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                                 }
1776
1777                                 if (arg.HasNamedTupleElement) {
1778                                         state |= StateFlags.HasNamedTupleElement;
1779                                 }
1780                         }
1781
1782                         if (open_type.Kind == MemberKind.MissingType)
1783                                 MemberCache = MemberCache.Empty;
1784
1785                         if ((open_type.Modifiers & Modifiers.COMPILER_GENERATED) != 0)
1786                                 state |= StateFlags.ConstraintsChecked;
1787                 }
1788
1789                 #region Properties
1790
1791                 public override TypeSpec BaseType {
1792                         get {
1793                                 if (cache == null || (state & StateFlags.PendingBaseTypeInflate) != 0)
1794                                         InitializeMemberCache (true);
1795
1796                                 return base.BaseType;
1797                         }
1798                 }
1799
1800                 //
1801                 // Inflated type parameters with constraints array, mapping with type arguments is based on index
1802                 //
1803                 public TypeParameterSpec[] Constraints {
1804                         get {
1805                                 if (constraints == null) {
1806                                         constraints = TypeParameterSpec.InflateConstraints (MemberDefinition.TypeParameters, l => l.CreateLocalInflator (context), this);
1807                                 }
1808
1809                                 return constraints;
1810                         }
1811                 }
1812
1813                 //
1814                 // Used to cache expensive constraints validation on constructed types
1815                 //
1816                 public bool HasConstraintsChecked {
1817                         get {
1818                                 return (state & StateFlags.ConstraintsChecked) != 0;
1819                         }
1820                         set {
1821                                 state = value ? state | StateFlags.ConstraintsChecked : state & ~StateFlags.ConstraintsChecked;
1822                         }
1823                 }
1824
1825                 public override IList<TypeSpec> Interfaces {
1826                         get {
1827                                 if (cache == null)
1828                                         InitializeMemberCache (true);
1829
1830                                 return base.Interfaces;
1831                         }
1832                 }
1833
1834                 public override bool IsExpressionTreeType {
1835                         get {
1836                                 return (open_type.state & StateFlags.InflatedExpressionType) != 0;
1837                         }
1838                 }
1839
1840                 public override bool IsArrayGenericInterface {
1841                         get {
1842                                 return (open_type.state & StateFlags.GenericIterateInterface) != 0;
1843                         }
1844                 }
1845
1846                 public override bool IsGenericTask {
1847                         get {
1848                                 return (open_type.state & StateFlags.GenericTask) != 0;
1849                         }
1850                 }
1851
1852                 public override bool IsNullableType {
1853                         get {
1854                                 return (open_type.state & StateFlags.InflatedNullableType) != 0;
1855                         }
1856                 }
1857
1858                 public override bool IsTupleType {
1859                         get {
1860                                 return (open_type.state & StateFlags.Tuple) != 0;
1861                         }
1862                 }
1863
1864                 //
1865                 // Types used to inflate the generic  type
1866                 //
1867                 public override TypeSpec[] TypeArguments {
1868                         get {
1869                                 return targs;
1870                         }
1871                 }
1872
1873                 #endregion
1874
1875                 public override bool AddInterface (TypeSpec iface)
1876                 {
1877                         var inflator = CreateLocalInflator (context);
1878                         iface = inflator.Inflate (iface);
1879                         if (iface == null)
1880                                 return false;
1881
1882                         return base.AddInterface (iface);
1883                 }
1884
1885                 public static bool ContainsTypeParameter (TypeSpec type)
1886                 {
1887                         if (type.Kind == MemberKind.TypeParameter)
1888                                 return true;
1889
1890                         var element_container = type as ElementTypeSpec;
1891                         if (element_container != null)
1892                                 return ContainsTypeParameter (element_container.Element);
1893
1894                         foreach (var t in type.TypeArguments) {
1895                                 if (ContainsTypeParameter (t)) {
1896                                         return true;
1897                                 }
1898                         }
1899
1900                         return false;
1901                 }
1902
1903                 public TypeParameterInflator CreateLocalInflator (IModuleContext context)
1904                 {
1905                         TypeParameterSpec[] tparams_full;
1906                         TypeSpec[] targs_full = targs;
1907                         if (IsNested) {
1908                                 //
1909                                 // Special case is needed when we are inflating an open type (nested type definition)
1910                                 // on inflated parent. Consider following case
1911                                 //
1912                                 // Foo<T>.Bar<U> => Foo<string>.Bar<U>
1913                                 //
1914                                 // Any later inflation of Foo<string>.Bar<U> has to also inflate T if used inside Bar<U>
1915                                 //
1916                                 List<TypeSpec> merged_targs = null;
1917                                 List<TypeParameterSpec> merged_tparams = null;
1918
1919                                 var type = DeclaringType;
1920
1921                                 do {
1922                                         if (type.TypeArguments.Length > 0) {
1923                                                 if (merged_targs == null) {
1924                                                         merged_targs = new List<TypeSpec> ();
1925                                                         merged_tparams = new List<TypeParameterSpec> ();
1926                                                         if (targs.Length > 0) {
1927                                                                 merged_targs.AddRange (targs);
1928                                                                 merged_tparams.AddRange (open_type.MemberDefinition.TypeParameters);
1929                                                         }
1930                                                 }
1931                                                 merged_tparams.AddRange (type.MemberDefinition.TypeParameters);
1932                                                 merged_targs.AddRange (type.TypeArguments);
1933                                         }
1934                                         type = type.DeclaringType;
1935                                 } while (type != null);
1936
1937                                 if (merged_targs != null) {
1938                                         // Type arguments are not in the right order but it should not matter in this case
1939                                         targs_full = merged_targs.ToArray ();
1940                                         tparams_full = merged_tparams.ToArray ();
1941                                 } else if (targs.Length == 0) {
1942                                         tparams_full = TypeParameterSpec.EmptyTypes;
1943                                 } else {
1944                                         tparams_full = open_type.MemberDefinition.TypeParameters;
1945                                 }
1946                         } else if (targs.Length == 0) {
1947                                 tparams_full = TypeParameterSpec.EmptyTypes;
1948                         } else {
1949                                 tparams_full = open_type.MemberDefinition.TypeParameters;
1950                         }
1951
1952                         return new TypeParameterInflator (context, this, tparams_full, targs_full);
1953                 }
1954
1955                 MetaType CreateMetaInfo ()
1956                 {
1957                         //
1958                         // Converts nested type arguments into right order
1959                         // Foo<string, bool>.Bar<int> => string, bool, int
1960                         //
1961                         var all = new List<MetaType> ();
1962                         TypeSpec type = this;
1963                         TypeSpec definition = type;
1964                         do {
1965                                 if (type.GetDefinition().IsGeneric) {
1966                                         all.InsertRange (0,
1967                                                 type.TypeArguments != TypeSpec.EmptyTypes ?
