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 { return name; }
 155                 }
 156
 157                 public Constraints Clone ()
 158                 {
 159                         return new Constraints (name, constraints, loc);
 160                 }
 161
 162                 GenericParameterAttributes attrs;
 163                 TypeExpr class_constraint;
 164                 ArrayList iface_constraints;
 165                 ArrayList type_param_constraints;
 166                 int num_constraints;
 167                 Type class_constraint_type;
 168                 Type[] iface_constraint_types;
 169                 Type effective_base_type;
 170                 bool resolved;
 171                 bool resolved_types;
 172
 173                 /// <summary>
 174                 ///   Resolve the constraints - but only resolve things into Expression's, not
 175                 ///   into actual types.
 176                 /// </summary>
 177                 public bool Resolve (IResolveContext ec)
 178                 {
 179                         if (resolved)
 180                                 return true;
 181
 182                         iface_constraints = new ArrayList ();
 183                         type_param_constraints = new ArrayList ();
 184
 185                         foreach (object obj in constraints) {
 186                                 if (HasConstructorConstraint) {
 187                                         Report.Error (401, loc,
 188                                                       "The new() constraint must be last.");
 189                                         return false;
 190                                 }
 191
 192                                 if (obj is SpecialConstraint) {
 193                                         SpecialConstraint sc = (SpecialConstraint) obj;
 194
 195                                         if (sc == SpecialConstraint.Constructor) {
 196                                                 if (!HasValueTypeConstraint) {
 197                                                         attrs |= GenericParameterAttributes.DefaultConstructorConstraint;
 198                                                         continue;
 199                                                 }
 200
 201                                                 Report.Error (
 202                                                         451, loc, "The new () constraint " +
 203                                                         "cannot be used with the `struct' " +
 204                                                         "constraint.");
 205                                                 return false;
 206                                         }
 207
 208                                         if ((num_constraints > 0) || HasReferenceTypeConstraint || HasValueTypeConstraint) {
 209                                                 Report.Error (449, loc,
 210                                                               "The `class' or `struct' " +
 211                                                               "constraint must be first");
 212                                                 return false;
 213                                         }
 214
 215                                         if (sc == SpecialConstraint.ReferenceType)
 216                                                 attrs |= GenericParameterAttributes.ReferenceTypeConstraint;
 217                                         else
 218                                                 attrs |= GenericParameterAttributes.NotNullableValueTypeConstraint;
 219                                         continue;
 220                                 }
 221
 222                                 int errors = Report.Errors;
 223                                 FullNamedExpression fn = ((Expression) obj).ResolveAsTypeStep (ec, false);
 224
 225                                 if (fn == null) {
 226                                         if (errors != Report.Errors)
 227                                                 return false;
 228
 229                                         Report.Error (246, loc, "Cannot find type '{0}'", ((Expression) obj).GetSignatureForError ());
 230                                         return false;
 231                                 }
 232
 233                                 TypeExpr expr;
 234                                 ConstructedType cexpr = fn as ConstructedType;
 235                                 if (cexpr != null) {
 236                                         if (!cexpr.ResolveConstructedType (ec))
 237                                                 return false;
 238
 239                                         expr = cexpr;
 240                                 } else
 241                                         expr = fn.ResolveAsTypeTerminal (ec, false);
 242
 243                                 if ((expr == null) || (expr.Type == null))
 244                                         return false;
 245
 246                                 TypeParameterExpr texpr = expr as TypeParameterExpr;
 247                                 if (texpr != null)
 248                                         type_param_constraints.Add (expr);
 249                                 else if (expr.IsInterface)
 250                                         iface_constraints.Add (expr);
 251                                 else if (class_constraint != null) {
 252                                         Report.Error (406, loc,
 253                                                       "`{0}': the class constraint for `{1}' " +
 254                                                       "must come before any other constraints.",
 255                                                       expr.Name, name);
 256                                         return false;
 257                                 } else if (HasReferenceTypeConstraint || HasValueTypeConstraint) {
 258                                         Report.Error (450, loc, "`{0}': cannot specify both " +
 259                                                       "a constraint class and the `class' " +
 260                                                       "or `struct' constraint.", expr.Name);
 261                                         return false;
 262                                 } else
 263                                         class_constraint = expr;
 264
 265                                 num_constraints++;
 266                         }
 267
 268                         ArrayList list = new ArrayList ();
 269                         foreach (TypeExpr iface_constraint in iface_constraints) {
 270                                 foreach (Type type in list) {
 271                                         if (!type.Equals (iface_constraint.Type))
 272                                                 continue;
 273
 274                                         Report.Error (405, loc,
 275                                                       "Duplicate constraint `{0}' for type " +
 276                                                       "parameter `{1}'.", iface_constraint.GetSignatureForError (),
 277                                                       name);
 278                                         return false;
 279                                 }
 280
 281                                 list.Add (iface_constraint.Type);
 282                         }
 283
 284                         foreach (TypeParameterExpr expr in type_param_constraints) {
 285                                 foreach (Type type in list) {
 286                                         if (!type.Equals (expr.Type))
 287                                                 continue;
 288
 289                                         Report.Error (405, loc,
 290                                                       "Duplicate constraint `{0}' for type " +
 291                                                       "parameter `{1}'.", expr.GetSignatureForError (), name);
 292                                         return false;
 293                                 }
 294
 295                                 list.Add (expr.Type);
 296                         }
 297
 298                         iface_constraint_types = new Type [list.Count];
 299                         list.CopyTo (iface_constraint_types, 0);
 300
 301                         if (class_constraint != null) {
 302                                 class_constraint_type = class_constraint.Type;
 303                                 if (class_constraint_type == null)
 304                                         return false;
 305
 306                                 if (class_constraint_type.IsSealed) {
 307                                         Report.Error (701, loc,
 308                                                       "`{0}' is not a valid bound.  Bounds " +
 309                                                       "must be interfaces or non sealed " +
 310                                                       "classes", TypeManager.CSharpName (class_constraint_type));
 311                                         return false;
 312                                 }
 313
 314                                 if ((class_constraint_type == TypeManager.array_type) ||
 315                                     (class_constraint_type == TypeManager.delegate_type) ||
 316                                     (class_constraint_type == TypeManager.enum_type) ||
 317                                     (class_constraint_type == TypeManager.value_type) ||
 318                                     (class_constraint_type == TypeManager.object_type)) {
 319                                         Report.Error (702, loc,
 320                                                       "Bound cannot be special class `{0}'",
 321                                                       TypeManager.CSharpName (class_constraint_type));
 322                                         return false;
 323                                 }
 324                         }
 325
 326                         if (class_constraint_type != null)
 327                                 effective_base_type = class_constraint_type;
 328                         else if (HasValueTypeConstraint)
 329                                 effective_base_type = TypeManager.value_type;
 330                         else
 331                                 effective_base_type = TypeManager.object_type;
 332
 333                         resolved = true;
 334                         return true;
 335                 }
 336
 337                 bool CheckTypeParameterConstraints (TypeParameter tparam, Hashtable seen)
 338                 {
 339                         seen.Add (tparam, true);
 340
 341                         Constraints constraints = tparam.Constraints;
 342                         if (constraints == null)
 343                                 return true;
 344
 345                         if (constraints.HasValueTypeConstraint) {
 346                                 Report.Error (456, loc, "Type parameter `{0}' has " +
 347                                               "the `struct' constraint, so it cannot " +
 348                                               "be used as a constraint for `{1}'",
 349                                               tparam.Name, name);
 350                                 return false;
 351                         }
 352
 353                         if (constraints.type_param_constraints == null)
 354                                 return true;
 355
 356                         foreach (TypeParameterExpr expr in constraints.type_param_constraints) {
 357                                 if (seen.Contains (expr.TypeParameter)) {
 358                                         Report.Error (454, loc, "Circular constraint " +
 359                                                       "dependency involving `{0}' and `{1}'",
 360                                                       tparam.Name, expr.Name);
 361                                         return false;
 362                                 }
 363
 364                                 if (!CheckTypeParameterConstraints (expr.TypeParameter, seen))
 365                                         return false;
 366                         }
 367
 368                         return true;
 369                 }
 370
 371                 /// <summary>
 372                 ///   Resolve the constraints into actual types.
 373                 /// </summary>
 374                 public bool ResolveTypes (IResolveContext ec)
 375                 {
 376                         if (resolved_types)
 377                                 return true;
 378
 379                         resolved_types = true;
 380
 381                         foreach (object obj in constraints) {
 382                                 ConstructedType cexpr = obj as ConstructedType;
 383                                 if (cexpr == null)
 384                                         continue;
 385
 386                                 if (!cexpr.CheckConstraints (ec))
 387                                         return false;
 388                         }
 389
 390                         foreach (TypeParameterExpr expr in type_param_constraints) {
 391                                 Hashtable seen = new Hashtable ();
 392                                 if (!CheckTypeParameterConstraints (expr.TypeParameter, seen))
 393                                         return false;
 394                         }
 395
 396                         for (int i = 0; i < iface_constraints.Count; ++i) {
 397                                 TypeExpr iface_constraint = (TypeExpr) iface_constraints [i];
 398                                 iface_constraint = iface_constraint.ResolveAsTypeTerminal (ec, false);
 399                                 if (iface_constraint == null)
 400                                         return false;
 401                                 iface_constraints [i] = iface_constraint;
 402                         }
 403
 404                         if (class_constraint != null) {
 405                                 class_constraint = class_constraint.ResolveAsTypeTerminal (ec, false);
 406                                 if (class_constraint == null)
 407                                         return false;
 408                         }
 409
 410                         return true;
 411                 }
 412
 413                 /// <summary>
 414                 ///   Check whether there are no conflicts in our type parameter constraints.
