mcs/gmcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  23                 {
  24                         Report.Error (30, loc, "Cannot convert type '" +
  25                                       TypeManager.CSharpName (source) + "' to '" +
  26                                       TypeManager.CSharpName (target) + "'");
  27                 }
  28
  29                 static EmptyExpression MyEmptyExpr;
  30                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  31                 {
  32                         Type expr_type = expr.Type;
  33
  34                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  35                                 // if we are a method group, emit a warning
  36
  37                                 expr.Emit (null);
  38                         }
  39
  40                         //
  41                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  42                         // is an abstract class, and not really a value type, so we apply the same rules.
  43                         //
  44                         if (target_type == TypeManager.object_type) {
  45                                 //
  46                                 // A pointer type cannot be converted to object
  47                                 //
  48                                 if (expr_type.IsPointer)
  49                                         return null;
  50
  51                                 if (expr_type.IsValueType)
  52                                         return new BoxedCast (expr);
  53                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type)
  54                                         return new EmptyCast (expr, target_type);
  55                         } else if (target_type == TypeManager.value_type) {
  56                                 if (expr_type.IsValueType)
  57                                         return new BoxedCast (expr);
  58                                 if (expr is NullLiteral)
  59                                         return new BoxedCast (expr);
  60                         } else if (expr_type.IsSubclassOf (target_type)) {
  61                                 //
  62                                 // Special case: enumeration to System.Enum.
  63                                 // System.Enum is not a value type, it is a class, so we need
  64                                 // a boxing conversion
  65                                 //
  66                                 if (expr_type.IsEnum)
  67                                         return new BoxedCast (expr);
  68
  69                                 return new EmptyCast (expr, target_type);
  70                         } else {
  71
  72                                 // This code is kind of mirrored inside ImplicitStandardConversionExists
  73                                 // with the small distinction that we only probe there
  74                                 //
  75                                 // Always ensure that the code here and there is in sync
  76
  77                                 // from the null type to any reference-type.
  78                                 if (expr is NullLiteral){
  79                                         if (target_type.IsPointer)
  80                                                 return NullPointer.Null;
  81
  82                                         if (!target_type.IsValueType)
  83                                                 return new NullCast (expr, target_type);
  84                                 }
  85
  86                                 // from any class-type S to any interface-type T.
  87                                 if (target_type.IsInterface) {
  88                                         if (TypeManager.ImplementsInterface (expr_type, target_type)){
  89                                                 if (expr_type.IsClass)
  90                                                         return new EmptyCast (expr, target_type);
  91                                                 else if (expr_type.IsValueType)
  92                                                         return new BoxedCast (expr, target_type);
  93                                         }
  94                                 }
  95
  96                                 // from any interface type S to interface-type T.
  97                                 if (expr_type.IsInterface && target_type.IsInterface) {
  98                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
  99                                                 return new EmptyCast (expr, target_type);
 100                                         else
 101                                                 return null;
 102                                 }
 103
 104                                 // from an array-type S to an array-type of type T
 105                                 if (expr_type.IsArray && target_type.IsArray) {
 106                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 107
 108                                                 Type expr_element_type = TypeManager.GetElementType (expr_type);
 109
 110                                                 if (MyEmptyExpr == null)
 111                                                         MyEmptyExpr = new EmptyExpression ();
 112
 113                                                 MyEmptyExpr.SetType (expr_element_type);
 114                                                 Type target_element_type = TypeManager.GetElementType (target_type);
 115
 116                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 117                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 118                                                                                       target_element_type))
 119                                                                 return new EmptyCast (expr, target_type);
 120                                         }
 121                                 }
 122
 123
 124                                 // from an array-type to System.Array
 125                                 if (expr_type.IsArray && target_type == TypeManager.array_type)
 126                                         return new EmptyCast (expr, target_type);
 127
 128                                 // from any delegate type to System.Delegate
 129                                 if ((expr_type == TypeManager.delegate_type ||
 130                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 131                                     target_type == TypeManager.delegate_type)
 132                                         return new EmptyCast (expr, target_type);
 133
 134                                 // from any array-type or delegate type into System.ICloneable.
 135                                 if (expr_type.IsArray ||
 136                                     expr_type == TypeManager.delegate_type ||
 137                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 138                                         if (target_type == TypeManager.icloneable_type)
 139                                                 return new EmptyCast (expr, target_type);
 140
 141                                 return null;
 142
 143                         }
 144
 145                         return null;
 146                 }
 147
 148                 //
 149                 // Tests whether an implicit reference conversion exists between expr_type
 150                 // and target_type
 151                 //
 152                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 153                 {
 154                         Type expr_type = expr.Type;
 155
 156                         //
 157                         // This is the boxed case.
 158                         //
 159                         if (target_type == TypeManager.object_type) {
 160                                 if (expr_type.IsClass || expr_type.IsValueType ||
 161                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 162                                         return true;
 163                         } else if (expr_type.IsSubclassOf (target_type)) {
 164                                 return true;
 165                         } else {
 166                                 // Please remember that all code below actually comes
 167                                 // from ImplicitReferenceConversion so make sure code remains in sync
 168
 169                                 // from any class-type S to any interface-type T.
 170                                 if (target_type.IsInterface) {
 171                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 172                                                 return true;
 173                                 }
 174
 175                                 // from any interface type S to interface-type T.
 176                                 if (expr_type.IsInterface && target_type.IsInterface)
 177                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 178                                                 return true;
 179
 180                                 // from an array-type S to an array-type of type T
 181                                 if (expr_type.IsArray && target_type.IsArray) {
 182                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 183
 184                                                 Type expr_element_type = expr_type.GetElementType ();
 185
 186                                                 if (MyEmptyExpr == null)
 187                                                         MyEmptyExpr = new EmptyExpression ();
 188
 189                                                 MyEmptyExpr.SetType (expr_element_type);
 190                                                 Type target_element_type = TypeManager.GetElementType (target_type);
 191
 192                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 193                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 194                                                                                       target_element_type))
 195                                                                 return true;
 196                                         }
 197                                 }
 198
 199                                 // from an array-type to System.Array
 200                                 if (expr_type.IsArray && (target_type == TypeManager.array_type))
 201                                         return true;
 202
 203                                 // from any delegate type to System.Delegate
 204                                 if ((expr_type == TypeManager.delegate_type ||
 205                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 206                                     target_type == TypeManager.delegate_type)
 207                                         if (target_type.IsAssignableFrom (expr_type))
 208                                                 return true;
 209
 210                                 // from any array-type or delegate type into System.ICloneable.
