mcs/mcs/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 EmptyExpression MyEmptyExpr;
  40                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  41                 {
  42                         Type expr_type = expr.Type;
  43
  44                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  45                                 // if we are a method group, emit a warning
  46
  47                                 expr.Emit (null);
  48                         }
  49
  50                         if (expr_type == TypeManager.void_type)
  51                                 return null;
  52
  53                         //
  54                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  55                         // is an abstract class, and not really a value type, so we apply the same rules.
  56                         //
  57                         if (target_type == TypeManager.object_type) {
  58                                 //
  59                                 // A pointer type cannot be converted to object
  60                                 //
  61                                 if (expr_type.IsPointer)
  62                                         return null;
  63
  64                                 if (expr_type.IsValueType)
  65                                         return new BoxedCast (expr);
  66                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
  67                                         if (expr_type == TypeManager.anonymous_method_type)
  68                                                 return null;
  69                                         return new EmptyCast (expr, target_type);
  70                                 }
  71
  72                                 return null;
  73                         } else if (target_type == TypeManager.value_type) {
  74                                 if (expr_type.IsValueType)
  75                                         return new BoxedCast (expr);
  76                                 if (expr_type == TypeManager.null_type)
  77                                         return new NullCast (expr, target_type);
  78
  79                                 return null;
  80                         } else if (expr_type.IsSubclassOf (target_type)) {
  81                                 //
  82                                 // Special case: enumeration to System.Enum.
  83                                 // System.Enum is not a value type, it is a class, so we need
  84                                 // a boxing conversion
  85                                 //
  86                                 if (expr_type.IsEnum)
  87                                         return new BoxedCast (expr);
  88
  89                                 return new EmptyCast (expr, target_type);
  90                         }
  91
  92                         // This code is kind of mirrored inside ImplicitStandardConversionExists
  93                         // with the small distinction that we only probe there
  94                         //
  95                         // Always ensure that the code here and there is in sync
  96
  97                         // from the null type to any reference-type.
  98                         if (expr_type == TypeManager.null_type){
  99                                 if (target_type.IsPointer)
 100                                         return new EmptyCast (NullPointer.Null, target_type);
 101
 102                                 if (!target_type.IsValueType)
 103                                         return new NullCast (expr, target_type);
 104                         }
 105
 106                         // from any class-type S to any interface-type T.
 107                         if (target_type.IsInterface) {
 108                                 if (target_type != TypeManager.iconvertible_type &&
 109                                     expr_type.IsValueType && (expr is Constant) &&
 110                                     !(expr is IntLiteral || expr is BoolLiteral ||
 111                                       expr is FloatLiteral || expr is DoubleLiteral ||
 112                                       expr is LongLiteral || expr is CharLiteral ||
 113                                       expr is StringLiteral || expr is DecimalLiteral ||
 114                                       expr is UIntLiteral || expr is ULongLiteral)) {
 115                                         return null;
 116                                 }
 117
 118                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 119                                         if (expr_type.IsClass)
 120                                                 return new EmptyCast (expr, target_type);
 121                                         else if (expr_type.IsValueType)
 122                                                 return new BoxedCast (expr, target_type);
 123                                         else
 124                                                 return new EmptyCast (expr, target_type);
 125                                 }
 126                         }
 127
 128                         // from any interface type S to interface-type T.
 129                         if (expr_type.IsInterface && target_type.IsInterface) {
 130                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 131                                         return new EmptyCast (expr, target_type);
 132                                 else
 133                                         return null;
 134                         }
 135
 136                         // from an array-type S to an array-type of type T
 137                         if (expr_type.IsArray && target_type.IsArray) {
 138                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 139
 140                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 141
 142                                         if (MyEmptyExpr == null)
 143                                                 MyEmptyExpr = new EmptyExpression ();
 144
 145                                         MyEmptyExpr.SetType (expr_element_type);
 146                                         Type target_element_type = TypeManager.GetElementType (target_type);
 147
 148                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 149                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 150                                                                                       target_element_type))
 151                                                         return new EmptyCast (expr, target_type);
 152                                 }
 153                         }
 154
 155                         // from an array-type to System.Array
 156                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 157                                 return new EmptyCast (expr, target_type);
 158
 159                         // from any delegate type to System.Delegate
 160                         if ((expr_type == TypeManager.delegate_type ||
 161                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 162                             target_type == TypeManager.delegate_type)
 163                                 return new EmptyCast (expr, target_type);
 164
 165                         // from any array-type or delegate type into System.ICloneable.
 166                         if (expr_type.IsArray ||
 167                             expr_type == TypeManager.delegate_type ||
 168                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 169                                 if (target_type == TypeManager.icloneable_type)
 170                                         return new EmptyCast (expr, target_type);
 171
 172                         return null;
 173                 }
 174
 175                 //
 176                 // Tests whether an implicit reference conversion exists between expr_type
 177                 // and target_type
 178                 //
 179                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 180                 {
 181                         Type expr_type = expr.Type;
 182
 183                         //
 184                         // This is the boxed case.
 185                         //
 186                         if (target_type == TypeManager.object_type) {
 187                                 if (expr_type.IsClass || expr_type.IsValueType ||
 188                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 189                                         if (target_type != TypeManager.anonymous_method_type)
 190                                                 return true;
 191
 192                                 return false;
 193                         } else if (expr_type.IsSubclassOf (target_type))
 194                                 return true;
 195
 196                         // Please remember that all code below actually comes
 197                         // from ImplicitReferenceConversion so make sure code remains in sync
 198
 199                         // from any class-type S to any interface-type T.
 200                         if (target_type.IsInterface) {
 201                                 if (target_type != TypeManager.iconvertible_type &&
 202                                     expr_type.IsValueType && (expr is Constant) &&
 203                                     !(expr is IntLiteral || expr is BoolLiteral ||
 204                                       expr is FloatLiteral || expr is DoubleLiteral ||
 205                                       expr is LongLiteral || expr is CharLiteral ||
 206                                       expr is StringLiteral || expr is DecimalLiteral ||
 207                                       expr is UIntLiteral || expr is ULongLiteral)) {
 208                                         return false;
 209                                 }
 210
 211                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 212                                         return true;
 213                         }
 214
 215                         // from any interface type S to interface-type T.
 216                         if (expr_type.IsInterface && target_type.IsInterface)
 217                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 218                                         return true;
 219
 220                         // from an array-type S to an array-type of type T
 221                         if (expr_type.IsArray && target_type.IsArray) {
 222                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 223
 224                                         Type expr_element_type = expr_type.GetElementType ();
 225
 226                                         if (MyEmptyExpr == null)
 227                                                 MyEmptyExpr = new EmptyExpression ();
 228
 229                                         MyEmptyExpr.SetType (expr_element_type);
 230                                         Type target_element_type = TypeManager.GetElementType (target_type);
 231
 232                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 233                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 234                                                                                       target_element_type))
 235                                                         return true;
 236                                 }
 237                         }
 238
 239                         // from an array-type to System.Array
 240                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 241                                 return true;
 242
 243                         // from any delegate type to System.Delegate
 244                         if ((expr_type == TypeManager.delegate_type ||
 245                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 246                             target_type == TypeManager.delegate_type)
 247                                 if (target_type.IsAssignableFrom (expr_type))
 248                                         return true;
 249
 250                         // from any array-type or delegate type into System.ICloneable.
 251                         if (expr_type.IsArray ||
 252                             expr_type == TypeManager.delegate_type ||
 253                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 254                                 if (target_type == TypeManager.icloneable_type)
 255                                         return true;
 256
 257                         // from the null type to any reference-type.