 415                 ///
 416                 ///   This is an example:
 417                 ///
 418                 ///   class Foo<T,U>
 419                 ///      where T : class
 420                 ///      where U : T, struct
 421                 /// </summary>
 422                 public bool CheckDependencies ()
 423                 {
 424                         foreach (TypeParameterExpr expr in type_param_constraints) {
 425                                 if (!CheckDependencies (expr.TypeParameter))
 426                                         return false;
 427                         }
 428
 429                         return true;
 430                 }
 431
 432                 bool CheckDependencies (TypeParameter tparam)
 433                 {
 434                         Constraints constraints = tparam.Constraints;
 435                         if (constraints == null)
 436                                 return true;
 437
 438                         if (HasValueTypeConstraint && constraints.HasClassConstraint) {
 439                                 Report.Error (455, loc, "Type parameter `{0}' inherits " +
 440                                               "conflicting constraints `{1}' and `{2}'",
 441                                               name, TypeManager.CSharpName (constraints.ClassConstraint),
 442                                               "System.ValueType");
 443                                 return false;
 444                         }
 445
 446                         if (HasClassConstraint && constraints.HasClassConstraint) {
 447                                 Type t1 = ClassConstraint;
 448                                 TypeExpr e1 = class_constraint;
 449                                 Type t2 = constraints.ClassConstraint;
 450                                 TypeExpr e2 = constraints.class_constraint;
 451
 452                                 if (!Convert.ImplicitReferenceConversionExists (e1, t2) &&
 453                                     !Convert.ImplicitReferenceConversionExists (e2, t1)) {
 454                                         Report.Error (455, loc,
 455                                                       "Type parameter `{0}' inherits " +
 456                                                       "conflicting constraints `{1}' and `{2}'",
 457                                                       name, TypeManager.CSharpName (t1), TypeManager.CSharpName (t2));
 458                                         return false;
 459                                 }
 460                         }
 461
 462                         if (constraints.type_param_constraints == null)
 463                                 return true;
 464
 465                         foreach (TypeParameterExpr expr in constraints.type_param_constraints) {
 466                                 if (!CheckDependencies (expr.TypeParameter))
 467                                         return false;
 468                         }
 469
 470                         return true;
 471                 }
 472
 473                 public override GenericParameterAttributes Attributes {
 474                         get { return attrs; }
 475                 }
 476
 477                 public override bool HasClassConstraint {
 478                         get { return class_constraint != null; }
 479                 }
 480
 481                 public override Type ClassConstraint {
 482                         get { return class_constraint_type; }
 483                 }
 484
 485                 public override Type[] InterfaceConstraints {
 486                         get { return iface_constraint_types; }
 487                 }
 488
 489                 public override Type EffectiveBaseClass {
 490                         get { return effective_base_type; }
 491                 }
 492
 493                 public bool IsSubclassOf (Type t)
 494                 {
 495                         if ((class_constraint_type != null) &&
 496                             class_constraint_type.IsSubclassOf (t))
 497                                 return true;
 498
 499                         if (iface_constraint_types == null)
 500                                 return false;
 501
 502                         foreach (Type iface in iface_constraint_types) {
 503                                 if (TypeManager.IsSubclassOf (iface, t))
 504                                         return true;
 505                         }
 506
 507                         return false;
 508                 }
 509
 510                 public Location Location {
 511                         get {
 512                                 return loc;
 513                         }
 514                 }
 515
 516                 /// <summary>
 517                 ///   This is used when we're implementing a generic interface method.
 518                 ///   Each method type parameter in implementing method must have the same
 519                 ///   constraints than the corresponding type parameter in the interface
 520                 ///   method.  To do that, we're called on each of the implementing method's
 521                 ///   type parameters.
 522                 /// </summary>
 523                 public bool CheckInterfaceMethod (GenericConstraints gc)
 524                 {
 525                         if (gc.Attributes != attrs)
 526                                 return false;
 527
 528                         if (HasClassConstraint != gc.HasClassConstraint)
 529                                 return false;
 530                         if (HasClassConstraint && !TypeManager.IsEqual (gc.ClassConstraint, ClassConstraint))
 531                                 return false;
 532
 533                         int gc_icount = gc.InterfaceConstraints != null ?
 534                                 gc.InterfaceConstraints.Length : 0;
 535                         int icount = InterfaceConstraints != null ?
 536                                 InterfaceConstraints.Length : 0;
 537
 538                         if (gc_icount != icount)
 539                                 return false;
 540
 541                         foreach (Type iface in gc.InterfaceConstraints) {
 542                                 bool ok = false;
 543                                 foreach (Type check in InterfaceConstraints) {
 544                                         if (TypeManager.IsEqual (iface, check)) {
 545                                                 ok = true;
 546                                                 break;
 547                                         }
 548                                 }
 549
 550                                 if (!ok)
 551                                         return false;
 552                         }
 553
 554                         return true;
 555                 }
 556         }
 557
 558         /// <summary>
 559         ///   A type parameter from a generic type definition.
 560         /// </summary>
 561         public class TypeParameter : MemberCore, IMemberContainer {
 562                 string name;
 563                 DeclSpace decl;
 564                 GenericConstraints gc;
 565                 Constraints constraints;
 566                 Location loc;
 567                 GenericTypeParameterBuilder type;
 568
 569                 public TypeParameter (DeclSpace parent, DeclSpace decl, string name,
 570                                       Constraints constraints, Attributes attrs, Location loc)
 571                         : base (parent, new MemberName (name, loc), attrs)
 572                 {
 573                         this.name = name;
 574                         this.decl = decl;
 575                         this.constraints = constraints;
 576                         this.loc = loc;
 577                 }
 578
 579                 public GenericConstraints GenericConstraints {
 580                         get { return gc != null ? gc : constraints; }
 581                 }
 582
 583                 public Constraints Constraints {
 584                         get { return constraints; }
 585                 }
 586
 587                 public bool HasConstructorConstraint {
 588                         get { return constraints != null && constraints.HasConstructorConstraint; }
 589                 }
 590
 591                 public DeclSpace DeclSpace {
 592                         get { return decl; }
 593                 }
 594
 595                 public Type Type {
 596                         get { return type; }
 597                 }
 598
 599                 /// <summary>
 600                 ///   This is the first method which is called during the resolving
 601                 ///   process; we're called immediately after creating the type parameters
 602                 ///   with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
 603                 ///   MethodBuilder).
 604                 ///
 605                 ///   We're either called from TypeContainer.DefineType() or from
 606                 ///   GenericMethod.Define() (called from Method.Define()).
 607                 /// </summary>
 608                 public void Define (GenericTypeParameterBuilder type)
 609                 {
 610                         if (this.type != null)
 611                                 throw new InvalidOperationException ();
 612
 613                         this.type = type;
 614                         TypeManager.AddTypeParameter (type, this);
 615                 }
 616
 617                 /// <summary>
 618                 ///   This is the second method which is called during the resolving
 619                 ///   process - in case of class type parameters, we're called from
 620                 ///   TypeContainer.ResolveType() - after it resolved the class'es
 621                 ///   base class and interfaces. For method type parameters, we're
 622                 ///   called immediately after Define().
 623                 ///
 624                 ///   We're just resolving the constraints into expressions here, we
 625                 ///   don't resolve them into actual types.
 626                 ///
 627                 ///   Note that in the special case of partial generic classes, we may be
 628                 ///   called _before_ Define() and we may also be called multiple types.
 629                 /// </summary>
 630                 public bool Resolve (DeclSpace ds)
 631                 {
 632                         if (constraints != null) {
 633                                 if (!constraints.Resolve (ds)) {
 634                                         constraints = null;
 635                                         return false;
 636                                 }
 637                         }
 638
 639                         return true;
 640                 }
 641
 642                 /// <summary>
 643                 ///   This is the third method which is called during the resolving
 644                 ///   process.  We're called immediately after calling DefineConstraints()
 645                 ///   on all of the current class'es type parameters.
 646                 ///
 647                 ///   Our job is to resolve the constraints to actual types.
 648                 ///
 649                 ///   Note that we may have circular dependencies on type parameters - this
 650                 ///   is why Resolve() and ResolveType() are separate.
 651                 /// </summary>
 652                 public bool ResolveType (IResolveContext ec)
 653                 {
 654                         if (constraints != null) {
 655                                 if (!constraints.ResolveTypes (ec)) {
 656                                         constraints = null;
 657                                         return false;
 658                                 }
 659                         }
 660
 661                         return true;
 662                 }
 663
 664                 /// <summary>
 665                 ///   This is the fourth and last method which is called during the resolving
 666                 ///   process.  We're called after everything is fully resolved and actually
 667                 ///   register the constraints with SRE and the TypeManager.
 668                 /// </summary>
 669                 public bool DefineType (IResolveContext ec)
 670                 {
 671                         return DefineType (ec, null, null, false);
 672                 }
 673
 674                 /// <summary>
 675                 ///   This is the fith and last method which is called during the resolving
 676                 ///   process.  We're called after everything is fully resolved and actually
 677                 ///   register the constraints with SRE and the TypeManager.
 678                 ///
 679                 ///   The `builder', `implementing' and `is_override' arguments are only
 680                 ///   applicable to method type parameters.
