mcs/bmcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 //
  23                 // This is used to prettify the code: a null argument is allowed
  24                 // for ImplicitStandardConversion as long as it is known that
  25                 // no anonymous method will play a role.
  26                 //
  27                 // FIXME: renamed from `const' to `static' to allow bootstraping from older
  28                 // versions of the compiler that could not cope with this construct.
  29                 //
  30                 public static EmitContext ConstantEC = null;
  31
  32                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  33                 {
  34                         Report.Error (30, loc, "Cannot convert type '" +
  35                                       TypeManager.CSharpName (source) + "' to '" +
  36                                       TypeManager.CSharpName (target) + "'");
  37                 }
  38
  39                 static Expression TypeParameter_to_Null (Expression expr, Type target_type,
  40                                                          Location loc)
  41                 {
  42                         if (!TypeParameter_to_Null (target_type)) {
  43                                 Report.Error (403, loc, "Cannot convert null to the type " +
  44                                               "parameter `{0}' becaues it could be a value " +
  45                                               "type.  Consider using `default ({0})' instead.",
  46                                               target_type);
  47                                 return null;
  48                         }
  49
  50                         return new NullCast (expr, target_type);
  51                 }
  52
  53                 static bool TypeParameter_to_Null (Type target_type)
  54                 {
  55                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (target_type);
  56                         if (gc == null)
  57                                 return false;
  58
  59                         if (gc.HasReferenceTypeConstraint)
  60                                 return true;
  61                         if (gc.HasClassConstraint && !TypeManager.IsValueType (gc.ClassConstraint))
  62                                 return true;
  63
  64                         return false;
  65                 }
  66
  67                 static Type TypeParam_EffectiveBaseType (EmitContext ec, Type t)
  68                 {
  69                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (t);
  70                         if (gc == null)
  71                                 return TypeManager.object_type;
  72
  73                         return TypeParam_EffectiveBaseType (ec, gc);
  74                 }
  75
  76                 static Type TypeParam_EffectiveBaseType (EmitContext ec, GenericConstraints gc)
  77                 {
  78                         ArrayList list = new ArrayList ();
  79                         list.Add (gc.EffectiveBaseClass);
  80                         foreach (Type t in gc.InterfaceConstraints) {
  81                                 if (!t.IsGenericParameter)
  82                                         continue;
  83
  84                                 GenericConstraints new_gc = TypeManager.GetTypeParameterConstraints (t);
  85                                 if (new_gc != null)
  86                                         list.Add (TypeParam_EffectiveBaseType (ec, new_gc));
  87                         }
  88                         return FindMostEncompassedType (ec, list);
  89                 }
  90
  91                 static Expression TypeParameterConversion (Expression expr, bool is_reference, Type target_type)
  92                 {
  93                         if (is_reference)
  94                                 return new EmptyCast (expr, target_type);
  95                         else
  96                                 return new BoxedCast (expr, target_type);
  97                 }
  98
  99                 static Expression ImplicitTypeParameterConversion (EmitContext ec, Expression expr,
 100                                                                    Type target_type)
 101                 {
 102                         Type expr_type = expr.Type;
 103
 104                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (expr_type);
 105
 106                         if (gc == null) {
 107                                 if (target_type == TypeManager.object_type)
 108                                         return new BoxedCast (expr);
 109
 110                                 return null;
 111                         }
 112
 113                         // We're converting from a type parameter which is known to be a reference type.
 114                         bool is_reference = gc.IsReferenceType;
 115                         Type base_type = TypeParam_EffectiveBaseType (ec, gc);
 116
 117                         if (TypeManager.IsSubclassOf (base_type, target_type))
 118                                 return TypeParameterConversion (expr, is_reference, target_type);
 119
 120                         if (target_type.IsInterface) {
 121                                 if (TypeManager.ImplementsInterface (base_type, target_type))
 122                                         return TypeParameterConversion (expr, is_reference, target_type);
 123
 124                                 foreach (Type t in gc.InterfaceConstraints) {
 125                                         if (TypeManager.IsSubclassOf (t, target_type))
 126                                                 return TypeParameterConversion (expr, is_reference, target_type);
 127                                 }
 128                         }
 129
 130                         foreach (Type t in gc.InterfaceConstraints) {
 131                                 if (!t.IsGenericParameter)
 132                                         continue;
 133                                 if (TypeManager.IsSubclassOf (t, target_type))
 134                                         return TypeParameterConversion (expr, is_reference, target_type);
 135                         }
 136
 137                         return null;
 138                 }
 139
 140                 static EmptyExpression MyEmptyExpr;
 141                 static public Expression WideningReferenceConversion (EmitContext ec, Expression expr, Type target_type)
 142                 {
 143                         Type expr_type = expr.Type;
 144
 145                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
 146                                 // if we are a method group, emit a warning
 147
 148                                 expr.Emit (null);
 149                         }
 150
 151                         if (expr_type == TypeManager.void_type)
 152                                 return null;
 153
 154                         if (expr_type.IsGenericParameter)
 155                                 return ImplicitTypeParameterConversion (ec, expr, target_type);
 156
 157                         //
 158                         // notice that it is possible to write "ValueType v = 1", the ValueType here
 159                         // is an abstract class, and not really a value type, so we apply the same rules.
 160                         //
 161                         if (target_type == TypeManager.object_type) {
 162                                 //
 163                                 // A pointer type cannot be converted to object
 164                                 //
 165                                 if (expr_type.IsPointer)
 166                                         return null;
 167
 168                                 if (TypeManager.IsValueType (expr_type))
 169                                         return new BoxedCast (expr);
 170                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
 171                                         if (expr_type == TypeManager.anonymous_method_type)
 172                                                 return null;
 173                                         return new EmptyCast (expr, target_type);
 174                                 }
 175
 176                                 return null;
 177                         } else if (target_type == TypeManager.value_type) {
 178                                 if (TypeManager.IsValueType (expr_type))
 179                                         return new BoxedCast (expr);
 180                                 if (expr_type == TypeManager.null_type)
 181                                         return new NullCast (expr, target_type);
 182
 183                                 return null;
 184                         } else if (TypeManager.IsSubclassOf (expr_type, target_type)) {
 185                                 //
 186                                 // Special case: enumeration to System.Enum.
 187                                 // System.Enum is not a value type, it is a class, so we need
 188                                 // a boxing conversion
 189                                 //
 190                                 if (expr_type.IsEnum || expr_type.IsGenericParameter)
 191                                         return new BoxedCast (expr);
 192
 193                                 return new EmptyCast (expr, target_type);
 194                         }
 195
 196                         // This code is kind of mirrored inside WideningStandardConversionExists
 197                         // with the small distinction that we only probe there
 198                         //
 199                         // Always ensure that the code here and there is in sync
 200
 201                         // from the null type to any reference-type.
 202                         if (expr_type == TypeManager.null_type){
 203                                 if (target_type.IsPointer)
 204                                         return new EmptyCast (expr, target_type);
 205
 206                                 if (!target_type.IsValueType)
 207                                         return new NullCast (expr, target_type);
 208                         }
 209
 210                         // from any class-type S to any interface-type T.
 211                         if (target_type.IsInterface) {
 212                                 if (target_type != TypeManager.iconvertible_type &&
 213                                     expr_type.IsValueType && (expr is Constant) &&
 214                                     !(expr is IntLiteral || expr is BoolLiteral ||
 215                                       expr is FloatLiteral || expr is DoubleLiteral ||
 216                                       expr is LongLiteral || expr is CharLiteral ||
 217                                       expr is StringLiteral || expr is DecimalLiteral ||
 218                                       expr is UIntLiteral || expr is ULongLiteral)) {
 219                                         return null;
 220                                 }
 221
 222                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 223                                         if (expr_type.IsGenericParameter || TypeManager.IsValueType (expr_type))
 224                                                 return new BoxedCast (expr, target_type);
 225                                         else
 226                                                 return new EmptyCast (expr, target_type);
 227                                 }
 228                         }
 229
 230                         // from any interface type S to interface-type T.
 231                         if (expr_type.IsInterface && target_type.IsInterface) {
 232                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 233                                         return new EmptyCast (expr, target_type);
 234                                 else
 235                                         return null;
 236                         }
 237
 238                         // from an array-type S to an array-type of type T
 239                         if (expr_type.IsArray && target_type.IsArray) {
 240                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 241
 242                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 243
 244                                         if (MyEmptyExpr == null)
 245                                                 MyEmptyExpr = new EmptyExpression ();
 246
 247                                         MyEmptyExpr.SetType (expr_element_type);
 248                                         Type target_element_type = TypeManager.GetElementType (target_type);
 249
 250                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 251                                                 if (WideningStandardConversionExists (ConstantEC, MyEmptyExpr,
 252                                                                                       target_element_type))
 253                                                         return new EmptyCast (expr, target_type);
 254                                 }
 255                         }
 256
 257                         // from an array-type to System.Array
 258                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 259                                 return new EmptyCast (expr, target_type);
 260
 261                         // from any delegate type to System.Delegate
 262                         if ((expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type)) &&
 263                             target_type == TypeManager.delegate_type)
 264                                 return new EmptyCast (expr, target_type);
 265
 266                         // from any array-type or delegate type into System.ICloneable.
