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