 681                 /// </summary>
 682                 public bool DefineType (IResolveContext ec, MethodBuilder builder,
 683                                         MethodInfo implementing, bool is_override)
 684                 {
 685                         if (!ResolveType (ec))
 686                                 return false;
 687
 688                         if (implementing != null) {
 689                                 if (is_override && (constraints != null)) {
 690                                         Report.Error (
 691                                                 460, loc, "Constraints for override and " +
 692                                                 "explicit interface implementation methods " +
 693                                                 "are inherited from the base method so they " +
 694                                                 "cannot be specified directly");
 695                                         return false;
 696                                 }
 697
 698                                 MethodBase mb = TypeManager.DropGenericMethodArguments (implementing);
 699
 700                                 int pos = type.GenericParameterPosition;
 701                                 Type mparam = mb.GetGenericArguments () [pos];
 702                                 GenericConstraints temp_gc = ReflectionConstraints.GetConstraints (mparam);
 703
 704                                 if (temp_gc != null)
 705                                         gc = new InflatedConstraints (temp_gc, implementing.DeclaringType);
 706                                 else if (constraints != null)
 707                                         gc = new InflatedConstraints (constraints, implementing.DeclaringType);
 708
 709                                 bool ok = true;
 710                                 if (constraints != null) {
 711                                         if (temp_gc == null)
 712                                                 ok = false;
 713                                         else if (!constraints.CheckInterfaceMethod (gc))
 714                                                 ok = false;
 715                                 } else {
 716                                         if (!is_override && (temp_gc != null))
 717                                                 ok = false;
 718                                 }
 719
 720                                 if (!ok) {
 721                                         Report.SymbolRelatedToPreviousError (implementing);
 722
 723                                         Report.Error (
 724                                                 425, loc, "The constraints for type " +
 725                                                 "parameter `{0}' of method `{1}' must match " +
 726                                                 "the constraints for type parameter `{2}' " +
 727                                                 "of interface method `{3}'. Consider using " +
 728                                                 "an explicit interface implementation instead",
 729                                                 Name, TypeManager.CSharpSignature (builder),
 730                                                 TypeManager.CSharpName (mparam), TypeManager.CSharpSignature (mb));
 731                                         return false;
 732                                 }
 733                         } else if (DeclSpace is CompilerGeneratedClass) {
 734                                 TypeParameter[] tparams = DeclSpace.TypeParameters;
 735                                 Type[] types = new Type [tparams.Length];
 736                                 for (int i = 0; i < tparams.Length; i++)
 737                                         types [i] = tparams [i].Type;
 738
 739                                 if (constraints != null)
 740                                         gc = new InflatedConstraints (constraints, types);
 741                         } else {
 742                                 gc = (GenericConstraints) constraints;
 743                         }
 744
 745                         if (gc == null)
 746                                 return true;
 747
 748                         if (gc.HasClassConstraint)
 749                                 type.SetBaseTypeConstraint (gc.ClassConstraint);
 750
 751                         type.SetInterfaceConstraints (gc.InterfaceConstraints);
 752                         type.SetGenericParameterAttributes (gc.Attributes);
 753                         TypeManager.RegisterBuilder (type, gc.InterfaceConstraints);
 754
 755                         return true;
 756                 }
 757
 758                 /// <summary>
 759                 ///   Check whether there are no conflicts in our type parameter constraints.
 760                 ///
 761                 ///   This is an example:
 762                 ///
 763                 ///   class Foo<T,U>
 764                 ///      where T : class
 765                 ///      where U : T, struct
 766                 /// </summary>
 767                 public bool CheckDependencies ()
 768                 {
 769                         if (constraints != null)
 770                                 return constraints.CheckDependencies ();
 771
 772                         return true;
 773                 }
 774
 775                 /// <summary>
 776                 ///   This is called for each part of a partial generic type definition.
 777                 ///
 778                 ///   If `new_constraints' is not null and we don't already have constraints,
 779                 ///   they become our constraints.  If we already have constraints, we must
 780                 ///   check that they're the same.
 781                 ///   con
 782                 /// </summary>
 783                 public bool UpdateConstraints (IResolveContext ec, Constraints new_constraints)
 784                 {
 785                         if (type == null)
 786                                 throw new InvalidOperationException ();
 787
 788                         if (new_constraints == null)
 789                                 return true;
 790
 791                         if (!new_constraints.Resolve (ec))
 792                                 return false;
 793                         if (!new_constraints.ResolveTypes (ec))
 794                                 return false;
 795
 796                         if (constraints != null)
 797                                 return constraints.CheckInterfaceMethod (new_constraints);
 798
 799                         constraints = new_constraints;
 800                         return true;
 801                 }
 802
 803                 public void EmitAttributes ()
 804                 {
 805                         if (OptAttributes != null)
 806                                 OptAttributes.Emit ();
 807                 }
 808
 809                 public override string DocCommentHeader {
 810                         get {
 811                                 throw new InvalidOperationException (
 812                                         "Unexpected attempt to get doc comment from " + this.GetType () + ".");
 813                         }
 814                 }
 815
 816                 //
 817                 // MemberContainer
 818                 //
 819
 820                 public override bool Define ()
 821                 {
 822                         return true;
 823                 }
 824
 825                 public override void ApplyAttributeBuilder (Attribute a,
 826                                                             CustomAttributeBuilder cb)
 827                 {
 828                         type.SetCustomAttribute (cb);
 829                 }
 830
 831                 public override AttributeTargets AttributeTargets {
 832                         get {
 833                                 return (AttributeTargets) AttributeTargets.GenericParameter;
 834                         }
 835                 }
 836
 837                 public override string[] ValidAttributeTargets {
 838                         get {
 839                                 return new string [] { "type parameter" };
 840                         }
 841                 }
 842
 843                 //
 844                 // IMemberContainer
 845                 //
 846
 847                 string IMemberContainer.Name {
 848                         get { return Name; }
 849                 }
 850
 851                 MemberCache IMemberContainer.BaseCache {
 852                         get { return null; }
 853                 }
 854
 855                 bool IMemberContainer.IsInterface {
 856                         get { return true; }
 857                 }
 858
 859                 MemberList IMemberContainer.GetMembers (MemberTypes mt, BindingFlags bf)
 860                 {
 861                         return FindMembers (mt, bf, null, null);
 862                 }
 863
 864                 MemberCache IMemberContainer.MemberCache {
 865                         get { return null; }
 866                 }
 867
 868                 public MemberList FindMembers (MemberTypes mt, BindingFlags bf,
 869                                                MemberFilter filter, object criteria)
 870                 {
 871                         if (constraints == null)
 872                                 return MemberList.Empty;
 873
 874                         ArrayList members = new ArrayList ();
 875
 876                         if (gc.HasClassConstraint) {
 877                                 MemberList list = TypeManager.FindMembers (
 878                                         gc.ClassConstraint, mt, bf, filter, criteria);
 879
 880                                 members.AddRange (list);
 881                         }
 882
 883                         Type[] ifaces = TypeManager.ExpandInterfaces (gc.InterfaceConstraints);
 884                         foreach (Type t in ifaces) {
 885                                 MemberList list = TypeManager.FindMembers (
 886                                         t, mt, bf, filter, criteria);
 887
 888                                 members.AddRange (list);
 889                         }
 890
 891                         return new MemberList (members);
 892                 }
 893
 894                 public bool IsSubclassOf (Type t)
 895                 {
 896                         if (type.Equals (t))
 897                                 return true;
 898
 899                         if (constraints != null)
 900                                 return constraints.IsSubclassOf (t);
 901
 902                         return false;
 903                 }
 904
 905                 public override string ToString ()
 906                 {
 907                         return "TypeParameter[" + name + "]";
 908                 }
 909
 910                 public static string GetSignatureForError (TypeParameter[] tp)
 911                 {
 912                         if (tp == null || tp.Length == 0)
 913                                 return "";
 914
 915                         StringBuilder sb = new StringBuilder ("<");
 916                         for (int i = 0; i < tp.Length; ++i) {
 917                                 if (i > 0)
 918                                         sb.Append (",");
 919                                 sb.Append (tp[i].GetSignatureForError ());
 920                         }
 921                         sb.Append ('>');
 922                         return sb.ToString ();
 923                 }
 924
 925                 public void InflateConstraints (Type declaring)
 926                 {
 927                         if (constraints != null)
 928                                 gc = new InflatedConstraints (constraints, declaring);
 929                 }
 930
 931                 protected class InflatedConstraints : GenericConstraints
 932                 {
 933                         GenericConstraints gc;
 934                         Type base_type;
 935                         Type class_constraint;
 936                         Type[] iface_constraints;
 937                         Type[] dargs;
 938
 939                         public InflatedConstraints (GenericConstraints gc, Type declaring)
 940                                 : this (gc, TypeManager.GetTypeArguments (declaring))
 941                         { }
 942
 943                         public InflatedConstraints (GenericConstraints gc, Type[] dargs)
 944                         {
 945                                 this.gc = gc;
 946                                 this.dargs = dargs;
 947
 948                                 ArrayList list = new ArrayList ();
 949                                 if (gc.HasClassConstraint)
 950                                         list.Add (inflate (gc.ClassConstraint));
 951                                 foreach (Type iface in gc.InterfaceConstraints)
 952                                         list.Add (inflate (iface));
 953
 954                                 bool has_class_constr = false;
 955                                 if (list.Count > 0) {
 956                                         Type first = (Type) list [0];
 957                                         has_class_constr = !first.IsInterface && !first.IsGenericParameter;
 958                                 }
 959
 960                                 if ((list.Count > 0) && has_class_constr) {
 961                                         class_constraint = (Type) list [0];
 962                                         iface_constraints = new Type [list.Count - 1];
 963                                         list.CopyTo (1, iface_constraints, 0, list.Count - 1);
 964                                 } else {
 965                                         iface_constraints = new Type [list.Count];
 966                                         list.CopyTo (iface_constraints, 0);
 967                                 }
 968
 969                                 if (HasValueTypeConstraint)
 970                                         base_type = TypeManager.value_type;
 971                                 else if (class_constraint != null)
 972                                         base_type = class_constraint;
 973                                 else
 974                                         base_type = TypeManager.object_type;
 975                         }
 976
 977                         Type inflate (Type t)
 978                         {
 979                                 if (t == null)
 980                                         return null;
 981                                 if (t.IsGenericParameter)
 982                                         return dargs [t.GenericParameterPosition];
 983                                 if (t.IsGenericType) {
 984                                         Type[] args = t.GetGenericArguments ();
 985                                         Type[] inflated = new Type [args.Length];
 986
 987                                         for (int i = 0; i < args.Length; i++)
 988                                                 inflated [i] = inflate (args [i]);
 989
 990                                         t = t.GetGenericTypeDefinition ();
 991                                         t = t.MakeGenericType (inflated);
 992                                 }
 993
 994                                 return t;
 995                         }
 996
 997                         public override string TypeParameter {
 998                                 get { return gc.TypeParameter; }
 999                         }
1000
1001                         public override GenericParameterAttributes Attributes {
1002                                 get { return gc.Attributes; }
1003                         }
1004
1005                         public override Type ClassConstraint {
1006                                 get { return class_constraint; }
1007                         }
1008
1009                         public override Type EffectiveBaseClass {
1010                                 get { return base_type; }
1011                         }
1012
1013                         public override Type[] InterfaceConstraints {
1014                                 get { return iface_constraints; }
1015                         }
1016                 }
1017         }
1018
1019         /// <summary>
1020         ///   A TypeExpr which already resolved to a type parameter.