 258                         if (expr_type == TypeManager.null_type){
 259                                 if (target_type.IsPointer)
 260                                         return true;
 261
 262                                 if (!target_type.IsValueType)
 263                                         return true;
 264                         }
 265                         return false;
 266                 }
 267
 268                 /// <summary>
 269                 ///   Implicit Numeric Conversions.
 270                 ///
 271                 ///   expr is the expression to convert, returns a new expression of type
 272                 ///   target_type or null if an implicit conversion is not possible.
 273                 /// </summary>
 274                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 275                                                                     Type target_type, Location loc)
 276                 {
 277                         Type expr_type = expr.Type;
 278
 279                         //
 280                         // Attempt to do the implicit constant expression conversions
 281
 282                         if (expr is Constant){
 283                                 if (expr is IntConstant){
 284                                         Expression e;
 285
 286                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 287
 288                                         if (e != null)
 289                                                 return e;
 290                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 291                                         //
 292                                         // Try the implicit constant expression conversion
 293                                         // from long to ulong, instead of a nice routine,
 294                                         // we just inline it
 295                                         //
 296                                         long v = ((LongConstant) expr).Value;
 297                                         if (v >= 0)
 298                                                 return new ULongConstant ((ulong) v);
 299                                 }
 300                         }
 301
 302                         Type real_target_type = target_type;
 303
 304                         if (expr_type == TypeManager.sbyte_type){
 305                                 //
 306                                 // From sbyte to short, int, long, float, double.
 307                                 //
 308                                 if (real_target_type == TypeManager.int32_type)
 309                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 310                                 if (real_target_type == TypeManager.int64_type)
 311                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 312                                 if (real_target_type == TypeManager.double_type)
 313                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 314                                 if (real_target_type == TypeManager.float_type)
 315                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 316                                 if (real_target_type == TypeManager.short_type)
 317                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 318                         } else if (expr_type == TypeManager.byte_type){
 319                                 //
 320                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 321                                 //
 322                                 if ((real_target_type == TypeManager.short_type) ||
 323                                     (real_target_type == TypeManager.ushort_type) ||
 324                                     (real_target_type == TypeManager.int32_type) ||
 325                                     (real_target_type == TypeManager.uint32_type))
 326                                         return new EmptyCast (expr, target_type);
 327
 328                                 if (real_target_type == TypeManager.uint64_type)
 329                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 330                                 if (real_target_type == TypeManager.int64_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 332                                 if (real_target_type == TypeManager.float_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 334                                 if (real_target_type == TypeManager.double_type)
 335                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 336                         } else if (expr_type == TypeManager.short_type){
 337                                 //
 338                                 // From short to int, long, float, double
 339                                 //
 340                                 if (real_target_type == TypeManager.int32_type)
 341                                         return new EmptyCast (expr, target_type);
 342                                 if (real_target_type == TypeManager.int64_type)
 343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 344                                 if (real_target_type == TypeManager.double_type)
 345                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 346                                 if (real_target_type == TypeManager.float_type)
 347                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 348                         } else if (expr_type == TypeManager.ushort_type){
 349                                 //
 350                                 // From ushort to int, uint, long, ulong, float, double
 351                                 //
 352                                 if (real_target_type == TypeManager.uint32_type)
 353                                         return new EmptyCast (expr, target_type);
 354
 355                                 if (real_target_type == TypeManager.uint64_type)
 356                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 357                                 if (real_target_type == TypeManager.int32_type)
 358                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 359                                 if (real_target_type == TypeManager.int64_type)
 360                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 361                                 if (real_target_type == TypeManager.double_type)
 362                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 363                                 if (real_target_type == TypeManager.float_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 365                         } else if (expr_type == TypeManager.int32_type){
 366                                 //
 367                                 // From int to long, float, double
 368                                 //
 369                                 if (real_target_type == TypeManager.int64_type)
 370                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 371                                 if (real_target_type == TypeManager.double_type)
 372                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 373                                 if (real_target_type == TypeManager.float_type)
 374                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 375                         } else if (expr_type == TypeManager.uint32_type){
 376                                 //
 377                                 // From uint to long, ulong, float, double
 378                                 //
 379                                 if (real_target_type == TypeManager.int64_type)
 380                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 381                                 if (real_target_type == TypeManager.uint64_type)
 382                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 383                                 if (real_target_type == TypeManager.double_type)
 384                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 385                                                                OpCodes.Conv_R8);
 386                                 if (real_target_type == TypeManager.float_type)
 387                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 388                                                                OpCodes.Conv_R4);
 389                         } else if (expr_type == TypeManager.int64_type){
 390                                 //
 391                                 // From long/ulong to float, double
 392                                 //
 393                                 if (real_target_type == TypeManager.double_type)
 394                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 395                                 if (real_target_type == TypeManager.float_type)
 396                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 397                         } else if (expr_type == TypeManager.uint64_type){
 398                                 //
 399                                 // From ulong to float, double
 400                                 //
 401                                 if (real_target_type == TypeManager.double_type)
 402                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 403                                                                OpCodes.Conv_R8);
 404                                 if (real_target_type == TypeManager.float_type)
 405                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 406                                                                OpCodes.Conv_R4);
 407                         } else if (expr_type == TypeManager.char_type){
 408                                 //
 409                                 // From char to ushort, int, uint, long, ulong, float, double
 410                                 //
 411                                 if ((real_target_type == TypeManager.ushort_type) ||
 412                                     (real_target_type == TypeManager.int32_type) ||
 413                                     (real_target_type == TypeManager.uint32_type))
 414                                         return new EmptyCast (expr, target_type);
 415                                 if (real_target_type == TypeManager.uint64_type)
 416                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 417                                 if (real_target_type == TypeManager.int64_type)
 418                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 419                                 if (real_target_type == TypeManager.float_type)
 420                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 421                                 if (real_target_type == TypeManager.double_type)
 422                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 423                         } else if (expr_type == TypeManager.float_type){
 424                                 //
 425                                 // float to double
 426                                 //
 427                                 if (real_target_type == TypeManager.double_type)
 428                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 429                         }
 430
 431                         return null;
 432                 }
 433
 434
 435                 /// <summary>
 436                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 437                 ///  implicit user defined conversions - needed for overload resolution
 438                 /// </summary>
 439                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 440                 {
 441                         if (ImplicitStandardConversionExists (ec, expr, target_type))
 442                                 return true;
 443
 444                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 445
 446                         if (dummy != null)
 447                                 return true;
 448
 449                         return false;
 450                 }
 451
 452                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 453                 {
 454                         Expression dummy = ImplicitUserConversion (
 455                                 ec, new EmptyExpression (source), target, Location.Null);
 456                         return dummy != null;
 457                 }
 458
 459                 /// <summary>
 460                 ///  Determines if a standard implicit conversion exists from
 461                 ///  expr_type to target_type
 462                 ///
 463                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 464                 /// </summary>
 465                 public static bool ImplicitStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 466                 {
 467                         Type expr_type = expr.Type;
 468
 469                         if (expr_type == TypeManager.void_type)
 470                                 return false;
 471
 472                         if (expr_type == target_type)
 473                                 return true;
 474
 475
 476                         // First numeric conversions
 477
 478                         if (expr_type == TypeManager.sbyte_type){
 479                                 //
 480                                 // From sbyte to short, int, long, float, double.
