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 //
  13 using System;
  14 using System.Reflection;
  15 using System.Reflection.Emit;
  16 using System.Globalization;
  17 using System.Collections.Generic;
  18 using System.Text;
  19 using System.Linq;
  20
  21 namespace Mono.CSharp {
  22         public enum Variance
  23         {
  24                 //
  25                 // Don't add or modify internal values, they are used as -/+ calculation signs
  26                 //
  27                 None                    = 0,
  28                 Covariant               = 1,
  29                 Contravariant   = -1
  30         }
  31
  32         [Flags]
  33         public enum SpecialConstraint
  34         {
  35                 None            = 0,
  36                 Constructor = 1 << 2,
  37                 Class           = 1 << 3,
  38                 Struct          = 1 << 4
  39         }
  40
  41         public class SpecialContraintExpr : FullNamedExpression
  42         {
  43                 public SpecialContraintExpr (SpecialConstraint constraint, Location loc)
  44                 {
  45                         this.loc = loc;
  46                         this.Constraint = constraint;
  47                 }
  48
  49                 public SpecialConstraint Constraint { get; private set; }
  50
  51                 protected override Expression DoResolve (ResolveContext rc)
  52                 {
  53                         throw new NotImplementedException ();
  54                 }
  55         }
  56
  57         //
  58         // A set of parsed constraints for a type parameter
  59         //
  60         public class Constraints
  61         {
  62                 SimpleMemberName tparam;
  63                 List<FullNamedExpression> constraints;
  64                 Location loc;
  65                 bool resolved;
  66                 bool resolving;
  67
  68                 public Constraints (SimpleMemberName tparam, List<FullNamedExpression> constraints, Location loc)
  69                 {
  70                         this.tparam = tparam;
  71                         this.constraints = constraints;
  72                         this.loc = loc;
  73                 }
  74
  75                 #region Properties
  76
  77                 public Location Location {
  78                         get {
  79                                 return loc;
  80                         }
  81                 }
  82
  83                 public SimpleMemberName TypeParameter {
  84                         get {
  85                                 return tparam;
  86                         }
  87                 }
  88
  89                 #endregion
  90
  91                 bool CheckConflictingInheritedConstraint (TypeSpec ba, TypeSpec bb, IMemberContext context, Location loc)
  92                 {
  93                         if (!TypeSpec.IsBaseClass (ba, bb, false) && !TypeSpec.IsBaseClass (bb, ba, false)) {
  94                                 context.Compiler.Report.Error (455, loc,
  95                                         "Type parameter `{0}' inherits conflicting constraints `{1}' and `{2}'",
  96                                         tparam.Value,
  97                                         ba.GetSignatureForError (), bb.GetSignatureForError ());
  98                                 return false;
  99                         }
 100
 101                         return true;
 102                 }
 103
 104                 public void CheckGenericConstraints (IMemberContext context)
 105                 {
 106                         foreach (var c in constraints) {
 107                                 var ge = c as GenericTypeExpr;
 108                                 if (ge != null)
 109                                         ge.CheckConstraints (context);
 110                         }
 111                 }
 112
 113                 //
 114                 // Resolve the constraints types with only possible early checks, return
 115                 // value `false' is reserved for recursive failure
 116                 //
 117                 public bool Resolve (IMemberContext context, TypeParameter tp)
 118                 {
 119                         if (resolved)
 120                                 return true;
 121
 122                         if (resolving)
 123                                 return false;
 124
 125                         resolving = true;
 126                         var spec = tp.Type;
 127                         List<TypeParameterSpec> tparam_types = null;
 128                         bool iface_found = false;
 129
 130                         spec.BaseType = TypeManager.object_type;
 131
 132                         for (int i = 0; i < constraints.Count; ++i) {
 133                                 var constraint = constraints[i];
 134
 135                                 if (constraint is SpecialContraintExpr) {
 136                                         spec.SpecialConstraint |= ((SpecialContraintExpr) constraint).Constraint;
 137                                         if (spec.HasSpecialStruct)
 138                                                 spec.BaseType = TypeManager.value_type;
 139
 140                                         // Set to null as it does not have a type
 141                                         constraints[i] = null;
 142                                         continue;
 143                                 }
 144
 145                                 var type_expr = constraints[i] = constraint.ResolveAsTypeTerminal (context, false);
 146                                 if (type_expr == null)
 147                                         continue;
 148
 149                                 var gexpr = type_expr as GenericTypeExpr;
 150                                 if (gexpr != null && gexpr.HasDynamicArguments ()) {
 151                                         context.Compiler.Report.Error (1968, constraint.Location,
 152                                                 "A constraint cannot be the dynamic type `{0}'", gexpr.GetSignatureForError ());
 153                                         continue;
 154                                 }
 155
 156                                 var type = type_expr.Type;
 157
 158                                 if (!context.CurrentMemberDefinition.IsAccessibleAs (type)) {
 159                                         context.Compiler.Report.SymbolRelatedToPreviousError (type);
 160                                         context.Compiler.Report.Error (703, loc,
 161                                                 "Inconsistent accessibility: constraint type `{0}' is less accessible than `{1}'",
 162                                                 type.GetSignatureForError (), context.GetSignatureForError ());
 163                                 }
 164
 165                                 if (type.IsInterface) {
 166                                         if (!spec.AddInterface (type)) {
 167                                                 context.Compiler.Report.Error (405, constraint.Location,
 168                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 169                                         }
 170
 171                                         iface_found = true;
 172                                         continue;
 173                                 }
 174
 175
 176                                 var constraint_tp = type as TypeParameterSpec;
 177                                 if (constraint_tp != null) {
 178                                         if (tparam_types == null) {
 179                                                 tparam_types = new List<TypeParameterSpec> (2);
 180                                         } else if (tparam_types.Contains (constraint_tp)) {
 181                                                 context.Compiler.Report.Error (405, constraint.Location,
 182                                                         "Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
 183                                                 continue;
 184                                         }
 185
 186                                         //
 187                                         // Checks whether each generic method parameter constraint type
 188                                         // is valid with respect to T
 189                                         //
 190                                         if (tp.IsMethodTypeParameter) {
 191                                                 TypeManager.CheckTypeVariance (type, Variance.Contravariant, context);
 192                                         }
 193
 194                                         var tp_def = constraint_tp.MemberDefinition as TypeParameter;
 195                                         if (tp_def != null && !tp_def.ResolveConstraints (context)) {
 196                                                 context.Compiler.Report.Error (454, constraint.Location,
 197                                                         "Circular constraint dependency involving `{0}' and `{1}'",
 198                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 199                                                 continue;
 200                                         }
 201
 202                                         //
 203                                         // Checks whether there are no conflicts between type parameter constraints
 204                                         //
 205                                         // class Foo<T, U>
 206                                         //      where T : A
 207                                         //      where U : B, T
 208                                         //
 209                                         // A and B are not convertible and only 1 class constraint is allowed
 210                                         //
 211                                         if (constraint_tp.HasTypeConstraint) {
 212                                                 if (spec.HasTypeConstraint || spec.HasSpecialStruct) {
 213                                                         if (!CheckConflictingInheritedConstraint (spec.BaseType, constraint_tp.BaseType, context, constraint.Location))
 214                                                                 continue;
 215                                                 } else {
 216                                                         for (int ii = 0; ii < tparam_types.Count; ++ii) {
 217                                                                 if (!tparam_types[ii].HasTypeConstraint)
 218                                                                         continue;
 219
 220                                                                 if (!CheckConflictingInheritedConstraint (tparam_types[ii].BaseType, constraint_tp.BaseType, context, constraint.Location))
 221                                                                         break;
 222                                                         }
 223                                                 }
 224                                         }
 225
 226                                         if (constraint_tp.HasSpecialStruct) {
 227                                                 context.Compiler.Report.Error (456, constraint.Location,
 228                                                         "Type parameter `{0}' has the `struct' constraint, so it cannot be used as a constraint for `{1}'",
 229                                                         constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
 230                                                 continue;
 231                                         }
 232
 233                                         tparam_types.Add (constraint_tp);
 234                                         continue;
 235                                 }
 236
 237                                 if (iface_found || spec.HasTypeConstraint) {
 238                                         context.Compiler.Report.Error (406, constraint.Location,
 239                                                 "The class type constraint `{0}' must be listed before any other constraints. Consider moving type constraint to the beginning of the constraint list",
 240                                                 type.GetSignatureForError ());
 241                                 }
 242
 243                                 if (spec.HasSpecialStruct || spec.HasSpecialClass) {
 244                                         context.Compiler.Report.Error (450, type_expr.Location,
 245                                                 "`{0}': cannot specify both a constraint class and the `class' or `struct' constraint",
 246                                                 type.GetSignatureForError ());
 247                                 }
 248
 249                                 if (type == InternalType.Dynamic) {
 250                                         context.Compiler.Report.Error (1967, constraint.Location, "A constraint cannot be the dynamic type");
 251                                         continue;
 252                                 }
 253
 254                                 if (type.IsSealed || !type.IsClass) {
 255                                         context.Compiler.Report.Error (701, loc,
 256                                                 "`{0}' is not a valid constraint. A constraint must be an interface, a non-sealed class or a type parameter",
 257                                                 TypeManager.CSharpName (type));
 258                                         continue;
 259                                 }
 260
 261                                 if (type.IsStatic) {
 262                                         context.Compiler.Report.Error (717, constraint.Location,
 263                                                 "`{0}' is not a valid constraint. Static classes cannot be used as constraints",
 264                                                 type.GetSignatureForError ());
 265                                 } else if (type == TypeManager.array_type || type == TypeManager.delegate_type ||
 266                                                         type == TypeManager.enum_type || type == TypeManager.value_type ||
 267                                                         type == TypeManager.object_type || type == TypeManager.multicast_delegate_type) {
 268                                         context.Compiler.Report.Error (702, constraint.Location,
 269                                                 "A constraint cannot be special class `{0}'", type.GetSignatureForError ());
 270                                         continue;
 271                                 }
 272
 273                                 spec.BaseType = type;
 274                         }
 275
 276                         if (tparam_types != null)
 277                                 spec.TypeArguments = tparam_types.ToArray ();
 278
 279                         resolving = false;
 280                         resolved = true;
 281                         return true;
 282                 }
 283
 284                 public void VerifyClsCompliance (Report report)
 285                 {
 286                         foreach (var c in constraints)
 287                         {
 288                                 if (c == null)
 289                                         continue;
 290
 291                                 if (!c.Type.IsCLSCompliant ()) {
 292                                         report.SymbolRelatedToPreviousError (c.Type);
 293                                         report.Warning (3024, 1, loc, "Constraint type `{0}' is not CLS-compliant",
 294                                                 c.Type.GetSignatureForError ());
 295                                 }
 296                         }
 297                 }
 298         }
 299
 300         //
 301         // A type parameter for a generic type or generic method definition
 302         //
 303         public class TypeParameter : MemberCore, ITypeDefinition
 304         {
 305                 static readonly string[] attribute_target = new string [] { "type parameter" };
 306
 307                 Constraints constraints;
 308                 GenericTypeParameterBuilder builder;
 309                 TypeParameterSpec spec;
 310
 311                 public TypeParameter (DeclSpace parent, int index, MemberName name, Constraints constraints, Attributes attrs, Variance variance)
 312                         : base (parent, name, attrs)
 313                 {
 314                         this.constraints = constraints;
 315                         this.spec = new TypeParameterSpec (null, index, this, SpecialConstraint.None, variance, null);
 316                 }
 317
 318                 public TypeParameter (TypeParameterSpec spec, DeclSpace parent, TypeSpec parentSpec, MemberName name, Attributes attrs)
 319                         : base (parent, name, attrs)
 320                 {
 321                         this.spec = new TypeParameterSpec (parentSpec, spec.DeclaredPosition, spec.MemberDefinition, spec.SpecialConstraint, spec.Variance, null) {
 322                                 BaseType = spec.BaseType,
 323                                 InterfacesDefined = spec.InterfacesDefined,
 324                                 TypeArguments = spec.TypeArguments
 325                         };
 326                 }
 327
 328                 #region Properties
 329
 330                 public override AttributeTargets AttributeTargets {
 331                         get {
 332                                 return AttributeTargets.GenericParameter;
 333                         }
 334                 }
 335
 336                 public override string DocCommentHeader {
 337                         get {
 338                                 throw new InvalidOperationException (
 339                                         "Unexpected attempt to get doc comment from " + this.GetType ());
 340                         }
 341                 }
 342
 343                 public bool IsMethodTypeParameter {
 344                         get {
 345                                 return spec.IsMethodOwned;
 346                         }
 347                 }
 348
 349                 public string Namespace {
 350                         get {
 351                                 return null;
 352                         }
 353                 }
 354
 355                 public TypeParameterSpec Type {
 356                         get {
 357                                 return spec;
 358                         }
 359                 }
 360
 361                 public int TypeParametersCount {
 362                         get {
 363                                 return 0;
 364                         }
 365                 }
 366
 367                 public TypeParameterSpec[] TypeParameters {
 368                         get {
 369                                 return null;
 370                         }
 371                 }
 372
 373                 public override string[] ValidAttributeTargets {
 374                         get {
 375                                 return attribute_target;
 376                         }
 377                 }
 378
 379                 public Variance Variance {
 380                         get {
 381                                 return spec.Variance;
 382                         }
 383                 }
 384
 385                 #endregion
 386
 387                 //
 388                 // This is called for each part of a partial generic type definition.
