mcs/mcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 //
  23                 // This is used to prettify the code: a null argument is allowed
  24                 // for ImplicitStandardConversion as long as it is known that
  25                 // no anonymous method will play a role.
  26                 //
  27                 // FIXME: renamed from `const' to `static' to allow bootstraping from older
  28                 // versions of the compiler that could not cope with this construct.
  29                 //
  30                 public static EmitContext ConstantEC = null;
  31
  32                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  33                 {
  34                         Report.Error (30, loc, "Cannot convert type '" +
  35                                       TypeManager.CSharpName (source) + "' to '" +
  36                                       TypeManager.CSharpName (target) + "'");
  37                 }
  38
  39                 static EmptyExpression MyEmptyExpr;
  40                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  41                 {
  42                         Type expr_type = expr.Type;
  43
  44                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  45                                 // if we are a method group, emit a warning
  46
  47                                 expr.Emit (null);
  48                         }
  49
  50                         if (expr_type == TypeManager.void_type)
  51                                 return null;
  52
  53                         //
  54                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  55                         // is an abstract class, and not really a value type, so we apply the same rules.
  56                         //
  57                         if (target_type == TypeManager.object_type) {
  58                                 //
  59                                 // A pointer type cannot be converted to object
  60                                 //
  61                                 if (expr_type.IsPointer)
  62                                         return null;
  63
  64                                 if (expr_type.IsValueType)
  65                                         return new BoxedCast (expr);
  66                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
  67                                         if (expr_type == TypeManager.anonymous_method_type)
  68                                                 return null;
  69                                         return new EmptyCast (expr, target_type);
  70                                 }
  71
  72                                 return null;
  73                         } else if (target_type == TypeManager.value_type) {
  74                                 if (expr_type.IsValueType)
  75                                         return new BoxedCast (expr);
  76                                 if (expr_type == TypeManager.null_type)
  77                                         return new NullCast (expr, target_type);
  78
  79                                 return null;
  80                         } else if (expr_type.IsSubclassOf (target_type)) {
  81                                 //
  82                                 // Special case: enumeration to System.Enum.
  83                                 // System.Enum is not a value type, it is a class, so we need
  84                                 // a boxing conversion
  85                                 //
  86                                 if (expr_type.IsEnum)
  87                                         return new BoxedCast (expr);
  88
  89                                 return new EmptyCast (expr, target_type);
  90                         }
  91
  92                         // This code is kind of mirrored inside ImplicitStandardConversionExists
  93                         // with the small distinction that we only probe there
  94                         //
  95                         // Always ensure that the code here and there is in sync
  96
  97                         // from the null type to any reference-type.
  98                         if (expr_type == TypeManager.null_type){
  99                                 if (target_type.IsPointer)
 100                                         return new EmptyCast (expr, target_type);
 101
 102                                 if (!target_type.IsValueType)
 103                                         return new NullCast (expr, target_type);
 104                         }
 105
 106                         // from any class-type S to any interface-type T.
 107                         if (target_type.IsInterface) {
 108                                 if (target_type != TypeManager.iconvertible_type &&
 109                                     expr_type.IsValueType && (expr is Constant) &&
 110                                     !(expr is IntLiteral || expr is BoolLiteral ||
 111                                       expr is FloatLiteral || expr is DoubleLiteral ||
 112                                       expr is LongLiteral || expr is CharLiteral ||
 113                                       expr is StringLiteral || expr is DecimalLiteral ||
 114                                       expr is UIntLiteral || expr is ULongLiteral)) {
 115                                         return null;
 116                                 }
 117
 118                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 119                                         if (expr_type.IsClass)
 120                                                 return new EmptyCast (expr, target_type);
 121                                         else if (expr_type.IsValueType)
 122                                                 return new BoxedCast (expr, target_type);
 123                                         else
 124                                                 return new EmptyCast (expr, target_type);
 125                                 }
 126                         }
 127
 128                         // from any interface type S to interface-type T.
 129                         if (expr_type.IsInterface && target_type.IsInterface) {
 130                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 131                                         return new EmptyCast (expr, target_type);
 132                                 else
 133                                         return null;
 134                         }
 135
 136                         // from an array-type S to an array-type of type T
 137                         if (expr_type.IsArray && target_type.IsArray) {
 138                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 139
 140                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 141
 142                                         if (MyEmptyExpr == null)
 143                                                 MyEmptyExpr = new EmptyExpression ();
 144
 145                                         MyEmptyExpr.SetType (expr_element_type);
 146                                         Type target_element_type = TypeManager.GetElementType (target_type);
 147
 148                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 149                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 150                                                                                       target_element_type))
 151                                                         return new EmptyCast (expr, target_type);
 152                                 }
 153                         }
 154
 155                         // from an array-type to System.Array
 156                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 157                                 return new EmptyCast (expr, target_type);
 158
 159                         // from any delegate type to System.Delegate
 160                         if ((expr_type == TypeManager.delegate_type ||
 161                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 162                             target_type == TypeManager.delegate_type)
 163                                 return new EmptyCast (expr, target_type);
 164
 165                         // from any array-type or delegate type into System.ICloneable.
 166                         if (expr_type.IsArray ||
 167                             expr_type == TypeManager.delegate_type ||
 168                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 169                                 if (target_type == TypeManager.icloneable_type)
 170                                         return new EmptyCast (expr, target_type);
 171
 172                         return null;
 173                 }
 174
 175                 //
 176                 // Tests whether an implicit reference conversion exists between expr_type
 177                 // and target_type
 178                 //
 179                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 180                 {
 181                         Type expr_type = expr.Type;
 182
 183                         //
 184                         // This is the boxed case.
 185                         //
 186                         if (target_type == TypeManager.object_type) {
 187                                 if (expr_type.IsClass || expr_type.IsValueType ||
 188                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 189                                         if (target_type != TypeManager.anonymous_method_type)
 190                                                 return true;
 191
 192                                 return false;
 193                         } else if (expr_type.IsSubclassOf (target_type))
 194                                 return true;
 195
 196                         // Please remember that all code below actually comes
 197                         // from ImplicitReferenceConversion so make sure code remains in sync
 198
 199                         // from any class-type S to any interface-type T.
 200                         if (target_type.IsInterface) {
 201                                 if (target_type != TypeManager.iconvertible_type &&
 202                                     expr_type.IsValueType && (expr is Constant) &&
 203                                     !(expr is IntLiteral || expr is BoolLiteral ||
 204                                       expr is FloatLiteral || expr is DoubleLiteral ||
 205                                       expr is LongLiteral || expr is CharLiteral ||
 206                                       expr is StringLiteral || expr is DecimalLiteral ||
 207                                       expr is UIntLiteral || expr is ULongLiteral)) {
 208                                         return false;
 209                                 }
 210
 211                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 212                                         return true;
 213                         }
 214
 215                         // from any interface type S to interface-type T.
 216                         if (expr_type.IsInterface && target_type.IsInterface)
 217                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 218                                         return true;
 219
 220                         // from an array-type S to an array-type of type T
 221                         if (expr_type.IsArray && target_type.IsArray) {
 222                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 223
 224                                         Type expr_element_type = expr_type.GetElementType ();
 225
 226                                         if (MyEmptyExpr == null)
 227                                                 MyEmptyExpr = new EmptyExpression ();
 228
 229                                         MyEmptyExpr.SetType (expr_element_type);
 230                                         Type target_element_type = TypeManager.GetElementType (target_type);
 231
 232                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 233                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 234                                                                                       target_element_type))
 235                                                         return true;
 236                                 }
 237                         }
 238
 239                         // from an array-type to System.Array
 240                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 241                                 return true;
 242
 243                         // from any delegate type to System.Delegate
 244                         if ((expr_type == TypeManager.delegate_type ||
 245                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 246                             target_type == TypeManager.delegate_type)
 247                                 if (target_type.IsAssignableFrom (expr_type))
 248                                         return true;
 249
 250                         // from any array-type or delegate type into System.ICloneable.