 481                                 //
 482                                 if ((target_type == TypeManager.int32_type) ||
 483                                     (target_type == TypeManager.int64_type) ||
 484                                     (target_type == TypeManager.double_type) ||
 485                                     (target_type == TypeManager.float_type)  ||
 486                                     (target_type == TypeManager.short_type) ||
 487                                     (target_type == TypeManager.decimal_type))
 488                                         return true;
 489
 490                         } else if (expr_type == TypeManager.byte_type){
 491                                 //
 492                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 493                                 //
 494                                 if ((target_type == TypeManager.short_type) ||
 495                                     (target_type == TypeManager.ushort_type) ||
 496                                     (target_type == TypeManager.int32_type) ||
 497                                     (target_type == TypeManager.uint32_type) ||
 498                                     (target_type == TypeManager.uint64_type) ||
 499                                     (target_type == TypeManager.int64_type) ||
 500                                     (target_type == TypeManager.float_type) ||
 501                                     (target_type == TypeManager.double_type) ||
 502                                     (target_type == TypeManager.decimal_type))
 503                                         return true;
 504
 505                         } else if (expr_type == TypeManager.short_type){
 506                                 //
 507                                 // From short to int, long, float, double
 508                                 //
 509                                 if ((target_type == TypeManager.int32_type) ||
 510                                     (target_type == TypeManager.int64_type) ||
 511                                     (target_type == TypeManager.double_type) ||
 512                                     (target_type == TypeManager.float_type) ||
 513                                     (target_type == TypeManager.decimal_type))
 514                                         return true;
 515
 516                         } else if (expr_type == TypeManager.ushort_type){
 517                                 //
 518                                 // From ushort to int, uint, long, ulong, float, double
 519                                 //
 520                                 if ((target_type == TypeManager.uint32_type) ||
 521                                     (target_type == TypeManager.uint64_type) ||
 522                                     (target_type == TypeManager.int32_type) ||
 523                                     (target_type == TypeManager.int64_type) ||
 524                                     (target_type == TypeManager.double_type) ||
 525                                     (target_type == TypeManager.float_type) ||
 526                                     (target_type == TypeManager.decimal_type))
 527                                         return true;
 528
 529                         } else if (expr_type == TypeManager.int32_type){
 530                                 //
 531                                 // From int to long, float, double
 532                                 //
 533                                 if ((target_type == TypeManager.int64_type) ||
 534                                     (target_type == TypeManager.double_type) ||
 535                                     (target_type == TypeManager.float_type) ||
 536                                     (target_type == TypeManager.decimal_type))
 537                                         return true;
 538
 539                         } else if (expr_type == TypeManager.uint32_type){
 540                                 //
 541                                 // From uint to long, ulong, float, double
 542                                 //
 543                                 if ((target_type == TypeManager.int64_type) ||
 544                                     (target_type == TypeManager.uint64_type) ||
 545                                     (target_type == TypeManager.double_type) ||
 546                                     (target_type == TypeManager.float_type) ||
 547                                     (target_type == TypeManager.decimal_type))
 548                                         return true;
 549
 550                         } else if ((expr_type == TypeManager.uint64_type) ||
 551                                    (expr_type == TypeManager.int64_type)) {
 552                                 //
 553                                 // From long/ulong to float, double
 554                                 //
 555                                 if ((target_type == TypeManager.double_type) ||
 556                                     (target_type == TypeManager.float_type) ||
 557                                     (target_type == TypeManager.decimal_type))
 558                                         return true;
 559
 560                         } else if (expr_type == TypeManager.char_type){
 561                                 //
 562                                 // From char to ushort, int, uint, long, ulong, float, double
 563                                 //
 564                                 if ((target_type == TypeManager.ushort_type) ||
 565                                     (target_type == TypeManager.int32_type) ||
 566                                     (target_type == TypeManager.uint32_type) ||
 567                                     (target_type == TypeManager.uint64_type) ||
 568                                     (target_type == TypeManager.int64_type) ||
 569                                     (target_type == TypeManager.float_type) ||
 570                                     (target_type == TypeManager.double_type) ||
 571                                     (target_type == TypeManager.decimal_type))
 572                                         return true;
 573
 574                         } else if (expr_type == TypeManager.float_type){
 575                                 //
 576                                 // float to double
 577                                 //
 578                                 if (target_type == TypeManager.double_type)
 579                                         return true;
 580                         }
 581
 582                         if (expr.eclass == ExprClass.MethodGroup){
 583                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 584                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 585                                         if (mg != null){
 586                                                 //
 587                                                 // This should not happen frequently, so we can create an object
 588                                                 // to test compatibility
 589                                                 //
 590                                                 Expression c = ImplicitDelegateCreation.Create (ec, mg, target_type, Location.Null);
 591                                                 return c != null;
 592                                         }
 593                                 }
 594                         }
 595
 596                         if (ImplicitReferenceConversionExists (expr, target_type))
 597                                 return true;
 598
 599                         //
 600                         // Implicit Constant Expression Conversions
 601                         //
 602                         if (expr is IntConstant){
 603                                 int value = ((IntConstant) expr).Value;
 604
 605                                 if (target_type == TypeManager.sbyte_type){
 606                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 607                                                 return true;
 608                                 } else if (target_type == TypeManager.byte_type){
 609                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 610                                                 return true;
 611                                 } else if (target_type == TypeManager.short_type){
 612                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 613                                                 return true;
 614                                 } else if (target_type == TypeManager.ushort_type){
 615                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 616                                                 return true;
 617                                 } else if (target_type == TypeManager.uint32_type){
 618                                         if (value >= 0)
 619                                                 return true;
 620                                 } else if (target_type == TypeManager.uint64_type){
 621                                          //
 622                                          // we can optimize this case: a positive int32
 623                                          // always fits on a uint64.  But we need an opcode
 624                                          // to do it.
 625                                          //
 626                                         if (value >= 0)
 627                                                 return true;
 628                                 }
 629
 630                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 631                                         return true;
 632                         }
 633
 634                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 635                                 //
 636                                 // Try the implicit constant expression conversion
 637                                 // from long to ulong, instead of a nice routine,
 638                                 // we just inline it
 639                                 //
 640                                 long v = ((LongConstant) expr).Value;
 641                                 if (v > 0)
 642                                         return true;
 643                         }
 644
 645                         if ((target_type == TypeManager.enum_type ||
 646                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 647                              expr is IntLiteral){
 648                                 IntLiteral i = (IntLiteral) expr;
 649
 650                                 if (i.Value == 0)
 651                                         return true;
 652                         }
 653
 654                         //
 655                         // If `expr_type' implements `target_type' (which is an iface)
 656                         // see TryImplicitIntConversion
 657                         //
 658                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 659                                 return true;
 660
 661                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 662                                 return true;
 663
 664                         if (expr_type == TypeManager.anonymous_method_type){
 665                                 if (!TypeManager.IsDelegateType (target_type))
 666                                         return false;
 667
 668                                 AnonymousMethod am = (AnonymousMethod) expr;
 669
 670                                 Expression conv = am.Compatible (ec, target_type, true);
 671                                 if (conv != null)
 672                                         return true;
 673                         }
 674
 675                         return false;
 676                 }
 677
 678                 //
 679                 // Used internally by FindMostEncompassedType, this is used
 680                 // to avoid creating lots of objects in the tight loop inside
 681                 // FindMostEncompassedType
 682                 //
 683                 static EmptyExpression priv_fmet_param;
 684
 685                 /// <summary>
 686                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 687                 ///  amongst the methods in the MethodGroupExpr
 688                 /// </summary>
 689                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 690                 {
 691                         Type best = null;
 692
 693                         if (priv_fmet_param == null)
 694                                 priv_fmet_param = new EmptyExpression ();
 695
 696                         foreach (Type t in types){
 697                                 priv_fmet_param.SetType (t);
 698
 699                                 if (best == null) {
 700                                         best = t;
 701                                         continue;
 702                                 }
 703
 704                                 if (ImplicitStandardConversionExists (ec, priv_fmet_param, best))
 705                                         best = t;
 706                         }
 707
 708                         return best;
 709                 }
 710
 711                 //
 712                 // Used internally by FindMostEncompassingType, this is used
 713                 // to avoid creating lots of objects in the tight loop inside
 714                 // FindMostEncompassingType
 715                 //
 716                 static EmptyExpression priv_fmee_ret;
 717
 718                 /// <summary>
 719                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 720                 ///  amongst the types in the given set
 721                 /// </summary>
 722                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 723                 {
 724                         Type best = null;
 725
 726                         if (priv_fmee_ret == null)
 727                                 priv_fmee_ret = new EmptyExpression ();
 728
 729                         foreach (Type t in types){
 730                                 priv_fmee_ret.SetType (best);
 731
 732                                 if (best == null) {
 733                                         best = t;
 734                                         continue;
 735                                 }
 736
 737                                 if (ImplicitStandardConversionExists (ec, priv_fmee_ret, t))
 738                                         best = t;
 739                         }
 740
 741                         return best;
 742                 }
 743
 744                 //
 745                 // Used to avoid creating too many objects
 746                 //
 747                 static EmptyExpression priv_fms_expr;
 748
 749                 /// <summary>
 750                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 751                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 752                 ///   for explicit and implicit conversion operators.