 267                         if (expr_type.IsArray ||
 268                             expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type))
 269                                 if (target_type == TypeManager.icloneable_type)
 270                                         return new EmptyCast (expr, target_type);
 271
 272                         // from a generic type definition to a generic instance.
 273                         if (TypeManager.IsEqual (expr_type, target_type))
 274                                 return new EmptyCast (expr, target_type);
 275
 276                         return null;
 277                 }
 278
 279                 //
 280                 // Tests whether an implicit reference conversion exists between expr_type
 281                 // and target_type
 282                 //
 283                 public static bool WideningReferenceConversionExists (EmitContext ec, Expression expr, Type target_type)
 284                 {
 285                         Type expr_type = expr.Type;
 286
 287                         if (expr_type.IsGenericParameter)
 288                                 return ImplicitTypeParameterConversion (ec, expr, target_type) != null;
 289
 290                         //
 291                         // This is the boxed case.
 292                         //
 293                         if (target_type == TypeManager.object_type) {
 294                                 if (expr_type.IsClass || TypeManager.IsValueType (expr_type) ||
 295                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 296                                         if (target_type != TypeManager.anonymous_method_type)
 297                                         return true;
 298
 299                                 return false;
 300                         } else if (TypeManager.IsSubclassOf (expr_type, target_type))
 301                                 return true;
 302
 303                         // Please remember that all code below actually comes
 304                         // from WideningReferenceConversion so make sure code remains in sync
 305
 306                         // from any class-type S to any interface-type T.
 307                         if (target_type.IsInterface) {
 308                                 if (target_type != TypeManager.iconvertible_type &&
 309                                     expr_type.IsValueType && (expr is Constant) &&
 310                                     !(expr is IntLiteral || expr is BoolLiteral ||
 311                                       expr is FloatLiteral || expr is DoubleLiteral ||
 312                                       expr is LongLiteral || expr is CharLiteral ||
 313                                       expr is StringLiteral || expr is DecimalLiteral ||
 314                                       expr is UIntLiteral || expr is ULongLiteral)) {
 315                                         return false;
 316                                 }
 317
 318                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 319                                         return true;
 320                         }
 321
 322                         // from any interface type S to interface-type T.
 323                         if (expr_type.IsInterface && target_type.IsInterface)
 324                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 325                                         return true;
 326
 327                         // from an array-type S to an array-type of type T
 328                         if (expr_type.IsArray && target_type.IsArray) {
 329                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 330
 331                                         Type expr_element_type = expr_type.GetElementType ();
 332
 333                                         if (MyEmptyExpr == null)
 334                                                 MyEmptyExpr = new EmptyExpression ();
 335
 336                                         MyEmptyExpr.SetType (expr_element_type);
 337                                         Type target_element_type = TypeManager.GetElementType (target_type);
 338
 339                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 340                                                 if (WideningStandardConversionExists (ConstantEC, MyEmptyExpr,
 341                                                                                       target_element_type))
 342                                                         return true;
 343                                 }
 344                         }
 345
 346                         // from an array-type to System.Array
 347                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 348                                 return true;
 349
 350                         // from any delegate type to System.Delegate
 351                         if ((expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type)) &&
 352                             target_type == TypeManager.delegate_type)
 353                                 if (target_type.IsAssignableFrom (expr_type))
 354                                         return true;
 355
 356                         // from any array-type or delegate type into System.ICloneable.
 357                         if (expr_type.IsArray ||
 358                             expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type))
 359                                 if (target_type == TypeManager.icloneable_type)
 360                                         return true;
 361
 362                         // from the null type to any reference-type.
 363                         if (expr_type == TypeManager.null_type){
 364                                 if (target_type.IsPointer)
 365                                         return true;
 366
 367                                 if (!target_type.IsValueType)
 368                                         return true;
 369                         }
 370
 371                         // from a generic type definition to a generic instance.
 372                         if (TypeManager.IsEqual (expr_type, target_type))
 373                                 return true;
 374
 375                         return false;
 376                 }
 377
 378                 /// <summary>
 379                 ///   Implicit Numeric Conversions.
 380                 ///
 381                 ///   expr is the expression to convert, returns a new expression of type
 382                 ///   target_type or null if an implicit conversion is not possible.
 383                 /// </summary>
 384
 385                 static public Expression WideningNumericConversion (EmitContext ec, Expression expr,
 386                                                                     Type target_type, Location loc)
 387                 {
 388                         Type expr_type = expr.Type;
 389
 390                         //
 391                         // Attempt to do the implicit constant expression conversions
 392
 393                         if (expr is Constant){
 394                                 if (expr is IntConstant){
 395                                         Expression e;
 396
 397                                         e = TryWideningIntConversion (target_type, (IntConstant) expr);
 398
 399                                         if (e != null)
 400                                                 return e;
 401                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 402                                         //
 403                                         // Try the implicit constant expression conversion
 404                                         // from long to ulong, instead of a nice routine,
 405                                         // we just inline it
 406                                         //
 407                                         long v = ((LongConstant) expr).Value;
 408                                         if (v >= 0)
 409                                                 return new ULongConstant ((ulong) v);
 410                                 }
 411                         }
 412
 413                         Type real_target_type = target_type;
 414
 415                          if (expr_type == TypeManager.byte_type){
 416                                 //
 417                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 418                                 //
 419                                 if ((real_target_type == TypeManager.short_type) ||
 420                                     (real_target_type == TypeManager.int32_type))
 421                                         return new EmptyCast (expr, target_type);
 422
 423                                 if (real_target_type == TypeManager.int64_type)
 424                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 425                                 if (real_target_type == TypeManager.float_type)
 426                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 427                                 if (real_target_type == TypeManager.double_type)
 428                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 429                                 if (real_target_type == TypeManager.decimal_type)
 430                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 431                         } else if (expr_type == TypeManager.short_type){
 432                                 //
 433                                 // From short to int, long, float, double
 434                                 //
 435                                 if (real_target_type == TypeManager.int32_type)
 436                                         return new EmptyCast (expr, target_type);
 437                                 if (real_target_type == TypeManager.int64_type)
 438                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 439                                 if (real_target_type == TypeManager.double_type)
 440                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 441                                 if (real_target_type == TypeManager.float_type)
 442                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 443                                 if (real_target_type == TypeManager.decimal_type)
 444                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 445                         } else if (expr_type == TypeManager.int32_type){
 446                                 //
 447                                 // From int to long, float, double
 448                                 //
 449                                 if (real_target_type == TypeManager.int64_type)
 450                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 451                                 if (real_target_type == TypeManager.double_type)
 452                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 453                                 if (real_target_type == TypeManager.float_type)
 454                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 455                                 if (real_target_type == TypeManager.decimal_type)
 456                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 457                         } else if (expr_type == TypeManager.int64_type){
 458                                 //
 459                                 // From long/ulong to float, double
 460                                 //
 461                                 if (real_target_type == TypeManager.double_type)
 462                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 463                                 if (real_target_type == TypeManager.float_type)
 464                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 465                                 if (real_target_type == TypeManager.decimal_type)
 466                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 467                         } else if (expr_type == TypeManager.decimal_type){
 468                                 //
 469                                 // From decimal to float, double
 470                                 //
 471                                 if (real_target_type == TypeManager.double_type)
 472                                         return new ImplicitInvocation (ec, "System", "Convert", "ToDouble", loc, expr);
 473                                 if (real_target_type == TypeManager.float_type)
 474                                         return new ImplicitInvocation (ec, "System", "Convert" ,"ToSingle", loc, expr);
 475                         } else if (expr_type == TypeManager.float_type){
 476                                 //
 477                                 // float to double
 478                                 //
 479                                 if (real_target_type == TypeManager.double_type)
 480                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 481                         }
 482
 483                         return null;
 484                 }
 485
 486
 487                 /// <summary>
 488                 ///  Same as WideningStandardConversionExists except that it also looks at
 489                 ///  implicit user defined conversions - needed for overload resolution
 490                 /// </summary>
 491                 public static bool WideningConversionExists (EmitContext ec, Expression expr, Type target_type)
 492                 {
 493                         if ((expr is NullLiteral) && target_type.IsGenericParameter)
 494                                 return TypeParameter_to_Null (target_type);
 495
 496                         if (WideningStandardConversionExists (ec, expr, target_type))
 497                                 return true;
 498
 499                         //
 500                         // VB.NET has no notion of User defined conversions
 501                         //
 502
 503 //                      Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 504
 505 //                      if (dummy != null)
 506 //                              return true;
 507
 508                         return false;
 509                 }
 510
 511                 //
 512                 // VB.NET has no notion of User defined conversions
 513                 //
 514
 515 //              public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 516 //              {
 517 //                      Expression dummy = ImplicitUserConversion (
 518 //                              ec, new EmptyExpression (source), target, Location.Null);
 519 //                      return dummy != null;
 520 //              }
 521
 522                 /// <summary>
 523                 ///  Determines if a standard implicit conversion exists from
 524                 ///  expr_type to target_type
 525                 ///
 526                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 527                 /// </summary>
 528                 public static bool WideningStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 529                 {
 530                         Type expr_type = expr.Type;
 531
 532                         if (expr_type == TypeManager.void_type)
 533                                 return false;
 534
 535                         //Console.WriteLine ("Expr is {0}", expr);
 536                         //Console.WriteLine ("{0} -> {1} ?", expr_type, target_type);
 537                         if (expr_type.Equals (target_type))
 538                                 return true;
 539
 540
 541                         // First numeric conversions
 542
 543                         if (expr_type == TypeManager.sbyte_type){
 544                                 //
 545                                 // From sbyte to short, int, long, float, double.
