 bool DoSecondPhase (ResolveContext ec, TypeInferenceContext tic, TypeSpec[] methodParameters, bool fixDependent)
2952                 {
2953                         bool fixed_any = false;
2954                         if (fixDependent && !tic.FixDependentTypes (ec, ref fixed_any))
2955                                 return false;
2956
2957                         // If no further unfixed type variables exist, type inference succeeds
2958                         if (!tic.UnfixedVariableExists)
2959                                 return true;
2960
2961                         if (!fixed_any && fixDependent)
2962                                 return false;
2963
2964                         // For all arguments where the corresponding argument output types
2965                         // contain unfixed type variables but the input types do not,
2966                         // an output type inference is made
2967                         for (int i = 0; i < arg_count; i++) {
2968
2969                                 // Align params arguments
2970                                 TypeSpec t_i = methodParameters [i >= methodParameters.Length ? methodParameters.Length - 1: i];
2971
2972                                 if (!t_i.IsDelegate) {
2973                                         if (!t_i.IsExpressionTreeType)
2974                                                 continue;
2975
2976                                         t_i = TypeManager.GetTypeArguments (t_i) [0];
2977                                 }
2978
2979                                 var mi = Delegate.GetInvokeMethod (t_i);
2980                                 TypeSpec rtype = mi.ReturnType;
2981
2982                                 if (tic.IsReturnTypeNonDependent (mi, rtype)) {
2983                                         // It can be null for default arguments
2984                                         if (arguments[i] == null)
2985                                                 continue;
2986
2987                                         score += tic.OutputTypeInference (ec, arguments[i].Expr, t_i);
2988                                 }
2989                         }
2990
2991
2992                         return DoSecondPhase (ec, tic, methodParameters, true);
2993                 }
2994         }
2995
2996         public class TypeInferenceContext
2997         {
2998                 protected enum BoundKind
2999                 {
3000                         Exact   = 0,
3001                         Lower   = 1,
3002                         Upper   = 2
3003                 }
3004
3005                 struct BoundInfo : IEquatable<BoundInfo>
3006                 {
3007                         public readonly TypeSpec Type;
3008                         public readonly BoundKind Kind;
3009
3010                         public BoundInfo (TypeSpec type, BoundKind kind)
3011                         {
3012                                 this.Type = type;
3013                                 this.Kind = kind;
3014                         }
3015
3016                         public override int GetHashCode ()
3017                         {
3018                                 return Type.GetHashCode ();
3019                         }
3020
3021                         public Expression GetTypeExpression ()
3022                         {
3023                                 return new TypeExpression (Type, Location.Null);
3024                         }
3025
3026                         #region IEquatable<BoundInfo> Members
3027
3028                         public bool Equals (BoundInfo other)
3029                         {
3030                                 return Type == other.Type && Kind == other.Kind;
3031                         }
3032
3033                         #endregion
3034                 }
3035
3036                 readonly TypeSpec[] tp_args;
3037                 readonly TypeSpec[] fixed_types;
3038                 readonly List<BoundInfo>[] bounds;
3039
3040                 // TODO MemberCache: Could it be TypeParameterSpec[] ??