 211                                 if (expr_type.IsArray ||
 212                                     expr_type == TypeManager.delegate_type ||
 213                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 214                                         if (target_type == TypeManager.icloneable_type)
 215                                                 return true;
 216
 217                                 // from the null type to any reference-type.
 218                                 if (expr is NullLiteral && !target_type.IsValueType &&
 219                                     !TypeManager.IsEnumType (target_type))
 220                                         return true;
 221
 222                         }
 223                         return false;
 224                 }
 225
 226                 /// <summary>
 227                 ///   Implicit Numeric Conversions.
 228                 ///
 229                 ///   expr is the expression to convert, returns a new expression of type
 230                 ///   target_type or null if an implicit conversion is not possible.
 231                 /// </summary>
 232                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 233                                                                     Type target_type, Location loc)
 234                 {
 235                         Type expr_type = expr.Type;
 236
 237                         //
 238                         // Attempt to do the implicit constant expression conversions
 239
 240                         if (expr is Constant){
 241
 242                                 if (expr is IntConstant){
 243                                         Expression e;
 244
 245                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 246
 247                                         if (e != null)
 248                                                 return e;
 249                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 250                                         //
 251                                         // Try the implicit constant expression conversion
 252                                         // from long to ulong, instead of a nice routine,
 253                                         // we just inline it
 254                                         //
 255                                         long v = ((LongConstant) expr).Value;
 256                                         if (v > 0)
 257                                                 return new ULongConstant ((ulong) v);
 258                                 }
 259                         }
 260
 261                         Type real_target_type = target_type;
 262
 263                         if (expr_type == TypeManager.sbyte_type){
 264                                 //
 265                                 // From sbyte to short, int, long, float, double.
 266                                 //
 267                                 if (real_target_type == TypeManager.int32_type)
 268                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 269                                 if (real_target_type == TypeManager.int64_type)
 270                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 271                                 if (real_target_type == TypeManager.double_type)
 272                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 273                                 if (real_target_type == TypeManager.float_type)
 274                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 275                                 if (real_target_type == TypeManager.short_type)
 276                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 277                         } else if (expr_type == TypeManager.byte_type){
 278                                 //
 279                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 280                                 //
 281                                 if ((real_target_type == TypeManager.short_type) ||
 282                                     (real_target_type == TypeManager.ushort_type) ||
 283                                     (real_target_type == TypeManager.int32_type) ||
 284                                     (real_target_type == TypeManager.uint32_type))
 285                                         return new EmptyCast (expr, target_type);
 286
 287                                 if (real_target_type == TypeManager.uint64_type)
 288                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 289                                 if (real_target_type == TypeManager.int64_type)
 290                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 291                                 if (real_target_type == TypeManager.float_type)
 292                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 293                                 if (real_target_type == TypeManager.double_type)
 294                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 295                         } else if (expr_type == TypeManager.short_type){
 296                                 //
 297                                 // From short to int, long, float, double
 298                                 //
 299                                 if (real_target_type == TypeManager.int32_type)
 300                                         return new EmptyCast (expr, target_type);
 301                                 if (real_target_type == TypeManager.int64_type)
 302                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 303                                 if (real_target_type == TypeManager.double_type)
 304                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 305                                 if (real_target_type == TypeManager.float_type)
 306                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 307                         } else if (expr_type == TypeManager.ushort_type){
 308                                 //
 309                                 // From ushort to int, uint, long, ulong, float, double
 310                                 //
 311                                 if (real_target_type == TypeManager.uint32_type)
 312                                         return new EmptyCast (expr, target_type);
 313
 314                                 if (real_target_type == TypeManager.uint64_type)
 315                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 316                                 if (real_target_type == TypeManager.int32_type)
 317                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 318                                 if (real_target_type == TypeManager.int64_type)
 319                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 320                                 if (real_target_type == TypeManager.double_type)
 321                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 322                                 if (real_target_type == TypeManager.float_type)
 323                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 324                         } else if (expr_type == TypeManager.int32_type){
 325                                 //
 326                                 // From int to long, float, double
 327                                 //
 328                                 if (real_target_type == TypeManager.int64_type)
 329                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 330                                 if (real_target_type == TypeManager.double_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 332                                 if (real_target_type == TypeManager.float_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 334                         } else if (expr_type == TypeManager.uint32_type){
 335                                 //
 336                                 // From uint to long, ulong, float, double
 337                                 //
 338                                 if (real_target_type == TypeManager.int64_type)
 339                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 340                                 if (real_target_type == TypeManager.uint64_type)
 341                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 342                                 if (real_target_type == TypeManager.double_type)
 343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 344                                                                OpCodes.Conv_R8);
 345                                 if (real_target_type == TypeManager.float_type)
 346                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 347                                                                OpCodes.Conv_R4);
 348                         } else if (expr_type == TypeManager.int64_type){
 349                                 //
 350                                 // From long/ulong to float, double
 351                                 //
 352                                 if (real_target_type == TypeManager.double_type)
 353                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 354                                 if (real_target_type == TypeManager.float_type)
 355                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 356                         } else if (expr_type == TypeManager.uint64_type){
 357                                 //
 358                                 // From ulong to float, double
 359                                 //
 360                                 if (real_target_type == TypeManager.double_type)
 361                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 362                                                                OpCodes.Conv_R8);
 363                                 if (real_target_type == TypeManager.float_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 365                                                                OpCodes.Conv_R4);
 366                         } else if (expr_type == TypeManager.char_type){
 367                                 //
 368                                 // From char to ushort, int, uint, long, ulong, float, double
 369                                 //
 370                                 if ((real_target_type == TypeManager.ushort_type) ||
 371                                     (real_target_type == TypeManager.int32_type) ||
 372                                     (real_target_type == TypeManager.uint32_type))
 373                                         return new EmptyCast (expr, target_type);
 374                                 if (real_target_type == TypeManager.uint64_type)
 375                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 376                                 if (real_target_type == TypeManager.int64_type)
 377                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 378                                 if (real_target_type == TypeManager.float_type)
 379                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 380                                 if (real_target_type == TypeManager.double_type)
 381                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 382                         } else if (expr_type == TypeManager.float_type){
 383                                 //
 384                                 // float to double
 385                                 //
 386                                 if (real_target_type == TypeManager.double_type)
 387                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 388                         }
 389
 390                         return null;
 391                 }
 392
 393
 394                 /// <summary>
 395                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 396                 ///  implicit user defined conversions - needed for overload resolution
 397                 /// </summary>
 398                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 399                 {
 400                         if (ImplicitStandardConversionExists (expr, target_type))
 401                                 return true;
 402
 403                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 404
 405                         if (dummy != null)
 406                                 return true;
 407
 408                         return false;
 409                 }
 410
 411                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 412                 {
 413                         Expression dummy = ImplicitUserConversion (
 414                                 ec, new EmptyExpression (source), target, Location.Null);
 415                         return dummy != null;
 416                 }
 417
 418                 /// <summary>
 419                 ///  Determines if a standard implicit conversion exists from
 420                 ///  expr_type to target_type
 421                 /// </summary>
 422                 public static bool ImplicitStandardConversionExists (Expression expr, Type target_type)
 423                 {
 424                         Type expr_type = expr.Type;
 425
 426                         if (expr_type == TypeManager.void_type)
 427                                 return false;
 428
 429                         //Console.WriteLine ("Expr is {0}", expr);
 430                         //Console.WriteLine ("{0} -> {1} ?", expr_type, target_type);
 431                         if (expr_type == target_type)
 432                                 return true;
 433
 434                         //Console.WriteLine ("No !!");
 435
 436                         // First numeric conversions
 437
 438                         if (expr_type == TypeManager.sbyte_type){
 439                                 //
 440                                 // From sbyte to short, int, long, float, double.