1968                                                 type.TypeArguments.Select (l => l.GetMetaInfo ()) :
1969                                                 type.MemberDefinition.TypeParameters.Select (l => l.GetMetaInfo ()));
1970                                 }
1971
1972                                 definition = definition.GetDefinition ();
1973                                 type = type.DeclaringType;
1974                         } while (type != null);
1975
1976                         return definition.GetMetaInfo ().MakeGenericType (all.ToArray ());
1977                 }
1978
1979                 public override void CheckObsoleteness (IMemberContext mc, Location loc)
1980                 {
1981                         base.CheckObsoleteness (mc, loc);
1982
1983                         foreach (var ta in TypeArguments)
1984                                 ta.CheckObsoleteness (mc, loc);
1985                 }
1986
1987                 public override ObsoleteAttribute GetAttributeObsolete ()
1988                 {
1989                         return open_type.GetAttributeObsolete ();
1990                 }
1991
1992                 protected override bool IsNotCLSCompliant (out bool attrValue)
1993                 {
1994                         if (base.IsNotCLSCompliant (out attrValue))
1995                                 return true;
1996
1997                         foreach (var ta in TypeArguments) {
1998                                 if (ta.MemberDefinition.CLSAttributeValue == false)
1999                                         return true;
2000                         }
2001
2002                         return false;
2003                 }
2004
2005                 public override TypeSpec GetDefinition ()
2006                 {
2007                         return open_type;
2008                 }
2009
2010                 public override MetaType GetMetaInfo ()
2011                 {
2012                         if (info == null)
2013                                 info = CreateMetaInfo ();
2014
2015                         return info;
2016                 }
2017
2018                 public override string GetSignatureForError ()
2019                 {
2020                         if (IsNullableType)
2021                                 return targs[0].GetSignatureForError () + "?";
2022
2023                         return base.GetSignatureForError ();
2024                 }
2025
2026                 protected override string GetTypeNameSignature ()
2027                 {
2028                         if (targs.Length == 0 || MemberDefinition is AnonymousTypeClass)
2029                                 return null;
2030
2031                         return "<" + TypeManager.CSharpName (targs) + ">";
2032                 }
2033
2034                 public bool HasDynamicArgument ()
2035                 {
2036                         for (int i = 0; i < targs.Length; ++i) {
2037                                 var item = targs[i];
2038
2039                                 if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2040                                         return true;
2041
2042                                 if (item is InflatedTypeSpec) {
2043                                         if (((InflatedTypeSpec) item).HasDynamicArgument ())
2044                                                 return true;
2045
2046                                         continue;
2047                                 }
2048
2049                                 if (item.IsArray) {
2050                                         while (item.IsArray) {
2051                                                 item = ((ArrayContainer) item).Element;
2052                                         }
2053
2054                                         if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2055                                                 return true;
2056                                 }
2057                         }
2058
2059                         return false;
2060                 }
2061
2062                 protected override void InitializeMemberCache (bool onlyTypes)
2063                 {
2064                         if (cache == null) {
2065                                 var open_cache = onlyTypes ? open_type.MemberCacheTypes : open_type.MemberCache;
2066
2067                                 // Surprisingly, calling MemberCache on open type could meantime create cache on this type
2068                                 // for imported type parameter constraints referencing nested type of this declaration
2069                                 if (cache == null)
2070                                         cache = new MemberCache (open_cache);
2071                         }
2072
2073                         var inflator = CreateLocalInflator (context);
2074
2075                         //
2076                         // Two stage inflate due to possible nested types recursive
2077                         // references
2078                         //
2079                         // class A<T> {
2080                         //    B b;
2081                         //    class B {
2082                         //      T Value;
2083                         //    }
2084                         // }
2085                         //
2086                         // When resolving type of `b' members of `B' cannot be
2087                         // inflated because are not yet available in membercache
2088                         //
2089                         if ((state & StateFlags.PendingMemberCacheMembers) == 0) {
2090                                 open_type.MemberCacheTypes.InflateTypes (cache, inflator);
2091
2092                                 //
2093                                 // Inflate any implemented interfaces
2094                                 //
2095                                 if (open_type.Interfaces != null) {
2096                                         ifaces = new List<TypeSpec> (open_type.Interfaces.Count);
2097                                         foreach (var iface in open_type.Interfaces) {
2098                                                 var iface_inflated = inflator.Inflate (iface);
2099                                                 if (iface_inflated == null)
2100                                                         continue;
2101
2102                                                 base.AddInterface (iface_inflated);
2103                                         }
2104                                 }
2105
2106                                 //
2107                                 // Handles the tricky case of recursive nested base generic type
2108                                 //
2109                                 // class A<T> : Base<A<T>.Nested> {
2110                                 //    class Nested {}
2111                                 // }
2112                                 //
2113                                 // When inflating A<T>. base type is not yet known, secondary
2114                                 // inflation is required (not common case) once base scope
2115                                 // is known
2116                                 //
2117                                 if (open_type.BaseType == null) {
2118                                         if (IsClass)
2119                                                 state |= StateFlags.PendingBaseTypeInflate;
2120                                 } else {
2121                                         BaseType = inflator.Inflate (open_type.BaseType);
2122                                 }
2123                         } else if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2124                                 //
2125                                 // It can happen when resolving base type without being defined
2126                                 // which is not allowed to happen and will always lead to an error
2127                                 //
2128                                 // class B { class N {} }
2129                                 // class A<T> : A<B.N> {}
2130                                 //
2131                                 if (open_type.BaseType == null)
2132                                         return;
2133
2134                                 BaseType = inflator.Inflate (open_type.BaseType);
2135                                 state &= ~StateFlags.PendingBaseTypeInflate;
2136                         }
2137
2138                         if (onlyTypes) {
2139                                 state |= StateFlags.PendingMemberCacheMembers;
2140                                 return;
2141                         }
2142
2143                         var tc = open_type.MemberDefinition as TypeDefinition;
2144                         if (tc != null && !tc.HasMembersDefined) {
2145                                 //
2146                                 // Inflating MemberCache with undefined members
2147                                 //
2148                                 return;
2149                         }
2150
2151                         if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
2152                                 BaseType = inflator.Inflate (open_type.BaseType);
2153                                 state &= ~StateFlags.PendingBaseTypeInflate;
2154                         }
2155
2156                         state &= ~StateFlags.PendingMemberCacheMembers;
2157                         open_type.MemberCache.InflateMembers (cache, open_type, inflator);
2158                 }
2159
2160                 public override TypeSpec Mutate (TypeParameterMutator mutator)
2161                 {
2162                         var targs = TypeArguments;
2163                         if (targs != null)
2164                                 targs = mutator.Mutate (targs);
2165
2166                         var decl = DeclaringType;
2167                         if (IsNested && DeclaringType.IsGenericOrParentIsGeneric)
2168                                 decl = mutator.Mutate (decl);
2169
2170                         if (targs == TypeArguments && decl == DeclaringType)
2171                                 return this;
2172
2173                         var mutated = (InflatedTypeSpec) MemberwiseClone ();
2174 #if DEBUG
2175                         mutated.ID += 1000000;
2176 #endif
2177
2178                         if (decl != DeclaringType) {
2179                                 // Gets back MethodInfo in case of metaInfo was inflated
2180                                 //mutated.info = MemberCache.GetMember<TypeSpec> (DeclaringType.GetDefinition (), this).info;
2181
2182                                 mutated.declaringType = decl;
2183                                 mutated.state |= StateFlags.PendingMetaInflate;
2184                         }
2185
2186                         if (targs != null) {
2187                                 mutated.targs = targs;
2188                                 mutated.info = null;
2189                         }
2190
2191                         return mutated;
2192                 }
2193         }
2194
2195
2196         //
2197         // Tracks the type arguments when instantiating a generic type. It's used
2198         // by both type arguments and type parameters
2199         //
2200         public class TypeArguments
2201         {
2202                 List<FullNamedExpression> args;
2203                 TypeSpec[] atypes;
2204
2205                 public TypeArguments (params FullNamedExpression[] types)
2206                 {
2207                         this.args = new List<FullNamedExpression> (types);
2208                 }
2209
2210                 public void Add (FullNamedExpression type)
2211                 {
2212                         args.Add (type);
2213                 }
2214
2215                 /// <summary>
2216                 ///   We may only be used after Resolve() is called and return the fully
2217                 ///   resolved types.
2218                 /// </summary>
2219                 // TODO: Not needed, just return type from resolve
2220                 public TypeSpec[] Arguments {
2221                         get {
2222                                 return atypes;
2223                         }
2224                         set {
2225                                 atypes = value;
2226                         }
2227                 }
2228
2229                 public int Count {
2230                         get {
2231                                 return args.Count;
2232                         }
2233                 }
2234
2235                 public virtual bool IsEmpty {
2236                         get {
2237                                 return false;
2238                         }
2239                 }
2240
2241                 public List<FullNamedExpression> TypeExpressions {
2242                         get {
2243                                 return this.args;
2244                         }
2245                 }
2246
2247                 public string GetSignatureForError()
2248                 {
2249                         StringBuilder sb = new StringBuilder ();
2250                         for (int i = 0; i < Count; ++i) {
2251                                 var expr = args[i];
2252                                 if (expr != null)
2253                                         sb.Append (expr.GetSignatureForError ());
2254
2255                                 if (i + 1 < Count)
2256                                         sb.Append (',');
2257                         }
2258
2259                         return sb.ToString ();
2260                 }
2261
2262                 /// <summary>
2263                 ///   Resolve the type arguments.