3041                 public TypeInferenceContext (TypeSpec[] typeArguments)
3042                 {
3043                         if (typeArguments.Length == 0)
3044                                 throw new ArgumentException ("Empty generic arguments");
3045
3046                         fixed_types = new TypeSpec [typeArguments.Length];
3047                         for (int i = 0; i < typeArguments.Length; ++i) {
3048                                 if (typeArguments [i].IsGenericParameter) {
3049                                         if (bounds == null) {
3050                                                 bounds = new List<BoundInfo> [typeArguments.Length];
3051                                                 tp_args = new TypeSpec [typeArguments.Length];
3052                                         }
3053                                         tp_args [i] = typeArguments [i];
3054                                 } else {
3055                                         fixed_types [i] = typeArguments [i];
3056                                 }
3057                         }
3058                 }
3059
3060                 //
3061                 // Used together with AddCommonTypeBound fo implement
3062                 // 7.4.2.13 Finding the best common type of a set of expressions
3063                 //
3064                 public TypeInferenceContext ()
3065                 {
3066                         fixed_types = new TypeSpec [1];
3067                         tp_args = new TypeSpec [1];
3068                         tp_args[0] = InternalType.Arglist; // it can be any internal type
3069                         bounds = new List<BoundInfo> [1];
3070                 }
3071
3072                 public TypeSpec[] InferredTypeArguments {
3073                         get {
3074                                 return fixed_types;
3075                         }
3076                 }
3077
3078                 public void AddCommonTypeBound (TypeSpec type)
3079                 {
3080                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, false);
3081                 }
3082
3083                 public void AddCommonTypeBoundAsync (TypeSpec type)
3084                 {
3085                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, true);
3086                 }
3087
3088                 void AddToBounds (BoundInfo bound, int index, bool voidAllowed)
3089                 {
3090                         //
3091                         // Some types cannot be used as type arguments
3092                         //
3093                         if ((bound.Type.Kind == MemberKind.Void && !voidAllowed) || bound.Type.IsPointer || bound.Type.IsSpecialRuntimeType ||
3094                                 bound.Type == InternalType.MethodGroup || bound.Type == InternalType.AnonymousMethod || bound.Type == InternalType.VarOutType)
3095                                 return;
3096
3097                         var a = bounds [index];
3098                         if (a == null) {
3099                                 a = new List<BoundInfo> (2);
3100                                 a.Add (bound);
3101                                 bounds [index] = a;
3102                                 return;
3103                         }
3104
3105                         if (a.Contains (bound))
3106                                 return;
3107
3108                         a.Add (bound);
3109                 }
3110
3111                 bool AllTypesAreFixed (TypeSpec[] types)
3112                 {
3113                         foreach (TypeSpec t in types) {
3114                                 if (t.IsGenericParameter) {
3115                                         if (!IsFixed (t))
3116                                                 return false;
3117                                         continue;
3118                                 }
3119
3120                                 if (t.IsGeneric && !AllTypesAreFixed (t.TypeArguments))
3121                                         return false;
3122                         }
3123
3124                         return true;
3125                 }
3126
3127                 //
3128                 // 26.3.3.8 Exact Inference
3129                 //
3130                 public int ExactInference (TypeSpec u, TypeSpec v)
3131                 {
3132                         // If V is an array type
3133                         if (v.IsArray) {
3134                                 if (!u.IsArray)
3135                                         return 0;
3136
3137                                 var ac_u = (ArrayContainer) u;
3138                                 var ac_v = (ArrayContainer) v;
3139                                 if (ac_u.Rank != ac_v.Rank)
3140                                         return 0;
3141
3142                                 return ExactInference (ac_u.Element, ac_v.Element);
3143                         }
3144
3145                         //
3146                         // If V is constructed type and U is constructed type or dynamic
3147                         //
3148                         if (TypeManager.IsGenericType (v)) {
3149                                 if (u.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
3150
3151                                         var ga_v = v.TypeArguments;
3152
3153                                         int score = 0;
3154                                         for (int i = 0; i < ga_v.Length; ++i)
3155                                                 score += ExactInference (u, ga_v [i]);
3156
3157                                         return System.Math.Min (1, score);
3158
3159                                 } else {
3160                                         if (!TypeManager.IsGenericType (u) || v.MemberDefinition != u.MemberDefinition)
3161                                                 return 0;
3162
3163                                         var ga_u = u.TypeArguments;
3164                                         var ga_v = v.TypeArguments;
3165
3166                                         if (u.TypeArguments.Length != v.TypeArguments.Length)
3167                                                 return 0;
3168
3169                                         int score = 0;