 441                                 //
 442                                 if ((target_type == TypeManager.int32_type) ||
 443                                     (target_type == TypeManager.int64_type) ||
 444                                     (target_type == TypeManager.double_type) ||
 445                                     (target_type == TypeManager.float_type)  ||
 446                                     (target_type == TypeManager.short_type) ||
 447                                     (target_type == TypeManager.decimal_type))
 448                                         return true;
 449
 450                         } else if (expr_type == TypeManager.byte_type){
 451                                 //
 452                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 453                                 //
 454                                 if ((target_type == TypeManager.short_type) ||
 455                                     (target_type == TypeManager.ushort_type) ||
 456                                     (target_type == TypeManager.int32_type) ||
 457                                     (target_type == TypeManager.uint32_type) ||
 458                                     (target_type == TypeManager.uint64_type) ||
 459                                     (target_type == TypeManager.int64_type) ||
 460                                     (target_type == TypeManager.float_type) ||
 461                                     (target_type == TypeManager.double_type) ||
 462                                     (target_type == TypeManager.decimal_type))
 463                                         return true;
 464
 465                         } else if (expr_type == TypeManager.short_type){
 466                                 //
 467                                 // From short to int, long, float, double
 468                                 //
 469                                 if ((target_type == TypeManager.int32_type) ||
 470                                     (target_type == TypeManager.int64_type) ||
 471                                     (target_type == TypeManager.double_type) ||
 472                                     (target_type == TypeManager.float_type) ||
 473                                     (target_type == TypeManager.decimal_type))
 474                                         return true;
 475
 476                         } else if (expr_type == TypeManager.ushort_type){
 477                                 //
 478                                 // From ushort to int, uint, long, ulong, float, double
 479                                 //
 480                                 if ((target_type == TypeManager.uint32_type) ||
 481                                     (target_type == TypeManager.uint64_type) ||
 482                                     (target_type == TypeManager.int32_type) ||
 483                                     (target_type == TypeManager.int64_type) ||
 484                                     (target_type == TypeManager.double_type) ||
 485                                     (target_type == TypeManager.float_type) ||
 486                                     (target_type == TypeManager.decimal_type))
 487                                         return true;
 488
 489                         } else if (expr_type == TypeManager.int32_type){
 490                                 //
 491                                 // From int to long, float, double
 492                                 //
 493                                 if ((target_type == TypeManager.int64_type) ||
 494                                     (target_type == TypeManager.double_type) ||
 495                                     (target_type == TypeManager.float_type) ||
 496                                     (target_type == TypeManager.decimal_type))
 497                                         return true;
 498
 499                         } else if (expr_type == TypeManager.uint32_type){
 500                                 //
 501                                 // From uint to long, ulong, float, double
 502                                 //
 503                                 if ((target_type == TypeManager.int64_type) ||
 504                                     (target_type == TypeManager.uint64_type) ||
 505                                     (target_type == TypeManager.double_type) ||
 506                                     (target_type == TypeManager.float_type) ||
 507                                     (target_type == TypeManager.decimal_type))
 508                                         return true;
 509
 510                         } else if ((expr_type == TypeManager.uint64_type) ||
 511                                    (expr_type == TypeManager.int64_type)) {
 512                                 //
 513                                 // From long/ulong to float, double
 514                                 //
 515                                 if ((target_type == TypeManager.double_type) ||
 516                                     (target_type == TypeManager.float_type) ||
 517                                     (target_type == TypeManager.decimal_type))
 518                                         return true;
 519
 520                         } else if (expr_type == TypeManager.char_type){
 521                                 //
 522                                 // From char to ushort, int, uint, long, ulong, float, double
 523                                 //
 524                                 if ((target_type == TypeManager.ushort_type) ||
 525                                     (target_type == TypeManager.int32_type) ||
 526                                     (target_type == TypeManager.uint32_type) ||
 527                                     (target_type == TypeManager.uint64_type) ||
 528                                     (target_type == TypeManager.int64_type) ||
 529                                     (target_type == TypeManager.float_type) ||
 530                                     (target_type == TypeManager.double_type) ||
 531                                     (target_type == TypeManager.decimal_type))
 532                                         return true;
 533
 534                         } else if (expr_type == TypeManager.float_type){
 535                                 //
 536                                 // float to double
 537                                 //
 538                                 if (target_type == TypeManager.double_type)
 539                                         return true;
 540                         }
 541
 542                         if (ImplicitReferenceConversionExists (expr, target_type))
 543                                 return true;
 544
 545                         if (expr is IntConstant){
 546                                 int value = ((IntConstant) expr).Value;
 547
 548                                 if (target_type == TypeManager.sbyte_type){
 549                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 550                                                 return true;
 551                                 } else if (target_type == TypeManager.byte_type){
 552                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 553                                                 return true;
 554                                 } else if (target_type == TypeManager.short_type){
 555                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 556                                                 return true;
 557                                 } else if (target_type == TypeManager.ushort_type){
 558                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 559                                                 return true;
 560                                 } else if (target_type == TypeManager.uint32_type){
 561                                         if (value >= 0)
 562                                                 return true;
 563                                 } else if (target_type == TypeManager.uint64_type){
 564                                          //
 565                                          // we can optimize this case: a positive int32
 566                                          // always fits on a uint64.  But we need an opcode
 567                                          // to do it.