 251                         if (expr_type.IsArray ||
 252                             expr_type == TypeManager.delegate_type ||
 253                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 254                                 if (target_type == TypeManager.icloneable_type)
 255                                         return true;
 256
 257                         // from the null type to any reference-type.
 258                         if (expr_type == TypeManager.null_type){
 259                                 if (target_type.IsPointer)
 260                                         return true;
 261
 262                                 if (!target_type.IsValueType)
 263                                         return true;
 264                         }
 265                         return false;
 266                 }
 267
 268                 /// <summary>
 269                 ///   Implicit Numeric Conversions.
 270                 ///
 271                 ///   expr is the expression to convert, returns a new expression of type
 272                 ///   target_type or null if an implicit conversion is not possible.
 273                 /// </summary>
 274                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 275                                                                     Type target_type, Location loc)
 276                 {
 277                         Type expr_type = expr.Type;
 278
 279                         //
 280                         // Attempt to do the implicit constant expression conversions
 281
 282                         if (expr is Constant){
 283                                 if (expr is IntConstant){
 284                                         Expression e;
 285
 286                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 287
 288                                         if (e != null)
 289                                                 return e;
 290                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 291                                         //
 292                                         // Try the implicit constant expression conversion
 293                                         // from long to ulong, instead of a nice routine,
 294                                         // we just inline it
 295                                         //
 296                                         long v = ((LongConstant) expr).Value;
 297                                         if (v >= 0)
 298                                                 return new ULongConstant ((ulong) v);
 299                                 }
 300                         }
 301
 302                         Type real_target_type = target_type;
 303
 304                         if (expr_type == TypeManager.sbyte_type){
 305                                 //
 306                                 // From sbyte to short, int, long, float, double.
 307                                 //
 308                                 if (real_target_type == TypeManager.int32_type)
 309                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 310                                 if (real_target_type == TypeManager.int64_type)
 311                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 312                                 if (real_target_type == TypeManager.double_type)
 313                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 314                                 if (real_target_type == TypeManager.float_type)
 315                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 316                                 if (real_target_type == TypeManager.short_type)
 317                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 318                         } else if (expr_type == TypeManager.byte_type){
 319                                 //
 320                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 321                                 //
 322                                 if ((real_target_type == TypeManager.short_type) ||
 323                                     (real_target_type == TypeManager.ushort_type) ||
 324                                     (real_target_type == TypeManager.int32_type) ||
 325                                     (real_target_type == TypeManager.uint32_type))
 326                                         return new EmptyCast (expr, target_type);
 327
 328                                 if (real_target_type == TypeManager.uint64_type)
 329                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 330                                 if (real_target_type == TypeManager.int64_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 332                                 if (real_target_type == TypeManager.float_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 334                                 if (real_target_type == TypeManager.double_type)
 335                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 336                         } else if (expr_type == TypeManager.short_type){
 337                                 //
 338                                 // From short to int, long, float, double
 339                                 //
 340                                 if (real_target_type == TypeManager.int32_type)
 341                                         return new EmptyCast (expr, target_type);
 342                                 if (real_target_type == TypeManager.int64_type)
 343                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 344                                 if (real_target_type == TypeManager.double_type)
 345                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 346                                 if (real_target_type == TypeManager.float_type)
 347                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 348                         } else if (expr_type == TypeManager.ushort_type){
 349                                 //
 350                                 // From ushort to int, uint, long, ulong, float, double
 351                                 //
 352                                 if (real_target_type == TypeManager.uint32_type)
 353                                         return new EmptyCast (expr, target_type);
 354
 355                                 if (real_target_type == TypeManager.uint64_type)
 356                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 357                                 if (real_target_type == TypeManager.int32_type)
 358                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 359                                 if (real_target_type == TypeManager.int64_type)
 360                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 361                                 if (real_target_type == TypeManager.double_type)
 362                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 363                                 if (real_target_type == TypeManager.float_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 365                         } else if (expr_type == TypeManager.int32_type){
 366                                 //
 367                                 // From int to long, float, double
 368                                 //
 369                                 if (real_target_type == TypeManager.int64_type)
 370                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 371                                 if (real_target_type == TypeManager.double_type)
 372                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 373                                 if (real_target_type == TypeManager.float_type)
 374                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 375                         } else if (expr_type == TypeManager.uint32_type){
 376                                 //
 377                                 // From uint to long, ulong, float, double
 378                                 //
 379                                 if (real_target_type == TypeManager.int64_type)
 380                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 381                                 if (real_target_type == TypeManager.uint64_type)
 382                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 383                                 if (real_target_type == TypeManager.double_type)
 384                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 385                                                                OpCodes.Conv_R8);
 386                                 if (real_target_type == TypeManager.float_type)
 387                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 388                                                                OpCodes.Conv_R4);
 389                         } else if (expr_type == TypeManager.int64_type){
 390                                 //
 391                                 // From long/ulong to float, double
 392                                 //
 393                                 if (real_target_type == TypeManager.double_type)
 394                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 395                                 if (real_target_type == TypeManager.float_type)
 396                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 397                         } else if (expr_type == TypeManager.uint64_type){
 398                                 //
 399                                 // From ulong to float, double
 400                                 //
 401                                 if (real_target_type == TypeManager.double_type)
 402                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 403                                                                OpCodes.Conv_R8);
 404                                 if (real_target_type == TypeManager.float_type)
 405                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 406                                                                OpCodes.Conv_R4);
 407                         } else if (expr_type == TypeManager.char_type){
 408                                 //
 409                                 // From char to ushort, int, uint, long, ulong, float, double
 410                                 //
 411                                 if ((real_target_type == TypeManager.ushort_type) ||
 412                                     (real_target_type == TypeManager.int32_type) ||
 413                                     (real_target_type == TypeManager.uint32_type))
 414                                         return new EmptyCast (expr, target_type);
 415                                 if (real_target_type == TypeManager.uint64_type)
 416                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 417                                 if (real_target_type == TypeManager.int64_type)
 418                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 419                                 if (real_target_type == TypeManager.float_type)
 420                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 421                                 if (real_target_type == TypeManager.double_type)
 422                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 423                         } else if (expr_type == TypeManager.float_type){
 424                                 //
 425                                 // float to double
 426                                 //
 427                                 if (real_target_type == TypeManager.double_type)
 428                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 429                         }
 430
 431                         return null;
 432                 }
 433
 434
 435                 /// <summary>
 436                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 437                 ///  implicit user defined conversions - needed for overload resolution
 438                 /// </summary>
 439                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 440                 {
 441                         if (ImplicitStandardConversionExists (ec, expr, target_type))
 442                                 return true;
 443
 444                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 445
 446                         if (dummy != null)
 447                                 return true;
 448
 449                         return false;
 450                 }
 451
 452                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 453                 {
 454                         Expression dummy = ImplicitUserConversion (
 455                                 ec, new EmptyExpression (source), target, Location.Null);
 456                         return dummy != null;
 457                 }
 458
 459                 /// <summary>
 460                 ///  Determines if a standard implicit conversion exists from
 461                 ///  expr_type to target_type
 462                 ///
 463                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 464                 /// </summary>
 465                 public static bool ImplicitStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 466                 {
 467                         Type expr_type = expr.Type;
 468
 469                         if (expr_type == TypeManager.void_type)
 470                                 return false;
 471
 472                         if (expr_type == target_type)
 473                                 return true;
 474
 475                         // First numeric conversions
 476
 477                         if (expr_type == TypeManager.sbyte_type){
 478                                 //
 479                                 // From sbyte to short, int, long, float, double.