3170                                         for (int i = 0; i < ga_v.Length; ++i)
3171                                                 score += ExactInference (ga_u [i], ga_v [i]);
3172
3173                                         return System.Math.Min (1, score);
3174                                 }
3175                         }
3176
3177                         // If V is one of the unfixed type arguments
3178                         int pos = IsUnfixed (v);
3179                         if (pos == -1)
3180                                 return 0;
3181
3182                         AddToBounds (new BoundInfo (u, BoundKind.Exact), pos, false);
3183                         return 1;
3184                 }
3185
3186                 public bool FixAllTypes (ResolveContext ec)
3187                 {
3188                         for (int i = 0; i < tp_args.Length; ++i) {
3189                                 if (!FixType (ec, i))
3190                                         return false;
3191                         }
3192                         return true;
3193                 }
3194
3195                 //
3196                 // All unfixed type variables Xi are fixed for which all of the following hold:
3197                 // a, There is at least one type variable Xj that depends on Xi
3198                 // b, Xi has a non-empty set of bounds
3199                 //
3200                 public bool FixDependentTypes (ResolveContext ec, ref bool fixed_any)
3201                 {
3202                         for (int i = 0; i < tp_args.Length; ++i) {
3203                                 if (fixed_types[i] != null)
3204                                         continue;
3205
3206                                 if (bounds[i] == null)
3207                                         continue;
3208
3209                                 if (!FixType (ec, i))
3210                                         return false;
3211
3212                                 fixed_any = true;
3213                         }
3214
3215                         return true;
3216                 }
3217
3218                 //
3219                 // All unfixed type variables Xi which depend on no Xj are fixed
3220                 //
3221                 public bool FixIndependentTypeArguments (ResolveContext ec, TypeSpec[] methodParameters, ref bool fixed_any)
3222                 {
3223                         var types_to_fix = new List<TypeSpec> (tp_args);
3224                         for (int i = 0; i < methodParameters.Length; ++i) {
3225                                 TypeSpec t = methodParameters[i];
3226
3227                                 if (!t.IsDelegate) {
3228                                         if (!t.IsExpressionTreeType)
3229                                                 continue;
3230
3231                                         t =  TypeManager.GetTypeArguments (t) [0];
3232                                 }
3233
3234                                 if (t.IsGenericParameter)
3235                                         continue;
3236
3237                                 var invoke = Delegate.GetInvokeMethod (t);
3238                                 TypeSpec rtype = invoke.ReturnType;
3239                                 while (rtype.IsArray)
3240                                         rtype = ((ArrayContainer) rtype).Element;
3241
3242                                 if (!rtype.IsGenericParameter && !TypeManager.IsGenericType (rtype))
3243                                         continue;
3244
3245                                 // Remove dependent types, they cannot be fixed yet
3246                                 RemoveDependentTypes (types_to_fix, rtype);
3247                         }
3248
3249                         foreach (TypeSpec t in types_to_fix) {
3250                                 if (t == null)
3251                                         continue;
3252
3253                                 int idx = IsUnfixed (t);
3254                                 if (idx >= 0 && !FixType (ec, idx)) {
3255                                         return false;
3256                                 }
3257                         }
3258
3259                         fixed_any = types_to_fix.Count > 0;
3260                         return true;
3261                 }
3262
3263                 //
3264                 // 26.3.3.10 Fixing
3265                 //
3266                 public bool FixType (ResolveContext ec, int i)
3267                 {
3268                         // It's already fixed
3269                         if (fixed_types[i] != null)
3270                                 throw new InternalErrorException ("Type argument has been already fixed");
3271
3272                         var candidates = bounds [i];
3273                         if (candidates == null)
3274                                 return false;
3275
3276                         if (candidates.Count == 1) {
3277                                 TypeSpec t = candidates[0].Type;
3278                                 if (t == InternalType.NullLiteral)
3279                                         return false;
3280
3281                                 fixed_types [i] = t;
3282                                 return true;
3283                         }
3284
3285                         //
3286                         // The set of candidate types Uj starts out as the set of
3287                         // all types in the set of bounds for Xi
3288                         //
3289                         var applicable = new bool [candidates.Count];
3290                         for (int ci = 0; ci < applicable.Length; ++ci)
3291                                 applicable [ci] = true;
3292
3293                         for (int ci = 0; ci < applicable.Length; ++ci) {
3294                                 var bound = candidates [ci];
3295                                 int cii = 0;
3296
3297                                 switch (bound.Kind) {
3298                                 case BoundKind.Exact:
3299                                         for (; cii != applicable.Length; ++cii) {
3300                                                 if (ci == cii)
3301                                                         continue;