 389                 //
 390                 // If partial type parameters constraints are not null and we don't
 391                 // already have constraints they become our constraints. If we already
 392                 // have constraints, we must check that they're the same.
 393                 //
 394                 public bool AddPartialConstraints (TypeContainer part, TypeParameter tp)
 395                 {
 396                         if (builder == null)
 397                                 throw new InvalidOperationException ();
 398
 399                         var new_constraints = tp.constraints;
 400                         if (new_constraints == null)
 401                                 return true;
 402
 403                         // TODO: could create spec only
 404                         //tp.Define (null, -1, part.Definition);
 405                         tp.spec.DeclaringType = part.Definition;
 406                         if (!tp.ResolveConstraints (part))
 407                                 return false;
 408
 409                         if (constraints != null)
 410                                 return spec.HasSameConstraintsDefinition (tp.Type);
 411
 412                         // Copy constraint from resolved part to partial container
 413                         spec.SpecialConstraint = tp.spec.SpecialConstraint;
 414                         spec.InterfacesDefined = tp.spec.InterfacesDefined;
 415                         spec.TypeArguments = tp.spec.TypeArguments;
 416                         spec.BaseType = tp.spec.BaseType;
 417
 418                         return true;
 419                 }
 420
 421                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 422                 {
 423                         builder.SetCustomAttribute ((ConstructorInfo) ctor.GetMetaInfo (), cdata);
 424                 }
 425
 426                 public void CheckGenericConstraints ()
 427                 {
 428                         if (constraints != null)
 429                                 constraints.CheckGenericConstraints (this);
 430                 }
 431
 432                 public TypeParameter CreateHoistedCopy (TypeContainer declaringType, TypeSpec declaringSpec)
 433                 {
 434                         return new TypeParameter (spec, declaringType, declaringSpec, MemberName, null);
 435                 }
 436
 437                 public override bool Define ()
 438                 {
 439                         return true;
 440                 }
 441
 442                 //
 443                 // This is the first method which is called during the resolving
 444                 // process; we're called immediately after creating the type parameters
 445                 // with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
 446                 // MethodBuilder).
 447                 //
 448                 public void Define (GenericTypeParameterBuilder type, TypeSpec declaringType)
 449                 {
 450                         if (builder != null)
 451                                 throw new InternalErrorException ();
 452
 453                         this.builder = type;
 454                         spec.DeclaringType = declaringType;
 455                         spec.SetMetaInfo (type);
 456                 }
 457
 458                 public void EmitConstraints (GenericTypeParameterBuilder builder)
 459                 {
 460                         var attr = GenericParameterAttributes.None;
 461                         if (spec.Variance == Variance.Contravariant)
 462                                 attr |= GenericParameterAttributes.Contravariant;
 463                         else if (spec.Variance == Variance.Covariant)
 464                                 attr |= GenericParameterAttributes.Covariant;
 465
 466                         if (spec.HasSpecialClass)
 467                                 attr |= GenericParameterAttributes.ReferenceTypeConstraint;
 468                         else if (spec.HasSpecialStruct)
 469                                 attr |= GenericParameterAttributes.NotNullableValueTypeConstraint | GenericParameterAttributes.DefaultConstructorConstraint;
 470
 471                         if (spec.HasSpecialConstructor)
 472                                 attr |= GenericParameterAttributes.DefaultConstructorConstraint;
 473
 474                         if (spec.BaseType != TypeManager.object_type)
 475                                 builder.SetBaseTypeConstraint (spec.BaseType.GetMetaInfo ());
 476
 477                         if (spec.InterfacesDefined != null)
 478                                 builder.SetInterfaceConstraints (spec.InterfacesDefined.Select (l => l.GetMetaInfo ()).ToArray ());
 479
 480                         if (spec.TypeArguments != null)
 481                                 builder.SetInterfaceConstraints (spec.TypeArguments.Select (l => l.GetMetaInfo ()).ToArray ());
 482
 483                         builder.SetGenericParameterAttributes (attr);
 484                 }
 485
 486                 public override void Emit ()
 487                 {
 488                         EmitConstraints (builder);
 489
 490                         if (OptAttributes != null)
 491                                 OptAttributes.Emit ();
 492
 493                         base.Emit ();
 494                 }
 495
 496                 public void ErrorInvalidVariance (IMemberContext mc, Variance expected)
 497                 {
 498                         Report.SymbolRelatedToPreviousError (mc.CurrentMemberDefinition);
 499                         string input_variance = Variance == Variance.Contravariant ? "contravariant" : "covariant";
 500                         string gtype_variance;
 501                         switch (expected) {
 502                         case Variance.Contravariant: gtype_variance = "contravariantly"; break;
 503                         case Variance.Covariant: gtype_variance = "covariantly"; break;
 504                         default: gtype_variance = "invariantly"; break;
 505                         }
 506
 507                         Delegate d = mc as Delegate;
 508                         string parameters = d != null ? d.Parameters.GetSignatureForError () : "";
 509
 510                         Report.Error (1961, Location,
 511                                 "The {2} type parameter `{0}' must be {3} valid on `{1}{4}'",
 512                                         GetSignatureForError (), mc.GetSignatureForError (), input_variance, gtype_variance, parameters);
 513                 }
 514
 515                 public TypeSpec GetAttributeCoClass ()
 516                 {
 517                         return null;
 518                 }
 519
 520                 public string GetAttributeDefaultMember ()
 521                 {
 522                         throw new NotSupportedException ();
 523                 }
 524
 525                 public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
 526                 {
 527                         throw new NotSupportedException ();
 528                 }
 529
 530                 public override string GetSignatureForError ()
 531                 {
 532                         return MemberName.Name;
 533                 }
 534
 535                 public MemberCache LoadMembers (TypeSpec declaringType)
 536                 {
 537                         throw new NotSupportedException ("Not supported for compiled definition");
 538                 }
 539
 540                 //
 541                 // Resolves all type parameter constraints
 542                 //
 543                 public bool ResolveConstraints (IMemberContext context)
 544                 {
 545                         if (constraints != null)
 546                                 return constraints.Resolve (context, this);
 547
 548                         if (spec.BaseType == null)
 549                                 spec.BaseType = TypeManager.object_type;
 550
 551                         return true;
 552                 }
 553
 554                 public static TypeParameter FindTypeParameter (TypeParameter[] tparams, string name)
 555                 {
 556                         foreach (var tp in tparams) {
 557                                 if (tp.Name == name)
 558                                         return tp;
 559                         }
 560
 561                         return null;
 562                 }
 563
 564                 public override bool IsClsComplianceRequired ()
 565                 {
 566                         return false;
 567                 }
 568
 569                 public new void VerifyClsCompliance ()
 570                 {
 571                         if (constraints != null)
 572                                 constraints.VerifyClsCompliance (Report);
 573                 }
 574         }
 575
 576         [System.Diagnostics.DebuggerDisplay ("{DisplayDebugInfo()}")]
 577         public class TypeParameterSpec : TypeSpec
 578         {
 579                 public static readonly new TypeParameterSpec[] EmptyTypes = new TypeParameterSpec[0];
 580
 581                 Variance variance;
 582                 SpecialConstraint spec;
 583                 readonly int tp_pos;
 584                 TypeSpec[] targs;
 585                 TypeSpec[] ifaces_defined;
 586
 587                 //
 588                 // Creates type owned type parameter
 589                 //
 590                 public TypeParameterSpec (TypeSpec declaringType, int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, Type info)
 591                         : base (MemberKind.TypeParameter, declaringType, definition, info, Modifiers.PUBLIC)
 592                 {
 593                         this.variance = variance;
 594                         this.spec = spec;
 595                         state &= ~StateFlags.Obsolete_Undetected;
 596                         tp_pos = index;
 597                 }
 598
 599                 //
 600                 // Creates method owned type parameter
 601                 //
 602                 public TypeParameterSpec (int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, Type info)
 603                         : this (null, index, definition, spec, variance, info)
 604                 {
 605                 }
 606
 607                 #region Properties
 608
 609                 public int DeclaredPosition {
 610                         get {
 611                                 return tp_pos;
 612                         }
 613                 }
 614
 615                 public bool HasSpecialConstructor {
 616                         get {
 617                                 return (spec & SpecialConstraint.Constructor) != 0;
 618                         }
 619                 }
 620
 621                 public bool HasSpecialClass {
 622                         get {
 623                                 return (spec & SpecialConstraint.Class) != 0;
 624                         }
 625                 }
 626
 627                 public bool HasSpecialStruct {
 628                         get {
 629                                 return (spec & SpecialConstraint.Struct) != 0;
 630                         }
 631                 }
 632
 633                 public bool HasTypeConstraint {
 634                         get {
 635                                 return BaseType != TypeManager.object_type && BaseType != TypeManager.value_type;
 636                         }
 637                 }
 638
 639                 public override IList<TypeSpec> Interfaces {
 640                         get {
 641                                 if ((state & StateFlags.InterfacesExpanded) == 0) {
 642                                         if (ifaces != null) {
 643                                                 for (int i = 0; i < ifaces.Count; ++i ) {
 644                                                         var iface_type = ifaces[i];
 645                                                         if (iface_type.Interfaces != null) {
 646                                                                 if (ifaces_defined == null)
 647                                                                         ifaces_defined = ifaces.ToArray ();
 648
 649                                                                 for (int ii = 0; ii < iface_type.Interfaces.Count; ++ii) {
 650                                                                         var ii_iface_type = iface_type.Interfaces [ii];
 651
 652                                                                         AddInterface (ii_iface_type);
 653                                                                 }
 654                                                         }
 655                                                 }
 656                                         }
 657
 658                                         if (ifaces_defined == null && ifaces != null)
 659                                                 ifaces_defined = ifaces.ToArray ();
 660
 661                                         state |= StateFlags.InterfacesExpanded;
 662                                 }
 663
 664                                 return ifaces;
 665                         }
 666                 }
 667
 668                 //
 669                 // Unexpanded interfaces list
 670                 //
 671                 public TypeSpec[] InterfacesDefined {
 672                         get {
 673                                 if (ifaces_defined == null && ifaces != null)
 674                                         ifaces_defined = ifaces.ToArray ();
 675
 676                                 return ifaces_defined;
 677                         }
 678                         set {
 679                                 ifaces_defined = value;
 680                         }
 681                 }
 682
 683                 public bool IsConstrained {
 684                         get {
 685                                 return spec != SpecialConstraint.None || ifaces != null || targs != null || HasTypeConstraint;
 686                         }
 687                 }
 688
 689                 //
 690                 // Returns whether the type parameter is "known to be a reference type"
 691                 //
 692                 public bool IsReferenceType {
 693                         get {
 694                                 return (spec & SpecialConstraint.Class) != 0 || HasTypeConstraint;
 695                         }
 696                 }
 697
 698                 public bool IsValueType {       // TODO: Do I need this ?