 568                                          //
 569                                         if (value >= 0)
 570                                                 return true;
 571                                 }
 572
 573                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 574                                         return true;
 575                         }
 576
 577                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 578                                 //
 579                                 // Try the implicit constant expression conversion
 580                                 // from long to ulong, instead of a nice routine,
 581                                 // we just inline it
 582                                 //
 583                                 long v = ((LongConstant) expr).Value;
 584                                 if (v > 0)
 585                                         return true;
 586                         }
 587
 588                         if ((target_type == TypeManager.enum_type ||
 589                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 590                              expr is IntLiteral){
 591                                 IntLiteral i = (IntLiteral) expr;
 592
 593                                 if (i.Value == 0)
 594                                         return true;
 595                         }
 596
 597                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 598                                 return true;
 599
 600                         return false;
 601                 }
 602
 603                 //
 604                 // Used internally by FindMostEncompassedType, this is used
 605                 // to avoid creating lots of objects in the tight loop inside
 606                 // FindMostEncompassedType
 607                 //
 608                 static EmptyExpression priv_fmet_param;
 609
 610                 /// <summary>
 611                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 612                 ///  amongst the methods in the MethodGroupExpr
 613                 /// </summary>
 614                 static Type FindMostEncompassedType (ArrayList types)
 615                 {
 616                         Type best = null;
 617
 618                         if (priv_fmet_param == null)
 619                                 priv_fmet_param = new EmptyExpression ();
 620
 621                         foreach (Type t in types){
 622                                 priv_fmet_param.SetType (t);
 623
 624                                 if (best == null) {
 625                                         best = t;
 626                                         continue;
 627                                 }
 628
 629                                 if (ImplicitStandardConversionExists (priv_fmet_param, best))
 630                                         best = t;
 631                         }
 632
 633                         return best;
 634                 }
 635
 636                 //
 637                 // Used internally by FindMostEncompassingType, this is used
 638                 // to avoid creating lots of objects in the tight loop inside
 639                 // FindMostEncompassingType
 640                 //
 641                 static EmptyExpression priv_fmee_ret;
 642
 643                 /// <summary>
 644                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 645                 ///  amongst the types in the given set
 646                 /// </summary>
 647                 static Type FindMostEncompassingType (ArrayList types)
 648                 {
 649                         Type best = null;
 650
 651                         if (priv_fmee_ret == null)
 652                                 priv_fmee_ret = new EmptyExpression ();
 653
 654                         foreach (Type t in types){
 655                                 priv_fmee_ret.SetType (best);
 656
 657                                 if (best == null) {
 658                                         best = t;
 659                                         continue;
 660                                 }
 661
 662                                 if (ImplicitStandardConversionExists (priv_fmee_ret, t))
 663                                         best = t;
 664                         }
 665
 666                         return best;
 667                 }
 668
 669                 //
 670                 // Used to avoid creating too many objects
 671                 //
 672                 static EmptyExpression priv_fms_expr;
 673
 674                 /// <summary>
 675                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 676                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 677                 ///   for explicit and implicit conversion operators.
 678                 /// </summary>
 679                 static public Type FindMostSpecificSource (MethodGroupExpr me, Expression source,
 680                                                            bool apply_explicit_conv_rules,
 681                                                            Location loc)
 682                 {
 683                         ArrayList src_types_set = new ArrayList ();
 684
 685                         if (priv_fms_expr == null)
 686                                 priv_fms_expr = new EmptyExpression ();
 687
 688                         //
 689                         // If any operator converts from S then Sx = S
 690                         //
 691                         Type source_type = source.Type;
 692                         foreach (MethodBase mb in me.Methods){
 693                                 ParameterData pd = Invocation.GetParameterData (mb);
 694                                 Type param_type = pd.ParameterType (0);
 695
 696                                 if (param_type == source_type)
 697                                         return param_type;
 698
 699                                 if (apply_explicit_conv_rules) {
 700                                         //
 701                                         // From the spec :
 702                                         // Find the set of applicable user-defined conversion operators, U.  This set
 703                                         // consists of the
 704                                         // user-defined implicit or explicit conversion operators declared by
 705                                         // the classes or structs in D that convert from a type encompassing
 706                                         // or encompassed by S to a type encompassing or encompassed by T
 707                                         //
 708                                         priv_fms_expr.SetType (param_type);
 709                                         if (ImplicitStandardConversionExists (priv_fms_expr, source_type))
 710                                                 src_types_set.Add (param_type);
 711                                         else {
 712                                                 if (ImplicitStandardConversionExists (source, param_type))
 713                                                         src_types_set.Add (param_type);
 714                                         }
 715                                 } else {
 716                                         //
 717                                         // Only if S is encompassed by param_type
 718                                         //
 719                                         if (ImplicitStandardConversionExists (source, param_type))
 720                                                 src_types_set.Add (param_type);
 721                                 }
 722                         }
 723
 724                         //
 725                         // Explicit Conv rules
 726                         //
 727                         if (apply_explicit_conv_rules) {
 728                                 ArrayList candidate_set = new ArrayList ();
 729
 730                                 foreach (Type param_type in src_types_set){
 731                                         if (ImplicitStandardConversionExists (source, param_type))
 732                                                 candidate_set.Add (param_type);
 733                                 }
 734
 735                                 if (candidate_set.Count != 0)
 736                                         return FindMostEncompassedType (candidate_set);
 737                         }
 738
 739                         //
 740                         // Final case
 741                         //
 742                         if (apply_explicit_conv_rules)
 743                                 return FindMostEncompassingType (src_types_set);
 744                         else
 745                                 return FindMostEncompassedType (src_types_set);
 746                 }
 747
 748                 //
 749                 // Useful in avoiding proliferation of objects
 750                 //
 751                 static EmptyExpression priv_fmt_expr;
 752
 753                 /// <summary>
 754                 ///  Finds the most specific target Tx according to section 13.4.4
 755                 /// </summary>
 756                 static public Type FindMostSpecificTarget (MethodGroupExpr me, Type target,
 757                                                            bool apply_explicit_conv_rules,
 758                                                            Location loc)
 759                 {
 760                         ArrayList tgt_types_set = new ArrayList ();
 761
 762                         if (priv_fmt_expr == null)
 763                                 priv_fmt_expr = new EmptyExpression ();
 764
 765                         //
 766                         // If any operator converts to T then Tx = T
 767                         //
 768                         foreach (MethodInfo mi in me.Methods){
 769                                 Type ret_type = mi.ReturnType;
 770
 771                                 if (ret_type == target)
 772                                         return ret_type;
 773
 774                                 if (apply_explicit_conv_rules) {
 775                                         //
 776                                         // From the spec :
 777                                         // Find the set of applicable user-defined conversion operators, U.
