mcs/mcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  23                 {
  24                         Report.Error (30, loc, "Cannot convert type '" +
  25                                       TypeManager.CSharpName (source) + "' to '" +
  26                                       TypeManager.CSharpName (target) + "'");
  27                 }
  28
  29                 static EmptyExpression MyEmptyExpr;
  30                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  31                 {
  32                         Type expr_type = expr.Type;
  33
  34                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  35                                 // if we are a method group, emit a warning
  36
  37                                 expr.Emit (null);
  38                         }
  39
  40                         //
  41                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  42                         // is an abstract class, and not really a value type, so we apply the same rules.
  43                         //
  44                         if (target_type == TypeManager.object_type) {
  45                                 //
  46                                 // A pointer type cannot be converted to object
  47                                 //
  48                                 if (expr_type.IsPointer)
  49                                         return null;
  50
  51                                 if (expr_type.IsValueType)
  52                                         return new BoxedCast (expr);
  53                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type)
  54                                         return new EmptyCast (expr, target_type);
  55                         } else if (target_type == TypeManager.value_type) {
  56                                 if (expr_type.IsValueType)
  57                                         return new BoxedCast (expr);
  58                                 if (expr is NullLiteral)
  59                                         return new BoxedCast (expr);
  60                         } else if (expr_type.IsSubclassOf (target_type)) {
  61                                 //
  62                                 // Special case: enumeration to System.Enum.
  63                                 // System.Enum is not a value type, it is a class, so we need
  64                                 // a boxing conversion
  65                                 //
  66                                 if (expr_type.IsEnum)
  67                                         return new BoxedCast (expr);
  68
  69                                 return new EmptyCast (expr, target_type);
  70                         } else {
  71
  72                                 // This code is kind of mirrored inside ImplicitStandardConversionExists
  73                                 // with the small distinction that we only probe there
  74                                 //
  75                                 // Always ensure that the code here and there is in sync
  76
  77                                 // from the null type to any reference-type.
  78                                 if (expr is NullLiteral && !target_type.IsValueType)
  79                                         return new NullCast (expr, target_type);
  80
  81
  82                                 // from any class-type S to any interface-type T.
  83                                 if (target_type.IsInterface) {
  84                                         if (TypeManager.ImplementsInterface (expr_type, target_type)){
  85                                                 if (expr_type.IsClass)
  86                                                         return new EmptyCast (expr, target_type);
  87                                                 else if (expr_type.IsValueType)
  88                                                         return new BoxedCast (expr, target_type);
  89                                         }
  90                                 }
  91
  92                                 // from any interface type S to interface-type T.
  93                                 if (expr_type.IsInterface && target_type.IsInterface) {
  94                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
  95                                                 return new EmptyCast (expr, target_type);
  96                                         else
  97                                                 return null;
  98                                 }
  99
 100                                 // from an array-type S to an array-type of type T
 101                                 if (expr_type.IsArray && target_type.IsArray) {
 102                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 103
 104                                                 Type expr_element_type = expr_type.GetElementType ();
 105
 106                                                 if (MyEmptyExpr == null)
 107                                                         MyEmptyExpr = new EmptyExpression ();
 108
 109                                                 MyEmptyExpr.SetType (expr_element_type);
 110                                                 Type target_element_type = target_type.GetElementType ();
 111
 112                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 113                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 114                                                                                       target_element_type))
 115                                                                 return new EmptyCast (expr, target_type);
 116                                         }
 117                                 }
 118
 119
 120                                 // from an array-type to System.Array
 121                                 if (expr_type.IsArray && target_type == TypeManager.array_type)
 122                                         return new EmptyCast (expr, target_type);
 123
 124                                 // from any delegate type to System.Delegate
 125                                 if ((expr_type == TypeManager.delegate_type ||
 126                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 127                                     target_type == TypeManager.delegate_type)
 128                                         return new EmptyCast (expr, target_type);
 129
 130                                 // from any array-type or delegate type into System.ICloneable.
 131                                 if (expr_type.IsArray ||
 132                                     expr_type == TypeManager.delegate_type ||
 133                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 134                                         if (target_type == TypeManager.icloneable_type)
 135                                                 return new EmptyCast (expr, target_type);
 136
 137                                 return null;
 138
 139                         }
 140
 141                         return null;
 142                 }
 143
 144                 //
 145                 // Tests whether an implicit reference conversion exists between expr_type
 146                 // and target_type
 147                 //
 148                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 149                 {
 150                         Type expr_type = expr.Type;
 151
 152                         //
 153                         // This is the boxed case.
 154                         //
 155                         if (target_type == TypeManager.object_type) {
 156                                 if (expr_type.IsClass || expr_type.IsValueType ||
 157                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 158                                         return true;
 159                         } else if (expr_type.IsSubclassOf (target_type)) {
 160                                 return true;
 161                         } else {
 162                                 // Please remember that all code below actually comes
 163                                 // from ImplicitReferenceConversion so make sure code remains in sync
 164
 165                                 // from any class-type S to any interface-type T.
 166                                 if (target_type.IsInterface) {
 167                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 168                                                 return true;
 169                                 }
 170
 171                                 // from any interface type S to interface-type T.
 172                                 if (expr_type.IsInterface && target_type.IsInterface)
 173                                         if (TypeManager.ImplementsInterface (expr_type, target_type))
 174                                                 return true;
 175
 176                                 // from an array-type S to an array-type of type T
 177                                 if (expr_type.IsArray && target_type.IsArray) {
 178                                         if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 179
 180                                                 Type expr_element_type = expr_type.GetElementType ();
 181
 182                                                 if (MyEmptyExpr == null)
 183                                                         MyEmptyExpr = new EmptyExpression ();
 184
 185                                                 MyEmptyExpr.SetType (expr_element_type);
 186                                                 Type target_element_type = target_type.GetElementType ();
 187
 188                                                 if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 189                                                         if (ImplicitStandardConversionExists (MyEmptyExpr,
 190                                                                                       target_element_type))
 191                                                                 return true;
 192                                         }
 193                                 }
 194
 195                                 // from an array-type to System.Array
 196                                 if (expr_type.IsArray && (target_type == TypeManager.array_type))
 197                                         return true;
 198
 199                                 // from any delegate type to System.Delegate
 200                                 if ((expr_type == TypeManager.delegate_type ||
 201                                      expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 202                                     target_type == TypeManager.delegate_type)
 203                                         if (target_type.IsAssignableFrom (expr_type))
 204                                                 return true;
 205
 206                                 // from any array-type or delegate type into System.ICloneable.
 207                                 if (expr_type.IsArray ||
 208                                     expr_type == TypeManager.delegate_type ||
 209                                     expr_type.IsSubclassOf (TypeManager.delegate_type))
 210                                         if (target_type == TypeManager.icloneable_type)
 211                                                 return true;
 212
 213                                 // from the null type to any reference-type.
 214                                 if (expr is NullLiteral && !target_type.IsValueType &&
 215                                     !TypeManager.IsEnumType (target_type))
 216                                         return true;
 217
 218                         }
 219
 220                         return false;
 221                 }
 222
 223                 /// <summary>
 224                 ///   Implicit Numeric Conversions.