 699                         get {
 700                                 // TODO MemberCache: probably wrong
 701                                 return HasSpecialStruct;
 702                         }
 703                 }
 704
 705                 public override string Name {
 706                         get {
 707                                 return definition.Name;
 708                         }
 709                 }
 710
 711                 public bool IsMethodOwned {
 712                         get {
 713                                 return DeclaringType == null;
 714                         }
 715                 }
 716
 717                 public SpecialConstraint SpecialConstraint {
 718                         get {
 719                                 return spec;
 720                         }
 721                         set {
 722                                 spec = value;
 723                         }
 724                 }
 725
 726                 //
 727                 // Types used to inflate the generic type
 728                 //
 729                 public new TypeSpec[] TypeArguments {
 730                         get {
 731                                 return targs;
 732                         }
 733                         set {
 734                                 targs = value;
 735                         }
 736                 }
 737
 738                 public Variance Variance {
 739                         get {
 740                                 return variance;
 741                         }
 742                 }
 743
 744                 #endregion
 745
 746                 public string DisplayDebugInfo ()
 747                 {
 748                         var s = GetSignatureForError ();
 749                         return IsMethodOwned ? s + "!!" : s + "!";
 750                 }
 751
 752                 //
 753                 // Finds effective base class
 754                 //
 755                 public TypeSpec GetEffectiveBase ()
 756                 {
 757                         if (HasSpecialStruct) {
 758                                 return TypeManager.value_type;
 759                         }
 760
 761                         if (BaseType != null && targs == null)
 762                                 return BaseType;
 763
 764                         var types = targs;
 765                         if (HasTypeConstraint) {
 766                                 Array.Resize (ref types, types.Length + 1);
 767                                 types[types.Length - 1] = BaseType;
 768                         }
 769
 770                         if (types != null)
 771                                 return Convert.FindMostEncompassedType (types.Select (l => l.BaseType));
 772
 773                         return TypeManager.object_type;
 774                 }
 775
 776                 public override string GetSignatureForError ()
 777                 {
 778                         return Name;
 779                 }
 780
 781                 //
 782                 // Constraints have to match by definition but not position, used by
 783                 // partial classes or methods
 784                 //
 785                 public bool HasSameConstraintsDefinition (TypeParameterSpec other)
 786                 {
 787                         if (spec != other.spec)
 788                                 return false;
 789
 790                         if (BaseType != other.BaseType)
 791                                 return false;
 792
 793                         if (!TypeSpecComparer.Override.IsSame (InterfacesDefined, other.InterfacesDefined))
 794                                 return false;
 795
 796                         if (!TypeSpecComparer.Override.IsSame (targs, other.targs))
 797                                 return false;
 798
 799                         return true;
 800                 }
 801
 802                 //
 803                 // Constraints have to match by using same set of types, used by
 804                 // implicit interface implementation
 805                 //
 806                 public bool HasSameConstraintsImplementation (TypeParameterSpec other)
 807                 {
 808                         if (spec != other.spec)
 809                                 return false;
 810
 811                         //
 812                         // It can be same base type or inflated type parameter
 813                         //
 814                         // interface I<T> { void Foo<U> where U : T; }
 815                         // class A : I<int> { void Foo<X> where X : int {} }
 816                         //
 817                         bool found;
 818                         if (!TypeSpecComparer.Override.IsEqual (BaseType, other.BaseType)) {
 819                                 if (other.targs == null)
 820                                         return false;
 821
 822                                 found = false;
 823                                 foreach (var otarg in other.targs) {
 824                                         if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
 825                                                 found = true;
 826                                                 break;
 827                                         }
 828                                 }
 829
 830                                 if (!found)
 831                                         return false;
 832                         }
 833
 834                         // Check interfaces implementation -> definition
 835                         if (InterfacesDefined != null) {
 836                                 foreach (var iface in InterfacesDefined) {
 837                                         found = false;
 838                                         if (other.InterfacesDefined != null) {
 839                                                 foreach (var oiface in other.InterfacesDefined) {
 840                                                         if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
 841                                                                 found = true;
 842                                                                 break;
 843                                                         }
 844                                                 }
 845                                         }
 846
 847                                         if (found)
 848                                                 continue;
 849
 850                                         if (other.targs != null) {
 851                                                 foreach (var otarg in other.targs) {
 852                                                         if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
 853                                                                 found = true;
 854                                                                 break;
 855                                                         }
 856                                                 }
 857                                         }
 858
 859                                         if (!found)
 860                                                 return false;
 861                                 }
 862                         }
 863
 864                         // Check interfaces implementation <- definition
 865                         if (other.InterfacesDefined != null) {
 866                                 if (InterfacesDefined == null)
 867                                         return false;
 868
 869                                 foreach (var oiface in other.InterfacesDefined) {
 870                                         found = false;
 871                                         foreach (var iface in InterfacesDefined) {
 872                                                 if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
 873                                                         found = true;
 874                                                         break;
 875                                                 }
 876                                         }
 877
 878                                         if (!found)
 879                                                 return false;
 880                                 }
 881                         }
 882
 883                         // Check type parameters implementation -> definition
 884                         if (targs != null) {
 885                                 if (other.targs == null)
 886                                         return false;
 887
 888                                 foreach (var targ in targs) {
 889                                         found = false;
 890                                         foreach (var otarg in other.targs) {
 891                                                 if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
 892                                                         found = true;
 893                                                         break;
 894                                                 }
 895                                         }
 896
 897                                         if (!found)
 898                                                 return false;
 899                                 }
 900                         }
 901
 902                         // Check type parameters implementation <- definition
 903                         if (other.targs != null) {
 904                                 foreach (var otarg in other.targs) {
 905                                         // Ignore inflated type arguments, were checked above
 906                                         if (!otarg.IsGenericParameter)
 907                                                 continue;
 908
 909                                         if (targs == null)
 910                                                 return false;
 911
 912                                         found = false;
 913                                         foreach (var targ in targs) {
 914                                                 if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
 915                                                         found = true;
 916                                                         break;
 917                                                 }
 918                                         }
 919
 920                                         if (!found)
 921                                                 return false;
 922                                 }
 923                         }
 924
 925                         return true;
 926                 }
 927
 928                 public static TypeParameterSpec[] InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec[] tparams)
 929                 {
 930                         TypeParameterSpec[] constraints = null;
 931
 932                         for (int i = 0; i < tparams.Length; ++i) {
 933                                 var tp = tparams[i];
 934                                 if (tp.HasTypeConstraint || tp.Interfaces != null || tp.TypeArguments != null) {
 935                                         if (constraints == null) {
 936                                                 constraints = new TypeParameterSpec[tparams.Length];
 937                                                 Array.Copy (tparams, constraints, constraints.Length);
 938                                         }
 939
 940                                         constraints[i] = (TypeParameterSpec) constraints[i].InflateMember (inflator);
 941                                 }
 942                         }
 943
 944                         if (constraints == null)
 945                                 constraints = tparams;
 946
 947                         return constraints;
 948                 }
 949
 950                 public void InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec tps)
 951                 {
 952                         tps.BaseType = inflator.Inflate (BaseType);
 953                         if (ifaces != null) {
 954                                 tps.ifaces = new List<TypeSpec> (ifaces.Count);
 955                                 for (int i = 0; i < ifaces.Count; ++i)
 956                                         tps.ifaces.Add (inflator.Inflate (ifaces[i]));
 957                         }
 958                         if (targs != null) {
 959                                 tps.targs = new TypeSpec[targs.Length];
 960                                 for (int i = 0; i < targs.Length; ++i)
 961                                         tps.targs[i] = inflator.Inflate (targs[i]);
 962                         }
 963                 }
 964
 965                 public override MemberSpec InflateMember (TypeParameterInflator inflator)
 966                 {
 967                         var tps = (TypeParameterSpec) MemberwiseClone ();
 968                         InflateConstraints (inflator, tps);
 969                         return tps;
 970                 }
 971
 972                 //
 973                 // Populates type parameter members using type parameter constraints
 974                 // The trick here is to be called late enough but not too late to
 975                 // populate member cache with all members from other types
 976                 //
 977                 protected override void InitializeMemberCache (bool onlyTypes)
 978                 {
 979                         cache = new MemberCache ();
 980                         if (ifaces != null) {
 981                                 foreach (var iface_type in Interfaces) {
 982                                         cache.AddInterface (iface_type);
 983                                 }
 984                         }
 985                 }
 986
 987                 public bool IsConvertibleToInterface (TypeSpec iface)
 988                 {
 989                         if (Interfaces != null) {
 990                                 foreach (var t in Interfaces) {
 991                                         if (t == iface)
 992                                                 return true;
 993                                 }
 994                         }
 995
 996                         if (TypeArguments != null) {
 997                                 foreach (var t in TypeArguments) {
 998                                         if (((TypeParameterSpec) t).IsConvertibleToInterface (iface))
 999                                                 return true;
1000                                 }
1001                         }
1002
1003                         return false;
1004                 }
1005
1006                 public override TypeSpec Mutate (TypeParameterMutator mutator)
1007                 {
1008                         return mutator.Mutate (this);
1009                 }
1010         }
1011
1012         public struct TypeParameterInflator
1013         {
1014                 readonly TypeSpec type;
1015                 readonly TypeParameterSpec[] tparams;
1016                 readonly TypeSpec[] targs;
1017
1018                 public TypeParameterInflator (TypeParameterInflator nested, TypeSpec type)
1019                         : this (type, nested.tparams, nested.targs)
1020                 {
1021                 }
1022
1023                 public TypeParameterInflator (TypeSpec type, TypeParameterSpec[] tparams, TypeSpec[] targs)
1024                 {
1025                         if (tparams.Length != targs.Length)
1026                                 throw new ArgumentException ("Invalid arguments");
1027
1028                         this.tparams = tparams;
1029                         this.targs = targs;
1030                         this.type = type;
1031                 }
1032
1033                 //
1034                 // Type parameters to inflate
1035                 //
1036                 public TypeParameterSpec[] TypeParameters {
1037                         get {
1038                                 return tparams;
1039                         }
1040                 }
1041
1042                 public TypeSpec Inflate (TypeSpec ts)
1043                 {
1044                         var tp = ts as TypeParameterSpec;
1045                         if (tp != null)
1046                                 return Inflate (tp);
1047
1048                         var ac = ts as ArrayContainer;
1049                         if (ac != null) {
1050                                 var et = Inflate (ac.Element);
1051                                 if (et != ac.Element)
1052                                         return ArrayContainer.MakeType (et, ac.Rank);
1053
1054                                 return ac;
1055                         }
1056
1057                         //
1058                         // When inflating a nested type, inflate its parent first
1059                         // in case it's using same type parameters (was inflated within the type)
1060                         //
1061                         if (ts.IsNested) {
1062                                 var parent = Inflate (ts.DeclaringType);
1063                                 if (ts.DeclaringType != parent) {
1064                                         //
1065                                         // Keep the inflated type arguments
1066                                         //
1067                                         var targs = ts.TypeArguments;
1068
1069                                         //
1070                                         // Parent was inflated, find the same type on inflated type
1071                                         // to use same cache for nested types on same generic parent
1072                                         //
1073                                         // TODO: Should use BindingRestriction.DeclaredOnly or GetMember
1074                                         ts = MemberCache.FindNestedType (parent, ts.Name, targs.Length);
1075
1076                                         //
1077                                         // Handle the tricky case where parent shares local type arguments
1078                                         // which means inflating inflated type
1079                                         //
1080                                         // class Test<T> {
1081                                         //              public static Nested<T> Foo () { return null; }
1082                                         //
1083                                         //              public class Nested<U> {}
1084                                         //      }
1085                                         //
1086                                         //  return type of Test<string>.Foo() has to be Test<string>.Nested<string>
1087                                         //
1088                                         if (targs.Length > 0) {
1089                                                 var inflated_targs = new TypeSpec [targs.Length];
1090                                                 for (var i = 0; i < targs.Length; ++i)
1091                                                         inflated_targs[i] = Inflate (targs[i]);
1092
1093                                                 ts = ts.MakeGenericType (inflated_targs);
1094                                         }
1095
1096                                         return ts;
1097                                 }
1098                         }
1099
1100                         // Inflate generic type
1101                         if (ts.Arity > 0)
1102                                 return InflateTypeParameters (ts);
1103
1104                         return ts;
1105                 }
1106
1107                 public TypeSpec Inflate (TypeParameterSpec tp)
1108                 {
1109                         for (int i = 0; i < tparams.Length; ++i)
1110                                 if (tparams [i] == tp)
1111                                         return targs[i];
1112
1113                         // This can happen when inflating nested types
1114                         // without type arguments specified
1115                         return tp;
1116                 }
1117
1118                 //
1119                 // Inflates generic types
1120                 //
1121                 TypeSpec InflateTypeParameters (TypeSpec type)
1122                 {
1123                         var targs = new TypeSpec[type.Arity];
1124                         var i = 0;
1125
1126                         var gti = type as InflatedTypeSpec;
1127
1128                         //
1129                         // Inflating using outside type arguments, var v = new Foo<int> (), class Foo<T> {}
1130                         //
1131                         if (gti != null) {
1132                                 for (; i < targs.Length; ++i)
1133                                         targs[i] = Inflate (gti.TypeArguments[i]);
1134
1135                                 return gti.GetDefinition ().MakeGenericType (targs);
1136                         }
1137
1138                         //
1139                         // Inflating parent using inside type arguments, class Foo<T> { ITest<T> foo; }
1140                         //
1141                         var args = type.MemberDefinition.TypeParameters;
1142                         foreach (var ds_tp in args)
1143                                 targs[i++] = Inflate (ds_tp);
1144
1145                         return type.MakeGenericType (targs);
1146                 }
1147
1148                 public TypeSpec TypeInstance {
1149                         get { return type; }
1150                 }
1151         }
1152
1153         //
1154         // Before emitting any code we have to change all MVAR references to VAR
1155         // when the method is of generic type and has hoisted variables
1156         //
1157         public class TypeParameterMutator
1158         {
1159                 TypeParameter[] mvar;
1160                 TypeParameter[] var;
1161                 Dictionary<TypeSpec, TypeSpec> mutated_typespec = new Dictionary<TypeSpec, TypeSpec> ();
1162
1163                 public TypeParameterMutator (TypeParameter[] mvar, TypeParameter[] var)
1164                 {
1165                         if (mvar.Length != var.Length)
1166                                 throw new ArgumentException ();
1167
1168                         this.mvar = mvar;
1169                         this.var = var;
1170                 }
1171
1172                 public static TypeSpec GetMemberDeclaringType (TypeSpec type)
1173                 {
1174                         if (type is InflatedTypeSpec) {
1175                                 if (type.DeclaringType == null)
1176                                         return type.GetDefinition ();
1177
1178                                 var parent = GetMemberDeclaringType (type.DeclaringType);
1179                                 type = MemberCache.GetMember<TypeSpec> (parent, type);
1180                         }
1181
1182                         return type;
1183                 }
1184
1185                 public TypeSpec Mutate (TypeSpec ts)
1186                 {
1187                         TypeSpec value;
1188                         if (mutated_typespec.TryGetValue (ts, out value))
1189                                 return value;
1190
1191                         value = ts.Mutate (this);
1192                         mutated_typespec.Add (ts, value);
1193                         return value;
1194                 }
1195
1196                 public FieldInfo Mutate (FieldSpec fs)
1197                 {
1198                         // TODO:
1199                         return fs.GetMetaInfo ();
1200                 }
1201
1202                 public TypeParameterSpec Mutate (TypeParameterSpec tp)
1203                 {
1204                         for (int i = 0; i < mvar.Length; ++i) {
1205                                 if (mvar[i].Type == tp)
1206                                         return var[i].Type;
1207                         }
1208
1209                         return tp;
1210                 }
1211
1212                 public TypeSpec[] Mutate (TypeSpec[] targs)
1213                 {
1214                         TypeSpec[] mutated = new TypeSpec[targs.Length];
1215                         bool changed = false;
1216                         for (int i = 0; i < targs.Length; ++i) {
1217                                 mutated[i] = Mutate (targs[i]);
1218                                 changed |= targs[i] != mutated[i];
1219                         }
1220
1221                         return changed ? mutated : targs;
1222                 }
1223         }
1224
1225         /// <summary>
1226         ///   A TypeExpr which already resolved to a type parameter.