 753                 /// </summary>
 754                 static public Type FindMostSpecificSource (EmitContext ec, MethodGroupExpr me,
 755                                                            Expression source, bool apply_explicit_conv_rules,
 756                                                            Location loc)
 757                 {
 758                         ArrayList src_types_set = new ArrayList ();
 759
 760                         if (priv_fms_expr == null)
 761                                 priv_fms_expr = new EmptyExpression ();
 762
 763                         //
 764                         // If any operator converts from S then Sx = S
 765                         //
 766                         Type source_type = source.Type;
 767                         foreach (MethodBase mb in me.Methods){
 768                                 ParameterData pd = TypeManager.GetParameterData (mb);
 769                                 Type param_type = pd.ParameterType (0);
 770
 771                                 if (param_type == source_type)
 772                                         return param_type;
 773
 774                                 if (apply_explicit_conv_rules) {
 775                                         //
 776                                         // From the spec :
 777                                         // Find the set of applicable user-defined conversion operators, U.  This set
 778                                         // consists of the
 779                                         // user-defined implicit or explicit conversion operators declared by
 780                                         // the classes or structs in D that convert from a type encompassing
 781                                         // or encompassed by S to a type encompassing or encompassed by T
 782                                         //
 783                                         priv_fms_expr.SetType (param_type);
 784                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, source_type))
 785                                                 src_types_set.Add (param_type);
 786                                         else {
 787                                                 if (ImplicitStandardConversionExists (ec, source, param_type))
 788                                                         src_types_set.Add (param_type);
 789                                         }
 790                                 } else {
 791                                         //
 792                                         // Only if S is encompassed by param_type
 793                                         //
 794                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 795                                                 src_types_set.Add (param_type);
 796                                 }
 797                         }
 798
 799                         //
 800                         // Explicit Conv rules
 801                         //
 802                         if (apply_explicit_conv_rules) {
 803                                 ArrayList candidate_set = new ArrayList ();
 804
 805                                 foreach (Type param_type in src_types_set){
 806                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 807                                                 candidate_set.Add (param_type);
 808                                 }
 809
 810                                 if (candidate_set.Count != 0)
 811                                         return FindMostEncompassedType (ec, candidate_set);
 812                         }
 813
 814                         //
 815                         // Final case
 816                         //
 817                         if (apply_explicit_conv_rules)
 818                                 return FindMostEncompassingType (ec, src_types_set);
 819                         else
 820                                 return FindMostEncompassedType (ec, src_types_set);
 821                 }
 822
 823                 //
 824                 // Useful in avoiding proliferation of objects
 825                 //
 826                 static EmptyExpression priv_fmt_expr;
 827
 828                 /// <summary>
 829                 ///  Finds the most specific target Tx according to section 13.4.4
 830                 /// </summary>
 831                 static public Type FindMostSpecificTarget (EmitContext ec, MethodGroupExpr me,
 832                                                            Type target, bool apply_explicit_conv_rules,
 833                                                            Location loc)
 834                 {
 835                         ArrayList tgt_types_set = new ArrayList ();
 836
 837                         if (priv_fmt_expr == null)
 838                                 priv_fmt_expr = new EmptyExpression ();
 839
 840                         //
 841                         // If any operator converts to T then Tx = T
 842                         //
 843                         foreach (MethodInfo mi in me.Methods){
 844                                 Type ret_type = mi.ReturnType;
 845
 846                                 if (ret_type == target)
 847                                         return ret_type;
 848
 849                                 if (apply_explicit_conv_rules) {
 850                                         //
 851                                         // From the spec :
 852                                         // Find the set of applicable user-defined conversion operators, U.
 853                                         //
 854                                         // This set consists of the
 855                                         // user-defined implicit or explicit conversion operators declared by
 856                                         // the classes or structs in D that convert from a type encompassing
 857                                         // or encompassed by S to a type encompassing or encompassed by T
 858                                         //
 859                                         priv_fms_expr.SetType (ret_type);
 860                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
 861                                                 tgt_types_set.Add (ret_type);
 862                                         else {
 863                                                 priv_fms_expr.SetType (target);
 864                                                 if (ImplicitStandardConversionExists (ec, priv_fms_expr, ret_type))
 865                                                         tgt_types_set.Add (ret_type);
 866                                         }
 867                                 } else {
 868                                         //
 869                                         // Only if T is encompassed by param_type
 870                                         //
 871                                         priv_fms_expr.SetType (ret_type);
 872                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
 873                                                 tgt_types_set.Add (ret_type);
 874                                 }
 875                         }
 876
 877                         //
 878                         // Explicit conv rules
 879                         //
 880                         if (apply_explicit_conv_rules) {
 881                                 ArrayList candidate_set = new ArrayList ();
 882
 883                                 foreach (Type ret_type in tgt_types_set){
 884                                         priv_fmt_expr.SetType (ret_type);
 885
 886                                         if (ImplicitStandardConversionExists (ec, priv_fmt_expr, target))
 887                                                 candidate_set.Add (ret_type);
 888                                 }
 889
 890                                 if (candidate_set.Count != 0)
 891                                         return FindMostEncompassingType (ec, candidate_set);
 892                         }
 893
 894                         //
 895                         // Okay, final case !
