mcs/mcs/ecore.cs

   1 //
   2 // ecore.cs: Core of the Expression representation for the intermediate tree.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // (C) 2001 Ximian, Inc.
   8 //
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17         using System.Text;
  18
  19         /// <remarks>
  20         ///   The ExprClass class contains the is used to pass the
  21         ///   classification of an expression (value, variable, namespace,
  22         ///   type, method group, property access, event access, indexer access,
  23         ///   nothing).
  24         /// </remarks>
  25         public enum ExprClass : byte {
  26                 Invalid,
  27
  28                 Value,
  29                 Variable,
  30                 Namespace,
  31                 Type,
  32                 MethodGroup,
  33                 PropertyAccess,
  34                 EventAccess,
  35                 IndexerAccess,
  36                 Nothing,
  37         }
  38
  39         /// <summary>
  40         ///   This interface is implemented by variables
  41         /// </summary>
  42         public interface IMemoryLocation {
  43                 /// <summary>
  44                 ///   The AddressOf method should generate code that loads
  45                 ///   the address of the object and leaves it on the stack
  46                 /// </summary>
  47                 void AddressOf (EmitContext ec);
  48         }
  49
  50         /// <remarks>
  51         ///   Base class for expressions
  52         /// </remarks>
  53         public abstract class Expression {
  54                 protected ExprClass eclass;
  55                 protected Type      type;
  56
  57                 public Type Type {
  58                         get {
  59                                 return type;
  60                         }
  61
  62                         set {
  63                                 type = value;
  64                         }
  65                 }
  66
  67                 public ExprClass ExprClass {
  68                         get {
  69                                 return eclass;
  70                         }
  71
  72                         set {
  73                                 eclass = value;
  74                         }
  75                 }
  76
  77                 /// <summary>
  78                 ///   Utility wrapper routine for Error, just to beautify the code
  79                 /// </summary>
  80                 static protected void Error (int error, string s)
  81                 {
  82                         Report.Error (error, s);
  83                 }
  84
  85                 static protected void Error (int error, Location loc, string s)
  86                 {
  87                         Report.Error (error, loc, s);
  88                 }
  89
  90                 /// <summary>
  91                 ///   Utility wrapper routine for Warning, just to beautify the code
  92                 /// </summary>
  93                 static protected void Warning (int warning, string s)
  94                 {
  95                         Report.Warning (warning, s);
  96                 }
  97
  98                 static public void error30 (Location loc, Type source, Type target)
  99                 {
 100                         Report.Error (30, loc, "Cannot convert type '" +
 101                                       TypeManager.CSharpName (source) + "' to '" +
 102                                       TypeManager.CSharpName (target) + "'");
 103                 }
 104
 105                 /// <summary>
 106                 ///   Performs semantic analysis on the Expression
 107                 /// </summary>
 108                 ///
 109                 /// <remarks>
 110                 ///   The Resolve method is invoked to perform the semantic analysis
 111                 ///   on the node.
 112                 ///
 113                 ///   The return value is an expression (it can be the
 114                 ///   same expression in some cases) or a new
 115                 ///   expression that better represents this node.
 116                 ///
 117                 ///   For example, optimizations of Unary (LiteralInt)
 118                 ///   would return a new LiteralInt with a negated
 119                 ///   value.
 120                 ///
 121                 ///   If there is an error during semantic analysis,
 122                 ///   then an error should be reported (using Report)
 123                 ///   and a null value should be returned.
 124                 ///
 125                 ///   There are two side effects expected from calling
 126                 ///   Resolve(): the the field variable "eclass" should
 127                 ///   be set to any value of the enumeration
 128                 ///   `ExprClass' and the type variable should be set
 129                 ///   to a valid type (this is the type of the
 130                 ///   expression).
 131                 /// </remarks>
 132                 public abstract Expression DoResolve (EmitContext ec);
 133
 134                 public virtual Expression DoResolveLValue (EmitContext ec, Expression right_side)
 135                 {
 136                         return DoResolve (ec);
 137                 }
 138
 139                 /// <summary>
 140                 ///   Resolves an expression and performs semantic analysis on it.
 141                 /// </summary>
 142                 ///
 143                 /// <remarks>
 144                 ///   Currently Resolve wraps DoResolve to perform sanity
 145                 ///   checking and assertion checking on what we expect from Resolve.
 146                 /// </remarks>
 147                 public Expression Resolve (EmitContext ec)
 148                 {
 149                         Expression e = DoResolve (ec);
 150
 151                         if (e != null){
 152                                 if (e is SimpleName){
 153                                         SimpleName s = (SimpleName) e;
 154
 155                                         Report.Error (
 156                                                 103, s.Location,
 157                                                 "The name `" + s.Name + "' could not be found in `" +
 158                                                 ec.TypeContainer.Name + "'");
 159                                         return null;
 160                                 }
 161
 162                                 if (e.ExprClass == ExprClass.Invalid)
 163                                         throw new Exception ("Expression " + e +
 164                                                              " ExprClass is Invalid after resolve");
 165
 166                                 if (e.ExprClass != ExprClass.MethodGroup)
 167                                         if (e.type == null)
 168                                                 throw new Exception ("Expression " + e +
 169                                                                      " did not set its type after Resolve");
 170                         }
 171
 172                         return e;
 173                 }
 174
 175                 /// <summary>
 176                 ///   Performs expression resolution and semantic analysis, but
 177                 ///   allows SimpleNames to be returned.
 178                 /// </summary>
 179                 ///
 180                 /// <remarks>
 181                 ///   This is used by MemberAccess to construct long names that can not be
 182                 ///   partially resolved (namespace-qualified names for example).
 183                 /// </remarks>
 184                 public Expression ResolveWithSimpleName (EmitContext ec)
 185                 {
 186                         Expression e = DoResolve (ec);
 187
 188                         if (e != null){
 189                                 if (e is SimpleName)
 190                                         return e;
 191
 192                                 if (e.ExprClass == ExprClass.Invalid)
 193                                         throw new Exception ("Expression " + e +
 194                                                              " ExprClass is Invalid after resolve");
 195
 196                                 if (e.ExprClass != ExprClass.MethodGroup)
 197                                         if (e.type == null)
 198                                                 throw new Exception ("Expression " + e +
 199                                                                      " did not set its type after Resolve");
 200                         }
 201
 202                         return e;
 203                 }
 204
 205                 /// <summary>
 206                 ///   Resolves an expression for LValue assignment
 207                 /// </summary>
 208                 ///
 209                 /// <remarks>
 210                 ///   Currently ResolveLValue wraps DoResolveLValue to perform sanity
 211                 ///   checking and assertion checking on what we expect from Resolve
 212                 /// </remarks>
 213                 public Expression ResolveLValue (EmitContext ec, Expression right_side)
 214                 {
 215                         Expression e = DoResolveLValue (ec, right_side);
 216
 217                         if (e != null){
 218                                 if (e is SimpleName){
 219                                         SimpleName s = (SimpleName) e;
 220
 221                                         Report.Error (
 222                                                 103, s.Location,
 223                                                 "The name `" + s.Name + "' could not be found in `" +
 224                                                 ec.TypeContainer.Name + "'");
 225                                         return null;
 226                                 }
 227
 228                                 if (e.ExprClass == ExprClass.Invalid)
 229                                         throw new Exception ("Expression " + e +
 230                                                              " ExprClass is Invalid after resolve");
 231
 232                                 if (e.ExprClass != ExprClass.MethodGroup)
 233                                         if (e.type == null)
 234                                                 throw new Exception ("Expression " + e +
 235                                                                      " did not set its type after Resolve");
 236                         }
 237
 238                         return e;
 239                 }
 240
 241                 /// <summary>
 242                 ///   Emits the code for the expression
 243                 /// </summary>
 244                 ///
 245                 /// <remarks>
 246                 ///   The Emit method is invoked to generate the code
 247                 ///   for the expression.
 248                 /// </remarks>
 249                 public abstract void Emit (EmitContext ec);
 250
 251                 /// <summary>
 252                 ///   This method should perform a reduction of the expression.  This should
 253                 ///   never return null.
 254                 /// </summary>
 255                 public virtual Expression Reduce (EmitContext ec)
 256                 {
 257                         return this;
 258                 }
 259
 260                 /// <summary>
 261                 ///   Protected constructor.  Only derivate types should
 262                 ///   be able to be created
 263                 /// </summary>
 264
 265                 protected Expression ()
 266                 {
 267                         eclass = ExprClass.Invalid;
 268                         type = null;
 269                 }
 270
 271                 /// <summary>
 272                 ///   Returns a literalized version of a literal FieldInfo
 273                 /// </summary>
 274                 public static Expression Literalize (object v, Type t)
 275                 {
 276                         if (t == TypeManager.int32_type)
 277                                 return new IntLiteral ((int) v);
 278                         else if (t == TypeManager.uint32_type)
 279                                 return new UIntLiteral ((uint) v);
 280                         else if (t == TypeManager.int64_type)
 281                                 return new LongLiteral ((long) v);
 282                         else if (t == TypeManager.uint64_type)
 283                                 return new ULongLiteral ((ulong) v);
 284                         else if (t == TypeManager.float_type)
 285                                 return new FloatLiteral ((float) v);
 286                         else if (t == TypeManager.double_type)
 287                                 return new DoubleLiteral ((double) v);
 288                         else if (t == TypeManager.string_type)
 289                                 return new StringLiteral ((string) v);
 290                         else if (t == TypeManager.short_type)
 291                                 return new IntLiteral ((int) ((short)v));
 292                         else if (t == TypeManager.ushort_type)
 293                                 return new IntLiteral ((int) ((ushort)v));
 294                         else if (t == TypeManager.sbyte_type)
 295                                 return new IntLiteral ((int) ((sbyte)v));
 296                         else if (t == TypeManager.byte_type)
 297                                 return new IntLiteral ((int) ((byte)v));
 298                         else if (t == TypeManager.char_type)
 299                                 return new IntLiteral ((int) ((char)v));
 300                         else
 301                                 throw new Exception ("Unknown type for literal (" + t +
 302                                                      "), details: " + v);
 303                 }
 304
 305                 /// <summary>
 306                 ///   Returns a fully formed expression after a MemberLookup
 307                 /// </summary>
 308                 static Expression ExprClassFromMemberInfo (EmitContext ec, MemberInfo mi, Location loc)
 309                 {
 310                         if (mi is EventInfo)
 311                                 return new EventExpr ((EventInfo) mi, loc);
 312                         else if (mi is FieldInfo)
 313                                 return new FieldExpr ((FieldInfo) mi, loc);
 314                         else if (mi is PropertyInfo)
 315                                 return new PropertyExpr ((PropertyInfo) mi, loc);
 316                         else if (mi is Type)
 317                                 return new TypeExpr ((Type) mi);
 318
 319                         return null;
 320                 }
 321
 322                 //
 323                 // FIXME: Probably implement a cache for (t,name,current_access_set)?