1227         /// </summary>
1228         public class TypeParameterExpr : TypeExpr {
1229
1230                 public TypeParameterExpr (TypeParameter type_parameter, Location loc)
1231                 {
1232                         this.type = type_parameter.Type;
1233                         this.eclass = ExprClass.TypeParameter;
1234                         this.loc = loc;
1235                 }
1236
1237                 protected override TypeExpr DoResolveAsTypeStep (IMemberContext ec)
1238                 {
1239                         throw new NotSupportedException ();
1240                 }
1241
1242                 public override FullNamedExpression ResolveAsTypeStep (IMemberContext ec, bool silent)
1243                 {
1244                         return this;
1245                 }
1246
1247                 public override bool CheckAccessLevel (IMemberContext ds)
1248                 {
1249                         return true;
1250                 }
1251         }
1252
1253         public class InflatedTypeSpec : TypeSpec
1254         {
1255                 TypeSpec[] targs;
1256                 TypeParameterSpec[] constraints;
1257                 readonly TypeSpec open_type;
1258
1259                 public InflatedTypeSpec (TypeSpec openType, TypeSpec declaringType, TypeSpec[] targs)
1260                         : base (openType.Kind, declaringType, openType.MemberDefinition, null, openType.Modifiers)
1261                 {
1262                         if (targs == null)
1263                                 throw new ArgumentNullException ("targs");
1264
1265 //                      this.state = openType.state;
1266                         this.open_type = openType;
1267                         this.targs = targs;
1268                 }
1269
1270                 #region Properties
1271
1272                 public override TypeSpec BaseType {
1273                         get {
1274                                 if (cache == null || (state & StateFlags.PendingBaseTypeInflate) != 0)
1275                                         InitializeMemberCache (true);
1276
1277                                 return base.BaseType;
1278                         }
1279                 }
1280
1281                 //
1282                 // Inflated type parameters with constraints array, mapping with type arguments is based on index
1283                 //
1284                 public TypeParameterSpec[] Constraints {
1285                         get {
1286                                 if (constraints == null) {
1287                                         var inflator = new TypeParameterInflator (this, MemberDefinition.TypeParameters, targs);
1288                                         constraints = TypeParameterSpec.InflateConstraints (inflator, MemberDefinition.TypeParameters);
1289                                 }
1290
1291                                 return constraints;
1292                         }
1293                 }
1294
1295                 public override IList<TypeSpec> Interfaces {
1296                         get {
1297                                 if (cache == null)
1298                                         InitializeMemberCache (true);
1299
1300                                 return base.Interfaces;
1301                         }
1302                 }
1303
1304                 public override MemberCache MemberCacheTypes {
1305                         get {
1306                                 if (cache == null)
1307                                         InitializeMemberCache (true);
1308
1309                                 return cache;
1310                         }
1311                 }
1312
1313                 //
1314                 // Types used to inflate the generic  type
1315                 //
1316                 public override TypeSpec[] TypeArguments {
1317                         get {
1318                                 return targs;
1319                         }
1320                 }
1321
1322                 #endregion
1323
1324                 Type CreateMetaInfo (TypeParameterMutator mutator)
1325                 {
1326                         //
1327                         // Converts nested type arguments into right order
1328                         // Foo<string, bool>.Bar<int> => string, bool, int
1329                         //
1330                         var all = new List<Type> ();
1331                         TypeSpec type = this;
1332                         TypeSpec definition = type;
1333                         do {
1334                                 if (type.GetDefinition().IsGeneric) {
1335                                         all.InsertRange (0,
1336                                                 type.TypeArguments != TypeSpec.EmptyTypes ?
1337                                                 type.TypeArguments.Select (l => l.GetMetaInfo ()) :
1338                                                 type.MemberDefinition.TypeParameters.Select (l => l.GetMetaInfo ()));
1339                                 }
1340
1341                                 definition = definition.GetDefinition ();
1342                                 type = type.DeclaringType;
1343                         } while (type != null);
1344
1345                         return definition.GetMetaInfo ().MakeGenericType (all.ToArray ());
1346                 }
1347
1348                 public override ObsoleteAttribute GetAttributeObsolete ()
1349                 {
1350                         return open_type.GetAttributeObsolete ();
1351                 }
1352
1353                 protected override bool IsNotCLSCompliant ()
1354                 {
1355                         if (base.IsNotCLSCompliant ())
1356                                 return true;
1357
1358                         foreach (var ta in TypeArguments) {
1359                                 if (ta.MemberDefinition.IsNotCLSCompliant ())
1360                                         return true;
1361                         }
1362
1363                         return false;
1364                 }
1365
1366                 public override TypeSpec GetDefinition ()
1367                 {
1368                         return open_type;
1369                 }
1370
1371                 public override Type GetMetaInfo ()
1372                 {
1373                         if (info == null)
1374                                 info = CreateMetaInfo (null);
1375
1376                         return info;
1377                 }
1378
1379                 public override string GetSignatureForError ()
1380                 {
1381                         if (TypeManager.IsNullableType (open_type))
1382                                 return targs[0].GetSignatureForError () + "?";
1383
1384                         return base.GetSignatureForError ();
1385                 }
1386
1387                 protected override string GetTypeNameSignature ()
1388                 {
1389                         if (targs.Length == 0 || MemberDefinition is AnonymousTypeClass)
1390                                 return null;
1391
1392                         return "<" + TypeManager.CSharpName (targs) + ">";
1393                 }
1394
1395                 protected override void InitializeMemberCache (bool onlyTypes)
1396                 {
1397                         if (cache == null)
1398                                 cache = new MemberCache (onlyTypes ? open_type.MemberCacheTypes : open_type.MemberCache);
1399
1400                         TypeParameterSpec[] tparams_full;
1401                         TypeSpec[] targs_full = targs;
1402                         if (IsNested) {
1403                                 //
1404                                 // Special case is needed when we are inflating an open type (nested type definition)
1405                                 // on inflated parent. Consider following case
1406                                 //
1407                                 // Foo<T>.Bar<U> => Foo<string>.Bar<U>
1408                                 //
1409                                 // Any later inflation of Foo<string>.Bar<U> has to also inflate T if used inside Bar<U>
1410                                 //
1411                                 List<TypeSpec> merged_targs = null;
1412                                 List<TypeParameterSpec> merged_tparams = null;
1413
1414                                 var type = DeclaringType;
1415
1416                                 do {
1417                                         if (type.TypeArguments.Length > 0) {
1418                                                 if (merged_targs == null) {
1419                                                         merged_targs = new List<TypeSpec> ();
1420                                                         merged_tparams = new List<TypeParameterSpec> ();
1421                                                         if (targs.Length > 0) {
1422                                                                 merged_targs.AddRange (targs);
1423                                                                 merged_tparams.AddRange (open_type.MemberDefinition.TypeParameters);
1424                                                         }
1425                                                 }
1426                                                 merged_tparams.AddRange (type.MemberDefinition.TypeParameters);
1427                                                 merged_targs.AddRange (type.TypeArguments);
1428                                         }
1429                                         type = type.DeclaringType;
1430                                 } while (type != null);
1431
1432                                 if (merged_targs != null) {
1433                                         // Type arguments are not in the right order but it should not matter in this case
1434                                         targs_full = merged_targs.ToArray ();
1435                                         tparams_full = merged_tparams.ToArray ();
1436                                 } else if (targs.Length == 0) {
1437                                         tparams_full = TypeParameterSpec.EmptyTypes;
1438                                 } else {
1439                                         tparams_full = open_type.MemberDefinition.TypeParameters;
1440                                 }
1441                         } else if (targs.Length == 0) {
1442                                 tparams_full = TypeParameterSpec.EmptyTypes;
1443                         } else {
1444                                 tparams_full = open_type.MemberDefinition.TypeParameters;
1445                         }
1446
1447                         var inflator = new TypeParameterInflator (this, tparams_full, targs_full);
1448
1449                         //
1450                         // Two stage inflate due to possible nested types recursive
1451                         // references
1452                         //
1453                         // class A<T> {
1454                         //    B b;
1455                         //    class B {
1456                         //      T Value;
1457                         //    }
1458                         // }
1459                         //
1460                         // When resolving type of `b' members of `B' cannot be
1461                         // inflated because are not yet available in membercache
1462                         //
1463                         if ((state & StateFlags.PendingMemberCacheMembers) == 0) {
1464                                 open_type.MemberCacheTypes.InflateTypes (cache, inflator);
1465
1466                                 //
1467                                 // Inflate any implemented interfaces
1468                                 //
1469                                 if (open_type.Interfaces != null) {
1470                                         ifaces = new List<TypeSpec> (open_type.Interfaces.Count);
1471                                         foreach (var iface in open_type.Interfaces) {
1472                                                 var iface_inflated = inflator.Inflate (iface);
1473                                                 AddInterface (iface_inflated);
1474                                         }
1475                                 }
1476
1477                                 //
1478                                 // Handles the tricky case of recursive nested base generic type
1479                                 //
1480                                 // class A<T> : Base<A<T>.Nested> {
1481                                 //    class Nested {}
1482                                 // }
1483                                 //
1484                                 // When inflating A<T>. base type is not yet known, secondary
1485                                 // inflation is required (not common case) once base scope
1486                                 // is known
1487                                 //
1488                                 if (open_type.BaseType == null) {
1489                                         if (IsClass)
1490                                                 state |= StateFlags.PendingBaseTypeInflate;
1491                                 } else {
1492                                         BaseType = inflator.Inflate (open_type.BaseType);
1493                                 }
1494                         } else if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
1495                                 BaseType = inflator.Inflate (open_type.BaseType);
1496                                 state &= ~StateFlags.PendingBaseTypeInflate;
1497                         }
1498
1499                         if (onlyTypes) {
1500                                 state |= StateFlags.PendingMemberCacheMembers;
1501                                 return;
1502                         }
1503
1504                         var tc = open_type.MemberDefinition as TypeContainer;
1505                         if (tc != null && !tc.HasMembersDefined)
1506                                 throw new InternalErrorException ("Inflating MemberCache with undefined members");
1507
1508                         if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
1509                                 BaseType = inflator.Inflate (open_type.BaseType);
1510                                 state &= ~StateFlags.PendingBaseTypeInflate;
1511                         }
1512
1513                         state &= ~StateFlags.PendingMemberCacheMembers;
1514                         open_type.MemberCache.InflateMembers (cache, open_type, inflator);
1515                 }
1516
1517                 public override TypeSpec Mutate (TypeParameterMutator mutator)
1518                 {
1519                         var targs = TypeArguments;
1520                         if (targs != null)
1521                                 targs = mutator.Mutate (targs);
1522
1523                         var decl = DeclaringType;
1524                         if (IsNested && DeclaringType.IsGenericOrParentIsGeneric)
1525                                 decl = mutator.Mutate (decl);
1526
1527                         if (targs == TypeArguments && decl == DeclaringType)
1528                                 return this;
1529
1530                         var mutated = (InflatedTypeSpec) MemberwiseClone ();
1531                         if (decl != DeclaringType) {
1532                                 // Gets back MethodInfo in case of metaInfo was inflated
1533                                 //mutated.info = MemberCache.GetMember<TypeSpec> (DeclaringType.GetDefinition (), this).info;
1534
1535                                 mutated.declaringType = decl;
1536                                 mutated.state |= StateFlags.PendingMetaInflate;
1537                         }
1538
1539                         if (targs != null) {
1540                                 mutated.targs = targs;
1541                                 mutated.info = null;
1542                         }
1543
1544                         return mutated;
1545                 }
1546         }
1547
1548
1549         //
1550         // Tracks the type arguments when instantiating a generic type. It's used
1551         // by both type arguments and type parameters
1552         //
1553         public class TypeArguments
1554         {
1555                 List<FullNamedExpression> args;
1556                 TypeSpec[] atypes;
1557
1558                 public TypeArguments (params FullNamedExpression[] types)
1559                 {
1560                         this.args = new List<FullNamedExpression> (types);
1561                 }
1562
1563                 public void Add (FullNamedExpression type)
1564                 {
1565                         args.Add (type);
1566                 }
1567
1568                 // TODO: Kill this monster
1569                 public TypeParameterName[] GetDeclarations ()
1570                 {
1571                         return args.ConvertAll (i => (TypeParameterName) i).ToArray ();
1572                 }
1573
1574                 /// <summary>
1575                 ///   We may only be used after Resolve() is called and return the fully
1576                 ///   resolved types.