 896                         //
 897                         if (apply_explicit_conv_rules)
 898                                 return FindMostEncompassedType (ec, tgt_types_set);
 899                         else
 900                                 return FindMostEncompassingType (ec, tgt_types_set);
 901                 }
 902
 903                 /// <summary>
 904                 ///  User-defined Implicit conversions
 905                 /// </summary>
 906                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 907                                                                  Type target, Location loc)
 908                 {
 909                         return UserDefinedConversion (ec, source, target, loc, false);
 910                 }
 911
 912                 /// <summary>
 913                 ///  User-defined Explicit conversions
 914                 /// </summary>
 915                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 916                                                                  Type target, Location loc)
 917                 {
 918                         return UserDefinedConversion (ec, source, target, loc, true);
 919                 }
 920
 921                 static DoubleHash explicit_conv = new DoubleHash (100);
 922                 static DoubleHash implicit_conv = new DoubleHash (100);
 923                 /// <summary>
 924                 ///   Computes the MethodGroup for the user-defined conversion
 925                 ///   operators from source_type to target_type.  `look_for_explicit'
 926                 ///   controls whether we should also include the list of explicit
 927                 ///   operators
 928                 /// </summary>
 929                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
 930                                                                Type source_type, Type target_type,
 931                                                                Location loc, bool look_for_explicit)
 932                 {
 933                         Expression mg1 = null, mg2 = null;
 934                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 935                         string op_name;
 936
 937                         op_name = "op_Implicit";
 938
 939                         MethodGroupExpr union3;
 940                         object r;
 941                         if ((look_for_explicit ? explicit_conv : implicit_conv).Lookup (source_type, target_type, out r))
 942                                 return (MethodGroupExpr) r;
 943
 944                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
 945                         if (source_type.BaseType != null)
 946                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 947
 948                         if (mg1 == null)
 949                                 union3 = (MethodGroupExpr) mg2;
 950                         else if (mg2 == null)
 951                                 union3 = (MethodGroupExpr) mg1;
 952                         else
 953                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
 954
 955                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
 956                         if (mg1 != null){
 957                                 if (union3 != null)
 958                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 959                                 else
 960                                         union3 = (MethodGroupExpr) mg1;
 961                         }
 962
 963                         if (target_type.BaseType != null)
 964                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 965
 966                         if (mg1 != null){
 967                                 if (union3 != null)
 968                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 969                                 else
 970                                         union3 = (MethodGroupExpr) mg1;
 971                         }
 972
 973                         MethodGroupExpr union4 = null;
 974
 975                         if (look_for_explicit) {
 976                                 op_name = "op_Explicit";
 977
 978                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
 979                                 if (source_type.BaseType != null)
 980                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 981
 982                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
 983                                 if (target_type.BaseType != null)
 984                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 985
 986                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
 987                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
 988
 989                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
 990                         }
 991
 992                         MethodGroupExpr ret = Invocation.MakeUnionSet (union3, union4, loc);
 993                         (look_for_explicit ? explicit_conv : implicit_conv).Insert (source_type, target_type, ret);
 994                         return ret;
 995                 }
 996
 997                 /// <summary>
 998                 ///   User-defined conversions
 999                 /// </summary>
1000                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
1001                                                                 Type target, Location loc,
1002                                                                 bool look_for_explicit)
1003                 {
1004                         MethodGroupExpr union;
1005                         Type source_type = source.Type;
1006                         MethodBase method = null;
1007
1008                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
1009                         if (union == null)
1010                                 return null;
1011
1012                         Type most_specific_source, most_specific_target;
1013
1014                         most_specific_source = FindMostSpecificSource (ec, union, source, look_for_explicit, loc);
1015                         if (most_specific_source == null)
1016                                 return null;
1017
1018                         most_specific_target = FindMostSpecificTarget (ec, union, target, look_for_explicit, loc);
1019                         if (most_specific_target == null)
1020                                 return null;
1021
1022                         int count = 0;
1023
1024
1025                         foreach (MethodBase mb in union.Methods){
1026                                 ParameterData pd = TypeManager.GetParameterData (mb);
1027                                 MethodInfo mi = (MethodInfo) mb;
1028
1029                                 if (pd.ParameterType (0) == most_specific_source &&
1030                                     mi.ReturnType == most_specific_target) {
1031                                         method = mb;
1032                                         count++;
1033                                 }
1034                         }
1035
1036                         if (method == null || count > 1)
1037                                 return null;
1038
1039
1040                         //
1041                         // This will do the conversion to the best match that we
1042                         // found.  Now we need to perform an implict standard conversion
1043                         // if the best match was not the type that we were requested
1044                         // by target.
1045                         //
1046                         if (look_for_explicit)
1047                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1048                         else
1049                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1050
1051                         if (source == null)
1052                                 return null;
1053
1054                         Expression e;
1055                         e =  new UserCast ((MethodInfo) method, source, loc);
1056                         if (e.Type != target){
1057                                 if (!look_for_explicit)
1058                                         e = ImplicitConversionStandard (ec, e, target, loc);
1059                                 else
1060                                         e = ExplicitConversionStandard (ec, e, target, loc);
1061                         }
1062
1063                         return e;
1064                 }
1065
1066                 /// <summary>
1067                 ///   Converts implicitly the resolved expression `expr' into the
1068                 ///   `target_type'.  It returns a new expression that can be used
1069                 ///   in a context that expects a `target_type'.
1070                 /// </summary>
1071                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1072                                                              Type target_type, Location loc)
1073                 {
1074                         Expression e;
1075
1076                         if (target_type == null)
1077                                 throw new Exception ("Target type is null");
1078
1079                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1080                         if (e != null)
1081                                 return e;
1082
1083                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1084                         if (e != null)
1085                                 return e;
1086
1087                         return null;
1088                 }
1089
1090
1091                 /// <summary>
1092                 ///   Attempts to apply the `Standard Implicit
1093                 ///   Conversion' rules to the expression `expr' into
1094                 ///   the `target_type'.  It returns a new expression
1095                 ///   that can be used in a context that expects a
1096                 ///   `target_type'.
1097                 ///
1098                 ///   This is different from `ImplicitConversion' in that the
1099                 ///   user defined implicit conversions are excluded.
1100                 /// </summary>
1101                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1102                                                                      Type target_type, Location loc)
1103                 {
1104                         Type expr_type = expr.Type;
1105                         Expression e;
1106
1107                         if (expr.eclass == ExprClass.MethodGroup){
1108                                 if (!TypeManager.IsDelegateType (target_type)){
1109                                         return null;
1110                                 }
1111
1112                                 //
1113                                 // Only allow anonymous method conversions on post ISO_1
1114                                 //
1115                                 if (RootContext.Version != LanguageVersion.ISO_1){
1116                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1117                                         if (mg != null)
1118                                                 return ImplicitDelegateCreation.Create (ec, mg, target_type, loc);
1119                                 }
1120                         }
1121
1122                         if (expr_type == target_type && expr_type != TypeManager.null_type)
1123                                 return expr;
1124
1125                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1126                         if (e != null)
1127                                 return e;
1128
1129                         e = ImplicitReferenceConversion (expr, target_type);
1130                         if (e != null)
1131                                 return e;
1132
1133                         if ((target_type == TypeManager.enum_type ||
1134                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1135                             expr is IntLiteral){
1136                                 IntLiteral i = (IntLiteral) expr;
1137
1138                                 if (i.Value == 0)
1139                                         return new EnumConstant ((Constant) expr, target_type);
1140                         }
1141
1142                         if (ec.InUnsafe) {
1143                                 if (expr_type.IsPointer){
1144                                         if (target_type == TypeManager.void_ptr_type)
1145                                                 return new EmptyCast (expr, target_type);
1146
1147                                         //
1148                                         // yep, comparing pointer types cant be done with
1149                                         // t1 == t2, we have to compare their element types.