2264                 /// </summary>
2265                 public virtual bool Resolve (IMemberContext ec, bool allowUnbound)
2266                 {
2267                         if (atypes != null)
2268                             return true;
2269
2270                         int count = args.Count;
2271                         bool ok = true;
2272
2273                         atypes = new TypeSpec [count];
2274
2275                         var errors = ec.Module.Compiler.Report.Errors;
2276
2277                         for (int i = 0; i < count; i++){
2278                                 var te = args[i].ResolveAsType (ec);
2279                                 if (te == null) {
2280                                         ok = false;
2281                                         continue;
2282                                 }
2283
2284                                 atypes[i] = te;
2285
2286                                 if (te.IsStatic) {
2287                                         ec.Module.Compiler.Report.Error (718, args[i].Location, "`{0}': static classes cannot be used as generic arguments",
2288                                                 te.GetSignatureForError ());
2289                                         ok = false;
2290                                 }
2291
2292                                 if (te.IsPointer || te.IsSpecialRuntimeType) {
2293                                         ec.Module.Compiler.Report.Error (306, args[i].Location,
2294                                                 "The type `{0}' may not be used as a type argument",
2295                                                 te.GetSignatureForError ());
2296                                         ok = false;
2297                                 }
2298                         }
2299
2300                         if (!ok || errors != ec.Module.Compiler.Report.Errors)
2301                                 atypes = null;
2302
2303                         return ok;
2304                 }
2305
2306                 public TypeArguments Clone ()
2307                 {
2308                         TypeArguments copy = new TypeArguments ();
2309                         foreach (var ta in args)
2310                                 copy.args.Add (ta);
2311
2312                         return copy;
2313                 }
2314         }
2315
2316         public class UnboundTypeArguments : TypeArguments
2317         {
2318                 Location loc;
2319
2320                 public UnboundTypeArguments (int arity, Location loc)
2321                         : base (new FullNamedExpression[arity])
2322                 {
2323                         this.loc = loc;
2324                 }
2325
2326                 public override bool IsEmpty {
2327                         get {
2328                                 return true;
2329                         }
2330                 }
2331
2332                 public override bool Resolve (IMemberContext mc, bool allowUnbound)
2333                 {
2334                         if (!allowUnbound) {
2335                                 mc.Module.Compiler.Report.Error (7003, loc, "Unbound generic name is not valid in this context");
2336                         }
2337
2338                         // Nothing to be resolved
2339                         return true;
2340                 }
2341         }
2342
2343         public class TypeParameters
2344         {
2345                 List<TypeParameter> names;
2346                 TypeParameterSpec[] types;
2347
2348                 public TypeParameters ()
2349                 {
2350                         names = new List<TypeParameter> ();
2351                 }
2352
2353                 public TypeParameters (int count)
2354                 {
2355                         names = new List<TypeParameter> (count);
2356                 }
2357
2358                 #region Properties
2359
2360                 public int Count {
2361                         get {
2362                                 return names.Count;
2363                         }
2364                 }
2365
2366                 public TypeParameterSpec[] Types {
2367                         get {
2368                                 return types;
2369                         }
2370                 }
2371
2372                 #endregion
2373
2374                 public void Add (TypeParameter tparam)
2375                 {
2376                         names.Add (tparam);
2377                 }
2378
2379                 public void Add (TypeParameters tparams)
2380                 {
2381                         names.AddRange (tparams.names);
2382                 }
2383
2384                 public void Create (TypeSpec declaringType, int parentOffset, TypeContainer parent)
2385                 {
2386                         types = new TypeParameterSpec[Count];
2387                         for (int i = 0; i < types.Length; ++i) {
2388                                 var tp = names[i];
2389
2390                                 tp.Create (declaringType, parent);
2391                                 types[i] = tp.Type;
2392                                 types[i].DeclaredPosition = i + parentOffset;
2393
2394                                 if (tp.Variance != Variance.None && !(declaringType != null && (declaringType.Kind == MemberKind.Interface || declaringType.Kind == MemberKind.Delegate))) {
2395                                         parent.Compiler.Report.Error (1960, tp.Location, "Variant type parameters can only be used with interfaces and delegates");
2396                                 }
2397                         }
2398                 }
2399
2400                 public void Define (GenericTypeParameterBuilder[] builders)
2401                 {
2402                         for (int i = 0; i < types.Length; ++i) {
2403                                 var tp = names[i];
2404                                 tp.Define (builders [types [i].DeclaredPosition]);
2405                         }
2406                 }
2407
2408                 public TypeParameter this[int index] {
2409                         get {
2410                                 return names [index];
2411                         }
2412                         set {
2413                                 names[index] = value;
2414                         }
2415                 }
2416
2417                 public TypeParameter Find (string name)
2418                 {
2419                         foreach (var tp in names) {
2420                                 if (tp.Name == name)
2421                                         return tp;
2422                         }
2423
2424                         return null;
2425                 }
2426
2427                 public string[] GetAllNames ()
2428                 {
2429                         return names.Select (l => l.Name).ToArray ();
2430                 }
2431
2432                 public string GetSignatureForError ()
2433                 {
2434                         StringBuilder sb = new StringBuilder ();
2435                         for (int i = 0; i < Count; ++i) {
2436                                 if (i > 0)
2437                                         sb.Append (',');
2438
2439                                 var name = names[i];
2440                                 if (name != null)
2441                                         sb.Append (name.GetSignatureForError ());
2442                         }
2443
2444                         return sb.ToString ();
2445                 }
2446
2447
2448                 public void CheckPartialConstraints (Method part)
2449                 {
2450                         var partTypeParameters = part.CurrentTypeParameters;
2451
2452                         for (int i = 0; i < Count; i++) {
2453                                 var tp_a = names[i];
2454                                 var tp_b = partTypeParameters [i];
2455                                 if (tp_a.Constraints == null) {
2456                                         if (tp_b.Constraints == null)
2457                                                 continue;
2458                                 } else if (tp_b.Constraints != null && tp_a.Type.HasSameConstraintsDefinition (tp_b.Type)) {
2459                                         continue;
2460                                 }
2461
2462                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition.Location, "");
2463                                 part.Compiler.Report.Error (761, part.Location,
2464                                         "Partial method declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2465                                         part.GetSignatureForError (), partTypeParameters[i].GetSignatureForError ());
2466                         }
2467                 }
2468
2469                 public void UpdateConstraints (TypeDefinition part)
2470                 {
2471                         var partTypeParameters = part.MemberName.TypeParameters;
2472
2473                         for (int i = 0; i < Count; i++) {
2474                                 var tp = names [i];
2475                                 if (tp.AddPartialConstraints (part, partTypeParameters [i]))
2476                                         continue;
2477
2478                                 part.Compiler.Report.SymbolRelatedToPreviousError (this[i].CurrentMemberDefinition);
2479                                 part.Compiler.Report.Error (265, part.Location,
2480                                         "Partial declarations of `{0}' have inconsistent constraints for type parameter `{1}'",
2481                                         part.GetSignatureForError (), tp.GetSignatureForError ());
2482                         }
2483                 }
2484
2485                 public void VerifyClsCompliance ()
2486                 {
2487                         foreach (var tp in names) {
2488                                 tp.VerifyClsCompliance ();
2489                         }
2490                 }
2491         }
2492
2493         //
2494         // A type expression of generic type with type arguments
2495         //
2496         class GenericTypeExpr : TypeExpr
2497         {
2498                 TypeArguments args;
2499                 TypeSpec open_type;
2500
2501                 /// <summary>
2502                 ///   Instantiate the generic type `t' with the type arguments `args'.
2503                 ///   Use this constructor if you already know the fully resolved
2504                 ///   generic type.