3302
3303                                                 if (!applicable[cii])
3304                                                         continue;
3305
3306                                                 //
3307                                                 // For each exact bound U of Xi all types Uj which are not identical
3308                                                 // to U are removed from the candidate set
3309                                                 //
3310                                                 if (candidates [cii].Type != bound.Type)
3311                                                         applicable[cii] = false;
3312                                         }
3313
3314                                         break;
3315                                 case BoundKind.Lower:
3316                                         for (; cii != applicable.Length; ++cii) {
3317                                                 if (ci == cii)
3318                                                         continue;
3319
3320                                                 if (!applicable[cii])
3321                                                         continue;
3322
3323                                                 //
3324                                                 // For each lower bound U of Xi all types Uj to which there is not an implicit conversion
3325                                                 // from U are removed from the candidate set
3326                                                 //
3327                                                 if (!Convert.ImplicitConversionExists (ec, bound.GetTypeExpression (), candidates [cii].Type)) {
3328                                                         applicable[cii] = false;
3329                                                 }
3330                                         }
3331
3332                                         break;
3333
3334                                 case BoundKind.Upper:
3335                                         for (; cii != applicable.Length; ++cii) {
3336                                                 if (ci == cii)
3337                                                         continue;
3338
3339                                                 if (!applicable[cii])
3340                                                         continue;
3341
3342                                                 //
3343                                                 // For each upper bound U of Xi all types Uj from which there is not an implicit conversion
3344                                                 // to U are removed from the candidate set
3345                                                 //
3346                                                 if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3347                                                         applicable[cii] = false;
3348                                         }
3349
3350                                         break;
3351                                 }
3352                         }
3353
3354                         TypeSpec best_candidate = null;
3355                         for (int ci = 0; ci < applicable.Length; ++ci) {
3356                                 if (!applicable[ci])
3357                                         continue;
3358
3359                                 var bound = candidates [ci];
3360                                 if (bound.Type == best_candidate)
3361                                         continue;
3362
3363                                 int cii = 0;
3364                                 for (; cii < applicable.Length; ++cii) {
3365                                         if (ci == cii)
3366                                                 continue;
3367
3368                                         if (!applicable[cii])
3369                                                 continue;
3370
3371                                         if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3372                                                 break;
3373                                 }
3374
3375                                 if (cii != applicable.Length)
3376                                         continue;
3377
3378                                 //
3379                                 // We already have the best candidate, break if it's different (non-unique)
3380                                 //
3381                                 // Dynamic is never ambiguous as we prefer dynamic over other best candidate types
3382                                 //
3383                                 if (best_candidate != null) {
3384
3385                                         if (best_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3386                                                 continue;
3387
3388                                         if (bound.Type.BuiltinType != BuiltinTypeSpec.Type.Dynamic && best_candidate != bound.Type)
3389                                                 return false;
3390                                 }
3391
3392                                 best_candidate = bound.Type;
3393                         }
3394
3395                         if (best_candidate == null)
3396                                 return false;
3397
3398                         fixed_types[i] = best_candidate;
3399                         return true;
3400                 }
3401
3402                 public bool HasBounds (int pos)
3403                 {
3404                         return bounds[pos] != null;
3405                 }
3406
3407                 //
3408                 // Uses inferred or partially infered types to inflate delegate type argument. Returns
3409                 // null when type parameter has not been fixed
3410                 //
3411                 public TypeSpec InflateGenericArgument (IModuleContext context, TypeSpec parameter)
3412                 {
3413                         var tp = parameter as TypeParameterSpec;
3414                         if (tp != null) {
3415                                 //
3416                                 // Type inference works on generic arguments (MVAR) only