 546                                 //
 547                                 if ((target_type == TypeManager.int32_type) ||
 548                                     (target_type == TypeManager.int64_type) ||
 549                                     (target_type == TypeManager.double_type) ||
 550                                     (target_type == TypeManager.float_type)  ||
 551                                     (target_type == TypeManager.short_type) ||
 552                                     (target_type == TypeManager.decimal_type))
 553                                         return true;
 554
 555                         } else if (expr_type == TypeManager.byte_type){
 556                                 //
 557                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 558                                 //
 559                                 if ((target_type == TypeManager.short_type) ||
 560                                     (target_type == TypeManager.ushort_type) ||
 561                                     (target_type == TypeManager.int32_type) ||
 562                                     (target_type == TypeManager.uint32_type) ||
 563                                     (target_type == TypeManager.uint64_type) ||
 564                                     (target_type == TypeManager.int64_type) ||
 565                                     (target_type == TypeManager.float_type) ||
 566                                     (target_type == TypeManager.double_type) ||
 567                                     (target_type == TypeManager.decimal_type))
 568                                         return true;
 569
 570                         } else if (expr_type == TypeManager.short_type){
 571                                 //
 572                                 // From short to int, long, float, double
 573                                 //
 574                                 if ((target_type == TypeManager.int32_type) ||
 575                                     (target_type == TypeManager.int64_type) ||
 576                                     (target_type == TypeManager.double_type) ||
 577                                     (target_type == TypeManager.float_type) ||
 578                                     (target_type == TypeManager.decimal_type))
 579                                         return true;
 580
 581                         } else if (expr_type == TypeManager.ushort_type){
 582                                 //
 583                                 // From ushort to int, uint, long, ulong, float, double
 584                                 //
 585                                 if ((target_type == TypeManager.uint32_type) ||
 586                                     (target_type == TypeManager.uint64_type) ||
 587                                     (target_type == TypeManager.int32_type) ||
 588                                     (target_type == TypeManager.int64_type) ||
 589                                     (target_type == TypeManager.double_type) ||
 590                                     (target_type == TypeManager.float_type) ||
 591                                     (target_type == TypeManager.decimal_type))
 592                                         return true;
 593
 594                         } else if (expr_type == TypeManager.int32_type){
 595                                 //
 596                                 // From int to long, float, double
 597                                 //
 598                                 if ((target_type == TypeManager.int64_type) ||
 599                                     (target_type == TypeManager.double_type) ||
 600                                     (target_type == TypeManager.float_type) ||
 601                                     (target_type == TypeManager.decimal_type))
 602                                         return true;
 603
 604                         } else if (expr_type == TypeManager.uint32_type){
 605                                 //
 606                                 // From uint to long, ulong, float, double
 607                                 //
 608                                 if ((target_type == TypeManager.int64_type) ||
 609                                     (target_type == TypeManager.uint64_type) ||
 610                                     (target_type == TypeManager.double_type) ||
 611                                     (target_type == TypeManager.float_type) ||
 612                                     (target_type == TypeManager.decimal_type))
 613                                         return true;
 614
 615                         } else if ((expr_type == TypeManager.uint64_type) ||
 616                                    (expr_type == TypeManager.int64_type)) {
 617                                 //
 618                                 // From long/ulong to float, double
 619                                 //
 620                                 if ((target_type == TypeManager.double_type) ||
 621                                     (target_type == TypeManager.float_type) ||
 622                                     (target_type == TypeManager.decimal_type))
 623                                         return true;
 624
 625                         } else if (expr_type == TypeManager.char_type){
 626                                 //
 627                                 // From char to ushort, int, uint, long, ulong, float, double
 628                                 //
 629                                 if ((target_type == TypeManager.ushort_type) ||
 630                                     (target_type == TypeManager.int32_type) ||
 631                                     (target_type == TypeManager.uint32_type) ||
 632                                     (target_type == TypeManager.uint64_type) ||
 633                                     (target_type == TypeManager.int64_type) ||
 634                                     (target_type == TypeManager.float_type) ||
 635                                     (target_type == TypeManager.double_type) ||
 636                                     (target_type == TypeManager.decimal_type))
 637                                         return true;
 638
 639                         } else if (expr_type == TypeManager.float_type){
 640                                 //
 641                                 // float to double
 642                                 //
 643                                 if (target_type == TypeManager.double_type)
 644                                         return true;
 645                         }
 646
 647                         if (expr.eclass == ExprClass.MethodGroup){
 648                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 649                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 650                                         if (mg != null){
 651                                                 //
 652                                                 // This should not happen frequently, so we can create an object
 653                                                 // to test compatibility
 654                                                 //
 655                                                 Expression c = ImplicitDelegateCreation.Create (ec, mg, target_type, Location.Null);
 656                                                 return c != null;
 657                                         }
 658                                 }
 659                         }
 660
 661                         if (WideningReferenceConversionExists (ec, expr, target_type))
 662                                 return true;
 663
 664                         //
 665                         // Implicit Constant Expression Conversions
 666                         //
 667                         if (expr is IntConstant){
 668                                 int value = ((IntConstant) expr).Value;
 669
 670                                 if (target_type == TypeManager.sbyte_type){
 671                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 672                                                 return true;
 673                                 } else if (target_type == TypeManager.byte_type){
 674                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 675                                                 return true;
 676                                 } else if (target_type == TypeManager.short_type){
 677                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 678                                                 return true;
 679                                 } else if (target_type == TypeManager.ushort_type){
 680                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 681                                                 return true;
 682                                 } else if (target_type == TypeManager.uint32_type){
 683                                         if (value >= 0)
 684                                                 return true;
 685                                 } else if (target_type == TypeManager.uint64_type){
 686                                          //
 687                                          // we can optimize this case: a positive int32
 688                                          // always fits on a uint64.  But we need an opcode
 689                                          // to do it.
 690                                          //
 691                                         if (value >= 0)
 692                                                 return true;
 693                                 }
 694
 695                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 696                                         return true;
 697                         }
 698
 699                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 700                                 //
 701                                 // Try the implicit constant expression conversion
 702                                 // from long to ulong, instead of a nice routine,
 703                                 // we just inline it
 704                                 //
 705                                 long v = ((LongConstant) expr).Value;
 706                                 if (v > 0)
 707                                         return true;
 708                         }
 709
 710                         if ((target_type == TypeManager.enum_type ||
 711                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 712                              expr is IntLiteral){
 713                                 IntLiteral i = (IntLiteral) expr;
 714
 715                                 if (i.Value == 0)
 716                                         return true;
 717                         }
 718
 719                         //
 720                         // If `expr_type' implements `target_type' (which is an iface)
 721                         // see TryWideningIntConversion
 722                         //
 723                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 724                                 return true;
 725
 726                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 727                                 return true;
 728
 729                         if (expr_type == TypeManager.anonymous_method_type){
 730                                 if (!TypeManager.IsDelegateType (target_type))
 731                                         return false;
 732
 733                                 AnonymousMethod am = (AnonymousMethod) expr;
 734
 735                                 Expression conv = am.Compatible (ec, target_type, true);
 736                                 if (conv != null)
 737                                         return true;
 738                         }
 739
 740                         return false;
 741                 }
 742
 743                 //
 744                 // Used internally by FindMostEncompassedType, this is used
 745                 // to avoid creating lots of objects in the tight loop inside
 746                 // FindMostEncompassedType
 747                 //
 748                 static EmptyExpression priv_fmet_param;
 749
 750                 /// <summary>
 751                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 752                 ///  amongst the methods in the MethodGroupExpr
 753                 /// </summary>
 754                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 755                 {
 756                         Type best = null;
 757
 758                         if (priv_fmet_param == null)
 759                                 priv_fmet_param = new EmptyExpression ();
 760
 761                         foreach (Type t in types){
 762                                 priv_fmet_param.SetType (t);
 763
 764                                 if (best == null) {
 765                                         best = t;
 766                                         continue;
 767                                 }
 768
 769                                 if (WideningStandardConversionExists (ec, priv_fmet_param, best))
 770                                         best = t;
 771                         }
 772
 773                         return best;
 774                 }
 775
 776                 //
 777                 // Used internally by FindMostEncompassingType, this is used
 778                 // to avoid creating lots of objects in the tight loop inside
 779                 // FindMostEncompassingType
 780                 //
 781                 static EmptyExpression priv_fmee_ret;
 782
 783                 /// <summary>
 784                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 785                 ///  amongst the types in the given set
 786                 /// </summary>
 787                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 788                 {
 789                         Type best = null;
 790
 791                         if (priv_fmee_ret == null)
 792                                 priv_fmee_ret = new EmptyExpression ();
 793
 794                         foreach (Type t in types){
 795                                 priv_fmee_ret.SetType (best);
 796
 797                                 if (best == null) {
 798                                         best = t;
 799                                         continue;
 800                                 }
 801
 802                                 if (WideningStandardConversionExists (ec, priv_fmee_ret, t))
 803                                         best = t;
 804                         }
 805
 806                         return best;
 807                 }
 808
 809                 //
 810                 // Used to avoid creating too many objects
 811                 //
 812                 static EmptyExpression priv_fms_expr;
 813
 814                 /// <summary>
 815                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 816                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 817                 ///   for explicit and implicit conversion operators.