 225                 ///
 226                 ///   expr is the expression to convert, returns a new expression of type
 227                 ///   target_type or null if an implicit conversion is not possible.
 228                 /// </summary>
 229                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 230                                                                     Type target_type, Location loc)
 231                 {
 232                         Type expr_type = expr.Type;
 233
 234                         //
 235                         // Attempt to do the implicit constant expression conversions
 236
 237                         if (expr is Constant){
 238
 239                                 if (expr is IntConstant){
 240                                         Expression e;
 241
 242                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 243
 244                                         if (e != null)
 245                                                 return e;
 246                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 247                                         //
 248                                         // Try the implicit constant expression conversion
 249                                         // from long to ulong, instead of a nice routine,
 250                                         // we just inline it
 251                                         //
 252                                         long v = ((LongConstant) expr).Value;
 253                                         if (v > 0)
 254                                                 return new ULongConstant ((ulong) v);
 255                                 }
 256                         }
 257
 258                         Type real_target_type = target_type;
 259
 260                         if (expr_type == TypeManager.sbyte_type){
 261                                 //
 262                                 // From sbyte to short, int, long, float, double.
 263                                 //
 264                                 if (real_target_type == TypeManager.int32_type)
 265                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 266                                 if (real_target_type == TypeManager.int64_type)
 267                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 268                                 if (real_target_type == TypeManager.double_type)
 269                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 270                                 if (real_target_type == TypeManager.float_type)
 271                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 272                                 if (real_target_type == TypeManager.short_type)
 273                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 274                         } else if (expr_type == TypeManager.byte_type){
 275                                 //
 276                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 277                                 //
 278                                 if ((real_target_type == TypeManager.short_type) ||
 279                                     (real_target_type == TypeManager.ushort_type) ||
 280                                     (real_target_type == TypeManager.int32_type) ||
 281                                     (real_target_type == TypeManager.uint32_type))
 282                                         return new EmptyCast (expr, target_type);
 283
 284                                 if (real_target_type == TypeManager.uint64_type)
 285                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 286                                 if (real_target_type == TypeManager.int64_type)
 287                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 288                                 if (real_target_type == TypeManager.float_type)
 289                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 290                                 if (real_target_type == TypeManager.double_type)
 291                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 292                         } else if (expr_type == TypeManager.short_type){
 293                                 //
 294                                 // From short to int, long, float, double
 295                                 //
 296                                 if (real_target_type == TypeManager.int32_type)
 297                                         return new EmptyCast (expr, target_type);
 298                                 if (real_target_type == TypeManager.int64_type)
 299                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 300                                 if (real_target_type == TypeManager.double_type)
 301                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 302                                 if (real_target_type == TypeManager.float_type)
 303                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 304                         } else if (expr_type == TypeManager.ushort_type){
 305                                 //
 306                                 // From ushort to int, uint, long, ulong, float, double
 307                                 //
 308                                 if (real_target_type == TypeManager.uint32_type)
 309                                         return new EmptyCast (expr, target_type);
 310
 311                                 if (real_target_type == TypeManager.uint64_type)
 312                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 313                                 if (real_target_type == TypeManager.int32_type)
 314                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 315                                 if (real_target_type == TypeManager.int64_type)
 316                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 317                                 if (real_target_type == TypeManager.double_type)
 318                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 319                                 if (real_target_type == TypeManager.float_type)
 320                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 321                         } else if (expr_type == TypeManager.int32_type){
 322                                 //
 323                                 // From int to long, float, double
 324                                 //
 325                                 if (real_target_type == TypeManager.int64_type)
 326                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 327                                 if (real_target_type == TypeManager.double_type)
 328                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 329                                 if (real_target_type == TypeManager.float_type)
 330                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 331                         } else if (expr_type == TypeManager.uint32_type){
 332                                 //
 333                                 // From uint to long, ulong, float, double
 334                                 //
 335                                 if (real_target_type == TypeManager.int64_type)
 336                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 337                                 if (real_target_type == TypeManager.uint64_type)
 338                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 339                                 if (real_target_type == TypeManager.double_type)
 340                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 341                                                                OpCodes.Conv_R8);
 342                                 if (real_target_type == TypeManager.float_type)
 343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 344                                                                OpCodes.Conv_R4);
 345                         } else if (expr_type == TypeManager.int64_type){
 346                                 //
 347                                 // From long/ulong to float, double
 348                                 //
 349                                 if (real_target_type == TypeManager.double_type)
 350                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 351                                 if (real_target_type == TypeManager.float_type)
 352                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 353                         } else if (expr_type == TypeManager.uint64_type){
 354                                 //
 355                                 // From ulong to float, double
 356                                 //
 357                                 if (real_target_type == TypeManager.double_type)
 358                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 359                                                                OpCodes.Conv_R8);
 360                                 if (real_target_type == TypeManager.float_type)
 361                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 362                                                                OpCodes.Conv_R4);
 363                         } else if (expr_type == TypeManager.char_type){
 364                                 //
 365                                 // From char to ushort, int, uint, long, ulong, float, double
 366                                 //
 367                                 if ((real_target_type == TypeManager.ushort_type) ||
 368                                     (real_target_type == TypeManager.int32_type) ||
 369                                     (real_target_type == TypeManager.uint32_type))
 370                                         return new EmptyCast (expr, target_type);
 371                                 if (real_target_type == TypeManager.uint64_type)
 372                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 373                                 if (real_target_type == TypeManager.int64_type)
 374                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 375                                 if (real_target_type == TypeManager.float_type)
 376                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 377                                 if (real_target_type == TypeManager.double_type)
 378                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 379                         } else if (expr_type == TypeManager.float_type){
 380                                 //
 381                                 // float to double
 382                                 //
 383                                 if (real_target_type == TypeManager.double_type)
 384                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 385                         }
 386
 387                         return null;
 388                 }
 389
 390
 391                 /// <summary>
 392                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 393                 ///  implicit user defined conversions - needed for overload resolution
 394                 /// </summary>
 395                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 396                 {
 397                         if (ImplicitStandardConversionExists (expr, target_type) == true)
 398                                 return true;
 399
 400                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 401
 402                         if (dummy != null)
 403                                 return true;
 404
 405                         return false;
 406                 }
 407
 408                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 409                 {
 410                         Expression dummy = ImplicitUserConversion (
 411                                 ec, new EmptyExpression (source), target, Location.Null);
 412                         return dummy != null;
 413                 }
 414
 415                 /// <summary>
 416                 ///  Determines if a standard implicit conversion exists from
 417                 ///  expr_type to target_type
 418                 /// </summary>
 419                 public static bool ImplicitStandardConversionExists (Expression expr, Type target_type)
 420                 {
 421                         Type expr_type = expr.Type;
 422
 423                         if (expr_type == TypeManager.void_type)
 424                                 return false;
 425
 426                         if (expr_type == target_type)
 427                                 return true;
 428
 429                         // First numeric conversions
 430
 431                         if (expr_type == TypeManager.sbyte_type){
 432                                 //
 433                                 // From sbyte to short, int, long, float, double.