1577                 /// </summary>
1578                 // TODO: Not needed, just return type from resolve
1579                 public TypeSpec[] Arguments {
1580                         get {
1581                                 return atypes;
1582                         }
1583                 }
1584
1585                 public int Count {
1586                         get {
1587                                 return args.Count;
1588                         }
1589                 }
1590
1591                 public virtual bool IsEmpty {
1592                         get {
1593                                 return false;
1594                         }
1595                 }
1596
1597                 public string GetSignatureForError()
1598                 {
1599                         StringBuilder sb = new StringBuilder ();
1600                         for (int i = 0; i < Count; ++i) {
1601                                 var expr = args[i];
1602                                 if (expr != null)
1603                                         sb.Append (expr.GetSignatureForError ());
1604
1605                                 if (i + 1 < Count)
1606                                         sb.Append (',');
1607                         }
1608
1609                         return sb.ToString ();
1610                 }
1611
1612                 /// <summary>
1613                 ///   Resolve the type arguments.
1614                 /// </summary>
1615                 public virtual bool Resolve (IMemberContext ec)
1616                 {
1617                         if (atypes != null)
1618                             return atypes.Length != 0;
1619
1620                         int count = args.Count;
1621                         bool ok = true;
1622
1623                         atypes = new TypeSpec [count];
1624
1625                         for (int i = 0; i < count; i++){
1626                                 TypeExpr te = args[i].ResolveAsTypeTerminal (ec, false);
1627                                 if (te == null) {
1628                                         ok = false;
1629                                         continue;
1630                                 }
1631
1632                                 atypes[i] = te.Type;
1633
1634                                 if (te.Type.IsStatic) {
1635                                         ec.Compiler.Report.Error (718, te.Location, "`{0}': static classes cannot be used as generic arguments",
1636                                                 te.GetSignatureForError ());
1637                                         ok = false;
1638                                 }
1639
1640                                 if (te.Type.IsPointer || TypeManager.IsSpecialType (te.Type)) {
1641                                         ec.Compiler.Report.Error (306, te.Location,
1642                                                 "The type `{0}' may not be used as a type argument",
1643                                                 te.GetSignatureForError ());
1644                                         ok = false;
1645                                 }
1646                         }
1647
1648                         if (!ok)
1649                                 atypes = TypeSpec.EmptyTypes;
1650
1651                         return ok;
1652                 }
1653
1654                 public TypeArguments Clone ()
1655                 {
1656                         TypeArguments copy = new TypeArguments ();
1657                         foreach (var ta in args)
1658                                 copy.args.Add (ta);
1659
1660                         return copy;
1661                 }
1662         }
1663
1664         public class UnboundTypeArguments : TypeArguments
1665         {
1666                 public UnboundTypeArguments (int arity)
1667                         : base (new FullNamedExpression[arity])
1668                 {
1669                 }
1670
1671                 public override bool IsEmpty {
1672                         get {
1673                                 return true;
1674                         }
1675                 }
1676
1677                 public override bool Resolve (IMemberContext ec)
1678                 {
1679                         // Nothing to be resolved
1680                         return true;
1681                 }
1682         }
1683
1684         public class TypeParameterName : SimpleName
1685         {
1686                 Attributes attributes;
1687                 Variance variance;
1688
1689                 public TypeParameterName (string name, Attributes attrs, Location loc)
1690                         : this (name, attrs, Variance.None, loc)
1691                 {
1692                 }
1693
1694                 public TypeParameterName (string name, Attributes attrs, Variance variance, Location loc)
1695                         : base (name, loc)
1696                 {
1697                         attributes = attrs;
1698                         this.variance = variance;
1699                 }
1700
1701                 public Attributes OptAttributes {
1702                         get {
1703                                 return attributes;
1704                         }
1705                 }
1706
1707                 public Variance Variance {
1708                         get {
1709                                 return variance;
1710                         }
1711                 }
1712         }
1713
1714         //
1715         // A type expression of generic type with type arguments
1716         //
1717         class GenericTypeExpr : TypeExpr
1718         {
1719                 TypeArguments args;
1720                 TypeSpec open_type;
1721                 bool constraints_checked;
1722
1723                 /// <summary>
1724                 ///   Instantiate the generic type `t' with the type arguments `args'.
1725                 ///   Use this constructor if you already know the fully resolved
1726                 ///   generic type.
1727                 /// </summary>
1728                 public GenericTypeExpr (TypeSpec open_type, TypeArguments args, Location l)
1729                 {
1730                         this.open_type = open_type;
1731                         loc = l;
1732                         this.args = args;
1733                 }
1734
1735                 public TypeArguments TypeArguments {
1736                         get { return args; }
1737                 }
1738
1739                 public override string GetSignatureForError ()
1740                 {
1741                         return TypeManager.CSharpName (type);
1742                 }
1743
1744                 protected override TypeExpr DoResolveAsTypeStep (IMemberContext ec)
1745                 {
1746                         if (!args.Resolve (ec))
1747                                 return null;
1748
1749                         TypeSpec[] atypes = args.Arguments;
1750
1751                         //
1752                         // Now bind the parameters
1753                         //
1754                         type = open_type.MakeGenericType (atypes);
1755
1756                         //
1757                         // Check constraints when context is not method/base type
1758                         //
1759                         if (!ec.HasUnresolvedConstraints)
1760                                 CheckConstraints (ec);
1761
1762                         return this;
1763                 }
1764
1765                 //
1766                 // Checks the constraints of open generic type against type
1767                 // arguments. Has to be called after all members have been defined
1768                 //
1769                 public bool CheckConstraints (IMemberContext ec)
1770                 {
1771                         if (constraints_checked)
1772                                 return true;
1773
1774                         constraints_checked = true;
1775
1776                         var gtype = (InflatedTypeSpec) type;
1777                         var constraints = gtype.Constraints;
1778                         if (constraints == null)
1779                                 return true;
1780
1781                         return ConstraintChecker.CheckAll (ec, open_type, args.Arguments, constraints, loc);
1782                 }
1783
1784                 public override bool CheckAccessLevel (IMemberContext mc)
1785                 {
1786                         DeclSpace c = mc.CurrentMemberDefinition as DeclSpace;
1787                         if (c == null)
1788                                 c = mc.CurrentMemberDefinition.Parent;
1789
1790                         return c.CheckAccessLevel (open_type);
1791                 }
1792
1793                 public bool HasDynamicArguments ()
1794                 {
1795                         return HasDynamicArguments (args.Arguments);
1796                 }
1797
1798                 static bool HasDynamicArguments (TypeSpec[] args)
1799                 {
1800                         for (int i = 0; i < args.Length; ++i) {
1801                                 var item = args[i];
1802
1803                                 if (item == InternalType.Dynamic)
1804                                         return true;
1805
1806                                 if (TypeManager.IsGenericType (item))
1807                                         return HasDynamicArguments (TypeManager.GetTypeArguments (item));
1808
1809                                 if (item.IsArray) {
1810                                         while (item.IsArray) {
1811                                                 item = ((ArrayContainer) item).Element;
1812                                         }
1813
1814                                         if (item == InternalType.Dynamic)
1815                                                 return true;
1816                                 }
1817                         }
1818
1819                         return false;
1820                 }
1821
1822                 public override bool Equals (object obj)
1823                 {
1824                         GenericTypeExpr cobj = obj as GenericTypeExpr;
1825                         if (cobj == null)
1826                                 return false;
1827
1828                         if ((type == null) || (cobj.type == null))
1829                                 return false;
1830
1831                         return type == cobj.type;
1832                 }
1833
1834                 public override int GetHashCode ()
1835                 {
1836                         return base.GetHashCode ();
1837                 }
1838         }
1839
1840         //
1841         // Generic type with unbound type arguments, used for typeof (G<,,>)
1842         //
1843         class GenericOpenTypeExpr : TypeExpr
1844         {
1845                 public GenericOpenTypeExpr (TypeSpec type, /*UnboundTypeArguments args,*/ Location loc)
1846                 {
1847                         this.type = type.GetDefinition ();
1848                         this.loc = loc;
1849                 }
1850
1851                 protected override TypeExpr DoResolveAsTypeStep (IMemberContext ec)
1852                 {
1853                         return this;
1854                 }
1855         }
1856
1857         static class ConstraintChecker
1858         {
1859                 /// <summary>
1860                 ///   Check the constraints; we're called from ResolveAsTypeTerminal()
1861                 ///   after fully resolving the constructed type.
1862                 /// </summary>
1863                 public static bool CheckAll (IMemberContext mc, MemberSpec context, TypeSpec[] targs, TypeParameterSpec[] tparams, Location loc)
1864                 {
1865                         for (int i = 0; i < tparams.Length; i++) {
1866                                 if (!CheckConstraint (mc, context, targs [i], tparams [i], loc))
1867                                         return false;
1868                         }
1869
1870                         return true;
1871                 }
1872
1873                 static bool CheckConstraint (IMemberContext mc, MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, Location loc)
1874                 {
1875                         //
1876                         // First, check the `class' and `struct' constraints.
1877                         //
1878                         if (tparam.HasSpecialClass && !TypeManager.IsReferenceType (atype)) {
1879                                 mc.Compiler.Report.Error (452, loc,
1880                                         "The type `{0}' must be a reference type in order to use it as type parameter `{1}' in the generic type or method `{2}'",
1881                                         TypeManager.CSharpName (atype), tparam.GetSignatureForError (), context.GetSignatureForError ());
1882                                 return false;
1883                         }
1884
1885                         if (tparam.HasSpecialStruct && (!TypeManager.IsValueType (atype) || TypeManager.IsNullableType (atype))) {
1886                                 mc.Compiler.Report.Error (453, loc,
1887                                         "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}'",
1888                                         TypeManager.CSharpName (atype), tparam.GetSignatureForError (), context.GetSignatureForError ());
1889                                 return false;
1890                         }
1891
1892                         //
1893                         // The class constraint comes next.
1894                         //
1895                         if (tparam.HasTypeConstraint) {
1896                                 CheckConversion (mc, context, atype, tparam, tparam.BaseType, loc);
1897                         }
1898
1899                         //
1900                         // Now, check the interfaces and type parameters constraints
1901                         //
1902                         if (tparam.Interfaces != null) {
1903                                 if (TypeManager.IsNullableType (atype)) {
1904                                         mc.Compiler.Report.Error (313, loc,
1905                                                 "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",
1906                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError ());
1907                                 } else {
1908                                         foreach (TypeSpec iface in tparam.Interfaces) {
1909                                                 CheckConversion (mc, context, atype, tparam, iface, loc);
1910                                         }
1911                                 }
1912                         }
1913
1914                         //
1915                         // Finally, check the constructor constraint.
