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