mcs/gmcs/generic.cs

   1 //
   2 // generic.cs: Generics support
   3 //
   4 // Authors: Martin Baulig (martin@ximian.com)
   5 //          Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // Licensed under the terms of the GNU GPL
   8 //
   9 // (C) 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
  10 // (C) 2004 Novell, Inc
  11 //
  12 using System;
  13 using System.Reflection;
  14 using System.Reflection.Emit;
  15 using System.Globalization;
  16 using System.Collections;
  17 using System.Text;
  18 using System.Text.RegularExpressions;
  19
  20 namespace Mono.CSharp {
  21
  22         /// <summary>
  23         ///   Abstract base class for type parameter constraints.
  24         ///   The type parameter can come from a generic type definition or from reflection.
  25         /// </summary>
  26         public abstract class GenericConstraints {
  27                 public abstract string TypeParameter {
  28                         get;
  29                 }
  30
  31                 public abstract GenericParameterAttributes Attributes {
  32                         get;
  33                 }
  34
  35                 public bool HasConstructorConstraint {
  36                         get { return (Attributes & GenericParameterAttributes.DefaultConstructorConstraint) != 0; }
  37                 }
  38
  39                 public bool HasReferenceTypeConstraint {
  40                         get { return (Attributes & GenericParameterAttributes.ReferenceTypeConstraint) != 0; }
  41                 }
  42
  43                 public bool HasValueTypeConstraint {
  44                         get { return (Attributes & GenericParameterAttributes.NotNullableValueTypeConstraint) != 0; }
  45                 }
  46
  47                 public virtual bool HasClassConstraint {
  48                         get { return ClassConstraint != null; }
  49                 }
  50
  51                 public abstract Type ClassConstraint {
  52                         get;
  53                 }
  54
  55                 public abstract Type[] InterfaceConstraints {
  56                         get;
  57                 }
  58
  59                 public abstract Type EffectiveBaseClass {
  60                         get;
  61                 }
  62
  63                 // <summary>
  64                 //   Returns whether the type parameter is "known to be a reference type".
  65                 // </summary>
  66                 public virtual bool IsReferenceType {
  67                         get {
  68                                 if (HasReferenceTypeConstraint)
  69                                         return true;
  70                                 if (HasValueTypeConstraint)
  71                                         return false;
  72
  73                                 if (ClassConstraint != null) {
  74                                         if (ClassConstraint.IsValueType)
  75                                                 return false;
  76
  77                                         if (ClassConstraint != TypeManager.object_type)
  78                                                 return true;
  79                                 }
  80
  81                                 foreach (Type t in InterfaceConstraints) {
  82                                         if (!t.IsGenericParameter)
  83                                                 continue;
  84
  85                                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (t);
  86                                         if ((gc != null) && gc.IsReferenceType)
  87                                                 return true;
  88                                 }
  89
  90                                 return false;
  91                         }
  92                 }
  93
  94                 // <summary>
  95                 //   Returns whether the type parameter is "known to be a value type".
  96                 // </summary>
  97                 public virtual bool IsValueType {
  98                         get {
  99                                 if (HasValueTypeConstraint)
 100                                         return true;
 101                                 if (HasReferenceTypeConstraint)
 102                                         return false;
 103
 104                                 if (ClassConstraint != null) {
 105                                         if (!ClassConstraint.IsValueType)
 106                                                 return false;
 107
 108                                         if (ClassConstraint != TypeManager.value_type)
 109                                                 return true;
 110                                 }
 111
 112                                 foreach (Type t in InterfaceConstraints) {
 113                                         if (!t.IsGenericParameter)
 114                                                 continue;
 115
 116                                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (t);
 117                                         if ((gc != null) && gc.IsValueType)
 118                                                 return true;
 119                                 }
 120
 121                                 return false;
 122                         }
 123                 }
 124         }
 125
 126         public enum SpecialConstraint
 127         {
 128                 Constructor,
 129                 ReferenceType,
 130                 ValueType
 131         }
 132
 133         /// <summary>
 134         ///   Tracks the constraints for a type parameter from a generic type definition.
 135         /// </summary>
 136         public class Constraints : GenericConstraints {
 137                 string name;
 138                 ArrayList constraints;
 139                 Location loc;
 140
 141                 //
 142                 // name is the identifier, constraints is an arraylist of
 143                 // Expressions (with types) or `true' for the constructor constraint.
 144                 //
 145                 public Constraints (string name, ArrayList constraints,
 146                                     Location loc)
 147                 {
 148                         this.name = name;
 149                         this.constraints = constraints;
 150                         this.loc = loc;
 151                 }
 152
 153                 public override string TypeParameter {
 154                         get {
 155                                 return name;
 156                         }
 157                 }
 158
 159                 GenericParameterAttributes attrs;
 160                 TypeExpr class_constraint;
 161                 ArrayList iface_constraints;
 162                 ArrayList type_param_constraints;
 163                 int num_constraints;
 164                 Type class_constraint_type;
 165                 Type[] iface_constraint_types;
 166                 Type effective_base_type;
 167                 bool resolved;
 168                 bool resolved_types;
 169
 170                 /// <summary>
 171                 ///   Resolve the constraints - but only resolve things into Expression's, not
 172                 ///   into actual types.
 173                 /// </summary>
 174                 public bool Resolve (IResolveContext ec)
 175                 {
 176                         if (resolved)
 177                                 return true;
 178
 179                         iface_constraints = new ArrayList ();
 180                         type_param_constraints = new ArrayList ();
 181
 182                         foreach (object obj in constraints) {
 183                                 if (HasConstructorConstraint) {
 184                                         Report.Error (401, loc,
 185                                                       "The new() constraint must be last.");
 186                                         return false;
 187                                 }
 188
 189                                 if (obj is SpecialConstraint) {
 190                                         SpecialConstraint sc = (SpecialConstraint) obj;
 191
 192                                         if (sc == SpecialConstraint.Constructor) {
 193                                                 if (!HasValueTypeConstraint) {
 194                                                         attrs |= GenericParameterAttributes.DefaultConstructorConstraint;
 195                                                         continue;
 196                                                 }
 197
 198                                                 Report.Error (
 199                                                         451, loc, "The new () constraint " +
 200                                                         "cannot be used with the `struct' " +
 201                                                         "constraint.");
 202                                                 return false;
 203                                         }
 204
 205                                         if ((num_constraints > 0) || HasReferenceTypeConstraint || HasValueTypeConstraint) {
 206                                                 Report.Error (449, loc,
 207                                                               "The `class' or `struct' " +
 208                                                               "constraint must be first");
 209                                                 return false;
 210                                         }
 211
 212                                         if (sc == SpecialConstraint.ReferenceType)
 213                                                 attrs |= GenericParameterAttributes.ReferenceTypeConstraint;
 214                                         else
 215                                                 attrs |= GenericParameterAttributes.NotNullableValueTypeConstraint;
 216                                         continue;
 217                                 }
 218
 219                                 int errors = Report.Errors;
 220                                 FullNamedExpression fn = ((Expression) obj).ResolveAsTypeStep (ec, false);
 221
 222                                 if (fn == null) {
 223                                         if (errors != Report.Errors)
 224                                                 return false;
 225
 226                                         Report.Error (246, loc, "Cannot find type '{0}'", ((Expression) obj).GetSignatureForError ());
 227                                         return false;
 228                                 }
 229
 230                                 TypeExpr expr;
 231                                 ConstructedType cexpr = fn as ConstructedType;
 232                                 if (cexpr != null) {
 233                                         if (!cexpr.ResolveConstructedType (ec))
 234                                                 return false;
 235
 236                                         expr = cexpr;
 237                                 } else
 238                                         expr = fn.ResolveAsTypeTerminal (ec, false);
 239
 240                                 if ((expr == null) || (expr.Type == null))
 241                                         return false;
 242
 243                                 TypeParameterExpr texpr = expr as TypeParameterExpr;
 244                                 if (texpr != null)
 245                                         type_param_constraints.Add (expr);
 246                                 else if (expr.IsInterface)
 247                                         iface_constraints.Add (expr);
 248                                 else if (class_constraint != null) {
 249                                         Report.Error (406, loc,
 250                                                       "`{0}': the class constraint for `{1}' " +
 251                                                       "must come before any other constraints.",
 252                                                       expr.Name, name);
 253                                         return false;
 254                                 } else if (HasReferenceTypeConstraint || HasValueTypeConstraint) {
 255                                         Report.Error (450, loc, "`{0}': cannot specify both " +
 256                                                       "a constraint class and the `class' " +
 257                                                       "or `struct' constraint.", expr.Name);
 258                                         return false;
 259                                 } else
 260                                         class_constraint = expr;
 261
 262                                 num_constraints++;
 263                         }
 264
 265                         ArrayList list = new ArrayList ();
 266                         foreach (TypeExpr iface_constraint in iface_constraints) {
 267                                 foreach (Type type in list) {
 268                                         if (!type.Equals (iface_constraint.Type))
 269                                                 continue;
 270
 271                                         Report.Error (405, loc,
 272                                                       "Duplicate constraint `{0}' for type " +
 273                                                       "parameter `{1}'.", iface_constraint.GetSignatureForError (),
 274                                                       name);
 275                                         return false;
 276                                 }
 277
 278                                 list.Add (iface_constraint.Type);
 279                         }
 280
 281                         foreach (TypeParameterExpr expr in type_param_constraints) {
 282                                 foreach (Type type in list) {
 283                                         if (!type.Equals (expr.Type))
 284                                                 continue;
 285
 286                                         Report.Error (405, loc,
 287                                                       "Duplicate constraint `{0}' for type " +
 288                                                       "parameter `{1}'.", expr.GetSignatureForError (), name);
 289                                         return false;
 290                                 }
 291
 292                                 list.Add (expr.Type);
 293                         }
 294
 295                         iface_constraint_types = new Type [list.Count];
 296                         list.CopyTo (iface_constraint_types, 0);
 297
 298                         if (class_constraint != null) {
 299                                 class_constraint_type = class_constraint.Type;
 300                                 if (class_constraint_type == null)
 301                                         return false;
 302
 303                                 if (class_constraint_type.IsSealed) {
 304                                         Report.Error (701, loc,
 305                                                       "`{0}' is not a valid bound.  Bounds " +
 306                                                       "must be interfaces or non sealed " +
 307                                                       "classes", TypeManager.CSharpName (class_constraint_type));
 308                                         return false;
 309                                 }
 310
 311                                 if ((class_constraint_type == TypeManager.array_type) ||
 312                                     (class_constraint_type == TypeManager.delegate_type) ||
 313                                     (class_constraint_type == TypeManager.enum_type) ||
 314                                     (class_constraint_type == TypeManager.value_type) ||
 315                                     (class_constraint_type == TypeManager.object_type)) {
 316                                         Report.Error (702, loc,
 317                                                       "Bound cannot be special class `{0}'",
 318                                                       TypeManager.CSharpName (class_constraint_type));
 319                                         return false;
 320                                 }
 321                         }
 322
 323                         if (class_constraint_type != null)
 324                                 effective_base_type = class_constraint_type;
 325                         else if (HasValueTypeConstraint)
 326                                 effective_base_type = TypeManager.value_type;
 327                         else
 328                                 effective_base_type = TypeManager.object_type;
 329
 330                         resolved = true;
 331                         return true;
 332                 }
 333
 334                 bool CheckTypeParameterConstraints (TypeParameter tparam, Hashtable seen)
 335                 {
 336                         seen.Add (tparam, true);
 337
 338                         Constraints constraints = tparam.Constraints;
 339                         if (constraints == null)
 340                                 return true;
 341
 342                         if (constraints.HasValueTypeConstraint) {
 343                                 Report.Error (456, loc, "Type parameter `{0}' has " +
 344                                               "the `struct' constraint, so it cannot " +
 345                                               "be used as a constraint for `{1}'",
 346                                               tparam.Name, name);
 347                                 return false;
 348                         }
 349
 350                         if (constraints.type_param_constraints == null)
 351                                 return true;
 352
 353                         foreach (TypeParameterExpr expr in constraints.type_param_constraints) {
 354                                 if (seen.Contains (expr.TypeParameter)) {
 355                                         Report.Error (454, loc, "Circular constraint " +
 356                                                       "dependency involving `{0}' and `{1}'",
 357                                                       tparam.Name, expr.Name);
 358                                         return false;
 359                                 }
 360
 361                                 if (!CheckTypeParameterConstraints (expr.TypeParameter, seen))
 362                                         return false;
 363                         }
 364
 365                         return true;
 366                 }
 367
 368                 /// <summary>
 369                 ///   Resolve the constraints into actual types.
 370                 /// </summary>
 371                 public bool ResolveTypes (IResolveContext ec)
 372                 {
 373                         if (resolved_types)
 374                                 return true;
 375
 376                         resolved_types = true;
 377
 378                         foreach (object obj in constraints) {
 379                                 ConstructedType cexpr = obj as ConstructedType;
 380                                 if (cexpr == null)
 381                                         continue;
 382
 383                                 if (!cexpr.CheckConstraints (ec))
 384                                         return false;
 385                         }
 386
 387                         foreach (TypeParameterExpr expr in type_param_constraints) {
 388                                 Hashtable seen = new Hashtable ();
 389                                 if (!CheckTypeParameterConstraints (expr.TypeParameter, seen))
 390                                         return false;
 391                         }
 392
 393                         for (int i = 0; i < iface_constraints.Count; ++i) {
 394                                 TypeExpr iface_constraint = (TypeExpr) iface_constraints [i];
 395                                 iface_constraint = iface_constraint.ResolveAsTypeTerminal (ec, false);
 396                                 if (iface_constraint == null)
 397                                         return false;
 398                                 iface_constraints [i] = iface_constraint;
 399                         }
 400
 401                         if (class_constraint != null) {
 402                                 class_constraint = class_constraint.ResolveAsTypeTerminal (ec, false);
 403                                 if (class_constraint == null)
 404                                         return false;
 405                         }
 406
 407                         return true;
 408                 }
 409
 410                 /// <summary>
 411                 ///   Check whether there are no conflicts in our type parameter constraints.