1916                         //
1917                         if (!tparam.HasSpecialConstructor)
1918                                 return true;
1919
1920                         if (!HasDefaultConstructor (atype)) {
1921                                 mc.Compiler.Report.SymbolRelatedToPreviousError (atype);
1922                                 mc.Compiler.Report.Error (310, loc,
1923                                         "The type `{0}' must have a public parameterless constructor in order to use it as parameter `{1}' in the generic type or method `{2}'",
1924                                         TypeManager.CSharpName (atype), tparam.GetSignatureForError (), context.GetSignatureForError ());
1925                                 return false;
1926                         }
1927
1928                         return true;
1929                 }
1930
1931                 static void CheckConversion (IMemberContext mc, MemberSpec context, TypeSpec atype, TypeParameterSpec tparam, TypeSpec ttype, Location loc)
1932                 {
1933                         var expr = new EmptyExpression (atype);
1934                         if (!Convert.ImplicitStandardConversionExists (expr, ttype)) {
1935                                 mc.Compiler.Report.SymbolRelatedToPreviousError (tparam);
1936                                 if (TypeManager.IsValueType (atype)) {
1937                                         mc.Compiler.Report.Error (315, loc, "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}'",
1938                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
1939                                 } else if (atype.IsGenericParameter) {
1940                                         mc.Compiler.Report.Error (314, loc, "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}'",
1941                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
1942                                 } else {
1943                                         mc.Compiler.Report.Error (311, loc, "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}'",
1944                                                 atype.GetSignatureForError (), tparam.GetSignatureForError (), context.GetSignatureForError (), ttype.GetSignatureForError ());
1945                                 }
1946                         }
1947                 }
1948
1949                 static bool HasDefaultConstructor (TypeSpec atype)
1950                 {
1951                         var tp = atype as TypeParameterSpec;
1952                         if (tp != null) {
1953                                 return tp.HasSpecialConstructor || tp.HasSpecialStruct;
1954                         }
1955
1956                         if (atype.IsStruct || atype.IsEnum)
1957                                 return true;
1958
1959                         if (atype.IsAbstract)
1960                                 return false;
1961
1962                         var tdef = atype.GetDefinition ();
1963
1964                         //
1965                         // In some circumstances MemberCache is not yet populated and members
1966                         // cannot be defined yet (recursive type new constraints)
1967                         //
1968                         // class A<T> where T : B<T>, new () {}
1969                         // class B<T> where T : A<T>, new () {}
1970                         //
1971                         var tc = tdef.MemberDefinition as Class;
1972                         if (tc != null) {
1973                                 if (tc.InstanceConstructors == null) {
1974                                         // Default ctor will be generated later
1975                                         return true;
1976                                 }
1977
1978                                 foreach (var c in tc.InstanceConstructors) {
1979                                         if (c.ParameterInfo.IsEmpty) {
1980                                                 if ((c.ModFlags & Modifiers.PUBLIC) != 0)
1981                                                         return true;
1982                                         }
1983                                 }
1984
1985                                 return false;
1986                         }
1987
1988                         var found = MemberCache.FindMember (tdef,
1989                                 MemberFilter.Constructor (ParametersCompiled.EmptyReadOnlyParameters),
1990                                 BindingRestriction.DeclaredOnly | BindingRestriction.InstanceOnly);
1991
1992                         return found != null && (found.Modifiers & Modifiers.PUBLIC) != 0;
1993                 }
1994         }
1995
1996         /// <summary>
1997         ///   A generic method definition.
1998         /// </summary>
1999         public class GenericMethod : DeclSpace
2000         {
2001                 ParametersCompiled parameters;
2002
2003                 public GenericMethod (NamespaceEntry ns, DeclSpace parent, MemberName name,
2004                                       FullNamedExpression return_type, ParametersCompiled parameters)
2005                         : base (ns, parent, name, null)
2006                 {
2007                         this.parameters = parameters;
2008                 }
2009
2010                 public GenericMethod (NamespaceEntry ns, DeclSpace parent, MemberName name, TypeParameter[] tparams,
2011                                           FullNamedExpression return_type, ParametersCompiled parameters)
2012                         : this (ns, parent, name, return_type, parameters)
2013                 {
2014                         this.type_params = tparams;
2015                 }
2016
2017                 public override TypeParameter[] CurrentTypeParameters {
2018                         get {
2019                                 return base.type_params;
2020                         }
2021                 }
2022
2023                 public override TypeBuilder DefineType ()
2024                 {
2025                         throw new Exception ();
2026                 }
2027
2028                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
2029                 {
2030                         throw new NotSupportedException ();
2031                 }
2032
2033                 public override bool Define ()
2034                 {
2035                         throw new NotSupportedException ();
2036                 }
2037
2038                 /// <summary>
2039                 ///   Define and resolve the type parameters.
2040                 ///   We're called from Method.Define().
2041                 /// </summary>
2042                 public bool Define (MethodOrOperator m)
2043                 {
2044                         TypeParameterName[] names = MemberName.TypeArguments.GetDeclarations ();
2045                         string[] snames = new string [names.Length];
2046                         for (int i = 0; i < names.Length; i++) {
2047                                 string type_argument_name = names[i].Name;
2048                                 int idx = parameters.GetParameterIndexByName (type_argument_name);
2049
2050                                 if (idx >= 0) {
2051                                         var b = m.Block;
2052                                         if (b == null)
2053                                                 b = new ToplevelBlock (Compiler, Location);
2054
2055                                         b.Error_AlreadyDeclaredTypeParameter (parameters [i].Location,
2056                                                 type_argument_name, "method parameter");
2057                                 }
2058
2059                                 if (m.Block != null) {
2060                                         var ikv = m.Block.GetKnownVariable (type_argument_name);
2061                                         if (ikv != null)
2062                                                 ikv.Block.Error_AlreadyDeclaredTypeParameter (ikv.Location, type_argument_name, "local variable");
2063                                 }
2064
2065                                 snames[i] = type_argument_name;
2066                         }
2067
2068                         GenericTypeParameterBuilder[] gen_params = m.MethodBuilder.DefineGenericParameters (snames);
2069                         for (int i = 0; i < TypeParameters.Length; i++)
2070                                 TypeParameters [i].Define (gen_params [i], null);
2071
2072                         return true;
2073                 }
2074
2075                 public void EmitAttributes ()
2076                 {
2077                         if (OptAttributes != null)
2078                                 OptAttributes.Emit ();
2079                 }
2080
2081                 public override string GetSignatureForError ()
2082                 {
2083                         return base.GetSignatureForError () + parameters.GetSignatureForError ();
2084                 }
2085
2086                 public override AttributeTargets AttributeTargets {
2087                         get {
2088                                 return AttributeTargets.Method | AttributeTargets.ReturnValue;
2089                         }
2090                 }
2091
2092                 public override string DocCommentHeader {
2093                         get { return "M:"; }
2094                 }
2095
2096                 public new void VerifyClsCompliance ()
2097                 {
2098                         foreach (TypeParameter tp in TypeParameters) {
2099                                 tp.VerifyClsCompliance ();
2100                         }
2101                 }
2102         }
2103
2104         public partial class TypeManager
2105         {
2106                 public static Variance CheckTypeVariance (TypeSpec t, Variance expected, IMemberContext member)
2107                 {
2108                         var tp = t as TypeParameterSpec;
2109                         if (tp != null) {
2110                                 Variance v = tp.Variance;
2111                                 if (expected == Variance.None && v != expected ||
2112                                         expected == Variance.Covariant && v == Variance.Contravariant ||
2113                                         expected == Variance.Contravariant && v == Variance.Covariant) {
2114                                         ((TypeParameter)tp.MemberDefinition).ErrorInvalidVariance (member, expected);
2115                                 }
2116
2117                                 return expected;
2118                         }
2119
2120                         if (t.TypeArguments.Length > 0) {
2121                                 var targs_definition = t.MemberDefinition.TypeParameters;
2122                                 TypeSpec[] targs = GetTypeArguments (t);
2123                                 for (int i = 0; i < targs.Length; ++i) {
2124                                         Variance v = targs_definition[i].Variance;
2125                                         CheckTypeVariance (targs[i], (Variance) ((int)v * (int)expected), member);
2126                                 }
2127
2128                                 return expected;
2129                         }
2130
2131                         if (t.IsArray)
2132                                 return CheckTypeVariance (GetElementType (t), expected, member);
2133
2134                         return Variance.None;
2135                 }
2136
2137                 /// <summary>
2138                 ///   Type inference.  Try to infer the type arguments from `method',
2139                 ///   which is invoked with the arguments `arguments'.  This is used
2140                 ///   when resolving an Invocation or a DelegateInvocation and the user
2141                 ///   did not explicitly specify type arguments.
2142                 /// </summary>
2143                 public static int InferTypeArguments (ResolveContext ec, Arguments arguments, ref MethodSpec method)
2144                 {
2145                         ATypeInference ti = ATypeInference.CreateInstance (arguments);
2146                         TypeSpec[] i_args = ti.InferMethodArguments (ec, method);
2147                         if (i_args == null)
2148                                 return ti.InferenceScore;
2149
2150                         if (i_args.Length == 0)
2151                                 return 0;
2152
2153                         method = method.MakeGenericMethod (i_args);
2154                         return 0;
2155                 }
2156         }
2157
2158         abstract class ATypeInference
2159         {
2160                 protected readonly Arguments arguments;
2161                 protected readonly int arg_count;
2162
2163                 protected ATypeInference (Arguments arguments)
2164                 {
2165                         this.arguments = arguments;
2166                         if (arguments != null)
2167                                 arg_count = arguments.Count;
2168                 }
2169
2170                 public static ATypeInference CreateInstance (Arguments arguments)
2171                 {
2172                         return new TypeInference (arguments);
2173                 }
2174
2175                 public virtual int InferenceScore {
2176                         get {
2177                                 return int.MaxValue;
2178                         }
2179                 }
2180
2181                 public abstract TypeSpec[] InferMethodArguments (ResolveContext ec, MethodSpec method);
2182         }
2183
2184         //
2185         // Implements C# type inference
2186         //
2187         class TypeInference : ATypeInference
2188         {
2189                 //
2190                 // Tracks successful rate of type inference
2191                 //
2192                 int score = int.MaxValue;
2193
2194                 public TypeInference (Arguments arguments)
2195                         : base (arguments)
2196                 {
2197                 }
2198
2199                 public override int InferenceScore {
2200                         get {
2201                                 return score;
2202                         }
2203                 }
2204
2205                 public override TypeSpec[] InferMethodArguments (ResolveContext ec, MethodSpec method)
2206                 {
2207                         var method_generic_args = method.GenericDefinition.TypeParameters;
2208                         TypeInferenceContext context = new TypeInferenceContext (method_generic_args);
2209                         if (!context.UnfixedVariableExists)
2210                                 return TypeSpec.EmptyTypes;
2211
2212                         AParametersCollection pd = method.Parameters;
2213                         if (!InferInPhases (ec, context, pd))
2214                                 return null;
2215
2216                         return context.InferredTypeArguments;
2217                 }
2218
2219                 //
2220                 // Implements method type arguments inference
2221                 //
2222                 bool InferInPhases (ResolveContext ec, TypeInferenceContext tic, AParametersCollection methodParameters)
2223                 {
2224                         int params_arguments_start;
2225                         if (methodParameters.HasParams) {
2226                                 params_arguments_start = methodParameters.Count - 1;
2227                         } else {
2228                                 params_arguments_start = arg_count;
2229                         }
2230
2231                         TypeSpec [] ptypes = methodParameters.Types;
2232
2233                         //
2234                         // The first inference phase
2235                         //
2236                         TypeSpec method_parameter = null;
2237                         for (int i = 0; i < arg_count; i++) {
2238                                 Argument a = arguments [i];
2239                                 if (a == null)
2240                                         continue;
2241
2242                                 if (i < params_arguments_start) {
2243                                         method_parameter = methodParameters.Types [i];
2244                                 } else if (i == params_arguments_start) {
2245                                         if (arg_count == params_arguments_start + 1 && TypeManager.HasElementType (a.Type))
2246                                                 method_parameter = methodParameters.Types [params_arguments_start];
2247                                         else
2248                                                 method_parameter = TypeManager.GetElementType (methodParameters.Types [params_arguments_start]);
2249
2250                                         ptypes = (TypeSpec[]) ptypes.Clone ();
2251                                         ptypes [i] = method_parameter;
2252                                 }
2253
2254                                 //
2255                                 // When a lambda expression, an anonymous method
2256                                 // is used an explicit argument type inference takes a place
2257                                 //
2258                                 AnonymousMethodExpression am = a.Expr as AnonymousMethodExpression;
2259                                 if (am != null) {
2260                                         if (am.ExplicitTypeInference (ec, tic, method_parameter))
2261                                                 --score;
2262                                         continue;
2263                                 }
2264
2265                                 if (a.IsByRef) {
2266                                         score -= tic.ExactInference (a.Type, method_parameter);
2267                                         continue;
2268                                 }
2269
2270                                 if (a.Expr.Type == InternalType.Null)
2271                                         continue;
2272
2273                                 if (TypeManager.IsValueType (method_parameter)) {
2274                                         score -= tic.LowerBoundInference (a.Type, method_parameter);
2275                                         continue;
2276                                 }
2277
2278                                 //
2279                                 // Otherwise an output type inference is made
2280                                 //
2281                                 score -= tic.OutputTypeInference (ec, a.Expr, method_parameter);
2282                         }
2283
2284                         //
2285                         // Part of the second phase but because it happens only once
2286                         // we don't need to call it in cycle
2287                         //
2288                         bool fixed_any = false;
2289                         if (!tic.FixIndependentTypeArguments (ec, ptypes, ref fixed_any))
2290                                 return false;
2291
2292                         return DoSecondPhase (ec, tic, ptypes, !fixed_any);
2293                 }
2294
2295                 bool DoSecondPhase (ResolveContext ec, TypeInferenceContext tic, TypeSpec[] methodParameters, bool fixDependent)
2296                 {
2297                         bool fixed_any = false;
2298                         if (fixDependent && !tic.FixDependentTypes (ec, ref fixed_any))
2299                                 return false;
2300
2301                         // If no further unfixed type variables exist, type inference succeeds
2302                         if (!tic.UnfixedVariableExists)
2303                                 return true;
2304
2305                         if (!fixed_any && fixDependent)
2306                                 return false;
2307
2308                         // For all arguments where the corresponding argument output types
2309                         // contain unfixed type variables but the input types do not,
2310                         // an output type inference is made
2311                         for (int i = 0; i < arg_count; i++) {
2312
2313                                 // Align params arguments
2314                                 TypeSpec t_i = methodParameters [i >= methodParameters.Length ? methodParameters.Length - 1: i];
2315
2316                                 if (!TypeManager.IsDelegateType (t_i)) {
2317                                         if (t_i.GetDefinition () != TypeManager.expression_type)
2318                                                 continue;
2319
2320                                         t_i = TypeManager.GetTypeArguments (t_i) [0];
2321                                 }
2322
2323                                 var mi = Delegate.GetInvokeMethod (ec.Compiler, t_i);
2324                                 TypeSpec rtype = mi.ReturnType;
2325
2326                                 if (tic.IsReturnTypeNonDependent (ec, mi, rtype))
2327                                         score -= tic.OutputTypeInference (ec, arguments [i].Expr, t_i);
2328                         }
2329
2330
2331                         return DoSecondPhase (ec, tic, methodParameters, true);
2332                 }
2333         }
2334
2335         public class TypeInferenceContext
2336         {
2337                 enum BoundKind
2338                 {
2339                         Exact   = 0,
2340                         Lower   = 1,
2341                         Upper   = 2
2342                 }
2343
2344                 class BoundInfo : IEquatable<BoundInfo>
2345                 {
2346                         public readonly TypeSpec Type;
2347                         public readonly BoundKind Kind;
2348
2349                         public BoundInfo (TypeSpec type, BoundKind kind)
2350                         {
2351                                 this.Type = type;
2352                                 this.Kind = kind;
2353                         }
2354
2355                         public override int GetHashCode ()
2356                         {
2357                                 return Type.GetHashCode ();
2358                         }
2359
2360                         #region IEquatable<BoundInfo> Members
2361
2362                         public bool Equals (BoundInfo other)
2363                         {
2364                                 return Type == other.Type && Kind == other.Kind;
2365                         }
2366
2367                         #endregion
2368                 }
2369
2370                 readonly TypeSpec[] unfixed_types;
2371                 readonly TypeSpec[] fixed_types;
2372                 readonly List<BoundInfo>[] bounds;
2373                 bool failed;
2374
2375                 // TODO MemberCache: Could it be TypeParameterSpec[] ??