1021         /// </summary>
1022         public class TypeParameterExpr : TypeExpr {
1023                 TypeParameter type_parameter;
1024
1025                 public override string Name {
1026                         get {
1027                                 return type_parameter.Name;
1028                         }
1029                 }
1030
1031                 public override string FullName {
1032                         get {
1033                                 return type_parameter.Name;
1034                         }
1035                 }
1036
1037                 public TypeParameter TypeParameter {
1038                         get {
1039                                 return type_parameter;
1040                         }
1041                 }
1042
1043                 public TypeParameterExpr (TypeParameter type_parameter, Location loc)
1044                 {
1045                         this.type_parameter = type_parameter;
1046                         this.loc = loc;
1047                 }
1048
1049                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1050                 {
1051                         type = type_parameter.Type;
1052
1053                         return this;
1054                 }
1055
1056                 public override bool IsInterface {
1057                         get { return false; }
1058                 }
1059
1060                 public override bool CheckAccessLevel (DeclSpace ds)
1061                 {
1062                         return true;
1063                 }
1064
1065                 public void Error_CannotUseAsUnmanagedType (Location loc)
1066                 {
1067                         Report.Error (-203, loc, "Can not use type parameter as unmanaged type");
1068                 }
1069         }
1070
1071         /// <summary>
1072         ///   Tracks the type arguments when instantiating a generic type.  We're used in
1073         ///   ConstructedType.
1074         /// </summary>
1075         public class TypeArguments {
1076                 public readonly Location Location;
1077                 ArrayList args;
1078                 Type[] atypes;
1079                 int dimension;
1080                 bool has_type_args;
1081                 bool created;
1082
1083                 public TypeArguments (Location loc)
1084                 {
1085                         args = new ArrayList ();
1086                         this.Location = loc;
1087                 }
1088
1089                 public TypeArguments (int dimension, Location loc)
1090                 {
1091                         this.dimension = dimension;
1092                         this.Location = loc;
1093                 }
1094
1095                 public void Add (Expression type)
1096                 {
1097                         if (created)
1098                                 throw new InvalidOperationException ();
1099
1100                         args.Add (type);
1101                 }
1102
1103                 public void Add (TypeArguments new_args)
1104                 {
1105                         if (created)
1106                                 throw new InvalidOperationException ();
1107
1108                         args.AddRange (new_args.args);
1109                 }
1110
1111                 /// <summary>
1112                 ///   We're used during the parsing process: the parser can't distinguish
1113                 ///   between type parameters and type arguments.  Because of that, the
1114                 ///   parser creates a `MemberName' with `TypeArguments' for both cases and
1115                 ///   in case of a generic type definition, we call GetDeclarations().
1116                 /// </summary>
1117                 public TypeParameterName[] GetDeclarations ()
1118                 {
1119                         TypeParameterName[] ret = new TypeParameterName [args.Count];
1120                         for (int i = 0; i < args.Count; i++) {
1121                                 TypeParameterName name = args [i] as TypeParameterName;
1122                                 if (name != null) {
1123                                         ret [i] = name;
1124                                         continue;
1125                                 }
1126                                 SimpleName sn = args [i] as SimpleName;
1127                                 if (sn != null) {
1128                                         ret [i] = new TypeParameterName (sn.Name, null, sn.Location);
1129                                         continue;
1130                                 }
1131
1132                                 Report.Error (81, Location, "Type parameter declaration " +
1133                                               "must be an identifier not a type");
1134                                 return null;
1135                         }
1136                         return ret;
1137                 }
1138
1139                 /// <summary>
1140                 ///   We may only be used after Resolve() is called and return the fully
1141                 ///   resolved types.
1142                 /// </summary>
1143                 public Type[] Arguments {
1144                         get {
1145                                 return atypes;
1146                         }
1147                 }
1148
1149                 public bool HasTypeArguments {
1150                         get {
1151                                 return has_type_args;
1152                         }
1153                 }
1154
1155                 public int Count {
1156                         get {
1157                                 if (dimension > 0)
1158                                         return dimension;
1159                                 else
1160                                         return args.Count;
1161                         }
1162                 }
1163
1164                 public bool IsUnbound {
1165                         get {
1166                                 return dimension > 0;
1167                         }
1168                 }
1169
1170                 public override string ToString ()
1171                 {
1172                         StringBuilder s = new StringBuilder ();
1173
1174                         int count = Count;
1175                         for (int i = 0; i < count; i++){
1176                                 //
1177                                 // FIXME: Use TypeManager.CSharpname once we have the type
1178                                 //
1179                                 if (args != null)
1180                                         s.Append (args [i].ToString ());
1181                                 if (i+1 < count)
1182                                         s.Append (",");
1183                         }
1184                         return s.ToString ();
1185                 }
1186
1187                 /// <summary>
1188                 ///   Resolve the type arguments.
1189                 /// </summary>
1190                 public bool Resolve (IResolveContext ec)
1191                 {
1192                         int count = args.Count;
1193                         bool ok = true;
1194
1195                         atypes = new Type [count];
1196
1197                         for (int i = 0; i < count; i++){
1198                                 TypeExpr te = ((Expression) args [i]).ResolveAsTypeTerminal (ec, false);
1199                                 if (te == null) {
1200                                         ok = false;
1201                                         continue;
1202                                 }
1203                                 if (te is TypeParameterExpr)
1204                                         has_type_args = true;
1205
1206                                 if (te.Type.IsPointer) {
1207                                         Report.Error (306, Location, "The type `{0}' may not be used " +
1208                                                       "as a type argument", TypeManager.CSharpName (te.Type));
1209                                         return false;
1210                                 } else if (te.Type == TypeManager.void_type) {
1211                                         Report.Error (1547, Location,
1212                                                       "Keyword `void' cannot be used in this context");
1213                                         return false;
1214                                 }
1215
1216                                 atypes [i] = te.Type;
1217                         }
1218                         return ok;
1219                 }
1220         }
1221
1222         public class TypeParameterName : SimpleName
1223         {
1224                 Attributes attributes;
1225
1226                 public TypeParameterName (string name, Attributes attrs, Location loc)
1227                         : base (name, loc)
1228                 {
1229                         attributes = attrs;
1230                 }
1231
1232                 public Attributes OptAttributes {
1233                         get {
1234                                 return attributes;
1235                         }
1236                 }
1237         }
1238
1239         /// <summary>
1240         ///   An instantiation of a generic type.
1241         /// </summary>
1242         public class ConstructedType : TypeExpr {
1243                 string full_name;
1244                 FullNamedExpression name;
1245                 TypeArguments args;
1246                 Type[] gen_params, atypes;
1247                 Type gt;
1248
1249                 /// <summary>
1250                 ///   Instantiate the generic type `fname' with the type arguments `args'.
1251                 /// </summary>
1252                 public ConstructedType (FullNamedExpression fname, TypeArguments args, Location l)
1253                 {
1254                         loc = l;
1255                         this.name = fname;
1256                         this.args = args;
1257
1258                         eclass = ExprClass.Type;
1259                         full_name = name + "<" + args.ToString () + ">";
1260                 }
1261
1262                 protected ConstructedType (TypeArguments args, Location l)
1263                 {
1264                         loc = l;
1265                         this.args = args;
1266
1267                         eclass = ExprClass.Type;
1268                 }
1269
1270                 protected ConstructedType (TypeParameter[] type_params, Location l)
1271                 {
1272                         loc = l;
1273
1274                         args = new TypeArguments (l);
1275                         foreach (TypeParameter type_param in type_params)
1276                                 args.Add (new TypeParameterExpr (type_param, l));
1277
1278                         eclass = ExprClass.Type;
1279                 }
1280
1281                 /// <summary>
1282                 ///   This is used to construct the `this' type inside a generic type definition.
1283                 /// </summary>
1284                 public ConstructedType (Type t, TypeParameter[] type_params, Location l)
1285                         : this (type_params, l)
1286                 {
1287                         gt = t.GetGenericTypeDefinition ();
1288
1289                         this.name = new TypeExpression (gt, l);
1290                         full_name = gt.FullName + "<" + args.ToString () + ">";
1291                 }
1292
1293                 /// <summary>
1294                 ///   Instantiate the generic type `t' with the type arguments `args'.
1295                 ///   Use this constructor if you already know the fully resolved
1296                 ///   generic type.