 818                 /// </summary>
 819                 static public Type FindMostSpecificSource (EmitContext ec, MethodGroupExpr me,
 820                                                            Expression source, bool apply_explicit_conv_rules,
 821                                                            Location loc)
 822                 {
 823                         ArrayList src_types_set = new ArrayList ();
 824
 825                         if (priv_fms_expr == null)
 826                                 priv_fms_expr = new EmptyExpression ();
 827
 828                         //
 829                         // If any operator converts from S then Sx = S
 830                         //
 831                         Type source_type = source.Type;
 832                         foreach (MethodBase mb in me.Methods){
 833                                 ParameterData pd = Invocation.GetParameterData (mb);
 834                                 Type param_type = pd.ParameterType (0);
 835
 836                                 if (param_type == source_type)
 837                                         return param_type;
 838
 839                                 if (apply_explicit_conv_rules) {
 840                                         //
 841                                         // From the spec :
 842                                         // Find the set of applicable user-defined conversion operators, U.  This set
 843                                         // consists of the
 844                                         // user-defined implicit or explicit conversion operators declared by
 845                                         // the classes or structs in D that convert from a type encompassing
 846                                         // or encompassed by S to a type encompassing or encompassed by T
 847                                         //
 848                                         priv_fms_expr.SetType (param_type);
 849                                         if (WideningStandardConversionExists (ec, priv_fms_expr, source_type))
 850                                                 src_types_set.Add (param_type);
 851                                         else {
 852                                                 if (WideningStandardConversionExists (ec, source, param_type))
 853                                                         src_types_set.Add (param_type);
 854                                         }
 855                                 } else {
 856                                         //
 857                                         // Only if S is encompassed by param_type
 858                                         //
 859                                         if (WideningStandardConversionExists (ec, source, param_type))
 860                                                 src_types_set.Add (param_type);
 861                                 }
 862                         }
 863
 864                         //
 865                         // Explicit Conv rules
 866                         //
 867                         if (apply_explicit_conv_rules) {
 868                                 ArrayList candidate_set = new ArrayList ();
 869
 870                                 foreach (Type param_type in src_types_set){
 871                                         if (WideningStandardConversionExists (ec, source, param_type))
 872                                                 candidate_set.Add (param_type);
 873                                 }
 874
 875                                 if (candidate_set.Count != 0)
 876                                         return FindMostEncompassedType (ec, candidate_set);
 877                         }
 878
 879                         //
 880                         // Final case
 881                         //
 882                         if (apply_explicit_conv_rules)
 883                                 return FindMostEncompassingType (ec, src_types_set);
 884                         else
 885                                 return FindMostEncompassedType (ec, src_types_set);
 886                 }
 887
 888                 //
 889                 // Useful in avoiding proliferation of objects
 890                 //
 891                 static EmptyExpression priv_fmt_expr;
 892
 893                 /// <summary>
 894                 ///  Finds the most specific target Tx according to section 13.4.4
 895                 /// </summary>
 896                 static public Type FindMostSpecificTarget (EmitContext ec, MethodGroupExpr me,
 897                                                            Type target, bool apply_explicit_conv_rules,
 898                                                            Location loc)
 899                 {
 900                         ArrayList tgt_types_set = new ArrayList ();
 901
 902                         if (priv_fmt_expr == null)
 903                                 priv_fmt_expr = new EmptyExpression ();
 904
 905                         //
 906                         // If any operator converts to T then Tx = T
 907                         //
 908                         foreach (MethodInfo mi in me.Methods){
 909                                 Type ret_type = mi.ReturnType;
 910
 911                                 if (ret_type == target)
 912                                         return ret_type;
 913
 914                                 if (apply_explicit_conv_rules) {
 915                                         //
 916                                         // From the spec :
 917                                         // Find the set of applicable user-defined conversion operators, U.
 918                                         //
 919                                         // This set consists of the
 920                                         // user-defined implicit or explicit conversion operators declared by
 921                                         // the classes or structs in D that convert from a type encompassing
 922                                         // or encompassed by S to a type encompassing or encompassed by T
 923                                         //
 924                                         priv_fms_expr.SetType (ret_type);
 925                                         if (WideningStandardConversionExists (ec, priv_fms_expr, target))
 926                                                 tgt_types_set.Add (ret_type);
 927                                         else {
 928                                                 priv_fms_expr.SetType (target);
 929                                                 if (WideningStandardConversionExists (ec, priv_fms_expr, ret_type))
 930                                                         tgt_types_set.Add (ret_type);
 931                                         }
 932                                 } else {
 933                                         //
 934                                         // Only if T is encompassed by param_type
 935                                         //
 936                                         priv_fms_expr.SetType (ret_type);
 937                                         if (WideningStandardConversionExists (ec, priv_fms_expr, target))
 938                                                 tgt_types_set.Add (ret_type);
 939                                 }
 940                         }
 941
 942                         //
 943                         // Explicit conv rules
 944                         //
 945                         if (apply_explicit_conv_rules) {
 946                                 ArrayList candidate_set = new ArrayList ();
 947
 948                                 foreach (Type ret_type in tgt_types_set){
 949                                         priv_fmt_expr.SetType (ret_type);
 950
 951                                         if (WideningStandardConversionExists (ec, priv_fmt_expr, target))
 952                                                 candidate_set.Add (ret_type);
 953                                 }
 954
 955                                 if (candidate_set.Count != 0)
 956                                         return FindMostEncompassingType (ec, candidate_set);
 957                         }
 958
 959                         //
 960                         // Okay, final case !
 961                         //
 962                         if (apply_explicit_conv_rules)
 963                                 return FindMostEncompassedType (ec, tgt_types_set);
 964                         else
 965                                 return FindMostEncompassingType (ec, tgt_types_set);
 966                 }
 967
 968                 /// <summary>
 969                 ///  User-defined Implicit conversions
 970                 /// </summary>
 971
 972                 //
 973                 // VB.NET has no notion of User defined conversions
 974                 //
 975
 976 //              static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 977 //                                                               Type target, Location loc)
 978 //              {
 979 //                      return UserDefinedConversion (ec, source, target, loc, false);
 980 //              }
 981
 982                 /// <summary>
 983                 ///  User-defined Explicit conversions
 984                 /// </summary>
 985
 986                 //
 987                 // VB.NET has no notion of User defined conversions
 988                 //
 989
 990 //              static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 991 //                                                               Type target, Location loc)
 992 //              {
 993 //                      return UserDefinedConversion (ec, source, target, loc, true);
 994 //              }
 995
 996                 static DoubleHash explicit_conv = new DoubleHash (100);
 997                 static DoubleHash implicit_conv = new DoubleHash (100);
 998                 /// <summary>
 999                 ///   Computes the MethodGroup for the user-defined conversion
1000                 ///   operators from source_type to target_type.  `look_for_explicit'
1001                 ///   controls whether we should also include the list of explicit
1002                 ///   operators
1003                 /// </summary>
1004                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
1005                                                                Type source_type, Type target_type,
1006                                                                Location loc, bool look_for_explicit)
1007                 {
1008                         Expression mg1 = null, mg2 = null;
1009                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
1010                         string op_name;
1011
1012                         op_name = "op_Implicit";
1013
1014                         MethodGroupExpr union3;
1015                         object r;
1016                         if ((look_for_explicit ? explicit_conv : implicit_conv).Lookup (source_type, target_type, out r))
1017                                 return (MethodGroupExpr) r;
1018
1019                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
1020                         if (source_type.BaseType != null)
1021                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
1022
1023                         if (mg1 == null)
1024                                 union3 = (MethodGroupExpr) mg2;
1025                         else if (mg2 == null)
1026                                 union3 = (MethodGroupExpr) mg1;
1027                         else
1028                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
1029
1030                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
1031                         if (mg1 != null){
1032                                 if (union3 != null)
1033                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
1034                                 else
1035                                         union3 = (MethodGroupExpr) mg1;
1036                         }
1037
1038                         if (target_type.BaseType != null)
1039                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
1040
1041                         if (mg1 != null){
1042                                 if (union3 != null)
1043                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
1044                                 else
1045                                         union3 = (MethodGroupExpr) mg1;
1046                         }
1047
1048                         MethodGroupExpr union4 = null;
1049
1050                         if (look_for_explicit) {
1051                                 op_name = "op_Explicit";
1052
1053                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
1054                                 if (source_type.BaseType != null)
1055                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
1056
1057                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
1058                                 if (target_type.BaseType != null)
1059                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
1060
1061                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
1062                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
1063
1064                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
1065                         }
1066
1067                         MethodGroupExpr ret = Invocation.MakeUnionSet (union3, union4, loc);
1068                         (look_for_explicit ? explicit_conv : implicit_conv).Insert (source_type, target_type, ret);
1069                         return ret;
1070                 }
1071
1072                 /// <summary>
1073                 ///   User-defined conversions
1074                 /// </summary>
1075
1076                 //
1077                 // VB.NET has no notion of User defined conversions. This method is not used.