 412                 ///
 413                 ///   This is an example:
 414                 ///
 415                 ///   class Foo<T,U>
 416                 ///      where T : class
 417                 ///      where U : T, struct
 418                 /// </summary>
 419                 public bool CheckDependencies ()
 420                 {
 421                         foreach (TypeParameterExpr expr in type_param_constraints) {
 422                                 if (!CheckDependencies (expr.TypeParameter))
 423                                         return false;
 424                         }
 425
 426                         return true;
 427                 }
 428
 429                 bool CheckDependencies (TypeParameter tparam)
 430                 {
 431                         Constraints constraints = tparam.Constraints;
 432                         if (constraints == null)
 433                                 return true;
 434
 435                         if (HasValueTypeConstraint && constraints.HasClassConstraint) {
 436                                 Report.Error (455, loc, "Type parameter `{0}' inherits " +
 437                                               "conflicting constraints `{1}' and `{2}'",
 438                                               name, TypeManager.CSharpName (constraints.ClassConstraint),
 439                                               "System.ValueType");
 440                                 return false;
 441                         }
 442
 443                         if (HasClassConstraint && constraints.HasClassConstraint) {
 444                                 Type t1 = ClassConstraint;
 445                                 TypeExpr e1 = class_constraint;
 446                                 Type t2 = constraints.ClassConstraint;
 447                                 TypeExpr e2 = constraints.class_constraint;
 448
 449                                 if (!Convert.ImplicitReferenceConversionExists (e1, t2) &&
 450                                     !Convert.ImplicitReferenceConversionExists (e2, t1)) {
 451                                         Report.Error (455, loc,
 452                                                       "Type parameter `{0}' inherits " +
 453                                                       "conflicting constraints `{1}' and `{2}'",
 454                                                       name, TypeManager.CSharpName (t1), TypeManager.CSharpName (t2));
 455                                         return false;
 456                                 }
 457                         }
 458
 459                         if (constraints.type_param_constraints == null)
 460                                 return true;
 461
 462                         foreach (TypeParameterExpr expr in constraints.type_param_constraints) {
 463                                 if (!CheckDependencies (expr.TypeParameter))
 464                                         return false;
 465                         }
 466
 467                         return true;
 468                 }
 469
 470                 public override GenericParameterAttributes Attributes {
 471                         get { return attrs; }
 472                 }
 473
 474                 public override bool HasClassConstraint {
 475                         get { return class_constraint != null; }
 476                 }
 477
 478                 public override Type ClassConstraint {
 479                         get { return class_constraint_type; }
 480                 }
 481
 482                 public override Type[] InterfaceConstraints {
 483                         get { return iface_constraint_types; }
 484                 }
 485
 486                 public override Type EffectiveBaseClass {
 487                         get { return effective_base_type; }
 488                 }
 489
 490                 public bool IsSubclassOf (Type t)
 491                 {
 492                         if ((class_constraint_type != null) &&
 493                             class_constraint_type.IsSubclassOf (t))
 494                                 return true;
 495
 496                         if (iface_constraint_types == null)
 497                                 return false;
 498
 499                         foreach (Type iface in iface_constraint_types) {
 500                                 if (TypeManager.IsSubclassOf (iface, t))
 501                                         return true;
 502                         }
 503
 504                         return false;
 505                 }
 506
 507                 /// <summary>
 508                 ///   This is used when we're implementing a generic interface method.
 509                 ///   Each method type parameter in implementing method must have the same
 510                 ///   constraints than the corresponding type parameter in the interface
 511                 ///   method.  To do that, we're called on each of the implementing method's
 512                 ///   type parameters.
 513                 /// </summary>
 514                 public bool CheckInterfaceMethod (GenericConstraints gc)
 515                 {
 516                         if (gc.Attributes != attrs)
 517                                 return false;
 518
 519                         if (HasClassConstraint != gc.HasClassConstraint)
 520                                 return false;
 521                         if (HasClassConstraint && !TypeManager.IsEqual (gc.ClassConstraint, ClassConstraint))
 522                                 return false;
 523
 524                         int gc_icount = gc.InterfaceConstraints != null ?
 525                                 gc.InterfaceConstraints.Length : 0;
 526                         int icount = InterfaceConstraints != null ?
 527                                 InterfaceConstraints.Length : 0;
 528
 529                         if (gc_icount != icount)
 530                                 return false;
 531
 532                         foreach (Type iface in gc.InterfaceConstraints) {
 533                                 bool ok = false;
 534                                 foreach (Type check in InterfaceConstraints) {
 535                                         if (TypeManager.IsEqual (iface, check)) {
 536                                                 ok = true;
 537                                                 break;
 538                                         }
 539                                 }
 540
 541                                 if (!ok)
 542                                         return false;
 543                         }
 544
 545                         return true;
 546                 }
 547         }
 548
 549         /// <summary>
 550         ///   A type parameter from a generic type definition.
 551         /// </summary>
 552         public class TypeParameter : MemberCore, IMemberContainer {
 553                 string name;
 554                 DeclSpace decl;
 555                 GenericConstraints gc;
 556                 Constraints constraints;
 557                 Location loc;
 558                 GenericTypeParameterBuilder type;
 559
 560                 public TypeParameter (DeclSpace parent, DeclSpace decl, string name,
 561                                       Constraints constraints, Attributes attrs, Location loc)
 562                         : base (parent, new MemberName (name, loc), attrs)
 563                 {
 564                         this.name = name;
 565                         this.decl = decl;
 566                         this.constraints = constraints;
 567                         this.loc = loc;
 568                 }
 569
 570                 public GenericConstraints GenericConstraints {
 571                         get {
 572                                 return gc != null ? gc : constraints;
 573                         }
 574                 }
 575
 576                 public Constraints Constraints {
 577                         get {
 578                                 return constraints;
 579                         }
 580                 }
 581
 582                 public bool HasConstructorConstraint {
 583                         get {
 584                                 if (constraints != null)
 585                                         return constraints.HasConstructorConstraint;
 586
 587                                 return false;
 588                         }
 589                 }
 590
 591                 public DeclSpace DeclSpace {
 592                         get {
 593                                 return decl;
 594                         }
 595                 }
 596
 597                 public Type Type {
 598                         get {
 599                                 return type;
 600                         }
 601                 }
 602
 603                 // FIXME: This should be removed once we fix the handling of RootContext.Tree.Types
 604                 public override DeclSpace DeclContainer {
 605                         get { return DeclSpace; }
 606                 }
 607
 608                 /// <summary>
 609                 ///   This is the first method which is called during the resolving
 610                 ///   process; we're called immediately after creating the type parameters
 611                 ///   with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
 612                 ///   MethodBuilder).
 613                 ///
 614                 ///   We're either called from TypeContainer.DefineType() or from
 615                 ///   GenericMethod.Define() (called from Method.Define()).
 616                 /// </summary>
 617                 public void Define (GenericTypeParameterBuilder type)
 618                 {
 619                         if (this.type != null)
 620                                 throw new InvalidOperationException ();
 621
 622                         this.type = type;
 623                         TypeManager.AddTypeParameter (type, this);
 624                 }
 625
 626                 /// <summary>
 627                 ///   This is the second method which is called during the resolving
 628                 ///   process - in case of class type parameters, we're called from
 629                 ///   TypeContainer.ResolveType() - after it resolved the class'es
 630                 ///   base class and interfaces. For method type parameters, we're
 631                 ///   called immediately after Define().
 632                 ///
 633                 ///   We're just resolving the constraints into expressions here, we
 634                 ///   don't resolve them into actual types.
 635                 ///
 636                 ///   Note that in the special case of partial generic classes, we may be
 637                 ///   called _before_ Define() and we may also be called multiple types.
 638                 /// </summary>
 639                 public bool Resolve (DeclSpace ds)
 640                 {
 641                         if (constraints != null) {
 642                                 if (!constraints.Resolve (ds)) {
 643                                         constraints = null;
 644                                         return false;
 645                                 }
 646                         }
 647
 648                         return true;
 649                 }
 650
 651                 /// <summary>
 652                 ///   This is the third method which is called during the resolving
 653                 ///   process.  We're called immediately after calling DefineConstraints()
 654                 ///   on all of the current class'es type parameters.
 655                 ///
 656                 ///   Our job is to resolve the constraints to actual types.
 657                 ///
 658                 ///   Note that we may have circular dependencies on type parameters - this
 659                 ///   is why Resolve() and ResolveType() are separate.
 660                 /// </summary>
 661                 public bool ResolveType (IResolveContext ec)
 662                 {
 663                         if (constraints != null) {
 664                                 if (!constraints.ResolveTypes (ec)) {
 665                                         constraints = null;
 666                                         return false;
 667                                 }
 668                         }
 669
 670                         return true;
 671                 }
 672
 673                 /// <summary>
 674                 ///   This is the fourth and last method which is called during the resolving
 675                 ///   process.  We're called after everything is fully resolved and actually
 676                 ///   register the constraints with SRE and the TypeManager.
 677                 /// </summary>
 678                 public bool DefineType (IResolveContext ec)
 679                 {
 680                         return DefineType (ec, null, null, false);
 681                 }
 682
 683                 /// <summary>
 684                 ///   This is the fith and last method which is called during the resolving
 685                 ///   process.  We're called after everything is fully resolved and actually
 686                 ///   register the constraints with SRE and the TypeManager.
 687                 ///
 688                 ///   The `builder', `implementing' and `is_override' arguments are only
 689                 ///   applicable to method type parameters.
 690                 /// </summary>
 691                 public bool DefineType (IResolveContext ec, MethodBuilder builder,
 692                                         MethodInfo implementing, bool is_override)
 693                 {
 694                         if (!ResolveType (ec))
 695                                 return false;
 696
 697                         if (implementing != null) {
 698                                 if (is_override && (constraints != null)) {
 699                                         Report.Error (
 700                                                 460, loc, "Constraints for override and " +
 701                                                 "explicit interface implementation methods " +
 702                                                 "are inherited from the base method so they " +
 703                                                 "cannot be specified directly");
 704                                         return false;
 705                                 }
 706
 707                                 MethodBase mb = TypeManager.DropGenericMethodArguments (implementing);
 708
 709                                 int pos = type.GenericParameterPosition;
 710                                 Type mparam = mb.GetGenericArguments () [pos];
 711                                 GenericConstraints temp_gc = ReflectionConstraints.GetConstraints (mparam);
 712
 713                                 if (temp_gc != null)
 714                                         gc = new InflatedConstraints (temp_gc, implementing.DeclaringType);
 715                                 else if (constraints != null)
 716                                         gc = new InflatedConstraints (constraints, implementing.DeclaringType);
 717
 718                                 bool ok = true;
 719                                 if (constraints != null) {
 720                                         if (temp_gc == null)
 721                                                 ok = false;
 722                                         else if (!constraints.CheckInterfaceMethod (gc))
 723                                                 ok = false;
 724                                 } else {
 725                                         if (!is_override && (temp_gc != null))
 726                                                 ok = false;
 727                                 }
 728
 729                                 if (!ok) {
 730                                         Report.SymbolRelatedToPreviousError (implementing);
 731
 732                                         Report.Error (
 733                                                 425, loc, "The constraints for type " +
 734                                                 "parameter `{0}' of method `{1}' must match " +
 735                                                 "the constraints for type parameter `{2}' " +
 736                                                 "of interface method `{3}'. Consider using " +
 737                                                 "an explicit interface implementation instead",
 738                                                 Name, TypeManager.CSharpSignature (builder),
 739                                                 TypeManager.CSharpName (mparam), TypeManager.CSharpSignature (mb));
 740                                         return false;
 741                                 }
 742                         } else if (DeclSpace is Iterator) {
 743                                 TypeParameter[] tparams = DeclSpace.TypeParameters;
 744                                 Type[] types = new Type [tparams.Length];
 745                                 for (int i = 0; i < tparams.Length; i++)
 746                                         types [i] = tparams [i].Type;
 747
 748                                 if (constraints != null)
 749                                         gc = new InflatedConstraints (constraints, types);
 750                         } else {
 751                                 gc = (GenericConstraints) constraints;
 752                         }
 753
 754                         if (gc == null)
 755                                 return true;
 756
 757                         if (gc.HasClassConstraint)
 758                                 type.SetBaseTypeConstraint (gc.ClassConstraint);
 759
 760                         type.SetInterfaceConstraints (gc.InterfaceConstraints);
 761                         type.SetGenericParameterAttributes (gc.Attributes);
 762                         TypeManager.RegisterBuilder (type, gc.InterfaceConstraints);
 763
 764                         return true;
 765                 }
 766
 767                 /// <summary>
 768                 ///   Check whether there are no conflicts in our type parameter constraints.
 769                 ///
 770                 ///   This is an example:
 771                 ///
 772                 ///   class Foo<T,U>
 773                 ///      where T : class
 774                 ///      where U : T, struct
 775                 /// </summary>
 776                 public bool CheckDependencies ()
 777                 {
 778                         if (constraints != null)
 779                                 return constraints.CheckDependencies ();
 780
 781                         return true;
 782                 }
 783
 784                 /// <summary>
 785                 ///   This is called for each part of a partial generic type definition.
 786                 ///
 787                 ///   If `new_constraints' is not null and we don't already have constraints,
 788                 ///   they become our constraints.  If we already have constraints, we must
 789                 ///   check that they're the same.