2376                 public TypeInferenceContext (TypeSpec[] typeArguments)
2377                 {
2378                         if (typeArguments.Length == 0)
2379                                 throw new ArgumentException ("Empty generic arguments");
2380
2381                         fixed_types = new TypeSpec [typeArguments.Length];
2382                         for (int i = 0; i < typeArguments.Length; ++i) {
2383                                 if (typeArguments [i].IsGenericParameter) {
2384                                         if (bounds == null) {
2385                                                 bounds = new List<BoundInfo> [typeArguments.Length];
2386                                                 unfixed_types = new TypeSpec [typeArguments.Length];
2387                                         }
2388                                         unfixed_types [i] = typeArguments [i];
2389                                 } else {
2390                                         fixed_types [i] = typeArguments [i];
2391                                 }
2392                         }
2393                 }
2394
2395                 //
2396                 // Used together with AddCommonTypeBound fo implement
2397                 // 7.4.2.13 Finding the best common type of a set of expressions
2398                 //
2399                 public TypeInferenceContext ()
2400                 {
2401                         fixed_types = new TypeSpec [1];
2402                         unfixed_types = new TypeSpec [1];
2403                         unfixed_types[0] = InternalType.Arglist; // it can be any internal type
2404                         bounds = new List<BoundInfo> [1];
2405                 }
2406
2407                 public TypeSpec[] InferredTypeArguments {
2408                         get {
2409                                 return fixed_types;
2410                         }
2411                 }
2412
2413                 public void AddCommonTypeBound (TypeSpec type)
2414                 {
2415                         AddToBounds (new BoundInfo (type, BoundKind.Lower), 0);
2416                 }
2417
2418                 void AddToBounds (BoundInfo bound, int index)
2419                 {
2420                         //
2421                         // Some types cannot be used as type arguments
2422                         //
2423                         if (bound.Type == TypeManager.void_type || bound.Type.IsPointer)
2424                                 return;
2425
2426                         var a = bounds [index];
2427                         if (a == null) {
2428                                 a = new List<BoundInfo> (2);
2429                                 a.Add (bound);
2430                                 bounds [index] = a;
2431                                 return;
2432                         }
2433
2434                         if (a.Contains (bound))
2435                                 return;
2436
2437                         a.Add (bound);
2438                 }
2439
2440                 bool AllTypesAreFixed (TypeSpec[] types)
2441                 {
2442                         foreach (TypeSpec t in types) {
2443                                 if (t.IsGenericParameter) {
2444                                         if (!IsFixed (t))
2445                                                 return false;
2446                                         continue;
2447                                 }
2448
2449                                 if (TypeManager.IsGenericType (t))
2450                                         return AllTypesAreFixed (TypeManager.GetTypeArguments (t));
2451                         }
2452
2453                         return true;
2454                 }
2455
2456                 //
2457                 // 26.3.3.8 Exact Inference
2458                 //
2459                 public int ExactInference (TypeSpec u, TypeSpec v)
2460                 {
2461                         // If V is an array type
2462                         if (v.IsArray) {
2463                                 if (!u.IsArray)
2464                                         return 0;
2465
2466                                 // TODO MemberCache: GetMetaInfo ()
2467                                 if (u.GetMetaInfo ().GetArrayRank () != v.GetMetaInfo ().GetArrayRank ())
2468                                         return 0;
2469
2470                                 return ExactInference (TypeManager.GetElementType (u), TypeManager.GetElementType (v));
2471                         }
2472
2473                         // If V is constructed type and U is constructed type
2474                         if (TypeManager.IsGenericType (v)) {
2475                                 if (!TypeManager.IsGenericType (u))
2476                                         return 0;
2477
2478                                 TypeSpec [] ga_u = TypeManager.GetTypeArguments (u);
2479                                 TypeSpec [] ga_v = TypeManager.GetTypeArguments (v);
2480                                 if (ga_u.Length != ga_v.Length)
2481                                         return 0;
2482
2483                                 int score = 0;
2484                                 for (int i = 0; i < ga_u.Length; ++i)
2485                                         score += ExactInference (ga_u [i], ga_v [i]);
2486
2487                                 return score > 0 ? 1 : 0;
2488                         }
2489
2490                         // If V is one of the unfixed type arguments
2491                         int pos = IsUnfixed (v);
2492                         if (pos == -1)
2493                                 return 0;
2494
2495                         AddToBounds (new BoundInfo (u, BoundKind.Exact), pos);
2496                         return 1;
2497                 }
2498
2499                 public bool FixAllTypes (ResolveContext ec)
2500                 {
2501                         for (int i = 0; i < unfixed_types.Length; ++i) {
2502                                 if (!FixType (ec, i))
2503                                         return false;
2504                         }
2505                         return true;
2506                 }
2507
2508                 //
2509                 // All unfixed type variables Xi are fixed for which all of the following hold:
2510                 // a, There is at least one type variable Xj that depends on Xi
2511                 // b, Xi has a non-empty set of bounds
2512                 //
2513                 public bool FixDependentTypes (ResolveContext ec, ref bool fixed_any)
2514                 {
2515                         for (int i = 0; i < unfixed_types.Length; ++i) {
2516                                 if (unfixed_types[i] == null)
2517                                         continue;
2518
2519                                 if (bounds[i] == null)
2520                                         continue;
2521
2522                                 if (!FixType (ec, i))
2523                                         return false;
2524
2525                                 fixed_any = true;
2526                         }
2527
2528                         return true;
2529                 }
2530
2531                 //
2532                 // All unfixed type variables Xi which depend on no Xj are fixed
2533                 //
2534                 public bool FixIndependentTypeArguments (ResolveContext ec, TypeSpec[] methodParameters, ref bool fixed_any)
2535                 {
2536                         var types_to_fix = new List<TypeSpec> (unfixed_types);
2537                         for (int i = 0; i < methodParameters.Length; ++i) {
2538                                 TypeSpec t = methodParameters[i];
2539
2540                                 if (!TypeManager.IsDelegateType (t)) {
2541                                         if (TypeManager.expression_type == null || t.MemberDefinition != TypeManager.expression_type.MemberDefinition)
2542                                                 continue;
2543
2544                                         t =  TypeManager.GetTypeArguments (t) [0];
2545                                 }
2546
2547                                 if (t.IsGenericParameter)
2548                                         continue;
2549
2550                                 var invoke = Delegate.GetInvokeMethod (ec.Compiler, t);
2551                                 TypeSpec rtype = invoke.ReturnType;
2552                                 if (!rtype.IsGenericParameter && !TypeManager.IsGenericType (rtype))
2553                                         continue;
2554
2555                                 // Remove dependent types, they cannot be fixed yet
2556                                 RemoveDependentTypes (types_to_fix, rtype);
2557                         }
2558
2559                         foreach (TypeSpec t in types_to_fix) {
2560                                 if (t == null)
2561                                         continue;
2562
2563                                 int idx = IsUnfixed (t);
2564                                 if (idx >= 0 && !FixType (ec, idx)) {
2565                                         return false;
2566                                 }
2567                         }
2568
2569                         fixed_any = types_to_fix.Count > 0;
2570                         return true;
2571                 }
2572
2573                 //
2574                 // 26.3.3.10 Fixing
2575                 //
2576                 public bool FixType (ResolveContext ec, int i)
2577                 {
2578                         // It's already fixed
2579                         if (unfixed_types[i] == null)
2580                                 throw new InternalErrorException ("Type argument has been already fixed");
2581
2582                         if (failed)
2583                                 return false;
2584
2585                         var candidates = bounds [i];
2586                         if (candidates == null)
2587                                 return false;
2588
2589                         if (candidates.Count == 1) {
2590                                 unfixed_types[i] = null;
2591                                 TypeSpec t = candidates[0].Type;
2592                                 if (t == InternalType.Null)
2593                                         return false;
2594
2595                                 fixed_types [i] = t;
2596                                 return true;
2597                         }
2598
2599                         //
2600                         // Determines a unique type from which there is
2601                         // a standard implicit conversion to all the other
2602                         // candidate types.