 324                 //
 325                 // FIXME: We need to cope with access permissions here, or this wont
 326                 // work!
 327                 //
 328                 // This code could use some optimizations, but we need to do some
 329                 // measurements.  For example, we could use a delegate to `flag' when
 330                 // something can not any longer be a method-group (because it is something
 331                 // else).
 332                 //
 333                 // Return values:
 334                 //     If the return value is an Array, then it is an array of
 335                 //     MethodBases
 336                 //
 337                 //     If the return value is an MemberInfo, it is anything, but a Method
 338                 //
 339                 //     null on error.
 340                 //
 341                 // FIXME: When calling MemberLookup inside an `Invocation', we should pass
 342                 // the arguments here and have MemberLookup return only the methods that
 343                 // match the argument count/type, unlike we are doing now (we delay this
 344                 // decision).
 345                 //
 346                 // This is so we can catch correctly attempts to invoke instance methods
 347                 // from a static body (scan for error 120 in ResolveSimpleName).
 348                 //
 349                 public static Expression MemberLookup (EmitContext ec, Type t, string name,
 350                                                        bool same_type, MemberTypes mt,
 351                                                        BindingFlags bf, Location loc)
 352                 {
 353                         if (same_type)
 354                                 bf |= BindingFlags.NonPublic;
 355
 356                         MemberInfo [] mi = ec.TypeContainer.RootContext.TypeManager.FindMembers (
 357                                 t, mt, bf, Type.FilterName, name);
 358
 359                         if (mi == null)
 360                                 return null;
 361
 362                         // Empty array ...
 363                         if (mi.Length == 0)
 364                                 return null;
 365
 366
 367                         if (mi.Length == 1 && !(mi [0] is MethodBase))
 368                                 return Expression.ExprClassFromMemberInfo (ec, mi [0], loc);
 369
 370                         for (int i = 0; i < mi.Length; i++)
 371                                 if (!(mi [i] is MethodBase)){
 372                                         Error (-5, "Do not know how to reproduce this case: " +
 373                                                "Methods and non-Method with the same name, " +
 374                                                "report this please");
 375
 376                                         for (i = 0; i < mi.Length; i++){
 377                                                 Type tt = mi [i].GetType ();
 378
 379                                                 Console.WriteLine (i + ": " + mi [i]);
 380                                                 while (tt != TypeManager.object_type){
 381                                                         Console.WriteLine (tt);
 382                                                         tt = tt.BaseType;
 383                                                 }
 384                                         }
 385                                 }
 386
 387                         return new MethodGroupExpr (mi);
 388                 }
 389
 390                 public const MemberTypes AllMemberTypes =
 391                         MemberTypes.Constructor |
 392                         MemberTypes.Event       |
 393                         MemberTypes.Field       |
 394                         MemberTypes.Method      |
 395                         MemberTypes.NestedType  |
 396                         MemberTypes.Property;
 397
 398                 public const BindingFlags AllBindingsFlags =
 399                         BindingFlags.Public |
 400                         BindingFlags.Static |
 401                         BindingFlags.Instance;
 402
 403                 public static Expression MemberLookup (EmitContext ec, Type t, string name,
 404                                                        bool same_type, Location loc)
 405                 {
 406                         return MemberLookup (ec, t, name, same_type, AllMemberTypes, AllBindingsFlags, loc);
 407                 }
 408
 409                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
 410                 {
 411                         Type expr_type = expr.Type;
 412
 413                         if (target_type == TypeManager.object_type) {
 414                                 if (expr_type.IsClass)
 415                                         return new EmptyCast (expr, target_type);
 416                                 if (expr_type.IsValueType)
 417                                         return new BoxedCast (expr);
 418                         } else if (expr_type.IsSubclassOf (target_type)) {
 419                                 return new EmptyCast (expr, target_type);
 420                         } else {
 421                                 // from any class-type S to any interface-type T.
 422                                 if (expr_type.IsClass && target_type.IsInterface) {
 423
 424                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 425                                                 return new EmptyCast (expr, target_type);
 426                                         else
 427                                                 return null;
 428                                 }
 429
 430                                 // from any interface type S to interface-type T.
 431                                 if (expr_type.IsInterface && target_type.IsInterface) {
 432
 433                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 434                                                 return new EmptyCast (expr, target_type);
 435                                         else
 436                                                 return null;
 437                                 }
 438
 439                                 // from an array-type S to an array-type of type T
 440                                 if (expr_type.IsArray && target_type.IsArray) {
 441                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 442
 443                                                 Type expr_element_type = expr_type.GetElementType ();
 444                                                 Type target_element_type = target_type.GetElementType ();
 445
 446                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 447                                                         if (StandardConversionExists (expr_element_type,
 448                                                                                       target_element_type))
 449                                                                 return new EmptyCast (expr, target_type);
 450                                         }
 451                                 }
 452
 453
 454                                 // from an array-type to System.Array
 455                                 if (expr_type.IsArray && target_type == TypeManager.array_type)
 456                                         return new EmptyCast (expr, target_type);
 457
 458                                 // from any delegate type to System.Delegate
 459                                 if (expr_type.IsSubclassOf (TypeManager.delegate_type) &&
 460                                     target_type == TypeManager.delegate_type)
 461                                         return new EmptyCast (expr, target_type);
 462
 463                                 // from any array-type or delegate type into System.ICloneable.
 464                                 if (expr_type.IsArray || expr_type.IsSubclassOf (TypeManager.delegate_type))
 465                                         if (target_type == TypeManager.icloneable_type)
 466                                                 return new EmptyCast (expr, target_type);
 467
 468                                 // from the null type to any reference-type.
 469                                 if (expr is NullLiteral)
 470                                         return new EmptyCast (expr, target_type);
 471
 472                                 return null;
 473
 474                         }
 475
 476                         return null;
 477                 }
 478
 479                 /// <summary>
 480                 ///   Handles expressions like this: decimal d; d = 1;
 481                 ///   and changes them into: decimal d; d = new System.Decimal (1);
 482                 /// </summary>
 483                 static Expression InternalTypeConstructor (EmitContext ec, Expression expr, Type target)
 484                 {
 485                         ArrayList args = new ArrayList ();
 486
 487                         args.Add (new Argument (expr, Argument.AType.Expression));
 488
 489                         Expression ne = new New (target.FullName, args,
 490                                                  new Location (-1));
 491
 492                         return ne.Resolve (ec);
 493                 }
 494
 495                 /// <summary>
 496                 ///   Implicit Numeric Conversions.
 497                 ///
 498                 ///   expr is the expression to convert, returns a new expression of type
 499                 ///   target_type or null if an implicit conversion is not possible.
 500                 /// </summary>
 501                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 502                                                                     Type target_type, Location loc)
 503                 {
 504                         Type expr_type = expr.Type;
 505
 506                         //
 507                         // Attempt to do the implicit constant expression conversions
 508
 509                         if (expr is IntLiteral){
 510                                 Expression e;
 511
 512                                 e = TryImplicitIntConversion (target_type, (IntLiteral) expr);
 513
 514                                 if (e != null)
 515                                         return e;
 516                         } else if (expr is LongLiteral && target_type == TypeManager.uint64_type){
 517                                 //
 518                                 // Try the implicit constant expression conversion
 519                                 // from long to ulong, instead of a nice routine,
 520                                 // we just inline it
 521                                 //
 522                                 if (((LongLiteral) expr).Value > 0)
 523                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 524                         }
 525
 526                         if (expr_type == TypeManager.sbyte_type){
 527                                 //
 528                                 // From sbyte to short, int, long, float, double.
