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                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  23                 {
  24                         Report.Error (30, loc, "Cannot convert type '" +
  25                                       TypeManager.CSharpName (source) + "' to '" +
  26                                       TypeManager.CSharpName (target) + "'");
  27                 }
  28
  29                 static EmptyExpression MyEmptyExpr;
  30                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  31                 {
  32                         Type expr_type = expr.Type;
  33
  34                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  35                                 // if we are a method group, emit a warning
  36
  37                                 expr.Emit (null);
  38                         }
  39
  40                         //
  41                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  42                         // is an abstract class, and not really a value type, so we apply the same rules.
  43                         //
  44                         if (target_type == TypeManager.object_type) {
  45                                 //
  46                                 // A pointer type cannot be converted to object
  47                                 //
  48                                 if (expr_type.IsPointer)
  49                                         return null;
  50
  51                                 if (expr_type.IsValueType)
  52                                         return new BoxedCast (expr);
  53                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type)
  54                                         return new EmptyCast (expr, target_type);
  55                         } else if (target_type == TypeManager.value_type) {
  56                                 if (expr_type.IsValueType)
  57                                         return new BoxedCast (expr);
  58                                 if (expr is NullLiteral)
  59                                         return new BoxedCast (expr);
  60                         } else if (expr_type.IsSubclassOf (target_type)) {
  61                                 //
  62                                 // Special case: enumeration to System.Enum.
  63                                 // System.Enum is not a value type, it is a class, so we need
  64                                 // a boxing conversion
  65                                 //
  66                                 if (expr_type.IsEnum)
  67                                         return new BoxedCast (expr);
  68
  69                                 return new EmptyCast (expr, target_type);
  70                         } else {
  71
  72                                 // This code is kind of mirrored inside ImplicitStandardConversionExists
  73                                 // with the small distinction that we only probe there
  74                                 //
  75                                 // Always ensure that the code here and there is in sync
  76
  77                                 // from the null type to any reference-type.
  78                                 if (expr is NullLiteral){
  79                                         if (target_type.IsPointer)
  80                                                 return NullPointer.Null;
  81
  82                                         if (!target_type.IsValueType)
  83                                                 return new NullCast (expr, target_type);
  84                                 }
  85
  86                                 // from any class-type S to any interface-type T.
  87                                 if (target_type.IsInterface) {
  88                                         if (TypeManager.ImplementsInterface (expr_type, target_type)){
  89                                                 if (expr_type.IsClass)
  90                                                         return new EmptyCast (expr, target_type);
  91                                                 else if (expr_type.IsValueType)
  92                                                         return new BoxedCast (expr, target_type);
  93                                         }
  94                                 }
  95
  96                                 // from any interface type S to interface-type T.
  97                                 if (expr_type.IsInterface && target_type.IsInterface) {
  98                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
  99                                                 return new EmptyCast (expr, target_type);
 100                                         else
 101                                                 return null;
 102                                 }
 103
 104                                 // from an array-type S to an array-type of type T
 105                                 if (expr_type.IsArray && target_type.IsArray) {
 106                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 107
 108                                                 Type expr_element_type = TypeManager.GetElementType (expr_type);
 109
 110                                                 if (MyEmptyExpr == null)
 111                                                         MyEmptyExpr = new EmptyExpression ();
 112
 113                                                 MyEmptyExpr.SetType (expr_element_type);
 114                                                 Type target_element_type = TypeManager.GetElementType (target_type);
 115
 116                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 117                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 118                                                                                       target_element_type))
 119                                                                 return new EmptyCast (expr, target_type);
 120                                         }
 121                                 }
 122
 123
 124                                 // from an array-type to System.Array
 125                                 if (expr_type.IsArray && target_type == TypeManager.array_type)
 126                                         return new EmptyCast (expr, target_type);
 127
 128                                 // from any delegate type to System.Delegate
 129                                 if ((expr_type == TypeManager.delegate_type ||
 130                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 131                                     target_type == TypeManager.delegate_type)
 132                                         return new EmptyCast (expr, target_type);
 133
 134                                 // from any array-type or delegate type into System.ICloneable.
 135                                 if (expr_type.IsArray ||
 136                                     expr_type == TypeManager.delegate_type ||
 137                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 138                                         if (target_type == TypeManager.icloneable_type)
 139                                                 return new EmptyCast (expr, target_type);
 140
 141                                 return null;
 142
 143                         }
 144
 145                         return null;
 146                 }
 147
 148                 //
 149                 // Tests whether an implicit reference conversion exists between expr_type
 150                 // and target_type
 151                 //
 152                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 153                 {
 154                         Type expr_type = expr.Type;
 155
 156                         //
 157                         // This is the boxed case.
 158                         //
 159                         if (target_type == TypeManager.object_type) {
 160                                 if (expr_type.IsClass || expr_type.IsValueType ||
 161                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 162                                         return true;
 163                         } else if (expr_type.IsSubclassOf (target_type)) {
 164                                 return true;
 165                         } else {
 166                                 // Please remember that all code below actually comes
 167                                 // from ImplicitReferenceConversion so make sure code remains in sync
 168
 169                                 // from any class-type S to any interface-type T.
 170                                 if (target_type.IsInterface) {
 171                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 172                                                 return true;
 173                                 }
 174
 175                                 // from any interface type S to interface-type T.
 176                                 if (expr_type.IsInterface && target_type.IsInterface)
 177                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 178                                                 return true;
 179
 180                                 // from an array-type S to an array-type of type T
 181                                 if (expr_type.IsArray && target_type.IsArray) {
 182                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 183
 184                                                 Type expr_element_type = expr_type.GetElementType ();
 185
 186                                                 if (MyEmptyExpr == null)
 187                                                         MyEmptyExpr = new EmptyExpression ();
 188
 189                                                 MyEmptyExpr.SetType (expr_element_type);
 190                                                 Type target_element_type = TypeManager.GetElementType (target_type);
 191
 192                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 193                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 194                                                                                       target_element_type))
 195                                                                 return true;
 196                                         }
 197                                 }
 198
 199                                 // from an array-type to System.Array
 200                                 if (expr_type.IsArray && (target_type == TypeManager.array_type))
 201                                         return true;
 202
 203                                 // from any delegate type to System.Delegate
 204                                 if ((expr_type == TypeManager.delegate_type ||
 205                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 206                                     target_type == TypeManager.delegate_type)
 207                                         if (target_type.IsAssignableFrom (expr_type))
 208                                                 return true;
 209
 210                                 // from any array-type or delegate type into System.ICloneable.
 211                                 if (expr_type.IsArray ||
 212                                     expr_type == TypeManager.delegate_type ||
 213                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 214                                         if (target_type == TypeManager.icloneable_type)
 215                                                 return true;
 216
 217                                 // from the null type to any reference-type.
 218                                 if (expr is NullLiteral && !target_type.IsValueType &&
 219                                     !TypeManager.IsEnumType (target_type))
 220                                         return true;
 221
 222                         }
 223                         return false;
 224                 }
 225
 226                 /// <summary>
 227                 ///   Implicit Numeric Conversions.