1297                 /// </summary>
1298                 public ConstructedType (Type t, TypeArguments args, Location l)
1299                         : this (args, l)
1300                 {
1301                         gt = t.GetGenericTypeDefinition ();
1302
1303                         this.name = new TypeExpression (gt, l);
1304                         full_name = gt.FullName + "<" + args.ToString () + ">";
1305                 }
1306
1307                 public TypeArguments TypeArguments {
1308                         get { return args; }
1309                 }
1310
1311                 public override string GetSignatureForError ()
1312                 {
1313                         return TypeManager.CSharpName (gt);
1314                 }
1315
1316                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1317                 {
1318                         if (!ResolveConstructedType (ec))
1319                                 return null;
1320
1321                         return this;
1322                 }
1323
1324                 /// <summary>
1325                 ///   Check the constraints; we're called from ResolveAsTypeTerminal()
1326                 ///   after fully resolving the constructed type.
1327                 /// </summary>
1328                 public bool CheckConstraints (IResolveContext ec)
1329                 {
1330                         return ConstraintChecker.CheckConstraints (ec, gt, gen_params, atypes, loc);
1331                 }
1332
1333                 /// <summary>
1334                 ///   Resolve the constructed type, but don't check the constraints.
1335                 /// </summary>
1336                 public bool ResolveConstructedType (IResolveContext ec)
1337                 {
1338                         if (type != null)
1339                                 return true;
1340                         // If we already know the fully resolved generic type.
1341                         if (gt != null)
1342                                 return DoResolveType (ec);
1343
1344                         int num_args;
1345                         Type t = name.Type;
1346
1347                         if (t == null) {
1348                                 Report.Error (246, loc, "Cannot find type `{0}'<...>", Name);
1349                                 return false;
1350                         }
1351
1352                         num_args = TypeManager.GetNumberOfTypeArguments (t);
1353                         if (num_args == 0) {
1354                                 Report.Error (308, loc,
1355                                               "The non-generic type `{0}' cannot " +
1356                                               "be used with type arguments.",
1357                                               TypeManager.CSharpName (t));
1358                                 return false;
1359                         }
1360
1361                         gt = t.GetGenericTypeDefinition ();
1362                         return DoResolveType (ec);
1363                 }
1364
1365                 bool DoResolveType (IResolveContext ec)
1366                 {
1367                         //
1368                         // Resolve the arguments.
1369                         //
1370                         if (args.Resolve (ec) == false)
1371                                 return false;
1372
1373                         gen_params = gt.GetGenericArguments ();
1374                         atypes = args.Arguments;
1375
1376                         if (atypes.Length != gen_params.Length) {
1377                                 Report.Error (305, loc,
1378                                               "Using the generic type `{0}' " +
1379                                               "requires {1} type arguments",
1380                                               TypeManager.CSharpName (gt),
1381                                               gen_params.Length.ToString ());
1382                                 return false;
1383                         }
1384
1385                         //
1386                         // Now bind the parameters.
1387                         //
1388                         type = gt.MakeGenericType (atypes);
1389                         return true;
1390                 }
1391
1392                 public Expression GetSimpleName (EmitContext ec)
1393                 {
1394                         return this;
1395                 }
1396
1397                 public override bool CheckAccessLevel (DeclSpace ds)
1398                 {
1399                         return ds.CheckAccessLevel (gt);
1400                 }
1401
1402                 public override bool AsAccessible (DeclSpace ds, int flags)
1403                 {
1404                         return ds.AsAccessible (gt, flags);
1405                 }
1406
1407                 public override bool IsClass {
1408                         get { return gt.IsClass; }
1409                 }
1410
1411                 public override bool IsValueType {
1412                         get { return gt.IsValueType; }
1413                 }
1414
1415                 public override bool IsInterface {
1416                         get { return gt.IsInterface; }
1417                 }
1418
1419                 public override bool IsSealed {
1420                         get { return gt.IsSealed; }
1421                 }
1422
1423                 public override bool Equals (object obj)
1424                 {
1425                         ConstructedType cobj = obj as ConstructedType;
1426                         if (cobj == null)
1427                                 return false;
1428
1429                         if ((type == null) || (cobj.type == null))
1430                                 return false;
1431
1432                         return type == cobj.type;
1433                 }
1434
1435                 public override int GetHashCode ()
1436                 {
1437                         return base.GetHashCode ();
1438                 }
1439
1440                 public override string Name {
1441                         get {
1442                                 return full_name;
1443                         }
1444                 }
1445
1446
1447                 public override string FullName {
1448                         get {
1449                                 return full_name;
1450                         }
1451                 }
1452         }
1453
1454         public abstract class ConstraintChecker
1455         {
1456                 protected readonly Type[] gen_params;
1457                 protected readonly Type[] atypes;
1458                 protected readonly Location loc;
1459
1460                 protected ConstraintChecker (Type[] gen_params, Type[] atypes, Location loc)
1461                 {
1462                         this.gen_params = gen_params;
1463                         this.atypes = atypes;
1464                         this.loc = loc;
1465                 }
1466
1467                 /// <summary>
1468                 ///   Check the constraints; we're called from ResolveAsTypeTerminal()
1469                 ///   after fully resolving the constructed type.
1470                 /// </summary>
1471                 public bool CheckConstraints (IResolveContext ec)
1472                 {
1473                         for (int i = 0; i < gen_params.Length; i++) {
1474                                 if (!CheckConstraints (ec, i))
1475                                         return false;
1476                         }
1477
1478                         return true;
1479                 }
1480
1481                 protected bool CheckConstraints (IResolveContext ec, int index)
1482                 {
1483                         Type atype = atypes [index];
1484                         Type ptype = gen_params [index];
1485
1486                         if (atype == ptype)
1487                                 return true;
1488
1489                         Expression aexpr = new EmptyExpression (atype);
1490
1491                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (ptype);
1492                         if (gc == null)
1493                                 return true;
1494
1495                         bool is_class, is_struct;
1496                         if (atype.IsGenericParameter) {
1497                                 GenericConstraints agc = TypeManager.GetTypeParameterConstraints (atype);
1498                                 if (agc != null) {
1499                                         if (agc is Constraints)
1500                                                 ((Constraints) agc).Resolve (ec);
1501                                         is_class = agc.HasReferenceTypeConstraint;
1502                                         is_struct = agc.HasValueTypeConstraint;
1503                                 } else {
1504                                         is_class = is_struct = false;
1505                                 }
1506                         } else {
1507 #if MS_COMPATIBLE
1508                                 is_class = false;
1509                                 if (!atype.IsGenericType)
1510 #endif
1511                                 is_class = atype.IsClass || atype.IsInterface;
1512                                 is_struct = atype.IsValueType && !TypeManager.IsNullableType (atype);
1513                         }
1514
1515                         //
1516                         // First, check the `class' and `struct' constraints.
1517                         //
1518                         if (gc.HasReferenceTypeConstraint && !is_class) {
1519                                 Report.Error (452, loc, "The type `{0}' must be " +
1520                                               "a reference type in order to use it " +
1521                                               "as type parameter `{1}' in the " +
1522                                               "generic type or method `{2}'.",
1523                                               TypeManager.CSharpName (atype),
1524                                               TypeManager.CSharpName (ptype),
1525                                               GetSignatureForError ());
1526                                 return false;
1527                         } else if (gc.HasValueTypeConstraint && !is_struct) {
1528                                 Report.Error (453, loc, "The type `{0}' must be a " +
1529                                               "non-nullable value 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                         }
1537
1538                         //
1539                         // The class constraint comes next.
1540                         //
1541                         if (gc.HasClassConstraint) {
1542                                 if (!CheckConstraint (ec, ptype, aexpr, gc.ClassConstraint))
1543                                         return false;
1544                         }
1545
1546                         //
1547                         // Now, check the interface constraints.
1548                         //
1549                         if (gc.InterfaceConstraints != null) {
1550                                 foreach (Type it in gc.InterfaceConstraints) {
1551                                         if (!CheckConstraint (ec, ptype, aexpr, it))
1552                                                 return false;
1553                                 }
1554                         }
1555
1556                         //
1557                         // Finally, check the constructor constraint.