 529                                 //
 530                                 if (target_type == TypeManager.int32_type)
 531                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 532                                 if (target_type == TypeManager.int64_type)
 533                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 534                                 if (target_type == TypeManager.double_type)
 535                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 536                                 if (target_type == TypeManager.float_type)
 537                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 538                                 if (target_type == TypeManager.short_type)
 539                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 540                                 if (target_type == TypeManager.decimal_type)
 541                                         return InternalTypeConstructor (ec, expr, target_type);
 542                         } else if (expr_type == TypeManager.byte_type){
 543                                 //
 544                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 545                                 //
 546                                 if ((target_type == TypeManager.short_type) ||
 547                                     (target_type == TypeManager.ushort_type) ||
 548                                     (target_type == TypeManager.int32_type) ||
 549                                     (target_type == TypeManager.uint32_type))
 550                                         return new EmptyCast (expr, target_type);
 551
 552                                 if (target_type == TypeManager.uint64_type)
 553                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 554                                 if (target_type == TypeManager.int64_type)
 555                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 556
 557                                 if (target_type == TypeManager.float_type)
 558                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 559                                 if (target_type == TypeManager.double_type)
 560                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 561                                 if (target_type == TypeManager.decimal_type)
 562                                         return InternalTypeConstructor (ec, expr, target_type);
 563                         } else if (expr_type == TypeManager.short_type){
 564                                 //
 565                                 // From short to int, long, float, double
 566                                 //
 567                                 if (target_type == TypeManager.int32_type)
 568                                         return new EmptyCast (expr, target_type);
 569                                 if (target_type == TypeManager.int64_type)
 570                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 571                                 if (target_type == TypeManager.double_type)
 572                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 573                                 if (target_type == TypeManager.float_type)
 574                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 575                                 if (target_type == TypeManager.decimal_type)
 576                                         return InternalTypeConstructor (ec, expr, target_type);
 577                         } else if (expr_type == TypeManager.ushort_type){
 578                                 //
 579                                 // From ushort to int, uint, long, ulong, float, double
 580                                 //
 581                                 if (target_type == TypeManager.uint32_type)
 582                                         return new EmptyCast (expr, target_type);
 583
 584                                 if (target_type == TypeManager.uint64_type)
 585                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 586                                 if (target_type == TypeManager.int32_type)
 587                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 588                                 if (target_type == TypeManager.int64_type)
 589                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 590                                 if (target_type == TypeManager.double_type)
 591                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 592                                 if (target_type == TypeManager.float_type)
 593                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 594                                 if (target_type == TypeManager.decimal_type)
 595                                         return InternalTypeConstructor (ec, expr, target_type);
 596                         } else if (expr_type == TypeManager.int32_type){
 597                                 //
 598                                 // From int to long, float, double
 599                                 //
 600                                 if (target_type == TypeManager.int64_type)
 601                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 602                                 if (target_type == TypeManager.double_type)
 603                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 604                                 if (target_type == TypeManager.float_type)
 605                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 606                                 if (target_type == TypeManager.decimal_type)
 607                                         return InternalTypeConstructor (ec, expr, target_type);
 608                         } else if (expr_type == TypeManager.uint32_type){
 609                                 //
 610                                 // From uint to long, ulong, float, double
 611                                 //
 612                                 if (target_type == TypeManager.int64_type)
 613                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 614                                 if (target_type == TypeManager.uint64_type)
 615                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 616                                 if (target_type == TypeManager.double_type)
 617                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 618                                                                OpCodes.Conv_R8);
 619                                 if (target_type == TypeManager.float_type)
 620                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 621                                                                OpCodes.Conv_R4);
 622                                 if (target_type == TypeManager.decimal_type)
 623                                         return InternalTypeConstructor (ec, expr, target_type);
 624                         } else if ((expr_type == TypeManager.uint64_type) ||
 625                                    (expr_type == TypeManager.int64_type)){
 626                                 //
 627                                 // From long/ulong to float, double
 628                                 //
 629                                 if (target_type == TypeManager.double_type)
 630                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 631                                                                OpCodes.Conv_R8);
 632                                 if (target_type == TypeManager.float_type)
 633                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 634                                                                OpCodes.Conv_R4);
 635                                 if (target_type == TypeManager.decimal_type)
 636                                         return InternalTypeConstructor (ec, expr, target_type);
 637                         } else if (expr_type == TypeManager.char_type){
 638                                 //
 639                                 // From char to ushort, int, uint, long, ulong, float, double
 640                                 //
 641                                 if ((target_type == TypeManager.ushort_type) ||
 642                                     (target_type == TypeManager.int32_type) ||
 643                                     (target_type == TypeManager.uint32_type))
 644                                         return new EmptyCast (expr, target_type);
 645                                 if (target_type == TypeManager.uint64_type)
 646                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 647                                 if (target_type == TypeManager.int64_type)
 648                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 649                                 if (target_type == TypeManager.float_type)
 650                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 651                                 if (target_type == TypeManager.double_type)
 652                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 653                                 if (target_type == TypeManager.decimal_type)
 654                                         return InternalTypeConstructor (ec, expr, target_type);
 655                         } else if (expr_type == TypeManager.float_type){
 656                                 //
 657                                 // float to double
 658                                 //
 659                                 if (target_type == TypeManager.double_type)
 660                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 661                         }
 662
 663                         return null;
 664                 }
 665
 666                 /// <summary>
 667                 ///  Determines if a standard implicit conversion exists from
 668                 ///  expr_type to target_type
 669                 /// </summary>
 670                 public static bool StandardConversionExists (Type expr_type, Type target_type)
 671                 {
 672                         if (expr_type == target_type)
 673                                 return true;
 674
 675                         // First numeric conversions
 676
 677                         if (expr_type == TypeManager.sbyte_type){
 678                                 //
 679                                 // From sbyte to short, int, long, float, double.
 680                                 //
 681                                 if ((target_type == TypeManager.int32_type) ||
 682                                     (target_type == TypeManager.int64_type) ||
 683                                     (target_type == TypeManager.double_type) ||
 684                                     (target_type == TypeManager.float_type)  ||
 685                                     (target_type == TypeManager.short_type) ||
 686                                     (target_type == TypeManager.decimal_type))
 687                                         return true;
 688
 689                         } else if (expr_type == TypeManager.byte_type){
 690                                 //
 691                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 692                                 //
 693                                 if ((target_type == TypeManager.short_type) ||
 694                                     (target_type == TypeManager.ushort_type) ||
 695                                     (target_type == TypeManager.int32_type) ||
 696                                     (target_type == TypeManager.uint32_type) ||
 697                                     (target_type == TypeManager.uint64_type) ||
 698                                     (target_type == TypeManager.int64_type) ||
 699                                     (target_type == TypeManager.float_type) ||
 700                                     (target_type == TypeManager.double_type) ||
 701                                     (target_type == TypeManager.decimal_type))
 702                                         return true;
 703
 704                         } else if (expr_type == TypeManager.short_type){
 705                                 //
 706                                 // From short to int, long, float, double
 707                                 //
 708                                 if ((target_type == TypeManager.int32_type) ||
 709                                     (target_type == TypeManager.int64_type) ||
 710                                     (target_type == TypeManager.double_type) ||
 711                                     (target_type == TypeManager.float_type) ||
 712                                     (target_type == TypeManager.decimal_type))
 713                                         return true;
 714
 715                         } else if (expr_type == TypeManager.ushort_type){
 716                                 //
 717                                 // From ushort to int, uint, long, ulong, float, double
 718                                 //
 719                                 if ((target_type == TypeManager.uint32_type) ||
 720                                     (target_type == TypeManager.uint64_type) ||
 721                                     (target_type == TypeManager.int32_type) ||
 722                                     (target_type == TypeManager.int64_type) ||
 723                                     (target_type == TypeManager.double_type) ||
 724                                     (target_type == TypeManager.float_type) ||
 725                                     (target_type == TypeManager.decimal_type))
 726                                         return true;
 727
 728                         } else if (expr_type == TypeManager.int32_type){
 729                                 //
 730                                 // From int to long, float, double
 731                                 //
 732                                 if ((target_type == TypeManager.int64_type) ||
 733                                     (target_type == TypeManager.double_type) ||
 734                                     (target_type == TypeManager.float_type) ||
 735                                     (target_type == TypeManager.decimal_type))
 736                                         return true;
 737
 738                         } else if (expr_type == TypeManager.uint32_type){
 739                                 //
 740                                 // From uint to long, ulong, float, double
 741                                 //
 742                                 if ((target_type == TypeManager.int64_type) ||
 743                                     (target_type == TypeManager.uint64_type) ||
 744                                     (target_type == TypeManager.double_type) ||
 745                                     (target_type == TypeManager.float_type) ||
 746                                     (target_type == TypeManager.decimal_type))
 747                                         return true;
 748
 749                         } else if ((expr_type == TypeManager.uint64_type) ||
 750                                    (expr_type == TypeManager.int64_type)) {
 751                                 //
 752                                 // From long/ulong to float, double
 753                                 //
 754                                 if ((target_type == TypeManager.double_type) ||
 755                                     (target_type == TypeManager.float_type) ||
 756                                     (target_type == TypeManager.decimal_type))
 757                                         return true;
 758
 759                         } else if (expr_type == TypeManager.char_type){
 760                                 //
 761                                 // From char to ushort, int, uint, long, ulong, float, double
 762                                 //
 763                                 if ((target_type == TypeManager.ushort_type) ||
 764                                     (target_type == TypeManager.int32_type) ||
 765                                     (target_type == TypeManager.uint32_type) ||
 766                                     (target_type == TypeManager.uint64_type) ||
 767                                     (target_type == TypeManager.int64_type) ||
 768                                     (target_type == TypeManager.float_type) ||
 769                                     (target_type == TypeManager.double_type) ||
 770                                     (target_type == TypeManager.decimal_type))
 771                                         return true;
 772
 773                         } else if (expr_type == TypeManager.float_type){
 774                                 //
 775                                 // float to double
 776                                 //
 777                                 if (target_type == TypeManager.double_type)
 778                                         return true;
 779                         }
 780
 781                         // Next reference conversions
 782
 783                         if (target_type == TypeManager.object_type) {
 784                                 if ((expr_type.IsClass) ||
 785                                     (expr_type.IsValueType))
 786                                         return true;
 787
 788                         } else if (expr_type.IsSubclassOf (target_type)) {
 789                                 return true;
 790
 791                         } else {
 792                                 // from any class-type S to any interface-type T.
 793                                 if (expr_type.IsClass && target_type.IsInterface)
 794                                         return true;
 795
 796                                 // from any interface type S to interface-type T.
 797                                 // FIXME : Is it right to use IsAssignableFrom ?
 798                                 if (expr_type.IsInterface && target_type.IsInterface)
 799                                         if (target_type.IsAssignableFrom (expr_type))
 800                                                 return true;
 801
 802                                 // from an array-type S to an array-type of type T
 803                                 if (expr_type.IsArray && target_type.IsArray) {
 804                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 805
 806                                                 Type expr_element_type = expr_type.GetElementType ();
 807                                                 Type target_element_type = target_type.GetElementType ();
 808
 809                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 810                                                         if (StandardConversionExists (expr_element_type,
 811                                                                                       target_element_type))
 812                                                                 return true;
 813                                         }
 814                                 }
 815
 816                                 // from an array-type to System.Array
 817                                 if (expr_type.IsArray && target_type.IsAssignableFrom (expr_type))
 818                                         return true;
 819
 820                                 // from any delegate type to System.Delegate
 821                                 if (expr_type.IsSubclassOf (TypeManager.delegate_type) &&
 822                                     target_type == TypeManager.delegate_type)
 823                                         if (target_type.IsAssignableFrom (expr_type))
 824                                                 return true;
 825
 826                                 // from any array-type or delegate type into System.ICloneable.
 827                                 if (expr_type.IsArray || expr_type.IsSubclassOf (TypeManager.delegate_type))
 828                                         if (target_type == TypeManager.icloneable_type)
 829                                                 return true;
 830
 831                                 // from the null type to any reference-type.
 832                                 // FIXME : How do we do this ?