 228                 ///
 229                 ///   expr is the expression to convert, returns a new expression of type
 230                 ///   target_type or null if an implicit conversion is not possible.
 231                 /// </summary>
 232                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 233                                                                     Type target_type, Location loc)
 234                 {
 235                         Type expr_type = expr.Type;
 236
 237                         //
 238                         // Attempt to do the implicit constant expression conversions
 239
 240                         if (expr is Constant){
 241
 242                                 if (expr is IntConstant){
 243                                         Expression e;
 244
 245                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 246
 247                                         if (e != null)
 248                                                 return e;
 249                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 250                                         //
 251                                         // Try the implicit constant expression conversion
 252                                         // from long to ulong, instead of a nice routine,
 253                                         // we just inline it
 254                                         //
 255                                         long v = ((LongConstant) expr).Value;
 256                                         if (v > 0)
 257                                                 return new ULongConstant ((ulong) v);
 258                                 }
 259                         }
 260
 261                         Type real_target_type = target_type;
 262
 263                         if (expr_type == TypeManager.sbyte_type){
 264                                 //
 265                                 // From sbyte to short, int, long, float, double.
 266                                 //
 267                                 if (real_target_type == TypeManager.int32_type)
 268                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 269                                 if (real_target_type == TypeManager.int64_type)
 270                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 271                                 if (real_target_type == TypeManager.double_type)
 272                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 273                                 if (real_target_type == TypeManager.float_type)
 274                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 275                                 if (real_target_type == TypeManager.short_type)
 276                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 277                         } else if (expr_type == TypeManager.byte_type){
 278                                 //
 279                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 280                                 //
 281                                 if ((real_target_type == TypeManager.short_type) ||
 282                                     (real_target_type == TypeManager.ushort_type) ||
 283                                     (real_target_type == TypeManager.int32_type) ||
 284                                     (real_target_type == TypeManager.uint32_type))
 285                                         return new EmptyCast (expr, target_type);
 286
 287                                 if (real_target_type == TypeManager.uint64_type)
 288                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 289                                 if (real_target_type == TypeManager.int64_type)
 290                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 291                                 if (real_target_type == TypeManager.float_type)
 292                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 293                                 if (real_target_type == TypeManager.double_type)
 294                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 295                         } else if (expr_type == TypeManager.short_type){
 296                                 //
 297                                 // From short to int, long, float, double
 298                                 //
 299                                 if (real_target_type == TypeManager.int32_type)
 300                                         return new EmptyCast (expr, target_type);
 301                                 if (real_target_type == TypeManager.int64_type)
 302                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 303                                 if (real_target_type == TypeManager.double_type)
 304                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 305                                 if (real_target_type == TypeManager.float_type)
 306                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 307                         } else if (expr_type == TypeManager.ushort_type){
 308                                 //
 309                                 // From ushort to int, uint, long, ulong, float, double
 310                                 //
 311                                 if (real_target_type == TypeManager.uint32_type)
 312                                         return new EmptyCast (expr, target_type);
 313
 314                                 if (real_target_type == TypeManager.uint64_type)
 315                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 316                                 if (real_target_type == TypeManager.int32_type)
 317                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 318                                 if (real_target_type == TypeManager.int64_type)
 319                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 320                                 if (real_target_type == TypeManager.double_type)
 321                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 322                                 if (real_target_type == TypeManager.float_type)
 323                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 324                         } else if (expr_type == TypeManager.int32_type){
 325                                 //
 326                                 // From int to long, float, double
 327                                 //
 328                                 if (real_target_type == TypeManager.int64_type)
 329                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 330                                 if (real_target_type == TypeManager.double_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 332                                 if (real_target_type == TypeManager.float_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 334                         } else if (expr_type == TypeManager.uint32_type){
 335                                 //
 336                                 // From uint to long, ulong, float, double
 337                                 //
 338                                 if (real_target_type == TypeManager.int64_type)
 339                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 340                                 if (real_target_type == TypeManager.uint64_type)
 341                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 342                                 if (real_target_type == TypeManager.double_type)
 343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 344                                                                OpCodes.Conv_R8);
 345                                 if (real_target_type == TypeManager.float_type)
 346                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 347                                                                OpCodes.Conv_R4);
 348                         } else if (expr_type == TypeManager.int64_type){
 349                                 //
 350                                 // From long/ulong to float, double
 351                                 //
 352                                 if (real_target_type == TypeManager.double_type)
 353                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 354                                 if (real_target_type == TypeManager.float_type)
 355                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 356                         } else if (expr_type == TypeManager.uint64_type){
 357                                 //
 358                                 // From ulong to float, double
 359                                 //
 360                                 if (real_target_type == TypeManager.double_type)
 361                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 362                                                                OpCodes.Conv_R8);
 363                                 if (real_target_type == TypeManager.float_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 365                                                                OpCodes.Conv_R4);
 366                         } else if (expr_type == TypeManager.char_type){
 367                                 //
 368                                 // From char to ushort, int, uint, long, ulong, float, double
 369                                 //
 370                                 if ((real_target_type == TypeManager.ushort_type) ||
 371                                     (real_target_type == TypeManager.int32_type) ||
 372                                     (real_target_type == TypeManager.uint32_type))
 373                                         return new EmptyCast (expr, target_type);
 374                                 if (real_target_type == TypeManager.uint64_type)
 375                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 376                                 if (real_target_type == TypeManager.int64_type)
 377                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 378                                 if (real_target_type == TypeManager.float_type)
 379                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 380                                 if (real_target_type == TypeManager.double_type)
 381                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 382                         } else if (expr_type == TypeManager.float_type){
 383                                 //
 384                                 // float to double
 385                                 //
 386                                 if (real_target_type == TypeManager.double_type)
 387                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 388                         }
 389
 390                         return null;
 391                 }
 392
 393
 394                 /// <summary>
 395                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 396                 ///  implicit user defined conversions - needed for overload resolution
 397                 /// </summary>
 398                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 399                 {
 400                         if (ImplicitStandardConversionExists (expr, target_type))
 401                                 return true;
 402
 403                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 404
 405                         if (dummy != null)
 406                                 return true;
 407
 408                         return false;
 409                 }
 410
 411                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 412                 {
 413                         Expression dummy = ImplicitUserConversion (
 414                                 ec, new EmptyExpression (source), target, Location.Null);
 415                         return dummy != null;
 416                 }
 417
 418                 /// <summary>
 419                 ///  Determines if a standard implicit conversion exists from
 420                 ///  expr_type to target_type
 421                 /// </summary>
 422                 public static bool ImplicitStandardConversionExists (Expression expr, Type target_type)
 423                 {
 424                         Type expr_type = expr.Type;
 425
 426                         if (expr_type == TypeManager.void_type)
 427                                 return false;
 428
 429                         if (expr_type == target_type)
 430                                 return true;
 431
 432                         // First numeric conversions
 433
 434                         if (expr_type == TypeManager.sbyte_type){
 435                                 //
 436                                 // From sbyte to short, int, long, float, double.