2603                         //
2604                         TypeSpec best_candidate = null;
2605                         int cii;
2606                         int candidates_count = candidates.Count;
2607                         for (int ci = 0; ci < candidates_count; ++ci) {
2608                                 BoundInfo bound = candidates [ci];
2609                                 for (cii = 0; cii < candidates_count; ++cii) {
2610                                         if (cii == ci)
2611                                                 continue;
2612
2613                                         BoundInfo cbound = candidates[cii];
2614
2615                                         // Same type parameters with different bounds
2616                                         if (cbound.Type == bound.Type) {
2617                                                 if (bound.Kind != BoundKind.Exact)
2618                                                         bound = cbound;
2619
2620                                                 continue;
2621                                         }
2622
2623                                         if (bound.Kind == BoundKind.Exact || cbound.Kind == BoundKind.Exact) {
2624                                                 if (cbound.Kind == BoundKind.Lower) {
2625                                                         if (!Convert.ImplicitConversionExists (ec, new TypeExpression (cbound.Type, Location.Null), bound.Type)) {
2626                                                                 break;
2627                                                         }
2628
2629                                                         continue;
2630                                                 }
2631                                                 if (cbound.Kind == BoundKind.Upper) {
2632                                                         if (!Convert.ImplicitConversionExists (ec, new TypeExpression (bound.Type, Location.Null), cbound.Type)) {
2633                                                                 break;
2634                                                         }
2635
2636                                                         continue;
2637                                                 }
2638
2639                                                 if (bound.Kind != BoundKind.Exact) {
2640                                                         if (!Convert.ImplicitConversionExists (ec, new TypeExpression (bound.Type, Location.Null), cbound.Type)) {
2641                                                                 break;
2642                                                         }
2643
2644                                                         bound = cbound;
2645                                                         continue;
2646                                                 }
2647
2648                                                 break;
2649                                         }
2650
2651                                         if (bound.Kind == BoundKind.Lower) {
2652                                                 if (cbound.Kind == BoundKind.Lower) {
2653                                                         if (!Convert.ImplicitConversionExists (ec, new TypeExpression (cbound.Type, Location.Null), bound.Type)) {
2654                                                                 break;
2655                                                         }
2656                                                 } else {
2657                                                         if (!Convert.ImplicitConversionExists (ec, new TypeExpression (bound.Type, Location.Null), cbound.Type)) {
2658                                                                 break;
2659                                                         }
2660                                                 }
2661
2662                                                 continue;
2663                                         }
2664
2665                                         if (bound.Kind == BoundKind.Upper) {
2666                                                 if (!Convert.ImplicitConversionExists (ec, new TypeExpression (bound.Type, Location.Null), cbound.Type)) {
2667                                                         break;
2668                                                 }
2669                                         } else {
2670                                                 throw new NotImplementedException ("variance conversion");
2671                                         }
2672                                 }
2673
2674                                 if (cii != candidates_count)
2675                                         continue;
2676
2677                                 //
2678                                 // We already have the best candidate, break if thet are different
2679                                 //
2680                                 // Dynamic is never ambiguous as we prefer dynamic over other best candidate types
2681                                 //
2682                                 if (best_candidate != null) {
2683
2684                                         if (best_candidate == InternalType.Dynamic)
2685                                                 continue;
2686
2687                                         if (bound.Type != InternalType.Dynamic && best_candidate != bound.Type)
2688                                                 return false;
2689                                 }
2690
2691                                 best_candidate = bound.Type;
2692                         }
2693
2694                         if (best_candidate == null)
2695                                 return false;
2696
2697                         unfixed_types[i] = null;
2698                         fixed_types[i] = best_candidate;
2699                         return true;
2700                 }
2701
2702                 //
2703                 // Uses inferred or partially infered types to inflate delegate type argument. Returns
2704                 // null when type parameter was not yet inferres
2705                 //
2706                 public TypeSpec InflateGenericArgument (TypeSpec parameter)
2707                 {
2708                         var tp = parameter as TypeParameterSpec;
2709                         if (tp != null) {
2710                                 //
2711                                 // Type inference work on generic arguments (MVAR) only
2712                                 //
2713                                 if (!tp.IsMethodOwned)
2714                                         return parameter;
2715
2716                                 return fixed_types [tp.DeclaredPosition] ?? parameter;
2717                         }
2718
2719                         var gt = parameter as InflatedTypeSpec;
2720                         if (gt != null) {
2721                                 var inflated_targs = new TypeSpec [gt.TypeArguments.Length];
2722                                 for (int ii = 0; ii < inflated_targs.Length; ++ii) {
2723                                         var inflated = InflateGenericArgument (gt.TypeArguments [ii]);
2724                                         if (inflated == null)
2725                                                 return null;
2726
2727                                         inflated_targs[ii] = inflated;
2728                                 }
2729
2730                                 return gt.GetDefinition ().MakeGenericType (inflated_targs);
2731                         }
2732
2733                         return parameter;
2734                 }
2735
2736                 //
2737                 // Tests whether all delegate input arguments are fixed and generic output type
2738                 // requires output type inference
2739                 //
2740                 public bool IsReturnTypeNonDependent (ResolveContext ec, MethodSpec invoke, TypeSpec returnType)
2741                 {
2742                         if (returnType.IsGenericParameter) {
2743                                 if (IsFixed (returnType))
2744                                     return false;
2745                         } else if (TypeManager.IsGenericType (returnType)) {
2746                                 if (TypeManager.IsDelegateType (returnType)) {
2747                                         invoke = Delegate.GetInvokeMethod (ec.Compiler, returnType);
2748                                         return IsReturnTypeNonDependent (ec, invoke, invoke.ReturnType);
2749                                 }
2750
2751                                 TypeSpec[] g_args = TypeManager.GetTypeArguments (returnType);
2752
2753                                 // At least one unfixed return type has to exist
2754                                 if (AllTypesAreFixed (g_args))
2755                                         return false;
2756                         } else {
2757                                 return false;
2758                         }
2759
2760                         // All generic input arguments have to be fixed
2761                         AParametersCollection d_parameters = invoke.Parameters;
2762                         return AllTypesAreFixed (d_parameters.Types);
2763                 }
2764
2765                 bool IsFixed (TypeSpec type)
2766                 {
2767                         return IsUnfixed (type) == -1;
2768                 }
2769
2770                 int IsUnfixed (TypeSpec type)
2771                 {
2772                         if (!type.IsGenericParameter)
2773                                 return -1;
2774
2775                         //return unfixed_types[type.GenericParameterPosition] != null;
2776                         for (int i = 0; i < unfixed_types.Length; ++i) {
2777                                 if (unfixed_types [i] == type)
2778                                         return i;
2779                         }
2780
2781                         return -1;
2782                 }
2783
2784                 //
2785                 // 26.3.3.9 Lower-bound Inference
2786                 //
2787                 public int LowerBoundInference (TypeSpec u, TypeSpec v)
2788                 {
2789                         return LowerBoundInference (u, v, false);
2790                 }
2791
2792                 //
2793                 // Lower-bound (false) or Upper-bound (true) inference based on inversed argument
2794                 //
2795                 int LowerBoundInference (TypeSpec u, TypeSpec v, bool inversed)
2796                 {
2797                         // If V is one of the unfixed type arguments
2798                         int pos = IsUnfixed (v);
2799                         if (pos != -1) {
2800                                 AddToBounds (new BoundInfo (u, inversed ? BoundKind.Upper : BoundKind.Lower), pos);
2801                                 return 1;
2802                         }
2803
2804                         // If U is an array type
2805                         var u_ac = u as ArrayContainer;
2806                         if (u_ac != null) {
2807                                 var v_ac = v as ArrayContainer;
2808                                 if (v_ac != null) {
2809                                         if (u_ac.Rank != v_ac.Rank)
2810                                                 return 0;
2811
2812                                         if (TypeManager.IsValueType (u_ac.Element))
2813                                                 return ExactInference (u_ac.Element, v_ac.Element);
2814
2815                                         return LowerBoundInference (u_ac.Element, v_ac.Element, inversed);
2816                                 }
2817
2818                                 if (u_ac.Rank != 1)
2819                                         return 0;
2820
2821                                 if (TypeManager.IsGenericType (v)) {
2822                                         TypeSpec g_v = v.GetDefinition ();
2823                                         if (g_v != TypeManager.generic_ilist_type &&
2824                                                 g_v != TypeManager.generic_icollection_type &&
2825                                                 g_v != TypeManager.generic_ienumerable_type)
2826                                                 return 0;
2827
2828                                         var v_i = TypeManager.GetTypeArguments (v) [0];
2829                                         if (TypeManager.IsValueType (u_ac.Element))
2830                                                 return ExactInference (u_ac.Element, v_i);
2831
2832                                         return LowerBoundInference (u_ac.Element, v_i);
2833                                 }
2834                         } else if (TypeManager.IsGenericType (v)) {
2835                                 //
2836                                 // if V is a constructed type C<V1..Vk> and there is a unique type C<U1..Uk>
2837                                 // such that U is identical to, inherits from (directly or indirectly),
2838                                 // or implements (directly or indirectly) C<U1..Uk>
2839                                 //
2840                                 var u_candidates = new List<TypeSpec> ();
2841                                 var open_v = v.MemberDefinition;
2842
2843                                 for (TypeSpec t = u; t != null; t = t.BaseType) {
2844                                         if (open_v == t.MemberDefinition)
2845                                                 u_candidates.Add (t);
2846
2847                                         if (t.Interfaces != null) {
2848                                                 foreach (var iface in t.Interfaces) {
2849                                                         if (open_v == iface.MemberDefinition)
2850                                                                 u_candidates.Add (iface);
2851                                                 }
2852                                         }
2853                                 }
2854
2855                                 TypeSpec [] unique_candidate_targs = null;
2856                                 TypeSpec[] ga_v = TypeManager.GetTypeArguments (v);
2857                                 foreach (TypeSpec u_candidate in u_candidates) {
2858                                         //
2859                                         // The unique set of types U1..Uk means that if we have an interface I<T>,
2860                                         // class U : I<int>, I<long> then no type inference is made when inferring
2861                                         // type I<T> by applying type U because T could be int or long
2862                                         //
2863                                         if (unique_candidate_targs != null) {
2864                                                 TypeSpec[] second_unique_candidate_targs = TypeManager.GetTypeArguments (u_candidate);
2865                                                 if (TypeSpecComparer.Equals (unique_candidate_targs, second_unique_candidate_targs)) {
2866                                                         unique_candidate_targs = second_unique_candidate_targs;
2867                                                         continue;
2868                                                 }
2869
2870                                                 //
2871                                                 // This should always cause type inference failure
2872                                                 //
2873                                                 failed = true;
2874                                                 return 1;
2875                                         }
2876
2877                                         unique_candidate_targs = TypeManager.GetTypeArguments (u_candidate);
2878                                 }
2879
2880                                 if (unique_candidate_targs != null) {
2881                                         var ga_open_v = open_v.TypeParameters;
2882                                         int score = 0;
2883                                         for (int i = 0; i < unique_candidate_targs.Length; ++i) {
2884                                                 Variance variance = ga_open_v [i].Variance;
2885
2886                                                 TypeSpec u_i = unique_candidate_targs [i];
2887                                                 if (variance == Variance.None || TypeManager.IsValueType (u_i)) {
2888                                                         if (ExactInference (u_i, ga_v [i]) == 0)
2889                                                                 ++score;
2890                                                 } else {
2891                                                         bool upper_bound = (variance == Variance.Contravariant && !inversed) ||
2892                                                                 (variance == Variance.Covariant && inversed);
2893
2894                                                         if (LowerBoundInference (u_i, ga_v [i], upper_bound) == 0)
2895                                                                 ++score;
2896                                                 }
2897                                         }
2898                                         return score;
2899                                 }
2900                         }
2901
2902                         return 0;
2903                 }
2904
2905                 //
2906                 // 26.3.3.6 Output Type Inference
2907                 //
2908                 public int OutputTypeInference (ResolveContext ec, Expression e, TypeSpec t)
2909                 {
2910                         // If e is a lambda or anonymous method with inferred return type
2911                         AnonymousMethodExpression ame = e as AnonymousMethodExpression;
2912                         if (ame != null) {
2913                                 TypeSpec rt = ame.InferReturnType (ec, this, t);
2914                                 var invoke = Delegate.GetInvokeMethod (ec.Compiler, t);
2915
2916                                 if (rt == null) {
2917                                         AParametersCollection pd = invoke.Parameters;
2918                                         return ame.Parameters.Count == pd.Count ? 1 : 0;
2919                                 }
2920
2921                                 TypeSpec rtype = invoke.ReturnType;
2922                                 return LowerBoundInference (rt, rtype) + 1;
2923                         }
2924
2925                         //
2926                         // if E is a method group and T is a delegate type or expression tree type
2927                         // return type Tb with parameter types T1..Tk and return type Tb, and overload
2928                         // resolution of E with the types T1..Tk yields a single method with return type U,
2929                         // then a lower-bound inference is made from U for Tb.
2930                         //
2931                         if (e is MethodGroupExpr) {
2932                                 if (!TypeManager.IsDelegateType (t)) {
2933                                         if (TypeManager.expression_type == null || t.MemberDefinition != TypeManager.expression_type.MemberDefinition)
2934                                                 return 0;
2935
2936                                         t = TypeManager.GetTypeArguments (t)[0];
2937                                 }
2938
2939                                 var invoke = Delegate.GetInvokeMethod (ec.Compiler, t);
2940                                 TypeSpec rtype = invoke.ReturnType;
2941
2942                                 if (!rtype.IsGenericParameter && !TypeManager.IsGenericType (rtype))
2943                                         return 0;
2944
2945                                 // LAMESPEC: Standard does not specify that all methodgroup arguments
2946                                 // has to be fixed but it does not specify how to do recursive type inference
2947                                 // either. We choose the simple option and infer return type only
2948                                 // if all delegate generic arguments are fixed.
2949                                 TypeSpec[] param_types = new TypeSpec [invoke.Parameters.Count];
2950                                 for (int i = 0; i < param_types.Length; ++i) {
2951                                         var inflated = InflateGenericArgument (invoke.Parameters.Types[i]);
2952                                         if (inflated == null)
2953                                                 return 0;
2954
2955                                         param_types[i] = inflated;
2956                                 }
2957
2958                                 MethodGroupExpr mg = (MethodGroupExpr) e;
2959                                 Arguments args = DelegateCreation.CreateDelegateMethodArguments (invoke.Parameters, param_types, e.Location);
2960                                 mg = mg.OverloadResolve (ec, ref args, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly);
2961                                 if (mg == null)
2962                                         return 0;
2963
2964                                 return LowerBoundInference (mg.BestCandidate.ReturnType, rtype) + 1;
2965                         }
2966
2967                         //
2968                         // if e is an expression with type U, then
2969                         // a lower-bound inference is made from U for T
2970                         //
2971                         return LowerBoundInference (e.Type, t) * 2;
2972                 }
2973
2974                 void RemoveDependentTypes (List<TypeSpec> types, TypeSpec returnType)
2975                 {
2976                         int idx = IsUnfixed (returnType);
2977                         if (idx >= 0) {
2978                                 types [idx] = null;
2979                                 return;
2980                         }
2981
2982                         if (TypeManager.IsGenericType (returnType)) {
2983                                 foreach (TypeSpec t in TypeManager.GetTypeArguments (returnType)) {
2984                                         RemoveDependentTypes (types, t);
2985                                 }
2986                         }
2987                 }
2988
2989                 public bool UnfixedVariableExists {
2990                         get {
2991                                 if (unfixed_types == null)
2992                                         return false;
2993
2994                                 foreach (TypeSpec ut in unfixed_types)
2995                                         if (ut != null)
2996                                                 return true;
2997                                 return false;
2998                         }
2999                 }
3000         }
3001 }