 778                                         //
 779                                         // This set consists of the
 780                                         // user-defined implicit or explicit conversion operators declared by
 781                                         // the classes or structs in D that convert from a type encompassing
 782                                         // or encompassed by S to a type encompassing or encompassed by T
 783                                         //
 784                                         priv_fms_expr.SetType (ret_type);
 785                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 786                                                 tgt_types_set.Add (ret_type);
 787                                         else {
 788                                                 priv_fms_expr.SetType (target);
 789                                                 if (ImplicitStandardConversionExists (priv_fms_expr, ret_type))
 790                                                         tgt_types_set.Add (ret_type);
 791                                         }
 792                                 } else {
 793                                         //
 794                                         // Only if T is encompassed by param_type
 795                                         //
 796                                         priv_fms_expr.SetType (ret_type);
 797                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 798                                                 tgt_types_set.Add (ret_type);
 799                                 }
 800                         }
 801
 802                         //
 803                         // Explicit conv rules
 804                         //
 805                         if (apply_explicit_conv_rules) {
 806                                 ArrayList candidate_set = new ArrayList ();
 807
 808                                 foreach (Type ret_type in tgt_types_set){
 809                                         priv_fmt_expr.SetType (ret_type);
 810
 811                                         if (ImplicitStandardConversionExists (priv_fmt_expr, target))
 812                                                 candidate_set.Add (ret_type);
 813                                 }
 814
 815                                 if (candidate_set.Count != 0)
 816                                         return FindMostEncompassingType (candidate_set);
 817                         }
 818
 819                         //
 820                         // Okay, final case !
 821                         //
 822                         if (apply_explicit_conv_rules)
 823                                 return FindMostEncompassedType (tgt_types_set);
 824                         else
 825                                 return FindMostEncompassingType (tgt_types_set);
 826                 }
 827
 828                 /// <summary>
 829                 ///  User-defined Implicit conversions
 830                 /// </summary>
 831                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 832                                                                  Type target, Location loc)
 833                 {
 834                         return UserDefinedConversion (ec, source, target, loc, false);
 835                 }
 836
 837                 /// <summary>
 838                 ///  User-defined Explicit conversions
 839                 /// </summary>
 840                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 841                                                                  Type target, Location loc)
 842                 {
 843                         return UserDefinedConversion (ec, source, target, loc, true);
 844                 }
 845
 846                 /// <summary>
 847                 ///   Computes the MethodGroup for the user-defined conversion
 848                 ///   operators from source_type to target_type.  `look_for_explicit'
 849                 ///   controls whether we should also include the list of explicit
 850                 ///   operators
 851                 /// </summary>
 852                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
 853                                                                Type source_type, Type target_type,
 854                                                                Location loc, bool look_for_explicit)
 855                 {
 856                         Expression mg1 = null, mg2 = null;
 857                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 858                         string op_name;
 859
 860                         op_name = "op_Implicit";
 861
 862                         MethodGroupExpr union3;
 863
 864                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
 865                         if (source_type.BaseType != null)
 866                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 867
 868                         if (mg1 == null)
 869                                 union3 = (MethodGroupExpr) mg2;
 870                         else if (mg2 == null)
 871                                 union3 = (MethodGroupExpr) mg1;
 872                         else
 873                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
 874
 875                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
 876                         if (mg1 != null){
 877                                 if (union3 != null)
 878                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 879                                 else
 880                                         union3 = (MethodGroupExpr) mg1;
 881                         }
 882
 883                         if (target_type.BaseType != null)
 884                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 885
 886                         if (mg1 != null){
 887                                 if (union3 != null)
 888                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 889                                 else
 890                                         union3 = (MethodGroupExpr) mg1;
 891                         }
 892
 893                         MethodGroupExpr union4 = null;
 894
 895                         if (look_for_explicit) {
 896                                 op_name = "op_Explicit";
 897
 898                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
 899                                 if (source_type.BaseType != null)
 900                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 901
 902                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
 903                                 if (target_type.BaseType != null)
 904                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 905
 906                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
 907                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
 908
 909                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
 910                         }
 911
 912                         return Invocation.MakeUnionSet (union3, union4, loc);
 913                 }
 914
 915                 /// <summary>
 916                 ///   User-defined conversions
 917                 /// </summary>
 918                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 919                                                                 Type target, Location loc,
 920                                                                 bool look_for_explicit)
 921                 {
 922                         MethodGroupExpr union;
 923                         Type source_type = source.Type;
 924                         MethodBase method = null;
 925
 926                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
 927                         if (union == null)
 928                                 return null;
 929
 930                         Type most_specific_source, most_specific_target;
 931 #if BLAH
 932                         foreach (MethodBase m in union.Methods){
 933                                 Console.WriteLine ("Name: " + m.Name);
 934                                 Console.WriteLine ("    : " + ((MethodInfo)m).ReturnType);
 935                         }
 936 #endif
 937
 938                         most_specific_source = FindMostSpecificSource (union, source, look_for_explicit, loc);
 939                         if (most_specific_source == null)
 940                                 return null;
 941
 942                         most_specific_target = FindMostSpecificTarget (union, target, look_for_explicit, loc);
 943                         if (most_specific_target == null)
 944                                 return null;
 945
 946                         int count = 0;
 947
 948
 949                         foreach (MethodBase mb in union.Methods){
 950                                 ParameterData pd = Invocation.GetParameterData (mb);
 951                                 MethodInfo mi = (MethodInfo) mb;
 952
 953                                 if (pd.ParameterType (0) == most_specific_source &&
 954                                     mi.ReturnType == most_specific_target) {
 955                                         method = mb;
 956                                         count++;
 957                                 }
 958                         }
 959
 960                         if (method == null || count > 1)
 961                                 return null;
 962
 963
 964                         //
 965                         // This will do the conversion to the best match that we
 966                         // found.  Now we need to perform an implict standard conversion
 967                         // if the best match was not the type that we were requested
 968                         // by target.