 437                                 //
 438                                 if ((target_type == TypeManager.int32_type) ||
 439                                     (target_type == TypeManager.int64_type) ||
 440                                     (target_type == TypeManager.double_type) ||
 441                                     (target_type == TypeManager.float_type)  ||
 442                                     (target_type == TypeManager.short_type) ||
 443                                     (target_type == TypeManager.decimal_type))
 444                                         return true;
 445
 446                         } else if (expr_type == TypeManager.byte_type){
 447                                 //
 448                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 449                                 //
 450                                 if ((target_type == TypeManager.short_type) ||
 451                                     (target_type == TypeManager.ushort_type) ||
 452                                     (target_type == TypeManager.int32_type) ||
 453                                     (target_type == TypeManager.uint32_type) ||
 454                                     (target_type == TypeManager.uint64_type) ||
 455                                     (target_type == TypeManager.int64_type) ||
 456                                     (target_type == TypeManager.float_type) ||
 457                                     (target_type == TypeManager.double_type) ||
 458                                     (target_type == TypeManager.decimal_type))
 459                                         return true;
 460
 461                         } else if (expr_type == TypeManager.short_type){
 462                                 //
 463                                 // From short to int, long, float, double
 464                                 //
 465                                 if ((target_type == TypeManager.int32_type) ||
 466                                     (target_type == TypeManager.int64_type) ||
 467                                     (target_type == TypeManager.double_type) ||
 468                                     (target_type == TypeManager.float_type) ||
 469                                     (target_type == TypeManager.decimal_type))
 470                                         return true;
 471
 472                         } else if (expr_type == TypeManager.ushort_type){
 473                                 //
 474                                 // From ushort to int, uint, long, ulong, float, double
 475                                 //
 476                                 if ((target_type == TypeManager.uint32_type) ||
 477                                     (target_type == TypeManager.uint64_type) ||
 478                                     (target_type == TypeManager.int32_type) ||
 479                                     (target_type == TypeManager.int64_type) ||
 480                                     (target_type == TypeManager.double_type) ||
 481                                     (target_type == TypeManager.float_type) ||
 482                                     (target_type == TypeManager.decimal_type))
 483                                         return true;
 484
 485                         } else if (expr_type == TypeManager.int32_type){
 486                                 //
 487                                 // From int to long, float, double
 488                                 //
 489                                 if ((target_type == TypeManager.int64_type) ||
 490                                     (target_type == TypeManager.double_type) ||
 491                                     (target_type == TypeManager.float_type) ||
 492                                     (target_type == TypeManager.decimal_type))
 493                                         return true;
 494
 495                         } else if (expr_type == TypeManager.uint32_type){
 496                                 //
 497                                 // From uint to long, ulong, float, double
 498                                 //
 499                                 if ((target_type == TypeManager.int64_type) ||
 500                                     (target_type == TypeManager.uint64_type) ||
 501                                     (target_type == TypeManager.double_type) ||
 502                                     (target_type == TypeManager.float_type) ||
 503                                     (target_type == TypeManager.decimal_type))
 504                                         return true;
 505
 506                         } else if ((expr_type == TypeManager.uint64_type) ||
 507                                    (expr_type == TypeManager.int64_type)) {
 508                                 //
 509                                 // From long/ulong to float, double
 510                                 //
 511                                 if ((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.char_type){
 517                                 //
 518                                 // From char to ushort, int, uint, long, ulong, float, double
 519                                 //
 520                                 if ((target_type == TypeManager.ushort_type) ||
 521                                     (target_type == TypeManager.int32_type) ||
 522                                     (target_type == TypeManager.uint32_type) ||
 523                                     (target_type == TypeManager.uint64_type) ||
 524                                     (target_type == TypeManager.int64_type) ||
 525                                     (target_type == TypeManager.float_type) ||
 526                                     (target_type == TypeManager.double_type) ||
 527                                     (target_type == TypeManager.decimal_type))
 528                                         return true;
 529
 530                         } else if (expr_type == TypeManager.float_type){
 531                                 //
 532                                 // float to double
 533                                 //
 534                                 if (target_type == TypeManager.double_type)
 535                                         return true;
 536                         }
 537
 538                         if (ImplicitReferenceConversionExists (expr, target_type))
 539                                 return true;
 540
 541                         if (expr is IntConstant){
 542                                 int value = ((IntConstant) expr).Value;
 543
 544                                 if (target_type == TypeManager.sbyte_type){
 545                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 546                                                 return true;
 547                                 } else if (target_type == TypeManager.byte_type){
 548                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 549                                                 return true;
 550                                 } else if (target_type == TypeManager.short_type){
 551                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 552                                                 return true;
 553                                 } else if (target_type == TypeManager.ushort_type){
 554                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 555                                                 return true;
 556                                 } else if (target_type == TypeManager.uint32_type){
 557                                         if (value >= 0)
 558                                                 return true;
 559                                 } else if (target_type == TypeManager.uint64_type){
 560                                          //
 561                                          // we can optimize this case: a positive int32
 562                                          // always fits on a uint64.  But we need an opcode
 563                                          // to do it.
 564                                          //
 565                                         if (value >= 0)
 566                                                 return true;
 567                                 }
 568
 569                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 570                                         return true;
 571                         }
 572
 573                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 574                                 //
 575                                 // Try the implicit constant expression conversion
 576                                 // from long to ulong, instead of a nice routine,
 577                                 // we just inline it
 578                                 //
 579                                 long v = ((LongConstant) expr).Value;
 580                                 if (v > 0)
 581                                         return true;
 582                         }
 583
 584                         if ((target_type == TypeManager.enum_type ||
 585                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 586                              expr is IntLiteral){
 587                                 IntLiteral i = (IntLiteral) expr;
 588
 589                                 if (i.Value == 0)
 590                                         return true;
 591                         }
 592
 593                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 594                                 return true;
 595
 596                         return false;
 597                 }
 598
 599                 //
 600                 // Used internally by FindMostEncompassedType, this is used
 601                 // to avoid creating lots of objects in the tight loop inside
 602                 // FindMostEncompassedType
 603                 //
 604                 static EmptyExpression priv_fmet_param;
 605
 606                 /// <summary>
 607                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 608                 ///  amongst the methods in the MethodGroupExpr
 609                 /// </summary>
 610                 static Type FindMostEncompassedType (ArrayList types)
 611                 {
 612                         Type best = null;
 613
 614                         if (priv_fmet_param == null)
 615                                 priv_fmet_param = new EmptyExpression ();
 616
 617                         foreach (Type t in types){
 618                                 priv_fmet_param.SetType (t);
 619
 620                                 if (best == null) {
 621                                         best = t;
 622                                         continue;
 623                                 }
 624
 625                                 if (ImplicitStandardConversionExists (priv_fmet_param, best))
 626                                         best = t;
 627                         }
 628
 629                         return best;
 630                 }
 631
 632                 //
 633                 // Used internally by FindMostEncompassingType, this is used
 634                 // to avoid creating lots of objects in the tight loop inside
 635                 // FindMostEncompassingType
 636                 //
 637                 static EmptyExpression priv_fmee_ret;
 638
 639                 /// <summary>
 640                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 641                 ///  amongst the types in the given set
 642                 /// </summary>
 643                 static Type FindMostEncompassingType (ArrayList types)
 644                 {
 645                         Type best = null;
 646
 647                         if (priv_fmee_ret == null)
 648                                 priv_fmee_ret = new EmptyExpression ();
 649
 650                         foreach (Type t in types){
 651                                 priv_fmee_ret.SetType (best);
 652
 653                                 if (best == null) {
 654                                         best = t;
 655                                         continue;
 656                                 }
 657
 658                                 if (ImplicitStandardConversionExists (priv_fmee_ret, t))
 659                                         best = t;
 660                         }
 661
 662                         return best;
 663                 }
 664
 665                 //
 666                 // Used to avoid creating too many objects
 667                 //
 668                 static EmptyExpression priv_fms_expr;
 669
 670                 /// <summary>
 671                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 672                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 673                 ///   for explicit and implicit conversion operators.