2505                 /// </summary>
2506                 public GenericTypeExpr (TypeSpec open_type, TypeArguments args, Location l)
2507                 {
2508                         this.open_type = open_type;
2509                         loc = l;
2510                         this.args = args;
2511                 }
2512
2513                 public override string GetSignatureForError ()
2514                 {
2515                         return type.GetSignatureForError ();
2516                 }
2517
2518                 public override TypeSpec ResolveAsType (IMemberContext mc, bool allowUnboundTypeArguments = false)
2519                 {
2520                         if (eclass != ExprClass.Unresolved)
2521                                 return type;
2522
2523                         if (!args.Resolve (mc, allowUnboundTypeArguments))
2524                                 return null;
2525
2526                         TypeSpec[] atypes = args.Arguments;
2527                         if (atypes == null)
2528                                 return null;
2529
2530                         //
2531                         // Now bind the parameters
2532                         //
2533                         var inflated = open_type.MakeGenericType (mc, atypes);
2534                         type = inflated;
2535                         eclass = ExprClass.Type;
2536
2537                         //
2538                         // The constraints can be checked only when full type hierarchy is known
2539                         //
2540                         if (!inflated.HasConstraintsChecked && mc.Module.HasTypesFullyDefined) {
2541                                 var constraints = inflated.Constraints;
2542                                 if (constraints != null) {
2543                                         var cc = new ConstraintChecker (mc);
2544                                         if (cc.CheckAll (open_type, atypes, constraints, loc)) {
2545                                                 inflated.HasConstraintsChecked = true;
2546                                         }
2547                                 }
2548                         }
2549
2550                         return type;
2551                 }
2552
2553                 public override bool Equals (object obj)
2554                 {
2555                         GenericTypeExpr cobj = obj as GenericTypeExpr;
2556                         if (cobj == null)
2557                                 return false;
2558
2559                         if ((type == null) || (cobj.type == null))
2560                                 return false;
2561
2562                         return type == cobj.type;
2563                 }
2564
2565                 public override int GetHashCode ()
2566                 {
2567                         return base.GetHashCode ();
2568                 }
2569         }
2570
2571         //
2572         // Generic type with unbound type arguments, used for typeof (G<,,>)
2573         //
2574         class GenericOpenTypeExpr : TypeExpression
2575         {
2576                 public GenericOpenTypeExpr (TypeSpec type, /*UnboundTypeArguments args,*/ Location loc)
2577                         : base (type.GetDefinition (), loc)
2578                 {
2579                 }
2580         }
2581
2582         struct ConstraintChecker
2583         {
2584                 IMemberContext mc;
2585                 bool recursive_checks;
2586
2587                 public ConstraintChecker (IMemberContext ctx)
2588                 {
2589                         this.mc = ctx;
2590                         recursive_checks = false;
2591                 }
2592
2593                 //
2594                 // Checks the constraints of open generic type against type
2595                 // arguments. This version is used for types which could not be
2596                 // checked immediatelly during construction because the type
2597                 // hierarchy was not yet fully setup (before Emit phase)
2598                 //
2599                 public static bool Check (IMemberContext mc, TypeSpec type, Location loc)
2600                 {
2601                         //
2602                         // Check declaring type first if there is any
2603                         //
2604                         if (type.DeclaringType != null && !Check (mc, type.DeclaringType, loc))
2605                                 return false;
2606
2607                         while (type is ElementTypeSpec)
2608                                 type = ((ElementTypeSpec) type).Element;
2609
2610                         if (type.Arity == 0)
2611                                 return true;
2612
2613                         var gtype = type as InflatedTypeSpec;
2614                         if (gtype == null)
2615                                 return true;
2616
2617                         var constraints = gtype.Constraints;
2618                         if (constraints == null)
2619                                 return true;
2620
2621                         if (gtype.HasConstraintsChecked)
2622                                 return true;
2623
2624                         var cc = new ConstraintChecker (mc);
2625                         cc.recursive_checks = true;
2626
2627                         if (cc.CheckAll (gtype.GetDefinition (), type.TypeArguments, constraints, loc)) {
2628                                 gtype.HasConstraintsChecked = true;
2629                                 return true;
2630                         }
2631
2632                         return false;
2633                 }
2634
2635                 //
2636                 // Checks all type arguments againts type parameters constraints
2637                 // NOTE: It can run in probing mode when `this.mc' is null
2638                 //
2639                 public bool CheckAll (MemberSpec context, TypeSpec[] targs, TypeParameterSpec[] tparams, Location loc)
2640                 {
2641                         if (targs == null)
2642                                 return true;
2643
2644                         for (int i = 0; i < tparams.Length; i++) {
2645                                 var targ = targs[i];
2646                                 if (!CheckConstraint (context, targ, tparams [i], loc))
2647                                         return false;
2648
2649                                 if (!recursive_checks)
2650                                         continue;
2651
2652                                 if (!Check (mc, targ, loc))
2653                                         return false;
2654                         }
2655
2656                         return true;
2657                 }
2658
2659                 bool CheckConstraint (MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, Location loc)
2660                 {
2661                         //
2662                         // First, check the `class' and `struct' constraints.
2663                         //
2664                         if (tparam.HasSpecialClass && !TypeSpec.IsReferenceType (atype)) {
2665                                 if (mc != null) {
2666                                         mc.Module.Compiler.Report.Error (452, loc,
2667                                                 "The type `{0}' must be a reference type in order to use it as type parameter `{1}' in the generic type or method `{2}'",
2668                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2669                                 }
2670
2671                                 return false;
2672                         }
2673
2674                         if (tparam.HasSpecialStruct && (!TypeSpec.IsValueType (atype) || atype.IsNullableType)) {
2675                                 if (mc != null) {
2676                                         mc.Module.Compiler.Report.Error (453, loc,
2677                                                 "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}'",
2678                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2679                                 }
2680
2681                                 return false;
2682                         }
2683
2684                         bool ok = true;
2685
2686                         //
2687                         // Check the class constraint
2688                         //
2689                         if (tparam.HasTypeConstraint) {
2690                                 if (!CheckConversion (mc, context, atype, tparam, tparam.BaseType, loc)) {
2691                                         if (mc == null)
2692                                                 return false;
2693
2694                                         ok = false;
2695                                 }
2696                         }
2697
2698                         //
2699                         // Check the interfaces constraints
2700                         //
2701                         if (tparam.InterfacesDefined != null) {
2702                                 foreach (TypeSpec iface in tparam.InterfacesDefined) {
2703                                         if (!CheckConversion (mc, context, atype, tparam, iface, loc)) {
2704                                                 if (mc == null)
2705                                                         return false;
2706
2707                                                 ok = false;
2708                                                 break;
2709                                         }
2710                                 }
2711                         }
2712
2713                         //
2714                         // Check the type parameter constraint
2715                         //
2716                         if (tparam.TypeArguments != null) {
2717                                 foreach (var ta in tparam.TypeArguments) {
2718                                         if (!CheckConversion (mc, context, atype, tparam, ta, loc)) {
2719                                                 if (mc == null)
2720                                                         return false;
2721
2722                                                 ok = false;
2723                                                 break;
2724                                         }
2725                                 }
2726                         }
2727
2728                         //
2729                         // Finally, check the constructor constraint.
2730                         //
2731                         if (!tparam.HasSpecialConstructor)
2732                                 return ok;
2733
2734                         if (!HasDefaultConstructor (atype)) {
2735                                 if (mc != null) {
2736                                         mc.Module.Compiler.Report.SymbolRelatedToPreviousError (atype);
2737                                         mc.Module.Compiler.Report.Error (310, loc,
2738                                                 "The type `{0}' must have a public parameterless constructor in order to use it as parameter `{1}' in the generic type or method `{2}'",
2739                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
2740                                 }
2741                                 return false;
2742                         }
2743
2744                         return ok;
2745                 }
2746
2747                 static bool HasDynamicTypeArgument (TypeSpec[] targs)
2748                 {
2749                         for (int i = 0; i < targs.Length; ++i) {
2750                                 var targ = targs [i];
2751                                 if (targ.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
2752                                         return true;
2753
2754                                 if (HasDynamicTypeArgument (targ.TypeArguments))
2755                                         return true;
2756                         }
2757
2758                         return false;
2759                 }
2760
2761                 bool CheckConversion (IMemberContext mc, MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, TypeSpec ttype, Location loc)
2762                 {
2763                         if (atype == ttype)
2764                                 return true;
2765
2766                         if (atype.IsGenericParameter) {
2767                                 var tps = (TypeParameterSpec) atype;
2768                                 if (tps.HasDependencyOn (ttype))
2769                                         return true;
2770
2771                                 if (Convert.ImplicitTypeParameterConversion (null, tps, ttype) != null)
2772                                         return true;
2773
2774                         } else if (TypeSpec.IsValueType (atype)) {
2775                                 if (atype.IsNullableType) {
2776                                         //
2777                                         // LAMESPEC: Only identity or base type ValueType or Object satisfy nullable type
2778                                         //
2779                                         if (TypeSpec.IsBaseClass (atype, ttype, false))
2780                                                 return true;
2781                                 } else {
2782                                         if (Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2783                                                 return true;
2784                                 }
2785                         } else {