 790                 ///   con
 791                 /// </summary>
 792                 public bool UpdateConstraints (IResolveContext ec, Constraints new_constraints)
 793                 {
 794                         if (type == null)
 795                                 throw new InvalidOperationException ();
 796
 797                         if (new_constraints == null)
 798                                 return true;
 799
 800                         if (!new_constraints.Resolve (ec))
 801                                 return false;
 802                         if (!new_constraints.ResolveTypes (ec))
 803                                 return false;
 804
 805                         if (constraints != null)
 806                                 return constraints.CheckInterfaceMethod (new_constraints);
 807
 808                         constraints = new_constraints;
 809                         return true;
 810                 }
 811
 812                 public void EmitAttributes ()
 813                 {
 814                         if (OptAttributes != null)
 815                                 OptAttributes.Emit ();
 816                 }
 817
 818                 public override string DocCommentHeader {
 819                         get {
 820                                 throw new InvalidOperationException (
 821                                         "Unexpected attempt to get doc comment from " + this.GetType () + ".");
 822                         }
 823                 }
 824
 825                 //
 826                 // MemberContainer
 827                 //
 828
 829                 public override bool Define ()
 830                 {
 831                         return true;
 832                 }
 833
 834                 public override void ApplyAttributeBuilder (Attribute a,
 835                                                             CustomAttributeBuilder cb)
 836                 {
 837                         type.SetCustomAttribute (cb);
 838                 }
 839
 840                 public override AttributeTargets AttributeTargets {
 841                         get {
 842                                 return (AttributeTargets) AttributeTargets.GenericParameter;
 843                         }
 844                 }
 845
 846                 public override string[] ValidAttributeTargets {
 847                         get {
 848                                 return new string [] { "type parameter" };
 849                         }
 850                 }
 851
 852                 //
 853                 // IMemberContainer
 854                 //
 855
 856                 string IMemberContainer.Name {
 857                         get { return Name; }
 858                 }
 859
 860                 MemberCache IMemberContainer.BaseCache {
 861                         get { return null; }
 862                 }
 863
 864                 bool IMemberContainer.IsInterface {
 865                         get { return true; }
 866                 }
 867
 868                 MemberList IMemberContainer.GetMembers (MemberTypes mt, BindingFlags bf)
 869                 {
 870                         return FindMembers (mt, bf, null, null);
 871                 }
 872
 873                 MemberCache IMemberContainer.MemberCache {
 874                         get { return null; }
 875                 }
 876
 877                 public MemberList FindMembers (MemberTypes mt, BindingFlags bf,
 878                                                MemberFilter filter, object criteria)
 879                 {
 880                         if (constraints == null)
 881                                 return MemberList.Empty;
 882
 883                         ArrayList members = new ArrayList ();
 884
 885                         if (gc.HasClassConstraint) {
 886                                 MemberList list = TypeManager.FindMembers (
 887                                         gc.ClassConstraint, mt, bf, filter, criteria);
 888
 889                                 members.AddRange (list);
 890                         }
 891
 892                         Type[] ifaces = TypeManager.ExpandInterfaces (gc.InterfaceConstraints);
 893                         foreach (Type t in ifaces) {
 894                                 MemberList list = TypeManager.FindMembers (
 895                                         t, mt, bf, filter, criteria);
 896
 897                                 members.AddRange (list);
 898                         }
 899
 900                         return new MemberList (members);
 901                 }
 902
 903                 public bool IsSubclassOf (Type t)
 904                 {
 905                         if (type.Equals (t))
 906                                 return true;
 907
 908                         if (constraints != null)
 909                                 return constraints.IsSubclassOf (t);
 910
 911                         return false;
 912                 }
 913
 914                 public override string ToString ()
 915                 {
 916                         return "TypeParameter[" + name + "]";
 917                 }
 918
 919                 public static string GetSignatureForError (TypeParameter[] tp)
 920                 {
 921                         if (tp == null || tp.Length == 0)
 922                                 return "";
 923
 924                         StringBuilder sb = new StringBuilder ("<");
 925                         for (int i = 0; i < tp.Length; ++i) {
 926                                 if (i > 0)
 927                                         sb.Append (",");
 928                                 sb.Append (tp[i].GetSignatureForError ());
 929                         }
 930                         sb.Append ('>');
 931                         return sb.ToString ();
 932                 }
 933
 934                 public void InflateConstraints (Type declaring)
 935                 {
 936                         if (constraints != null)
 937                                 gc = new InflatedConstraints (constraints, declaring);
 938                 }
 939
 940                 protected class InflatedConstraints : GenericConstraints
 941                 {
 942                         GenericConstraints gc;
 943                         Type base_type;
 944                         Type class_constraint;
 945                         Type[] iface_constraints;
 946                         Type[] dargs;
 947
 948                         public InflatedConstraints (GenericConstraints gc, Type declaring)
 949                                 : this (gc, TypeManager.GetTypeArguments (declaring))
 950                         { }
 951
 952                         public InflatedConstraints (GenericConstraints gc, Type[] dargs)
 953                         {
 954                                 this.gc = gc;
 955                                 this.dargs = dargs;
 956
 957                                 ArrayList list = new ArrayList ();
 958                                 if (gc.HasClassConstraint)
 959                                         list.Add (inflate (gc.ClassConstraint));
 960                                 foreach (Type iface in gc.InterfaceConstraints)
 961                                         list.Add (inflate (iface));
 962
 963                                 bool has_class_constr = false;
 964                                 if (list.Count > 0) {
 965                                         Type first = (Type) list [0];
 966                                         has_class_constr = !first.IsInterface && !first.IsGenericParameter;
 967                                 }
 968
 969                                 if ((list.Count > 0) && has_class_constr) {
 970                                         class_constraint = (Type) list [0];
 971                                         iface_constraints = new Type [list.Count - 1];
 972                                         list.CopyTo (1, iface_constraints, 0, list.Count - 1);
 973                                 } else {
 974                                         iface_constraints = new Type [list.Count];
 975                                         list.CopyTo (iface_constraints, 0);
 976                                 }
 977
 978                                 if (HasValueTypeConstraint)
 979                                         base_type = TypeManager.value_type;
 980                                 else if (class_constraint != null)
 981                                         base_type = class_constraint;
 982                                 else
 983                                         base_type = TypeManager.object_type;
 984                         }
 985
 986                         Type inflate (Type t)
 987                         {
 988                                 if (t == null)
 989                                         return null;
 990                                 if (t.IsGenericParameter)
 991                                         return dargs [t.GenericParameterPosition];
 992                                 if (t.IsGenericType) {
 993                                         Type[] args = t.GetGenericArguments ();
 994                                         Type[] inflated = new Type [args.Length];
 995
 996                                         for (int i = 0; i < args.Length; i++)
 997                                                 inflated [i] = inflate (args [i]);
 998
 999                                         t = t.GetGenericTypeDefinition ();
1000                                         t = t.MakeGenericType (inflated);
1001                                 }
1002
1003                                 return t;
1004                         }
1005
1006                         public override string TypeParameter {
1007                                 get { return gc.TypeParameter; }
1008                         }
1009
1010                         public override GenericParameterAttributes Attributes {
1011                                 get { return gc.Attributes; }
1012                         }
1013
1014                         public override Type ClassConstraint {
1015                                 get { return class_constraint; }
1016                         }
1017
1018                         public override Type EffectiveBaseClass {
1019                                 get { return base_type; }
1020                         }
1021
1022                         public override Type[] InterfaceConstraints {
1023                                 get { return iface_constraints; }
1024                         }
1025                 }
1026         }
1027
1028         /// <summary>
1029         ///   A TypeExpr which already resolved to a type parameter.
1030         /// </summary>
1031         public class TypeParameterExpr : TypeExpr {
1032                 TypeParameter type_parameter;
1033
1034                 public override string Name {
1035                         get {
1036                                 return type_parameter.Name;
1037                         }
1038                 }
1039
1040                 public override string FullName {
1041                         get {
1042                                 return type_parameter.Name;
1043                         }
1044                 }
1045
1046                 public TypeParameter TypeParameter {
1047                         get {
1048                                 return type_parameter;
1049                         }
1050                 }
1051
1052                 public TypeParameterExpr (TypeParameter type_parameter, Location loc)
1053                 {
1054                         this.type_parameter = type_parameter;
1055                         this.loc = loc;
1056                 }
1057
1058                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1059                 {
1060                         type = type_parameter.Type;
1061
1062                         return this;
1063                 }
1064
1065                 public override bool IsInterface {
1066                         get { return false; }
1067                 }
1068
1069                 public override bool CheckAccessLevel (DeclSpace ds)
1070                 {
1071                         return true;
1072                 }
1073
1074                 public void Error_CannotUseAsUnmanagedType (Location loc)
1075                 {
1076                         Report.Error (-203, loc, "Can not use type parameter as unmanaged type");
1077                 }
1078         }
1079
1080         /// <summary>
1081         ///   Tracks the type arguments when instantiating a generic type.  We're used in
1082         ///   ConstructedType.
1083         /// </summary>
1084         public class TypeArguments {
1085                 public readonly Location Location;
1086                 ArrayList args;
1087                 Type[] atypes;
1088                 int dimension;
1089                 bool has_type_args;
1090                 bool created;
1091
1092                 public TypeArguments (Location loc)
1093                 {
1094                         args = new ArrayList ();
1095                         this.Location = loc;
1096                 }
1097
1098                 public TypeArguments (int dimension, Location loc)
1099                 {
1100                         this.dimension = dimension;
1101                         this.Location = loc;
1102                 }
1103
1104                 public void Add (Expression type)
1105                 {
1106                         if (created)
1107                                 throw new InvalidOperationException ();
1108
1109                         args.Add (type);
1110                 }
1111
1112                 public void Add (TypeArguments new_args)
1113                 {
1114                         if (created)
1115                                 throw new InvalidOperationException ();
1116
1117                         args.AddRange (new_args.args);
1118                 }
1119
1120                 /// <summary>
1121                 ///   We're used during the parsing process: the parser can't distinguish
1122                 ///   between type parameters and type arguments.  Because of that, the
1123                 ///   parser creates a `MemberName' with `TypeArguments' for both cases and
1124                 ///   in case of a generic type definition, we call GetDeclarations().
1125                 /// </summary>
1126                 public TypeParameterName[] GetDeclarations ()
1127                 {
1128                         TypeParameterName[] ret = new TypeParameterName [args.Count];
1129                         for (int i = 0; i < args.Count; i++) {
1130                                 TypeParameterName name = args [i] as TypeParameterName;
1131                                 if (name != null) {
1132                                         ret [i] = name;
1133                                         continue;
1134                                 }
1135                                 SimpleName sn = args [i] as SimpleName;
1136                                 if (sn != null) {
1137                                         ret [i] = new TypeParameterName (sn.Name, null, sn.Location);
1138                                         continue;
1139                                 }
1140
1141                                 Report.Error (81, Location, "Type parameter declaration " +
1142                                               "must be an identifier not a type");
1143                                 return null;
1144                         }
1145                         return ret;
1146                 }
1147
1148                 /// <summary>
1149                 ///   We may only be used after Resolve() is called and return the fully
1150                 ///   resolved types.
1151                 /// </summary>
1152                 public Type[] Arguments {
1153                         get {
1154                                 return atypes;
1155                         }
1156                 }
1157
1158                 public bool HasTypeArguments {
1159                         get {
1160                                 return has_type_args;
1161                         }
1162                 }
1163
1164                 public int Count {
1165                         get {
1166                                 if (dimension > 0)
1167                                         return dimension;
1168                                 else
1169                                         return args.Count;
1170                         }
1171                 }
1172
1173                 public bool IsUnbound {
1174                         get {
1175                                 return dimension > 0;
1176                         }
1177                 }
1178
1179                 public override string ToString ()
1180                 {
1181                         StringBuilder s = new StringBuilder ();
1182
1183                         int count = Count;
1184                         for (int i = 0; i < count; i++){
1185                                 //
1186                                 // FIXME: Use TypeManager.CSharpname once we have the type
1187                                 //
1188                                 if (args != null)
1189                                         s.Append (args [i].ToString ());
1190                                 if (i+1 < count)
1191                                         s.Append (",");
1192                         }
1193                         return s.ToString ();
1194                 }
1195
1196                 /// <summary>
1197                 ///   Resolve the type arguments.
1198                 /// </summary>
1199                 public bool Resolve (IResolveContext ec)
1200                 {
1201                         int count = args.Count;
1202                         bool ok = true;
1203
1204                         atypes = new Type [count];
1205
1206                         for (int i = 0; i < count; i++){
1207                                 TypeExpr te = ((Expression) args [i]).ResolveAsTypeTerminal (ec, false);
1208                                 if (te == null) {
1209                                         ok = false;
1210                                         continue;
1211                                 }
1212                                 if (te is TypeParameterExpr)
1213                                         has_type_args = true;
1214
1215                                 if (te.Type.IsPointer) {
1216                                         Report.Error (306, Location, "The type `{0}' may not be used " +
1217                                                       "as a type argument.", TypeManager.CSharpName (te.Type));
1218                                         return false;
1219                                 } else if (te.Type == TypeManager.void_type) {
1220                                         Report.Error (1547, Location,
1221                                                       "Keyword `void' cannot be used in this context");
1222                                         return false;
1223                                 }
1224
1225                                 atypes [i] = te.Type;
1226                         }
1227                         return ok;
1228                 }
1229         }
1230
1231         public class TypeParameterName : SimpleName
1232         {
1233                 Attributes attributes;
1234
1235                 public TypeParameterName (string name, Attributes attrs, Location loc)
1236                         : base (name, loc)
1237                 {
1238                         attributes = attrs;
1239                 }
1240
1241                 public Attributes OptAttributes {
1242                         get {
1243                                 return attributes;
1244                         }
1245                 }
1246         }
1247
1248         /// <summary>
1249         ///   An instantiation of a generic type.
1250         /// </summary>
1251         public class ConstructedType : TypeExpr {
1252                 string full_name;
1253                 FullNamedExpression name;
1254                 TypeArguments args;
1255                 Type[] gen_params, atypes;
1256                 Type gt;
1257
1258                 /// <summary>
1259                 ///   Instantiate the generic type `fname' with the type arguments `args'.
1260                 /// </summary>
1261                 public ConstructedType (FullNamedExpression fname, TypeArguments args, Location l)
1262                 {
1263                         loc = l;
1264                         this.name = fname;
1265                         this.args = args;
1266
1267                         eclass = ExprClass.Type;
1268                         full_name = name + "<" + args.ToString () + ">";
1269                 }
1270
1271                 protected ConstructedType (TypeArguments args, Location l)
1272                 {
1273                         loc = l;
1274                         this.args = args;
1275
1276                         eclass = ExprClass.Type;
1277                 }
1278
1279                 protected ConstructedType (TypeParameter[] type_params, Location l)
1280                 {
1281                         loc = l;
1282
1283                         args = new TypeArguments (l);
1284                         foreach (TypeParameter type_param in type_params)
1285                                 args.Add (new TypeParameterExpr (type_param, l));
1286
1287                         eclass = ExprClass.Type;
1288                 }
1289
1290                 /// <summary>
1291                 ///   This is used to construct the `this' type inside a generic type definition.
1292                 /// </summary>
1293                 public ConstructedType (Type t, TypeParameter[] type_params, Location l)
1294                         : this (type_params, l)
1295                 {
1296                         gt = t.GetGenericTypeDefinition ();
1297
1298                         this.name = new TypeExpression (gt, l);
1299                         full_name = gt.FullName + "<" + args.ToString () + ">";
1300                 }
1301
1302                 /// <summary>
1303                 ///   Instantiate the generic type `t' with the type arguments `args'.
1304                 ///   Use this constructor if you already know the fully resolved
1305                 ///   generic type.
1306                 /// </summary>
1307                 public ConstructedType (Type t, TypeArguments args, Location l)
1308                         : this (args, l)
1309                 {
1310                         gt = t.GetGenericTypeDefinition ();
1311
1312                         this.name = new TypeExpression (gt, l);
1313                         full_name = gt.FullName + "<" + args.ToString () + ">";
1314                 }
1315
1316                 public TypeArguments TypeArguments {
1317                         get { return args; }
1318                 }
1319
1320                 public override string GetSignatureForError ()
1321                 {
1322                         return TypeManager.CSharpName (gt);
1323                 }
1324
1325                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1326                 {
1327                         if (!ResolveConstructedType (ec))
1328                                 return null;
1329
1330                         return this;
1331                 }
1332
1333                 /// <summary>
1334                 ///   Check the constraints; we're called from ResolveAsTypeTerminal()
1335                 ///   after fully resolving the constructed type.
1336                 /// </summary>
1337                 public bool CheckConstraints (IResolveContext ec)
1338                 {
1339                         return ConstraintChecker.CheckConstraints (ec, gt, gen_params, atypes, loc);
1340                 }
1341
1342                 /// <summary>
1343                 ///   Resolve the constructed type, but don't check the constraints.
1344                 /// </summary>
1345                 public bool ResolveConstructedType (IResolveContext ec)
1346                 {
1347                         if (type != null)
1348                                 return true;
1349                         // If we already know the fully resolved generic type.
1350                         if (gt != null)
1351                                 return DoResolveType (ec);
1352
1353                         int num_args;
1354                         Type t = name.Type;
1355
1356                         if (t == null) {
1357                                 Report.Error (246, loc, "Cannot find type `{0}'<...>", Name);
1358                                 return false;
1359                         }
1360
1361                         num_args = TypeManager.GetNumberOfTypeArguments (t);
1362                         if (num_args == 0) {
1363                                 Report.Error (308, loc,
1364                                               "The non-generic type `{0}' cannot " +
1365                                               "be used with type arguments.",
1366                                               TypeManager.CSharpName (t));
1367                                 return false;
1368                         }
1369
1370                         gt = t.GetGenericTypeDefinition ();
1371                         return DoResolveType (ec);
1372                 }
1373
1374                 bool DoResolveType (IResolveContext ec)
1375                 {
1376                         //
1377                         // Resolve the arguments.