 480                                 //
 481                                 if ((target_type == TypeManager.int32_type) ||
 482                                     (target_type == TypeManager.int64_type) ||
 483                                     (target_type == TypeManager.double_type) ||
 484                                     (target_type == TypeManager.float_type)  ||
 485                                     (target_type == TypeManager.short_type) ||
 486                                     (target_type == TypeManager.decimal_type))
 487                                         return true;
 488
 489                         } else if (expr_type == TypeManager.byte_type){
 490                                 //
 491                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 492                                 //
 493                                 if ((target_type == TypeManager.short_type) ||
 494                                     (target_type == TypeManager.ushort_type) ||
 495                                     (target_type == TypeManager.int32_type) ||
 496                                     (target_type == TypeManager.uint32_type) ||
 497                                     (target_type == TypeManager.uint64_type) ||
 498                                     (target_type == TypeManager.int64_type) ||
 499                                     (target_type == TypeManager.float_type) ||
 500                                     (target_type == TypeManager.double_type) ||
 501                                     (target_type == TypeManager.decimal_type))
 502                                         return true;
 503
 504                         } else if (expr_type == TypeManager.short_type){
 505                                 //
 506                                 // From short to int, long, float, double
 507                                 //
 508                                 if ((target_type == TypeManager.int32_type) ||
 509                                     (target_type == TypeManager.int64_type) ||
 510                                     (target_type == TypeManager.double_type) ||
 511                                     (target_type == TypeManager.float_type) ||
 512                                     (target_type == TypeManager.decimal_type))
 513                                         return true;
 514
 515                         } else if (expr_type == TypeManager.ushort_type){
 516                                 //
 517                                 // From ushort to int, uint, long, ulong, float, double
 518                                 //
 519                                 if ((target_type == TypeManager.uint32_type) ||
 520                                     (target_type == TypeManager.uint64_type) ||
 521                                     (target_type == TypeManager.int32_type) ||
 522                                     (target_type == TypeManager.int64_type) ||
 523                                     (target_type == TypeManager.double_type) ||
 524                                     (target_type == TypeManager.float_type) ||
 525                                     (target_type == TypeManager.decimal_type))
 526                                         return true;
 527
 528                         } else if (expr_type == TypeManager.int32_type){
 529                                 //
 530                                 // From int to long, float, double
 531                                 //
 532                                 if ((target_type == TypeManager.int64_type) ||
 533                                     (target_type == TypeManager.double_type) ||
 534                                     (target_type == TypeManager.float_type) ||
 535                                     (target_type == TypeManager.decimal_type))
 536                                         return true;
 537
 538                         } else if (expr_type == TypeManager.uint32_type){
 539                                 //
 540                                 // From uint to long, ulong, float, double
 541                                 //
 542                                 if ((target_type == TypeManager.int64_type) ||
 543                                     (target_type == TypeManager.uint64_type) ||
 544                                     (target_type == TypeManager.double_type) ||
 545                                     (target_type == TypeManager.float_type) ||
 546                                     (target_type == TypeManager.decimal_type))
 547                                         return true;
 548
 549                         } else if ((expr_type == TypeManager.uint64_type) ||
 550                                    (expr_type == TypeManager.int64_type)) {
 551                                 //
 552                                 // From long/ulong to float, double
 553                                 //
 554                                 if ((target_type == TypeManager.double_type) ||
 555                                     (target_type == TypeManager.float_type) ||
 556                                     (target_type == TypeManager.decimal_type))
 557                                         return true;
 558
 559                         } else if (expr_type == TypeManager.char_type){
 560                                 //
 561                                 // From char to ushort, int, uint, long, ulong, float, double
 562                                 //
 563                                 if ((target_type == TypeManager.ushort_type) ||
 564                                     (target_type == TypeManager.int32_type) ||
 565                                     (target_type == TypeManager.uint32_type) ||
 566                                     (target_type == TypeManager.uint64_type) ||
 567                                     (target_type == TypeManager.int64_type) ||
 568                                     (target_type == TypeManager.float_type) ||
 569                                     (target_type == TypeManager.double_type) ||
 570                                     (target_type == TypeManager.decimal_type))
 571                                         return true;
 572
 573                         } else if (expr_type == TypeManager.float_type){
 574                                 //
 575                                 // float to double
 576                                 //
 577                                 if (target_type == TypeManager.double_type)
 578                                         return true;
 579                         }
 580
 581                         if (ImplicitReferenceConversionExists (expr, target_type))
 582                                 return true;
 583
 584                         //
 585                         // Implicit Constant Expression Conversions
 586                         //
 587                         if (expr is IntConstant){
 588                                 int value = ((IntConstant) expr).Value;
 589
 590                                 if (target_type == TypeManager.sbyte_type){
 591                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 592                                                 return true;
 593                                 } else if (target_type == TypeManager.byte_type){
 594                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 595                                                 return true;
 596                                 } else if (target_type == TypeManager.short_type){
 597                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 598                                                 return true;
 599                                 } else if (target_type == TypeManager.ushort_type){
 600                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 601                                                 return true;
 602                                 } else if (target_type == TypeManager.uint32_type){
 603                                         if (value >= 0)
 604                                                 return true;
 605                                 } else if (target_type == TypeManager.uint64_type){
 606                                          //
 607                                          // we can optimize this case: a positive int32
 608                                          // always fits on a uint64.  But we need an opcode
 609                                          // to do it.
 610                                          //
 611                                         if (value >= 0)
 612                                                 return true;
 613                                 }
 614
 615                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 616                                         return true;
 617                         }
 618
 619                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 620                                 //
 621                                 // Try the implicit constant expression conversion
 622                                 // from long to ulong, instead of a nice routine,
 623                                 // we just inline it
 624                                 //
 625                                 long v = ((LongConstant) expr).Value;
 626                                 if (v > 0)
 627                                         return true;
 628                         }
 629
 630                         if ((target_type == TypeManager.enum_type ||
 631                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 632                              expr is IntLiteral){
 633                                 IntLiteral i = (IntLiteral) expr;
 634
 635                                 if (i.Value == 0)
 636                                         return true;
 637                         }
 638
 639                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 640                                 return true;
 641
 642                         if (expr_type == TypeManager.anonymous_method_type){
 643                                 if (!TypeManager.IsDelegateType (target_type))
 644                                         return false;
 645
 646                                 AnonymousMethod am = (AnonymousMethod) expr;
 647                                 int errors = Report.Errors;
 648
 649                                 Expression conv = am.Compatible (ec, target_type, true);
 650                                 if (conv != null)
 651                                         return true;
 652                         }
 653
 654                         return false;
 655                 }
 656
 657                 //
 658                 // Used internally by FindMostEncompassedType, this is used
 659                 // to avoid creating lots of objects in the tight loop inside
 660                 // FindMostEncompassedType
 661                 //
 662                 static EmptyExpression priv_fmet_param;
 663
 664                 /// <summary>
 665                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 666                 ///  amongst the methods in the MethodGroupExpr
 667                 /// </summary>
 668                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 669                 {
 670                         Type best = null;
 671
 672                         if (priv_fmet_param == null)
 673                                 priv_fmet_param = new EmptyExpression ();
 674
 675                         foreach (Type t in types){
 676                                 priv_fmet_param.SetType (t);
 677
 678                                 if (best == null) {
 679                                         best = t;
 680                                         continue;
 681                                 }
 682
 683                                 if (ImplicitStandardConversionExists (ec, priv_fmet_param, best))
 684                                         best = t;
 685                         }
 686
 687                         return best;
 688                 }
 689
 690                 //
 691                 // Used internally by FindMostEncompassingType, this is used
 692                 // to avoid creating lots of objects in the tight loop inside
 693                 // FindMostEncompassingType
 694                 //
 695                 static EmptyExpression priv_fmee_ret;
 696
 697                 /// <summary>
 698                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 699                 ///  amongst the types in the given set
 700                 /// </summary>
 701                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 702                 {
 703                         Type best = null;
 704
 705                         if (priv_fmee_ret == null)
 706                                 priv_fmee_ret = new EmptyExpression ();
 707
 708                         foreach (Type t in types){
 709                                 priv_fmee_ret.SetType (best);
 710
 711                                 if (best == null) {
 712                                         best = t;
 713                                         continue;
 714                                 }
 715
 716                                 if (ImplicitStandardConversionExists (ec, priv_fmee_ret, t))
 717                                         best = t;
 718                         }
 719
 720                         return best;
 721                 }
 722
 723                 //
 724                 // Used to avoid creating too many objects
 725                 //
 726                 static EmptyExpression priv_fms_expr;
 727
 728                 /// <summary>
 729                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 730                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 731                 ///   for explicit and implicit conversion operators.