 969                         //
 970                         if (look_for_explicit)
 971                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
 972                         else
 973                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
 974
 975                         if (source == null)
 976                                 return null;
 977
 978                         Expression e;
 979                         e =  new UserCast ((MethodInfo) method, source, loc);
 980                         if (e.Type != target){
 981                                 if (!look_for_explicit)
 982                                         e = ImplicitConversionStandard (ec, e, target, loc);
 983                                 else
 984                                         e = ExplicitConversionStandard (ec, e, target, loc);
 985                         }
 986
 987                         return e;
 988                 }
 989
 990                 /// <summary>
 991                 ///   Converts implicitly the resolved expression `expr' into the
 992                 ///   `target_type'.  It returns a new expression that can be used
 993                 ///   in a context that expects a `target_type'.
 994                 /// </summary>
 995                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
 996                                                           Type target_type, Location loc)
 997                 {
 998                         Type expr_type = expr.Type;
 999                         Expression e;
1000
1001                         if (target_type == null)
1002                                 throw new Exception ("Target type is null");
1003
1004                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1005                         if (e != null)
1006                                 return e;
1007
1008                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1009                         if (e != null)
1010                                 return e;
1011
1012                         return null;
1013                 }
1014
1015
1016                 /// <summary>
1017                 ///   Attempts to apply the `Standard Implicit
1018                 ///   Conversion' rules to the expression `expr' into
1019                 ///   the `target_type'.  It returns a new expression
1020                 ///   that can be used in a context that expects a
1021                 ///   `target_type'.
1022                 ///
1023                 ///   This is different from `ImplicitConversion' in that the
1024                 ///   user defined implicit conversions are excluded.
1025                 /// </summary>
1026                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1027                                                                      Type target_type, Location loc)
1028                 {
1029                         Type expr_type = expr.Type;
1030                         Expression e;
1031
1032                         if (expr_type == target_type && !(expr is NullLiteral))
1033                                 return expr;
1034
1035                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1036                         if (e != null)
1037                                 return e;
1038
1039                         e = ImplicitReferenceConversion (expr, target_type);
1040                         if (e != null)
1041                                 return e;
1042
1043                         if ((target_type == TypeManager.enum_type ||
1044                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1045                             expr is IntLiteral){
1046                                 IntLiteral i = (IntLiteral) expr;
1047
1048                                 if (i.Value == 0)
1049                                         return new EnumConstant ((Constant) expr, target_type);
1050                         }
1051
1052                         if (ec.InUnsafe) {
1053                                 if (expr_type.IsPointer){
1054                                         if (target_type == TypeManager.void_ptr_type)
1055                                                 return new EmptyCast (expr, target_type);
1056
1057                                         //
1058                                         // yep, comparing pointer types cant be done with
1059                                         // t1 == t2, we have to compare their element types.
1060                                         //
1061                                         if (target_type.IsPointer){
1062                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1063                                                         return expr;
1064                                         }
1065                                 }
1066
1067                                 if (target_type.IsPointer) {
1068                                         if (expr is NullLiteral)
1069                                                 return new EmptyCast (expr, target_type);
1070
1071                                         if (expr_type == TypeManager.void_ptr_type)
1072                                                 return new EmptyCast (expr, target_type);
1073                                 }
1074                         }
1075
1076                         return null;
1077                 }
1078
1079                 /// <summary>
1080                 ///   Attemps to perform an implict constant conversion of the IntConstant
1081                 ///   into a different data type using casts (See Implicit Constant
1082                 ///   Expression Conversions)
1083                 /// </summary>
1084                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1085                 {
1086                         int value = ic.Value;
1087
1088                         if (target_type == TypeManager.sbyte_type){
1089                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1090                                         return new SByteConstant ((sbyte) value);
1091                         } else if (target_type == TypeManager.byte_type){
1092                                 if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
1093                                         return new ByteConstant ((byte) value);
1094                         } else if (target_type == TypeManager.short_type){
1095                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1096                                         return new ShortConstant ((short) value);
1097                         } else if (target_type == TypeManager.ushort_type){
1098                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1099                                         return new UShortConstant ((ushort) value);
1100                         } else if (target_type == TypeManager.uint32_type){
1101                                 if (value >= 0)
1102                                         return new UIntConstant ((uint) value);
1103                         } else if (target_type == TypeManager.uint64_type){
1104                                 //
1105                                 // we can optimize this case: a positive int32
1106                                 // always fits on a uint64.  But we need an opcode
1107                                 // to do it.