2786                                 if (Convert.ImplicitReferenceConversionExists (atype, ttype) || Convert.ImplicitBoxingConversion (null, atype, ttype) != null)
2787                                         return true;
2788                         }
2789
2790                         if (mc != null) {
2791                                 mc.Module.Compiler.Report.SymbolRelatedToPreviousError (tparam);
2792                                 if (atype.IsGenericParameter) {
2793                                         mc.Module.Compiler.Report.Error (314, loc,
2794                                                 "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}'",
2795                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2796                                 } else if (TypeSpec.IsValueType (atype)) {
2797                                         if (atype.IsNullableType) {
2798                                                 if (ttype.IsInterface) {
2799                                                         mc.Module.Compiler.Report.Error (313, loc,
2800                                                                 "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}'",
2801                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2802                                                 } else {
2803                                                         mc.Module.Compiler.Report.Error (312, loc,
2804                                                                 "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}'",
2805                                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2806                                                 }
2807                                         } else {
2808                                                 mc.Module.Compiler.Report.Error (315, loc,
2809                                                         "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}'",
2810                                                         atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2811                                         }
2812                                 } else {
2813                                         mc.Module.Compiler.Report.Error (311, loc,
2814                                                 "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}'",
2815                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
2816                                 }
2817                         }
2818
2819                         return false;
2820                 }
2821
2822                 static bool HasDefaultConstructor (TypeSpec atype)
2823                 {
2824                         var tp = atype as TypeParameterSpec;
2825                         if (tp != null) {
2826                                 return tp.HasSpecialConstructor || tp.HasSpecialStruct;
2827                         }
2828
2829                         if (atype.IsStruct || atype.IsEnum)
2830                                 return true;
2831
2832                         if (atype.IsAbstract)
2833                                 return false;
2834
2835                         var tdef = atype.GetDefinition ();
2836
2837                         var found = MemberCache.FindMember (tdef,
2838                                 MemberFilter.Constructor (ParametersCompiled.EmptyReadOnlyParameters),
2839                                 BindingRestriction.DeclaredOnly | BindingRestriction.InstanceOnly);
2840
2841                         return found != null && (found.Modifiers & Modifiers.PUBLIC) != 0;
2842                 }
2843         }
2844
2845         //
2846         // Implements C# type inference
2847         //
2848         class TypeInference
2849         {
2850                 //
2851                 // Tracks successful rate of type inference
2852                 //
2853                 int score;
2854                 readonly Arguments arguments;
2855                 readonly int arg_count;
2856
2857                 public TypeInference (Arguments arguments)
2858                 {
2859                         this.arguments = arguments;
2860                         if (arguments != null)
2861                                 arg_count = arguments.Count;
2862                 }
2863
2864                 public int InferenceScore {
2865                         get {
2866                                 return score;
2867                         }
2868                 }
2869
2870                 public TypeSpec[] InferMethodArguments (ResolveContext ec, MethodSpec method)
2871                 {
2872                         var method_generic_args = method.GenericDefinition.TypeParameters;
2873                         TypeInferenceContext context = new TypeInferenceContext (method_generic_args);
2874                         if (!context.UnfixedVariableExists)
2875                                 return TypeSpec.EmptyTypes;
2876
2877                         AParametersCollection pd = method.Parameters;
2878                         if (!InferInPhases (ec, context, pd))
2879                                 return null;
2880
2881                         return context.InferredTypeArguments;
2882                 }
2883
2884                 //
2885                 // Implements method type arguments inference
2886                 //
2887                 bool InferInPhases (ResolveContext ec, TypeInferenceContext tic, AParametersCollection methodParameters)
2888                 {
2889                         int params_arguments_start;
2890                         if (methodParameters.HasParams) {
2891                                 params_arguments_start = methodParameters.Count - 1;
2892                         } else {
2893                                 params_arguments_start = arg_count;
2894                         }
2895
2896                         TypeSpec [] ptypes = methodParameters.Types;
2897
2898                         //
2899                         // The first inference phase
2900                         //
2901                         TypeSpec method_parameter = null;
2902                         for (int i = 0; i < arg_count; i++) {
2903                                 Argument a = arguments [i];
2904                                 if (a == null)
2905                                         continue;
2906
2907                                 if (i < params_arguments_start) {
2908                                         method_parameter = methodParameters.Types [i];
2909                                 } else if (i == params_arguments_start) {
2910                                         if (arg_count == params_arguments_start + 1 && TypeManager.HasElementType (a.Type))
2911                                                 method_parameter = methodParameters.Types [params_arguments_start];
2912                                         else
2913                                                 method_parameter = TypeManager.GetElementType (methodParameters.Types [params_arguments_start]);
2914
2915                                         ptypes = (TypeSpec[]) ptypes.Clone ();
2916                                         ptypes [i] = method_parameter;
2917                                 }
2918
2919                                 //
2920                                 // When a lambda expression, an anonymous method
2921                                 // is used an explicit argument type inference takes a place
2922                                 //
2923                                 AnonymousMethodExpression am = a.Expr as AnonymousMethodExpression;
2924                                 if (am != null) {
2925                                         if (am.ExplicitTypeInference (tic, method_parameter))
2926                                                 ++score;
2927                                         continue;
2928                                 }
2929
2930                                 if (a.IsByRef) {
2931                                         score += tic.ExactInference (a.Type, method_parameter);
2932                                         continue;
2933                                 }
2934
2935                                 if (a.Expr.Type == InternalType.NullLiteral)
2936                                         continue;
2937
2938                                 if (TypeSpec.IsValueType (method_parameter)) {
2939                                         score += tic.LowerBoundInference (a.Type, method_parameter);
2940                                         continue;
2941                                 }
2942
2943                                 //
2944                                 // Otherwise an output type inference is made
2945                                 //
2946                                 score += tic.OutputTypeInference (ec, a.Expr, method_parameter);
2947                         }
2948
2949                         //
2950                         // Part of the second phase but because it happens only once
2951                         // we don't need to call it in cycle
2952                         //
2953                         bool fixed_any = false;
2954                         if (!tic.FixIndependentTypeArguments (ec, ptypes, ref fixed_any))
2955                                 return false;
2956
2957                         return DoSecondPhase (ec, tic, ptypes, !fixed_any);
2958                 }
2959
2960                 bool DoSecondPhase (ResolveContext ec, TypeInferenceContext tic, TypeSpec[] methodParameters, bool fixDependent)
2961                 {
2962                         bool fixed_any = false;
2963                         if (fixDependent && !tic.FixDependentTypes (ec, ref fixed_any))
2964                                 return false;
2965
2966                         // If no further unfixed type variables exist, type inference succeeds
2967                         if (!tic.UnfixedVariableExists)
2968                                 return true;
2969
2970                         if (!fixed_any && fixDependent)
2971                                 return false;
2972
2973                         // For all arguments where the corresponding argument output types
2974                         // contain unfixed type variables but the input types do not,
2975                         // an output type inference is made
2976                         for (int i = 0; i < arg_count; i++) {
2977
2978                                 // Align params arguments
2979                                 TypeSpec t_i = methodParameters [i >= methodParameters.Length ? methodParameters.Length - 1: i];
2980
2981                                 if (!t_i.IsDelegate) {
2982                                         if (!t_i.IsExpressionTreeType)
2983                                                 continue;
2984
2985                                         t_i = TypeManager.GetTypeArguments (t_i) [0];
2986                                 }
2987
2988                                 var mi = Delegate.GetInvokeMethod (t_i);
2989                                 TypeSpec rtype = mi.ReturnType;
2990
2991                                 if (tic.IsReturnTypeNonDependent (mi, rtype)) {
2992                                         // It can be null for default arguments
2993                                         if (arguments[i] == null)
2994                                                 continue;
2995
2996                                         score += tic.OutputTypeInference (ec, arguments[i].Expr, t_i);
2997                                 }
2998                         }
2999
3000
3001                         return DoSecondPhase (ec, tic, methodParameters, true);
3002                 }
3003         }
3004
3005         public class TypeInferenceContext
3006         {
3007                 protected enum BoundKind
3008                 {
3009                         Exact   = 0,
3010                         Lower   = 1,
3011                         Upper   = 2
3012                 }
3013
3014                 struct BoundInfo : IEquatable<BoundInfo>
3015                 {
3016                         public readonly TypeSpec Type;
3017                         public readonly BoundKind Kind;
3018
3019                         public BoundInfo (TypeSpec type, BoundKind kind)
3020                         {
3021                                 this.Type = type;
3022                                 this.Kind = kind;
3023                         }
3024
3025                         public override int GetHashCode ()
3026                         {
3027                                 return Type.GetHashCode ();
3028                         }
3029
3030                         public Expression GetTypeExpression ()
3031                         {
3032                                 return new TypeExpression (Type, Location.Null);
3033                         }
3034
3035                         #region IEquatable<BoundInfo> Members
3036
3037                         public bool Equals (BoundInfo other)
3038                         {
3039                                 return Type == other.Type && Kind == other.Kind;
3040                         }
3041
3042                         #endregion
3043                 }
3044
3045                 readonly TypeSpec[] tp_args;
3046                 readonly TypeSpec[] fixed_types;
3047                 readonly List<BoundInfo>[] bounds;
3048
3049                 // TODO MemberCache: Could it be TypeParameterSpec[] ??