1378                         //
1379                         if (args.Resolve (ec) == false)
1380                                 return false;
1381
1382                         gen_params = gt.GetGenericArguments ();
1383                         atypes = args.Arguments;
1384
1385                         if (atypes.Length != gen_params.Length) {
1386                                 Report.Error (305, loc,
1387                                               "Using the generic type `{0}' " +
1388                                               "requires {1} type arguments",
1389                                               TypeManager.CSharpName (gt),
1390                                               gen_params.Length.ToString ());
1391                                 return false;
1392                         }
1393
1394                         //
1395                         // Now bind the parameters.
1396                         //
1397                         type = gt.MakeGenericType (atypes);
1398                         return true;
1399                 }
1400
1401                 public Expression GetSimpleName (EmitContext ec)
1402                 {
1403                         return this;
1404                 }
1405
1406                 public override bool CheckAccessLevel (DeclSpace ds)
1407                 {
1408                         return ds.CheckAccessLevel (gt);
1409                 }
1410
1411                 public override bool AsAccessible (DeclSpace ds, int flags)
1412                 {
1413                         return ds.AsAccessible (gt, flags);
1414                 }
1415
1416                 public override bool IsClass {
1417                         get { return gt.IsClass; }
1418                 }
1419
1420                 public override bool IsValueType {
1421                         get { return gt.IsValueType; }
1422                 }
1423
1424                 public override bool IsInterface {
1425                         get { return gt.IsInterface; }
1426                 }
1427
1428                 public override bool IsSealed {
1429                         get { return gt.IsSealed; }
1430                 }
1431
1432                 public override bool Equals (object obj)
1433                 {
1434                         ConstructedType cobj = obj as ConstructedType;
1435                         if (cobj == null)
1436                                 return false;
1437
1438                         if ((type == null) || (cobj.type == null))
1439                                 return false;
1440
1441                         return type == cobj.type;
1442                 }
1443
1444                 public override int GetHashCode ()
1445                 {
1446                         return base.GetHashCode ();
1447                 }
1448
1449                 public override string Name {
1450                         get {
1451                                 return full_name;
1452                         }
1453                 }
1454
1455
1456                 public override string FullName {
1457                         get {
1458                                 return full_name;
1459                         }
1460                 }
1461         }
1462
1463         public abstract class ConstraintChecker
1464         {
1465                 protected readonly Type[] gen_params;
1466                 protected readonly Type[] atypes;
1467                 protected readonly Location loc;
1468
1469                 protected ConstraintChecker (Type[] gen_params, Type[] atypes, Location loc)
1470                 {
1471                         this.gen_params = gen_params;
1472                         this.atypes = atypes;
1473                         this.loc = loc;
1474                 }
1475
1476                 /// <summary>
1477                 ///   Check the constraints; we're called from ResolveAsTypeTerminal()
1478                 ///   after fully resolving the constructed type.
1479                 /// </summary>
1480                 public bool CheckConstraints (IResolveContext ec)
1481                 {
1482                         for (int i = 0; i < gen_params.Length; i++) {
1483                                 if (!CheckConstraints (ec, i))
1484                                         return false;
1485                         }
1486
1487                         return true;
1488                 }
1489
1490                 protected bool CheckConstraints (IResolveContext ec, int index)
1491                 {
1492                         Type atype = atypes [index];
1493                         Type ptype = gen_params [index];
1494
1495                         if (atype == ptype)
1496                                 return true;
1497
1498                         Expression aexpr = new EmptyExpression (atype);
1499
1500                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (ptype);
1501                         if (gc == null)
1502                                 return true;
1503
1504                         bool is_class, is_struct;
1505                         if (atype.IsGenericParameter) {
1506                                 GenericConstraints agc = TypeManager.GetTypeParameterConstraints (atype);
1507                                 if (agc != null) {
1508                                         if (agc is Constraints)
1509                                                 ((Constraints) agc).Resolve (ec);
1510                                         is_class = agc.HasReferenceTypeConstraint;
1511                                         is_struct = agc.HasValueTypeConstraint;
1512                                 } else {
1513                                         is_class = is_struct = false;
1514                                 }
1515                         } else {
1516 #if MS_COMPATIBLE
1517                                 is_class = false;
1518                                 if (!atype.IsGenericType)
1519 #endif
1520                                 is_class = atype.IsClass || atype.IsInterface;
1521                                 is_struct = atype.IsValueType && !TypeManager.IsNullableType (atype);
1522                         }
1523
1524                         //
1525                         // First, check the `class' and `struct' constraints.
1526                         //
1527                         if (gc.HasReferenceTypeConstraint && !is_class) {
1528                                 Report.Error (452, loc, "The type `{0}' must be " +
1529                                               "a reference type in order to use it " +
1530                                               "as type parameter `{1}' in the " +
1531                                               "generic type or method `{2}'.",
1532                                               TypeManager.CSharpName (atype),
1533                                               TypeManager.CSharpName (ptype),
1534                                               GetSignatureForError ());
1535                                 return false;
1536                         } else if (gc.HasValueTypeConstraint && !is_struct) {
1537                                 Report.Error (453, loc, "The type `{0}' must be a " +
1538                                               "non-nullable value type in order to use it " +
1539                                               "as type parameter `{1}' in the " +
1540                                               "generic type or method `{2}'.",
1541                                               TypeManager.CSharpName (atype),
1542                                               TypeManager.CSharpName (ptype),
1543                                               GetSignatureForError ());
1544                                 return false;
1545                         }
1546
1547                         //
1548                         // The class constraint comes next.
1549                         //
1550                         if (gc.HasClassConstraint) {
1551                                 if (!CheckConstraint (ec, ptype, aexpr, gc.ClassConstraint))
1552                                         return false;
1553                         }
1554
1555                         //
1556                         // Now, check the interface constraints.
1557                         //
1558                         if (gc.InterfaceConstraints != null) {
1559                                 foreach (Type it in gc.InterfaceConstraints) {
1560                                         if (!CheckConstraint (ec, ptype, aexpr, it))
1561                                                 return false;
1562                                 }
1563                         }
1564
1565                         //
1566                         // Finally, check the constructor constraint.
1567                         //
1568
1569                         if (!gc.HasConstructorConstraint)
1570                                 return true;
1571
1572                         if (TypeManager.IsBuiltinType (atype) || atype.IsValueType)
1573                                 return true;
1574
1575                         if (HasDefaultConstructor (ec.DeclContainer.TypeBuilder, atype))
1576                                 return true;
1577
1578                         Report_SymbolRelatedToPreviousError ();
1579                         Report.SymbolRelatedToPreviousError (atype);
1580                         Report.Error (310, loc, "The type `{0}' must have a public " +
1581                                       "parameterless constructor in order to use it " +
1582                                       "as parameter `{1}' in the generic type or " +
1583                                       "method `{2}'",
1584                                       TypeManager.CSharpName (atype),
1585                                       TypeManager.CSharpName (ptype),
1586                                       GetSignatureForError ());
1587                         return false;
1588                 }
1589
1590                 protected bool CheckConstraint (IResolveContext ec, Type ptype, Expression expr,
1591                                                 Type ctype)
1592                 {
1593                         if (TypeManager.HasGenericArguments (ctype)) {
1594                                 Type[] types = TypeManager.GetTypeArguments (ctype);
1595
1596                                 TypeArguments new_args = new TypeArguments (loc);
1597
1598                                 for (int i = 0; i < types.Length; i++) {
1599                                         Type t = types [i];
1600
1601                                         if (t.IsGenericParameter) {
1602                                                 int pos = t.GenericParameterPosition;
1603                                                 t = atypes [pos];
1604                                         }
1605                                         new_args.Add (new TypeExpression (t, loc));
1606                                 }
1607
1608                                 TypeExpr ct = new ConstructedType (ctype, new_args, loc);
1609                                 if (ct.ResolveAsTypeStep (ec, false) == null)
1610                                         return false;
1611                                 ctype = ct.Type;
1612                         } else if (ctype.IsGenericParameter) {
1613                                 int pos = ctype.GenericParameterPosition;
1614                                 ctype = atypes [pos];
1615                         }
1616
1617                         if (Convert.ImplicitStandardConversionExists (expr, ctype))
1618                                 return true;
1619
1620                         Error_TypeMustBeConvertible (expr.Type, ctype, ptype);
1621                         return false;
1622                 }
1623
1624                 bool HasDefaultConstructor (Type containerType, Type atype)
1625                 {
1626                         if (atype.IsAbstract)
1627                                 return false;
1628
1629                 again:
1630                         atype = TypeManager.DropGenericTypeArguments (atype);
1631                         if (atype is TypeBuilder) {
1632                                 TypeContainer tc = TypeManager.LookupTypeContainer (atype);
1633                                 if (tc.InstanceConstructors == null) {
1634                                         atype = atype.BaseType;
1635                                         goto again;
1636                                 }
1637
1638                                 foreach (Constructor c in tc.InstanceConstructors) {
1639                                         if ((c.ModFlags & Modifiers.PUBLIC) == 0)
1640                                                 continue;
1641                                         if ((c.Parameters.FixedParameters != null) &&
1642                                             (c.Parameters.FixedParameters.Length != 0))
1643                                                 continue;
1644                                         if (c.Parameters.HasArglist || c.Parameters.HasParams)
1645                                                 continue;
1646
1647                                         return true;
1648                                 }
1649                         }
1650
1651                         TypeParameter tparam = TypeManager.LookupTypeParameter (atype);
1652                         if (tparam != null)
1653                                 return tparam.HasConstructorConstraint;
1654
1655                         MemberList list = TypeManager.FindMembers (
1656                                 atype, MemberTypes.Constructor,
1657                                 BindingFlags.Public | BindingFlags.Instance |
1658                                 BindingFlags.DeclaredOnly, null, null);
1659
1660                         if (atype.IsAbstract || (list == null))
1661                                 return false;
1662
1663                         foreach (MethodBase mb in list) {
1664                                 ParameterData pd = TypeManager.GetParameterData (mb);
1665                                 if ((pd.Count == 0) && mb.IsPublic && !mb.IsStatic)
1666                                         return true;
1667                         }
1668
1669                         return false;
1670                 }
1671
1672                 protected abstract string GetSignatureForError ();
1673                 protected abstract void Report_SymbolRelatedToPreviousError ();
1674
1675                 void Error_TypeMustBeConvertible (Type atype, Type gc, Type ptype)
1676                 {
1677                         Report_SymbolRelatedToPreviousError ();
1678                         Report.SymbolRelatedToPreviousError (atype);
1679                         Report.Error (309, loc,
1680                                       "The type `{0}' must be convertible to `{1}' in order to " +
1681                                       "use it as parameter `{2}' in the generic type or method `{3}'",
1682                                       TypeManager.CSharpName (atype), TypeManager.CSharpName (gc),
1683                                       TypeManager.CSharpName (ptype), GetSignatureForError ());
1684                 }
1685
1686                 public static bool CheckConstraints (EmitContext ec, MethodBase definition,
1687                                                      MethodBase instantiated, Location loc)
1688                 {
1689                         MethodConstraintChecker checker = new MethodConstraintChecker (
1690                                 definition, definition.GetGenericArguments (),
1691                                 instantiated.GetGenericArguments (), loc);
1692
1693                         return checker.CheckConstraints (ec);
1694                 }
1695
1696                 public static bool CheckConstraints (IResolveContext ec, Type gt, Type[] gen_params,
1697                                                      Type[] atypes, Location loc)
1698                 {
1699                         TypeConstraintChecker checker = new TypeConstraintChecker (
1700                                 gt, gen_params, atypes, loc);
1701
1702                         return checker.CheckConstraints (ec);
1703                 }
1704
1705                 protected class MethodConstraintChecker : ConstraintChecker
1706                 {
1707                         MethodBase definition;
1708
1709                         public MethodConstraintChecker (MethodBase definition, Type[] gen_params,
1710                                                         Type[] atypes, Location loc)
1711                                 : base (gen_params, atypes, loc)
1712                         {
1713                                 this.definition = definition;
1714                         }
1715
1716                         protected override string GetSignatureForError ()
1717                         {
1718                                 return TypeManager.CSharpSignature (definition);
1719                         }
1720
1721                         protected override void Report_SymbolRelatedToPreviousError ()
1722                         {
1723                                 Report.SymbolRelatedToPreviousError (definition);
1724                         }
1725                 }
1726
1727                 protected class TypeConstraintChecker : ConstraintChecker
1728                 {
1729                         Type gt;
1730
1731                         public TypeConstraintChecker (Type gt, Type[] gen_params, Type[] atypes,
1732                                                       Location loc)
1733                                 : base (gen_params, atypes, loc)
1734                         {
1735                                 this.gt = gt;
1736                         }
1737
1738                         protected override string GetSignatureForError ()
1739                         {
1740                                 return TypeManager.CSharpName (gt);
1741                         }
1742
1743                         protected override void Report_SymbolRelatedToPreviousError ()
1744                         {
1745                                 Report.SymbolRelatedToPreviousError (gt);
1746                         }
1747                 }
1748         }
1749
1750         /// <summary>
1751         ///   A generic method definition.
1752         /// </summary>
1753         public class GenericMethod : DeclSpace
1754         {
1755                 Expression return_type;
1756                 Parameters parameters;
1757
1758                 public GenericMethod (NamespaceEntry ns, DeclSpace parent, MemberName name,
1759                                       Expression return_type, Parameters parameters)
1760                         : base (ns, parent, name, null)
1761                 {
1762                         this.return_type = return_type;
1763                         this.parameters = parameters;
1764                 }
1765
1766                 public override TypeBuilder DefineType ()
1767                 {
1768                         throw new Exception ();
1769                 }
1770
1771                 public override bool Define ()
1772                 {
1773                         for (int i = 0; i < TypeParameters.Length; i++)
1774                                 if (!TypeParameters [i].Resolve (this))
1775                                         return false;
1776
1777                         return true;
1778                 }
1779
1780                 /// <summary>
1781                 ///   Define and resolve the type parameters.
1782                 ///   We're called from Method.Define().
1783                 /// </summary>
1784                 public bool Define (MethodBuilder mb)
1785                 {
1786                         GenericTypeParameterBuilder[] gen_params;
1787                         TypeParameterName[] names = MemberName.TypeArguments.GetDeclarations ();
1788                         string[] snames = new string [names.Length];
1789                         for (int i = 0; i < names.Length; i++)
1790                                 snames [i] = names [i].Name;
1791                         gen_params = mb.DefineGenericParameters (snames);
1792                         for (int i = 0; i < TypeParameters.Length; i++)
1793                                 TypeParameters [i].Define (gen_params [i]);
1794
1795                         if (!Define ())
1796                                 return false;
1797
1798                         for (int i = 0; i < TypeParameters.Length; i++) {
1799                                 if (!TypeParameters [i].ResolveType (this))
1800                                         return false;
1801                         }
1802
1803                         return true;
1804                 }
1805
1806                 /// <summary>
1807                 ///   We're called from MethodData.Define() after creating the MethodBuilder.