 674                 /// </summary>
 675                 static public Type FindMostSpecificSource (MethodGroupExpr me, Expression source,
 676                                                            bool apply_explicit_conv_rules,
 677                                                            Location loc)
 678                 {
 679                         ArrayList src_types_set = new ArrayList ();
 680
 681                         if (priv_fms_expr == null)
 682                                 priv_fms_expr = new EmptyExpression ();
 683
 684                         //
 685                         // If any operator converts from S then Sx = S
 686                         //
 687                         Type source_type = source.Type;
 688                         foreach (MethodBase mb in me.Methods){
 689                                 ParameterData pd = Invocation.GetParameterData (mb);
 690                                 Type param_type = pd.ParameterType (0);
 691
 692                                 if (param_type == source_type)
 693                                         return param_type;
 694
 695                                 if (apply_explicit_conv_rules) {
 696                                         //
 697                                         // From the spec :
 698                                         // Find the set of applicable user-defined conversion operators, U.  This set
 699                                         // consists of the
 700                                         // user-defined implicit or explicit conversion operators declared by
 701                                         // the classes or structs in D that convert from a type encompassing
 702                                         // or encompassed by S to a type encompassing or encompassed by T
 703                                         //
 704                                         priv_fms_expr.SetType (param_type);
 705                                         if (ImplicitStandardConversionExists (priv_fms_expr, source_type))
 706                                                 src_types_set.Add (param_type);
 707                                         else {
 708                                                 if (ImplicitStandardConversionExists (source, param_type))
 709                                                         src_types_set.Add (param_type);
 710                                         }
 711                                 } else {
 712                                         //
 713                                         // Only if S is encompassed by param_type
 714                                         //
 715                                         if (ImplicitStandardConversionExists (source, param_type))
 716                                                 src_types_set.Add (param_type);
 717                                 }
 718                         }
 719
 720                         //
 721                         // Explicit Conv rules
 722                         //
 723                         if (apply_explicit_conv_rules) {
 724                                 ArrayList candidate_set = new ArrayList ();
 725
 726                                 foreach (Type param_type in src_types_set){
 727                                         if (ImplicitStandardConversionExists (source, param_type))
 728                                                 candidate_set.Add (param_type);
 729                                 }
 730
 731                                 if (candidate_set.Count != 0)
 732                                         return FindMostEncompassedType (candidate_set);
 733                         }
 734
 735                         //
 736                         // Final case
 737                         //
 738                         if (apply_explicit_conv_rules)
 739                                 return FindMostEncompassingType (src_types_set);
 740                         else
 741                                 return FindMostEncompassedType (src_types_set);
 742                 }
 743
 744                 //
 745                 // Useful in avoiding proliferation of objects
 746                 //
 747                 static EmptyExpression priv_fmt_expr;
 748
 749                 /// <summary>
 750                 ///  Finds the most specific target Tx according to section 13.4.4
 751                 /// </summary>
 752                 static public Type FindMostSpecificTarget (MethodGroupExpr me, Type target,
 753                                                            bool apply_explicit_conv_rules,
 754                                                            Location loc)
 755                 {
 756                         ArrayList tgt_types_set = new ArrayList ();
 757
 758                         if (priv_fmt_expr == null)
 759                                 priv_fmt_expr = new EmptyExpression ();
 760
 761                         //
 762                         // If any operator converts to T then Tx = T
 763                         //
 764                         foreach (MethodInfo mi in me.Methods){
 765                                 Type ret_type = mi.ReturnType;
 766
 767                                 if (ret_type == target)
 768                                         return ret_type;
 769
 770                                 if (apply_explicit_conv_rules) {
 771                                         //
 772                                         // From the spec :
 773                                         // Find the set of applicable user-defined conversion operators, U.
 774                                         //
 775                                         // This set consists of the
 776                                         // user-defined implicit or explicit conversion operators declared by
 777                                         // the classes or structs in D that convert from a type encompassing
 778                                         // or encompassed by S to a type encompassing or encompassed by T
 779                                         //
 780                                         priv_fms_expr.SetType (ret_type);
 781                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 782                                                 tgt_types_set.Add (ret_type);
 783                                         else {
 784                                                 priv_fms_expr.SetType (target);
 785                                                 if (ImplicitStandardConversionExists (priv_fms_expr, ret_type))
 786                                                         tgt_types_set.Add (ret_type);
 787                                         }
 788                                 } else {
 789                                         //
 790                                         // Only if T is encompassed by param_type
 791                                         //
 792                                         priv_fms_expr.SetType (ret_type);
 793                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 794                                                 tgt_types_set.Add (ret_type);
 795                                 }
 796                         }
 797
 798                         //
 799                         // Explicit conv rules
 800                         //
 801                         if (apply_explicit_conv_rules) {
 802                                 ArrayList candidate_set = new ArrayList ();
 803
 804                                 foreach (Type ret_type in tgt_types_set){
 805                                         priv_fmt_expr.SetType (ret_type);
 806
 807                                         if (ImplicitStandardConversionExists (priv_fmt_expr, target))
 808                                                 candidate_set.Add (ret_type);
 809                                 }
 810
 811                                 if (candidate_set.Count != 0)
 812                                         return FindMostEncompassingType (candidate_set);
 813                         }
 814
 815                         //
 816                         // Okay, final case !
