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 (NullPointer.Null, 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, decimal
 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                                 if (real_target_type == TypeManager.decimal_type)
 319                                         return new CastToDecimal (ec, expr);
 320                         } else if (expr_type == TypeManager.byte_type){
 321                                 //
 322                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 323                                 //
 324                                 if ((real_target_type == TypeManager.short_type) ||
 325                                     (real_target_type == TypeManager.ushort_type) ||
 326                                     (real_target_type == TypeManager.int32_type) ||
 327                                     (real_target_type == TypeManager.uint32_type))
 328                                         return new EmptyCast (expr, target_type);
 329
 330                                 if (real_target_type == TypeManager.uint64_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 332                                 if (real_target_type == TypeManager.int64_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 334                                 if (real_target_type == TypeManager.float_type)
 335                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 336                                 if (real_target_type == TypeManager.double_type)
 337                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 338                                 if (real_target_type == TypeManager.decimal_type)
 339                                         return new CastToDecimal (ec, expr);
 340
 341                         } else if (expr_type == TypeManager.short_type){
 342                                 //
 343                                 // From short to int, long, float, double, decimal
 344                                 //
 345                                 if (real_target_type == TypeManager.int32_type)
 346                                         return new EmptyCast (expr, target_type);
 347                                 if (real_target_type == TypeManager.int64_type)
 348                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 349                                 if (real_target_type == TypeManager.double_type)
 350                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 351                                 if (real_target_type == TypeManager.float_type)
 352                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 353                                 if (real_target_type == TypeManager.decimal_type)
 354                                         return new CastToDecimal (ec, expr);
 355
 356                         } else if (expr_type == TypeManager.ushort_type){
 357                                 //
 358                                 // From ushort to int, uint, long, ulong, float, double, decimal
 359                                 //
 360                                 if (real_target_type == TypeManager.uint32_type)
 361                                         return new EmptyCast (expr, target_type);
 362
 363                                 if (real_target_type == TypeManager.uint64_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 365                                 if (real_target_type == TypeManager.int32_type)
 366                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 367                                 if (real_target_type == TypeManager.int64_type)
 368                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 369                                 if (real_target_type == TypeManager.double_type)
 370                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 371                                 if (real_target_type == TypeManager.float_type)
 372                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 373                                 if (real_target_type == TypeManager.decimal_type)
 374                                         return new CastToDecimal (ec, expr);
 375                         } else if (expr_type == TypeManager.int32_type){
 376                                 //
 377                                 // From int to long, float, double, decimal
 378                                 //
 379                                 if (real_target_type == TypeManager.int64_type)
 380                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 381                                 if (real_target_type == TypeManager.double_type)
 382                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 383                                 if (real_target_type == TypeManager.float_type)
 384                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 385                                 if (real_target_type == TypeManager.decimal_type)
 386                                         return new CastToDecimal (ec, expr);
 387                         } else if (expr_type == TypeManager.uint32_type){
 388                                 //
 389                                 // From uint to long, ulong, float, double, decimal
 390                                 //
 391                                 if (real_target_type == TypeManager.int64_type)
 392                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 393                                 if (real_target_type == TypeManager.uint64_type)
 394                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 395                                 if (real_target_type == TypeManager.double_type)
 396                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 397                                                                OpCodes.Conv_R8);
 398                                 if (real_target_type == TypeManager.float_type)
 399                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 400                                                                OpCodes.Conv_R4);
 401                                 if (real_target_type == TypeManager.decimal_type)
 402                                         return new CastToDecimal (ec, expr);
 403                         } else if (expr_type == TypeManager.int64_type){
 404                                 //
 405                                 // From long/ulong to float, double
 406                                 //
 407                                 if (real_target_type == TypeManager.double_type)
 408                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 409                                 if (real_target_type == TypeManager.float_type)
 410                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 411                                 if (real_target_type == TypeManager.decimal_type)
 412                                         return new CastToDecimal (ec, expr);
 413                         } else if (expr_type == TypeManager.uint64_type){
 414                                 //
 415                                 // From ulong to float, double
 416                                 //
 417                                 if (real_target_type == TypeManager.double_type)
 418                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 419                                                                OpCodes.Conv_R8);
 420                                 if (real_target_type == TypeManager.float_type)
 421                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 422                                                                OpCodes.Conv_R4);
 423                                 if (real_target_type == TypeManager.decimal_type)
 424                                         return new CastToDecimal (ec, expr);
 425                         } else if (expr_type == TypeManager.char_type){
 426                                 //
 427                                 // From char to ushort, int, uint, long, ulong, float, double, decimal
 428                                 //
 429                                 if ((real_target_type == TypeManager.ushort_type) ||
 430                                     (real_target_type == TypeManager.int32_type) ||
 431                                     (real_target_type == TypeManager.uint32_type))
 432                                         return new EmptyCast (expr, target_type);
 433                                 if (real_target_type == TypeManager.uint64_type)