 833
 834                         }
 835
 836                         return false;
 837                 }
 838
 839                 /// <summary>
 840                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 841                 ///  amongst the methods in the MethodGroupExpr which convert from a
 842                 ///  type encompassing source_type
 843                 /// </summary>
 844                 static Type FindMostEncompassedType (MethodGroupExpr me, Type source_type)
 845                 {
 846                         Type best = null;
 847
 848                         for (int i = me.Methods.Length; i > 0; ) {
 849                                 i--;
 850
 851                                 MethodBase mb = me.Methods [i];
 852                                 ParameterData pd = Invocation.GetParameterData (mb);
 853                                 Type param_type = pd.ParameterType (0);
 854
 855                                 if (StandardConversionExists (source_type, param_type)) {
 856                                         if (best == null)
 857                                                 best = param_type;
 858
 859                                         if (StandardConversionExists (param_type, best))
 860                                                 best = param_type;
 861                                 }
 862                         }
 863
 864                         return best;
 865                 }
 866
 867                 /// <summary>
 868                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 869                 ///  amongst the methods in the MethodGroupExpr which convert to a
 870                 ///  type encompassed by target_type
 871                 /// </summary>
 872                 static Type FindMostEncompassingType (MethodGroupExpr me, Type target)
 873                 {
 874                         Type best = null;
 875
 876                         for (int i = me.Methods.Length; i > 0; ) {
 877                                 i--;
 878
 879                                 MethodInfo mi = (MethodInfo) me.Methods [i];
 880                                 Type ret_type = mi.ReturnType;
 881
 882                                 if (StandardConversionExists (ret_type, target)) {
 883                                         if (best == null)
 884                                                 best = ret_type;
 885
 886                                         if (!StandardConversionExists (ret_type, best))
 887                                                 best = ret_type;
 888                                 }
 889
 890                         }
 891
 892                         return best;
 893
 894                 }
 895
 896
 897                 /// <summary>
 898                 ///  User-defined Implicit conversions
 899                 /// </summary>
 900                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 901                                                                  Type target, Location loc)
 902                 {
 903                         return UserDefinedConversion (ec, source, target, loc, false);
 904                 }
 905
 906                 /// <summary>
 907                 ///  User-defined Explicit conversions
 908                 /// </summary>
 909                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 910                                                                  Type target, Location loc)
 911                 {
 912                         return UserDefinedConversion (ec, source, target, loc, true);
 913                 }
 914
 915                 /// <summary>
 916                 ///   User-defined conversions
 917                 /// </summary>
 918                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 919                                                                 Type target, Location loc,
 920                                                                 bool look_for_explicit)
 921                 {
 922                         Expression mg1 = null, mg2 = null, mg3 = null, mg4 = null;
 923                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 924                         Expression e;
 925                         MethodBase method = null;
 926                         Type source_type = source.Type;
 927
 928                         string op_name;
 929
 930                         // If we have a boolean type, we need to check for the True operator
 931
 932                         // FIXME : How does the False operator come into the picture ?
 933                         // FIXME : This doesn't look complete and very correct !
 934                         if (target == TypeManager.bool_type)
 935                                 op_name = "op_True";
 936                         else
 937                                 op_name = "op_Implicit";
 938
 939                         mg1 = MemberLookup (ec, source_type, op_name, false, loc);
 940
 941                         if (source_type.BaseType != null)
 942                                 mg2 = MemberLookup (ec, source_type.BaseType, op_name, false, loc);
 943
 944                         mg3 = MemberLookup (ec, target, op_name, false, loc);
 945
 946                         if (target.BaseType != null)
 947                                 mg4 = MemberLookup (ec, target.BaseType, op_name, false, loc);
 948
 949                         MethodGroupExpr union1 = Invocation.MakeUnionSet (mg1, mg2);
 950                         MethodGroupExpr union2 = Invocation.MakeUnionSet (mg3, mg4);
 951
 952                         MethodGroupExpr union3 = Invocation.MakeUnionSet (union1, union2);
 953
 954                         MethodGroupExpr union4 = null;
 955
 956                         if (look_for_explicit) {
 957
 958                                 op_name = "op_Explicit";
 959
 960                                 mg5 = MemberLookup (ec, source_type, op_name, false, loc);
 961
 962                                 if (source_type.BaseType != null)
 963                                         mg6 = MemberLookup (ec, source_type.BaseType, op_name, false, loc);
 964
 965                                 mg7 = MemberLookup (ec, target, op_name, false, loc);
 966
 967                                 if (target.BaseType != null)
 968                                         mg8 = MemberLookup (ec, target.BaseType, op_name, false, loc);
 969
 970                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6);
 971                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8);
 972
 973                                 union4 = Invocation.MakeUnionSet (union5, union6);
 974                         }
 975
 976                         MethodGroupExpr union = Invocation.MakeUnionSet (union3, union4);
 977
 978                         if (union != null) {
 979
 980                                 Type most_specific_source, most_specific_target;
 981
 982                                 most_specific_source = FindMostEncompassedType (union, source_type);
 983                                 if (most_specific_source == null)
 984                                         return null;
 985
 986                                 most_specific_target = FindMostEncompassingType (union, target);
 987                                 if (most_specific_target == null)
 988                                         return null;
 989
 990                                 int count = 0;
 991
 992                                 for (int i = union.Methods.Length; i > 0;) {
 993                                         i--;
 994
 995                                         MethodBase mb = union.Methods [i];
 996                                         ParameterData pd = Invocation.GetParameterData (mb);
 997                                         MethodInfo mi = (MethodInfo) union.Methods [i];
 998
 999                                         if (pd.ParameterType (0) == most_specific_source &&
1000                                             mi.ReturnType == most_specific_target) {
1001                                                 method = mb;
1002                                                 count++;
1003                                         }
1004                                 }
1005
1006                                 if (method == null || count > 1) {
1007                                         Report.Error (-11, loc, "Ambiguous user defined conversion");
1008                                         return null;
1009                                 }
1010
1011                                 //
1012                                 // This will do the conversion to the best match that we
1013                                 // found.  Now we need to perform an implict standard conversion
1014                                 // if the best match was not the type that we were requested
1015                                 // by target.
1016                                 //
1017                                 if (look_for_explicit)
1018                                         source = ConvertExplicitStandard (ec, source, most_specific_source, loc);
1019                                 else
1020                                         source = ConvertImplicitStandard (ec, source,
1021                                                                           most_specific_source, loc);
1022
1023                                 if (source == null)
1024                                         return null;
1025
1026                                 e =  new UserCast ((MethodInfo) method, source);
1027
1028                                 if (e.Type != target){
1029                                         if (!look_for_explicit)
1030                                                 e = ConvertImplicitStandard (ec, e, target, loc);
1031                                         else
1032                                                 e = ConvertExplicitStandard (ec, e, target, loc);
1033
1034                                         return e;
1035                                 } else
1036                                         return e;
1037                         }
1038
1039                         return null;
1040                 }
1041
1042                 /// <summary>
1043                 ///   Converts implicitly the resolved expression `expr' into the
1044                 ///   `target_type'.  It returns a new expression that can be used
1045                 ///   in a context that expects a `target_type'.
1046                 /// </summary>
1047                 static public Expression ConvertImplicit (EmitContext ec, Expression expr,
1048                                                           Type target_type, Location loc)
1049                 {
1050                         Type expr_type = expr.Type;
1051                         Expression e;
1052
1053                         if (expr_type == target_type)
1054                                 return expr;
1055
1056                         if (target_type == null)
1057                                 throw new Exception ("Target type is null");
1058
1059                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1060                         if (e != null)
1061                                 return e;
1062
1063                         e = ImplicitReferenceConversion (expr, target_type);
1064                         if (e != null)
1065                                 return e;
1066
1067                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1068                         if (e != null)
1069                                 return e;
1070
1071                         if (target_type.IsSubclassOf (TypeManager.enum_type) && expr is IntLiteral){
1072                                 IntLiteral i = (IntLiteral) expr;
1073
1074                                 if (i.Value == 0)
1075                                         return new EmptyCast (expr, target_type);
1076                         }
1077
1078                         return null;
1079                 }
1080
1081
1082                 /// <summary>
1083                 ///   Attempts to apply the `Standard Implicit
1084                 ///   Conversion' rules to the expression `expr' into
1085                 ///   the `target_type'.  It returns a new expression
1086                 ///   that can be used in a context that expects a
1087                 ///   `target_type'.
1088                 ///
1089                 ///   This is different from `ConvertImplicit' in that the
1090                 ///   user defined implicit conversions are excluded.
1091                 /// </summary>
1092                 static public Expression ConvertImplicitStandard (EmitContext ec, Expression expr,
1093                                                                   Type target_type, Location loc)
1094                 {
1095                         Type expr_type = expr.Type;
1096                         Expression e;
1097
1098                         if (expr_type == target_type)
1099                                 return expr;
1100
1101                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1102                         if (e != null)
1103                                 return e;
1104
1105                         e = ImplicitReferenceConversion (expr, target_type);
1106                         if (e != null)
1107                                 return e;
1108
1109                         if (target_type.IsSubclassOf (TypeManager.enum_type) && expr is IntLiteral){
1110                                 IntLiteral i = (IntLiteral) expr;
1111
1112                                 if (i.Value == 0)
1113                                         return new EmptyCast (expr, target_type);
1114                         }
1115                         return null;
1116                 }
1117
1118                 /// <summary>
1119                 ///   Attemps to perform an implict constant conversion of the IntLiteral
1120                 ///   into a different data type using casts (See Implicit Constant
1121                 ///   Expression Conversions)
1122                 /// </summary>
1123                 static protected Expression TryImplicitIntConversion (Type target_type, IntLiteral il)
1124                 {
1125                         int value = il.Value;
1126
1127                         if (target_type == TypeManager.sbyte_type){
1128                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1129                                         return new EmptyCast (il, target_type);
1130                         } else if (target_type == TypeManager.byte_type){
1131                                 if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
1132                                         return new EmptyCast (il, target_type);
1133                         } else if (target_type == TypeManager.short_type){
1134                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1135                                         return new EmptyCast (il, target_type);
1136                         } else if (target_type == TypeManager.ushort_type){
1137                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1138                                         return new EmptyCast (il, target_type);
1139                         } else if (target_type == TypeManager.uint32_type){
1140                                 //
1141                                 // we can optimize this case: a positive int32
1142                                 // always fits on a uint32
1143                                 //
1144                                 if (value >= 0)
1145                                         return new EmptyCast (il, target_type);
1146                         } else if (target_type == TypeManager.uint64_type){
1147                                 //
1148                                 // we can optimize this case: a positive int32
1149                                 // always fits on a uint64.  But we need an opcode
1150                                 // to do it.