1078                 //
1079                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
1080                                                                 Type target, Location loc,
1081                                                                 bool look_for_explicit)
1082                 {
1083                         MethodGroupExpr union;
1084                         Type source_type = source.Type;
1085                         MethodBase method = null;
1086
1087                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
1088                         if (union == null)
1089                                 return null;
1090
1091                         Type most_specific_source, most_specific_target;
1092
1093                         most_specific_source = FindMostSpecificSource (ec, union, source, look_for_explicit, loc);
1094                         if (most_specific_source == null)
1095                                 return null;
1096
1097                         most_specific_target = FindMostSpecificTarget (ec, union, target, look_for_explicit, loc);
1098                         if (most_specific_target == null)
1099                                 return null;
1100
1101                         int count = 0;
1102
1103
1104                         foreach (MethodBase mb in union.Methods){
1105                                 ParameterData pd = Invocation.GetParameterData (mb);
1106                                 MethodInfo mi = (MethodInfo) mb;
1107
1108                                 if (pd.ParameterType (0) == most_specific_source &&
1109                                     mi.ReturnType == most_specific_target) {
1110                                         method = mb;
1111                                         count++;
1112                                 }
1113                         }
1114
1115                         if (method == null || count > 1)
1116                                 return null;
1117
1118
1119                         //
1120                         // This will do the conversion to the best match that we
1121                         // found.  Now we need to perform an implict standard conversion
1122                         // if the best match was not the type that we were requested
1123                         // by target.
1124                         //
1125                         if (look_for_explicit)
1126                                 source = WideningAndNarrowingConversionStandard (ec, source, most_specific_source, loc);
1127                         else
1128                                 source = WideningConversionStandard (ec, source, most_specific_source, loc);
1129
1130                         if (source == null)
1131                                 return null;
1132
1133                         Expression e;
1134                         e =  new UserCast ((MethodInfo) method, source, loc);
1135                         if (e.Type != target){
1136                                 if (!look_for_explicit)
1137                                         e = WideningConversionStandard (ec, e, target, loc);
1138                                 else
1139                                         e = WideningAndNarrowingConversionStandard (ec, e, target, loc);
1140                         }
1141
1142                         return e;
1143                 }
1144
1145                 /// <summary>
1146                 ///   Converts implicitly the resolved expression `expr' into the
1147                 ///   `target_type'.  It returns a new expression that can be used
1148                 ///   in a context that expects a `target_type'.
1149                 /// </summary>
1150                 static public Expression WideningConversion (EmitContext ec, Expression expr,
1151                                                              Type target_type, Location loc)
1152                 {
1153                         Expression e;
1154
1155                         if (target_type == null)
1156                                 throw new Exception ("Target type is null");
1157
1158                         e = WideningConversionStandard (ec, expr, target_type, loc);
1159                         if (e != null)
1160                                 return e;
1161
1162                         //
1163                         // VB.NET has no notion of User defined conversions
1164                         //
1165
1166 //                      e = ImplicitUserConversion (ec, expr, target_type, loc);
1167 //                      if (e != null)
1168 //                              return e;
1169
1170                         return null;
1171                 }
1172
1173
1174                 /// <summary>
1175                 ///   Attempts to apply the `Standard Implicit
1176                 ///   Conversion' rules to the expression `expr' into
1177                 ///   the `target_type'.  It returns a new expression
1178                 ///   that can be used in a context that expects a
1179                 ///   `target_type'.
1180                 ///
1181                 ///   This is different from `WideningConversion' in that the
1182                 ///   user defined implicit conversions are excluded.
1183                 /// </summary>
1184                 static public Expression WideningConversionStandard (EmitContext ec, Expression expr,
1185                                                                      Type target_type, Location loc)
1186                 {
1187                         Type expr_type = expr.Type;
1188                         Expression e;
1189
1190                         if ((expr is NullLiteral) && target_type.IsGenericParameter)
1191                                 return TypeParameter_to_Null (expr, target_type, loc);
1192
1193                         if (expr.eclass == ExprClass.MethodGroup){
1194                                 if (!TypeManager.IsDelegateType (target_type)){
1195                                         return null;
1196                                 }
1197
1198                                 //
1199                                 // Only allow anonymous method conversions on post ISO_1
1200                                 //
1201                                 if (RootContext.Version != LanguageVersion.ISO_1){
1202                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1203                                         if (mg != null)
1204                                                 return ImplicitDelegateCreation.Create (ec, mg, target_type, loc);
1205                                 }
1206                         }
1207
1208                         if (expr_type.Equals (target_type) && !TypeManager.IsNullType (expr_type))
1209                                 return expr;
1210
1211                         e = WideningNumericConversion (ec, expr, target_type, loc);
1212                         if (e != null)
1213                                 return e;
1214
1215                         e = WideningReferenceConversion (ec, expr, target_type);
1216                         if (e != null)
1217                                 return e;
1218
1219                         if ((target_type == TypeManager.enum_type ||
1220                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1221                             expr is IntLiteral){
1222                                 IntLiteral i = (IntLiteral) expr;
1223
1224                                 if (i.Value == 0)
1225                                         return new EnumConstant ((Constant) expr, target_type);
1226                         }
1227
1228                         if (ec.InUnsafe) {
1229                                 if (expr_type.IsPointer){
1230                                         if (target_type == TypeManager.void_ptr_type)
1231                                                 return new EmptyCast (expr, target_type);
1232
1233                                         //
1234                                         // yep, comparing pointer types cant be done with
1235                                         // t1 == t2, we have to compare their element types.
1236                                         //
1237                                         if (target_type.IsPointer){
1238                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1239                                                         return expr;
1240                                         }
1241                                 }
1242
1243                                 if (target_type.IsPointer) {
1244                                         if (expr_type == TypeManager.null_type)
1245                                                 return new EmptyCast (expr, target_type);
1246
1247                                         if (expr_type == TypeManager.void_ptr_type)
1248                                                 return new EmptyCast (expr, target_type);
1249                                 }
1250                         }
1251
1252                         if (expr_type == TypeManager.anonymous_method_type){
1253                                 if (!TypeManager.IsDelegateType (target_type)){
1254                                         Report.Error (1660, loc,
1255                                                               "Cannot convert anonymous method to `{0}', since it is not a delegate",
1256                                                               TypeManager.CSharpName (target_type));
1257                                         return null;
1258                                 }
1259
1260                                 AnonymousMethod am = (AnonymousMethod) expr;
1261                                 int errors = Report.Errors;
1262
1263                                 Expression conv = am.Compatible (ec, target_type, false);
1264                                 if (conv != null)
1265                                         return conv;
1266
1267                                 //
1268                                 // We return something instead of null, to avoid
1269                                 // the duplicate error, since am.Compatible would have
1270                                 // reported that already
1271                                 //
1272                                 if (errors != Report.Errors)
1273                                         return new EmptyCast (expr, target_type);
1274                         }
1275
1276                         //
1277                         // VB.NET specific conversions
1278                         //
1279
1280                         e = WideningStringConversions (ec, expr, target_type, loc);
1281                         if (e != null)
1282                                 return e;
1283
1284
1285                         return null;
1286                 }
1287
1288                 /// <summary>
1289                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1290                 ///   into a different data type using casts (See Implicit Constant
1291                 ///   Expression Conversions)
1292                 /// </summary>
1293                 static public Expression TryWideningIntConversion (Type target_type, IntConstant ic)
1294                 {
1295                         int value = ic.Value;
1296
1297                         if (target_type == TypeManager.sbyte_type){
1298                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1299                                         return new SByteConstant ((sbyte) value);
1300                         } else if (target_type == TypeManager.byte_type){
1301                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1302                                         return new ByteConstant ((byte) value);
1303                         } else if (target_type == TypeManager.short_type){
1304                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1305                                         return new ShortConstant ((short) value);
1306                         } else if (target_type == TypeManager.ushort_type){
1307                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1308                                         return new UShortConstant ((ushort) value);
1309                         } else if (target_type == TypeManager.uint32_type){
1310                                 if (value >= 0)
1311                                         return new UIntConstant ((uint) value);
1312                         } else if (target_type == TypeManager.uint64_type){
1313                                 //
1314                                 // we can optimize this case: a positive int32
1315                                 // always fits on a uint64.  But we need an opcode
1316                                 // to do it.