 817                         //
 818                         if (apply_explicit_conv_rules)
 819                                 return FindMostEncompassedType (tgt_types_set);
 820                         else
 821                                 return FindMostEncompassingType (tgt_types_set);
 822                 }
 823
 824                 /// <summary>
 825                 ///  User-defined Implicit conversions
 826                 /// </summary>
 827                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 828                                                                  Type target, Location loc)
 829                 {
 830                         return UserDefinedConversion (ec, source, target, loc, false);
 831                 }
 832
 833                 /// <summary>
 834                 ///  User-defined Explicit conversions
 835                 /// </summary>
 836                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 837                                                                  Type target, Location loc)
 838                 {
 839                         return UserDefinedConversion (ec, source, target, loc, true);
 840                 }
 841
 842                 /// <summary>
 843                 ///   Computes the MethodGroup for the user-defined conversion
 844                 ///   operators from source_type to target_type.  `look_for_explicit'
 845                 ///   controls whether we should also include the list of explicit
 846                 ///   operators
 847                 /// </summary>
 848                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
 849                                                                Type source_type, Type target_type,
 850                                                                Location loc, bool look_for_explicit)
 851                 {
 852                         Expression mg1 = null, mg2 = null;
 853                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 854                         string op_name;
 855
 856                         op_name = "op_Implicit";
 857
 858                         MethodGroupExpr union3;
 859
 860                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
 861                         if (source_type.BaseType != null)
 862                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 863
 864                         if (mg1 == null)
 865                                 union3 = (MethodGroupExpr) mg2;
 866                         else if (mg2 == null)
 867                                 union3 = (MethodGroupExpr) mg1;
 868                         else
 869                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
 870
 871                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
 872                         if (mg1 != null){
 873                                 if (union3 != null)
 874                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 875                                 else
 876                                         union3 = (MethodGroupExpr) mg1;
 877                         }
 878
 879                         if (target_type.BaseType != null)
 880                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 881
 882                         if (mg1 != null){
 883                                 if (union3 != null)
 884                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 885                                 else
 886                                         union3 = (MethodGroupExpr) mg1;
 887                         }
 888
 889                         MethodGroupExpr union4 = null;
 890
 891                         if (look_for_explicit) {
 892                                 op_name = "op_Explicit";
 893
 894                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
 895                                 if (source_type.BaseType != null)
 896                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 897
 898                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
 899                                 if (target_type.BaseType != null)
 900                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 901
 902                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
 903                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
 904
 905                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
 906                         }
 907
 908                         return Invocation.MakeUnionSet (union3, union4, loc);
 909                 }
 910
 911                 /// <summary>
 912                 ///   User-defined conversions
 913                 /// </summary>
 914                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 915                                                                 Type target, Location loc,
 916                                                                 bool look_for_explicit)
 917                 {
 918                         MethodGroupExpr union;
 919                         Type source_type = source.Type;
 920                         MethodBase method = null;
 921
 922                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
 923                         if (union == null)
 924                                 return null;
 925
 926                         Type most_specific_source, most_specific_target;
 927
 928                         most_specific_source = FindMostSpecificSource (union, source, look_for_explicit, loc);
 929                         if (most_specific_source == null)
 930                                 return null;
 931
 932                         most_specific_target = FindMostSpecificTarget (union, target, look_for_explicit, loc);
 933                         if (most_specific_target == null)
 934                                 return null;
 935
 936                         int count = 0;
 937
 938
 939                         foreach (MethodBase mb in union.Methods){
 940                                 ParameterData pd = Invocation.GetParameterData (mb);
 941                                 MethodInfo mi = (MethodInfo) mb;
 942
 943                                 if (pd.ParameterType (0) == most_specific_source &&
 944                                     mi.ReturnType == most_specific_target) {
 945                                         method = mb;
 946                                         count++;
 947                                 }
 948                         }
 949
 950                         if (method == null || count > 1)
 951                                 return null;
 952
 953
 954                         //
 955                         // This will do the conversion to the best match that we
 956                         // found.  Now we need to perform an implict standard conversion
 957                         // if the best match was not the type that we were requested
 958                         // by target.
 959                         //
 960                         if (look_for_explicit)
 961                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
 962                         else
 963                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
 964
 965                         if (source == null)
 966                                 return null;
 967
 968                         Expression e;
 969                         e =  new UserCast ((MethodInfo) method, source, loc);
 970                         if (e.Type != target){
 971                                 if (!look_for_explicit)
 972                                         e = ImplicitConversionStandard (ec, e, target, loc);
 973                                 else
 974                                         e = ExplicitConversionStandard (ec, e, target, loc);
 975                         }
 976
 977                         return e;
 978                 }
 979
 980                 /// <summary>
 981                 ///   Converts implicitly the resolved expression `expr' into the
 982                 ///   `target_type'.  It returns a new expression that can be used
 983                 ///   in a context that expects a `target_type'.
 984                 /// </summary>
 985                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
 986                                                           Type target_type, Location loc)
 987                 {
 988                         Type expr_type = expr.Type;
 989                         Expression e;
 990
 991                         if (target_type == null)
 992                                 throw new Exception ("Target type is null");
 993
 994                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
 995                         if (e != null)
 996                                 return e;
 997
 998                         e = ImplicitUserConversion (ec, expr, target_type, loc);
 999                         if (e != null)
1000                                 return e;
1001
1002                         return null;
1003                 }
1004
1005
1006                 /// <summary>
1007                 ///   Attempts to apply the `Standard Implicit
1008                 ///   Conversion' rules to the expression `expr' into
1009                 ///   the `target_type'.  It returns a new expression
1010                 ///   that can be used in a context that expects a
1011                 ///   `target_type'.
1012                 ///
1013                 ///   This is different from `ImplicitConversion' in that the
1014                 ///   user defined implicit conversions are excluded.
1015                 /// </summary>
1016                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1017                                                                      Type target_type, Location loc)
1018                 {
1019                         Type expr_type = expr.Type;
1020                         Expression e;
1021
1022                         if (expr_type == target_type && !(expr is NullLiteral))
1023                                 return expr;
1024
1025                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1026                         if (e != null)
1027                                 return e;
1028
1029                         e = ImplicitReferenceConversion (expr, target_type);
1030                         if (e != null)
1031                                 return e;
1032
1033                         if ((target_type == TypeManager.enum_type ||
1034                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1035                             expr is IntLiteral){
1036                                 IntLiteral i = (IntLiteral) expr;
1037
1038                                 if (i.Value == 0)
1039                                         return new EnumConstant ((Constant) expr, target_type);
1040                         }
1041
1042                         if (ec.InUnsafe) {
1043                                 if (expr_type.IsPointer){
1044                                         if (target_type == TypeManager.void_ptr_type)
1045                                                 return new EmptyCast (expr, target_type);
1046
1047                                         //
1048                                         // yep, comparing pointer types cant be done with
1049                                         // t1 == t2, we have to compare their element types.
1050                                         //
1051                                         if (target_type.IsPointer){
1052                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1053                                                         return expr;
1054                                         }
1055                                 }
1056
1057                                 if (target_type.IsPointer) {
1058                                         if (expr is NullLiteral)
1059                                                 return new EmptyCast (expr, target_type);
1060
1061                                         if (expr_type == TypeManager.void_ptr_type)
1062                                                 return new EmptyCast (expr, target_type);
1063                                 }
1064                         }
1065
1066                         return null;
1067                 }
1068
1069                 /// <summary>
1070                 ///   Attemps to perform an implict constant conversion of the IntConstant
1071                 ///   into a different data type using casts (See Implicit Constant
1072                 ///   Expression Conversions)
1073                 /// </summary>
1074                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1075                 {
1076                         int value = ic.Value;
1077
1078                         if (target_type == TypeManager.sbyte_type){
1079                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1080                                         return new SByteConstant ((sbyte) value);
1081                         } else if (target_type == TypeManager.byte_type){
1082                                 if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
1083                                         return new ByteConstant ((byte) value);
1084                         } else if (target_type == TypeManager.short_type){
1085                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1086                                         return new ShortConstant ((short) value);
1087                         } else if (target_type == TypeManager.ushort_type){
1088                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1089                                         return new UShortConstant ((ushort) value);
1090                         } else if (target_type == TypeManager.uint32_type){
1091                                 if (value >= 0)
1092                                         return new UIntConstant ((uint) value);
1093                         } else if (target_type == TypeManager.uint64_type){
1094                                 //
1095                                 // we can optimize this case: a positive int32
1096                                 // always fits on a uint64.  But we need an opcode
1097                                 // to do it.