 732                 /// </summary>
 733                 static public Type FindMostSpecificSource (EmitContext ec, MethodGroupExpr me,
 734                                                            Expression source, bool apply_explicit_conv_rules,
 735                                                            Location loc)
 736                 {
 737                         ArrayList src_types_set = new ArrayList ();
 738
 739                         if (priv_fms_expr == null)
 740                                 priv_fms_expr = new EmptyExpression ();
 741
 742                         //
 743                         // If any operator converts from S then Sx = S
 744                         //
 745                         Type source_type = source.Type;
 746                         foreach (MethodBase mb in me.Methods){
 747                                 ParameterData pd = Invocation.GetParameterData (mb);
 748                                 Type param_type = pd.ParameterType (0);
 749
 750                                 if (param_type == source_type)
 751                                         return param_type;
 752
 753                                 if (apply_explicit_conv_rules) {
 754                                         //
 755                                         // From the spec :
 756                                         // Find the set of applicable user-defined conversion operators, U.  This set
 757                                         // consists of the
 758                                         // user-defined implicit or explicit conversion operators declared by
 759                                         // the classes or structs in D that convert from a type encompassing
 760                                         // or encompassed by S to a type encompassing or encompassed by T
 761                                         //
 762                                         priv_fms_expr.SetType (param_type);
 763                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, source_type))
 764                                                 src_types_set.Add (param_type);
 765                                         else {
 766                                                 if (ImplicitStandardConversionExists (ec, source, param_type))
 767                                                         src_types_set.Add (param_type);
 768                                         }
 769                                 } else {
 770                                         //
 771                                         // Only if S is encompassed by param_type
 772                                         //
 773                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 774                                                 src_types_set.Add (param_type);
 775                                 }
 776                         }
 777
 778                         //
 779                         // Explicit Conv rules
 780                         //
 781                         if (apply_explicit_conv_rules) {
 782                                 ArrayList candidate_set = new ArrayList ();
 783
 784                                 foreach (Type param_type in src_types_set){
 785                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 786                                                 candidate_set.Add (param_type);
 787                                 }
 788
 789                                 if (candidate_set.Count != 0)
 790                                         return FindMostEncompassedType (ec, candidate_set);
 791                         }
 792
 793                         //
 794                         // Final case
 795                         //
 796                         if (apply_explicit_conv_rules)
 797                                 return FindMostEncompassingType (ec, src_types_set);
 798                         else
 799                                 return FindMostEncompassedType (ec, src_types_set);
 800                 }
 801
 802                 //
 803                 // Useful in avoiding proliferation of objects
 804                 //
 805                 static EmptyExpression priv_fmt_expr;
 806
 807                 /// <summary>
 808                 ///  Finds the most specific target Tx according to section 13.4.4
 809                 /// </summary>
 810                 static public Type FindMostSpecificTarget (EmitContext ec, MethodGroupExpr me,
 811                                                            Type target, bool apply_explicit_conv_rules,
 812                                                            Location loc)
 813                 {
 814                         ArrayList tgt_types_set = new ArrayList ();
 815
 816                         if (priv_fmt_expr == null)
 817                                 priv_fmt_expr = new EmptyExpression ();
 818
 819                         //
 820                         // If any operator converts to T then Tx = T
 821                         //
 822                         foreach (MethodInfo mi in me.Methods){
 823                                 Type ret_type = mi.ReturnType;
 824
 825                                 if (ret_type == target)
 826                                         return ret_type;
 827
 828                                 if (apply_explicit_conv_rules) {
 829                                         //
 830                                         // From the spec :
 831                                         // Find the set of applicable user-defined conversion operators, U.
 832                                         //
 833                                         // This set consists of the
 834                                         // user-defined implicit or explicit conversion operators declared by
 835                                         // the classes or structs in D that convert from a type encompassing
 836                                         // or encompassed by S to a type encompassing or encompassed by T
 837                                         //
 838                                         priv_fms_expr.SetType (ret_type);
 839                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
 840                                                 tgt_types_set.Add (ret_type);
 841                                         else {
 842                                                 priv_fms_expr.SetType (target);
 843                                                 if (ImplicitStandardConversionExists (ec, priv_fms_expr, ret_type))
 844                                                         tgt_types_set.Add (ret_type);
 845                                         }
 846                                 } else {
 847                                         //
 848                                         // Only if T is encompassed by param_type
 849                                         //
 850                                         priv_fms_expr.SetType (ret_type);
 851                                         if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
 852                                                 tgt_types_set.Add (ret_type);
 853                                 }
 854                         }
 855
 856                         //
 857                         // Explicit conv rules
 858                         //
 859                         if (apply_explicit_conv_rules) {
 860                                 ArrayList candidate_set = new ArrayList ();
 861
 862                                 foreach (Type ret_type in tgt_types_set){
 863                                         priv_fmt_expr.SetType (ret_type);
 864
 865                                         if (ImplicitStandardConversionExists (ec, priv_fmt_expr, target))
 866                                                 candidate_set.Add (ret_type);
 867                                 }
 868
 869                                 if (candidate_set.Count != 0)
 870                                         return FindMostEncompassingType (ec, candidate_set);
 871                         }
 872
 873                         //
 874                         // Okay, final case !