1558                         //
1559
1560                         if (!gc.HasConstructorConstraint)
1561                                 return true;
1562
1563                         if (TypeManager.IsBuiltinType (atype) || atype.IsValueType)
1564                                 return true;
1565
1566                         if (HasDefaultConstructor (ec.DeclContainer.TypeBuilder, atype))
1567                                 return true;
1568
1569                         Report_SymbolRelatedToPreviousError ();
1570                         Report.SymbolRelatedToPreviousError (atype);
1571                         Report.Error (310, loc, "The type `{0}' must have a public " +
1572                                       "parameterless constructor in order to use it " +
1573                                       "as parameter `{1}' in the generic type or " +
1574                                       "method `{2}'",
1575                                       TypeManager.CSharpName (atype),
1576                                       TypeManager.CSharpName (ptype),
1577                                       GetSignatureForError ());
1578                         return false;
1579                 }
1580
1581                 protected bool CheckConstraint (IResolveContext ec, Type ptype, Expression expr,
1582                                                 Type ctype)
1583                 {
1584                         if (TypeManager.HasGenericArguments (ctype)) {
1585                                 Type[] types = TypeManager.GetTypeArguments (ctype);
1586
1587                                 TypeArguments new_args = new TypeArguments (loc);
1588
1589                                 for (int i = 0; i < types.Length; i++) {
1590                                         Type t = types [i];
1591
1592                                         if (t.IsGenericParameter) {
1593                                                 int pos = t.GenericParameterPosition;
1594                                                 t = atypes [pos];
1595                                         }
1596                                         new_args.Add (new TypeExpression (t, loc));
1597                                 }
1598
1599                                 TypeExpr ct = new ConstructedType (ctype, new_args, loc);
1600                                 if (ct.ResolveAsTypeStep (ec, false) == null)
1601                                         return false;
1602                                 ctype = ct.Type;
1603                         } else if (ctype.IsGenericParameter) {
1604                                 int pos = ctype.GenericParameterPosition;
1605                                 ctype = atypes [pos];
1606                         }
1607
1608                         if (Convert.ImplicitStandardConversionExists (expr, ctype))
1609                                 return true;
1610
1611                         Error_TypeMustBeConvertible (expr.Type, ctype, ptype);
1612                         return false;
1613                 }
1614
1615                 bool HasDefaultConstructor (Type containerType, Type atype)
1616                 {
1617                         if (atype.IsAbstract)
1618                                 return false;
1619
1620                 again:
1621                         atype = TypeManager.DropGenericTypeArguments (atype);
1622                         if (atype is TypeBuilder) {
1623                                 TypeContainer tc = TypeManager.LookupTypeContainer (atype);
1624                                 if (tc.InstanceConstructors == null) {
1625                                         atype = atype.BaseType;
1626                                         goto again;
1627                                 }
1628
1629                                 foreach (Constructor c in tc.InstanceConstructors) {
1630                                         if ((c.ModFlags & Modifiers.PUBLIC) == 0)
1631                                                 continue;
1632                                         if ((c.Parameters.FixedParameters != null) &&
1633                                             (c.Parameters.FixedParameters.Length != 0))
1634                                                 continue;
1635                                         if (c.Parameters.HasArglist || c.Parameters.HasParams)
1636                                                 continue;
1637
1638                                         return true;
1639                                 }
1640                         }
1641
1642                         TypeParameter tparam = TypeManager.LookupTypeParameter (atype);
1643                         if (tparam != null)
1644                                 return tparam.HasConstructorConstraint;
1645
1646                         MemberList list = TypeManager.FindMembers (
1647                                 atype, MemberTypes.Constructor,
1648                                 BindingFlags.Public | BindingFlags.Instance |
1649                                 BindingFlags.DeclaredOnly, null, null);
1650
1651                         if (atype.IsAbstract || (list == null))
1652                                 return false;
1653
1654                         foreach (MethodBase mb in list) {
1655                                 ParameterData pd = TypeManager.GetParameterData (mb);
1656                                 if ((pd.Count == 0) && mb.IsPublic && !mb.IsStatic)
1657                                         return true;
1658                         }
1659
1660                         return false;
1661                 }
1662
1663                 protected abstract string GetSignatureForError ();
1664                 protected abstract void Report_SymbolRelatedToPreviousError ();
1665
1666                 void Error_TypeMustBeConvertible (Type atype, Type gc, Type ptype)
1667                 {
1668                         Report_SymbolRelatedToPreviousError ();
1669                         Report.SymbolRelatedToPreviousError (atype);
1670                         Report.Error (309, loc,
1671                                       "The type `{0}' must be convertible to `{1}' in order to " +
1672                                       "use it as parameter `{2}' in the generic type or method `{3}'",
1673                                       TypeManager.CSharpName (atype), TypeManager.CSharpName (gc),
1674                                       TypeManager.CSharpName (ptype), GetSignatureForError ());
1675                 }
1676
1677                 public static bool CheckConstraints (EmitContext ec, MethodBase definition,
1678                                                      MethodBase instantiated, Location loc)
1679                 {
1680                         MethodConstraintChecker checker = new MethodConstraintChecker (
1681                                 definition, definition.GetGenericArguments (),
1682                                 instantiated.GetGenericArguments (), loc);
1683
1684                         return checker.CheckConstraints (ec);
1685                 }
1686
1687                 public static bool CheckConstraints (IResolveContext ec, Type gt, Type[] gen_params,
1688                                                      Type[] atypes, Location loc)
1689                 {
1690                         TypeConstraintChecker checker = new TypeConstraintChecker (
1691                                 gt, gen_params, atypes, loc);
1692
1693                         return checker.CheckConstraints (ec);
1694                 }
1695
1696                 protected class MethodConstraintChecker : ConstraintChecker
1697                 {
1698                         MethodBase definition;
1699
1700                         public MethodConstraintChecker (MethodBase definition, Type[] gen_params,
1701                                                         Type[] atypes, Location loc)
1702                                 : base (gen_params, atypes, loc)
1703                         {
1704                                 this.definition = definition;
1705                         }
1706
1707                         protected override string GetSignatureForError ()
1708                         {
1709                                 return TypeManager.CSharpSignature (definition);
1710                         }
1711
1712                         protected override void Report_SymbolRelatedToPreviousError ()
1713                         {
1714                                 Report.SymbolRelatedToPreviousError (definition);
1715                         }
1716                 }
1717
1718                 protected class TypeConstraintChecker : ConstraintChecker
1719                 {
1720                         Type gt;
1721
1722                         public TypeConstraintChecker (Type gt, Type[] gen_params, Type[] atypes,
1723                                                       Location loc)
1724                                 : base (gen_params, atypes, loc)
1725                         {
1726                                 this.gt = gt;
1727                         }
1728
1729                         protected override string GetSignatureForError ()
1730                         {
1731                                 return TypeManager.CSharpName (gt);
1732                         }
1733
1734                         protected override void Report_SymbolRelatedToPreviousError ()
1735                         {
1736                                 Report.SymbolRelatedToPreviousError (gt);
1737                         }
1738                 }
1739         }
1740
1741         /// <summary>
1742         ///   A generic method definition.
1743         /// </summary>
1744         public class GenericMethod : DeclSpace
1745         {
1746                 Expression return_type;
1747                 Parameters parameters;
1748
1749                 public GenericMethod (NamespaceEntry ns, DeclSpace parent, MemberName name,
1750                                       Expression return_type, Parameters parameters)
1751                         : base (ns, parent, name, null)
1752                 {
1753                         this.return_type = return_type;
1754                         this.parameters = parameters;
1755                 }
1756
1757                 public override TypeBuilder DefineType ()
1758                 {
1759                         throw new Exception ();
1760                 }
1761
1762                 public override bool Define ()
1763                 {
1764                         for (int i = 0; i < TypeParameters.Length; i++)
1765                                 if (!TypeParameters [i].Resolve (this))
1766                                         return false;
1767
1768                         return true;
1769                 }
1770
1771                 /// <summary>
1772                 ///   Define and resolve the type parameters.
1773                 ///   We're called from Method.Define().
1774                 /// </summary>
1775                 public bool Define (MethodBuilder mb, ToplevelBlock block)
1776                 {
1777                         TypeParameterName[] names = MemberName.TypeArguments.GetDeclarations ();
1778                         string[] snames = new string [names.Length];
1779                         for (int i = 0; i < names.Length; i++) {
1780                                 string type_argument_name = names[i].Name;
1781                                 Parameter p = parameters.GetParameterByName (type_argument_name);
1782                                 if (p != null) {
1783                                         Error_ParameterNameCollision (p.Location, type_argument_name, "method parameter");
1784                                         return false;
1785                                 }
1786                                 if (block != null) {
1787                                         LocalInfo li = (LocalInfo)block.Variables[type_argument_name];
1788                                         if (li != null) {
1789                                                 Error_ParameterNameCollision (li.Location, type_argument_name, "local variable");
1790                                                 return false;
1791                                         }
1792                                 }
1793                                 snames[i] = type_argument_name;
1794                         }
1795
1796                         GenericTypeParameterBuilder[] gen_params = mb.DefineGenericParameters (snames);
1797                         for (int i = 0; i < TypeParameters.Length; i++)
1798                                 TypeParameters [i].Define (gen_params [i]);
1799
1800                         if (!Define ())
1801                                 return false;
1802
1803                         for (int i = 0; i < TypeParameters.Length; i++) {
1804                                 if (!TypeParameters [i].ResolveType (this))
1805                                         return false;
1806                         }
1807
1808                         return true;
1809                 }
1810
1811                 static void Error_ParameterNameCollision (Location loc, string name, string collisionWith)
1812                 {
1813                         Report.Error (412, loc, "The type parameter name `{0}' is the same as `{1}'",
1814                                 name, collisionWith);
1815                 }
1816
1817                 /// <summary>
1818                 ///   We're called from MethodData.Define() after creating the MethodBuilder.