1098                                 //
1099                                 if (value >= 0)
1100                                         return new ULongConstant ((ulong) value);
1101                         } else if (target_type == TypeManager.double_type)
1102                                 return new DoubleConstant ((double) value);
1103                         else if (target_type == TypeManager.float_type)
1104                                 return new FloatConstant ((float) value);
1105
1106                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1107                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1108                                 Constant e = (Constant) ic;
1109
1110                                 //
1111                                 // Possibly, we need to create a different 0 literal before passing
1112                                 // to EnumConstant
1113                                 //n
1114                                 if (underlying == TypeManager.int64_type)
1115                                         e = new LongLiteral (0);
1116                                 else if (underlying == TypeManager.uint64_type)
1117                                         e = new ULongLiteral (0);
1118
1119                                 return new EnumConstant (e, target_type);
1120                         }
1121                         return null;
1122                 }
1123
1124                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1125                 {
1126                         string msg = "Cannot convert implicitly from `"+
1127                                 TypeManager.CSharpName (source) + "' to `" +
1128                                 TypeManager.CSharpName (target) + "'";
1129
1130                         Report.Error (29, loc, msg);
1131                 }
1132
1133                 /// <summary>
1134                 ///   Attemptes to implicityly convert `target' into `type', using
1135                 ///   ImplicitConversion.  If there is no implicit conversion, then
1136                 ///   an error is signaled
1137                 /// </summary>
1138                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1139                                                                      Type target_type, Location loc)
1140                 {
1141                         Expression e;
1142
1143                         e = ImplicitConversion (ec, source, target_type, loc);
1144                         if (e != null)
1145                                 return e;
1146
1147                         if (source is DoubleLiteral && target_type == TypeManager.float_type){
1148                                 Report.Error (664, loc,
1149                                               "Double literal cannot be implicitly converted to " +
1150                                               "float type, use F suffix to create a float literal");
1151                         }
1152
1153                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1154
1155                         return null;
1156                 }
1157
1158                 /// <summary>
1159                 ///   Performs the explicit numeric conversions
1160                 /// </summary>
1161                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1162                 {
1163                         Type expr_type = expr.Type;
1164
1165                         //
1166                         // If we have an enumeration, extract the underlying type,
1167                         // use this during the comparison, but wrap around the original
1168                         // target_type
1169                         //
1170                         Type real_target_type = target_type;
1171
1172                         if (TypeManager.IsEnumType (real_target_type))
1173                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1174
1175                         if (ImplicitStandardConversionExists (expr, real_target_type)){
1176                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1177
1178                                 if (real_target_type != target_type)
1179                                         return new EmptyCast (ce, target_type);
1180                                 return ce;
1181                         }
1182
1183                         if (expr_type == TypeManager.sbyte_type){
1184                                 //
1185                                 // From sbyte to byte, ushort, uint, ulong, char
1186                                 //
1187                                 if (real_target_type == TypeManager.byte_type)
1188                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1189                                 if (real_target_type == TypeManager.ushort_type)
1190                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1191                                 if (real_target_type == TypeManager.uint32_type)
1192                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1193                                 if (real_target_type == TypeManager.uint64_type)
1194                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1195                                 if (real_target_type == TypeManager.char_type)
1196                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1197                         } else if (expr_type == TypeManager.byte_type){
1198                                 //
1199                                 // From byte to sbyte and char
1200                                 //
1201                                 if (real_target_type == TypeManager.sbyte_type)
1202                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1203                                 if (real_target_type == TypeManager.char_type)
1204                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1205                         } else if (expr_type == TypeManager.short_type){
1206                                 //
1207                                 // From short to sbyte, byte, ushort, uint, ulong, char
1208                                 //
1209                                 if (real_target_type == TypeManager.sbyte_type)
1210                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1211                                 if (real_target_type == TypeManager.byte_type)
1212                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1213                                 if (real_target_type == TypeManager.ushort_type)
1214                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1215                                 if (real_target_type == TypeManager.uint32_type)
1216                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1217                                 if (real_target_type == TypeManager.uint64_type)
1218                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1219                                 if (real_target_type == TypeManager.char_type)
1220                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1221                         } else if (expr_type == TypeManager.ushort_type){
1222                                 //
1223                                 // From ushort to sbyte, byte, short, char
1224                                 //
1225                                 if (real_target_type == TypeManager.sbyte_type)
1226                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1227                                 if (real_target_type == TypeManager.byte_type)
1228                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1229                                 if (real_target_type == TypeManager.short_type)
1230                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1231                                 if (real_target_type == TypeManager.char_type)
1232                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1233                         } else if (expr_type == TypeManager.int32_type){
1234                                 //
1235                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1236                                 //
1237                                 if (real_target_type == TypeManager.sbyte_type)
1238                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1239                                 if (real_target_type == TypeManager.byte_type)
1240                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1241                                 if (real_target_type == TypeManager.short_type)
1242                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1243                                 if (real_target_type == TypeManager.ushort_type)
1244                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1245                                 if (real_target_type == TypeManager.uint32_type)
1246                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1247                                 if (real_target_type == TypeManager.uint64_type)
1248                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1249                                 if (real_target_type == TypeManager.char_type)
1250                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1251                         } else if (expr_type == TypeManager.uint32_type){
1252                                 //
1253                                 // From uint to sbyte, byte, short, ushort, int, char
1254                                 //
1255                                 if (real_target_type == TypeManager.sbyte_type)
1256                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1257                                 if (real_target_type == TypeManager.byte_type)
1258                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1259                                 if (real_target_type == TypeManager.short_type)
1260                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1261                                 if (real_target_type == TypeManager.ushort_type)
1262                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1263                                 if (real_target_type == TypeManager.int32_type)
1264                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1265                                 if (real_target_type == TypeManager.char_type)
1266                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1267                         } else if (expr_type == TypeManager.int64_type){
1268                                 //
1269                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1270                                 //
1271                                 if (real_target_type == TypeManager.sbyte_type)
1272                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1273                                 if (real_target_type == TypeManager.byte_type)
1274                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1275                                 if (real_target_type == TypeManager.short_type)
1276                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1277                                 if (real_target_type == TypeManager.ushort_type)
1278                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1279                                 if (real_target_type == TypeManager.int32_type)
1280                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1281                                 if (real_target_type == TypeManager.uint32_type)
1282                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1283                                 if (real_target_type == TypeManager.uint64_type)
1284                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1285                                 if (real_target_type == TypeManager.char_type)
1286                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1287                         } else if (expr_type == TypeManager.uint64_type){
1288                                 //
1289                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1290                                 //
1291                                 if (real_target_type == TypeManager.sbyte_type)
1292                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1293                                 if (real_target_type == TypeManager.byte_type)