 875                         //
 876                         if (apply_explicit_conv_rules)
 877                                 return FindMostEncompassedType (ec, tgt_types_set);
 878                         else
 879                                 return FindMostEncompassingType (ec, tgt_types_set);
 880                 }
 881
 882                 /// <summary>
 883                 ///  User-defined Implicit conversions
 884                 /// </summary>
 885                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 886                                                                  Type target, Location loc)
 887                 {
 888                         return UserDefinedConversion (ec, source, target, loc, false);
 889                 }
 890
 891                 /// <summary>
 892                 ///  User-defined Explicit conversions
 893                 /// </summary>
 894                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 895                                                                  Type target, Location loc)
 896                 {
 897                         return UserDefinedConversion (ec, source, target, loc, true);
 898                 }
 899
 900                 static DoubleHash explicit_conv = new DoubleHash (100);
 901                 static DoubleHash implicit_conv = new DoubleHash (100);
 902                 /// <summary>
 903                 ///   Computes the MethodGroup for the user-defined conversion
 904                 ///   operators from source_type to target_type.  `look_for_explicit'
 905                 ///   controls whether we should also include the list of explicit
 906                 ///   operators
 907                 /// </summary>
 908                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
 909                                                                Type source_type, Type target_type,
 910                                                                Location loc, bool look_for_explicit)
 911                 {
 912                         Expression mg1 = null, mg2 = null;
 913                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
 914                         string op_name;
 915
 916                         op_name = "op_Implicit";
 917
 918                         MethodGroupExpr union3;
 919                         object r;
 920                         if ((look_for_explicit ? explicit_conv : implicit_conv).Lookup (source_type, target_type, out r))
 921                                 return (MethodGroupExpr) r;
 922
 923                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
 924                         if (source_type.BaseType != null)
 925                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 926
 927                         if (mg1 == null)
 928                                 union3 = (MethodGroupExpr) mg2;
 929                         else if (mg2 == null)
 930                                 union3 = (MethodGroupExpr) mg1;
 931                         else
 932                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
 933
 934                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
 935                         if (mg1 != null){
 936                                 if (union3 != null)
 937                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 938                                 else
 939                                         union3 = (MethodGroupExpr) mg1;
 940                         }
 941
 942                         if (target_type.BaseType != null)
 943                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 944
 945                         if (mg1 != null){
 946                                 if (union3 != null)
 947                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
 948                                 else
 949                                         union3 = (MethodGroupExpr) mg1;
 950                         }
 951
 952                         MethodGroupExpr union4 = null;
 953
 954                         if (look_for_explicit) {
 955                                 op_name = "op_Explicit";
 956
 957                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
 958                                 if (source_type.BaseType != null)
 959                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
 960
 961                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
 962                                 if (target_type.BaseType != null)
 963                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
 964
 965                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
 966                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
 967
 968                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
 969                         }
 970
 971                         MethodGroupExpr ret = Invocation.MakeUnionSet (union3, union4, loc);
 972                         (look_for_explicit ? explicit_conv : implicit_conv).Insert (source_type, target_type, ret);
 973                         return ret;
 974                 }
 975
 976                 /// <summary>
 977                 ///   User-defined conversions
 978                 /// </summary>
 979                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 980                                                                 Type target, Location loc,
 981                                                                 bool look_for_explicit)
 982                 {
 983                         MethodGroupExpr union;
 984                         Type source_type = source.Type;
 985                         MethodBase method = null;
 986
 987                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
 988                         if (union == null)
 989                                 return null;
 990
 991                         Type most_specific_source, most_specific_target;
 992
 993                         most_specific_source = FindMostSpecificSource (ec, union, source, look_for_explicit, loc);
 994                         if (most_specific_source == null)
 995                                 return null;
 996
 997                         most_specific_target = FindMostSpecificTarget (ec, union, target, look_for_explicit, loc);
 998                         if (most_specific_target == null)
 999                                 return null;
1000
1001                         int count = 0;
1002
1003
1004                         foreach (MethodBase mb in union.Methods){
1005                                 ParameterData pd = Invocation.GetParameterData (mb);
1006                                 MethodInfo mi = (MethodInfo) mb;
1007
1008                                 if (pd.ParameterType (0) == most_specific_source &&
1009                                     mi.ReturnType == most_specific_target) {
1010                                         method = mb;
1011                                         count++;
1012                                 }
1013                         }
1014
1015                         if (method == null || count > 1)
1016                                 return null;
1017
1018
1019                         //
1020                         // This will do the conversion to the best match that we
1021                         // found.  Now we need to perform an implict standard conversion
1022                         // if the best match was not the type that we were requested
1023                         // by target.
1024                         //
1025                         if (look_for_explicit)
1026                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1027                         else
1028                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1029
1030                         if (source == null)
1031                                 return null;
1032
1033                         Expression e;
1034                         e =  new UserCast ((MethodInfo) method, source, loc);
1035                         if (e.Type != target){
1036                                 if (!look_for_explicit)
1037                                         e = ImplicitConversionStandard (ec, e, target, loc);
1038                                 else
1039                                         e = ExplicitConversionStandard (ec, e, target, loc);
1040                         }
1041
1042                         return e;
1043                 }
1044
1045                 /// <summary>
1046                 ///   Converts implicitly the resolved expression `expr' into the
1047                 ///   `target_type'.  It returns a new expression that can be used
1048                 ///   in a context that expects a `target_type'.
1049                 /// </summary>
1050                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1051                                                              Type target_type, Location loc)
1052                 {
1053                         Expression e;
1054
1055                         if (target_type == null)
1056                                 throw new Exception ("Target type is null");
1057
1058                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1059                         if (e != null)
1060                                 return e;
1061
1062                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1063                         if (e != null)
1064                                 return e;
1065
1066                         return null;
1067                 }
1068
1069
1070                 /// <summary>
1071                 ///   Attempts to apply the `Standard Implicit
1072                 ///   Conversion' rules to the expression `expr' into
1073                 ///   the `target_type'.  It returns a new expression
1074                 ///   that can be used in a context that expects a
1075                 ///   `target_type'.
1076                 ///
1077                 ///   This is different from `ImplicitConversion' in that the
1078                 ///   user defined implicit conversions are excluded.
1079                 /// </summary>
1080                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1081                                                                      Type target_type, Location loc)
1082                 {
1083                         Type expr_type = expr.Type;
1084                         Expression e;
1085
1086                         if (expr.eclass == ExprClass.MethodGroup){
1087                                 if (!TypeManager.IsDelegateType (target_type)){
1088                                         return null;
1089                                 }
1090
1091                                 //
1092                                 // Only allow anonymous method conversions on post ISO_1
1093                                 //
1094                                 if (RootContext.Version != LanguageVersion.ISO_1){
1095                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1096                                         if (mg != null)
1097                                                 return ImplicitDelegateCreation.Create (ec, mg, target_type, loc);
1098                                 }
1099                         }
1100
1101                         if (expr_type == target_type && expr_type != TypeManager.null_type)
1102                                 return expr;
1103
1104                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1105                         if (e != null)
1106                                 return e;
1107
1108                         e = ImplicitReferenceConversion (expr, target_type);
1109                         if (e != null)
1110                                 return e;
1111
1112                         if ((target_type == TypeManager.enum_type ||
1113                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1114                             expr is IntLiteral){
1115                                 IntLiteral i = (IntLiteral) expr;
1116
1117                                 if (i.Value == 0)
1118                                         return new EnumConstant ((Constant) expr, target_type);
1119                         }
1120
1121                         if (ec.InUnsafe) {
1122                                 if (expr_type.IsPointer){
1123                                         if (target_type == TypeManager.void_ptr_type)
1124                                                 return new EmptyCast (expr, target_type);
1125
1126                                         //
1127                                         // yep, comparing pointer types cant be done with
1128                                         // t1 == t2, we have to compare their element types.