1317                                 //
1318                                 if (value >= 0)
1319                                         return new ULongConstant ((ulong) value);
1320                         } else if (target_type == TypeManager.double_type)
1321                                 return new DoubleConstant ((double) value);
1322                         else if (target_type == TypeManager.float_type)
1323                                 return new FloatConstant ((float) value);
1324
1325                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1326                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1327                                 Constant e = (Constant) ic;
1328
1329                                 //
1330                                 // Possibly, we need to create a different 0 literal before passing
1331                                 // to EnumConstant
1332                                 //
1333                                 if (underlying == TypeManager.int64_type)
1334                                         e = new LongLiteral (0);
1335                                 else if (underlying == TypeManager.uint64_type)
1336                                         e = new ULongLiteral (0);
1337
1338                                 return new EnumConstant (e, target_type);
1339                         }
1340
1341                         //
1342                         // If `target_type' is an interface and the type of `ic' implements the interface
1343                         // e.g. target_type is IComparable, IConvertible, IFormattable
1344                         //
1345                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1346                                 return new BoxedCast (ic);
1347
1348                         return null;
1349                 }
1350
1351                 static public void Error_CannotWideningConversion (Location loc, Type source, Type target)
1352                 {
1353                         if (source.Name == target.Name){
1354                                 Report.ExtraInformation (loc,
1355                                          String.Format (
1356                                                 "The type {0} has two conflicting definitons, one comes from {0} and the other from {1}",
1357                                                 source.Assembly.FullName, target.Assembly.FullName));
1358
1359                         }
1360                         Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
1361                                       source == TypeManager.anonymous_method_type ?
1362                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1363                                       TypeManager.CSharpName (target));
1364                 }
1365
1366                 /// <summary>
1367                 ///   Attempts to implicitly convert `source' into `target_type', using
1368                 ///   WideningConversion.  If there is no implicit conversion, then
1369                 ///   an error is signaled
1370                 /// </summary>
1371                 static public Expression WideningConversionRequired (EmitContext ec, Expression source,
1372                                                                      Type target_type, Location loc)
1373                 {
1374                         Expression e;
1375
1376                         int errors = Report.Errors;
1377                         e = WideningConversion (ec, source, target_type, loc);
1378                         if (Report.Errors > errors)
1379                                 return null;
1380                         if (e != null)
1381                                 return e;
1382
1383                         if (source is DoubleLiteral) {
1384                                 if (target_type == TypeManager.float_type) {
1385                                         Error_664 (loc, "float", "f");
1386                                         return null;
1387                                 }
1388                                 if (target_type == TypeManager.decimal_type) {
1389                                         Error_664 (loc, "decimal", "m");
1390                                         return null;
1391                                 }
1392                         }
1393
1394                         if (source is Constant){
1395                                 Constant c = (Constant) source;
1396
1397                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1398                                 return null;
1399                         }
1400
1401                         Error_CannotWideningConversion (loc, source.Type, target_type);
1402
1403                         return null;
1404                 }
1405
1406                 static void Error_664 (Location loc, string type, string suffix) {
1407                         Report.Error (664, loc,
1408                                 "Literal of type double cannot be implicitly converted to type '{0}'. Add suffix '{1}' to create a literal of this type",
1409                                 type, suffix);
1410                 }
1411
1412                 /// <summary>
1413                 ///   Performs the explicit numeric conversions
1414                 /// </summary>
1415
1416                 /// <summary>
1417                 ///   Performs the explicit numeric conversions
1418                 /// </summary>
1419                 static Expression NarrowingNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1420                 {
1421                         Type expr_type = expr.Type;
1422
1423                         //
1424                         // If we have an enumeration, extract the underlying type,
1425                         // use this during the comparison, but wrap around the original
1426                         // target_type
1427                         //
1428                         Type real_target_type = target_type;
1429
1430                         if (TypeManager.IsEnumType (real_target_type))
1431                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1432
1433                         if (WideningStandardConversionExists (ec, expr, real_target_type)){
1434                                 Expression ce = WideningConversionStandard (ec, expr, real_target_type, loc);
1435
1436                                 if (real_target_type != target_type)
1437                                         return new EmptyCast (ce, target_type);
1438                                 return ce;
1439                         }
1440
1441                         if (expr_type == TypeManager.short_type){
1442                                 //
1443                                 // From short to byte
1444                                 //
1445                                 if (real_target_type == TypeManager.byte_type)
1446                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1447                         } else if (expr_type == TypeManager.int32_type){
1448                                 //
1449                                 // From int to byte, short
1450                                 //
1451                                 if (real_target_type == TypeManager.byte_type)
1452                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1453                                 if (real_target_type == TypeManager.short_type)
1454                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1455                         } else if (expr_type == TypeManager.int64_type){
1456                                 //
1457                                 // From long to byte, short, int
1458                                 //
1459                                 if (real_target_type == TypeManager.byte_type)
1460                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1461                                 if (real_target_type == TypeManager.short_type)
1462                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1463                                 if (real_target_type == TypeManager.int32_type)
1464                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1465                         } else if (expr_type == TypeManager.decimal_type){
1466                                 //
1467                                 // From decimal to byte, short, int, long
1468                                 //
1469                                 if (real_target_type == TypeManager.byte_type)
1470                                         return new ImplicitInvocation (ec, "System", "Convert" , "ToByte", loc, expr);
1471                                 if (real_target_type == TypeManager.short_type)
1472                                         return new ImplicitInvocation (ec, "System", "Convert", "ToInt16", loc, expr);
1473                                 if (real_target_type == TypeManager.int32_type)
1474                                         return new ImplicitInvocation (ec, "System", "Convert", "ToInt32", loc, expr);
1475                                 if (real_target_type == TypeManager.int64_type)
1476                                         return new ImplicitInvocation (ec, "System", "Convert", "ToInt64", loc, expr);
1477                         } else if (expr_type == TypeManager.float_type){
1478                                 //
1479                                 // From float to byte, short, int, long, decimal
1480                                 //
1481                                 if (real_target_type == TypeManager.byte_type)
1482                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1483                                 if (real_target_type == TypeManager.short_type)
1484                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1485                                 if (real_target_type == TypeManager.int32_type)
1486                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1487                                 if (real_target_type == TypeManager.int64_type)
1488                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1489                                 if (real_target_type == TypeManager.decimal_type)
1490                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
1491                         } else if (expr_type == TypeManager.double_type){
1492                                 //
1493                                 // From double to byte, short, int, long, float, decimal
1494                                 //
1495                                 if (real_target_type == TypeManager.byte_type)
1496                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1497                                 if (real_target_type == TypeManager.short_type)
1498                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1499                                 if (real_target_type == TypeManager.int32_type)
1500                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1501                                 if (real_target_type == TypeManager.int64_type)
1502                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1503                                 if (real_target_type == TypeManager.float_type)
1504                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1505                                 if (real_target_type == TypeManager.decimal_type)
1506                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
1507                         }
1508
1509                         return null;
1510                 }
1511
1512                 /// <summary>
1513                 /// VB.NET specific: Convert to and from boolean
1514                 /// </summary>
1515
1516                 static public Expression BooleanConversions (EmitContext ec, Expression expr,
1517                                                                     Type target_type, Location loc)
1518                 {
1519                         Type expr_type = expr.Type;
1520                         Type real_target_type = target_type;
1521
1522                         if (expr_type == TypeManager.bool_type) {
1523
1524                                 //
1525                                 // From boolean to byte, short, int,
1526                                 // long, float, double, decimal
1527                                 //
1528
1529                                 if (real_target_type == TypeManager.byte_type)
1530                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_U1);
1531                                 if (real_target_type == TypeManager.short_type)
1532                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I2);
1533                                 if (real_target_type == TypeManager.int32_type)
1534                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I4);
1535                                 if (real_target_type == TypeManager.int64_type)
1536                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I8);
1537                                 if (real_target_type == TypeManager.float_type)
1538                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_R4);
1539                                 if (real_target_type == TypeManager.double_type)
1540                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_R8);
1541                                 if (real_target_type == TypeManager.decimal_type) {
1542                                         return new ImplicitInvocation (ec, "DecimalType", "FromBoolean", loc, expr);
1543                                 }
1544                         } if (real_target_type == TypeManager.bool_type) {
1545
1546                                 //
1547                                 // From byte, short, int, long, float,
1548                                 // double, decimal to boolean
1549                                 //
1550
1551                                 if (expr_type == TypeManager.byte_type ||
1552                                         expr_type == TypeManager.short_type ||
1553                                         expr_type == TypeManager.int32_type ||