 434                                 //
 435                                 if ((target_type == TypeManager.int32_type) ||
 436                                     (target_type == TypeManager.int64_type) ||
 437                                     (target_type == TypeManager.double_type) ||
 438                                     (target_type == TypeManager.float_type)  ||
 439                                     (target_type == TypeManager.short_type) ||
 440                                     (target_type == TypeManager.decimal_type))
 441                                         return true;
 442
 443                         } else if (expr_type == TypeManager.byte_type){
 444                                 //
 445                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 446                                 //
 447                                 if ((target_type == TypeManager.short_type) ||
 448                                     (target_type == TypeManager.ushort_type) ||
 449                                     (target_type == TypeManager.int32_type) ||
 450                                     (target_type == TypeManager.uint32_type) ||
 451                                     (target_type == TypeManager.uint64_type) ||
 452                                     (target_type == TypeManager.int64_type) ||
 453                                     (target_type == TypeManager.float_type) ||
 454                                     (target_type == TypeManager.double_type) ||
 455                                     (target_type == TypeManager.decimal_type))
 456                                         return true;
 457
 458                         } else if (expr_type == TypeManager.short_type){
 459                                 //
 460                                 // From short to int, long, float, double
 461                                 //
 462                                 if ((target_type == TypeManager.int32_type) ||
 463                                     (target_type == TypeManager.int64_type) ||
 464                                     (target_type == TypeManager.double_type) ||
 465                                     (target_type == TypeManager.float_type) ||
 466                                     (target_type == TypeManager.decimal_type))
 467                                         return true;
 468
 469                         } else if (expr_type == TypeManager.ushort_type){
 470                                 //
 471                                 // From ushort to int, uint, long, ulong, float, double
 472                                 //
 473                                 if ((target_type == TypeManager.uint32_type) ||
 474                                     (target_type == TypeManager.uint64_type) ||
 475                                     (target_type == TypeManager.int32_type) ||
 476                                     (target_type == TypeManager.int64_type) ||
 477                                     (target_type == TypeManager.double_type) ||
 478                                     (target_type == TypeManager.float_type) ||
 479                                     (target_type == TypeManager.decimal_type))
 480                                         return true;
 481
 482                         } else if (expr_type == TypeManager.int32_type){
 483                                 //
 484                                 // From int to long, float, double
 485                                 //
 486                                 if ((target_type == TypeManager.int64_type) ||
 487                                     (target_type == TypeManager.double_type) ||
 488                                     (target_type == TypeManager.float_type) ||
 489                                     (target_type == TypeManager.decimal_type))
 490                                         return true;
 491
 492                         } else if (expr_type == TypeManager.uint32_type){
 493                                 //
 494                                 // From uint to long, ulong, float, double
 495                                 //
 496                                 if ((target_type == TypeManager.int64_type) ||
 497                                     (target_type == TypeManager.uint64_type) ||
 498                                     (target_type == TypeManager.double_type) ||
 499                                     (target_type == TypeManager.float_type) ||
 500                                     (target_type == TypeManager.decimal_type))
 501                                         return true;
 502
 503                         } else if ((expr_type == TypeManager.uint64_type) ||
 504                                    (expr_type == TypeManager.int64_type)) {
 505                                 //
 506                                 // From long/ulong to float, double
 507                                 //
 508                                 if ((target_type == TypeManager.double_type) ||
 509                                     (target_type == TypeManager.float_type) ||
 510                                     (target_type == TypeManager.decimal_type))
 511                                         return true;
 512
 513                         } else if (expr_type == TypeManager.char_type){
 514                                 //
 515                                 // From char to ushort, int, uint, long, ulong, float, double
 516                                 //
 517                                 if ((target_type == TypeManager.ushort_type) ||
 518                                     (target_type == TypeManager.int32_type) ||
 519                                     (target_type == TypeManager.uint32_type) ||
 520                                     (target_type == TypeManager.uint64_type) ||
 521                                     (target_type == TypeManager.int64_type) ||
 522                                     (target_type == TypeManager.float_type) ||
 523                                     (target_type == TypeManager.double_type) ||
 524                                     (target_type == TypeManager.decimal_type))
 525                                         return true;
 526
 527                         } else if (expr_type == TypeManager.float_type){
 528                                 //
 529                                 // float to double
 530                                 //
 531                                 if (target_type == TypeManager.double_type)
 532                                         return true;
 533                         }
 534
 535                         if (ImplicitReferenceConversionExists (expr, target_type))
 536                                 return true;
 537
 538                         if (expr is IntConstant){
 539                                 int value = ((IntConstant) expr).Value;
 540
 541                                 if (target_type == TypeManager.sbyte_type){
 542                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 543                                                 return true;
 544                                 } else if (target_type == TypeManager.byte_type){
 545                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 546                                                 return true;
 547                                 } else if (target_type == TypeManager.short_type){
 548                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 549                                                 return true;
 550                                 } else if (target_type == TypeManager.ushort_type){
 551                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 552                                                 return true;
 553                                 } else if (target_type == TypeManager.uint32_type){
 554                                         if (value >= 0)
 555                                                 return true;
 556                                 } else if (target_type == TypeManager.uint64_type){
 557                                          //
 558                                          // we can optimize this case: a positive int32
 559                                          // always fits on a uint64.  But we need an opcode
 560                                          // to do it.
 561                                          //
 562                                         if (value >= 0)
 563                                                 return true;
 564                                 }
 565
 566                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 567                                         return true;
 568                         }
 569
 570                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 571                                 //
 572                                 // Try the implicit constant expression conversion
 573                                 // from long to ulong, instead of a nice routine,
 574                                 // we just inline it
 575                                 //
 576                                 long v = ((LongConstant) expr).Value;
 577                                 if (v > 0)
 578                                         return true;
 579                         }
 580
 581                         if ((target_type == TypeManager.enum_type ||
 582                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 583                              expr is IntLiteral){
 584                                 IntLiteral i = (IntLiteral) expr;
 585
 586                                 if (i.Value == 0)
 587                                         return true;
 588                         }
 589
 590                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 591                                 return true;
 592
 593                         return false;
 594                 }
 595
 596                 //
 597                 // Used internally by FindMostEncompassedType, this is used
 598                 // to avoid creating lots of objects in the tight loop inside
 599                 // FindMostEncompassedType
 600                 //
 601                 static EmptyExpression priv_fmet_param;
 602
 603                 /// <summary>
 604                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 605                 ///  amongst the methods in the MethodGroupExpr
 606                 /// </summary>
 607                 static Type FindMostEncompassedType (ArrayList types)
 608                 {
 609                         Type best = null;
 610
 611                         if (priv_fmet_param == null)
 612                                 priv_fmet_param = new EmptyExpression ();
 613
 614                         foreach (Type t in types){
 615                                 priv_fmet_param.SetType (t);
 616
 617                                 if (best == null) {
 618                                         best = t;
 619                                         continue;
 620                                 }
 621
 622                                 if (ImplicitStandardConversionExists (priv_fmet_param, best))
 623                                         best = t;
 624                         }
 625
 626                         return best;
 627                 }
 628
 629                 //
 630                 // Used internally by FindMostEncompassingType, this is used
 631                 // to avoid creating lots of objects in the tight loop inside
 632                 // FindMostEncompassingType
 633                 //
 634                 static EmptyExpression priv_fmee_ret;
 635
 636                 /// <summary>
 637                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 638                 ///  amongst the types in the given set
 639                 /// </summary>
 640                 static Type FindMostEncompassingType (ArrayList types)
 641                 {
 642                         Type best = null;
 643
 644                         if (priv_fmee_ret == null)
 645                                 priv_fmee_ret = new EmptyExpression ();
 646
 647                         foreach (Type t in types){
 648                                 priv_fmee_ret.SetType (best);
 649
 650                                 if (best == null) {
 651                                         best = t;
 652                                         continue;
 653                                 }
 654
 655                                 if (ImplicitStandardConversionExists (priv_fmee_ret, t))
 656                                         best = t;
 657                         }
 658
 659                         return best;
 660                 }
 661
 662                 //
 663                 // Used to avoid creating too many objects
 664                 //
 665                 static EmptyExpression priv_fms_expr;
 666
 667                 /// <summary>
 668                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 669                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 670                 ///   for explicit and implicit conversion operators.