1151                                 //
1152                                 if (value >= 0)
1153                                         return new OpcodeCast (il, target_type, OpCodes.Conv_I8);
1154                         }
1155
1156                         return null;
1157                 }
1158
1159                 /// <summary>
1160                 ///   Attemptes to implicityly convert `target' into `type', using
1161                 ///   ConvertImplicit.  If there is no implicit conversion, then
1162                 ///   an error is signaled
1163                 /// </summary>
1164                 static public Expression ConvertImplicitRequired (EmitContext ec, Expression source,
1165                                                                   Type target_type, Location loc)
1166                 {
1167                         Expression e;
1168
1169                         e = ConvertImplicit (ec, source, target_type, loc);
1170                         if (e != null)
1171                                 return e;
1172
1173                         string msg = "Cannot convert implicitly from `"+
1174                                 TypeManager.CSharpName (source.Type) + "' to `" +
1175                                 TypeManager.CSharpName (target_type) + "'";
1176
1177                         Error (29, loc, msg);
1178
1179                         return null;
1180                 }
1181
1182                 /// <summary>
1183                 ///   Performs the explicit numeric conversions
1184                 /// </summary>
1185                 static Expression ConvertNumericExplicit (EmitContext ec, Expression expr,
1186                                                           Type target_type)
1187                 {
1188                         Type expr_type = expr.Type;
1189
1190                         if (expr_type == TypeManager.sbyte_type){
1191                                 //
1192                                 // From sbyte to byte, ushort, uint, ulong, char
1193                                 //
1194                                 if (target_type == TypeManager.byte_type)
1195                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1196                                 if (target_type == TypeManager.ushort_type)
1197                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1198                                 if (target_type == TypeManager.uint32_type)
1199                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1200                                 if (target_type == TypeManager.uint64_type)
1201                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1202                                 if (target_type == TypeManager.char_type)
1203                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1204                         } else if (expr_type == TypeManager.byte_type){
1205                                 //
1206                                 // From byte to sbyte and char
1207                                 //
1208                                 if (target_type == TypeManager.sbyte_type)
1209                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1210                                 if (target_type == TypeManager.char_type)
1211                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1212                         } else if (expr_type == TypeManager.short_type){
1213                                 //
1214                                 // From short to sbyte, byte, ushort, uint, ulong, char
1215                                 //
1216                                 if (target_type == TypeManager.sbyte_type)
1217                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1218                                 if (target_type == TypeManager.byte_type)
1219                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1220                                 if (target_type == TypeManager.ushort_type)
1221                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1222                                 if (target_type == TypeManager.uint32_type)
1223                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1224                                 if (target_type == TypeManager.uint64_type)
1225                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1226                                 if (target_type == TypeManager.char_type)
1227                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1228                         } else if (expr_type == TypeManager.ushort_type){
1229                                 //
1230                                 // From ushort to sbyte, byte, short, char
1231                                 //
1232                                 if (target_type == TypeManager.sbyte_type)
1233                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1234                                 if (target_type == TypeManager.byte_type)
1235                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1236                                 if (target_type == TypeManager.short_type)
1237                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1238                                 if (target_type == TypeManager.char_type)
1239                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1240                         } else if (expr_type == TypeManager.int32_type){
1241                                 //
1242                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1243                                 //
1244                                 if (target_type == TypeManager.sbyte_type)
1245                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1246                                 if (target_type == TypeManager.byte_type)
1247                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1248                                 if (target_type == TypeManager.short_type)
1249                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1250                                 if (target_type == TypeManager.ushort_type)
1251                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1252                                 if (target_type == TypeManager.uint32_type)
1253                                         return new EmptyCast (expr, target_type);
1254                                 if (target_type == TypeManager.uint64_type)
1255                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1256                                 if (target_type == TypeManager.char_type)
1257                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1258                         } else if (expr_type == TypeManager.uint32_type){
1259                                 //
1260                                 // From uint to sbyte, byte, short, ushort, int, char
1261                                 //
1262                                 if (target_type == TypeManager.sbyte_type)
1263                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1264                                 if (target_type == TypeManager.byte_type)
1265                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1266                                 if (target_type == TypeManager.short_type)
1267                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1268                                 if (target_type == TypeManager.ushort_type)
1269                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1270                                 if (target_type == TypeManager.int32_type)
1271                                         return new EmptyCast (expr, target_type);
1272                                 if (target_type == TypeManager.char_type)
1273                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1274                         } else if (expr_type == TypeManager.int64_type){
1275                                 //
1276                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1277                                 //
1278                                 if (target_type == TypeManager.sbyte_type)
1279                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1280                                 if (target_type == TypeManager.byte_type)
1281                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1282                                 if (target_type == TypeManager.short_type)
1283                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1284                                 if (target_type == TypeManager.ushort_type)
1285                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1286                                 if (target_type == TypeManager.int32_type)
1287                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1288                                 if (target_type == TypeManager.uint32_type)
1289                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1290                                 if (target_type == TypeManager.uint64_type)
1291                                         return new EmptyCast (expr, target_type);
1292                                 if (target_type == TypeManager.char_type)
1293                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1294                         } else if (expr_type == TypeManager.uint64_type){
1295                                 //
1296                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1297                                 //
1298                                 if (target_type == TypeManager.sbyte_type)
1299                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1300                                 if (target_type == TypeManager.byte_type)
1301                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1302                                 if (target_type == TypeManager.short_type)
1303                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1304                                 if (target_type == TypeManager.ushort_type)
1305                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1306                                 if (target_type == TypeManager.int32_type)
1307                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1308                                 if (target_type == TypeManager.uint32_type)
1309                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1310                                 if (target_type == TypeManager.int64_type)
1311                                         return new EmptyCast (expr, target_type);
1312                                 if (target_type == TypeManager.char_type)
1313                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1314                         } else if (expr_type == TypeManager.char_type){
1315                                 //
1316                                 // From char to sbyte, byte, short
1317                                 //
1318                                 if (target_type == TypeManager.sbyte_type)
1319                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1320                                 if (target_type == TypeManager.byte_type)
1321                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1322                                 if (target_type == TypeManager.short_type)
1323                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1324                         } else if (expr_type == TypeManager.float_type){
1325                                 //
1326                                 // From float to sbyte, byte, short,
1327                                 // ushort, int, uint, long, ulong, char
1328                                 // or decimal
1329                                 //
1330                                 if (target_type == TypeManager.sbyte_type)
1331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1332                                 if (target_type == TypeManager.byte_type)
1333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1334                                 if (target_type == TypeManager.short_type)
1335                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1336                                 if (target_type == TypeManager.ushort_type)
1337                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1338                                 if (target_type == TypeManager.int32_type)
1339                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1340                                 if (target_type == TypeManager.uint32_type)
1341                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1342                                 if (target_type == TypeManager.int64_type)
1343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1344                                 if (target_type == TypeManager.uint64_type)
1345                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1346                                 if (target_type == TypeManager.char_type)
1347                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1348                                 if (target_type == TypeManager.decimal_type)
1349                                         return InternalTypeConstructor (ec, expr, target_type);
1350                         } else if (expr_type == TypeManager.double_type){
1351                                 //
1352                                 // From double to byte, byte, short,
1353                                 // ushort, int, uint, long, ulong,
1354                                 // char, float or decimal
1355                                 //
1356                                 if (target_type == TypeManager.sbyte_type)
1357                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1358                                 if (target_type == TypeManager.byte_type)
1359                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1360                                 if (target_type == TypeManager.short_type)
1361                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1362                                 if (target_type == TypeManager.ushort_type)
1363                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1364                                 if (target_type == TypeManager.int32_type)
1365                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1366                                 if (target_type == TypeManager.uint32_type)
1367                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1368                                 if (target_type == TypeManager.int64_type)
1369                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1370                                 if (target_type == TypeManager.uint64_type)
1371                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1372                                 if (target_type == TypeManager.char_type)
1373                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1374                                 if (target_type == TypeManager.float_type)
1375                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
1376                                 if (target_type == TypeManager.decimal_type)
1377                                         return InternalTypeConstructor (ec, expr, target_type);
1378                         }
1379
1380                         // decimal is taken care of by the op_Explicit methods.
1381
1382                         return null;
1383                 }
1384
1385                 /// <summary>
1386                 ///  Returns whether an explicit reference conversion can be performed
1387                 ///  from source_type to target_type
1388                 /// </summary>
1389                 static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1390                 {
1391                         bool target_is_value_type = target_type.IsValueType;
1392
1393                         if (source_type == target_type)
1394                                 return true;
1395
1396                         //
1397                         // From object to any reference type
1398                         //
1399                         if (source_type == TypeManager.object_type && !target_is_value_type)
1400                                 return true;
1401
1402                         //
1403                         // From any class S to any class-type T, provided S is a base class of T
1404                         //
1405                         if (target_type.IsSubclassOf (source_type))
1406                                 return true;
1407
1408                         //
1409                         // From any interface type S to any interface T provided S is not derived from T
1410                         //
1411                         if (source_type.IsInterface && target_type.IsInterface){
1412                                 if (!target_type.IsSubclassOf (source_type))
1413                                         return true;
1414                         }
1415
1416                         //
1417                         // From any class type S to any interface T, provides S is not sealed
1418                         // and provided S does not implement T.
1419                         //
1420                         if (target_type.IsInterface && !source_type.IsSealed &&
1421                             !target_type.IsAssignableFrom (source_type))
1422                                 return true;
1423
1424                         //
1425                         // From any interface-type S to to any class type T, provided T is not
1426                         // sealed, or provided T implements S.
1427                         //
1428                         if (source_type.IsInterface &&
1429                             (!target_type.IsSealed || source_type.IsAssignableFrom (target_type)))
1430                                 return true;
1431
1432                         // From an array type S with an element type Se to an array type T with an
1433                         // element type Te provided all the following are true:
1434                         //     * S and T differe only in element type, in other words, S and T
1435                         //       have the same number of dimensions.