3417                                 //
3418                                 if (!tp.IsMethodOwned)
3419                                         return parameter;
3420
3421                                 //
3422                                 // Ensure the type parameter belongs to same container
3423                                 //
3424                                 if (tp.DeclaredPosition < tp_args.Length && tp_args[tp.DeclaredPosition] == parameter)
3425                                         return fixed_types[tp.DeclaredPosition] ?? parameter;
3426
3427                                 return parameter;
3428                         }
3429
3430                         var gt = parameter as InflatedTypeSpec;
3431                         if (gt != null) {
3432                                 var inflated_targs = new TypeSpec [gt.TypeArguments.Length];
3433                                 for (int ii = 0; ii < inflated_targs.Length; ++ii) {
3434                                         var inflated = InflateGenericArgument (context, gt.TypeArguments [ii]);
3435                                         if (inflated == null)
3436                                                 return null;
3437
3438                                         inflated_targs[ii] = inflated;
3439                                 }
3440
3441                                 return gt.GetDefinition ().MakeGenericType (context, inflated_targs);
3442                         }
3443
3444                         var ac = parameter as ArrayContainer;
3445                         if (ac != null) {
3446                                 var inflated = InflateGenericArgument (context, ac.Element);
3447                                 if (inflated != ac.Element)
3448                                         return ArrayContainer.MakeType (context.Module, inflated);
3449                         }
3450
3451                         return parameter;
3452                 }
3453
3454                 //
3455                 // Tests whether all delegate input arguments are fixed and generic output type
3456                 // requires output type inference
3457                 //
3458                 public bool IsReturnTypeNonDependent (MethodSpec invoke, TypeSpec returnType)
3459                 {
3460                         AParametersCollection d_parameters = invoke.Parameters;
3461
3462                         if (d_parameters.IsEmpty)
3463                                 return true;
3464
3465                         while (returnType.IsArray)
3466                                 returnType = ((ArrayContainer) returnType).Element;
3467
3468                         if (returnType.IsGenericParameter) {
3469                                 if (IsFixed (returnType))
3470                                     return false;
3471                         } else if (TypeManager.IsGenericType (returnType)) {
3472                                 TypeSpec[] g_args = TypeManager.GetTypeArguments (returnType);
3473
3474                                 // At least one unfixed return type has to exist
3475                                 if (AllTypesAreFixed (g_args))
3476                                         return false;
3477                         } else {
3478                                 return false;
3479                         }
3480
3481                         // All generic input arguments have to be fixed
3482                         return AllTypesAreFixed (d_parameters.Types);
3483                 }
3484
3485                 bool IsFixed (TypeSpec type)
3486                 {
3487                         return IsUnfixed (type) == -1;
3488                 }
3489
3490                 int IsUnfixed (TypeSpec type)
3491                 {
3492                         if (!type.IsGenericParameter)
3493                                 return -1;
3494
3495                         for (int i = 0; i < tp_args.Length; ++i) {
3496                                 if (tp_args[i] == type) {
3497                                         if (fixed_types[i] != null)
3498                                                 break;
3499
3500                                         return i;
3501                                 }
3502                         }
3503
3504                         return -1;
3505                 }
3506
3507                 //
3508                 // 26.3.3.9 Lower-bound Inference
3509                 //
3510                 public int LowerBoundInference (TypeSpec u, TypeSpec v)
3511                 {
3512                         return LowerBoundInference (u, v, false);
3513                 }
3514
3515                 //
3516                 // Lower-bound (false) or Upper-bound (true) inference based on inversed argument
3517                 //
3518                 int LowerBoundInference (TypeSpec u, TypeSpec v, bool inversed)
3519                 {
3520                         // If V is one of the unfixed type arguments
3521                         int pos = IsUnfixed (v);
3522                         if (pos != -1) {
3523                                 AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos, false);
3524                                 return 1;
3525                         }
3526
3527                         // If U is an array type
3528                         var u_ac = u as ArrayContainer;
3529                         if (u_ac != null) {
3530                                 var v_ac = v as ArrayContainer;
3531                                 if (v_ac != null) {
3532                                         if (u_ac.Rank != v_ac.Rank)
3533                                                 return 0;
3534
3535                                         if (TypeSpec.IsValueType (u_ac.Element))
3536                                                 return ExactInference (u_ac.Element, v_ac.Element);
3537
3538                                         return LowerBoundInference (u_ac.Element, v_ac.Element, inversed);
3539                                 }
3540
3541                                 if (u_ac.Rank != 1 || !v.IsArrayGenericInterface)
3542                                         return 0;
3543
3544                                 var v_i = TypeManager.GetTypeArguments (v) [0];