3050                 public TypeInferenceContext (TypeSpec[] typeArguments)
3051                 {
3052                         if (typeArguments.Length == 0)
3053                                 throw new ArgumentException ("Empty generic arguments");
3054
3055                         fixed_types = new TypeSpec [typeArguments.Length];
3056                         for (int i = 0; i < typeArguments.Length; ++i) {
3057                                 if (typeArguments [i].IsGenericParameter) {
3058                                         if (bounds == null) {
3059                                                 bounds = new List<BoundInfo> [typeArguments.Length];
3060                                                 tp_args = new TypeSpec [typeArguments.Length];
3061                                         }
3062                                         tp_args [i] = typeArguments [i];
3063                                 } else {
3064                                         fixed_types [i] = typeArguments [i];
3065                                 }
3066                         }
3067                 }
3068
3069                 //
3070                 // Used together with AddCommonTypeBound fo implement
3071                 // 7.4.2.13 Finding the best common type of a set of expressions
3072                 //
3073                 public TypeInferenceContext ()
3074                 {
3075                         fixed_types = new TypeSpec [1];
3076                         tp_args = new TypeSpec [1];
3077                         tp_args[0] = InternalType.Arglist; // it can be any internal type
3078                         bounds = new List<BoundInfo> [1];
3079                 }
3080
3081                 public TypeSpec[] InferredTypeArguments {
3082                         get {
3083                                 return fixed_types;
3084                         }
3085                 }
3086
3087                 public void AddCommonTypeBound (TypeSpec type)
3088                 {
3089                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, false);
3090                 }
3091
3092                 public void AddCommonTypeBoundAsync (TypeSpec type)
3093                 {
3094                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0, true);
3095                 }
3096
3097                 void AddToBounds (BoundInfo bound, int index, bool voidAllowed)
3098                 {
3099                         //
3100                         // Some types cannot be used as type arguments
3101                         //
3102                         if ((bound.Type.Kind == MemberKind.Void && !voidAllowed) || bound.Type.IsPointer || bound.Type.IsSpecialRuntimeType ||
3103                             bound.Type == InternalType.MethodGroup || bound.Type == InternalType.AnonymousMethod || bound.Type == InternalType.VarOutType ||
3104                             bound.Type == InternalType.ThrowExpr)
3105                                 return;
3106
3107                         if (bound.Type.IsTupleType && TupleLiteral.ContainsNoTypeElement (bound.Type))
3108                                 return;
3109
3110                         var a = bounds [index];
3111                         if (a == null) {
3112                                 a = new List<BoundInfo> (2);
3113                                 a.Add (bound);
3114                                 bounds [index] = a;
3115                                 return;
3116                         }
3117
3118                         if (a.Contains (bound))
3119                                 return;
3120
3121                         a.Add (bound);
3122                 }
3123
3124                 bool AllTypesAreFixed (TypeSpec[] types)
3125                 {
3126                         foreach (TypeSpec t in types) {
3127                                 if (t.IsGenericParameter) {
3128                                         if (!IsFixed (t))
3129                                                 return false;
3130                                         continue;
3131                                 }
3132
3133                                 if (t.IsGeneric && !AllTypesAreFixed (t.TypeArguments))
3134                                         return false;
3135                         }
3136
3137                         return true;
3138                 }
3139
3140                 //
3141                 // 26.3.3.8 Exact Inference
3142                 //
3143                 public int ExactInference (TypeSpec u, TypeSpec v)
3144                 {
3145                         // If V is an array type
3146                         if (v.IsArray) {
3147                                 if (!u.IsArray)
3148                                         return 0;
3149
3150                                 var ac_u = (ArrayContainer) u;
3151                                 var ac_v = (ArrayContainer) v;
3152                                 if (ac_u.Rank != ac_v.Rank)
3153                                         return 0;
3154
3155                                 return ExactInference (ac_u.Element, ac_v.Element);
3156                         }
3157
3158                         //
3159                         // If V is constructed type and U is constructed type or dynamic
3160                         //
3161                         if (TypeManager.IsGenericType (v)) {
3162                                 if (u.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
3163
3164                                         var ga_v = v.TypeArguments;
3165
3166                                         int score = 0;
3167                                         for (int i = 0; i < ga_v.Length; ++i)
3168                                                 score += ExactInference (u, ga_v [i]);
3169
3170                                         return System.Math.Min (1, score);
3171
3172                                 } else {
3173                                         if (!TypeManager.IsGenericType (u) || v.MemberDefinition != u.MemberDefinition)
3174                                                 return 0;
3175
3176                                         var ga_u = u.TypeArguments;
3177                                         var ga_v = v.TypeArguments;
3178
3179                                         if (u.TypeArguments.Length != v.TypeArguments.Length)
3180                                                 return 0;
3181
3182                                         int score = 0;
3183                                         for (int i = 0; i < ga_v.Length; ++i)
3184                                                 score += ExactInference (ga_u [i], ga_v [i]);
3185
3186                                         return System.Math.Min (1, score);
3187                                 }
3188                         }
3189
3190                         // If V is one of the unfixed type arguments
3191                         int pos = IsUnfixed (v);
3192                         if (pos == -1)
3193                                 return 0;
3194
3195                         AddToBounds (new BoundInfo (u, BoundKind.Exact), pos, false);
3196                         return 1;
3197                 }
3198
3199                 public bool FixAllTypes (ResolveContext ec)
3200                 {
3201                         for (int i = 0; i < tp_args.Length; ++i) {
3202                                 if (!FixType (ec, i))
3203                                         return false;
3204                         }
3205                         return true;
3206                 }
3207
3208                 //
3209                 // All unfixed type variables Xi are fixed for which all of the following hold:
3210                 // a, There is at least one type variable Xj that depends on Xi
3211                 // b, Xi has a non-empty set of bounds
3212                 //
3213                 public bool FixDependentTypes (ResolveContext ec, ref bool fixed_any)
3214                 {
3215                         for (int i = 0; i < tp_args.Length; ++i) {
3216                                 if (fixed_types[i] != null)
3217                                         continue;
3218
3219                                 if (bounds[i] == null)
3220                                         continue;
3221
3222                                 if (!FixType (ec, i))
3223                                         return false;
3224
3225                                 fixed_any = true;
3226                         }
3227
3228                         return true;
3229                 }
3230
3231                 //
3232                 // All unfixed type variables Xi which depend on no Xj are fixed
3233                 //
3234                 public bool FixIndependentTypeArguments (ResolveContext ec, TypeSpec[] methodParameters, ref bool fixed_any)
3235                 {
3236                         var types_to_fix = new List<TypeSpec> (tp_args);
3237                         for (int i = 0; i < methodParameters.Length; ++i) {
3238                                 TypeSpec t = methodParameters[i];
3239
3240                                 if (!t.IsDelegate) {
3241                                         if (!t.IsExpressionTreeType)
3242                                                 continue;
3243
3244                                         t =  TypeManager.GetTypeArguments (t) [0];
3245                                 }
3246
3247                                 if (t.IsGenericParameter)
3248                                         continue;
3249
3250                                 var invoke = Delegate.GetInvokeMethod (t);
3251                                 TypeSpec rtype = invoke.ReturnType;
3252                                 while (rtype.IsArray)
3253                                         rtype = ((ArrayContainer) rtype).Element;
3254
3255                                 if (!rtype.IsGenericParameter && !TypeManager.IsGenericType (rtype))
3256                                         continue;
3257
3258                                 // Remove dependent types, they cannot be fixed yet
3259                                 RemoveDependentTypes (types_to_fix, rtype);
3260                         }
3261
3262                         foreach (TypeSpec t in types_to_fix) {
3263                                 if (t == null)
3264                                         continue;
3265
3266                                 int idx = IsUnfixed (t);
3267                                 if (idx >= 0 && !FixType (ec, idx)) {
3268                                         return false;
3269                                 }
3270                         }
3271
3272                         fixed_any = types_to_fix.Count > 0;
3273                         return true;
3274                 }
3275
3276                 //
3277                 // 26.3.3.10 Fixing
3278                 //
3279                 public bool FixType (ResolveContext ec, int i)
3280                 {
3281                         // It's already fixed
3282                         if (fixed_types[i] != null)
3283                                 throw new InternalErrorException ("Type argument has been already fixed");
3284
3285                         var candidates = bounds [i];
3286                         if (candidates == null)
3287                                 return false;
3288
3289                         if (candidates.Count == 1) {
3290                                 TypeSpec t = candidates[0].Type;
3291                                 if (t == InternalType.NullLiteral)
3292                                         return false;
3293
3294                                 fixed_types [i] = t;
3295                                 return true;
3296                         }
3297
3298                         //
3299                         // The set of candidate types Uj starts out as the set of
3300                         // all types in the set of bounds for Xi
3301                         //
3302                         var applicable = new bool [candidates.Count];
3303                         for (int ci = 0; ci < applicable.Length; ++ci)
3304                                 applicable [ci] = true;
3305
3306                         for (int ci = 0; ci < applicable.Length; ++ci) {
3307                                 var bound = candidates [ci];
3308                                 int cii = 0;
3309
3310                                 switch (bound.Kind) {
3311                                 case BoundKind.Exact:
3312                                         for (; cii != applicable.Length; ++cii) {