1554                                         expr_type == TypeManager.int64_type ||
1555                                         expr_type == TypeManager.float_type ||
1556                                         expr_type == TypeManager.double_type)
1557                                                 return new NumericToBooleanCast (expr, expr_type);
1558                                 if (expr_type == TypeManager.decimal_type) {
1559                                         return new ImplicitInvocation (ec, "System", "Convert", "ToBoolean", loc, expr);
1560                                 }
1561                         }
1562
1563                         return null;
1564                 }
1565
1566                 /// <summary>
1567                 /// VB.NET specific: Widening conversions to string
1568                 /// </summary>
1569
1570                 static public Expression WideningStringConversions (EmitContext ec, Expression expr,
1571                                                                     Type target_type, Location loc)
1572
1573                 {
1574                         Type expr_type = expr.Type;
1575                         Type real_target_type = target_type;
1576
1577                         if (real_target_type == TypeManager.string_type) {
1578                                 //
1579                                 // From char to string
1580                                 //
1581                                 if (expr_type == TypeManager.char_type)
1582                                         return new ImplicitInvocation (ec, "StringType", "FromChar", loc, expr);
1583                         }
1584
1585                         if(expr_type.IsArray && (expr_type.GetElementType() == TypeManager.char_type)) {
1586                                 //
1587                                 // From char array to string
1588                                 //
1589                                 return new ImplicitNew (ec, "System", "String", loc, expr);
1590                         }
1591
1592                         return null;
1593                 }
1594
1595                 /// <summary>
1596                 /// VB.NET specific: Narrowing conversions involving strings
1597                 /// </summary>
1598
1599                 static public Expression NarrowingStringConversions (EmitContext ec, Expression expr,
1600                                                                     Type target_type, Location loc)
1601                 {
1602                         Type expr_type = expr.Type;
1603                         Type real_target_type = target_type;
1604
1605                         // FIXME: Need to take care of Constants
1606
1607                         if (expr_type == TypeManager.string_type) {
1608
1609                                 //
1610                                 // From string to chararray, bool,
1611                                 // byte, short, char, int, long,
1612                                 // float, double, decimal and date
1613                                 //
1614
1615                                 if (real_target_type.IsArray && (real_target_type.GetElementType() == TypeManager.char_type))
1616                                         return new ImplicitInvocation (ec, "CharArrayType", "FromString", loc, expr);
1617                                 if (real_target_type == TypeManager.bool_type)
1618                                         return new ImplicitInvocation (ec, "BooleanType", "FromString", loc, expr);
1619                                 if (real_target_type == TypeManager.byte_type)
1620                                         return new ImplicitInvocation (ec, "ByteType", "FromString", loc, expr);
1621                                 if (real_target_type == TypeManager.short_type)
1622                                         return new ImplicitInvocation (ec, "ShortType", "FromString", loc, expr);
1623                                 if (real_target_type == TypeManager.char_type)
1624                                         return new ImplicitInvocation (ec, "CharType", "FromString", loc, expr);
1625                                 if (real_target_type == TypeManager.int32_type)
1626                                         return new ImplicitInvocation (ec, "IntegerType", "FromString", loc, expr);
1627                                 if (real_target_type == TypeManager.int64_type)
1628                                         return new ImplicitInvocation (ec, "LongType", "FromString", loc, expr);
1629                                 if (real_target_type == TypeManager.float_type)
1630                                         return new ImplicitInvocation (ec, "SingleType", "FromString", loc, expr);
1631                                 if (real_target_type == TypeManager.double_type)
1632                                         return new ImplicitInvocation (ec, "DoubleType", "FromString", loc, expr);
1633                                 if (real_target_type == TypeManager.decimal_type)
1634                                         return new ImplicitInvocation (ec, "DecimalType", "FromString", loc, expr);
1635                                 if (real_target_type == TypeManager.date_type)
1636                                         return new ImplicitInvocation (ec, "DateType", "FromString", loc, expr);
1637                         } if (real_target_type == TypeManager.string_type) {
1638
1639                                 //
1640                                 // From bool, byte, short, char, int,
1641                                 // long, float, double, decimal and
1642                                 // date to string
1643                                 //
1644
1645                                 if (expr_type == TypeManager.bool_type)
1646                                         return new ImplicitInvocation (ec, "StringType", "FromBoolean", loc, expr);
1647                                 if (expr_type == TypeManager.byte_type)
1648                                         return new ImplicitInvocation (ec, "StringType", "FromByte", loc, expr);
1649                                 if (expr_type == TypeManager.short_type)
1650                                         return new ImplicitInvocation (ec, "StringType", "FromShort", loc, expr);
1651                                 if (expr_type == TypeManager.int32_type)
1652                                         return new ImplicitInvocation (ec, "StringType", "FromInteger", loc, expr);
1653                                 if (expr_type == TypeManager.int64_type)
1654                                         return new ImplicitInvocation (ec, "StringType", "FromLong", loc, expr);
1655                                 if (expr_type == TypeManager.float_type)
1656                                         return new ImplicitInvocation (ec, "StringType", "FromSingle", loc, expr);
1657                                 if (expr_type == TypeManager.double_type)
1658                                         return new ImplicitInvocation (ec, "StringType", "FromDouble", loc, expr);
1659                                 if (expr_type == TypeManager.decimal_type)
1660                                         return new ImplicitInvocation (ec, "StringType", "FromDecimal", loc, expr);
1661                                 if (expr_type == TypeManager.date_type)
1662                                         return new ImplicitInvocation (ec, "StringType", "FromDate", loc, expr);
1663                         }
1664
1665                         return null;
1666                 }
1667
1668                 /// <summary>
1669                 ///  Returns whether an explicit reference conversion can be performed
1670                 ///  from source_type to target_type
1671                 /// </summary>
1672                 public static bool NarrowingReferenceConversionExists (Type source_type, Type target_type)
1673                 {
1674                         bool target_is_type_param = target_type.IsGenericParameter;
1675                         bool target_is_value_type = target_type.IsValueType;
1676
1677                         if (source_type == target_type)
1678                                 return true;
1679
1680                         //
1681                         // From object to a generic parameter
1682                         //
1683                         if (source_type == TypeManager.object_type && target_is_type_param)
1684                                 return true;
1685
1686                         //
1687                         // From object to any reference type
1688                         //
1689                         if (source_type == TypeManager.object_type && !target_is_value_type)
1690                                 return true;
1691
1692                         //
1693                         // From any class S to any class-type T, provided S is a base class of T
1694                         //
1695                         if (TypeManager.IsSubclassOf (target_type, source_type))
1696                                 return true;
1697
1698                         //
1699                         // From any interface type S to any interface T provided S is not derived from T
1700                         //
1701                         if (source_type.IsInterface && target_type.IsInterface){
1702                                 if (!TypeManager.IsSubclassOf (target_type, source_type))
1703                                         return true;
1704                         }
1705
1706                         //
1707                         // From any class type S to any interface T, provided S is not sealed
1708                         // and provided S does not implement T.
1709                         //
1710                         if (target_type.IsInterface && !source_type.IsSealed &&
1711                             !TypeManager.ImplementsInterface (source_type, target_type))
1712                                 return true;
1713
1714                         //
1715                         // From any interface-type S to to any class type T, provided T is not
1716                         // sealed, or provided T implements S.
1717                         //
1718                         if (source_type.IsInterface &&
1719                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1720                                 return true;
1721
1722
1723                         // From an array type S with an element type Se to an array type T with an
1724                         // element type Te provided all the following are true:
1725                         //     * S and T differe only in element type, in other words, S and T
1726                         //       have the same number of dimensions.
1727                         //     * Both Se and Te are reference types
1728                         //     * An explicit referenc conversions exist from Se to Te
1729                         //
1730                         if (source_type.IsArray && target_type.IsArray) {
1731                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1732
1733                                         Type source_element_type = TypeManager.GetElementType (source_type);
1734                                         Type target_element_type = TypeManager.GetElementType (target_type);
1735
1736                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1737                                                 if (NarrowingReferenceConversionExists (source_element_type,
1738                                                                                        target_element_type))
1739                                                         return true;
1740                                 }
1741                         }
1742
1743
1744                         // From System.Array to any array-type
1745                         if (source_type == TypeManager.array_type &&
1746                             target_type.IsArray){
1747                                 return true;
1748                         }
1749
1750                         //
1751                         // From System delegate to any delegate-type
1752                         //
1753                         if (source_type == TypeManager.delegate_type &&
1754                             TypeManager.IsDelegateType (target_type))
1755                                 return true;
1756
1757                         //
1758                         // From ICloneable to Array or Delegate types
1759                         //
1760                         if (source_type == TypeManager.icloneable_type &&
1761                             (target_type == TypeManager.array_type ||
1762                              target_type == TypeManager.delegate_type))
1763                                 return true;
1764
1765                         return false;
1766                 }
1767
1768                 /// <summary>
1769                 ///   Implements Explicit Reference conversions
1770                 /// </summary>
1771                 static Expression NarrowingReferenceConversion (Expression source, Type target_type)
1772                 {
1773                         Type source_type = source.Type;
1774                         bool target_is_type_param = target_type.IsGenericParameter;
1775                         bool target_is_value_type = target_type.IsValueType;
1776
1777                         //
1778                         // From object to a generic parameter
1779                         //
1780                         if (source_type == TypeManager.object_type && target_is_type_param)
1781                                 return new UnboxCast (source, target_type);
1782
1783                         //
1784                         // From object to any reference type
1785                         //
1786                         if (source_type == TypeManager.object_type && !target_is_value_type)
1787                                 return new ClassCast (source, target_type);
1788
1789                         //
1790                         // Unboxing conversion.