1436                         //     * Both Se and Te are reference types
1437                         //     * An explicit referenc conversions exist from Se to Te
1438                         //
1439                         if (source_type.IsArray && target_type.IsArray) {
1440                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1441
1442                                         Type source_element_type = source_type.GetElementType ();
1443                                         Type target_element_type = target_type.GetElementType ();
1444
1445                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1446                                                 if (ExplicitReferenceConversionExists (source_element_type,
1447                                                                                        target_element_type))
1448                                                         return true;
1449                                 }
1450                         }
1451
1452
1453                         // From System.Array to any array-type
1454                         if (source_type == TypeManager.array_type &&
1455                             target_type.IsSubclassOf (TypeManager.array_type)){
1456                                 return true;
1457                         }
1458
1459                         //
1460                         // From System delegate to any delegate-type
1461                         //
1462                         if (source_type == TypeManager.delegate_type &&
1463                             target_type.IsSubclassOf (TypeManager.delegate_type))
1464                                 return true;
1465
1466                         //
1467                         // From ICloneable to Array or Delegate types
1468                         //
1469                         if (source_type == TypeManager.icloneable_type &&
1470                             (target_type == TypeManager.array_type ||
1471                              target_type == TypeManager.delegate_type))
1472                                 return true;
1473
1474                         return false;
1475                 }
1476
1477                 /// <summary>
1478                 ///   Implements Explicit Reference conversions
1479                 /// </summary>
1480                 static Expression ConvertReferenceExplicit (Expression source, Type target_type)
1481                 {
1482                         Type source_type = source.Type;
1483                         bool target_is_value_type = target_type.IsValueType;
1484
1485                         //
1486                         // From object to any reference type
1487                         //
1488                         if (source_type == TypeManager.object_type && !target_is_value_type)
1489                                 return new ClassCast (source, target_type);
1490
1491
1492                         //
1493                         // From any class S to any class-type T, provided S is a base class of T
1494                         //
1495                         if (target_type.IsSubclassOf (source_type))
1496                                 return new ClassCast (source, target_type);
1497
1498                         //
1499                         // From any interface type S to any interface T provided S is not derived from T
1500                         //
1501                         if (source_type.IsInterface && target_type.IsInterface){
1502
1503                                 Type [] ifaces = source_type.GetInterfaces ();
1504
1505                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1506                                         return null;
1507                                 else
1508                                         return new ClassCast (source, target_type);
1509                         }
1510
1511                         //
1512                         // From any class type S to any interface T, provides S is not sealed
1513                         // and provided S does not implement T.
1514                         //
1515                         if (target_type.IsInterface && !source_type.IsSealed) {
1516
1517                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1518                                         return null;
1519                                 else
1520                                         return new ClassCast (source, target_type);
1521
1522                         }
1523
1524                         //
1525                         // From any interface-type S to to any class type T, provided T is not
1526                         // sealed, or provided T implements S.
1527                         //
1528                         if (source_type.IsInterface) {
1529
1530                                 if (target_type.IsSealed)
1531                                         return null;
1532
1533                                 if (TypeManager.ImplementsInterface (target_type, source_type))
1534                                         return new ClassCast (source, target_type);
1535                                 else
1536                                         return null;
1537                         }
1538
1539                         // From an array type S with an element type Se to an array type T with an
1540                         // element type Te provided all the following are true:
1541                         //     * S and T differe only in element type, in other words, S and T
1542                         //       have the same number of dimensions.
1543                         //     * Both Se and Te are reference types
1544                         //     * An explicit referenc conversions exist from Se to Te
1545                         //
1546                         if (source_type.IsArray && target_type.IsArray) {
1547                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1548
1549                                         Type source_element_type = source_type.GetElementType ();
1550                                         Type target_element_type = target_type.GetElementType ();
1551
1552                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1553                                                 if (ExplicitReferenceConversionExists (source_element_type,
1554                                                                                        target_element_type))
1555                                                         return new ClassCast (source, target_type);
1556                                 }
1557                         }
1558
1559
1560                         // From System.Array to any array-type
1561                         if (source_type == TypeManager.array_type &&
1562                             target_type.IsSubclassOf (TypeManager.array_type)){
1563                                 return new ClassCast (source, target_type);
1564                         }
1565
1566                         //
1567                         // From System delegate to any delegate-type
1568                         //
1569                         if (source_type == TypeManager.delegate_type &&
1570                             target_type.IsSubclassOf (TypeManager.delegate_type))
1571                                 return new ClassCast (source, target_type);
1572
1573                         //
1574                         // From ICloneable to Array or Delegate types
1575                         //
1576                         if (source_type == TypeManager.icloneable_type &&
1577                             (target_type == TypeManager.array_type ||
1578                              target_type == TypeManager.delegate_type))
1579                                 return new ClassCast (source, target_type);
1580
1581                         return null;
1582                 }
1583
1584                 /// <summary>
1585                 ///   Performs an explicit conversion of the expression `expr' whose
1586                 ///   type is expr.Type to `target_type'.
1587                 /// </summary>
1588                 static public Expression ConvertExplicit (EmitContext ec, Expression expr,
1589                                                           Type target_type, Location loc)
1590                 {
1591                         Type expr_type = expr.Type;
1592                         Expression ne = ConvertImplicitStandard (ec, expr, target_type, loc);
1593
1594                         if (ne != null)
1595                                 return ne;
1596
1597                         ne = ConvertNumericExplicit (ec, expr, target_type);
1598                         if (ne != null)
1599                                 return ne;
1600
1601                         //
1602                         // Unboxing conversion.
1603                         //
1604                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1605                                 return new UnboxCast (expr, target_type);
1606
1607                         //
1608                         // Enum types
1609                         //
1610                         if (expr is EnumLiteral) {
1611                                 Expression e = ((EnumLiteral) expr).Child;
1612
1613                                 return ConvertImplicit (ec, e, target_type, loc);
1614                         }
1615
1616                         ne = ConvertReferenceExplicit (expr, target_type);
1617                         if (ne != null)
1618                                 return ne;
1619
1620                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1621                         if (ne != null)
1622                                 return ne;
1623
1624                         error30 (loc, expr_type, target_type);
1625                         return null;
1626                 }
1627
1628                 /// <summary>
1629                 ///   Same as ConverExplicit, only it doesn't include user defined conversions
1630                 /// </summary>
1631                 static public Expression ConvertExplicitStandard (EmitContext ec, Expression expr,
1632                                                                   Type target_type, Location l)
1633                 {
1634                         Expression ne = ConvertImplicitStandard (ec, expr, target_type, l);
1635
1636                         if (ne != null)
1637                                 return ne;
1638
1639                         ne = ConvertNumericExplicit (ec, expr, target_type);
1640                         if (ne != null)
1641                                 return ne;
1642
1643                         ne = ConvertReferenceExplicit (expr, target_type);
1644                         if (ne != null)
1645                                 return ne;
1646
1647                         error30 (l, expr.Type, target_type);
1648                         return null;
1649                 }
1650
1651                 static string ExprClassName (ExprClass c)
1652                 {
1653                         switch (c){
1654                         case ExprClass.Invalid:
1655                                 return "Invalid";
1656                         case ExprClass.Value:
1657                                 return "value";
1658                         case ExprClass.Variable:
1659                                 return "variable";
1660                         case ExprClass.Namespace:
1661                                 return "namespace";
1662                         case ExprClass.Type:
1663                                 return "type";
1664                         case ExprClass.MethodGroup:
1665                                 return "method group";
1666                         case ExprClass.PropertyAccess:
1667                                 return "property access";
1668                         case ExprClass.EventAccess:
1669                                 return "event access";
1670                         case ExprClass.IndexerAccess:
1671                                 return "indexer access";
1672                         case ExprClass.Nothing:
1673                                 return "null";
1674                         }
1675                         throw new Exception ("Should not happen");
1676                 }
1677
1678                 /// <summary>
1679                 ///   Reports that we were expecting `expr' to be of class `expected'
1680                 /// </summary>
1681                 protected void report118 (Location loc, Expression expr, string expected)
1682                 {
1683                         string kind = "Unknown";
1684
1685                         if (expr != null)
1686                                 kind = ExprClassName (expr.ExprClass);
1687
1688                         Error (118, loc, "Expression denotes a '" + kind +
1689                                "' where an " + expected + " was expected");
1690                 }
1691
1692                 /// <summary>
1693                 ///   This function tries to reduce the expression performing
1694                 ///   constant folding and common subexpression elimination
1695                 /// </summary>
1696                 static public Expression Reduce (EmitContext ec, Expression e)
1697                 {
1698                         //Console.WriteLine ("Calling reduce");
1699                         return e.Reduce (ec);
1700                 }
1701         }
1702
1703         /// <summary>
1704         ///   This is just a base class for expressions that can
1705         ///   appear on statements (invocations, object creation,
1706         ///   assignments, post/pre increment and decrement).  The idea
1707         ///   being that they would support an extra Emition interface that
1708         ///   does not leave a result on the stack.
1709         /// </summary>
1710         public abstract class ExpressionStatement : Expression {
1711
1712                 /// <summary>
1713                 ///   Requests the expression to be emitted in a `statement'
1714                 ///   context.  This means that no new value is left on the
1715                 ///   stack after invoking this method (constrasted with
1716                 ///   Emit that will always leave a value on the stack).
1717                 /// </summary>
1718                 public abstract void EmitStatement (EmitContext ec);
1719         }
1720
1721         /// <summary>
1722         ///   This kind of cast is used to encapsulate the child
1723         ///   whose type is child.Type into an expression that is
1724         ///   reported to return "return_type".  This is used to encapsulate
1725         ///   expressions which have compatible types, but need to be dealt
1726         ///   at higher levels with.
1727         ///
1728         ///   For example, a "byte" expression could be encapsulated in one
1729         ///   of these as an "unsigned int".  The type for the expression
1730         ///   would be "unsigned int".
1731         ///
1732         /// </summary>
1733         public class EmptyCast : Expression {
1734                 protected Expression child;
1735
1736                 public EmptyCast (Expression child, Type return_type)
1737                 {
1738                         ExprClass = child.ExprClass;
1739                         type = return_type;
1740                         this.child = child;
1741                 }
1742
1743                 public override Expression DoResolve (EmitContext ec)
1744                 {
1745                         // This should never be invoked, we are born in fully
1746                         // initialized state.
1747
1748                         return this;
1749                 }
1750
1751                 public override void Emit (EmitContext ec)
1752                 {
1753                         child.Emit (ec);
1754                 }
1755
1756         }
1757
1758         /// <summary>
1759         ///  This class is used to wrap literals which belong inside Enums
1760         /// </summary>
1761         public class EnumLiteral : Literal {
1762                 public Expression Child;
1763
1764                 public EnumLiteral (Expression child, Type enum_type)
1765                 {
1766                         ExprClass = child.ExprClass;
1767                         this.Child = child;
1768                         type = enum_type;
1769                 }
1770
1771                 public override Expression DoResolve (EmitContext ec)
1772                 {
1773                         // This should never be invoked, we are born in fully
1774                         // initialized state.