1150                                         //
1151                                         if (target_type.IsPointer){
1152                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1153                                                         return expr;
1154                                         }
1155                                 }
1156
1157                                 if (target_type.IsPointer) {
1158                                         if (expr_type == TypeManager.null_type)
1159                                                 return new EmptyCast (NullPointer.Null, target_type);
1160
1161                                         if (expr_type == TypeManager.void_ptr_type)
1162                                                 return new EmptyCast (expr, target_type);
1163                                 }
1164                         }
1165
1166                         if (expr_type == TypeManager.anonymous_method_type){
1167                                 if (!TypeManager.IsDelegateType (target_type)){
1168                                         Report.Error (1660, loc,
1169                                                               "Cannot convert anonymous method to `{0}', since it is not a delegate",
1170                                                               TypeManager.CSharpName (target_type));
1171                                         return null;
1172                                 }
1173
1174                                 AnonymousMethod am = (AnonymousMethod) expr;
1175                                 int errors = Report.Errors;
1176
1177                                 Expression conv = am.Compatible (ec, target_type, false);
1178                                 if (conv != null)
1179                                         return conv;
1180
1181                                 //
1182                                 // We return something instead of null, to avoid
1183                                 // the duplicate error, since am.Compatible would have
1184                                 // reported that already
1185                                 //
1186                                 if (errors != Report.Errors)
1187                                         return new EmptyCast (expr, target_type);
1188                         }
1189
1190                         return null;
1191                 }
1192
1193                 /// <summary>
1194                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1195                 ///   into a different data type using casts (See Implicit Constant
1196                 ///   Expression Conversions)
1197                 /// </summary>
1198                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1199                 {
1200                         int value = ic.Value;
1201
1202                         if (target_type == TypeManager.sbyte_type){
1203                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1204                                         return new SByteConstant ((sbyte) value);
1205                         } else if (target_type == TypeManager.byte_type){
1206                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1207                                         return new ByteConstant ((byte) value);
1208                         } else if (target_type == TypeManager.short_type){
1209                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1210                                         return new ShortConstant ((short) value);
1211                         } else if (target_type == TypeManager.ushort_type){
1212                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1213                                         return new UShortConstant ((ushort) value);
1214                         } else if (target_type == TypeManager.uint32_type){
1215                                 if (value >= 0)
1216                                         return new UIntConstant ((uint) value);
1217                         } else if (target_type == TypeManager.uint64_type){
1218                                 //
1219                                 // we can optimize this case: a positive int32
1220                                 // always fits on a uint64.  But we need an opcode
1221                                 // to do it.
1222                                 //
1223                                 if (value >= 0)
1224                                         return new ULongConstant ((ulong) value);
1225                         } else if (target_type == TypeManager.double_type)
1226                                 return new DoubleConstant ((double) value);
1227                         else if (target_type == TypeManager.float_type)
1228                                 return new FloatConstant ((float) value);
1229
1230                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1231                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1232                                 Constant e = (Constant) ic;
1233
1234                                 //
1235                                 // Possibly, we need to create a different 0 literal before passing
1236                                 // to EnumConstant
1237                                 //
1238                                 if (underlying == TypeManager.int64_type)
1239                                         e = new LongLiteral (0);
1240                                 else if (underlying == TypeManager.uint64_type)
1241                                         e = new ULongLiteral (0);
1242
1243                                 return new EnumConstant (e, target_type);
1244                         }
1245
1246                         //
1247                         // If `target_type' is an interface and the type of `ic' implements the interface
1248                         // e.g. target_type is IComparable, IConvertible, IFormattable
1249                         //
1250                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1251                                 return new BoxedCast (ic);
1252
1253                         return null;
1254                 }
1255
1256                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1257                 {
1258                         if (source.Name == target.Name){
1259                                 Report.ExtraInformation (loc,
1260                                          String.Format (
1261                                                 "The type {0} has two conflicting definitions, one comes from {1} and the other from {2}",
1262                                                 source.Name, source.Assembly.FullName, target.Assembly.FullName));
1263
1264                         }
1265                         Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
1266                                       source == TypeManager.anonymous_method_type ?
1267                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1268                                       TypeManager.CSharpName (target));
1269                 }
1270
1271                 /// <summary>
1272                 ///   Attempts to implicitly convert `source' into `target_type', using
1273                 ///   ImplicitConversion.  If there is no implicit conversion, then
1274                 ///   an error is signaled
1275                 /// </summary>
1276                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1277                                                                      Type target_type, Location loc)
1278                 {
1279                         Expression e;
1280
1281                         e = ImplicitConversion (ec, source, target_type, loc);
1282                         if (e != null)
1283                                 return e;
1284
1285                         if (source is DoubleLiteral) {
1286                                 if (target_type == TypeManager.float_type) {
1287                                         Error_664 (loc, "float", "f");
1288                                         return null;
1289                                 }
1290                                 if (target_type == TypeManager.decimal_type) {
1291                                         Error_664 (loc, "decimal", "m");
1292                                         return null;
1293                                 }
1294                         }
1295
1296                         if (source is Constant){
1297                                 Constant c = (Constant) source;
1298
1299                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1300                                 return null;
1301                         }
1302
1303                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1304
1305                         return null;
1306                 }
1307
1308                 static void Error_664 (Location loc, string type, string suffix) {
1309                         Report.Error (664, loc,
1310                                 "Literal of type double cannot be implicitly converted to type '{0}'. Add suffix '{1}' to create a literal of this type",
1311                                 type, suffix);
1312                 }
1313
1314                 /// <summary>
1315                 ///   Performs the explicit numeric conversions
1316                 /// </summary>
1317                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1318                 {
1319                         Type expr_type = expr.Type;
1320
1321                         //
1322                         // If we have an enumeration, extract the underlying type,
1323                         // use this during the comparison, but wrap around the original
1324                         // target_type
1325                         //
1326                         Type real_target_type = target_type;
1327
1328                         if (TypeManager.IsEnumType (real_target_type))
1329                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1330
1331                         if (ImplicitStandardConversionExists (ec, expr, real_target_type)){
1332                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1333
1334                                 if (real_target_type != target_type)
1335                                         return new EmptyCast (ce, target_type);
1336                                 return ce;
1337                         }
1338
1339                         if (expr_type == TypeManager.sbyte_type){
1340                                 //
1341                                 // From sbyte to byte, ushort, uint, ulong, char
1342                                 //
1343                                 if (real_target_type == TypeManager.byte_type)
1344                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1345                                 if (real_target_type == TypeManager.ushort_type)
1346                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1347                                 if (real_target_type == TypeManager.uint32_type)
1348                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1349                                 if (real_target_type == TypeManager.uint64_type)
1350                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1351                                 if (real_target_type == TypeManager.char_type)
1352                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1353                         } else if (expr_type == TypeManager.byte_type){
1354                                 //
1355                                 // From byte to sbyte and char
1356                                 //
1357                                 if (real_target_type == TypeManager.sbyte_type)
1358                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1359                                 if (real_target_type == TypeManager.char_type)
1360                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1361                         } else if (expr_type == TypeManager.short_type){
1362                                 //
1363                                 // From short to sbyte, byte, ushort, uint, ulong, char
1364                                 //
1365                                 if (real_target_type == TypeManager.sbyte_type)
1366                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1367                                 if (real_target_type == TypeManager.byte_type)
1368                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1369                                 if (real_target_type == TypeManager.ushort_type)
1370                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1371                                 if (real_target_type == TypeManager.uint32_type)
1372                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1373                                 if (real_target_type == TypeManager.uint64_type)
1374                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1375                                 if (real_target_type == TypeManager.char_type)
1376                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1377                         } else if (expr_type == TypeManager.ushort_type){
1378                                 //
1379                                 // From ushort to sbyte, byte, short, char
1380                                 //
1381                                 if (real_target_type == TypeManager.sbyte_type)
1382                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1383                                 if (real_target_type == TypeManager.byte_type)
1384                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1385                                 if (real_target_type == TypeManager.short_type)
1386                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1387                                 if (real_target_type == TypeManager.char_type)
1388                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1389                         } else if (expr_type == TypeManager.int32_type){
1390                                 //
1391                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1392                                 //
1393                                 if (real_target_type == TypeManager.sbyte_type)
1394                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1395                                 if (real_target_type == TypeManager.byte_type)
1396                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1397                                 if (real_target_type == TypeManager.short_type)
1398                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1399                                 if (real_target_type == TypeManager.ushort_type)