3313                                                 if (ci == cii)
3314                                                         continue;
3315
3316                                                 if (!applicable[cii])
3317                                                         continue;
3318
3319                                                 //
3320                                                 // For each exact bound U of Xi all types Uj which are not identical
3321                                                 // to U are removed from the candidate set
3322                                                 //
3323                                                 if (candidates [cii].Type != bound.Type)
3324                                                         applicable[cii] = false;
3325                                         }
3326
3327                                         break;
3328                                 case BoundKind.Lower:
3329                                         for (; cii != applicable.Length; ++cii) {
3330                                                 if (ci == cii)
3331                                                         continue;
3332
3333                                                 if (!applicable[cii])
3334                                                         continue;
3335
3336                                                 //
3337                                                 // For each lower bound U of Xi all types Uj to which there is not an implicit conversion
3338                                                 // from U are removed from the candidate set
3339                                                 //
3340                                                 if (!Convert.ImplicitConversionExists (ec, bound.GetTypeExpression (), candidates [cii].Type)) {
3341                                                         applicable[cii] = false;
3342                                                 }
3343                                         }
3344
3345                                         break;
3346
3347                                 case BoundKind.Upper:
3348                                         for (; cii != applicable.Length; ++cii) {
3349                                                 if (ci == cii)
3350                                                         continue;
3351
3352                                                 if (!applicable[cii])
3353                                                         continue;
3354
3355                                                 //
3356                                                 // For each upper bound U of Xi all types Uj from which there is not an implicit conversion
3357                                                 // to U are removed from the candidate set
3358                                                 //
3359                                                 if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3360                                                         applicable[cii] = false;
3361                                         }
3362
3363                                         break;
3364                                 }
3365                         }
3366
3367                         TypeSpec best_candidate = null;
3368                         for (int ci = 0; ci < applicable.Length; ++ci) {
3369                                 if (!applicable[ci])
3370                                         continue;
3371
3372                                 var bound = candidates [ci];
3373                                 if (bound.Type == best_candidate)
3374                                         continue;
3375
3376                                 int cii = 0;
3377                                 for (; cii < applicable.Length; ++cii) {
3378                                         if (ci == cii)
3379                                                 continue;
3380
3381                                         if (!applicable[cii])
3382                                                 continue;
3383
3384                                         if (!Convert.ImplicitConversionExists (ec, candidates[cii].GetTypeExpression (), bound.Type))
3385                                                 break;
3386                                 }
3387
3388                                 if (cii != applicable.Length)
3389                                         continue;
3390
3391                                 //
3392                                 // We already have the best candidate, break if it's different (non-unique)
3393                                 //
3394                                 // Dynamic is never ambiguous as we prefer dynamic over other best candidate types
3395                                 //
3396                                 if (best_candidate != null) {
3397
3398                                         if (best_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3399                                                 continue;
3400
3401                                         if (bound.Type.BuiltinType != BuiltinTypeSpec.Type.Dynamic && best_candidate != bound.Type)
3402                                                 return false;
3403                                 }
3404
3405                                 best_candidate = bound.Type;
3406                         }
3407
3408                         if (best_candidate == null)
3409                                 return false;
3410
3411                         fixed_types[i] = best_candidate;
3412                         return true;
3413                 }
3414
3415                 public bool HasBounds (int pos)
3416                 {
3417                         return bounds[pos] != null;
3418                 }
3419
3420                 //
3421                 // Uses inferred or partially infered types to inflate delegate type argument. Returns
3422                 // null when type parameter has not been fixed
3423                 //
3424                 public TypeSpec InflateGenericArgument (IModuleContext context, TypeSpec parameter)
3425                 {
3426                         var tp = parameter as TypeParameterSpec;
3427                         if (tp != null) {
3428                                 //
3429                                 // Type inference works on generic arguments (MVAR) only
3430                                 //
3431                                 if (!tp.IsMethodOwned)
3432                                         return parameter;
3433
3434                                 //
3435                                 // Ensure the type parameter belongs to same container
3436                                 //
3437                                 if (tp.DeclaredPosition < tp_args.Length && tp_args[tp.DeclaredPosition] == parameter)
3438                                         return fixed_types[tp.DeclaredPosition] ?? parameter;
3439
3440                                 return parameter;
3441                         }
3442
3443                         var gt = parameter as InflatedTypeSpec;
3444                         if (gt != null) {
3445                                 var inflated_targs = new TypeSpec [gt.TypeArguments.Length];
3446                                 for (int ii = 0; ii < inflated_targs.Length; ++ii) {
3447                                         var inflated = InflateGenericArgument (context, gt.TypeArguments [ii]);
3448                                         if (inflated == null)
3449                                                 return null;
3450
3451                                         inflated_targs[ii] = inflated;
3452                                 }
3453
3454                                 return gt.GetDefinition ().MakeGenericType (context, inflated_targs);
3455                         }
3456
3457                         var ac = parameter as ArrayContainer;
3458                         if (ac != null) {
3459                                 var inflated = InflateGenericArgument (context, ac.Element);
3460                                 if (inflated != ac.Element)
3461                                         return ArrayContainer.MakeType (context.Module, inflated);
3462                         }
3463
3464                         return parameter;
3465                 }
3466
3467                 //
3468                 // Tests whether all delegate input arguments are fixed and generic output type
3469                 // requires output type inference
3470                 //
3471                 public bool IsReturnTypeNonDependent (MethodSpec invoke, TypeSpec returnType)
3472                 {
3473                         AParametersCollection d_parameters = invoke.Parameters;
3474
3475                         if (d_parameters.IsEmpty)
3476                                 return true;
3477
3478                         while (returnType.IsArray)
3479                                 returnType = ((ArrayContainer) returnType).Element;
3480
3481                         if (returnType.IsGenericParameter) {
3482                                 if (IsFixed (returnType))
3483                                     return false;
3484                         } else if (TypeManager.IsGenericType (returnType)) {
3485                                 TypeSpec[] g_args = TypeManager.GetTypeArguments (returnType);
3486
3487                                 // At least one unfixed return type has to exist
3488                                 if (AllTypesAreFixed (g_args))
3489                                         return false;
3490                         } else {
3491                                 return false;
3492                         }
3493
3494                         // All generic input arguments have to be fixed
3495                         return AllTypesAreFixed (d_parameters.Types);
3496                 }
3497
3498                 bool IsFixed (TypeSpec type)
3499                 {
3500                         return IsUnfixed (type) == -1;
3501                 }
3502
3503                 int IsUnfixed (TypeSpec type)
3504                 {
3505                         if (!type.IsGenericParameter)
3506                                 return -1;
3507
3508                         for (int i = 0; i < tp_args.Length; ++i) {
3509                                 if (tp_args[i] == type) {
3510                                         if (fixed_types[i] != null)
3511                                                 break;
3512
3513                                         return i;
3514                                 }
3515                         }
3516
3517                         return -1;
3518                 }
3519
3520                 //
3521                 // 26.3.3.9 Lower-bound Inference
3522                 //
3523                 public int LowerBoundInference (TypeSpec u, TypeSpec v)
3524                 {
3525                         return LowerBoundInference (u, v, false);
3526                 }
3527
3528                 //
3529                 // Lower-bound (false) or Upper-bound (true) inference based on inversed argument
3530                 //
3531                 int LowerBoundInference (TypeSpec u, TypeSpec v, bool inversed)
3532                 {
3533                         // If V is one of the unfixed type arguments
3534                         int pos = IsUnfixed (v);
3535                         if (pos != -1) {
3536                                 AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos, false);
3537                                 return 1;
3538                         }
3539
3540                         // If U is an array type
3541                         var u_ac = u as ArrayContainer;
3542                         if (u_ac != null) {
3543                                 var v_ac = v as ArrayContainer;
3544                                 if (v_ac != null) {
3545                                         if (u_ac.Rank != v_ac.Rank)
3546                                                 return 0;
3547
3548                                         if (TypeSpec.IsValueType (u_ac.Element))
3549                                                 return ExactInference (u_ac.Element, v_ac.Element);
3550
3551                                         return LowerBoundInference (u_ac.Element, v_ac.Element, inversed);
3552                                 }
3553
3554                                 if (u_ac.Rank != 1 || !v.IsArrayGenericInterface)
3555                                         return 0;
3556