1775
1776                         return this;
1777                 }
1778
1779                 public override void Emit (EmitContext ec)
1780                 {
1781                         Child.Emit (ec);
1782                 }
1783
1784                 public override object GetValue ()
1785                 {
1786                         return ((Literal) Child).GetValue ();
1787                 }
1788
1789                 public override string AsString ()
1790                 {
1791                         return ((Literal) Child).AsString ();
1792                 }
1793         }
1794
1795         /// <summary>
1796         ///   This kind of cast is used to encapsulate Value Types in objects.
1797         ///
1798         ///   The effect of it is to box the value type emitted by the previous
1799         ///   operation.
1800         /// </summary>
1801         public class BoxedCast : EmptyCast {
1802
1803                 public BoxedCast (Expression expr)
1804                         : base (expr, TypeManager.object_type)
1805                 {
1806                 }
1807
1808                 public override Expression DoResolve (EmitContext ec)
1809                 {
1810                         // This should never be invoked, we are born in fully
1811                         // initialized state.
1812
1813                         return this;
1814                 }
1815
1816                 public override void Emit (EmitContext ec)
1817                 {
1818                         base.Emit (ec);
1819                         ec.ig.Emit (OpCodes.Box, child.Type);
1820                 }
1821         }
1822
1823         public class UnboxCast : EmptyCast {
1824                 public UnboxCast (Expression expr, Type return_type)
1825                         : base (expr, return_type)
1826                 {
1827                 }
1828
1829                 public override Expression DoResolve (EmitContext ec)
1830                 {
1831                         // This should never be invoked, we are born in fully
1832                         // initialized state.
1833
1834                         return this;
1835                 }
1836
1837                 public override void Emit (EmitContext ec)
1838                 {
1839                         Type t = type;
1840                         ILGenerator ig = ec.ig;
1841
1842                         base.Emit (ec);
1843                         ig.Emit (OpCodes.Unbox, t);
1844
1845                         //
1846                         // Load the object from the pointer
1847                         //
1848                         if (t == TypeManager.int32_type)
1849                                 ig.Emit (OpCodes.Ldind_I4);
1850                         else if (t == TypeManager.uint32_type)
1851                                 ig.Emit (OpCodes.Ldind_U4);
1852                         else if (t == TypeManager.short_type)
1853                                 ig.Emit (OpCodes.Ldind_I2);
1854                         else if (t == TypeManager.ushort_type)
1855                                 ig.Emit (OpCodes.Ldind_U2);
1856                         else if (t == TypeManager.char_type)
1857                                 ig.Emit (OpCodes.Ldind_U2);
1858                         else if (t == TypeManager.byte_type)
1859                                 ig.Emit (OpCodes.Ldind_U1);
1860                         else if (t == TypeManager.sbyte_type)
1861                                 ig.Emit (OpCodes.Ldind_I1);
1862                         else if (t == TypeManager.uint64_type)
1863                                 ig.Emit (OpCodes.Ldind_I8);
1864                         else if (t == TypeManager.int64_type)
1865                                 ig.Emit (OpCodes.Ldind_I8);
1866                         else if (t == TypeManager.float_type)
1867                                 ig.Emit (OpCodes.Ldind_R4);
1868                         else if (t == TypeManager.double_type)
1869                                 ig.Emit (OpCodes.Ldind_R8);
1870                         else if (t == TypeManager.bool_type)
1871                                 ig.Emit (OpCodes.Ldind_I1);
1872                         else if (t == TypeManager.intptr_type)
1873                                 ig.Emit (OpCodes.Ldind_I);
1874                         else
1875                                 ig.Emit (OpCodes.Ldobj, t);
1876                 }
1877         }
1878
1879         /// <summary>
1880         ///   This kind of cast is used to encapsulate a child expression
1881         ///   that can be trivially converted to a target type using one or
1882         ///   two opcodes.  The opcodes are passed as arguments.
1883         /// </summary>
1884         public class OpcodeCast : EmptyCast {
1885                 OpCode op, op2;
1886                 bool second_valid;
1887
1888                 public OpcodeCast (Expression child, Type return_type, OpCode op)
1889                         : base (child, return_type)
1890
1891                 {
1892                         this.op = op;
1893                         second_valid = false;
1894                 }
1895
1896                 public OpcodeCast (Expression child, Type return_type, OpCode op, OpCode op2)
1897                         : base (child, return_type)
1898
1899                 {
1900                         this.op = op;
1901                         this.op2 = op2;
1902                         second_valid = true;
1903                 }
1904
1905                 public override Expression DoResolve (EmitContext ec)
1906                 {
1907                         // This should never be invoked, we are born in fully
1908                         // initialized state.
1909
1910                         return this;
1911                 }
1912
1913                 public override void Emit (EmitContext ec)
1914                 {
1915                         base.Emit (ec);
1916                         ec.ig.Emit (op);
1917
1918                         if (second_valid)
1919                                 ec.ig.Emit (op2);
1920                 }
1921
1922         }
1923
1924         /// <summary>
1925         ///   This kind of cast is used to encapsulate a child and cast it
1926         ///   to the class requested
1927         /// </summary>
1928         public class ClassCast : EmptyCast {
1929                 public ClassCast (Expression child, Type return_type)
1930                         : base (child, return_type)
1931
1932                 {
1933                 }
1934
1935                 public override Expression DoResolve (EmitContext ec)
1936                 {
1937                         // This should never be invoked, we are born in fully
1938                         // initialized state.
1939
1940                         return this;
1941                 }
1942
1943                 public override void Emit (EmitContext ec)
1944                 {
1945                         base.Emit (ec);
1946
1947                         ec.ig.Emit (OpCodes.Castclass, type);
1948                 }
1949
1950         }
1951
1952         /// <summary>
1953         ///   SimpleName expressions are initially formed of a single
1954         ///   word and it only happens at the beginning of the expression.
1955         /// </summary>
1956         ///
1957         /// <remarks>
1958         ///   The expression will try to be bound to a Field, a Method
1959         ///   group or a Property.  If those fail we pass the name to our
1960         ///   caller and the SimpleName is compounded to perform a type
1961         ///   lookup.  The idea behind this process is that we want to avoid
1962         ///   creating a namespace map from the assemblies, as that requires
1963         ///   the GetExportedTypes function to be called and a hashtable to
1964         ///   be constructed which reduces startup time.  If later we find
1965         ///   that this is slower, we should create a `NamespaceExpr' expression
1966         ///   that fully participates in the resolution process.
1967         ///
1968         ///   For example `System.Console.WriteLine' is decomposed into
1969         ///   MemberAccess (MemberAccess (SimpleName ("System"), "Console"), "WriteLine")
1970         ///
1971         ///   The first SimpleName wont produce a match on its own, so it will
1972         ///   be turned into:
1973         ///   MemberAccess (SimpleName ("System.Console"), "WriteLine").
1974         ///
1975         ///   System.Console will produce a TypeExpr match.
1976         ///
1977         ///   The downside of this is that we might be hitting `LookupType' too many
1978         ///   times with this scheme.
1979         /// </remarks>
1980         public class SimpleName : Expression {
1981                 public readonly string Name;
1982                 public readonly Location Location;
1983
1984                 public SimpleName (string name, Location l)
1985                 {
1986                         Name = name;
1987                         Location = l;
1988                 }
1989
1990                 public static void Error120 (Location l, string name)
1991                 {
1992                         Report.Error (
1993                                 120, l,
1994                                 "An object reference is required " +
1995                                 "for the non-static field `"+name+"'");
1996                 }
1997
1998                 //
1999                 // Checks whether we are trying to access an instance
2000                 // property, method or field from a static body.
2001                 //
2002                 Expression MemberStaticCheck (Expression e)
2003                 {
2004                         if (e is FieldExpr){
2005                                 FieldInfo fi = ((FieldExpr) e).FieldInfo;
2006
2007                                 if (!fi.IsStatic){
2008                                         Error120 (Location, Name);
2009                                         return null;
2010                                 }
2011                         } else if (e is MethodGroupExpr){
2012                                 MethodGroupExpr mg = (MethodGroupExpr) e;
2013
2014                                 if (!mg.RemoveInstanceMethods ()){
2015                                         Error120 (Location, mg.Methods [0].Name);
2016                                         return null;
2017                                 }
2018                                 return e;
2019                         } else if (e is PropertyExpr){
2020                                 if (!((PropertyExpr) e).IsStatic){
2021                                         Error120 (Location, Name);
2022                                         return null;
2023                                 }
2024                         }
2025
2026                         return e;
2027                 }
2028
2029                 // <remarks>
2030                 //   7.5.2: Simple Names.
2031                 //
2032                 //   Local Variables and Parameters are handled at
2033                 //   parse time, so they never occur as SimpleNames.
2034                 // </remarks>
2035                 public override Expression DoResolve (EmitContext ec)
2036                 {
2037                         Expression e;
2038
2039                         //
2040                         // Stage 1: Performed by the parser (binding to local or parameters).
2041                         //
2042
2043                         //
2044                         // Stage 2: Lookup members
2045                         //
2046                         e = MemberLookup (ec, ec.TypeContainer.TypeBuilder, Name, true, Location);
2047                         if (e == null){
2048                                 //
2049                                 // Stage 3: Lookup symbol in the various namespaces.
2050                                 //
2051                                 Type t;
2052
2053                                 if ((t = ec.TypeContainer.LookupType (Name, true)) != null)
2054                                         return new TypeExpr (t);
2055
2056                                 //
2057                                 // Stage 3 part b: Lookup up if we are an alias to a type
2058                                 // or a namespace.
2059                                 //
2060                                 // Since we are cheating: we only do the Alias lookup for
2061                                 // namespaces if the name does not include any dots in it
2062                                 //
2063
2064                                 // IMPLEMENT ME.  Read mcs/mcs/TODO for ideas, or rewrite
2065                                 // using NamespaceExprs (dunno how that fixes the alias
2066                                 // per-file though).
2067
2068                                 // No match, maybe our parent can compose us
2069                                 // into something meaningful.
2070                                 //
2071                                 return this;
2072                         }
2073
2074                         // Step 2, continues here.