1129                                         //
1130                                         if (target_type.IsPointer){
1131                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1132                                                         return expr;
1133                                         }
1134                                 }
1135
1136                                 if (target_type.IsPointer) {
1137                                         if (expr_type == TypeManager.null_type)
1138                                                 return new EmptyCast (expr, target_type);
1139
1140                                         if (expr_type == TypeManager.void_ptr_type)
1141                                                 return new EmptyCast (expr, target_type);
1142                                 }
1143                         }
1144
1145                         if (expr_type == TypeManager.anonymous_method_type){
1146                                 if (!TypeManager.IsDelegateType (target_type)){
1147                                         Report.Error (1660, loc,
1148                                                               "Cannot convert anonymous method to `{0}', since it is not a delegate",
1149                                                               TypeManager.CSharpName (target_type));
1150                                         return null;
1151                                 }
1152
1153                                 AnonymousMethod am = (AnonymousMethod) expr;
1154                                 int errors = Report.Errors;
1155
1156                                 Expression conv = am.Compatible (ec, target_type, false);
1157                                 if (conv != null)
1158                                         return conv;
1159
1160                                 //
1161                                 // We return something instead of null, to avoid
1162                                 // the duplicate error, since am.Compatible would have
1163                                 // reported that already
1164                                 //
1165                                 if (errors != Report.Errors)
1166                                         return new EmptyCast (expr, target_type);
1167                         }
1168
1169                         return null;
1170                 }
1171
1172                 /// <summary>
1173                 ///   Attemps to perform an implict constant conversion of the IntConstant
1174                 ///   into a different data type using casts (See Implicit Constant
1175                 ///   Expression Conversions)
1176                 /// </summary>
1177                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1178                 {
1179                         int value = ic.Value;
1180
1181                         if (target_type == TypeManager.sbyte_type){
1182                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1183                                         return new SByteConstant ((sbyte) value);
1184                         } else if (target_type == TypeManager.byte_type){
1185                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1186                                         return new ByteConstant ((byte) value);
1187                         } else if (target_type == TypeManager.short_type){
1188                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1189                                         return new ShortConstant ((short) value);
1190                         } else if (target_type == TypeManager.ushort_type){
1191                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1192                                         return new UShortConstant ((ushort) value);
1193                         } else if (target_type == TypeManager.uint32_type){
1194                                 if (value >= 0)
1195                                         return new UIntConstant ((uint) value);
1196                         } else if (target_type == TypeManager.uint64_type){
1197                                 //
1198                                 // we can optimize this case: a positive int32
1199                                 // always fits on a uint64.  But we need an opcode
1200                                 // to do it.
1201                                 //
1202                                 if (value >= 0)
1203                                         return new ULongConstant ((ulong) value);
1204                         } else if (target_type == TypeManager.double_type)
1205                                 return new DoubleConstant ((double) value);
1206                         else if (target_type == TypeManager.float_type)
1207                                 return new FloatConstant ((float) value);
1208
1209                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1210                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1211                                 Constant e = (Constant) ic;
1212
1213                                 //
1214                                 // Possibly, we need to create a different 0 literal before passing
1215                                 // to EnumConstant
1216                                 //
1217                                 if (underlying == TypeManager.int64_type)
1218                                         e = new LongLiteral (0);
1219                                 else if (underlying == TypeManager.uint64_type)
1220                                         e = new ULongLiteral (0);
1221
1222                                 return new EnumConstant (e, target_type);
1223                         }
1224                         return null;
1225                 }
1226
1227                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1228                 {
1229                         if (source.Name == target.Name){
1230                                 Report.ExtraInformation (loc,
1231                                          String.Format (
1232                                                 "The type {0} has two conflicting definitons, one comes from {0} and the other from {1}",
1233                                                 source.Assembly.FullName, target.Assembly.FullName));
1234
1235                         }
1236                         Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
1237                                       source == TypeManager.anonymous_method_type ?
1238                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1239                                       TypeManager.CSharpName (target));
1240                 }
1241
1242                 /// <summary>
1243                 ///   Attemptes to implicityly convert `target' into `type', using
1244                 ///   ImplicitConversion.  If there is no implicit conversion, then
1245                 ///   an error is signaled
1246                 /// </summary>
1247                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1248                                                                      Type target_type, Location loc)
1249                 {
1250                         Expression e;
1251
1252                         e = ImplicitConversion (ec, source, target_type, loc);
1253                         if (e != null)
1254                                 return e;
1255
1256                         if (source is DoubleLiteral) {
1257                                 if (target_type == TypeManager.float_type) {
1258                                         Error_664 (loc, "float", "f");
1259                                         return null;
1260                                 }
1261                                 if (target_type == TypeManager.decimal_type) {
1262                                         Error_664 (loc, "decimal", "m");
1263                                         return null;
1264                                 }
1265                         }
1266
1267                         if (source is Constant){
1268                                 Constant c = (Constant) source;
1269
1270                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1271                                 return null;
1272                         }
1273
1274                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1275
1276                         return null;
1277                 }
1278
1279                 static void Error_664 (Location loc, string type, string suffix) {
1280                         Report.Error (664, loc,
1281                                 "Literal of type double cannot be implicitly converted to type '{0}'. Add suffix '{1}' to create a literal of this type",
1282                                 type, suffix);
1283                 }
1284
1285                 /// <summary>
1286                 ///   Performs the explicit numeric conversions
1287                 /// </summary>
1288                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1289                 {
1290                         Type expr_type = expr.Type;
1291
1292                         //
1293                         // If we have an enumeration, extract the underlying type,
1294                         // use this during the comparison, but wrap around the original
1295                         // target_type
1296                         //
1297                         Type real_target_type = target_type;
1298
1299                         if (TypeManager.IsEnumType (real_target_type))
1300                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1301
1302                         if (ImplicitStandardConversionExists (ec, expr, real_target_type)){
1303                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1304
1305                                 if (real_target_type != target_type)
1306                                         return new EmptyCast (ce, target_type);
1307                                 return ce;
1308                         }
1309
1310                         if (expr_type == TypeManager.sbyte_type){
1311                                 //
1312                                 // From sbyte to byte, ushort, uint, ulong, char
1313                                 //
1314                                 if (real_target_type == TypeManager.byte_type)
1315                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1316                                 if (real_target_type == TypeManager.ushort_type)
1317                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1318                                 if (real_target_type == TypeManager.uint32_type)
1319                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1320                                 if (real_target_type == TypeManager.uint64_type)
1321                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1322                                 if (real_target_type == TypeManager.char_type)
1323                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1324                         } else if (expr_type == TypeManager.byte_type){
1325                                 //
1326                                 // From byte to sbyte and char
1327                                 //
1328                                 if (real_target_type == TypeManager.sbyte_type)
1329                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1330                                 if (real_target_type == TypeManager.char_type)
1331                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1332                         } else if (expr_type == TypeManager.short_type){
1333                                 //
1334                                 // From short to sbyte, byte, ushort, uint, ulong, char
1335                                 //
1336                                 if (real_target_type == TypeManager.sbyte_type)
1337                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1338                                 if (real_target_type == TypeManager.byte_type)
1339                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1340                                 if (real_target_type == TypeManager.ushort_type)
1341                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1342                                 if (real_target_type == TypeManager.uint32_type)
1343                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1344                                 if (real_target_type == TypeManager.uint64_type)
1345                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1346                                 if (real_target_type == TypeManager.char_type)
1347                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1348                         } else if (expr_type == TypeManager.ushort_type){
1349                                 //
1350                                 // From ushort to sbyte, byte, short, char
1351                                 //
1352                                 if (real_target_type == TypeManager.sbyte_type)
1353                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1354                                 if (real_target_type == TypeManager.byte_type)
1355                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1356                                 if (real_target_type == TypeManager.short_type)
1357                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1358                                 if (real_target_type == TypeManager.char_type)
1359                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1360                         } else if (expr_type == TypeManager.int32_type){
1361                                 //
1362                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1363                                 //
1364                                 if (real_target_type == TypeManager.sbyte_type)
1365                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1366                                 if (real_target_type == TypeManager.byte_type)
1367                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1368                                 if (real_target_type == TypeManager.short_type)
1369                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1370                                 if (real_target_type == TypeManager.ushort_type)
1371                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1372                                 if (real_target_type == TypeManager.uint32_type)
1373                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1374                                 if (real_target_type == TypeManager.uint64_type)