3545                                 if (TypeSpec.IsValueType (u_ac.Element))
3546                                         return ExactInference (u_ac.Element, v_i);
3547
3548                                 return LowerBoundInference (u_ac.Element, v_i);
3549                         }
3550
3551                         if (v.IsGenericOrParentIsGeneric) {
3552                                 //
3553                                 // if V is a constructed type C<V1..Vk> and there is a unique type C<U1..Uk>
3554                                 // such that U is identical to, inherits from (directly or indirectly),
3555                                 // or implements (directly or indirectly) C<U1..Uk>
3556                                 //
3557                                 var u_candidates = new List<TypeSpec> ();
3558                                 var open_v = v.MemberDefinition;
3559
3560                                 for (TypeSpec t = u; t != null; t = t.BaseType) {
3561                                         if (open_v == t.MemberDefinition)
3562                                                 u_candidates.Add (t);
3563
3564                                         //
3565                                         // Using this trick for dynamic type inference, the spec says the type arguments are "unknown" but
3566                                         // that would complicate the process a lot, instead I treat them as dynamic
3567                                         //
3568                                         if (t.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3569                                                 u_candidates.Add (t);
3570                                 }
3571
3572                                 if (u.Interfaces != null) {
3573                                         foreach (var iface in u.Interfaces) {
3574                                                 if (open_v == iface.MemberDefinition)
3575                                                         u_candidates.Add (iface);
3576                                         }
3577                                 }
3578
3579                                 TypeSpec[] unique_candidate_targs = null;
3580                                 var ga_v = TypeSpec.GetAllTypeArguments (v);
3581                                 foreach (TypeSpec u_candidate in u_candidates) {
3582                                         //
3583                                         // The unique set of types U1..Uk means that if we have an interface I<T>,
3584                                         // class U : I<int>, I<long> then no type inference is made when inferring
3585                                         // type I<T> by applying type U because T could be int or long
3586                                         //
3587                                         if (unique_candidate_targs != null) {
3588                                                 TypeSpec[] second_unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3589                                                 if (TypeSpecComparer.Equals (unique_candidate_targs, second_unique_candidate_targs)) {
3590                                                         unique_candidate_targs = second_unique_candidate_targs;
3591                                                         continue;
3592                                                 }
3593
3594                                                 //
3595                                                 // Break when candidate arguments are ambiguous
3596                                                 //
3597                                                 return 0;
3598                                         }
3599
3600                                         //
3601                                         // A candidate is dynamic type expression, to simplify things use dynamic
3602                                         // for all type parameter of this type. For methods like this one
3603                                         //
3604                                         // void M<T, U> (IList<T>, IList<U[]>)
3605                                         //
3606                                         // dynamic becomes both T and U when the arguments are of dynamic type
3607                                         //
3608                                         if (u_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
3609                                                 unique_candidate_targs = new TypeSpec[ga_v.Length];
3610                                                 for (int i = 0; i < unique_candidate_targs.Length; ++i)
3611                                                         unique_candidate_targs[i] = u_candidate;
3612                                         } else {
3613                                                 unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3614                                         }
3615                                 }
3616
3617                                 if (unique_candidate_targs != null) {
3618                                         int score = 0;
3619                                         int tp_index = -1;
3620                                         TypeParameterSpec[] tps = null;
3621
3622                                         for (int i = 0; i < unique_candidate_targs.Length; ++i) {
3623                                                 if (tp_index < 0) {
3624                                                         while (v.Arity == 0)
3625                                                                 v = v.DeclaringType;
3626
3627                                                         tps = v.MemberDefinition.TypeParameters;
3628                                                         tp_index = tps.Length - 1;
3629                                                 }
3630
3631                                                 Variance variance = tps [tp_index--].Variance;
3632
3633                                                 TypeSpec u_i = unique_candidate_targs [i];
3634                                                 if (variance == Variance.None || TypeSpec.IsValueType (u_i)) {