1819                 /// </summary>
1820                 public bool DefineType (EmitContext ec, MethodBuilder mb,
1821                                         MethodInfo implementing, bool is_override)
1822                 {
1823                         for (int i = 0; i < TypeParameters.Length; i++)
1824                                 if (!TypeParameters [i].DefineType (
1825                                             ec, mb, implementing, is_override))
1826                                         return false;
1827
1828                         bool ok = true;
1829                         foreach (Parameter p in parameters.FixedParameters){
1830                                 if (!p.Resolve (ec))
1831                                         ok = false;
1832                         }
1833                         if ((return_type != null) && (return_type.ResolveAsTypeTerminal (ec, false) == null))
1834                                 ok = false;
1835
1836                         return ok;
1837                 }
1838
1839                 public void EmitAttributes ()
1840                 {
1841                         for (int i = 0; i < TypeParameters.Length; i++)
1842                                 TypeParameters [i].EmitAttributes ();
1843
1844                         if (OptAttributes != null)
1845                                 OptAttributes.Emit ();
1846                 }
1847
1848                 public override bool DefineMembers ()
1849                 {
1850                         return true;
1851                 }
1852
1853                 public override MemberList FindMembers (MemberTypes mt, BindingFlags bf,
1854                                                         MemberFilter filter, object criteria)
1855                 {
1856                         throw new Exception ();
1857                 }
1858
1859                 public override MemberCache MemberCache {
1860                         get {
1861                                 return null;
1862                         }
1863                 }
1864
1865                 public override AttributeTargets AttributeTargets {
1866                         get {
1867                                 return AttributeTargets.Method | AttributeTargets.ReturnValue;
1868                         }
1869                 }
1870
1871                 public override string DocCommentHeader {
1872                         get { return "M:"; }
1873                 }
1874         }
1875
1876         public class DefaultValueExpression : Expression
1877         {
1878                 Expression expr;
1879
1880                 public DefaultValueExpression (Expression expr, Location loc)
1881                 {
1882                         this.expr = expr;
1883                         this.loc = loc;
1884                 }
1885
1886                 public override Expression DoResolve (EmitContext ec)
1887                 {
1888                         TypeExpr texpr = expr.ResolveAsTypeTerminal (ec, false);
1889                         if (texpr == null)
1890                                 return null;
1891
1892                         type = texpr.Type;
1893
1894                         eclass = ExprClass.Variable;
1895                         return this;
1896                 }
1897
1898                 public override void Emit (EmitContext ec)
1899                 {
1900                         if (type.IsGenericParameter || TypeManager.IsValueType (type)) {
1901                                 LocalTemporary temp_storage = new LocalTemporary (type);
1902
1903                                 temp_storage.AddressOf (ec, AddressOp.LoadStore);
1904                                 ec.ig.Emit (OpCodes.Initobj, type);
1905                                 temp_storage.Emit (ec);
1906                         } else
1907                                 ec.ig.Emit (OpCodes.Ldnull);
1908                 }
1909         }
1910
1911         public class NullableType : TypeExpr
1912         {
1913                 Expression underlying;
1914
1915                 public NullableType (Expression underlying, Location l)
1916                 {
1917                         this.underlying = underlying;
1918                         loc = l;
1919
1920                         eclass = ExprClass.Type;
1921                 }
1922
1923                 public NullableType (Type type, Location loc)
1924                         : this (new TypeExpression (type, loc), loc)
1925                 { }
1926
1927                 public override string Name {
1928                         get { return underlying.ToString () + "?"; }
1929                 }
1930
1931                 public override string FullName {
1932                         get { return underlying.ToString () + "?"; }
1933                 }
1934
1935                 protected override TypeExpr DoResolveAsTypeStep (IResolveContext ec)
1936                 {
1937                         TypeArguments args = new TypeArguments (loc);
1938                         args.Add (underlying);
1939
1940                         ConstructedType ctype = new ConstructedType (TypeManager.generic_nullable_type, args, loc);
1941                         return ctype.ResolveAsTypeTerminal (ec, false);
1942                 }
1943         }
1944
1945         public partial class TypeManager
1946         {
1947                 //
1948                 // A list of core types that the compiler requires or uses
1949                 //
1950                 static public Type activator_type;
1951                 static public Type generic_ilist_type;
1952                 static public Type generic_icollection_type;
1953                 static public Type generic_ienumerator_type;
1954                 static public Type generic_ienumerable_type;
1955                 static public Type generic_nullable_type;
1956
1957                 // <remarks>
1958                 //   Tracks the generic parameters.
1959                 // </remarks>
1960                 static PtrHashtable builder_to_type_param;
1961
1962                 //
1963                 // These methods are called by code generated by the compiler
1964                 //
1965                 static public MethodInfo activator_create_instance;
1966
1967                 static void InitGenerics ()
1968                 {
1969                         builder_to_type_param = new PtrHashtable ();
1970                 }
1971
1972                 static void CleanUpGenerics ()
1973                 {
1974                         builder_to_type_param = null;
1975                 }
1976
1977                 static void InitGenericCoreTypes ()
1978                 {
1979                         activator_type = CoreLookupType ("System", "Activator");
1980
1981                         generic_ilist_type = CoreLookupType (
1982                                 "System.Collections.Generic", "IList", 1);
1983                         generic_icollection_type = CoreLookupType (
1984                                 "System.Collections.Generic", "ICollection", 1);
1985                         generic_ienumerator_type = CoreLookupType (
1986                                 "System.Collections.Generic", "IEnumerator", 1);
1987                         generic_ienumerable_type = CoreLookupType (
1988                                 "System.Collections.Generic", "IEnumerable", 1);
1989                         generic_nullable_type = CoreLookupType (
1990                                 "System", "Nullable", 1);
1991                 }
1992
1993                 static void InitGenericCodeHelpers ()
1994                 {
1995                         // Activator
1996                         Type [] type_arg = { type_type };
1997                         activator_create_instance = GetMethod (
1998                                 activator_type, "CreateInstance", type_arg);
1999                 }
2000
2001                 static Type CoreLookupType (string ns, string name, int arity)
2002                 {
2003                         return CoreLookupType (ns, MemberName.MakeName (name, arity));
2004                 }
2005
2006                 public static void AddTypeParameter (Type t, TypeParameter tparam)
2007                 {
2008                         if (!builder_to_type_param.Contains (t))
2009                                 builder_to_type_param.Add (t, tparam);
2010                 }
2011
2012                 public static TypeContainer LookupGenericTypeContainer (Type t)
2013                 {
2014                         t = DropGenericTypeArguments (t);
2015                         return LookupTypeContainer (t);
2016                 }
2017
2018                 public static TypeParameter LookupTypeParameter (Type t)
2019                 {
2020                         return (TypeParameter) builder_to_type_param [t];
2021                 }
2022
2023                 public static GenericConstraints GetTypeParameterConstraints (Type t)
2024                 {
2025                         if (!t.IsGenericParameter)
2026                                 throw new InvalidOperationException ();
2027
2028                         TypeParameter tparam = LookupTypeParameter (t);
2029                         if (tparam != null)
2030                                 return tparam.GenericConstraints;
2031
2032                         return ReflectionConstraints.GetConstraints (t);
2033                 }
2034
2035                 public static bool HasGenericArguments (Type t)
2036                 {
2037                         return GetNumberOfTypeArguments (t) > 0;
2038                 }
2039
2040                 public static int GetNumberOfTypeArguments (Type t)
2041                 {
2042                         if (t.IsGenericParameter)
2043                                 return 0;
2044                         DeclSpace tc = LookupDeclSpace (t);
2045                         if (tc != null)
2046                                 return tc.IsGeneric ? tc.CountTypeParameters : 0;
2047                         else
2048                                 return t.IsGenericType ? t.GetGenericArguments ().Length : 0;
2049                 }
2050
2051                 public static Type[] GetTypeArguments (Type t)
2052                 {
2053                         DeclSpace tc = LookupDeclSpace (t);
2054                         if (tc != null) {
2055                                 if (!tc.IsGeneric)
2056                                         return Type.EmptyTypes;
2057
2058                                 TypeParameter[] tparam = tc.TypeParameters;
2059                                 Type[] ret = new Type [tparam.Length];
2060                                 for (int i = 0; i < tparam.Length; i++) {
2061                                         ret [i] = tparam [i].Type;
2062                                         if (ret [i] == null)
2063                                                 throw new InternalErrorException ();
2064                                 }
2065
2066                                 return ret;
2067                         } else
2068                                 return t.GetGenericArguments ();
2069                 }
2070
2071                 public static Type DropGenericTypeArguments (Type t)
2072                 {
2073                         if (!t.IsGenericType)
2074                                 return t;
2075                         // Micro-optimization: a generic typebuilder is always a generic type definition
2076                         if (t is TypeBuilder)
2077                                 return t;
2078                         return t.GetGenericTypeDefinition ();
2079                 }
2080
2081                 public static MethodBase DropGenericMethodArguments (MethodBase m)
2082                 {
2083                         if (m.IsGenericMethodDefinition)
2084                                 return m;
2085                         if (m.IsGenericMethod)
2086                                 return ((MethodInfo) m).GetGenericMethodDefinition ();
2087                         if (!m.DeclaringType.IsGenericType)
2088                                 return m;
2089
2090                         Type t = m.DeclaringType.GetGenericTypeDefinition ();
2091                         BindingFlags bf = BindingFlags.Public | BindingFlags.NonPublic |
2092                                 BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly;
2093
2094                         if (m is ConstructorInfo) {
2095                                 foreach (ConstructorInfo c in t.GetConstructors (bf))
2096                                         if (c.MetadataToken == m.MetadataToken)
2097                                                 return c;
2098                         } else {
2099                                 foreach (MethodBase mb in t.GetMethods (bf))
2100                                         if (mb.MetadataToken == m.MetadataToken)
2101                                                 return mb;
2102                         }
2103
2104                         return m;
2105                 }
2106
2107                 public static FieldInfo GetGenericFieldDefinition (FieldInfo fi)
2108                 {
2109                         if (fi.DeclaringType.IsGenericTypeDefinition ||
2110                             !fi.DeclaringType.IsGenericType)
2111                                 return fi;
2112
2113                         Type t = fi.DeclaringType.GetGenericTypeDefinition ();
2114                         BindingFlags bf = BindingFlags.Public | BindingFlags.NonPublic |
2115                                 BindingFlags.Static | BindingFlags.Instance | BindingFlags.DeclaredOnly;
2116
2117                         foreach (FieldInfo f in t.GetFields (bf))
2118                                 if (f.MetadataToken == fi.MetadataToken)
2119                                         return f;
2120
2121                         return fi;
2122                 }
2123
2124                 public static bool IsEqual (Type a, Type b)
2125                 {
2126                         if (a.Equals (b))
2127                                 return true;
2128
2129                         if (a.IsGenericParameter && b.IsGenericParameter) {
2130                                 if (a.DeclaringMethod != b.DeclaringMethod &&
2131                                     (a.DeclaringMethod == null || b.DeclaringMethod == null))
2132                                         return false;
2133                                 return a.GenericParameterPosition == b.GenericParameterPosition;
2134                         }
2135
2136                         if (a.IsArray && b.IsArray) {
2137                                 if (a.GetArrayRank () != b.GetArrayRank ())
2138                                         return false;
2139                                 return IsEqual (a.GetElementType (), b.GetElementType ());
2140                         }
2141
2142                         if (a.IsByRef && b.IsByRef)
2143                                 return IsEqual (a.GetElementType (), b.GetElementType ());
2144
2145                         if (a.IsGenericType && b.IsGenericType) {
2146                                 if (a.GetGenericTypeDefinition () != b.GetGenericTypeDefinition ())
2147                                         return false;
2148
2149                                 Type[] aargs = a.GetGenericArguments ();
2150                                 Type[] bargs = b.GetGenericArguments ();
2151
2152                                 if (aargs.Length != bargs.Length)
2153                                         return false;
2154
2155                                 for (int i = 0; i < aargs.Length; i++) {
2156                                         if (!IsEqual (aargs [i], bargs [i]))
2157                                                 return false;
2158                                 }
2159
2160                                 return true;
2161                         }
2162
2163                         //
2164                         // This is to build with the broken circular dependencies between
2165                         // System and System.Configuration in the 2.x profile where we
2166                         // end up with a situation where:
2167                         //
2168                         // System on the second build is referencing the System.Configuration
2169                         // that has references to the first System build.