1375                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1376                                 if (real_target_type == TypeManager.char_type)
1377                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1378                         } else if (expr_type == TypeManager.uint32_type){
1379                                 //
1380                                 // From uint to sbyte, byte, short, ushort, int, char
1381                                 //
1382                                 if (real_target_type == TypeManager.sbyte_type)
1383                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1384                                 if (real_target_type == TypeManager.byte_type)
1385                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1386                                 if (real_target_type == TypeManager.short_type)
1387                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1388                                 if (real_target_type == TypeManager.ushort_type)
1389                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1390                                 if (real_target_type == TypeManager.int32_type)
1391                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1392                                 if (real_target_type == TypeManager.char_type)
1393                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1394                         } else if (expr_type == TypeManager.int64_type){
1395                                 //
1396                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1397                                 //
1398                                 if (real_target_type == TypeManager.sbyte_type)
1399                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1400                                 if (real_target_type == TypeManager.byte_type)
1401                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1402                                 if (real_target_type == TypeManager.short_type)
1403                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1404                                 if (real_target_type == TypeManager.ushort_type)
1405                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1406                                 if (real_target_type == TypeManager.int32_type)
1407                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1408                                 if (real_target_type == TypeManager.uint32_type)
1409                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1410                                 if (real_target_type == TypeManager.uint64_type)
1411                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1412                                 if (real_target_type == TypeManager.char_type)
1413                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1414                         } else if (expr_type == TypeManager.uint64_type){
1415                                 //
1416                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1417                                 //
1418                                 if (real_target_type == TypeManager.sbyte_type)
1419                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1420                                 if (real_target_type == TypeManager.byte_type)
1421                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1422                                 if (real_target_type == TypeManager.short_type)
1423                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1424                                 if (real_target_type == TypeManager.ushort_type)
1425                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1426                                 if (real_target_type == TypeManager.int32_type)
1427                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1428                                 if (real_target_type == TypeManager.uint32_type)
1429                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1430                                 if (real_target_type == TypeManager.int64_type)
1431                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1432                                 if (real_target_type == TypeManager.char_type)
1433                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1434                         } else if (expr_type == TypeManager.char_type){
1435                                 //
1436                                 // From char to sbyte, byte, short
1437                                 //
1438                                 if (real_target_type == TypeManager.sbyte_type)
1439                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1440                                 if (real_target_type == TypeManager.byte_type)
1441                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1442                                 if (real_target_type == TypeManager.short_type)
1443                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1444                         } else if (expr_type == TypeManager.float_type){
1445                                 //
1446                                 // From float to sbyte, byte, short,
1447                                 // ushort, int, uint, long, ulong, char
1448                                 // or decimal
1449                                 //
1450                                 if (real_target_type == TypeManager.sbyte_type)
1451                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1452                                 if (real_target_type == TypeManager.byte_type)
1453                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1454                                 if (real_target_type == TypeManager.short_type)
1455                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1456                                 if (real_target_type == TypeManager.ushort_type)
1457                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1458                                 if (real_target_type == TypeManager.int32_type)
1459                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1460                                 if (real_target_type == TypeManager.uint32_type)
1461                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1462                                 if (real_target_type == TypeManager.int64_type)
1463                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1464                                 if (real_target_type == TypeManager.uint64_type)
1465                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1466                                 if (real_target_type == TypeManager.char_type)
1467                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1468                         } else if (expr_type == TypeManager.double_type){
1469                                 //
1470                                 // From double to byte, byte, short,
1471                                 // ushort, int, uint, long, ulong,
1472                                 // char, float or decimal
1473                                 //
1474                                 if (real_target_type == TypeManager.sbyte_type)
1475                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1476                                 if (real_target_type == TypeManager.byte_type)
1477                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1478                                 if (real_target_type == TypeManager.short_type)
1479                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1480                                 if (real_target_type == TypeManager.ushort_type)
1481                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1482                                 if (real_target_type == TypeManager.int32_type)
1483                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1484                                 if (real_target_type == TypeManager.uint32_type)
1485                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1486                                 if (real_target_type == TypeManager.int64_type)
1487                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1488                                 if (real_target_type == TypeManager.uint64_type)
1489                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1490                                 if (real_target_type == TypeManager.char_type)
1491                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1492                                 if (real_target_type == TypeManager.float_type)
1493                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1494                         }
1495
1496                         // decimal is taken care of by the op_Explicit methods.
1497
1498                         return null;
1499                 }
1500
1501                 /// <summary>
1502                 ///  Returns whether an explicit reference conversion can be performed
1503                 ///  from source_type to target_type
1504                 /// </summary>
1505                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1506                 {
1507                         bool target_is_value_type = target_type.IsValueType;
1508
1509                         if (source_type == target_type)
1510                                 return true;
1511
1512                         //
1513                         // From object to any reference type
1514                         //
1515                         if (source_type == TypeManager.object_type && !target_is_value_type)
1516                                 return true;
1517
1518                         //
1519                         // From any class S to any class-type T, provided S is a base class of T
1520                         //
1521                         if (target_type.IsSubclassOf (source_type))
1522                                 return true;
1523
1524                         //
1525                         // From any interface type S to any interface T provided S is not derived from T
1526                         //
1527                         if (source_type.IsInterface && target_type.IsInterface){
1528                                 if (!target_type.IsSubclassOf (source_type))
1529                                         return true;
1530                         }
1531
1532                         //
1533                         // From any class type S to any interface T, provided S is not sealed
1534                         // and provided S does not implement T.
1535                         //
1536                         if (target_type.IsInterface && !source_type.IsSealed &&
1537                             !TypeManager.ImplementsInterface (source_type, target_type))
1538                                 return true;
1539
1540                         //
1541                         // From any interface-type S to to any class type T, provided T is not
1542                         // sealed, or provided T implements S.
1543                         //
1544                         if (source_type.IsInterface &&
1545                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1546                                 return true;
1547
1548
1549                         // From an array type S with an element type Se to an array type T with an
1550                         // element type Te provided all the following are true:
1551                         //     * S and T differe only in element type, in other words, S and T
1552                         //       have the same number of dimensions.
1553                         //     * Both Se and Te are reference types
1554                         //     * An explicit referenc conversions exist from Se to Te
1555                         //
1556                         if (source_type.IsArray && target_type.IsArray) {
1557                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1558
1559                                         Type source_element_type = TypeManager.GetElementType (source_type);
1560                                         Type target_element_type = TypeManager.GetElementType (target_type);
1561
1562                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1563                                                 if (ExplicitReferenceConversionExists (source_element_type,
1564                                                                                        target_element_type))
1565                                                         return true;
1566                                 }
1567                         }
1568
1569
1570                         // From System.Array to any array-type
1571                         if (source_type == TypeManager.array_type &&
1572                             target_type.IsArray){
1573                                 return true;
1574                         }
1575
1576                         //
1577                         // From System delegate to any delegate-type
1578                         //
1579                         if (source_type == TypeManager.delegate_type &&
1580                             target_type.IsSubclassOf (TypeManager.delegate_type))
1581                                 return true;
1582
1583                         //
1584                         // From ICloneable to Array or Delegate types
1585                         //
1586                         if (source_type == TypeManager.icloneable_type &&
1587                             (target_type == TypeManager.array_type ||
1588                              target_type == TypeManager.delegate_type))
1589                                 return true;
1590
1591                         return false;
1592                 }
1593
1594                 /// <summary>
1595                 ///   Implements Explicit Reference conversions
1596                 /// </summary>
1597                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1598                 {
1599                         Type source_type = source.Type;
1600                         bool target_is_value_type = target_type.IsValueType;
1601
1602                         //
1603                         // From object to any reference type
1604                         //
1605                         if (source_type == TypeManager.object_type && !target_is_value_type)
1606                                 return new ClassCast (source, target_type);
1607
1608                         //
1609                         // Unboxing conversion.
