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