1294                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1295                                 if (real_target_type == TypeManager.short_type)
1296                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1297                                 if (real_target_type == TypeManager.ushort_type)
1298                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1299                                 if (real_target_type == TypeManager.int32_type)
1300                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1301                                 if (real_target_type == TypeManager.uint32_type)
1302                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1303                                 if (real_target_type == TypeManager.int64_type)
1304                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1305                                 if (real_target_type == TypeManager.char_type)
1306                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1307                         } else if (expr_type == TypeManager.char_type){
1308                                 //
1309                                 // From char to sbyte, byte, short
1310                                 //
1311                                 if (real_target_type == TypeManager.sbyte_type)
1312                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1313                                 if (real_target_type == TypeManager.byte_type)
1314                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1315                                 if (real_target_type == TypeManager.short_type)
1316                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1317                         } else if (expr_type == TypeManager.float_type){
1318                                 //
1319                                 // From float to sbyte, byte, short,
1320                                 // ushort, int, uint, long, ulong, char
1321                                 // or decimal
1322                                 //
1323                                 if (real_target_type == TypeManager.sbyte_type)
1324                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1325                                 if (real_target_type == TypeManager.byte_type)
1326                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1327                                 if (real_target_type == TypeManager.short_type)
1328                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1329                                 if (real_target_type == TypeManager.ushort_type)
1330                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1331                                 if (real_target_type == TypeManager.int32_type)
1332                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1333                                 if (real_target_type == TypeManager.uint32_type)
1334                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1335                                 if (real_target_type == TypeManager.int64_type)
1336                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1337                                 if (real_target_type == TypeManager.uint64_type)
1338                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1339                                 if (real_target_type == TypeManager.char_type)
1340                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1341                         } else if (expr_type == TypeManager.double_type){
1342                                 //
1343                                 // From double to byte, byte, short,
1344                                 // ushort, int, uint, long, ulong,
1345                                 // char, float or decimal
1346                                 //
1347                                 if (real_target_type == TypeManager.sbyte_type)
1348                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1349                                 if (real_target_type == TypeManager.byte_type)
1350                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1351                                 if (real_target_type == TypeManager.short_type)
1352                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1353                                 if (real_target_type == TypeManager.ushort_type)
1354                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1355                                 if (real_target_type == TypeManager.int32_type)
1356                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1357                                 if (real_target_type == TypeManager.uint32_type)
1358                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1359                                 if (real_target_type == TypeManager.int64_type)
1360                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1361                                 if (real_target_type == TypeManager.uint64_type)
1362                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1363                                 if (real_target_type == TypeManager.char_type)
1364                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1365                                 if (real_target_type == TypeManager.float_type)
1366                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1367                         }
1368
1369                         // decimal is taken care of by the op_Explicit methods.
1370
1371                         return null;
1372                 }
1373
1374                 /// <summary>
1375                 ///  Returns whether an explicit reference conversion can be performed
1376                 ///  from source_type to target_type
1377                 /// </summary>
1378                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1379                 {
1380                         bool target_is_value_type = target_type.IsValueType;
1381
1382                         if (source_type == target_type)
1383                                 return true;
1384
1385                         //
1386                         // From object to any reference type
1387                         //
1388                         if (source_type == TypeManager.object_type && !target_is_value_type)
1389                                 return true;
1390
1391                         //
1392                         // From any class S to any class-type T, provided S is a base class of T
1393                         //
1394                         if (target_type.IsSubclassOf (source_type))
1395                                 return true;
1396
1397                         //
1398                         // From any interface type S to any interface T provided S is not derived from T
1399                         //
1400                         if (source_type.IsInterface && target_type.IsInterface){
1401                                 if (!target_type.IsSubclassOf (source_type))
1402                                         return true;
1403                         }
1404
1405                         //
1406                         // From any class type S to any interface T, provided S is not sealed
1407                         // and provided S does not implement T.
1408                         //
1409                         if (target_type.IsInterface && !source_type.IsSealed &&
1410                             !TypeManager.ImplementsInterface (source_type, target_type))
1411                                 return true;
1412
1413                         //
1414                         // From any interface-type S to to any class type T, provided T is not
1415                         // sealed, or provided T implements S.
1416                         //
1417                         if (source_type.IsInterface &&
1418                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1419                                 return true;
1420
1421
1422                         // From an array type S with an element type Se to an array type T with an
1423                         // element type Te provided all the following are true:
1424                         //     * S and T differe only in element type, in other words, S and T
1425                         //       have the same number of dimensions.
1426                         //     * Both Se and Te are reference types
1427                         //     * An explicit referenc conversions exist from Se to Te
1428                         //
1429                         if (source_type.IsArray && target_type.IsArray) {
1430                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1431
1432                                         Type source_element_type = TypeManager.GetElementType (source_type);
1433                                         Type target_element_type = TypeManager.GetElementType (target_type);
1434
1435                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1436                                                 if (ExplicitReferenceConversionExists (source_element_type,
1437                                                                                        target_element_type))
1438                                                         return true;
1439                                 }
1440                         }
1441
1442
1443                         // From System.Array to any array-type
1444                         if (source_type == TypeManager.array_type &&
1445                             target_type.IsArray){
1446                                 return true;
1447                         }
1448
1449                         //
1450                         // From System delegate to any delegate-type
1451                         //
1452                         if (source_type == TypeManager.delegate_type &&
1453                             target_type.IsSubclassOf (TypeManager.delegate_type))
1454                                 return true;
1455
1456                         //
1457                         // From ICloneable to Array or Delegate types
1458                         //
1459                         if (source_type == TypeManager.icloneable_type &&
1460                             (target_type == TypeManager.array_type ||
1461                              target_type == TypeManager.delegate_type))
1462                                 return true;
1463
1464                         return false;
1465                 }
1466
1467                 /// <summary>
1468                 ///   Implements Explicit Reference conversions
1469                 /// </summary>
1470                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1471                 {
1472                         Type source_type = source.Type;
1473                         bool target_is_value_type = target_type.IsValueType;
1474
1475                         //
1476                         // From object to any reference type
1477                         //
1478                         if (source_type == TypeManager.object_type && !target_is_value_type)
1479                                 return new ClassCast (source, target_type);
1480
1481
1482                         //
1483                         // From any class S to any class-type T, provided S is a base class of T
1484                         //
1485                         if (target_type.IsSubclassOf (source_type))
1486                                 return new ClassCast (source, target_type);
1487
1488                         //
1489                         // From any interface type S to any interface T provided S is not derived from T
1490                         //
1491                         if (source_type.IsInterface && target_type.IsInterface){
1492                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1493                                         return null;
1494                                 else
1495                                         return new ClassCast (source, target_type);
1496                         }
1497
1498                         //
1499                         // From any class type S to any interface T, provides S is not sealed
1500                         // and provided S does not implement T.