1791                         //
1792                         if (((source_type == TypeManager.enum_type &&
1793                                 !(source is EmptyCast)) ||
1794                                 source_type == TypeManager.value_type) && target_is_value_type)
1795                                 return new UnboxCast (source, target_type);
1796
1797                         //
1798                         // From any class S to any class-type T, provided S is a base class of T
1799                         //
1800                         if (TypeManager.IsSubclassOf (target_type, source_type))
1801                                 return new ClassCast (source, target_type);
1802
1803                         //
1804                         // From any interface type S to any interface T provided S is not derived from T
1805                         //
1806                         if (source_type.IsInterface && target_type.IsInterface){
1807                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1808                                         return null;
1809                                 else
1810                                         return new ClassCast (source, target_type);
1811                         }
1812
1813                         //
1814                         // From any class type S to any interface T, provides S is not sealed
1815                         // and provided S does not implement T.
1816                         //
1817                         if (target_type.IsInterface && !source_type.IsSealed) {
1818                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1819                                         return null;
1820                                 else
1821                                         return new ClassCast (source, target_type);
1822
1823                         }
1824
1825                         //
1826                         // From any interface-type S to to any class type T, provided T is not
1827                         // sealed, or provided T implements S.
1828                         //
1829                         if (source_type.IsInterface) {
1830                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1831                                         if (target_type.IsClass)
1832                                                 return new ClassCast (source, target_type);
1833                                         else
1834                                                 return new UnboxCast (source, target_type);
1835                                 }
1836
1837                                 return null;
1838                         }
1839
1840                         // From an array type S with an element type Se to an array type T with an
1841                         // element type Te provided all the following are true:
1842                         //     * S and T differe only in element type, in other words, S and T
1843                         //       have the same number of dimensions.
1844                         //     * Both Se and Te are reference types
1845                         //     * An explicit referenc conversions exist from Se to Te
1846                         //
1847                         if (source_type.IsArray && target_type.IsArray) {
1848                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1849
1850                                         Type source_element_type = TypeManager.GetElementType (source_type);
1851                                         Type target_element_type = TypeManager.GetElementType (target_type);
1852
1853                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1854                                                 if (NarrowingReferenceConversionExists (source_element_type,
1855                                                                                        target_element_type))
1856                                                         return new ClassCast (source, target_type);
1857                                 }
1858                         }
1859
1860
1861                         // From System.Array to any array-type
1862                         if (source_type == TypeManager.array_type &&
1863                             target_type.IsArray) {
1864                                 return new ClassCast (source, target_type);
1865                         }
1866
1867                         //
1868                         // From System delegate to any delegate-type
1869                         //
1870                         if (source_type == TypeManager.delegate_type &&
1871                             TypeManager.IsDelegateType (target_type))
1872                                 return new ClassCast (source, target_type);
1873
1874                         //
1875                         // From ICloneable to Array or Delegate types
1876                         //
1877                         if (source_type == TypeManager.icloneable_type &&
1878                             (target_type == TypeManager.array_type ||
1879                              target_type == TypeManager.delegate_type))
1880                                 return new ClassCast (source, target_type);
1881
1882                         return null;
1883                 }
1884
1885                 /// <summary>
1886                 ///   Performs an explicit conversion of the expression `expr' whose
1887                 ///   type is expr.Type to `target_type'.
1888                 /// </summary>
1889                 static public Expression WideningAndNarrowingConversion (EmitContext ec, Expression expr,
1890                                                              Type target_type, Location loc)
1891                 {
1892                         Type expr_type = expr.Type;
1893                         Type original_expr_type = expr_type;
1894
1895                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1896                                 if (target_type == TypeManager.enum_type ||
1897                                     target_type == TypeManager.object_type) {
1898                                         if (expr is EnumConstant)
1899                                                 expr = ((EnumConstant) expr).Child;
1900                                         // We really need all these casts here .... :-(
1901                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1902                                         return new EmptyCast (expr, target_type);
1903                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1904                                            target_type.IsSubclassOf (TypeManager.enum_type))
1905                                         return new UnboxCast (expr, target_type);
1906
1907                                 //
1908                                 // Notice that we have kept the expr_type unmodified, which is only
1909                                 // used later on to
1910                                 if (expr is EnumConstant)
1911                                         expr = ((EnumConstant) expr).Child;
1912                                 else
1913                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1914                                 expr_type = expr.Type;
1915                         }
1916
1917                         int errors = Report.Errors;
1918                         Expression ne = WideningConversionStandard (ec, expr, target_type, loc);
1919                         if (Report.Errors > errors)
1920                                 return null;
1921
1922                         if (ne != null)
1923                                 return ne;
1924
1925                         ne = NarrowingNumericConversion (ec, expr, target_type, loc);
1926                         if (ne != null)
1927                                 return ne;
1928
1929                         //
1930                         // Unboxing conversion.
1931                         //
1932                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1933                                 return new UnboxCast (expr, target_type);
1934
1935                         //
1936                         // Skip the NarrowingReferenceConversion because we can not convert
1937                         // from Null to a ValueType, and ExplicitReference wont check against
1938                         // null literal explicitly
1939                         //
1940                         if (expr_type != TypeManager.null_type){
1941                                 ne = NarrowingReferenceConversion (expr, target_type);
1942                                 if (ne != null)
1943                                         return ne;
1944                         }
1945
1946                 skip_explicit:
1947                         if (ec.InUnsafe){
1948                                 if (target_type.IsPointer){
1949                                         if (expr_type.IsPointer)
1950                                                 return new EmptyCast (expr, target_type);
1951
1952                                         if (expr_type == TypeManager.sbyte_type ||
1953                                             expr_type == TypeManager.byte_type ||
1954                                             expr_type == TypeManager.short_type ||
1955                                             expr_type == TypeManager.ushort_type ||
1956                                             expr_type == TypeManager.int32_type ||
1957                                             expr_type == TypeManager.uint32_type ||
1958                                             expr_type == TypeManager.uint64_type ||
1959                                             expr_type == TypeManager.int64_type)
1960                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1961                                 }
1962                                 if (expr_type.IsPointer){
1963                                         Expression e = null;
1964
1965                                         if (target_type == TypeManager.sbyte_type)
1966                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1967                                         else if (target_type == TypeManager.byte_type)
1968                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1969                                         else if (target_type == TypeManager.short_type)
1970                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1971                                         else if (target_type == TypeManager.ushort_type)
1972                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1973                                         else if (target_type == TypeManager.int32_type)
1974                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1975                                         else if (target_type == TypeManager.uint32_type)
1976                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1977                                         else if (target_type == TypeManager.uint64_type)
1978                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1979                                         else if (target_type == TypeManager.int64_type){
1980                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1981                                         }
1982
1983                                         if (e != null){
1984                                                 Expression ci, ce;
1985
1986                                                 ci = WideningConversionStandard (ec, e, target_type, loc);
1987
1988                                                 if (ci != null)
1989                                                         return ci;
1990
1991                                                 ce = NarrowingNumericConversion (ec, e, target_type, loc);
1992                                                 if (ce != null)
1993                                                         return ce;
1994                                                 //
1995                                                 // We should always be able to go from an uint32
1996                                                 // implicitly or explicitly to the other integral
1997                                                 // types
1998                                                 //
1999                                                 throw new Exception ("Internal compiler error");
2000                                         }
2001                                 }
2002                         }
2003
2004                         //
2005                         // VB.NET specific conversions
2006                         //
2007
2008                         ne = BooleanConversions (ec, expr, target_type, loc);
2009                         if (ne != null)
2010                                 return ne;
2011
2012                         ne = NarrowingStringConversions (ec, expr, target_type, loc);
2013                         if (ne != null)
2014                                 return ne;
2015
2016
2017                         //
2018                         // VB.NET has no notion of User defined conversions
2019                         //
2020
2021 //                      ne = ExplicitUserConversion (ec, expr, target_type, loc);
2022 //                      if (ne != null)
2023 //                              return ne;
2024
2025                         if (expr is NullLiteral){
2026                                 Report.Error (37, loc, "Cannot convert null to value type `" +
2027                                               TypeManager.CSharpName (target_type) + "'");
2028                                 return null;
2029                         }
2030
2031                         Error_CannotConvertType (loc, original_expr_type, target_type);
2032                         return null;
2033                 }
2034
2035                 /// <summary>
2036                 ///   Same as WideningAndNarrowingConversion, only it doesn't include user defined conversions
2037                 /// </summary>
2038                 static public Expression WideningAndNarrowingConversionStandard (EmitContext ec, Expression expr,
2039                                                                      Type target_type, Location l)
2040                 {
2041                         int errors = Report.Errors;
2042                         Expression ne = WideningConversionStandard (ec, expr, target_type, l);
2043                         if (Report.Errors > errors)
2044                                 return null;
2045
2046                         if (ne != null)
2047                                 return ne;
2048
2049                         ne = NarrowingNumericConversion (ec, expr, target_type, l);
2050                         if (ne != null)
2051                                 return ne;
2052
2053                         ne = NarrowingReferenceConversion (expr, target_type);
2054                         if (ne != null)
2055                                 return ne;
2056
2057                         Error_CannotConvertType (l, expr.Type, target_type);
2058                         return null;
2059                 }
2060         }
2061 }