2170                         //
2171                         // Point in case: NameValueCollection built on the first pass, vs
2172                         // NameValueCollection build on the second one.  The problem is that
2173                         // we need to override some methods sometimes, or we need to
2174                         //
2175                         if (RootContext.BrokenCircularDeps){
2176                                 if (a.Name == b.Name && a.Namespace == b.Namespace){
2177                                         Console.WriteLine ("GonziMatch: {0}.{1}", a.Namespace, a.Name);
2178                                         return true;
2179                                 }
2180                         }
2181                         return false;
2182                 }
2183
2184                 /// <summary>
2185                 ///   Check whether `a' and `b' may become equal generic types.
2186                 ///   The algorithm to do that is a little bit complicated.
2187                 /// </summary>
2188                 public static bool MayBecomeEqualGenericTypes (Type a, Type b, Type[] class_infered,
2189                                                                Type[] method_infered)
2190                 {
2191                         if (a.IsGenericParameter) {
2192                                 //
2193                                 // If a is an array of a's type, they may never
2194                                 // become equal.
2195                                 //
2196                                 while (b.IsArray) {
2197                                         b = b.GetElementType ();
2198                                         if (a.Equals (b))
2199                                                 return false;
2200                                 }
2201
2202                                 //
2203                                 // If b is a generic parameter or an actual type,
2204                                 // they may become equal:
2205                                 //
2206                                 //    class X<T,U> : I<T>, I<U>
2207                                 //    class X<T> : I<T>, I<float>
2208                                 //
2209                                 if (b.IsGenericParameter || !b.IsGenericType) {
2210                                         int pos = a.GenericParameterPosition;
2211                                         Type[] args = a.DeclaringMethod != null ? method_infered : class_infered;
2212                                         if (args [pos] == null) {
2213                                                 args [pos] = b;
2214                                                 return true;
2215                                         }
2216
2217                                         return args [pos] == a;
2218                                 }
2219
2220                                 //
2221                                 // We're now comparing a type parameter with a
2222                                 // generic instance.  They may become equal unless
2223                                 // the type parameter appears anywhere in the
2224                                 // generic instance:
2225                                 //
2226                                 //    class X<T,U> : I<T>, I<X<U>>
2227                                 //        -> error because you could instanciate it as
2228                                 //           X<X<int>,int>
2229                                 //
2230                                 //    class X<T> : I<T>, I<X<T>> -> ok
2231                                 //
2232
2233                                 Type[] bargs = GetTypeArguments (b);
2234                                 for (int i = 0; i < bargs.Length; i++) {
2235                                         if (a.Equals (bargs [i]))
2236                                                 return false;
2237                                 }
2238
2239                                 return true;
2240                         }
2241
2242                         if (b.IsGenericParameter)
2243                                 return MayBecomeEqualGenericTypes (b, a, class_infered, method_infered);
2244
2245                         //
2246                         // At this point, neither a nor b are a type parameter.
2247                         //
2248                         // If one of them is a generic instance, let
2249                         // MayBecomeEqualGenericInstances() compare them (if the
2250                         // other one is not a generic instance, they can never
2251                         // become equal).
2252                         //
2253
2254                         if (a.IsGenericType || b.IsGenericType)
2255                                 return MayBecomeEqualGenericInstances (a, b, class_infered, method_infered);
2256
2257                         //
2258                         // If both of them are arrays.
2259                         //
2260
2261                         if (a.IsArray && b.IsArray) {
2262                                 if (a.GetArrayRank () != b.GetArrayRank ())
2263                                         return false;
2264
2265                                 a = a.GetElementType ();
2266                                 b = b.GetElementType ();
2267
2268                                 return MayBecomeEqualGenericTypes (a, b, class_infered, method_infered);
2269                         }
2270
2271                         //
2272                         // Ok, two ordinary types.
2273                         //
2274
2275                         return a.Equals (b);
2276                 }
2277
2278                 //
2279                 // Checks whether two generic instances may become equal for some
2280                 // particular instantiation (26.3.1).
2281                 //
2282                 public static bool MayBecomeEqualGenericInstances (Type a, Type b,
2283                                                                    Type[] class_infered,
2284                                                                    Type[] method_infered)
2285                 {
2286                         if (!a.IsGenericType || !b.IsGenericType)
2287                                 return false;
2288                         if (a.GetGenericTypeDefinition () != b.GetGenericTypeDefinition ())
2289                                 return false;
2290
2291                         return MayBecomeEqualGenericInstances (
2292                                 GetTypeArguments (a), GetTypeArguments (b), class_infered, method_infered);
2293                 }
2294
2295                 public static bool MayBecomeEqualGenericInstances (Type[] aargs, Type[] bargs,
2296                                                                    Type[] class_infered,
2297                                                                    Type[] method_infered)
2298                 {
2299                         if (aargs.Length != bargs.Length)
2300                                 return false;
2301
2302                         for (int i = 0; i < aargs.Length; i++) {
2303                                 if (!MayBecomeEqualGenericTypes (aargs [i], bargs [i], class_infered, method_infered))
2304                                         return false;
2305                         }
2306
2307                         return true;
2308                 }
2309
2310                 /// <summary>
2311                 ///   Check whether `type' and `parent' are both instantiations of the same
2312                 ///   generic type.  Note that we do not check the type parameters here.
2313                 /// </summary>
2314                 public static bool IsInstantiationOfSameGenericType (Type type, Type parent)
2315                 {
2316                         int tcount = GetNumberOfTypeArguments (type);
2317                         int pcount = GetNumberOfTypeArguments (parent);
2318
2319                         if (tcount != pcount)
2320                                 return false;
2321
2322                         type = DropGenericTypeArguments (type);
2323                         parent = DropGenericTypeArguments (parent);
2324
2325                         return type.Equals (parent);
2326                 }
2327
2328                 /// <summary>
2329                 ///   Whether `mb' is a generic method definition.
2330                 /// </summary>
2331                 public static bool IsGenericMethodDefinition (MethodBase mb)
2332                 {
2333                         if (mb.DeclaringType is TypeBuilder) {
2334                                 IMethodData method = (IMethodData) builder_to_method [mb];
2335                                 if (method == null)
2336                                         return false;
2337
2338                                 return method.GenericMethod != null;
2339                         }
2340
2341                         return mb.IsGenericMethodDefinition;
2342                 }
2343
2344                 /// <summary>
2345                 ///   Whether `mb' is a generic method definition.
2346                 /// </summary>
2347                 public static bool IsGenericMethod (MethodBase mb)
2348                 {
2349                         if (mb.DeclaringType is TypeBuilder) {
2350                                 IMethodData method = (IMethodData) builder_to_method [mb];
2351                                 if (method == null)
2352                                         return false;
2353
2354                                 return method.GenericMethod != null;
2355                         }
2356
2357                         return mb.IsGenericMethod;
2358                 }
2359
2360                 //
2361                 // Type inference.
2362                 //
2363
2364                 static bool InferType (Type pt, Type at, Type[] infered)
2365                 {
2366                         if (pt.IsGenericParameter) {
2367                                 if (pt.DeclaringMethod == null)
2368                                         return pt == at;
2369
2370                                 int pos = pt.GenericParameterPosition;
2371
2372                                 if (infered [pos] == null) {
2373                                         infered [pos] = at;
2374                                         return true;
2375                                 }
2376
2377                                 if (infered [pos] != at)
2378                                         return false;
2379
2380                                 return true;
2381                         }
2382
2383                         if (!pt.ContainsGenericParameters) {
2384                                 if (at.ContainsGenericParameters)
2385                                         return InferType (at, pt, infered);
2386                                 else
2387                                         return true;
2388                         }
2389
2390                         if (at.IsArray) {
2391                                 if (pt.IsArray) {
2392                                         if (at.GetArrayRank () != pt.GetArrayRank ())
2393                                                 return false;
2394
2395                                         return InferType (pt.GetElementType (), at.GetElementType (), infered);
2396                                 }
2397
2398                                 if (!pt.IsGenericType)
2399                                         return false;
2400
2401                                 Type gt = pt.GetGenericTypeDefinition ();
2402                                 if ((gt != generic_ilist_type) && (gt != generic_icollection_type) &&
2403                                     (gt != 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 AnonymousMethodExpression))
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 }