 434                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 435                                 if (real_target_type == TypeManager.int64_type)
 436                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 437                                 if (real_target_type == TypeManager.float_type)
 438                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 439                                 if (real_target_type == TypeManager.double_type)
 440                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 441                                 if (real_target_type == TypeManager.decimal_type)
 442                                         return new CastToDecimal (ec, expr);
 443                         } else if (expr_type == TypeManager.float_type){
 444                                 //
 445                                 // float to double
 446                                 //
 447                                 if (real_target_type == TypeManager.double_type)
 448                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 449                         }
 450
 451                         return null;
 452                 }
 453
 454
 455                 /// <summary>
 456                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 457                 ///  implicit user defined conversions - needed for overload resolution
 458                 /// </summary>
 459                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 460                 {
 461                         if (ImplicitStandardConversionExists (ec, expr, target_type))
 462                                 return true;
 463
 464                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 465
 466                         if (dummy != null)
 467                                 return true;
 468
 469                         return false;
 470                 }
 471
 472                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 473                 {
 474                         Expression dummy = ImplicitUserConversion (
 475                                 ec, new EmptyExpression (source), target, Location.Null);
 476                         return dummy != null;
 477                 }
 478
 479                 /// <summary>
 480                 ///  Determines if a standard implicit conversion exists from
 481                 ///  expr_type to target_type
 482                 ///
 483                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 484                 /// </summary>
 485                 public static bool ImplicitStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 486                 {
 487                         Type expr_type = expr.Type;
 488
 489                         if (expr_type == TypeManager.void_type)
 490                                 return false;
 491
 492                         if (expr_type == target_type)
 493                                 return true;
 494
 495
 496                         // First numeric conversions
 497
 498                         if (expr_type == TypeManager.sbyte_type){
 499                                 //
 500                                 // From sbyte to short, int, long, float, double, decimal
 501                                 //
 502                                 if ((target_type == TypeManager.int32_type) ||
 503                                     (target_type == TypeManager.int64_type) ||
 504                                     (target_type == TypeManager.double_type) ||
 505                                     (target_type == TypeManager.float_type)  ||
 506                                     (target_type == TypeManager.short_type) ||
 507                                     (target_type == TypeManager.decimal_type))
 508                                         return true;
 509
 510                         } else if (expr_type == TypeManager.byte_type){
 511                                 //
 512                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 513                                 //
 514                                 if ((target_type == TypeManager.short_type) ||
 515                                     (target_type == TypeManager.ushort_type) ||
 516                                     (target_type == TypeManager.int32_type) ||
 517                                     (target_type == TypeManager.uint32_type) ||
 518                                     (target_type == TypeManager.uint64_type) ||
 519                                     (target_type == TypeManager.int64_type) ||
 520                                     (target_type == TypeManager.float_type) ||
 521                                     (target_type == TypeManager.double_type) ||
 522                                     (target_type == TypeManager.decimal_type))
 523                                         return true;
 524
 525                         } else if (expr_type == TypeManager.short_type){
 526                                 //
 527                                 // From short to int, long, double, float, decimal
 528                                 //
 529                                 if ((target_type == TypeManager.int32_type) ||
 530                                     (target_type == TypeManager.int64_type) ||
 531                                     (target_type == TypeManager.double_type) ||
 532                                     (target_type == TypeManager.float_type) ||
 533                                     (target_type == TypeManager.decimal_type))
 534                                         return true;
 535
 536                         } else if (expr_type == TypeManager.ushort_type){
 537                                 //
 538                                 // From ushort to int, uint, long, ulong, double, float, decimal
 539                                 //
 540                                 if ((target_type == TypeManager.uint32_type) ||
 541                                     (target_type == TypeManager.uint64_type) ||
 542                                     (target_type == TypeManager.int32_type) ||
 543                                     (target_type == TypeManager.int64_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.int32_type){
 550                                 //
 551                                 // From int to long, double, float, decimal
 552                                 //
 553                                 if ((target_type == TypeManager.int64_type) ||
 554                                     (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.uint32_type){
 560                                 //
 561                                 // From uint to long, ulong, double, float, decimal
 562                                 //
 563                                 if ((target_type == TypeManager.int64_type) ||
 564                                     (target_type == TypeManager.uint64_type) ||
 565                                     (target_type == TypeManager.double_type) ||
 566                                     (target_type == TypeManager.float_type) ||
 567                                     (target_type == TypeManager.decimal_type))
 568                                         return true;
 569
 570                         } else if ((expr_type == TypeManager.uint64_type) ||
 571                                    (expr_type == TypeManager.int64_type)) {
 572                                 //
 573                                 // From long/ulong to double, float, decimal
 574                                 //
 575                                 if ((target_type == TypeManager.double_type) ||
 576                                     (target_type == TypeManager.float_type) ||
 577                                     (target_type == TypeManager.decimal_type))
 578                                         return true;
 579
 580                         } else if (expr_type == TypeManager.char_type){
 581                                 //
 582                                 // From char to ushort, int, uint, ulong, long, float, double, decimal
 583                                 //
 584                                 if ((target_type == TypeManager.ushort_type) ||
 585                                     (target_type == TypeManager.int32_type) ||
 586                                     (target_type == TypeManager.uint32_type) ||
 587                                     (target_type == TypeManager.uint64_type) ||
 588                                     (target_type == TypeManager.int64_type) ||
 589                                     (target_type == TypeManager.float_type) ||