1108                                 //
1109                                 if (value >= 0)
1110                                         return new ULongConstant ((ulong) value);
1111                         } else if (target_type == TypeManager.double_type)
1112                                 return new DoubleConstant ((double) value);
1113                         else if (target_type == TypeManager.float_type)
1114                                 return new FloatConstant ((float) value);
1115
1116                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1117                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1118                                 Constant e = (Constant) ic;
1119
1120                                 //
1121                                 // Possibly, we need to create a different 0 literal before passing
1122                                 // to EnumConstant
1123                                 //n
1124                                 if (underlying == TypeManager.int64_type)
1125                                         e = new LongLiteral (0);
1126                                 else if (underlying == TypeManager.uint64_type)
1127                                         e = new ULongLiteral (0);
1128
1129                                 return new EnumConstant (e, target_type);
1130                         }
1131                         return null;
1132                 }
1133
1134                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1135                 {
1136                         string msg = "Cannot convert implicitly from `"+
1137                                 TypeManager.CSharpName (source) + "' to `" +
1138                                 TypeManager.CSharpName (target) + "'";
1139
1140                         Report.Error (29, loc, msg);
1141                 }
1142
1143                 /// <summary>
1144                 ///   Attemptes to implicityly convert `target' into `type', using
1145                 ///   ImplicitConversion.  If there is no implicit conversion, then
1146                 ///   an error is signaled
1147                 /// </summary>
1148                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1149                                                                      Type target_type, Location loc)
1150                 {
1151                         Expression e;
1152
1153                         e = ImplicitConversion (ec, source, target_type, loc);
1154                         if (e != null)
1155                                 return e;
1156
1157                         if (source is DoubleLiteral && target_type == TypeManager.float_type){
1158                                 Report.Error (664, loc,
1159                                               "Double literal cannot be implicitly converted to " +
1160                                               "float type, use F suffix to create a float literal");
1161                         }
1162
1163                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1164
1165                         return null;
1166                 }
1167
1168                 /// <summary>
1169                 ///   Performs the explicit numeric conversions
1170                 /// </summary>
1171                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1172                 {
1173                         Type expr_type = expr.Type;
1174
1175                         //
1176                         // If we have an enumeration, extract the underlying type,
1177                         // use this during the comparison, but wrap around the original
1178                         // target_type
1179                         //
1180                         Type real_target_type = target_type;
1181
1182                         if (TypeManager.IsEnumType (real_target_type))
1183                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1184
1185                         if (ImplicitStandardConversionExists (expr, real_target_type)){
1186                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1187
1188                                 if (real_target_type != target_type)
1189                                         return new EmptyCast (ce, target_type);
1190                                 return ce;
1191                         }
1192
1193                         if (expr_type == TypeManager.sbyte_type){
1194                                 //
1195                                 // From sbyte to byte, ushort, uint, ulong, char
1196                                 //
1197                                 if (real_target_type == TypeManager.byte_type)
1198                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1199                                 if (real_target_type == TypeManager.ushort_type)
1200                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1201                                 if (real_target_type == TypeManager.uint32_type)
1202                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1203                                 if (real_target_type == TypeManager.uint64_type)
1204                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1205                                 if (real_target_type == TypeManager.char_type)
1206                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1207                         } else if (expr_type == TypeManager.byte_type){
1208                                 //
1209                                 // From byte to sbyte and char
1210                                 //
1211                                 if (real_target_type == TypeManager.sbyte_type)
1212                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1213                                 if (real_target_type == TypeManager.char_type)
1214                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1215                         } else if (expr_type == TypeManager.short_type){
1216                                 //
1217                                 // From short to sbyte, byte, ushort, uint, ulong, char
1218                                 //
1219                                 if (real_target_type == TypeManager.sbyte_type)
1220                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1221                                 if (real_target_type == TypeManager.byte_type)
1222                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1223                                 if (real_target_type == TypeManager.ushort_type)
1224                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1225                                 if (real_target_type == TypeManager.uint32_type)
1226                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1227                                 if (real_target_type == TypeManager.uint64_type)
1228                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1229                                 if (real_target_type == TypeManager.char_type)
1230                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1231                         } else if (expr_type == TypeManager.ushort_type){
1232                                 //
1233                                 // From ushort to sbyte, byte, short, char
1234                                 //
1235                                 if (real_target_type == TypeManager.sbyte_type)
1236                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1237                                 if (real_target_type == TypeManager.byte_type)
1238                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1239                                 if (real_target_type == TypeManager.short_type)
1240                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1241                                 if (real_target_type == TypeManager.char_type)
1242                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1243                         } else if (expr_type == TypeManager.int32_type){
1244                                 //
1245                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1246                                 //
1247                                 if (real_target_type == TypeManager.sbyte_type)
1248                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1249                                 if (real_target_type == TypeManager.byte_type)
1250                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1251                                 if (real_target_type == TypeManager.short_type)
1252                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1253                                 if (real_target_type == TypeManager.ushort_type)
1254                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1255                                 if (real_target_type == TypeManager.uint32_type)
1256                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1257                                 if (real_target_type == TypeManager.uint64_type)
1258                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1259                                 if (real_target_type == TypeManager.char_type)
1260                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1261                         } else if (expr_type == TypeManager.uint32_type){
1262                                 //
1263                                 // From uint to sbyte, byte, short, ushort, int, char
1264                                 //
1265                                 if (real_target_type == TypeManager.sbyte_type)
1266                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1267                                 if (real_target_type == TypeManager.byte_type)
1268                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1269                                 if (real_target_type == TypeManager.short_type)
1270                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1271                                 if (real_target_type == TypeManager.ushort_type)
1272                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1273                                 if (real_target_type == TypeManager.int32_type)
1274                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1275                                 if (real_target_type == TypeManager.char_type)
1276                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1277                         } else if (expr_type == TypeManager.int64_type){
1278                                 //
1279                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1280                                 //
1281                                 if (real_target_type == TypeManager.sbyte_type)
1282                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1283                                 if (real_target_type == TypeManager.byte_type)
1284                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1285                                 if (real_target_type == TypeManager.short_type)
1286                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1287                                 if (real_target_type == TypeManager.ushort_type)
1288                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1289                                 if (real_target_type == TypeManager.int32_type)
1290                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1291                                 if (real_target_type == TypeManager.uint32_type)
1292                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1293                                 if (real_target_type == TypeManager.uint64_type)
1294                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1295                                 if (real_target_type == TypeManager.char_type)
1296                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1297                         } else if (expr_type == TypeManager.uint64_type){
1298                                 //
1299                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1300                                 //
1301                                 if (real_target_type == TypeManager.sbyte_type)
1302                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1303                                 if (real_target_type == TypeManager.byte_type)
1304                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1305                                 if (real_target_type == TypeManager.short_type)
1306                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1307                                 if (real_target_type == TypeManager.ushort_type)
1308                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1309                                 if (real_target_type == TypeManager.int32_type)
1310                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1311                                 if (real_target_type == TypeManager.uint32_type)
1312                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1313                                 if (real_target_type == TypeManager.int64_type)
1314                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1315                                 if (real_target_type == TypeManager.char_type)
1316                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1317                         } else if (expr_type == TypeManager.char_type){
1318                                 //
1319                                 // From char to sbyte, byte, short
1320                                 //
1321                                 if (real_target_type == TypeManager.sbyte_type)
1322                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1323                                 if (real_target_type == TypeManager.byte_type)
1324                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1325                                 if (real_target_type == TypeManager.short_type)
1326                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1327                         } else if (expr_type == TypeManager.float_type){
1328                                 //
1329                                 // From float to sbyte, byte, short,
1330                                 // ushort, int, uint, long, ulong, char
1331                                 // or decimal
1332                                 //
1333                                 if (real_target_type == TypeManager.sbyte_type)
1334                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1335                                 if (real_target_type == TypeManager.byte_type)
1336                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1337                                 if (real_target_type == TypeManager.short_type)
1338                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1339                                 if (real_target_type == TypeManager.ushort_type)
1340                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1341                                 if (real_target_type == TypeManager.int32_type)
1342                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1343                                 if (real_target_type == TypeManager.uint32_type)
1344                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1345                                 if (real_target_type == TypeManager.int64_type)
1346                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1347                                 if (real_target_type == TypeManager.uint64_type)
1348                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1349                                 if (real_target_type == TypeManager.char_type)
1350                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1351                         } else if (expr_type == TypeManager.double_type){
1352                                 //
1353                                 // From double to byte, byte, short,
1354                                 // ushort, int, uint, long, ulong,
1355                                 // char, float or decimal
1356                                 //
1357                                 if (real_target_type == TypeManager.sbyte_type)
1358                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1359                                 if (real_target_type == TypeManager.byte_type)
1360                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1361                                 if (real_target_type == TypeManager.short_type)
1362                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1363                                 if (real_target_type == TypeManager.ushort_type)
1364                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1365                                 if (real_target_type == TypeManager.int32_type)
1366                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1367                                 if (real_target_type == TypeManager.uint32_type)
1368                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1369                                 if (real_target_type == TypeManager.int64_type)
1370                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1371                                 if (real_target_type == TypeManager.uint64_type)
1372                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1373                                 if (real_target_type == TypeManager.char_type)
1374                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1375                                 if (real_target_type == TypeManager.float_type)
1376                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1377                         }
1378
1379                         // decimal is taken care of by the op_Explicit methods.