1808                 /// </summary>
1809                 public bool DefineType (EmitContext ec, MethodBuilder mb,
1810                                         MethodInfo implementing, bool is_override)
1811                 {
1812                         for (int i = 0; i < TypeParameters.Length; i++)
1813                                 if (!TypeParameters [i].DefineType (
1814                                             ec, mb, implementing, is_override))
1815                                         return false;
1816
1817                         bool ok = true;
1818                         foreach (Parameter p in parameters.FixedParameters){
1819                                 if (!p.Resolve (ec))
1820                                         ok = false;
1821                         }
1822                         if ((return_type != null) && (return_type.ResolveAsTypeTerminal (ec, false) == null))
1823                                 ok = false;
1824
1825                         return ok;
1826                 }
1827
1828                 public void EmitAttributes ()
1829                 {
1830                         for (int i = 0; i < TypeParameters.Length; i++)
1831                                 TypeParameters [i].EmitAttributes ();
1832
1833                         if (OptAttributes != null)
1834                                 OptAttributes.Emit ();
1835                 }
1836
1837                 public override bool DefineMembers ()
1838                 {
1839                         return true;
1840                 }
1841
1842                 public override MemberList FindMembers (MemberTypes mt, BindingFlags bf,
1843                                                         MemberFilter filter, object criteria)
1844                 {
1845                         throw new Exception ();
1846                 }
1847
1848                 public override MemberCache MemberCache {
1849                         get {
1850                                 return null;
1851                         }
1852                 }
1853
1854                 public override void ApplyAttributeBuilder (Attribute a, CustomAttributeBuilder cb)
1855                 {
1856                         base.ApplyAttributeBuilder (a, cb);
1857                 }
1858
1859                 public override AttributeTargets AttributeTargets {
1860                         get {
1861                                 return AttributeTargets.Method | AttributeTargets.ReturnValue;
1862                         }
1863                 }
1864
1865                 public override string DocCommentHeader {
1866                         get { return "M:"; }
1867                 }
1868         }
1869
1870         public class DefaultValueExpression : Expression
1871         {
1872                 Expression expr;
1873
1874                 public DefaultValueExpression (Expression expr, Location loc)
1875                 {
1876                         this.expr = expr;
1877                         this.loc = loc;
1878                 }
1879
1880                 public override Expression DoResolve (EmitContext ec)
1881                 {
1882                         TypeExpr texpr = expr.ResolveAsTypeTerminal (ec, false);
1883                         if (texpr == null)
1884                                 return null;
1885
1886                         type = texpr.Type;
1887
1888                         eclass = ExprClass.Variable;
1889                         return this;
1890                 }
1891
1892                 public override void Emit (EmitContext ec)
1893                 {
1894                         if (type.IsGenericParameter || TypeManager.IsValueType (type)) {
1895                                 LocalTemporary temp_storage = new LocalTemporary (type);
1896
1897                                 temp_storage.AddressOf (ec, AddressOp.LoadStore);
1898                                 ec.ig.Emit (OpCodes.Initobj, type);
1899                                 temp_storage.Emit (ec);
1900                         } else
1901                                 ec.ig.Emit (OpCodes.Ldnull);
1902                 }
1903         }
1904
1905         public class NullableType : TypeExpr
1906         {
1907                 Expression underlying;
1908
1909                 public NullableType (Expression underlying, Location l)
1910                 {
1911                         this.underlying = underlying;
1912                         loc = l;
1913
1914                         eclass = ExprClass.Type;
1915                 }
1916
1917                 public NullableType (Type type, Location loc)
1918                         : this (new TypeExpression (type, loc), loc)
1919                 { }
1920
1921                 public override string Name {
1922                         get { return underlying.ToString () + "?"; }
1923                 }
1924
1925                 public override string FullName {
1926                         get { return underlying.ToString () + "?"; }
1927                 }
1928
1929                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1930                 {
1931                         TypeArguments args = new TypeArguments (loc);
1932                         args.Add (underlying);
1933
1934                         ConstructedType ctype = new ConstructedType (TypeManager.generic_nullable_type, args, loc);
1935                         return ctype.ResolveAsTypeTerminal (ec, false);
1936                 }
1937         }
1938
1939         public partial class TypeManager
1940         {
1941                 //
1942                 // A list of core types that the compiler requires or uses
1943                 //
1944                 static public Type activator_type;
1945                 static public Type generic_ienumerator_type;
1946                 static public Type generic_ienumerable_type;
1947                 static public Type generic_nullable_type;
1948
1949                 // <remarks>
1950                 //   Tracks the generic parameters.
1951                 // </remarks>
1952                 static PtrHashtable builder_to_type_param;
1953
1954                 //
1955                 // These methods are called by code generated by the compiler
1956                 //
1957                 static public MethodInfo activator_create_instance;
1958
1959                 static void InitGenerics ()
1960                 {
1961                         builder_to_type_param = new PtrHashtable ();
1962                 }
1963
1964                 static void CleanUpGenerics ()
1965                 {
1966                         builder_to_type_param = null;
1967                 }
1968
1969                 static void InitGenericCoreTypes ()
1970                 {
1971                         activator_type = CoreLookupType ("System", "Activator");
1972
1973                         generic_ienumerator_type = CoreLookupType (
1974                                 "System.Collections.Generic", "IEnumerator", 1);
1975                         generic_ienumerable_type = CoreLookupType (
1976                                 "System.Collections.Generic", "IEnumerable", 1);
1977                         generic_nullable_type = CoreLookupType (
1978                                 "System", "Nullable", 1);
1979                 }
1980
1981                 static void InitGenericCodeHelpers ()
1982                 {
1983                         // Activator
1984                         Type [] type_arg = { type_type };
1985                         activator_create_instance = GetMethod (
1986                                 activator_type, "CreateInstance", type_arg);
1987                 }
1988
1989                 static Type CoreLookupType (string ns, string name, int arity)
1990                 {
1991                         return CoreLookupType (ns, MemberName.MakeName (name, arity));
1992                 }
1993
1994                 public static void AddTypeParameter (Type t, TypeParameter tparam)
1995                 {
1996                         if (!builder_to_type_param.Contains (t))
1997                                 builder_to_type_param.Add (t, tparam);
1998                 }
1999
2000                 public static TypeContainer LookupGenericTypeContainer (Type t)
2001                 {
2002                         t = DropGenericTypeArguments (t);
2003                         return LookupTypeContainer (t);
2004                 }
2005
2006                 public static TypeParameter LookupTypeParameter (Type t)
2007                 {
2008                         return (TypeParameter) builder_to_type_param [t];
2009                 }
2010
2011                 public static GenericConstraints GetTypeParameterConstraints (Type t)
2012                 {
2013                         if (!t.IsGenericParameter)
2014                                 throw new InvalidOperationException ();
2015
2016                         TypeParameter tparam = LookupTypeParameter (t);
2017                         if (tparam != null)
2018                                 return tparam.GenericConstraints;
2019
2020                         return ReflectionConstraints.GetConstraints (t);
2021                 }
2022
2023                 public static bool HasGenericArguments (Type t)
2024                 {
2025                         return GetNumberOfTypeArguments (t) > 0;
2026                 }
2027
2028                 public static int GetNumberOfTypeArguments (Type t)
2029                 {
2030                         if (t.IsGenericParameter)
2031                                 return 0;
2032                         DeclSpace tc = LookupDeclSpace (t);
2033                         if (tc != null)
2034                                 return tc.IsGeneric ? tc.CountTypeParameters : 0;
2035                         else
2036                                 return t.IsGenericType ? t.GetGenericArguments ().Length : 0;
2037                 }
2038
2039                 public static Type[] GetTypeArguments (Type t)
2040                 {
2041                         DeclSpace tc = LookupDeclSpace (t);
2042                         if (tc != null) {
2043                                 if (!tc.IsGeneric)
2044                                         return Type.EmptyTypes;
2045
2046                                 TypeParameter[] tparam = tc.TypeParameters;
2047                                 Type[] ret = new Type [tparam.Length];
2048                                 for (int i = 0; i < tparam.Length; i++) {
2049                                         ret [i] = tparam [i].Type;
2050                                         if (ret [i] == null)
2051                                                 throw new InternalErrorException ();
2052                                 }
2053
2054                                 return ret;
2055                         } else
2056                                 return t.GetGenericArguments ();
2057                 }
2058
2059                 public static Type DropGenericTypeArguments (Type t)
2060                 {
2061                         if (!t.IsGenericType)
2062                                 return t;
2063                         // Micro-optimization: a generic typebuilder is always a generic type definition
2064                         if (t is TypeBuilder)
2065                                 return t;
2066                         return t.GetGenericTypeDefinition ();
2067                 }
2068
2069                 public static MethodBase DropGenericMethodArguments (MethodBase m)
2070                 {
2071                         if (m.IsGenericMethodDefinition)
2072                                 return m;
2073                         if (m.IsGenericMethod)
2074                                 return ((MethodInfo) m).GetGenericMethodDefinition ();
2075                         if (!m.DeclaringType.IsGenericType)
2076                                 return m;
2077
2078                         Type t = m.DeclaringType.GetGenericTypeDefinition ();
2079                         BindingFlags bf = BindingFlags.Public | BindingFlags.NonPublic |
2080                                 BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly;
2081
2082                         if (m is ConstructorInfo) {
2083                                 foreach (ConstructorInfo c in t.GetConstructors (bf))
2084                                         if (c.MetadataToken == m.MetadataToken)
2085                                                 return c;
2086                         } else {
2087                                 foreach (MethodBase mb in t.GetMethods (bf))
2088                                         if (mb.MetadataToken == m.MetadataToken)
2089                                                 return mb;
2090                         }
2091
2092                         return m;
2093                 }
2094
2095                 public static FieldInfo GetGenericFieldDefinition (FieldInfo fi)
2096                 {
2097                         if (fi.DeclaringType.IsGenericTypeDefinition ||
2098                             !fi.DeclaringType.IsGenericType)
2099                                 return fi;
2100
2101                         Type t = fi.DeclaringType.GetGenericTypeDefinition ();
2102                         BindingFlags bf = BindingFlags.Public | BindingFlags.NonPublic |
2103                                 BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly;
2104
2105                         foreach (FieldInfo f in t.GetFields (bf))
2106                                 if (f.MetadataToken == fi.MetadataToken)
2107                                         return f;
2108
2109                         return fi;
2110                 }
2111
2112                 //
2113                 // Whether `array' is an array of T and `enumerator' is `IEnumerable<T>'.
2114                 // For instance "string[]" -> "IEnumerable<string>".
2115                 //
2116                 public static bool IsIEnumerable (Type array, Type enumerator)
2117                 {
2118                         if (!array.IsArray || !enumerator.IsGenericType)
2119                                 return false;
2120
2121                         if (enumerator.GetGenericTypeDefinition () != generic_ienumerable_type)
2122                                 return false;
2123
2124                         Type[] args = GetTypeArguments (enumerator);
2125                         return args [0] == GetElementType (array);
2126                 }
2127
2128                 public static bool IsEqual (Type a, Type b)
2129                 {
2130                         if (a.Equals (b))
2131                                 return true;
2132
2133                         if (a.IsGenericParameter && b.IsGenericParameter) {
2134                                 if (a.DeclaringMethod != b.DeclaringMethod &&
2135                                     (a.DeclaringMethod == null || b.DeclaringMethod == null))
2136                                         return false;
2137                                 return a.GenericParameterPosition == b.GenericParameterPosition;
2138                         }
2139
2140                         if (a.IsArray && b.IsArray) {
2141                                 if (a.GetArrayRank () != b.GetArrayRank ())
2142                                         return false;
2143                                 return IsEqual (a.GetElementType (), b.GetElementType ());
2144                         }
2145
2146                         if (a.IsByRef && b.IsByRef)
2147                                 return IsEqual (a.GetElementType (), b.GetElementType ());
2148
2149                         if (a.IsGenericType && b.IsGenericType) {
2150                                 if (a.GetGenericTypeDefinition () != b.GetGenericTypeDefinition ())
2151                                         return false;
2152
2153                                 Type[] aargs = a.GetGenericArguments ();
2154                                 Type[] bargs = b.GetGenericArguments ();
2155
2156                                 if (aargs.Length != bargs.Length)
2157                                         return false;
2158
2159                                 for (int i = 0; i < aargs.Length; i++) {
2160                                         if (!IsEqual (aargs [i], bargs [i]))
2161                                                 return false;
2162                                 }
2163
2164                                 return true;
2165                         }
2166
2167                         //
2168                         // This is to build with the broken circular dependencies between
2169                         // System and System.Configuration in the 2.x profile where we
2170                         // end up with a situation where:
2171                         //
2172                         // System on the second build is referencing the System.Configuration
2173                         // that has references to the first System build.
2174                         //
2175                         // Point in case: NameValueCollection built on the first pass, vs
2176                         // NameValueCollection build on the second one.  The problem is that
2177                         // we need to override some methods sometimes, or we need to
2178                         //
2179                         if (RootContext.BrokenCircularDeps){
2180                                 if (a.Name == b.Name && a.Namespace == b.Namespace){
2181                                         Console.WriteLine ("GonziMatch: {0}.{1}", a.Namespace, a.Name);
2182                                         return true;
2183                                 }
2184                         }
2185                         return false;
2186                 }
2187
2188                 /// <summary>
2189                 ///   Check whether `a' and `b' may become equal generic types.
2190                 ///   The algorithm to do that is a little bit complicated.
2191                 /// </summary>
2192                 public static bool MayBecomeEqualGenericTypes (Type a, Type b, Type[] class_infered,
2193                                                                Type[] method_infered)
2194                 {
2195                         if (a.IsGenericParameter) {
2196                                 //
2197                                 // If a is an array of a's type, they may never
2198                                 // become equal.
2199                                 //
2200                                 while (b.IsArray) {
2201                                         b = b.GetElementType ();
2202                                         if (a.Equals (b))
2203                                                 return false;
2204                                 }
2205
2206                                 //
2207                                 // If b is a generic parameter or an actual type,
2208                                 // they may become equal:
2209                                 //
2210                                 //    class X<T,U> : I<T>, I<U>
2211                                 //    class X<T> : I<T>, I<float>
2212                                 //
2213                                 if (b.IsGenericParameter || !b.IsGenericType) {
2214                                         int pos = a.GenericParameterPosition;
2215                                         Type[] args = a.DeclaringMethod != null ? method_infered : class_infered;
2216                                         if (args [pos] == null) {
2217                                                 args [pos] = b;
2218                                                 return true;
2219                                         }
2220
2221                                         return args [pos] == a;
2222                                 }
2223
2224                                 //
2225                                 // We're now comparing a type parameter with a
2226                                 // generic instance.  They may become equal unless
2227                                 // the type parameter appears anywhere in the
2228                                 // generic instance:
2229                                 //
2230                                 //    class X<T,U> : I<T>, I<X<U>>
2231                                 //        -> error because you could instanciate it as
2232                                 //           X<X<int>,int>
2233                                 //
2234                                 //    class X<T> : I<T>, I<X<T>> -> ok
2235                                 //
2236
2237                                 Type[] bargs = GetTypeArguments (b);
2238                                 for (int i = 0; i < bargs.Length; i++) {
2239                                         if (a.Equals (bargs [i]))
2240                                                 return false;
2241                                 }
2242
2243                                 return true;
2244                         }
2245
2246                         if (b.IsGenericParameter)
2247                                 return MayBecomeEqualGenericTypes (b, a, class_infered, method_infered);
2248
2249                         //
2250                         // At this point, neither a nor b are a type parameter.