 671                 /// </summary>
 672                 static public Type FindMostSpecificSource (MethodGroupExpr me, Expression source,
 673                                                            bool apply_explicit_conv_rules,
 674                                                            Location loc)
 675                 {
 676                         ArrayList src_types_set = new ArrayList ();
 677
 678                         if (priv_fms_expr == null)
 679                                 priv_fms_expr = new EmptyExpression ();
 680
 681                         //
 682                         // If any operator converts from S then Sx = S
 683                         //
 684                         Type source_type = source.Type;
 685                         foreach (MethodBase mb in me.Methods){
 686                                 ParameterData pd = Invocation.GetParameterData (mb);
 687                                 Type param_type = pd.ParameterType (0);
 688
 689                                 if (param_type == source_type)
 690                                         return param_type;
 691
 692                                 if (apply_explicit_conv_rules) {
 693                                         //
 694                                         // From the spec :
 695                                         // Find the set of applicable user-defined conversion operators, U.  This set
 696                                         // consists of the
 697                                         // user-defined implicit or explicit conversion operators declared by
 698                                         // the classes or structs in D that convert from a type encompassing
 699                                         // or encompassed by S to a type encompassing or encompassed by T
 700                                         //
 701                                         priv_fms_expr.SetType (param_type);
 702                                         if (ImplicitStandardConversionExists (priv_fms_expr, source_type))
 703                                                 src_types_set.Add (param_type);
 704                                         else {
 705                                                 if (ImplicitStandardConversionExists (source, param_type))
 706                                                         src_types_set.Add (param_type);
 707                                         }
 708                                 } else {
 709                                         //
 710                                         // Only if S is encompassed by param_type
 711                                         //
 712                                         if (ImplicitStandardConversionExists (source, param_type))
 713                                                 src_types_set.Add (param_type);
 714                                 }
 715                         }
 716
 717                         //
 718                         // Explicit Conv rules
 719                         //
 720                         if (apply_explicit_conv_rules) {
 721                                 ArrayList candidate_set = new ArrayList ();
 722
 723                                 foreach (Type param_type in src_types_set){
 724                                         if (ImplicitStandardConversionExists (source, param_type))
 725                                                 candidate_set.Add (param_type);
 726                                 }
 727
 728                                 if (candidate_set.Count != 0)
 729                                         return FindMostEncompassedType (candidate_set);
 730                         }
 731
 732                         //
 733                         // Final case
 734                         //
 735                         if (apply_explicit_conv_rules)
 736                                 return FindMostEncompassingType (src_types_set);
 737                         else
 738                                 return FindMostEncompassedType (src_types_set);
 739                 }
 740
 741                 //
 742                 // Useful in avoiding proliferation of objects
 743                 //
 744                 static EmptyExpression priv_fmt_expr;
 745
 746                 /// <summary>
 747                 ///  Finds the most specific target Tx according to section 13.4.4
 748                 /// </summary>
 749                 static public Type FindMostSpecificTarget (MethodGroupExpr me, Type target,
 750                                                            bool apply_explicit_conv_rules,
 751                                                            Location loc)
 752                 {
 753                         ArrayList tgt_types_set = new ArrayList ();
 754
 755                         if (priv_fmt_expr == null)
 756                                 priv_fmt_expr = new EmptyExpression ();
 757
 758                         //
 759                         // If any operator converts to T then Tx = T
 760                         //
 761                         foreach (MethodInfo mi in me.Methods){
 762                                 Type ret_type = mi.ReturnType;
 763
 764                                 if (ret_type == target)
 765                                         return ret_type;
 766
 767                                 if (apply_explicit_conv_rules) {
 768                                         //
 769                                         // From the spec :
 770                                         // Find the set of applicable user-defined conversion operators, U.
 771                                         //
 772                                         // This set consists of the
 773                                         // user-defined implicit or explicit conversion operators declared by
 774                                         // the classes or structs in D that convert from a type encompassing
 775                                         // or encompassed by S to a type encompassing or encompassed by T
 776                                         //
 777                                         priv_fms_expr.SetType (ret_type);
 778                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 779                                                 tgt_types_set.Add (ret_type);
 780                                         else {
 781                                                 priv_fms_expr.SetType (target);
 782                                                 if (ImplicitStandardConversionExists (priv_fms_expr, ret_type))
 783                                                         tgt_types_set.Add (ret_type);
 784                                         }
 785                                 } else {
 786                                         //
 787                                         // Only if T is encompassed by param_type
 788                                         //
 789                                         priv_fms_expr.SetType (ret_type);
 790                                         if (ImplicitStandardConversionExists (priv_fms_expr, target))
 791                                                 tgt_types_set.Add (ret_type);
 792                                 }
 793                         }
 794
 795                         //
 796                         // Explicit conv rules
 797                         //
 798                         if (apply_explicit_conv_rules) {
 799                                 ArrayList candidate_set = new ArrayList ();
 800
 801                                 foreach (Type ret_type in tgt_types_set){
 802                                         priv_fmt_expr.SetType (ret_type);
 803
 804                                         if (ImplicitStandardConversionExists (priv_fmt_expr, target))
 805                                                 candidate_set.Add (ret_type);
 806                                 }
 807
 808                                 if (candidate_set.Count != 0)
 809                                         return FindMostEncompassingType (candidate_set);
 810                         }
 811
 812                         //
 813                         // Okay, final case !