2075                         if (e is TypeExpr)
2076                                 return e;
2077
2078                         if (e is FieldExpr){
2079                                 FieldExpr fe = (FieldExpr) e;
2080
2081                                 if (!fe.FieldInfo.IsStatic)
2082                                         fe.InstanceExpression = new This (Location.Null);
2083                         }
2084
2085                         if (ec.IsStatic)
2086                                 return MemberStaticCheck (e);
2087                         else
2088                                 return e;
2089                 }
2090
2091                 public override void Emit (EmitContext ec)
2092                 {
2093                         //
2094                         // If this is ever reached, then we failed to
2095                         // find the name as a namespace
2096                         //
2097
2098                         Error (103, Location, "The name `" + Name +
2099                                "' does not exist in the class `" +
2100                                ec.TypeContainer.Name + "'");
2101                 }
2102         }
2103
2104         /// <summary>
2105         ///   Fully resolved expression that evaluates to a type
2106         /// </summary>
2107         public class TypeExpr : Expression {
2108                 public TypeExpr (Type t)
2109                 {
2110                         Type = t;
2111                         eclass = ExprClass.Type;
2112                 }
2113
2114                 override public Expression DoResolve (EmitContext ec)
2115                 {
2116                         return this;
2117                 }
2118
2119                 override public void Emit (EmitContext ec)
2120                 {
2121                         throw new Exception ("Implement me");
2122                 }
2123         }
2124
2125         /// <summary>
2126         ///   MethodGroup Expression.
2127         ///
2128         ///   This is a fully resolved expression that evaluates to a type
2129         /// </summary>
2130         public class MethodGroupExpr : Expression {
2131                 public MethodBase [] Methods;
2132                 Expression instance_expression = null;
2133
2134                 public MethodGroupExpr (MemberInfo [] mi)
2135                 {
2136                         Methods = new MethodBase [mi.Length];
2137                         mi.CopyTo (Methods, 0);
2138                         eclass = ExprClass.MethodGroup;
2139                 }
2140
2141                 public MethodGroupExpr (ArrayList l)
2142                 {
2143                         Methods = new MethodBase [l.Count];
2144
2145                         l.CopyTo (Methods, 0);
2146                         eclass = ExprClass.MethodGroup;
2147                 }
2148
2149                 //
2150                 // `A method group may have associated an instance expression'
2151                 //
2152                 public Expression InstanceExpression {
2153                         get {
2154                                 return instance_expression;
2155                         }
2156
2157                         set {
2158                                 instance_expression = value;
2159                         }
2160                 }
2161
2162                 override public Expression DoResolve (EmitContext ec)
2163                 {
2164                         return this;
2165                 }
2166
2167                 override public void Emit (EmitContext ec)
2168                 {
2169                         throw new Exception ("This should never be reached");
2170                 }
2171
2172                 bool RemoveMethods (bool keep_static)
2173                 {
2174                         ArrayList smethods = new ArrayList ();
2175                         int top = Methods.Length;
2176                         int i;
2177
2178                         for (i = 0; i < top; i++){
2179                                 MethodBase mb = Methods [i];
2180
2181                                 if (mb.IsStatic == keep_static)
2182                                         smethods.Add (mb);
2183                         }
2184
2185                         if (smethods.Count == 0)
2186                                 return false;
2187
2188                         Methods = new MethodBase [smethods.Count];
2189                         smethods.CopyTo (Methods, 0);
2190
2191                         return true;
2192                 }
2193
2194                 /// <summary>
2195                 ///   Removes any instance methods from the MethodGroup, returns
2196                 ///   false if the resulting set is empty.
2197                 /// </summary>
2198                 public bool RemoveInstanceMethods ()
2199                 {
2200                         return RemoveMethods (true);
2201                 }
2202
2203                 /// <summary>
2204                 ///   Removes any static methods from the MethodGroup, returns
2205                 ///   false if the resulting set is empty.
2206                 /// </summary>
2207                 public bool RemoveStaticMethods ()
2208                 {
2209                         return RemoveMethods (false);
2210                 }
2211         }
2212
2213         /// <summary>
2214         ///   Fully resolved expression that evaluates to a Field
2215         /// </summary>
2216         public class FieldExpr : Expression, IAssignMethod, IMemoryLocation {
2217                 public readonly FieldInfo FieldInfo;
2218                 public Expression InstanceExpression;
2219                 Location loc;
2220
2221                 public FieldExpr (FieldInfo fi, Location l)
2222                 {
2223                         FieldInfo = fi;
2224                         eclass = ExprClass.Variable;
2225                         type = fi.FieldType;
2226                         loc = l;
2227                 }
2228
2229                 override public Expression DoResolve (EmitContext ec)
2230                 {
2231                         if (!FieldInfo.IsStatic){
2232                                 if (InstanceExpression == null){
2233                                         throw new Exception ("non-static FieldExpr without instance var\n" +
2234                                                              "You have to assign the Instance variable\n" +
2235                                                              "Of the FieldExpr to set this\n");
2236                                 }
2237
2238                                 InstanceExpression = InstanceExpression.Resolve (ec);
2239                                 if (InstanceExpression == null)
2240                                         return null;
2241
2242                         }
2243                         return this;
2244                 }
2245
2246                 public Expression DoResolveLValue (EmitContext ec)
2247                 {
2248                         if (!FieldInfo.IsInitOnly)
2249                                 return this;
2250
2251                         //
2252                         // InitOnly fields can only be assigned in constructors
2253                         //
2254
2255                         if (ec.IsConstructor)
2256                                 return this;
2257
2258                         Report.Error (191, loc,
2259                                       "Readonly field can not be assigned outside " +
2260                                       "of constructor or variable initializer");
2261
2262                         return null;
2263                 }
2264
2265                 override public void Emit (EmitContext ec)
2266                 {
2267                         ILGenerator ig = ec.ig;
2268
2269                         if (FieldInfo.IsStatic)
2270                                 ig.Emit (OpCodes.Ldsfld, FieldInfo);
2271                         else {
2272                                 InstanceExpression.Emit (ec);
2273
2274                                 ig.Emit (OpCodes.Ldfld, FieldInfo);
2275                         }
2276                 }
2277
2278                 public void EmitAssign (EmitContext ec, Expression source)
2279                 {
2280                         bool is_static = FieldInfo.IsStatic;
2281
2282                         if (!is_static)
2283                                 InstanceExpression.Emit (ec);
2284                         source.Emit (ec);
2285
2286                         if (is_static)
2287                                 ec.ig.Emit (OpCodes.Stsfld, FieldInfo);
2288                         else
2289                                 ec.ig.Emit (OpCodes.Stfld, FieldInfo);
2290
2291                 }
2292
2293                 public void AddressOf (EmitContext ec)
2294                 {
2295                         if (FieldInfo.IsStatic)
2296                                 ec.ig.Emit (OpCodes.Ldsflda, FieldInfo);
2297                         else {
2298                                 InstanceExpression.Emit (ec);
2299                                 ec.ig.Emit (OpCodes.Ldflda, FieldInfo);
2300                         }
2301                 }
2302         }
2303
2304         /// <summary>
2305         ///   Expression that evaluates to a Property.  The Assign class
2306         ///   might set the `Value' expression if we are in an assignment.
2307         ///
2308         ///   This is not an LValue because we need to re-write the expression, we
2309         ///   can not take data from the stack and store it.
2310         /// </summary>
2311         public class PropertyExpr : ExpressionStatement, IAssignMethod {
2312                 public readonly PropertyInfo PropertyInfo;
2313                 public readonly bool IsStatic;
2314                 MethodInfo [] Accessors;
2315                 Location loc;
2316
2317                 Expression instance_expr;
2318
2319                 public PropertyExpr (PropertyInfo pi, Location l)
2320                 {
2321                         PropertyInfo = pi;
2322                         eclass = ExprClass.PropertyAccess;
2323                         IsStatic = false;
2324                         loc = l;
2325                         Accessors = TypeManager.GetAccessors (pi);
2326
2327                         if (Accessors != null)
2328                                 for (int i = 0; i < Accessors.Length; i++){
2329                                         if (Accessors [i] != null)
2330                                                 if (Accessors [i].IsStatic)
2331                                                         IsStatic = true;
2332                                 }
2333                         else
2334                                 Accessors = new MethodInfo [2];
2335
2336                         type = pi.PropertyType;
2337                 }
2338
2339                 //
2340                 // The instance expression associated with this expression
2341                 //
2342                 public Expression InstanceExpression {
2343                         set {
2344                                 instance_expr = value;
2345                         }
2346
2347                         get {
2348                                 return instance_expr;
2349                         }
2350                 }
2351
2352                 public bool VerifyAssignable ()
2353                 {
2354                         if (!PropertyInfo.CanWrite){
2355                                 Report.Error (200, loc,
2356                                               "The property `" + PropertyInfo.Name +
2357                                               "' can not be assigned to, as it has not set accessor");
2358                                 return false;
2359                         }
2360
2361                         return true;
2362                 }
2363
2364                 override public Expression DoResolve (EmitContext ec)
2365                 {
2366                         if (!PropertyInfo.CanRead){
2367                                 Report.Error (154, loc,
2368                                               "The property `" + PropertyInfo.Name +
2369                                               "' can not be used in " +
2370                                               "this context because it lacks a get accessor");
2371                                 return null;
2372                         }
2373
2374                         return this;
2375                 }
2376
2377                 override public void Emit (EmitContext ec)
2378                 {
2379                         Invocation.EmitCall (ec, IsStatic, instance_expr, Accessors [0], null);
2380
2381                 }
2382
2383                 //
2384                 // Implements the IAssignMethod interface for assignments
2385                 //
2386                 public void EmitAssign (EmitContext ec, Expression source)
2387                 {
2388                         Argument arg = new Argument (source, Argument.AType.Expression);
2389                         ArrayList args = new ArrayList ();
2390
2391                         args.Add (arg);
2392                         Invocation.EmitCall (ec, IsStatic, instance_expr, Accessors [1], args);
2393                 }
2394
2395                 override public void EmitStatement (EmitContext ec)
2396                 {
2397                         Emit (ec);
2398                         ec.ig.Emit (OpCodes.Pop);
2399                 }
2400         }
2401
2402         /// <summary>
2403         ///   Fully resolved expression that evaluates to a Expression
2404         /// </summary>
2405         public class EventExpr : Expression {
2406                 public readonly EventInfo EventInfo;
2407                 Location loc;
2408
2409                 public EventExpr (EventInfo ei, Location loc)
2410                 {
2411                         EventInfo = ei;
2412                         this.loc = loc;
2413                         eclass = ExprClass.EventAccess;
2414                 }
2415
2416                 override public Expression DoResolve (EmitContext ec)
2417                 {
2418                         // We are born in resolved state.
2419                         return this;
2420                 }
2421
2422                 override public void Emit (EmitContext ec)
2423                 {
2424                         throw new Exception ("Implement me");
2425                         // FIXME: Implement.
2426                 }
2427         }
2428
2429 }