mcs/gmcs/generic.cs

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