3557                                 var v_i = TypeManager.GetTypeArguments (v) [0];
3558                                 if (TypeSpec.IsValueType (u_ac.Element))
3559                                         return ExactInference (u_ac.Element, v_i);
3560
3561                                 return LowerBoundInference (u_ac.Element, v_i);
3562                         }
3563
3564                         if (v.IsGenericOrParentIsGeneric) {
3565                                 //
3566                                 // if V is a constructed type C<V1..Vk> and there is a unique type C<U1..Uk>
3567                                 // such that U is identical to, inherits from (directly or indirectly),
3568                                 // or implements (directly or indirectly) C<U1..Uk>
3569                                 //
3570                                 var u_candidates = new List<TypeSpec> ();
3571                                 var open_v = v.MemberDefinition;
3572
3573                                 for (TypeSpec t = u; t != null; t = t.BaseType) {
3574                                         if (open_v == t.MemberDefinition)
3575                                                 u_candidates.Add (t);
3576
3577                                         //
3578                                         // Using this trick for dynamic type inference, the spec says the type arguments are "unknown" but
3579                                         // that would complicate the process a lot, instead I treat them as dynamic
3580                                         //
3581                                         if (t.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
3582                                                 u_candidates.Add (t);
3583                                 }
3584
3585                                 if (u.Interfaces != null) {
3586                                         foreach (var iface in u.Interfaces) {
3587                                                 if (open_v == iface.MemberDefinition)
3588                                                         u_candidates.Add (iface);
3589                                         }
3590                                 }
3591
3592                                 TypeSpec[] unique_candidate_targs = null;
3593                                 var ga_v = TypeSpec.GetAllTypeArguments (v);
3594                                 foreach (TypeSpec u_candidate in u_candidates) {
3595                                         //
3596                                         // The unique set of types U1..Uk means that if we have an interface I<T>,
3597                                         // class U : I<int>, I<long> then no type inference is made when inferring
3598                                         // type I<T> by applying type U because T could be int or long
3599                                         //
3600                                         if (unique_candidate_targs != null) {
3601                                                 TypeSpec[] second_unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3602                                                 if (TypeSpecComparer.Equals (unique_candidate_targs, second_unique_candidate_targs)) {
3603                                                         unique_candidate_targs = second_unique_candidate_targs;
3604                                                         continue;
3605                                                 }
3606
3607                                                 //
3608                                                 // Break when candidate arguments are ambiguous
3609                                                 //
3610                                                 return 0;
3611                                         }
3612
3613                                         //
3614                                         // A candidate is dynamic type expression, to simplify things use dynamic
3615                                         // for all type parameter of this type. For methods like this one
3616                                         //
3617                                         // void M<T, U> (IList<T>, IList<U[]>)
3618                                         //
3619                                         // dynamic becomes both T and U when the arguments are of dynamic type
3620                                         //
3621                                         if (u_candidate.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
3622                                                 unique_candidate_targs = new TypeSpec[ga_v.Length];
3623                                                 for (int i = 0; i < unique_candidate_targs.Length; ++i)
3624                                                         unique_candidate_targs[i] = u_candidate;
3625                                         } else {
3626                                                 unique_candidate_targs = TypeSpec.GetAllTypeArguments (u_candidate);
3627                                         }
3628                                 }
3629
3630                                 if (unique_candidate_targs != null) {
3631                                         int score = 0;
3632                                         int tp_index = -1;
3633                                         TypeParameterSpec[] tps = null;
3634
3635                                         for (int i = 0; i < unique_candidate_targs.Length; ++i) {
3636                                                 if (tp_index < 0) {
3637                                                         while (v.Arity == 0)
3638                                                                 v = v.DeclaringType;
3639
3640                                                         tps = v.MemberDefinition.TypeParameters;
3641                                                         tp_index = tps.Length - 1;
3642                                                 }
3643
3644                                                 Variance variance = tps [tp_index--].Variance;
3645
3646                                                 TypeSpec u_i = unique_candidate_targs [i];
3647                                                 if (variance == Variance.None || TypeSpec.IsValueType (u_i)) {
3648                                                         if (ExactInference (u_i, ga_v [i]) == 0)
3649                                                                 ++score;
3650                                                 } else {
3651                                                         bool upper_bound = (variance == Variance.Contravariant && !inversed) ||
3652                                                                 (variance == Variance.Covariant && inversed);
3653
3654                                                         if (LowerBoundInference (u_i, ga_v [i], upper_bound) == 0)
3655                                                                 ++score;
3656                                                 }
3657                                         }
3658
3659                                         return score;
3660                                 }
3661                         }
3662
3663                         return 0;
3664                 }
3665
3666                 //
3667                 // 26.3.3.6 Output Type Inference
3668                 //
3669                 public int OutputTypeInference (ResolveContext ec, Expression e, TypeSpec t)
3670                 {
3671                         // If e is a lambda or anonymous method with inferred return type
3672                         AnonymousMethodExpression ame = e as AnonymousMethodExpression;
3673                         if (ame != null) {
3674                                 TypeSpec rt = ame.InferReturnType (ec, this, t);
3675                                 var invoke = Delegate.GetInvokeMethod (t);
3676
3677                                 if (rt == null) {
3678                                         AParametersCollection pd = invoke.Parameters;
3679                                         return ame.Parameters.Count == pd.Count ? 1 : 0;
3680                                 }
3681
3682                                 TypeSpec rtype = invoke.ReturnType;
3683                                 return LowerBoundInference (rt, rtype) + 1;
3684                         }
3685
3686                         //
3687                         // if E is a method group and T is a delegate type or expression tree type
3688                         // return type Tb with parameter types T1..Tk and return type Tb, and overload
3689                         // resolution of E with the types T1..Tk yields a single method with return type U,
3690                         // then a lower-bound inference is made from U for Tb.
3691                         //
3692                         if (e is MethodGroupExpr) {
3693                                 if (!t.IsDelegate) {
3694                                         if (!t.IsExpressionTreeType)
3695                                                 return 0;
3696
3697                                         t = TypeManager.GetTypeArguments (t)[0];
3698                                 }
3699
3700                                 var invoke = Delegate.GetInvokeMethod (t);
3701                                 TypeSpec rtype = invoke.ReturnType;
3702
3703                                 if (!IsReturnTypeNonDependent (invoke, rtype))
3704                                         return 0;
3705
3706                                 // LAMESPEC: Standard does not specify that all methodgroup arguments
3707                                 // has to be fixed but it does not specify how to do recursive type inference
3708                                 // either. We choose the simple option and infer return type only
3709                                 // if all delegate generic arguments are fixed.
3710                                 TypeSpec[] param_types = new TypeSpec [invoke.Parameters.Count];
3711                                 for (int i = 0; i < param_types.Length; ++i) {
3712                                         var inflated = InflateGenericArgument (ec, invoke.Parameters.Types[i]);
3713                                         if (inflated == null)
3714                                                 return 0;
3715
3716                                         param_types[i] = inflated;
3717                                 }
3718
3719                                 MethodGroupExpr mg = (MethodGroupExpr) e;
3720                                 Arguments args = DelegateCreation.CreateDelegateMethodArguments (ec, invoke.Parameters, param_types, e.Location);
3721                                 mg = mg.OverloadResolve (ec, ref args, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly);
3722                                 if (mg == null)
3723                                         return 0;
3724
3725                                 return LowerBoundInference (mg.BestCandidateReturnType, rtype) + 1;
3726                         }
3727
3728                         //
3729                         // if e is an expression with type U, then
3730                         // a lower-bound inference is made from U for T
3731                         //
3732                         return LowerBoundInference (e.Type, t) * 2;
3733                 }
3734
3735                 void RemoveDependentTypes (List<TypeSpec> types, TypeSpec returnType)
3736                 {
3737                         int idx = IsUnfixed (returnType);
3738                         if (idx >= 0) {
3739                                 types [idx] = null;
3740                                 return;
3741                         }
3742
3743                         if (TypeManager.IsGenericType (returnType)) {
3744                                 foreach (TypeSpec t in TypeManager.GetTypeArguments (returnType)) {
3745                                         RemoveDependentTypes (types, t);
3746                                 }
3747                         }
3748                 }
3749
3750                 public bool UnfixedVariableExists {
3751                         get {
3752                                 foreach (TypeSpec ut in fixed_types) {
3753                                         if (ut == null)
3754                                                 return true;
3755                                 }
3756
3757                                 return false;
3758                         }
3759                 }
3760         }
3761 }