2251                         //
2252                         // If one of them is a generic instance, let
2253                         // MayBecomeEqualGenericInstances() compare them (if the
2254                         // other one is not a generic instance, they can never
2255                         // become equal).
2256                         //
2257
2258                         if (a.IsGenericType || b.IsGenericType)
2259                                 return MayBecomeEqualGenericInstances (a, b, class_infered, method_infered);
2260
2261                         //
2262                         // If both of them are arrays.
2263                         //
2264
2265                         if (a.IsArray && b.IsArray) {
2266                                 if (a.GetArrayRank () != b.GetArrayRank ())
2267                                         return false;
2268
2269                                 a = a.GetElementType ();
2270                                 b = b.GetElementType ();
2271
2272                                 return MayBecomeEqualGenericTypes (a, b, class_infered, method_infered);
2273                         }
2274
2275                         //
2276                         // Ok, two ordinary types.
2277                         //
2278
2279                         return a.Equals (b);
2280                 }
2281
2282                 //
2283                 // Checks whether two generic instances may become equal for some
2284                 // particular instantiation (26.3.1).
2285                 //
2286                 public static bool MayBecomeEqualGenericInstances (Type a, Type b,
2287                                                                    Type[] class_infered,
2288                                                                    Type[] method_infered)
2289                 {
2290                         if (!a.IsGenericType || !b.IsGenericType)
2291                                 return false;
2292                         if (a.GetGenericTypeDefinition () != b.GetGenericTypeDefinition ())
2293                                 return false;
2294
2295                         return MayBecomeEqualGenericInstances (
2296                                 GetTypeArguments (a), GetTypeArguments (b), class_infered, method_infered);
2297                 }
2298
2299                 public static bool MayBecomeEqualGenericInstances (Type[] aargs, Type[] bargs,
2300                                                                    Type[] class_infered,
2301                                                                    Type[] method_infered)
2302                 {
2303                         if (aargs.Length != bargs.Length)
2304                                 return false;
2305
2306                         for (int i = 0; i < aargs.Length; i++) {
2307                                 if (!MayBecomeEqualGenericTypes (aargs [i], bargs [i], class_infered, method_infered))
2308                                         return false;
2309                         }
2310
2311                         return true;
2312                 }
2313
2314                 /// <summary>
2315                 ///   Check whether `type' and `parent' are both instantiations of the same
2316                 ///   generic type.  Note that we do not check the type parameters here.
2317                 /// </summary>
2318                 public static bool IsInstantiationOfSameGenericType (Type type, Type parent)
2319                 {
2320                         int tcount = GetNumberOfTypeArguments (type);
2321                         int pcount = GetNumberOfTypeArguments (parent);
2322
2323                         if (tcount != pcount)
2324                                 return false;
2325
2326                         type = DropGenericTypeArguments (type);
2327                         parent = DropGenericTypeArguments (parent);
2328
2329                         return type.Equals (parent);
2330                 }
2331
2332                 /// <summary>
2333                 ///   Whether `mb' is a generic method definition.
2334                 /// </summary>
2335                 public static bool IsGenericMethodDefinition (MethodBase mb)
2336                 {
2337                         if (mb.DeclaringType is TypeBuilder) {
2338                                 IMethodData method = (IMethodData) builder_to_method [mb];
2339                                 if (method == null)
2340                                         return false;
2341
2342                                 return method.GenericMethod != null;
2343                         }
2344
2345                         return mb.IsGenericMethodDefinition;
2346                 }
2347
2348                 /// <summary>
2349                 ///   Whether `mb' is a generic method definition.
2350                 /// </summary>
2351                 public static bool IsGenericMethod (MethodBase mb)
2352                 {
2353                         if (mb.DeclaringType is TypeBuilder) {
2354                                 IMethodData method = (IMethodData) builder_to_method [mb];
2355                                 if (method == null)
2356                                         return false;
2357
2358                                 return method.GenericMethod != null;
2359                         }
2360
2361                         return mb.IsGenericMethod;
2362                 }
2363
2364                 //
2365                 // Type inference.
2366                 //
2367
2368                 static bool InferType (Type pt, Type at, Type[] infered)
2369                 {
2370                         if (pt.IsGenericParameter) {
2371                                 if (pt.DeclaringMethod == null)
2372                                         return pt == at;
2373
2374                                 int pos = pt.GenericParameterPosition;
2375
2376                                 if (infered [pos] == null) {
2377                                         infered [pos] = at;
2378                                         return true;
2379                                 }
2380
2381                                 if (infered [pos] != at)
2382                                         return false;
2383
2384                                 return true;
2385                         }
2386
2387                         if (!pt.ContainsGenericParameters) {
2388                                 if (at.ContainsGenericParameters)
2389                                         return InferType (at, pt, infered);
2390                                 else
2391                                         return true;
2392                         }
2393
2394                         if (at.IsArray) {
2395                                 if (pt.IsArray) {
2396                                         if (at.GetArrayRank () != pt.GetArrayRank ())
2397                                                 return false;
2398
2399                                         return InferType (pt.GetElementType (), at.GetElementType (), infered);
2400                                 }
2401
2402                                 if (!pt.IsGenericType ||
2403                                     (pt.GetGenericTypeDefinition () != generic_ienumerable_type))
2404                                     return false;
2405
2406                                 Type[] args = GetTypeArguments (pt);
2407                                 return InferType (args [0], at.GetElementType (), infered);
2408                         }
2409
2410                         if (pt.IsArray) {
2411                                 if (!at.IsArray ||
2412                                     (pt.GetArrayRank () != at.GetArrayRank ()))
2413                                         return false;
2414
2415                                 return InferType (pt.GetElementType (), at.GetElementType (), infered);
2416                         }
2417
2418                         if (pt.IsByRef && at.IsByRef)
2419                                 return InferType (pt.GetElementType (), at.GetElementType (), infered);
2420                         ArrayList list = new ArrayList ();
2421                         if (at.IsGenericType)
2422                                 list.Add (at);
2423                         for (Type bt = at.BaseType; bt != null; bt = bt.BaseType)
2424                                 list.Add (bt);
2425
2426                         list.AddRange (TypeManager.GetInterfaces (at));
2427
2428                         bool found_one = false;
2429
2430                         foreach (Type type in list) {
2431                                 if (!type.IsGenericType)
2432                                         continue;
2433
2434                                 Type[] infered_types = new Type [infered.Length];
2435
2436                                 if (!InferGenericInstance (pt, type, infered_types))
2437                                         continue;
2438
2439                                 for (int i = 0; i < infered_types.Length; i++) {
2440                                         if (infered [i] == null) {
2441                                                 infered [i] = infered_types [i];
2442                                                 continue;
2443                                         }
2444
2445                                         if (infered [i] != infered_types [i])
2446                                                 return false;
2447                                 }
2448
2449                                 found_one = true;
2450                         }
2451
2452                         return found_one;
2453                 }
2454
2455                 static bool InferGenericInstance (Type pt, Type at, Type[] infered_types)
2456                 {
2457                         Type[] at_args = at.GetGenericArguments ();
2458                         Type[] pt_args = pt.GetGenericArguments ();
2459
2460                         if (at_args.Length != pt_args.Length)
2461                                 return false;
2462
2463                         for (int i = 0; i < at_args.Length; i++) {
2464                                 if (!InferType (pt_args [i], at_args [i], infered_types))
2465                                         return false;
2466                         }
2467
2468                         for (int i = 0; i < infered_types.Length; i++) {
2469                                 if (infered_types [i] == null)
2470                                         return false;
2471                         }
2472
2473                         return true;
2474                 }
2475
2476                 /// <summary>
2477                 ///   Type inference.  Try to infer the type arguments from the params method
2478                 ///   `method', which is invoked with the arguments `arguments'.  This is used
2479                 ///   when resolving an Invocation or a DelegateInvocation and the user
2480                 ///   did not explicitly specify type arguments.
2481                 /// </summary>
2482                 public static bool InferParamsTypeArguments (EmitContext ec, ArrayList arguments,
2483                                                              ref MethodBase method)
2484                 {
2485                         if (!TypeManager.IsGenericMethod (method))
2486                                 return true;
2487
2488                         // if there are no arguments, there's no way to infer the type-arguments
2489                         if (arguments == null || arguments.Count == 0)
2490                                 return false;
2491
2492                         ParameterData pd = TypeManager.GetParameterData (method);
2493                         int pd_count = pd.Count;
2494                         int arg_count = arguments.Count;
2495
2496                         if (pd_count == 0)
2497                                 return false;
2498
2499                         if (pd.ParameterModifier (pd_count - 1) != Parameter.Modifier.PARAMS)
2500                                 return false;
2501
2502                         if (pd_count - 1 > arg_count)
2503                                 return false;
2504
2505                         Type[] method_args = method.GetGenericArguments ();
2506                         Type[] infered_types = new Type [method_args.Length];
2507
2508                         //
2509                         // If we have come this far, the case which
2510                         // remains is when the number of parameters is
2511                         // less than or equal to the argument count.
2512                         //
2513                         for (int i = 0; i < pd_count - 1; ++i) {
2514                                 Argument a = (Argument) arguments [i];
2515
2516                                 if ((a.Expr is NullLiteral) || (a.Expr is MethodGroupExpr))
2517                                         continue;
2518
2519                                 Type pt = pd.ParameterType (i);
2520                                 Type at = a.Type;
2521
2522                                 if (!InferType (pt, at, infered_types))
2523                                         return false;
2524                         }
2525
2526                         Type element_type = TypeManager.GetElementType (pd.ParameterType (pd_count - 1));
2527
2528                         for (int i = pd_count - 1; i < arg_count; i++) {
2529                                 Argument a = (Argument) arguments [i];
2530
2531                                 if ((a.Expr is NullLiteral) || (a.Expr is MethodGroupExpr))
2532                                         continue;
2533
2534                                 if (!InferType (element_type, a.Type, infered_types))
2535                                         return false;
2536                         }
2537
2538                         for (int i = 0; i < infered_types.Length; i++)
2539                                 if (infered_types [i] == null)
2540                                         return false;
2541
2542                         method = ((MethodInfo)method).MakeGenericMethod (infered_types);
2543                         return true;
2544                 }
2545
2546                 static bool InferTypeArguments (Type[] param_types, Type[] arg_types,
2547                                                 Type[] infered_types)
2548                 {
2549                         if (infered_types == null)
2550                                 return false;
2551
2552                         for (int i = 0; i < arg_types.Length; i++) {
2553                                 if (arg_types [i] == null)
2554                                         continue;
2555
2556                                 if (!InferType (param_types [i], arg_types [i], infered_types))
2557                                         return false;
2558                         }
2559
2560                         for (int i = 0; i < infered_types.Length; i++)
2561                                 if (infered_types [i] == null)
2562                                         return false;
2563
2564                         return true;
2565                 }
2566
2567                 /// <summary>
2568                 ///   Type inference.  Try to infer the type arguments from `method',
2569                 ///   which is invoked with the arguments `arguments'.  This is used
2570                 ///   when resolving an Invocation or a DelegateInvocation and the user
2571                 ///   did not explicitly specify type arguments.
2572                 /// </summary>
2573                 public static bool InferTypeArguments (ArrayList arguments,
2574                                                        ref MethodBase method)
2575                 {
2576                         if (!TypeManager.IsGenericMethod (method))
2577                                 return true;
2578
2579                         int arg_count;
2580                         if (arguments != null)
2581                                 arg_count = arguments.Count;
2582                         else
2583                                 arg_count = 0;
2584
2585                         ParameterData pd = TypeManager.GetParameterData (method);
2586                         if (arg_count != pd.Count)
2587                                 return false;
2588
2589                         Type[] method_args = method.GetGenericArguments ();
2590
2591                         bool is_open = false;
2592                         for (int i = 0; i < method_args.Length; i++) {
2593                                 if (method_args [i].IsGenericParameter) {
2594                                         is_open = true;
2595                                         break;
2596                                 }
2597                         }
2598
2599                         // If none of the method parameters mention a generic parameter, we can't infer the generic parameters
2600                         if (!is_open)
2601                                 return !TypeManager.IsGenericMethodDefinition (method);
2602
2603                         Type[] infered_types = new Type [method_args.Length];
2604
2605                         Type[] param_types = new Type [pd.Count];
2606                         Type[] arg_types = new Type [pd.Count];
2607
2608                         for (int i = 0; i < arg_count; i++) {
2609                                 param_types [i] = pd.ParameterType (i);
2610
2611                                 Argument a = (Argument) arguments [i];
2612                                 if ((a.Expr is NullLiteral) || (a.Expr is MethodGroupExpr) ||
2613                                     (a.Expr is AnonymousMethod))
2614                                         continue;
2615
2616                                 arg_types [i] = a.Type;
2617                         }
2618
2619                         if (!InferTypeArguments (param_types, arg_types, infered_types))
2620                                 return false;
2621
2622                         method = ((MethodInfo)method).MakeGenericMethod (infered_types);
2623                         return true;
2624                 }
2625
2626                 /// <summary>
2627                 ///   Type inference.