3635                                                         if (ExactInference (u_i, ga_v [i]) == 0)
3636                                                                 ++score;
3637                                                 } else {
3638                                                         bool upper_bound = (variance == Variance.Contravariant && !inversed) ||
3639                                                                 (variance == Variance.Covariant && inversed);
3640
3641                                                         if (LowerBoundInference (u_i, ga_v [i], upper_bound) == 0)
3642                                                                 ++score;
3643                                                 }
3644                                         }
3645
3646                                         return score;
3647                                 }
3648                         }
3649
3650                         return 0;
3651                 }
3652
3653                 //
3654                 // 26.3.3.6 Output Type Inference
3655                 //
3656                 public int OutputTypeInference (ResolveContext ec, Expression e, TypeSpec t)
3657                 {
3658                         // If e is a lambda or anonymous method with inferred return type
3659                         AnonymousMethodExpression ame = e as AnonymousMethodExpression;
3660                         if (ame != null) {
3661                                 TypeSpec rt = ame.InferReturnType (ec, this, t);
3662                                 var invoke = Delegate.GetInvokeMethod (t);
3663
3664                                 if (rt == null) {
3665                                         AParametersCollection pd = invoke.Parameters;
3666                                         return ame.Parameters.Count == pd.Count ? 1 : 0;
3667                                 }
3668
3669                                 TypeSpec rtype = invoke.ReturnType;
3670                                 return LowerBoundInference (rt, rtype) + 1;
3671                         }
3672
3673                         //
3674                         // if E is a method group and T is a delegate type or expression tree type
3675                         // return type Tb with parameter types T1..Tk and return type Tb, and overload
3676                         // resolution of E with the types T1..Tk yields a single method with return type U,
3677                         // then a lower-bound inference is made from U for Tb.
3678                         //
3679                         if (e is MethodGroupExpr) {
3680                                 if (!t.IsDelegate) {
3681                                         if (!t.IsExpressionTreeType)
3682                                                 return 0;
3683
3684                                         t = TypeManager.GetTypeArguments (t)[0];
3685                                 }
3686
3687                                 var invoke = Delegate.GetInvokeMethod (t);
3688                                 TypeSpec rtype = invoke.ReturnType;
3689
3690                                 if (!IsReturnTypeNonDependent (invoke, rtype))
3691                                         return 0;
3692
3693                                 // LAMESPEC: Standard does not specify that all methodgroup arguments
3694                                 // has to be fixed but it does not specify how to do recursive type inference
3695                                 // either. We choose the simple option and infer return type only
3696                                 // if all delegate generic arguments are fixed.
3697                                 TypeSpec[] param_types = new TypeSpec [invoke.Parameters.Count];
3698                                 for (int i = 0; i < param_types.Length; ++i) {
3699                                         var inflated = InflateGenericArgument (ec, invoke.Parameters.Types[i]);
3700                                         if (inflated == null)
3701                                                 return 0;
3702
3703                                         param_types[i] = inflated;
3704                                 }
3705
3706                                 MethodGroupExpr mg = (MethodGroupExpr) e;
3707                                 Arguments args = DelegateCreation.CreateDelegateMethodArguments (ec, invoke.Parameters, param_types, e.Location);
3708                                 mg = mg.OverloadResolve (ec, ref args, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly);
3709                                 if (mg == null)
3710                                         return 0;
3711
3712                                 return LowerBoundInference (mg.BestCandidateReturnType, rtype) + 1;
3713                         }
3714
3715                         //
3716                         // if e is an expression with type U, then
3717                         // a lower-bound inference is made from U for T
3718                         //
3719                         return LowerBoundInference (e.Type, t) * 2;
3720                 }
3721
3722                 void RemoveDependentTypes (List<TypeSpec> types, TypeSpec returnType)
3723                 {
3724                         int idx = IsUnfixed (returnType);
3725                         if (idx >= 0) {
3726                                 types [idx] = null;
3727                                 return;
3728                         }
3729
3730                         if (TypeManager.IsGenericType (returnType)) {
3731                                 foreach (TypeSpec t in TypeManager.GetTypeArguments (returnType)) {
3732                                         RemoveDependentTypes (types, t);
3733                                 }
3734                         }
3735                 }
3736
3737                 public bool UnfixedVariableExists {
3738                         get {
3739                                 foreach (TypeSpec ut in fixed_types) {
3740                                         if (ut == null)
3741                                                 return true;
3742                                 }
3743
3744                                 return false;
3745                         }
3746                 }
3747         }
3748 }