1400                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1401                                 if (real_target_type == TypeManager.uint32_type)
1402                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1403                                 if (real_target_type == TypeManager.uint64_type)
1404                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1405                                 if (real_target_type == TypeManager.char_type)
1406                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1407                         } else if (expr_type == TypeManager.uint32_type){
1408                                 //
1409                                 // From uint to sbyte, byte, short, ushort, int, char
1410                                 //
1411                                 if (real_target_type == TypeManager.sbyte_type)
1412                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1413                                 if (real_target_type == TypeManager.byte_type)
1414                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1415                                 if (real_target_type == TypeManager.short_type)
1416                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1417                                 if (real_target_type == TypeManager.ushort_type)
1418                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1419                                 if (real_target_type == TypeManager.int32_type)
1420                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1421                                 if (real_target_type == TypeManager.char_type)
1422                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1423                         } else if (expr_type == TypeManager.int64_type){
1424                                 //
1425                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1426                                 //
1427                                 if (real_target_type == TypeManager.sbyte_type)
1428                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1429                                 if (real_target_type == TypeManager.byte_type)
1430                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1431                                 if (real_target_type == TypeManager.short_type)
1432                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1433                                 if (real_target_type == TypeManager.ushort_type)
1434                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1435                                 if (real_target_type == TypeManager.int32_type)
1436                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1437                                 if (real_target_type == TypeManager.uint32_type)
1438                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1439                                 if (real_target_type == TypeManager.uint64_type)
1440                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1441                                 if (real_target_type == TypeManager.char_type)
1442                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1443                         } else if (expr_type == TypeManager.uint64_type){
1444                                 //
1445                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1446                                 //
1447                                 if (real_target_type == TypeManager.sbyte_type)
1448                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1449                                 if (real_target_type == TypeManager.byte_type)
1450                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1451                                 if (real_target_type == TypeManager.short_type)
1452                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1453                                 if (real_target_type == TypeManager.ushort_type)
1454                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1455                                 if (real_target_type == TypeManager.int32_type)
1456                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1457                                 if (real_target_type == TypeManager.uint32_type)
1458                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1459                                 if (real_target_type == TypeManager.int64_type)
1460                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1461                                 if (real_target_type == TypeManager.char_type)
1462                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1463                         } else if (expr_type == TypeManager.char_type){
1464                                 //
1465                                 // From char to sbyte, byte, short
1466                                 //
1467                                 if (real_target_type == TypeManager.sbyte_type)
1468                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1469                                 if (real_target_type == TypeManager.byte_type)
1470                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1471                                 if (real_target_type == TypeManager.short_type)
1472                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1473                         } else if (expr_type == TypeManager.float_type){
1474                                 //
1475                                 // From float to sbyte, byte, short,
1476                                 // ushort, int, uint, long, ulong, char
1477                                 // or decimal
1478                                 //
1479                                 if (real_target_type == TypeManager.sbyte_type)
1480                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1481                                 if (real_target_type == TypeManager.byte_type)
1482                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1483                                 if (real_target_type == TypeManager.short_type)
1484                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1485                                 if (real_target_type == TypeManager.ushort_type)
1486                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1487                                 if (real_target_type == TypeManager.int32_type)
1488                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1489                                 if (real_target_type == TypeManager.uint32_type)
1490                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1491                                 if (real_target_type == TypeManager.int64_type)
1492                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1493                                 if (real_target_type == TypeManager.uint64_type)
1494                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1495                                 if (real_target_type == TypeManager.char_type)
1496                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1497                         } else if (expr_type == TypeManager.double_type){
1498                                 //
1499                                 // From double to byte, byte, short,
1500                                 // ushort, int, uint, long, ulong,
1501                                 // char, float or decimal
1502                                 //
1503                                 if (real_target_type == TypeManager.sbyte_type)
1504                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1505                                 if (real_target_type == TypeManager.byte_type)
1506                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1507                                 if (real_target_type == TypeManager.short_type)
1508                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1509                                 if (real_target_type == TypeManager.ushort_type)
1510                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1511                                 if (real_target_type == TypeManager.int32_type)
1512                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1513                                 if (real_target_type == TypeManager.uint32_type)
1514                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1515                                 if (real_target_type == TypeManager.int64_type)
1516                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1517                                 if (real_target_type == TypeManager.uint64_type)
1518                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1519                                 if (real_target_type == TypeManager.char_type)
1520                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1521                                 if (real_target_type == TypeManager.float_type)
1522                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1523                         }
1524
1525                         // decimal is taken care of by the op_Explicit methods.
1526
1527                         return null;
1528                 }
1529
1530                 /// <summary>
1531                 ///  Returns whether an explicit reference conversion can be performed
1532                 ///  from source_type to target_type
1533                 /// </summary>
1534                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1535                 {
1536                         bool target_is_value_type = target_type.IsValueType;
1537
1538                         if (source_type == target_type)
1539                                 return true;
1540
1541                         //
1542                         // From object to any reference type
1543                         //
1544                         if (source_type == TypeManager.object_type && !target_is_value_type)
1545                                 return true;
1546
1547                         //
1548                         // From any class S to any class-type T, provided S is a base class of T
1549                         //
1550                         if (target_type.IsSubclassOf (source_type))
1551                                 return true;
1552
1553                         //
1554                         // From any interface type S to any interface T provided S is not derived from T
1555                         //
1556                         if (source_type.IsInterface && target_type.IsInterface){
1557                                 if (!target_type.IsSubclassOf (source_type))
1558                                         return true;
1559                         }
1560
1561                         //
1562                         // From any class type S to any interface T, provided S is not sealed
1563                         // and provided S does not implement T.
1564                         //
1565                         if (target_type.IsInterface && !source_type.IsSealed &&
1566                             !TypeManager.ImplementsInterface (source_type, target_type))
1567                                 return true;
1568
1569                         //
1570                         // From any interface-type S to to any class type T, provided T is not
1571                         // sealed, or provided T implements S.
1572                         //
1573                         if (source_type.IsInterface &&
1574                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1575                                 return true;
1576
1577
1578                         // From an array type S with an element type Se to an array type T with an
1579                         // element type Te provided all the following are true:
1580                         //     * S and T differe only in element type, in other words, S and T
1581                         //       have the same number of dimensions.
1582                         //     * Both Se and Te are reference types
1583                         //     * An explicit referenc conversions exist from Se to Te
1584                         //
1585                         if (source_type.IsArray && target_type.IsArray) {
1586                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1587
1588                                         Type source_element_type = TypeManager.GetElementType (source_type);
1589                                         Type target_element_type = TypeManager.GetElementType (target_type);
1590
1591                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1592                                                 if (ExplicitReferenceConversionExists (source_element_type,
1593                                                                                        target_element_type))
1594                                                         return true;
1595                                 }
1596                         }
1597
1598
1599                         // From System.Array to any array-type
1600                         if (source_type == TypeManager.array_type &&
1601                             target_type.IsArray){
1602                                 return true;
1603                         }
1604
1605                         //
1606                         // From System delegate to any delegate-type
1607                         //
1608                         if (source_type == TypeManager.delegate_type &&
1609                             target_type.IsSubclassOf (TypeManager.delegate_type))
1610                                 return true;
1611
1612                         //
1613                         // From ICloneable to Array or Delegate types
1614                         //
1615                         if (source_type == TypeManager.icloneable_type &&
1616                             (target_type == TypeManager.array_type ||
1617                              target_type == TypeManager.delegate_type))
1618                                 return true;
1619
1620                         return false;
1621                 }
1622
1623                 /// <summary>
1624                 ///   Implements Explicit Reference conversions
1625                 /// </summary>
1626                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1627                 {
1628                         Type source_type = source.Type;
1629                         bool target_is_value_type = target_type.IsValueType;
1630
1631                         //
1632                         // From object to any reference type
1633                         //
1634                         if (source_type == TypeManager.object_type && !target_is_value_type)
1635                                 return new ClassCast (source, target_type);
1636
1637                         //
1638                         // Unboxing conversion.