2628                 /// </summary>
2629                 public static bool InferTypeArguments (ParameterData apd,
2630                                                        ref MethodBase method)
2631                 {
2632                         if (!TypeManager.IsGenericMethod (method))
2633                                 return true;
2634
2635                         ParameterData pd = TypeManager.GetParameterData (method);
2636                         if (apd.Count != pd.Count)
2637                                 return false;
2638
2639                         Type[] method_args = method.GetGenericArguments ();
2640                         Type[] infered_types = new Type [method_args.Length];
2641
2642                         Type[] param_types = new Type [pd.Count];
2643                         Type[] arg_types = new Type [pd.Count];
2644
2645                         for (int i = 0; i < apd.Count; i++) {
2646                                 param_types [i] = pd.ParameterType (i);
2647                                 arg_types [i] = apd.ParameterType (i);
2648                         }
2649
2650                         if (!InferTypeArguments (param_types, arg_types, infered_types))
2651                                 return false;
2652
2653                         method = ((MethodInfo)method).MakeGenericMethod (infered_types);
2654                         return true;
2655                 }
2656
2657                 public static bool IsNullableType (Type t)
2658                 {
2659                         return generic_nullable_type == DropGenericTypeArguments (t);
2660                 }
2661
2662                 public static bool IsNullableTypeOf (Type t, Type nullable)
2663                 {
2664                         if (!IsNullableType (t))
2665                                 return false;
2666
2667                         return GetTypeArguments (t) [0] == nullable;
2668                 }
2669
2670                 public static bool IsNullableValueType (Type t)
2671                 {
2672                         if (!IsNullableType (t))
2673                                 return false;
2674
2675                         return GetTypeArguments (t) [0].IsValueType;
2676                 }
2677         }
2678
2679         public abstract class Nullable
2680         {
2681                 public sealed class NullableInfo
2682                 {
2683                         public readonly Type Type;
2684                         public readonly Type UnderlyingType;
2685                         public readonly MethodInfo HasValue;
2686                         public readonly MethodInfo Value;
2687                         public readonly ConstructorInfo Constructor;
2688
2689                         public NullableInfo (Type type)
2690                         {
2691                                 Type = type;
2692                                 UnderlyingType = TypeManager.GetTypeArguments (type) [0];
2693
2694                                 PropertyInfo has_value_pi = TypeManager.GetProperty (type, "HasValue");
2695                                 PropertyInfo value_pi = TypeManager.GetProperty (type, "Value");
2696
2697                                 HasValue = has_value_pi.GetGetMethod (false);
2698                                 Value = value_pi.GetGetMethod (false);
2699                                 Constructor = type.GetConstructor (new Type[] { UnderlyingType });
2700                         }
2701                 }
2702
2703                 public class Unwrap : Expression, IMemoryLocation, IAssignMethod
2704                 {
2705                         Expression expr;
2706                         NullableInfo info;
2707
2708                         LocalTemporary temp;
2709                         bool has_temp;
2710
2711                         protected Unwrap (Expression expr)
2712                         {
2713                                 this.expr = expr;
2714                                 this.loc = expr.Location;
2715                         }
2716
2717                         public static Unwrap Create (Expression expr, EmitContext ec)
2718                         {
2719                                 return new Unwrap (expr).Resolve (ec) as Unwrap;
2720                         }
2721
2722                         public override Expression DoResolve (EmitContext ec)
2723                         {
2724                                 expr = expr.Resolve (ec);
2725                                 if (expr == null)
2726                                         return null;
2727
2728                                 temp = new LocalTemporary (expr.Type);
2729
2730                                 info = new NullableInfo (expr.Type);
2731                                 type = info.UnderlyingType;
2732                                 eclass = expr.eclass;
2733                                 return this;
2734                         }
2735
2736                         public override void Emit (EmitContext ec)
2737                         {
2738                                 AddressOf (ec, AddressOp.LoadStore);
2739                                 ec.ig.EmitCall (OpCodes.Call, info.Value, null);
2740                         }
2741
2742                         public void EmitCheck (EmitContext ec)
2743                         {
2744                                 AddressOf (ec, AddressOp.LoadStore);
2745                                 ec.ig.EmitCall (OpCodes.Call, info.HasValue, null);
2746                         }
2747
2748                         public void Store (EmitContext ec)
2749                         {
2750                                 create_temp (ec);
2751                         }
2752
2753                         void create_temp (EmitContext ec)
2754                         {
2755                                 if ((temp != null) && !has_temp) {
2756                                         expr.Emit (ec);
2757                                         temp.Store (ec);
2758                                         has_temp = true;
2759                                 }
2760                         }
2761
2762                         public void AddressOf (EmitContext ec, AddressOp mode)
2763                         {
2764                                 create_temp (ec);
2765                                 if (temp != null)
2766                                         temp.AddressOf (ec, AddressOp.LoadStore);
2767                                 else
2768                                         ((IMemoryLocation) expr).AddressOf (ec, AddressOp.LoadStore);
2769                         }
2770
2771                         public void Emit (EmitContext ec, bool leave_copy)
2772                         {
2773                                 create_temp (ec);
2774                                 if (leave_copy) {
2775                                         if (temp != null)
2776                                                 temp.Emit (ec);
2777                                         else
2778                                                 expr.Emit (ec);
2779                                 }
2780
2781                                 Emit (ec);
2782                         }
2783
2784                         public void EmitAssign (EmitContext ec, Expression source,
2785                                                 bool leave_copy, bool prepare_for_load)
2786                         {
2787                                 InternalWrap wrap = new InternalWrap (source, info, loc);
2788                                 ((IAssignMethod) expr).EmitAssign (ec, wrap, leave_copy, false);
2789                         }
2790
2791                         protected class InternalWrap : Expression
2792                         {
2793                                 public Expression expr;
2794                                 public NullableInfo info;
2795
2796                                 public InternalWrap (Expression expr, NullableInfo info, Location loc)
2797                                 {
2798                                         this.expr = expr;
2799                                         this.info = info;
2800                                         this.loc = loc;
2801
2802                                         type = info.Type;
2803                                         eclass = ExprClass.Value;
2804                                 }
2805
2806                                 public override Expression DoResolve (EmitContext ec)
2807                                 {
2808                                         return this;
2809                                 }
2810
2811                                 public override void Emit (EmitContext ec)
2812                                 {
2813                                         expr.Emit (ec);
2814                                         ec.ig.Emit (OpCodes.Newobj, info.Constructor);
2815                                 }
2816                         }
2817                 }
2818
2819                 public class Wrap : Expression
2820                 {
2821                         Expression expr;
2822                         NullableInfo info;
2823
2824                         protected Wrap (Expression expr)
2825                         {
2826                                 this.expr = expr;
2827                                 this.loc = expr.Location;
2828                         }
2829
2830                         public static Wrap Create (Expression expr, EmitContext ec)
2831                         {
2832                                 return new Wrap (expr).Resolve (ec) as Wrap;
2833                         }
2834
2835                         public override Expression DoResolve (EmitContext ec)
2836                         {
2837                                 expr = expr.Resolve (ec);
2838                                 if (expr == null)
2839                                         return null;
2840
2841                                 TypeExpr target_type = new NullableType (expr.Type, loc);
2842                                 target_type = target_type.ResolveAsTypeTerminal (ec, false);
2843                                 if (target_type == null)
2844                                         return null;
2845
2846                                 type = target_type.Type;
2847                                 info = new NullableInfo (type);
2848                                 eclass = ExprClass.Value;
2849                                 return this;
2850                         }
2851
2852                         public override void Emit (EmitContext ec)
2853                         {
2854                                 expr.Emit (ec);
2855                                 ec.ig.Emit (OpCodes.Newobj, info.Constructor);
2856                         }
2857                 }
2858
2859                 public class NullableLiteral : NullLiteral, IMemoryLocation {
2860                         public NullableLiteral (Type target_type, Location loc)
2861                                 : base (loc)
2862                         {
2863                                 this.type = target_type;
2864
2865                                 eclass = ExprClass.Value;
2866                         }
2867
2868                         public override Expression DoResolve (EmitContext ec)
2869                         {
2870                                 return this;
2871                         }
2872
2873                         public override void Emit (EmitContext ec)
2874                         {
2875                                 LocalTemporary value_target = new LocalTemporary (type);
2876
2877                                 value_target.AddressOf (ec, AddressOp.Store);
2878                                 ec.ig.Emit (OpCodes.Initobj, type);
2879                                 value_target.Emit (ec);
2880                         }
2881
2882                         public void AddressOf (EmitContext ec, AddressOp Mode)
2883                         {
2884                                 LocalTemporary value_target = new LocalTemporary (type);
2885
2886                                 value_target.AddressOf (ec, AddressOp.Store);
2887                                 ec.ig.Emit (OpCodes.Initobj, type);
2888                                 ((IMemoryLocation) value_target).AddressOf (ec, Mode);
2889                         }
2890                 }
2891
2892                 public abstract class Lifted : Expression, IMemoryLocation
2893                 {
2894                         Expression expr, underlying, wrap, null_value;
2895                         Unwrap unwrap;
2896
2897                         protected Lifted (Expression expr, Location loc)
2898                         {
2899                                 this.expr = expr;
2900                                 this.loc = loc;
2901                         }
2902
2903                         public override Expression DoResolve (EmitContext ec)
2904                         {
2905                                 expr = expr.Resolve (ec);
2906                                 if (expr == null)
2907                                         return null;
2908
2909                                 unwrap = Unwrap.Create (expr, ec);
2910                                 if (unwrap == null)
2911                                         return null;
2912
2913                                 underlying = ResolveUnderlying (unwrap, ec);
2914                                 if (underlying == null)
2915                                         return null;
2916
2917                                 wrap = Wrap.Create (underlying, ec);
2918                                 if (wrap == null)
2919                                         return null;
2920
2921                                 null_value = new NullableLiteral (wrap.Type, loc).Resolve (ec);
2922                                 if (null_value == null)
2923                                         return null;
2924
2925                                 type = wrap.Type;
2926                                 eclass = ExprClass.Value;
2927                                 return this;
2928                         }
2929
2930                         protected abstract Expression ResolveUnderlying (Expression unwrap, EmitContext ec);
2931
2932                         public override void Emit (EmitContext ec)
2933                         {
2934                                 ILGenerator ig = ec.ig;
2935                                 Label is_null_label = ig.DefineLabel ();
2936                                 Label end_label = ig.DefineLabel ();
2937
2938                                 unwrap.EmitCheck (ec);
2939                                 ig.Emit (OpCodes.Brfalse, is_null_label);
2940
2941                                 wrap.Emit (ec);
2942                                 ig.Emit (OpCodes.Br, end_label);
2943
2944                                 ig.MarkLabel (is_null_label);
2945                                 null_value.Emit (ec);
2946
2947                                 ig.MarkLabel (end_label);
2948                         }
2949
2950                         public void AddressOf (EmitContext ec, AddressOp mode)
2951                         {
2952                                 unwrap.AddressOf (ec, mode);
2953                         }
2954                 }
2955
2956                 public class LiftedConversion : Lifted
2957                 {
2958                         public readonly bool IsUser;
2959                         public readonly bool IsExplicit;
2960                         public readonly Type TargetType;
2961
2962                         public LiftedConversion (Expression expr, Type target_type, bool is_user,
2963                                                  bool is_explicit, Location loc)
2964                                 : base (expr, loc)
2965                         {
2966                                 this.IsUser = is_user;
2967                                 this.IsExplicit = is_explicit;
2968                                 this.TargetType = target_type;
2969                         }
2970
2971                         protected override Expression ResolveUnderlying (Expression unwrap, EmitContext ec)
2972                         {
2973                                 Type type = TypeManager.GetTypeArguments (TargetType) [0];
2974
2975                                 if (IsUser) {
2976                                         return Convert.UserDefinedConversion (ec, unwrap, type, loc, IsExplicit);
2977                                 } else {
2978                                         if (IsExplicit)
2979                                                 return Convert.ExplicitConversion (ec, unwrap, type, loc);
2980                                         else
2981                                                 return Convert.ImplicitConversion (ec, unwrap, type, loc);
2982                                 }
2983                         }
2984                 }
2985
2986                 public class LiftedUnaryOperator : Lifted
2987                 {
2988                         public readonly Unary.Operator Oper;
2989
2990                         public LiftedUnaryOperator (Unary.Operator op, Expression expr, Location loc)
2991                                 : base (expr, loc)
2992                         {
2993                                 this.Oper = op;
2994                         }
2995
2996                         protected override Expression ResolveUnderlying (Expression unwrap, EmitContext ec)
2997                         {
2998                                 return new Unary (Oper, unwrap, loc);
2999                         }
3000                 }
3001
3002                 public class LiftedConditional : Lifted
3003                 {
3004                         Expression true_expr, false_expr;
3005
3006                         public LiftedConditional (Expression expr, Expression true_expr, Expression false_expr,
3007                                                   Location loc)
3008                                 : base (expr, loc)
3009                         {
3010                                 this.true_expr = true_expr;
3011                                 this.false_expr = false_expr;
3012                         }
3013
3014                         protected override Expression ResolveUnderlying (Expression unwrap, EmitContext ec)
3015                         {
3016                                 return new Conditional (unwrap, true_expr, false_expr);
3017                         }
3018                 }
3019
3020                 public class LiftedBinaryOperator : Expression
3021                 {
3022                         public readonly Binary.Operator Oper;
3023
3024                         Expression left, right, original_left, original_right;
3025                         Expression underlying, null_value, bool_wrap;
3026                         Unwrap left_unwrap, right_unwrap;
3027                         bool is_equality, is_comparision, is_boolean;
3028
3029                         public LiftedBinaryOperator (Binary.Operator op, Expression left, Expression right,
3030                                                      Location loc)
3031                         {
3032                                 this.Oper = op;
3033                                 this.left = original_left = left;
3034                                 this.right = original_right = right;
3035                                 this.loc = loc;
3036                         }
3037
3038                         public override Expression DoResolve (EmitContext ec)
3039                         {
3040                                 if (TypeManager.IsNullableType (left.Type)) {
3041                                         left = left_unwrap = Unwrap.Create (left, ec);
3042                                         if (left == null)
3043                                                 return null;
3044                                 }
3045
3046                                 if (TypeManager.IsNullableType (right.Type)) {
3047                                         right = right_unwrap = Unwrap.Create (right, ec);
3048                                         if (right == null)
3049                                                 return null;
3050                                 }
3051
3052                                 if ((Oper == Binary.Operator.LogicalAnd) ||
3053                                     (Oper == Binary.Operator.LogicalOr)) {
3054                                         Binary.Error_OperatorCannotBeApplied (
3055                                                 loc, Binary.OperName (Oper),
3056                                                 original_left.GetSignatureForError (),
3057                                                 original_right.GetSignatureForError ());
3058                                         return null;
3059                                 }
3060
3061                                 if (((Oper == Binary.Operator.BitwiseAnd) || (Oper == Binary.Operator.BitwiseOr)) &&
3062                                     ((left.Type == TypeManager.bool_type) && (right.Type == TypeManager.bool_type))) {
3063                                         Expression empty = new EmptyExpression (TypeManager.bool_type);
3064                                         bool_wrap = Wrap.Create (empty, ec);
3065                                         null_value = new NullableLiteral (bool_wrap.Type, loc).Resolve (ec);
3066
3067                                         type = bool_wrap.Type;
3068                                         is_boolean = true;
3069                                 } else if ((Oper == Binary.Operator.Equality) || (Oper == Binary.Operator.Inequality)) {
3070                                         if (!(left is NullLiteral) && !(right is NullLiteral)) {
3071                                                 underlying = new Binary (Oper, left, right).Resolve (ec);
3072                                                 if (underlying == null)
3073                                                         return null;
3074                                         }
3075
3076                                         type = TypeManager.bool_type;
3077                                         is_equality = true;
3078                                 } else if ((Oper == Binary.Operator.LessThan) ||
3079                                            (Oper == Binary.Operator.GreaterThan) ||
3080                                            (Oper == Binary.Operator.LessThanOrEqual) ||
3081                                            (Oper == Binary.Operator.GreaterThanOrEqual)) {
3082                                         underlying = new Binary (Oper, left, right).Resolve (ec);
3083                                         if (underlying == null)