 814                         //
 815                         if (apply_explicit_conv_rules)
 816                                 return FindMostEncompassedType (tgt_types_set);
 817                         else
 818                                 return FindMostEncompassingType (tgt_types_set);
 819                 }
 820
 821                 /// <summary>
 822                 ///  User-defined Implicit conversions
 823                 /// </summary>
 824                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 825                                                                  Type target, Location loc)
 826                 {
 827                         return UserDefinedConversion (ec, source, target, loc, false);
 828                 }
 829
 830                 /// <summary>
 831                 ///  User-defined Explicit conversions
 832                 /// </summary>
 833                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 834                                                                  Type target, Location loc)
 835                 {
 836                         return UserDefinedConversion (ec, source, target, loc, true);
 837                 }
 838
 839                 /// <summary>
 840                 ///   Computes the MethodGroup for the user-defined conversion
 841                 ///   operators from source_type to target_type.  `look_for_explicit'
 842                 ///   controls whether we should also include the list of explicit
 843                 ///   operators
 844                 /// </summary>
 845                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
 846                                                                Type source_type, Type target_type,
 847                                                                Location loc, bool look_for_explicit)
 848                 {
 849                         Expression mg1 = null, mg2 = null;
 850                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 851                         string op_name;
 852
 853                         op_name = "op_Implicit";
 854
 855                         MethodGroupExpr union3;
 856
 857                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
 858                         if (source_type.BaseType != null)
 859                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 860
 861                         if (mg1 == null)
 862                                 union3 = (MethodGroupExpr) mg2;
 863                         else if (mg2 == null)
 864                                 union3 = (MethodGroupExpr) mg1;
 865                         else
 866                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
 867
 868                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
 869                         if (mg1 != null){
 870                                 if (union3 != null)
 871                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 872                                 else
 873                                         union3 = (MethodGroupExpr) mg1;
 874                         }
 875
 876                         if (target_type.BaseType != null)
 877                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 878
 879                         if (mg1 != null){
 880                                 if (union3 != null)
 881                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 882                                 else
 883                                         union3 = (MethodGroupExpr) mg1;
 884                         }
 885
 886                         MethodGroupExpr union4 = null;
 887
 888                         if (look_for_explicit) {
 889                                 op_name = "op_Explicit";
 890
 891                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
 892                                 if (source_type.BaseType != null)
 893                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 894
 895                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
 896                                 if (target_type.BaseType != null)
 897                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 898
 899                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
 900                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
 901
 902                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
 903                         }
 904
 905                         return Invocation.MakeUnionSet (union3, union4, loc);
 906                 }
 907
 908                 /// <summary>
 909                 ///   User-defined conversions
 910                 /// </summary>
 911                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 912                                                                 Type target, Location loc,
 913                                                                 bool look_for_explicit)
 914                 {
 915                         MethodGroupExpr union;
 916                         Type source_type = source.Type;
 917                         MethodBase method = null;
 918
 919                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
 920                         if (union == null)
 921                                 return null;
 922
 923                         Type most_specific_source, most_specific_target;
 924 #if BLAH
 925                         foreach (MethodBase m in union.Methods){
 926                                 Console.WriteLine ("Name: " + m.Name);
 927                                 Console.WriteLine ("    : " + ((MethodInfo)m).ReturnType);
 928                         }
 929 #endif
 930
 931                         most_specific_source = FindMostSpecificSource (union, source, look_for_explicit, loc);
 932                         if (most_specific_source == null)
 933                                 return null;
 934
 935                         most_specific_target = FindMostSpecificTarget (union, target, look_for_explicit, loc);
 936                         if (most_specific_target == null)
 937                                 return null;
 938
 939                         int count = 0;
 940
 941
 942                         foreach (MethodBase mb in union.Methods){
 943                                 ParameterData pd = Invocation.GetParameterData (mb);
 944                                 MethodInfo mi = (MethodInfo) mb;
 945
 946                                 if (pd.ParameterType (0) == most_specific_source &&
 947                                     mi.ReturnType == most_specific_target) {
 948                                         method = mb;
 949                                         count++;
 950                                 }
 951                         }
 952
 953                         if (method == null || count > 1)
 954                                 return null;
 955
 956
 957                         //
 958                         // This will do the conversion to the best match that we
 959                         // found.  Now we need to perform an implict standard conversion
 960                         // if the best match was not the type that we were requested
 961                         // by target.
 962                         //
 963                         if (look_for_explicit)
 964                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
 965                         else
 966                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
 967
 968                         if (source == null)
 969                                 return null;
 970
 971                         Expression e;
 972                         e =  new UserCast ((MethodInfo) method, source, loc);
 973                         if (e.Type != target){
 974                                 if (!look_for_explicit)
 975                                         e = ImplicitConversionStandard (ec, e, target, loc);
 976                                 else
 977                                         e = ExplicitConversionStandard (ec, e, target, loc);
 978                         }
 979
 980                         return e;
 981                 }
 982
 983                 /// <summary>
 984                 ///   Converts implicitly the resolved expression `expr' into the
 985                 ///   `target_type'.  It returns a new expression that can be used
 986                 ///   in a context that expects a `target_type'.
 987                 /// </summary>
 988                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
 989                                                           Type target_type, Location loc)
 990                 {
 991                         Type expr_type = expr.Type;
 992                         Expression e;
 993
 994                         if (target_type == null)
 995                                 throw new Exception ("Target type is null");
 996
 997                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
 998                         if (e != null)
 999                                 return e;
1000
1001                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1002                         if (e != null)
1003                                 return e;
1004
1005                         return null;
1006                 }
1007
1008
1009                 /// <summary>
1010                 ///   Attempts to apply the `Standard Implicit
1011                 ///   Conversion' rules to the expression `expr' into
1012                 ///   the `target_type'.  It returns a new expression
1013                 ///   that can be used in a context that expects a
1014                 ///   `target_type'.
1015                 ///
1016                 ///   This is different from `ImplicitConversion' in that the
1017                 ///   user defined implicit conversions are excluded.
1018                 /// </summary>
1019                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1020                                                                   Type target_type, Location loc)
1021                 {
1022                         Type expr_type = expr.Type;
1023                         Expression e;
1024
1025                         if (expr_type == target_type && !(expr is NullLiteral))
1026                                 return expr;
1027
1028                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1029                         if (e != null)
1030                                 return e;
1031
1032                         e = ImplicitReferenceConversion (expr, target_type);
1033                         if (e != null)
1034                                 return e;
1035
1036                         if ((target_type == TypeManager.enum_type ||
1037                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1038                             expr is IntLiteral){
1039                                 IntLiteral i = (IntLiteral) expr;
1040
1041                                 if (i.Value == 0)
1042                                         return new EnumConstant ((Constant) expr, target_type);
1043                         }
1044
1045                         if (ec.InUnsafe) {
1046                                 if (expr_type.IsPointer){
1047                                         if (target_type == TypeManager.void_ptr_type)
1048                                                 return new EmptyCast (expr, target_type);
1049
1050                                         //
1051                                         // yep, comparing pointer types cant be done with
1052                                         // t1 == t2, we have to compare their element types.