1639                         //
1640                         if (((source_type == TypeManager.enum_type &&
1641                                 !(source is EmptyCast)) ||
1642                                 source_type == TypeManager.value_type) && target_is_value_type)
1643                                 return new UnboxCast (source, target_type);
1644
1645                         //
1646                         // From any class S to any class-type T, provided S is a base class of T
1647                         //
1648                         if (target_type.IsSubclassOf (source_type))
1649                                 return new ClassCast (source, target_type);
1650
1651                         //
1652                         // From any interface type S to any interface T provided S is not derived from T
1653                         //
1654                         if (source_type.IsInterface && target_type.IsInterface){
1655                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1656                                         return null;
1657                                 else
1658                                         return new ClassCast (source, target_type);
1659                         }
1660
1661                         //
1662                         // From any class type S to any interface T, provides S is not sealed
1663                         // and provided S does not implement T.
1664                         //
1665                         if (target_type.IsInterface && !source_type.IsSealed) {
1666                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1667                                         return null;
1668                                 else
1669                                         return new ClassCast (source, target_type);
1670
1671                         }
1672
1673                         //
1674                         // From any interface-type S to to any class type T, provided T is not
1675                         // sealed, or provided T implements S.
1676                         //
1677                         if (source_type.IsInterface) {
1678                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1679                                         if (target_type.IsClass)
1680                                                 return new ClassCast (source, target_type);
1681                                         else
1682                                                 return new UnboxCast (source, target_type);
1683                                 }
1684
1685                                 return null;
1686                         }
1687
1688                         // From an array type S with an element type Se to an array type T with an
1689                         // element type Te provided all the following are true:
1690                         //     * S and T differe only in element type, in other words, S and T
1691                         //       have the same number of dimensions.
1692                         //     * Both Se and Te are reference types
1693                         //     * An explicit referenc conversions exist from Se to Te
1694                         //
1695                         if (source_type.IsArray && target_type.IsArray) {
1696                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1697
1698                                         Type source_element_type = TypeManager.GetElementType (source_type);
1699                                         Type target_element_type = TypeManager.GetElementType (target_type);
1700
1701                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1702                                                 if (ExplicitReferenceConversionExists (source_element_type,
1703                                                                                        target_element_type))
1704                                                         return new ClassCast (source, target_type);
1705                                 }
1706                         }
1707
1708
1709                         // From System.Array to any array-type
1710                         if (source_type == TypeManager.array_type &&
1711                             target_type.IsArray) {
1712                                 return new ClassCast (source, target_type);
1713                         }
1714
1715                         //
1716                         // From System delegate to any delegate-type
1717                         //
1718                         if (source_type == TypeManager.delegate_type &&
1719                             target_type.IsSubclassOf (TypeManager.delegate_type))
1720                                 return new ClassCast (source, target_type);
1721
1722                         //
1723                         // From ICloneable to Array or Delegate types
1724                         //
1725                         if (source_type == TypeManager.icloneable_type &&
1726                             (target_type == TypeManager.array_type ||
1727                              target_type == TypeManager.delegate_type))
1728                                 return new ClassCast (source, target_type);
1729
1730                         return null;
1731                 }
1732
1733                 /// <summary>
1734                 ///   Performs an explicit conversion of the expression `expr' whose
1735                 ///   type is expr.Type to `target_type'.
1736                 /// </summary>
1737                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1738                                                              Type target_type, Location loc)
1739                 {
1740                         Type expr_type = expr.Type;
1741                         Type original_expr_type = expr_type;
1742
1743                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1744                                 if (target_type == TypeManager.enum_type ||
1745                                     target_type == TypeManager.object_type) {
1746                                         if (expr is EnumConstant)
1747                                                 expr = ((EnumConstant) expr).Child;
1748                                         // We really need all these casts here .... :-(
1749                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1750                                         return new EmptyCast (expr, target_type);
1751                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1752                                            target_type.IsSubclassOf (TypeManager.enum_type))
1753                                         return new UnboxCast (expr, target_type);
1754
1755                                 //
1756                                 // Notice that we have kept the expr_type unmodified, which is only
1757                                 // used later on to
1758                                 if (expr is EnumConstant)
1759                                         expr = ((EnumConstant) expr).Child;
1760                                 else
1761                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1762                                 expr_type = expr.Type;
1763                         }
1764
1765                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1766
1767                         if (ne != null)
1768                                 return ne;
1769
1770                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1771                         if (ne != null)
1772                                 return ne;
1773
1774                         //
1775                         // Unboxing conversion.
1776                         //
1777                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1778                                 return new UnboxCast (expr, target_type);
1779
1780                         //
1781                         // Skip the ExplicitReferenceConversion because we can not convert
1782                         // from Null to a ValueType, and ExplicitReference wont check against
1783                         // null literal explicitly
1784                         //
1785                         if (expr_type != TypeManager.null_type){
1786                                 ne = ExplicitReferenceConversion (expr, target_type);
1787                                 if (ne != null)
1788                                         return ne;
1789                         }
1790
1791                         if (ec.InUnsafe){
1792                                 if (target_type.IsPointer){
1793                                         if (expr_type.IsPointer)
1794                                                 return new EmptyCast (expr, target_type);
1795
1796                                         if (expr_type == TypeManager.sbyte_type ||
1797                                             expr_type == TypeManager.short_type ||
1798                                             expr_type == TypeManager.int32_type ||
1799                                             expr_type == TypeManager.int64_type)
1800                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
1801
1802                                         if (expr_type == TypeManager.ushort_type ||
1803                                             expr_type == TypeManager.uint32_type ||
1804                                             expr_type == TypeManager.uint64_type ||
1805                                             expr_type == TypeManager.byte_type)
1806                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1807                                 }
1808                                 if (expr_type.IsPointer){
1809                                         Expression e = null;
1810
1811                                         if (target_type == TypeManager.sbyte_type)
1812                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1813                                         else if (target_type == TypeManager.byte_type)
1814                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1815                                         else if (target_type == TypeManager.short_type)
1816                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1817                                         else if (target_type == TypeManager.ushort_type)
1818                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1819                                         else if (target_type == TypeManager.int32_type)
1820                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1821                                         else if (target_type == TypeManager.uint32_type)
1822                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1823                                         else if (target_type == TypeManager.uint64_type)
1824                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1825                                         else if (target_type == TypeManager.int64_type){
1826                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1827                                         }
1828
1829                                         if (e != null){
1830                                                 Expression ci, ce;
1831
1832                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1833
1834                                                 if (ci != null)
1835                                                         return ci;
1836
1837                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1838                                                 if (ce != null)
1839                                                         return ce;
1840                                                 //
1841                                                 // We should always be able to go from an uint32
1842                                                 // implicitly or explicitly to the other integral
1843                                                 // types
1844                                                 //
1845                                                 throw new Exception ("Internal compiler error");
1846                                         }
1847                                 }
1848                         }
1849
1850                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1851                         if (ne != null)
1852                                 return ne;
1853
1854                         if (expr is NullLiteral){
1855                                 Report.Error (37, loc, "Cannot convert null to value type `" +
1856                                               TypeManager.CSharpName (target_type) + "'");
1857                                 return null;
1858                         }
1859
1860                         Error_CannotConvertType (loc, original_expr_type, target_type);
1861                         return null;
1862                 }
1863
1864                 /// <summary>
1865                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1866                 /// </summary>
1867                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1868                                                                   Type target_type, Location l)
1869                 {
1870                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1871
1872                         if (ne != null)
1873                                 return ne;
1874
1875                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1876                         if (ne != null)
1877                                 return ne;
1878
1879                         ne = ExplicitReferenceConversion (expr, target_type);
1880                         if (ne != null)
1881                                 return ne;
1882
1883                         Error_CannotConvertType (l, expr.Type, target_type);
1884                         return null;
1885                 }
1886         }
1887 }