1380
1381                         return null;
1382                 }
1383
1384                 /// <summary>
1385                 ///  Returns whether an explicit reference conversion can be performed
1386                 ///  from source_type to target_type
1387                 /// </summary>
1388                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1389                 {
1390                         bool target_is_value_type = target_type.IsValueType;
1391
1392                         if (source_type == target_type)
1393                                 return true;
1394
1395                         //
1396                         // From object to any reference type
1397                         //
1398                         if (source_type == TypeManager.object_type && !target_is_value_type)
1399                                 return true;
1400
1401                         //
1402                         // From any class S to any class-type T, provided S is a base class of T
1403                         //
1404                         if (target_type.IsSubclassOf (source_type))
1405                                 return true;
1406
1407                         //
1408                         // From any interface type S to any interface T provided S is not derived from T
1409                         //
1410                         if (source_type.IsInterface && target_type.IsInterface){
1411                                 if (!target_type.IsSubclassOf (source_type))
1412                                         return true;
1413                         }
1414
1415                         //
1416                         // From any class type S to any interface T, provided S is not sealed
1417                         // and provided S does not implement T.
1418                         //
1419                         if (target_type.IsInterface && !source_type.IsSealed &&
1420                             !TypeManager.ImplementsInterface (source_type, target_type))
1421                                 return true;
1422
1423                         //
1424                         // From any interface-type S to to any class type T, provided T is not
1425                         // sealed, or provided T implements S.
1426                         //
1427                         if (source_type.IsInterface &&
1428                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1429                                 return true;
1430
1431
1432                         // From an array type S with an element type Se to an array type T with an
1433                         // element type Te provided all the following are true:
1434                         //     * S and T differe only in element type, in other words, S and T
1435                         //       have the same number of dimensions.
1436                         //     * Both Se and Te are reference types
1437                         //     * An explicit referenc conversions exist from Se to Te
1438                         //
1439                         if (source_type.IsArray && target_type.IsArray) {
1440                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1441
1442                                         Type source_element_type = TypeManager.GetElementType (source_type);
1443                                         Type target_element_type = TypeManager.GetElementType (target_type);
1444
1445                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1446                                                 if (ExplicitReferenceConversionExists (source_element_type,
1447                                                                                        target_element_type))
1448                                                         return true;
1449                                 }
1450                         }
1451
1452
1453                         // From System.Array to any array-type
1454                         if (source_type == TypeManager.array_type &&
1455                             target_type.IsArray){
1456                                 return true;
1457                         }
1458
1459                         //
1460                         // From System delegate to any delegate-type
1461                         //
1462                         if (source_type == TypeManager.delegate_type &&
1463                             target_type.IsSubclassOf (TypeManager.delegate_type))
1464                                 return true;
1465
1466                         //
1467                         // From ICloneable to Array or Delegate types
1468                         //
1469                         if (source_type == TypeManager.icloneable_type &&
1470                             (target_type == TypeManager.array_type ||
1471                              target_type == TypeManager.delegate_type))
1472                                 return true;
1473
1474                         return false;
1475                 }
1476
1477                 /// <summary>
1478                 ///   Implements Explicit Reference conversions
1479                 /// </summary>
1480                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1481                 {
1482                         Type source_type = source.Type;
1483                         bool target_is_value_type = target_type.IsValueType;
1484
1485                         //
1486                         // From object to any reference type
1487                         //
1488                         if (source_type == TypeManager.object_type && !target_is_value_type)
1489                                 return new ClassCast (source, target_type);
1490
1491
1492                         //
1493                         // From any class S to any class-type T, provided S is a base class of T
1494                         //
1495                         if (target_type.IsSubclassOf (source_type))
1496                                 return new ClassCast (source, target_type);
1497
1498                         //
1499                         // From any interface type S to any interface T provided S is not derived from T
1500                         //
1501                         if (source_type.IsInterface && target_type.IsInterface){
1502                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1503                                         return null;
1504                                 else
1505                                         return new ClassCast (source, target_type);
1506                         }
1507
1508                         //
1509                         // From any class type S to any interface T, provides S is not sealed
1510                         // and provided S does not implement T.
1511                         //
1512                         if (target_type.IsInterface && !source_type.IsSealed) {
1513                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1514                                         return null;
1515                                 else
1516                                         return new ClassCast (source, target_type);
1517
1518                         }
1519
1520                         //
1521                         // From any interface-type S to to any class type T, provided T is not
1522                         // sealed, or provided T implements S.
1523                         //
1524                         if (source_type.IsInterface) {
1525                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type))
1526                                         return new ClassCast (source, target_type);
1527                                 else
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, "Cannot convert null to value type `" +
1623                                                       TypeManager.CSharpName (expr_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 }