3084                                                 return null;
3085
3086                                         type = TypeManager.bool_type;
3087                                         is_comparision = true;
3088                                 } else {
3089                                         underlying = new Binary (Oper, left, right).Resolve (ec);
3090                                         if (underlying == null)
3091                                                 return null;
3092
3093                                         underlying = Wrap.Create (underlying, ec);
3094                                         if (underlying == null)
3095                                                 return null;
3096
3097                                         type = underlying.Type;
3098                                         null_value = new NullableLiteral (type, loc).Resolve (ec);
3099                                 }
3100
3101                                 eclass = ExprClass.Value;
3102                                 return this;
3103                         }
3104
3105                         void EmitBoolean (EmitContext ec)
3106                         {
3107                                 ILGenerator ig = ec.ig;
3108
3109                                 Label left_is_null_label = ig.DefineLabel ();
3110                                 Label right_is_null_label = ig.DefineLabel ();
3111                                 Label is_null_label = ig.DefineLabel ();
3112                                 Label wrap_label = ig.DefineLabel ();
3113                                 Label end_label = ig.DefineLabel ();
3114
3115                                 if (left_unwrap != null) {
3116                                         left_unwrap.EmitCheck (ec);
3117                                         ig.Emit (OpCodes.Brfalse, left_is_null_label);
3118                                 }
3119
3120                                 left.Emit (ec);
3121                                 ig.Emit (OpCodes.Dup);
3122                                 if ((Oper == Binary.Operator.BitwiseOr) || (Oper == Binary.Operator.LogicalOr))
3123                                         ig.Emit (OpCodes.Brtrue, wrap_label);
3124                                 else
3125                                         ig.Emit (OpCodes.Brfalse, wrap_label);
3126
3127                                 if (right_unwrap != null) {
3128                                         right_unwrap.EmitCheck (ec);
3129                                         ig.Emit (OpCodes.Brfalse, right_is_null_label);
3130                                 }
3131
3132                                 if ((Oper == Binary.Operator.LogicalAnd) || (Oper == Binary.Operator.LogicalOr))
3133                                         ig.Emit (OpCodes.Pop);
3134
3135                                 right.Emit (ec);
3136                                 if (Oper == Binary.Operator.BitwiseOr)
3137                                         ig.Emit (OpCodes.Or);
3138                                 else if (Oper == Binary.Operator.BitwiseAnd)
3139                                         ig.Emit (OpCodes.And);
3140                                 ig.Emit (OpCodes.Br, wrap_label);
3141
3142                                 ig.MarkLabel (left_is_null_label);
3143                                 if (right_unwrap != null) {
3144                                         right_unwrap.EmitCheck (ec);
3145                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3146                                 }
3147
3148                                 right.Emit (ec);
3149                                 ig.Emit (OpCodes.Dup);
3150                                 if ((Oper == Binary.Operator.BitwiseOr) || (Oper == Binary.Operator.LogicalOr))
3151                                         ig.Emit (OpCodes.Brtrue, wrap_label);
3152                                 else
3153                                         ig.Emit (OpCodes.Brfalse, wrap_label);
3154
3155                                 ig.MarkLabel (right_is_null_label);
3156                                 ig.Emit (OpCodes.Pop);
3157                                 ig.MarkLabel (is_null_label);
3158                                 null_value.Emit (ec);
3159                                 ig.Emit (OpCodes.Br, end_label);
3160
3161                                 ig.MarkLabel (wrap_label);
3162                                 ig.Emit (OpCodes.Nop);
3163                                 bool_wrap.Emit (ec);
3164                                 ig.Emit (OpCodes.Nop);
3165
3166                                 ig.MarkLabel (end_label);
3167                         }
3168
3169                         void EmitEquality (EmitContext ec)
3170                         {
3171                                 ILGenerator ig = ec.ig;
3172
3173                                 // Given 'X? x;' for any value type X: 'x != null' is the same as 'x.HasValue'
3174                                 if (left is NullLiteral) {
3175                                         if (right_unwrap == null)
3176                                                 throw new InternalErrorException ();
3177                                         right_unwrap.EmitCheck (ec);
3178                                         if (Oper == Binary.Operator.Equality) {
3179                                                 ig.Emit (OpCodes.Ldc_I4_0);
3180                                                 ig.Emit (OpCodes.Ceq);
3181                                         }
3182                                         return;
3183                                 }
3184
3185                                 if (right is NullLiteral) {
3186                                         if (left_unwrap == null)
3187                                                 throw new InternalErrorException ();
3188                                         left_unwrap.EmitCheck (ec);
3189                                         if (Oper == Binary.Operator.Equality) {
3190                                                 ig.Emit (OpCodes.Ldc_I4_0);
3191                                                 ig.Emit (OpCodes.Ceq);
3192                                         }
3193                                         return;
3194                                 }
3195
3196                                 Label both_have_value_label = ig.DefineLabel ();
3197                                 Label end_label = ig.DefineLabel ();
3198
3199                                 if (left_unwrap != null && right_unwrap != null) {
3200                                         Label dissimilar_label = ig.DefineLabel ();
3201
3202                                         left_unwrap.EmitCheck (ec);
3203                                         ig.Emit (OpCodes.Dup);
3204                                         right_unwrap.EmitCheck (ec);
3205                                         ig.Emit (OpCodes.Bne_Un, dissimilar_label);
3206
3207                                         ig.Emit (OpCodes.Brtrue, both_have_value_label);
3208
3209                                         // both are null
3210                                         if (Oper == Binary.Operator.Equality)
3211                                                 ig.Emit (OpCodes.Ldc_I4_1);
3212                                         else
3213                                                 ig.Emit (OpCodes.Ldc_I4_0);
3214                                         ig.Emit (OpCodes.Br, end_label);
3215
3216                                         ig.MarkLabel (dissimilar_label);
3217                                         ig.Emit (OpCodes.Pop);
3218                                 } else if (left_unwrap != null) {
3219                                         left_unwrap.EmitCheck (ec);
3220                                         ig.Emit (OpCodes.Brtrue, both_have_value_label);
3221                                 } else if (right_unwrap != null) {
3222                                         right_unwrap.EmitCheck (ec);
3223                                         ig.Emit (OpCodes.Brtrue, both_have_value_label);
3224                                 } else {
3225                                         throw new InternalErrorException ("shouldn't get here");
3226                                 }
3227
3228                                 // one is null while the other isn't
3229                                 if (Oper == Binary.Operator.Equality)
3230                                         ig.Emit (OpCodes.Ldc_I4_0);
3231                                 else
3232                                         ig.Emit (OpCodes.Ldc_I4_1);
3233                                 ig.Emit (OpCodes.Br, end_label);
3234
3235                                 ig.MarkLabel (both_have_value_label);
3236                                 underlying.Emit (ec);
3237
3238                                 ig.MarkLabel (end_label);
3239                         }
3240
3241                         void EmitComparision (EmitContext ec)
3242                         {
3243                                 ILGenerator ig = ec.ig;
3244
3245                                 Label is_null_label = ig.DefineLabel ();
3246                                 Label end_label = ig.DefineLabel ();
3247
3248                                 if (left_unwrap != null) {
3249                                         left_unwrap.EmitCheck (ec);
3250                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3251                                 }
3252
3253                                 if (right_unwrap != null) {
3254                                         right_unwrap.EmitCheck (ec);
3255                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3256                                 }
3257
3258                                 underlying.Emit (ec);
3259                                 ig.Emit (OpCodes.Br, end_label);
3260
3261                                 ig.MarkLabel (is_null_label);
3262                                 ig.Emit (OpCodes.Ldc_I4_0);
3263
3264                                 ig.MarkLabel (end_label);
3265                         }
3266
3267                         public override void Emit (EmitContext ec)
3268                         {
3269                                 if (left_unwrap != null)
3270                                         left_unwrap.Store (ec);
3271                                 if (right_unwrap != null)
3272                                         right_unwrap.Store (ec);
3273
3274                                 if (is_boolean) {
3275                                         EmitBoolean (ec);
3276                                         return;
3277                                 } else if (is_equality) {
3278                                         EmitEquality (ec);
3279                                         return;
3280                                 } else if (is_comparision) {
3281                                         EmitComparision (ec);
3282                                         return;
3283                                 }
3284
3285                                 ILGenerator ig = ec.ig;
3286
3287                                 Label is_null_label = ig.DefineLabel ();
3288                                 Label end_label = ig.DefineLabel ();
3289
3290                                 if (left_unwrap != null) {
3291                                         left_unwrap.EmitCheck (ec);
3292                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3293                                 }
3294
3295                                 if (right_unwrap != null) {
3296                                         right_unwrap.EmitCheck (ec);
3297                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3298                                 }
3299
3300                                 underlying.Emit (ec);
3301                                 ig.Emit (OpCodes.Br, end_label);
3302
3303                                 ig.MarkLabel (is_null_label);
3304                                 null_value.Emit (ec);
3305
3306                                 ig.MarkLabel (end_label);
3307                         }
3308                 }
3309
3310                 public class OperatorTrueOrFalse : Expression
3311                 {
3312                         public readonly bool IsTrue;
3313
3314                         Expression expr;
3315                         Unwrap unwrap;
3316
3317                         public OperatorTrueOrFalse (Expression expr, bool is_true, Location loc)
3318                         {
3319                                 this.IsTrue = is_true;
3320                                 this.expr = expr;
3321                                 this.loc = loc;
3322                         }
3323
3324                         public override Expression DoResolve (EmitContext ec)
3325                         {
3326                                 unwrap = Unwrap.Create (expr, ec);
3327                                 if (unwrap == null)
3328                                         return null;
3329
3330                                 if (unwrap.Type != TypeManager.bool_type)
3331                                         return null;
3332
3333                                 type = TypeManager.bool_type;
3334                                 eclass = ExprClass.Value;
3335                                 return this;
3336                         }
3337
3338                         public override void Emit (EmitContext ec)
3339                         {
3340                                 ILGenerator ig = ec.ig;
3341
3342                                 Label is_null_label = ig.DefineLabel ();
3343                                 Label end_label = ig.DefineLabel ();
3344
3345                                 unwrap.EmitCheck (ec);
3346                                 ig.Emit (OpCodes.Brfalse, is_null_label);
3347
3348                                 unwrap.Emit (ec);
3349                                 if (!IsTrue) {
3350                                         ig.Emit (OpCodes.Ldc_I4_0);
3351                                         ig.Emit (OpCodes.Ceq);
3352                                 }
3353                                 ig.Emit (OpCodes.Br, end_label);
3354
3355                                 ig.MarkLabel (is_null_label);
3356                                 ig.Emit (OpCodes.Ldc_I4_0);
3357
3358                                 ig.MarkLabel (end_label);
3359                         }
3360                 }
3361
3362                 public class NullCoalescingOperator : Expression
3363                 {
3364                         Expression left, right;
3365                         Expression expr;
3366                         Unwrap unwrap;
3367
3368                         public NullCoalescingOperator (Expression left, Expression right, Location loc)
3369                         {
3370                                 this.left = left;
3371                                 this.right = right;
3372                                 this.loc = loc;
3373
3374                                 eclass = ExprClass.Value;
3375                         }
3376
3377                         public override Expression DoResolve (EmitContext ec)
3378                         {
3379                                 if (type != null)
3380                                         return this;
3381
3382                                 left = left.Resolve (ec);
3383                                 if (left == null)
3384                                         return null;
3385
3386                                 right = right.Resolve (ec);
3387                                 if (right == null)
3388                                         return null;
3389
3390                                 Type ltype = left.Type, rtype = right.Type;
3391
3392                                 if (!TypeManager.IsNullableType (ltype) && ltype.IsValueType) {
3393                                         Binary.Error_OperatorCannotBeApplied (loc, "??", ltype, rtype);
3394                                         return null;
3395                                 }
3396
3397                                 if (TypeManager.IsNullableType (ltype)) {
3398                                         NullableInfo info = new NullableInfo (ltype);
3399
3400                                         unwrap = Unwrap.Create (left, ec);
3401                                         if (unwrap == null)
3402                                                 return null;
3403
3404                                         expr = Convert.ImplicitConversion (ec, right, info.UnderlyingType, loc);
3405                                         if (expr != null) {
3406                                                 left = unwrap;
3407                                                 type = expr.Type;
3408                                                 return this;
3409                                         }
3410                                 }
3411
3412                                 expr = Convert.ImplicitConversion (ec, right, ltype, loc);
3413                                 if (expr != null) {
3414                                         type = expr.Type;
3415                                         return this;
3416                                 }
3417
3418                                 if (unwrap != null) {
3419                                         expr = Convert.ImplicitConversion (ec, unwrap, rtype, loc);
3420                                         if (expr != null) {
3421                                                 left = expr;
3422                                                 expr = right;
3423                                                 type = expr.Type;
3424                                                 return this;
3425                                         }
3426                                 }
3427
3428                                 Binary.Error_OperatorCannotBeApplied (loc, "??", ltype, rtype);
3429                                 return null;
3430                         }
3431
3432                         public override void Emit (EmitContext ec)
3433                         {
3434                                 ILGenerator ig = ec.ig;
3435
3436                                 Label is_null_label = ig.DefineLabel ();
3437                                 Label end_label = ig.DefineLabel ();
3438
3439                                 if (unwrap != null) {
3440                                         unwrap.EmitCheck (ec);
3441                                         ig.Emit (OpCodes.Brfalse, is_null_label);
3442
3443                                         left.Emit (ec);
3444                                         ig.Emit (OpCodes.Br, end_label);
3445
3446                                         ig.MarkLabel (is_null_label);
3447                                         expr.Emit (ec);
3448
3449                                         ig.MarkLabel (end_label);
3450                                 } else {
3451                                         left.Emit (ec);
3452                                         ig.Emit (OpCodes.Dup);
3453                                         ig.Emit (OpCodes.Brtrue, end_label);
3454
3455                                         ig.MarkLabel (is_null_label);
3456
3457                                         ig.Emit (OpCodes.Pop);
3458                                         expr.Emit (ec);
3459
3460                                         ig.MarkLabel (end_label);
3461                                 }
3462                         }
3463                 }
3464
3465                 public class LiftedUnaryMutator : ExpressionStatement
3466                 {
3467                         public readonly UnaryMutator.Mode Mode;
3468                         Expression expr, null_value;
3469                         UnaryMutator underlying;
3470                         Unwrap unwrap;
3471
3472                         public LiftedUnaryMutator (UnaryMutator.Mode mode, Expression expr, Location loc)
3473                         {
3474                                 this.expr = expr;
3475                                 this.Mode = mode;
3476                                 this.loc = loc;
3477
3478                                 eclass = ExprClass.Value;
3479                         }
3480
3481                         public override Expression DoResolve (EmitContext ec)
3482                         {
3483                                 expr = expr.Resolve (ec);
3484                                 if (expr == null)
3485                                         return null;
3486
3487                                 unwrap = Unwrap.Create (expr, ec);
3488                                 if (unwrap == null)
3489                                         return null;
3490
3491                                 underlying = (UnaryMutator) new UnaryMutator (Mode, unwrap, loc).Resolve (ec);
3492                                 if (underlying == null)
3493                                         return null;
3494
3495                                 null_value = new NullableLiteral (expr.Type, loc).Resolve (ec);
3496                                 if (null_value == null)
3497                                         return null;
3498
3499                                 type = expr.Type;
3500                                 return this;
3501                         }
3502
3503                         void DoEmit (EmitContext ec, bool is_expr)
3504                         {
3505                                 ILGenerator ig = ec.ig;
3506                                 Label is_null_label = ig.DefineLabel ();
3507                                 Label end_label = ig.DefineLabel ();
3508
3509                                 unwrap.EmitCheck (ec);
3510                                 ig.Emit (OpCodes.Brfalse, is_null_label);
3511
3512                                 if (is_expr)
3513                                         underlying.Emit (ec);
3514                                 else
3515                                         underlying.EmitStatement (ec);
3516                                 ig.Emit (OpCodes.Br, end_label);
3517
3518                                 ig.MarkLabel (is_null_label);
3519                                 if (is_expr)
3520                                         null_value.Emit (ec);
3521
3522                                 ig.MarkLabel (end_label);
3523                         }
3524
3525                         public override void Emit (EmitContext ec)
3526                         {
3527                                 DoEmit (ec, true);
3528                         }
3529
3530                         public override void EmitStatement (EmitContext ec)
3531                         {
3532                                 DoEmit (ec, false);
3533                         }
3534                 }
3535         }
3536 }