1053                                         //
1054                                         if (target_type.IsPointer){
1055                                                 if (target_type.GetElementType() == expr_type.GetElementType())
1056                                                         return expr;
1057                                         }
1058                                 }
1059
1060                                 if (target_type.IsPointer) {
1061                                         if (expr is NullLiteral)
1062                                                 return new EmptyCast (expr, target_type);
1063
1064                                         if (expr_type == TypeManager.void_ptr_type)
1065                                                 return new EmptyCast (expr, target_type);
1066                                 }
1067                         }
1068
1069                         return null;
1070                 }
1071
1072                 /// <summary>
1073                 ///   Attemps to perform an implict constant conversion of the IntConstant
1074                 ///   into a different data type using casts (See Implicit Constant
1075                 ///   Expression Conversions)
1076                 /// </summary>
1077                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1078                 {
1079                         int value = ic.Value;
1080
1081                         if (target_type == TypeManager.sbyte_type){
1082                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1083                                         return new SByteConstant ((sbyte) value);
1084                         } else if (target_type == TypeManager.byte_type){
1085                                 if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
1086                                         return new ByteConstant ((byte) value);
1087                         } else if (target_type == TypeManager.short_type){
1088                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1089                                         return new ShortConstant ((short) value);
1090                         } else if (target_type == TypeManager.ushort_type){
1091                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1092                                         return new UShortConstant ((ushort) value);
1093                         } else if (target_type == TypeManager.uint32_type){
1094                                 if (value >= 0)
1095                                         return new UIntConstant ((uint) value);
1096                         } else if (target_type == TypeManager.uint64_type){
1097                                 //
1098                                 // we can optimize this case: a positive int32
1099                                 // always fits on a uint64.  But we need an opcode
1100                                 // to do it.
1101                                 //
1102                                 if (value >= 0)
1103                                         return new ULongConstant ((ulong) value);
1104                         } else if (target_type == TypeManager.double_type)
1105                                 return new DoubleConstant ((double) value);
1106                         else if (target_type == TypeManager.float_type)
1107                                 return new FloatConstant ((float) value);
1108
1109                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1110                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1111                                 Constant e = (Constant) ic;
1112
1113                                 //
1114                                 // Possibly, we need to create a different 0 literal before passing
1115                                 // to EnumConstant
1116                                 //n
1117                                 if (underlying == TypeManager.int64_type)
1118                                         e = new LongLiteral (0);
1119                                 else if (underlying == TypeManager.uint64_type)
1120                                         e = new ULongLiteral (0);
1121
1122                                 return new EnumConstant (e, target_type);
1123                         }
1124                         return null;
1125                 }
1126
1127                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1128                 {
1129                         string msg = "Cannot convert implicitly from `"+
1130                                 TypeManager.CSharpName (source) + "' to `" +
1131                                 TypeManager.CSharpName (target) + "'";
1132
1133                         Report.Error (29, loc, msg);
1134                 }
1135
1136                 /// <summary>
1137                 ///   Attemptes to implicityly convert `target' into `type', using
1138                 ///   ImplicitConversion.  If there is no implicit conversion, then
1139                 ///   an error is signaled
1140                 /// </summary>
1141                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1142                                                                   Type target_type, Location loc)
1143                 {
1144                         Expression e;
1145
1146                         e = ImplicitConversion (ec, source, target_type, loc);
1147                         if (e != null)
1148                                 return e;
1149
1150                         if (source is DoubleLiteral && target_type == TypeManager.float_type){
1151                                 Report.Error (664, loc,
1152                                               "Double literal cannot be implicitly converted to " +
1153                                               "float type, use F suffix to create a float literal");
1154                         }
1155
1156                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1157
1158                         return null;
1159                 }
1160
1161                 /// <summary>
1162                 ///   Performs the explicit numeric conversions
1163                 /// </summary>
1164                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1165                 {
1166                         Type expr_type = expr.Type;
1167
1168                         //
1169                         // If we have an enumeration, extract the underlying type,
1170                         // use this during the comparison, but wrap around the original
1171                         // target_type
1172                         //
1173                         Type real_target_type = target_type;
1174
1175                         if (TypeManager.IsEnumType (real_target_type))
1176                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1177
1178                         if (ImplicitStandardConversionExists (expr, real_target_type)){
1179                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1180
1181                                 if (real_target_type != target_type)
1182                                         return new EmptyCast (ce, target_type);
1183                                 return ce;
1184                         }
1185
1186                         if (expr_type == TypeManager.sbyte_type){
1187                                 //
1188                                 // From sbyte to byte, ushort, uint, ulong, char
1189                                 //
1190                                 if (real_target_type == TypeManager.byte_type)
1191                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1192                                 if (real_target_type == TypeManager.ushort_type)
1193                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1194                                 if (real_target_type == TypeManager.uint32_type)
1195                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1196                                 if (real_target_type == TypeManager.uint64_type)
1197                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1198                                 if (real_target_type == TypeManager.char_type)
1199                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1200                         } else if (expr_type == TypeManager.byte_type){
1201                                 //
1202                                 // From byte to sbyte and char
1203                                 //
1204                                 if (real_target_type == TypeManager.sbyte_type)
1205                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1206                                 if (real_target_type == TypeManager.char_type)
1207                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1208                         } else if (expr_type == TypeManager.short_type){
1209                                 //
1210                                 // From short to sbyte, byte, ushort, uint, ulong, char
1211                                 //
1212                                 if (real_target_type == TypeManager.sbyte_type)
1213                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1214                                 if (real_target_type == TypeManager.byte_type)
1215                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1216                                 if (real_target_type == TypeManager.ushort_type)
1217                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1218                                 if (real_target_type == TypeManager.uint32_type)
1219                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1220                                 if (real_target_type == TypeManager.uint64_type)
1221                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1222                                 if (real_target_type == TypeManager.char_type)
1223                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1224                         } else if (expr_type == TypeManager.ushort_type){
1225                                 //
1226                                 // From ushort to sbyte, byte, short, char
1227                                 //
1228                                 if (real_target_type == TypeManager.sbyte_type)
1229                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1230                                 if (real_target_type == TypeManager.byte_type)
1231                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1232                                 if (real_target_type == TypeManager.short_type)
1233                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1234                                 if (real_target_type == TypeManager.char_type)
1235                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1236                         } else if (expr_type == TypeManager.int32_type){
1237                                 //
1238                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1239                                 //
1240                                 if (real_target_type == TypeManager.sbyte_type)
1241                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1242                                 if (real_target_type == TypeManager.byte_type)
1243                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1244                                 if (real_target_type == TypeManager.short_type)
1245                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1246                                 if (real_target_type == TypeManager.ushort_type)
1247                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1248                                 if (real_target_type == TypeManager.uint32_type)
1249                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1250                                 if (real_target_type == TypeManager.uint64_type)
1251                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1252                                 if (real_target_type == TypeManager.char_type)
1253                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1254                         } else if (expr_type == TypeManager.uint32_type){
1255                                 //
1256                                 // From uint to sbyte, byte, short, ushort, int, char
1257                                 //
1258                                 if (real_target_type == TypeManager.sbyte_type)
1259                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1260                                 if (real_target_type == TypeManager.byte_type)
1261                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1262                                 if (real_target_type == TypeManager.short_type)
1263                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1264                                 if (real_target_type == TypeManager.ushort_type)
1265                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1266                                 if (real_target_type == TypeManager.int32_type)
1267                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1268                                 if (real_target_type == TypeManager.char_type)
1269                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1270                         } else if (expr_type == TypeManager.int64_type){
1271                                 //
1272                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1273                                 //
1274                                 if (real_target_type == TypeManager.sbyte_type)
1275                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1276                                 if (real_target_type == TypeManager.byte_type)