1610                         //
1611                         if (((source_type == TypeManager.enum_type &&
1612                                 !(source is EmptyCast)) ||
1613                                 source_type == TypeManager.value_type) && target_is_value_type)
1614                                 return new UnboxCast (source, target_type);
1615
1616                         //
1617                         // From any class S to any class-type T, provided S is a base class of T
1618                         //
1619                         if (target_type.IsSubclassOf (source_type))
1620                                 return new ClassCast (source, target_type);
1621
1622                         //
1623                         // From any interface type S to any interface T provided S is not derived from T
1624                         //
1625                         if (source_type.IsInterface && target_type.IsInterface){
1626                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1627                                         return null;
1628                                 else
1629                                         return new ClassCast (source, target_type);
1630                         }
1631
1632                         //
1633                         // From any class type S to any interface T, provides S is not sealed
1634                         // and provided S does not implement T.
1635                         //
1636                         if (target_type.IsInterface && !source_type.IsSealed) {
1637                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1638                                         return null;
1639                                 else
1640                                         return new ClassCast (source, target_type);
1641
1642                         }
1643
1644                         //
1645                         // From any interface-type S to to any class type T, provided T is not
1646                         // sealed, or provided T implements S.
1647                         //
1648                         if (source_type.IsInterface) {
1649                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1650                                         if (target_type.IsClass)
1651                                                 return new ClassCast (source, target_type);
1652                                         else
1653                                                 return new UnboxCast (source, target_type);
1654                                 }
1655
1656                                 return null;
1657                         }
1658
1659                         // From an array type S with an element type Se to an array type T with an
1660                         // element type Te provided all the following are true:
1661                         //     * S and T differe only in element type, in other words, S and T
1662                         //       have the same number of dimensions.
1663                         //     * Both Se and Te are reference types
1664                         //     * An explicit referenc conversions exist from Se to Te
1665                         //
1666                         if (source_type.IsArray && target_type.IsArray) {
1667                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1668
1669                                         Type source_element_type = TypeManager.GetElementType (source_type);
1670                                         Type target_element_type = TypeManager.GetElementType (target_type);
1671
1672                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1673                                                 if (ExplicitReferenceConversionExists (source_element_type,
1674                                                                                        target_element_type))
1675                                                         return new ClassCast (source, target_type);
1676                                 }
1677                         }
1678
1679
1680                         // From System.Array to any array-type
1681                         if (source_type == TypeManager.array_type &&
1682                             target_type.IsArray) {
1683                                 return new ClassCast (source, target_type);
1684                         }
1685
1686                         //
1687                         // From System delegate to any delegate-type
1688                         //
1689                         if (source_type == TypeManager.delegate_type &&
1690                             target_type.IsSubclassOf (TypeManager.delegate_type))
1691                                 return new ClassCast (source, target_type);
1692
1693                         //
1694                         // From ICloneable to Array or Delegate types
1695                         //
1696                         if (source_type == TypeManager.icloneable_type &&
1697                             (target_type == TypeManager.array_type ||
1698                              target_type == TypeManager.delegate_type))
1699                                 return new ClassCast (source, target_type);
1700
1701                         return null;
1702                 }
1703
1704                 /// <summary>
1705                 ///   Performs an explicit conversion of the expression `expr' whose
1706                 ///   type is expr.Type to `target_type'.
1707                 /// </summary>
1708                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1709                                                              Type target_type, Location loc)
1710                 {
1711                         Type expr_type = expr.Type;
1712                         Type original_expr_type = expr_type;
1713
1714                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1715                                 if (target_type == TypeManager.enum_type ||
1716                                     target_type == TypeManager.object_type) {
1717                                         if (expr is EnumConstant)
1718                                                 expr = ((EnumConstant) expr).Child;
1719                                         // We really need all these casts here .... :-(
1720                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1721                                         return new EmptyCast (expr, target_type);
1722                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1723                                            target_type.IsSubclassOf (TypeManager.enum_type))
1724                                         return new UnboxCast (expr, target_type);
1725
1726                                 //
1727                                 // Notice that we have kept the expr_type unmodified, which is only
1728                                 // used later on to
1729                                 if (expr is EnumConstant)
1730                                         expr = ((EnumConstant) expr).Child;
1731                                 else
1732                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1733                                 expr_type = expr.Type;
1734                         }
1735
1736                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1737
1738                         if (ne != null)
1739                                 return ne;
1740
1741                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1742                         if (ne != null)
1743                                 return ne;
1744
1745                         //
1746                         // Unboxing conversion.
1747                         //
1748                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1749                                 return new UnboxCast (expr, target_type);
1750
1751                         //
1752                         // Skip the ExplicitReferenceConversion because we can not convert
1753                         // from Null to a ValueType, and ExplicitReference wont check against
1754                         // null literal explicitly
1755                         //
1756                         if (expr_type != TypeManager.null_type){
1757                                 ne = ExplicitReferenceConversion (expr, target_type);
1758                                 if (ne != null)
1759                                         return ne;
1760                         }
1761
1762                 skip_explicit:
1763                         if (ec.InUnsafe){
1764                                 if (target_type.IsPointer){
1765                                         if (expr_type.IsPointer)
1766                                                 return new EmptyCast (expr, target_type);
1767
1768                                         if (expr_type == TypeManager.sbyte_type ||
1769                                             expr_type == TypeManager.byte_type ||
1770                                             expr_type == TypeManager.short_type ||
1771                                             expr_type == TypeManager.ushort_type ||
1772                                             expr_type == TypeManager.int32_type ||
1773                                             expr_type == TypeManager.uint32_type ||
1774                                             expr_type == TypeManager.uint64_type ||
1775                                             expr_type == TypeManager.int64_type)
1776                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1777                                 }
1778                                 if (expr_type.IsPointer){
1779                                         Expression e = null;
1780
1781                                         if (target_type == TypeManager.sbyte_type)
1782                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1783                                         else if (target_type == TypeManager.byte_type)
1784                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1785                                         else if (target_type == TypeManager.short_type)
1786                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1787                                         else if (target_type == TypeManager.ushort_type)
1788                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1789                                         else if (target_type == TypeManager.int32_type)
1790                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1791                                         else if (target_type == TypeManager.uint32_type)
1792                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1793                                         else if (target_type == TypeManager.uint64_type)
1794                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1795                                         else if (target_type == TypeManager.int64_type){
1796                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1797                                         }
1798
1799                                         if (e != null){
1800                                                 Expression ci, ce;
1801
1802                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1803
1804                                                 if (ci != null)
1805                                                         return ci;
1806
1807                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1808                                                 if (ce != null)
1809                                                         return ce;
1810                                                 //
1811                                                 // We should always be able to go from an uint32
1812                                                 // implicitly or explicitly to the other integral
1813                                                 // types
1814                                                 //
1815                                                 throw new Exception ("Internal compiler error");
1816                                         }
1817                                 }
1818                         }
1819
1820                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1821                         if (ne != null)
1822                                 return ne;
1823
1824                         if (expr is NullLiteral){
1825                                 Report.Error (37, loc, "Cannot convert null to value type `" +
1826                                               TypeManager.CSharpName (target_type) + "'");
1827                                 return null;
1828                         }
1829
1830                         Error_CannotConvertType (loc, original_expr_type, target_type);
1831                         return null;
1832                 }
1833
1834                 /// <summary>
1835                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1836                 /// </summary>
1837                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1838                                                                   Type target_type, Location l)
1839                 {
1840                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1841
1842                         if (ne != null)
1843                                 return ne;
1844
1845                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1846                         if (ne != null)
1847                                 return ne;
1848
1849                         ne = ExplicitReferenceConversion (expr, target_type);
1850                         if (ne != null)
1851                                 return ne;
1852
1853                         Error_CannotConvertType (l, expr.Type, target_type);
1854                         return null;
1855                 }
1856         }
1857 }