1501                         //
1502                         if (target_type.IsInterface && !source_type.IsSealed) {
1503                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1504                                         return null;
1505                                 else
1506                                         return new ClassCast (source, target_type);
1507
1508                         }
1509
1510                         //
1511                         // From any interface-type S to to any class type T, provided T is not
1512                         // sealed, or provided T implements S.
1513                         //
1514                         if (source_type.IsInterface) {
1515                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1516                                         if (target_type.IsClass)
1517                                                 return new ClassCast (source, target_type);
1518                                         else
1519                                                 return new UnboxCast (source, target_type);
1520                                 }
1521
1522                                 return null;
1523                         }
1524
1525                         // From an array type S with an element type Se to an array type T with an
1526                         // element type Te provided all the following are true:
1527                         //     * S and T differe only in element type, in other words, S and T
1528                         //       have the same number of dimensions.
1529                         //     * Both Se and Te are reference types
1530                         //     * An explicit referenc conversions exist from Se to Te
1531                         //
1532                         if (source_type.IsArray && target_type.IsArray) {
1533                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1534
1535                                         Type source_element_type = TypeManager.GetElementType (source_type);
1536                                         Type target_element_type = TypeManager.GetElementType (target_type);
1537
1538                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1539                                                 if (ExplicitReferenceConversionExists (source_element_type,
1540                                                                                        target_element_type))
1541                                                         return new ClassCast (source, target_type);
1542                                 }
1543                         }
1544
1545
1546                         // From System.Array to any array-type
1547                         if (source_type == TypeManager.array_type &&
1548                             target_type.IsArray) {
1549                                 return new ClassCast (source, target_type);
1550                         }
1551
1552                         //
1553                         // From System delegate to any delegate-type
1554                         //
1555                         if (source_type == TypeManager.delegate_type &&
1556                             target_type.IsSubclassOf (TypeManager.delegate_type))
1557                                 return new ClassCast (source, target_type);
1558
1559                         //
1560                         // From ICloneable to Array or Delegate types
1561                         //
1562                         if (source_type == TypeManager.icloneable_type &&
1563                             (target_type == TypeManager.array_type ||
1564                              target_type == TypeManager.delegate_type))
1565                                 return new ClassCast (source, target_type);
1566
1567                         return null;
1568                 }
1569
1570                 /// <summary>
1571                 ///   Performs an explicit conversion of the expression `expr' whose
1572                 ///   type is expr.Type to `target_type'.
1573                 /// </summary>
1574                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1575                                                           Type target_type, Location loc)
1576                 {
1577                         Type expr_type = expr.Type;
1578                         Type original_expr_type = expr_type;
1579
1580                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1581                                 if (target_type == TypeManager.enum_type ||
1582                                     target_type == TypeManager.object_type) {
1583                                         if (expr is EnumConstant)
1584                                                 expr = ((EnumConstant) expr).Child;
1585                                         // We really need all these casts here .... :-(
1586                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1587                                         return new EmptyCast (expr, target_type);
1588                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1589                                            target_type.IsSubclassOf (TypeManager.enum_type))
1590                                         return new UnboxCast (expr, target_type);
1591
1592                                 //
1593                                 // Notice that we have kept the expr_type unmodified, which is only
1594                                 // used later on to
1595                                 if (expr is EnumConstant)
1596                                         expr = ((EnumConstant) expr).Child;
1597                                 else
1598                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1599                                 expr_type = expr.Type;
1600                         }
1601
1602                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1603
1604                         if (ne != null)
1605                                 return ne;
1606
1607                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1608                         if (ne != null)
1609                                 return ne;
1610
1611                         //
1612                         // Unboxing conversion.
1613                         //
1614                         if (expr_type == TypeManager.object_type && target_type.IsValueType){
1615                                 if (expr is NullLiteral){
1616                                         Report.Error (37, loc, "Cannot convert null to value type `" +
1617                                                       TypeManager.CSharpName (target_type) + "'");
1618                                         return null;
1619                                 }
1620                                 return new UnboxCast (expr, target_type);
1621                         }
1622
1623
1624                         ne = ExplicitReferenceConversion (expr, target_type);
1625                         if (ne != null)
1626                                 return ne;
1627
1628                         if (ec.InUnsafe){
1629                                 if (target_type.IsPointer){
1630                                         if (expr_type.IsPointer)
1631                                                 return new EmptyCast (expr, target_type);
1632
1633                                         if (expr_type == TypeManager.sbyte_type ||
1634                                             expr_type == TypeManager.byte_type ||
1635                                             expr_type == TypeManager.short_type ||
1636                                             expr_type == TypeManager.ushort_type ||
1637                                             expr_type == TypeManager.int32_type ||
1638                                             expr_type == TypeManager.uint32_type ||
1639                                             expr_type == TypeManager.uint64_type ||
1640                                             expr_type == TypeManager.int64_type)
1641                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1642                                 }
1643                                 if (expr_type.IsPointer){
1644                                         Expression e = null;
1645
1646                                         if (target_type == TypeManager.sbyte_type)
1647                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1648                                         else if (target_type == TypeManager.byte_type)
1649                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1650                                         else if (target_type == TypeManager.short_type)
1651                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1652                                         else if (target_type == TypeManager.ushort_type)
1653                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1654                                         else if (target_type == TypeManager.int32_type)
1655                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1656                                         else if (target_type == TypeManager.uint32_type)
1657                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1658                                         else if (target_type == TypeManager.uint64_type)
1659                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1660                                         else if (target_type == TypeManager.int64_type){
1661                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1662                                         }
1663
1664                                         if (e != null){
1665                                                 Expression ci, ce;
1666
1667                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1668
1669                                                 if (ci != null)
1670                                                         return ci;
1671
1672                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1673                                                 if (ce != null)
1674                                                         return ce;
1675                                                 //
1676                                                 // We should always be able to go from an uint32
1677                                                 // implicitly or explicitly to the other integral
1678                                                 // types
1679                                                 //
1680                                                 throw new Exception ("Internal compiler error");
1681                                         }
1682                                 }
1683                         }
1684
1685                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1686                         if (ne != null)
1687                                 return ne;
1688
1689                         Error_CannotConvertType (loc, original_expr_type, target_type);
1690                         return null;
1691                 }
1692
1693                 /// <summary>
1694                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1695                 /// </summary>
1696                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1697                                                                   Type target_type, Location l)
1698                 {
1699                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1700
1701                         if (ne != null)
1702                                 return ne;
1703
1704                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1705                         if (ne != null)
1706                                 return ne;
1707
1708                         ne = ExplicitReferenceConversion (expr, target_type);
1709                         if (ne != null)
1710                                 return ne;
1711
1712                         Error_CannotConvertType (l, expr.Type, target_type);
1713                         return null;
1714                 }
1715         }
1716 }