1277                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1278                                 if (real_target_type == TypeManager.short_type)
1279                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1280                                 if (real_target_type == TypeManager.ushort_type)
1281                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1282                                 if (real_target_type == TypeManager.int32_type)
1283                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1284                                 if (real_target_type == TypeManager.uint32_type)
1285                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1286                                 if (real_target_type == TypeManager.uint64_type)
1287                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1288                                 if (real_target_type == TypeManager.char_type)
1289                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1290                         } else if (expr_type == TypeManager.uint64_type){
1291                                 //
1292                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1293                                 //
1294                                 if (real_target_type == TypeManager.sbyte_type)
1295                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1296                                 if (real_target_type == TypeManager.byte_type)
1297                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1298                                 if (real_target_type == TypeManager.short_type)
1299                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1300                                 if (real_target_type == TypeManager.ushort_type)
1301                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1302                                 if (real_target_type == TypeManager.int32_type)
1303                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1304                                 if (real_target_type == TypeManager.uint32_type)
1305                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1306                                 if (real_target_type == TypeManager.int64_type)
1307                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1308                                 if (real_target_type == TypeManager.char_type)
1309                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1310                         } else if (expr_type == TypeManager.char_type){
1311                                 //
1312                                 // From char to sbyte, byte, short
1313                                 //
1314                                 if (real_target_type == TypeManager.sbyte_type)
1315                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1316                                 if (real_target_type == TypeManager.byte_type)
1317                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1318                                 if (real_target_type == TypeManager.short_type)
1319                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1320                         } else if (expr_type == TypeManager.float_type){
1321                                 //
1322                                 // From float to sbyte, byte, short,
1323                                 // ushort, int, uint, long, ulong, char
1324                                 // or decimal
1325                                 //
1326                                 if (real_target_type == TypeManager.sbyte_type)
1327                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1328                                 if (real_target_type == TypeManager.byte_type)
1329                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1330                                 if (real_target_type == TypeManager.short_type)
1331                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1332                                 if (real_target_type == TypeManager.ushort_type)
1333                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1334                                 if (real_target_type == TypeManager.int32_type)
1335                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1336                                 if (real_target_type == TypeManager.uint32_type)
1337                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1338                                 if (real_target_type == TypeManager.int64_type)
1339                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1340                                 if (real_target_type == TypeManager.uint64_type)
1341                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1342                                 if (real_target_type == TypeManager.char_type)
1343                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1344                         } else if (expr_type == TypeManager.double_type){
1345                                 //
1346                                 // From double to byte, byte, short,
1347                                 // ushort, int, uint, long, ulong,
1348                                 // char, float or decimal
1349                                 //
1350                                 if (real_target_type == TypeManager.sbyte_type)
1351                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1352                                 if (real_target_type == TypeManager.byte_type)
1353                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1354                                 if (real_target_type == TypeManager.short_type)
1355                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1356                                 if (real_target_type == TypeManager.ushort_type)
1357                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1358                                 if (real_target_type == TypeManager.int32_type)
1359                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1360                                 if (real_target_type == TypeManager.uint32_type)
1361                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1362                                 if (real_target_type == TypeManager.int64_type)
1363                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1364                                 if (real_target_type == TypeManager.uint64_type)
1365                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1366                                 if (real_target_type == TypeManager.char_type)
1367                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1368                                 if (real_target_type == TypeManager.float_type)
1369                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1370                         }
1371
1372                         // decimal is taken care of by the op_Explicit methods.
1373
1374                         return null;
1375                 }
1376
1377                 /// <summary>
1378                 ///  Returns whether an explicit reference conversion can be performed
1379                 ///  from source_type to target_type
1380                 /// </summary>
1381                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1382                 {
1383                         bool target_is_value_type = target_type.IsValueType;
1384
1385                         if (source_type == target_type)
1386                                 return true;
1387
1388                         //
1389                         // From object to any reference type
1390                         //
1391                         if (source_type == TypeManager.object_type && !target_is_value_type)
1392                                 return true;
1393
1394                         //
1395                         // From any class S to any class-type T, provided S is a base class of T
1396                         //
1397                         if (target_type.IsSubclassOf (source_type))
1398                                 return true;
1399
1400                         //
1401                         // From any interface type S to any interface T provided S is not derived from T
1402                         //
1403                         if (source_type.IsInterface && target_type.IsInterface){
1404                                 if (!target_type.IsSubclassOf (source_type))
1405                                         return true;
1406                         }
1407
1408                         //
1409                         // From any class type S to any interface T, provided S is not sealed
1410                         // and provided S does not implement T.
1411                         //
1412                         if (target_type.IsInterface && !source_type.IsSealed &&
1413                             !TypeManager.ImplementsInterface (source_type, target_type))
1414                                 return true;
1415
1416                         //
1417                         // From any interface-type S to to any class type T, provided T is not
1418                         // sealed, or provided T implements S.
1419                         //
1420                         if (source_type.IsInterface &&
1421                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1422                                 return true;
1423
1424
1425                         // From an array type S with an element type Se to an array type T with an
1426                         // element type Te provided all the following are true:
1427                         //     * S and T differe only in element type, in other words, S and T
1428                         //       have the same number of dimensions.
1429                         //     * Both Se and Te are reference types
1430                         //     * An explicit referenc conversions exist from Se to Te
1431                         //
1432                         if (source_type.IsArray && target_type.IsArray) {
1433                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1434
1435                                         Type source_element_type = source_type.GetElementType ();
1436                                         Type target_element_type = target_type.GetElementType ();
1437
1438                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1439                                                 if (ExplicitReferenceConversionExists (source_element_type,
1440                                                                                        target_element_type))
1441                                                         return true;
1442                                 }
1443                         }
1444
1445
1446                         // From System.Array to any array-type
1447                         if (source_type == TypeManager.array_type &&
1448                             target_type.IsArray){
1449                                 return true;
1450                         }
1451
1452                         //
1453                         // From System delegate to any delegate-type
1454                         //
1455                         if (source_type == TypeManager.delegate_type &&
1456                             target_type.IsSubclassOf (TypeManager.delegate_type))
1457                                 return true;
1458
1459                         //
1460                         // From ICloneable to Array or Delegate types
1461                         //
1462                         if (source_type == TypeManager.icloneable_type &&
1463                             (target_type == TypeManager.array_type ||
1464                              target_type == TypeManager.delegate_type))
1465                                 return true;
1466
1467                         return false;
1468                 }
1469
1470                 /// <summary>
1471                 ///   Implements Explicit Reference conversions
1472                 /// </summary>
1473                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1474                 {
1475                         Type source_type = source.Type;
1476                         bool target_is_value_type = target_type.IsValueType;
1477
1478                         //
1479                         // From object to any reference type
1480                         //
1481                         if (source_type == TypeManager.object_type && !target_is_value_type)
1482                                 return new ClassCast (source, target_type);
1483
1484
1485                         //
1486                         // From any class S to any class-type T, provided S is a base class of T
1487                         //
1488                         if (target_type.IsSubclassOf (source_type))
1489                                 return new ClassCast (source, target_type);
1490
1491                         //
1492                         // From any interface type S to any interface T provided S is not derived from T
1493                         //
1494                         if (source_type.IsInterface && target_type.IsInterface){
1495                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1496                                         return null;
1497                                 else
1498                                         return new ClassCast (source, target_type);
1499                         }
1500
1501                         //
1502                         // From any class type S to any interface T, provides S is not sealed
1503                         // and provided S does not implement T.
1504                         //
1505                         if (target_type.IsInterface && !source_type.IsSealed) {
1506                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1507                                         return null;
1508                                 else
1509                                         return new ClassCast (source, target_type);
1510
1511                         }
1512
1513                         //
1514                         // From any interface-type S to to any class type T, provided T is not
1515                         // sealed, or provided T implements S.
1516                         //
1517                         if (source_type.IsInterface) {
1518                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type))
1519                                         return new ClassCast (source, target_type);
1520                                 else
1521                                         return null;
1522                         }
1523
1524                         // From an array type S with an element type Se to an array type T with an
1525                         // element type Te provided all the following are true:
1526                         //     * S and T differe only in element type, in other words, S and T
1527                         //       have the same number of dimensions.
1528                         //     * Both Se and Te are reference types
1529                         //     * An explicit referenc conversions exist from Se to Te
1530                         //
1531                         if (source_type.IsArray && target_type.IsArray) {
1532                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1533
1534                                         Type source_element_type = source_type.GetElementType ();
1535                                         Type target_element_type = target_type.GetElementType ();
1536
1537                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1538                                                 if (ExplicitReferenceConversionExists (source_element_type,
1539                                                                                        target_element_type))
1540                                                         return new ClassCast (source, target_type);
1541                                 }
1542                         }
1543
1544
1545                         // From System.Array to any array-type
1546                         if (source_type == TypeManager.array_type &&
1547                             target_type.IsArray) {
1548                                 return new ClassCast (source, target_type);
1549                         }
1550
1551                         //
1552                         // From System delegate to any delegate-type
1553                         //
1554                         if (source_type == TypeManager.delegate_type &&
1555                             target_type.IsSubclassOf (TypeManager.delegate_type))
1556                                 return new ClassCast (source, target_type);
1557
1558                         //
1559                         // From ICloneable to Array or Delegate types
1560                         //
1561                         if (source_type == TypeManager.icloneable_type &&
1562                             (target_type == TypeManager.array_type ||
1563                              target_type == TypeManager.delegate_type))
1564                                 return new ClassCast (source, target_type);
1565
1566                         return null;
1567                 }
1568
1569                 /// <summary>
1570                 ///   Performs an explicit conversion of the expression `expr' whose
1571                 ///   type is expr.Type to `target_type'.
1572                 /// </summary>
1573                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1574                                                           Type target_type, Location loc)
1575                 {
1576                         Type expr_type = expr.Type;
1577                         Type original_expr_type = expr_type;
1578
1579                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1580                                 if (target_type == TypeManager.enum_type ||
1581                                     target_type == TypeManager.object_type) {
1582                                         if (expr is EnumConstant)
1583                                                 expr = ((EnumConstant) expr).Child;
1584                                         // We really need all these casts here .... :-(
1585                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1586                                         return new EmptyCast (expr, target_type);
1587                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1588                                            target_type.IsSubclassOf (TypeManager.enum_type))
1589                                         return new UnboxCast (expr, target_type);
1590
1591                                 //
1592                                 // Notice that we have kept the expr_type unmodified, which is only
1593                                 // used later on to
1594                                 if (expr is EnumConstant)
1595                                         expr = ((EnumConstant) expr).Child;
1596                                 else
1597                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1598                                 expr_type = expr.Type;
1599                         }
1600
1601                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1602
1603                         if (ne != null)
1604                                 return ne;
1605
1606                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1607                         if (ne != null)
1608                                 return ne;
1609
1610                         //
1611                         // Unboxing conversion.
1612                         //
1613                         if (expr_type == TypeManager.object_type && target_type.IsValueType){
1614                                 if (expr is NullLiteral){
1615                                         Report.Error (37, "Cannot convert null to value type `" +
1616                                                       TypeManager.CSharpName (expr_type) + "'");
1617                                         return null;
1618                                 }
1619                                 return new UnboxCast (expr, target_type);
1620                         }
1621
1622
1623                         ne = ExplicitReferenceConversion (expr, target_type);
1624                         if (ne != null)
1625                                 return ne;
1626
1627                         if (ec.InUnsafe){
1628                                 if (target_type.IsPointer){
1629                                         if (expr_type.IsPointer)
1630                                                 return new EmptyCast (expr, target_type);
1631
1632                                         if (expr_type == TypeManager.sbyte_type ||
1633                                             expr_type == TypeManager.byte_type ||
1634                                             expr_type == TypeManager.short_type ||
1635                                             expr_type == TypeManager.ushort_type ||
1636                                             expr_type == TypeManager.int32_type ||
1637                                             expr_type == TypeManager.uint32_type ||
1638                                             expr_type == TypeManager.uint64_type ||
1639                                             expr_type == TypeManager.int64_type)
1640                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1641                                 }
1642                                 if (expr_type.IsPointer){
1643                                         if (target_type == TypeManager.sbyte_type ||
1644                                             target_type == TypeManager.byte_type ||
1645                                             target_type == TypeManager.short_type ||
1646                                             target_type == TypeManager.ushort_type ||
1647                                             target_type == TypeManager.int32_type ||
1648                                             target_type == TypeManager.uint32_type ||
1649                                             target_type == TypeManager.uint64_type ||
1650                                             target_type == TypeManager.int64_type){
1651                                                 Expression e = new EmptyCast (expr, TypeManager.uint32_type);
1652                                                 Expression ci, ce;
1653
1654                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1655
1656                                                 if (ci != null)
1657                                                         return ci;
1658
1659                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1660                                                 if (ce != null)
1661                                                         return ce;
1662                                                 //
1663                                                 // We should always be able to go from an uint32
1664                                                 // implicitly or explicitly to the other integral
1665                                                 // types
1666                                                 //
1667                                                 throw new Exception ("Internal compiler error");
1668                                         }
1669                                 }
1670                         }
1671
1672                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1673                         if (ne != null)
1674                                 return ne;
1675
1676                         Error_CannotConvertType (loc, original_expr_type, target_type);
1677                         return null;
1678                 }
1679
1680                 /// <summary>
1681                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1682                 /// </summary>
1683                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1684                                                                   Type target_type, Location l)
1685                 {
1686                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1687
1688                         if (ne != null)
1689                                 return ne;
1690
1691                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1692                         if (ne != null)
1693                                 return ne;
1694
1695                         ne = ExplicitReferenceConversion (expr, target_type);
1696                         if (ne != null)
1697                                 return ne;
1698
1699                         Error_CannotConvertType (l, expr.Type, target_type);
1700                         return null;
1701                 }
1702         }
1703 }