 590                                     (target_type == TypeManager.double_type) ||
 591                                     (target_type == TypeManager.decimal_type))
 592                                         return true;
 593
 594                         } else if (expr_type == TypeManager.float_type){
 595                                 //
 596                                 // float to double
 597                                 //
 598                                 if (target_type == TypeManager.double_type)
 599                                         return true;
 600                         }
 601
 602                         if (expr.eclass == ExprClass.MethodGroup){
 603                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 604                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 605                                         if (mg != null){
 606                                                 //
 607                                                 // This should not happen frequently, so we can create an object
 608                                                 // to test compatibility
 609                                                 //
 610                                                 Expression c = ImplicitDelegateCreation.Create (
 611                                                         ec, mg, target_type, true, Location.Null);
 612                                                 return c != null;
 613                                         }
 614                                 }
 615                         }
 616
 617                         if (ImplicitReferenceConversionExists (expr, target_type))
 618                                 return true;
 619
 620                         //
 621                         // Implicit Constant Expression Conversions
 622                         //
 623                         if (expr is IntConstant){
 624                                 int value = ((IntConstant) expr).Value;
 625
 626                                 if (target_type == TypeManager.sbyte_type){
 627                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 628                                                 return true;
 629                                 } else if (target_type == TypeManager.byte_type){
 630                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 631                                                 return true;
 632                                 } else if (target_type == TypeManager.short_type){
 633                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 634                                                 return true;
 635                                 } else if (target_type == TypeManager.ushort_type){
 636                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 637                                                 return true;
 638                                 } else if (target_type == TypeManager.uint32_type){
 639                                         if (value >= 0)
 640                                                 return true;
 641                                 } else if (target_type == TypeManager.uint64_type){
 642                                          //
 643                                          // we can optimize this case: a positive int32
 644                                          // always fits on a uint64.  But we need an opcode
 645                                          // to do it.
 646                                          //
 647                                         if (value >= 0)
 648                                                 return true;
 649                                 }
 650
 651                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 652                                         return true;
 653                         }
 654
 655                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 656                                 //
 657                                 // Try the implicit constant expression conversion
 658                                 // from long to ulong, instead of a nice routine,
 659                                 // we just inline it
 660                                 //
 661                                 long v = ((LongConstant) expr).Value;
 662                                 if (v > 0)
 663                                         return true;
 664                         }
 665
 666                         if ((target_type == TypeManager.enum_type ||
 667                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 668                              expr is IntLiteral){
 669                                 IntLiteral i = (IntLiteral) expr;
 670
 671                                 if (i.Value == 0)
 672                                         return true;
 673                         }
 674
 675                         //
 676                         // If `expr_type' implements `target_type' (which is an iface)
 677                         // see TryImplicitIntConversion
 678                         //
 679                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 680                                 return true;
 681
 682                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 683                                 return true;
 684
 685                         if (expr_type == TypeManager.anonymous_method_type){
 686                                 if (!TypeManager.IsDelegateType (target_type))
 687                                         return false;
 688
 689                                 AnonymousMethod am = (AnonymousMethod) expr;
 690
 691                                 Expression conv = am.Compatible (ec, target_type, true);
 692                                 if (conv != null)
 693                                         return true;
 694                         }
 695
 696                         return false;
 697                 }
 698
 699                 /// <summary>
 700                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 701                 ///  amongst the methods in the MethodGroupExpr
 702                 /// </summary>
 703                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 704                 {
 705                         Type best = null;
 706
 707                         if (types.Count == 0)
 708                                 return null;
 709
 710                         if (types.Count == 1)
 711                                 return (Type) types [0];
 712
 713                         EmptyExpression expr = EmptyExpression.Grab ();
 714
 715                         foreach (Type t in types) {
 716                                 if (best == null) {
 717                                         best = t;
 718                                         continue;
 719                                 }
 720
 721                                 expr.SetType (t);
 722                                 if (ImplicitStandardConversionExists (ec, expr, best))
 723                                         best = t;
 724                         }
 725
 726                         expr.SetType (best);
 727                         foreach (Type t in types) {
 728                                 if (best == t)
 729                                         continue;
 730                                 if (!ImplicitStandardConversionExists (ec, expr, t)) {
 731                                         best = null;
 732                                         break;
 733                                 }
 734                         }
 735
 736                         EmptyExpression.Release (expr);
 737
 738                         return best;
 739                 }
 740
 741                 /// <summary>
 742                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 743                 ///  amongst the types in the given set
 744                 /// </summary>
 745                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 746                 {
 747                         Type best = null;
 748
 749                         if (types.Count == 0)
 750                                 return null;
 751
 752                         if (types.Count == 1)
 753                                 return (Type) types [0];
 754
 755                         EmptyExpression expr = EmptyExpression.Grab ();
 756
 757                         foreach (Type t in types) {
 758                                 if (best == null) {
 759                                         best = t;
 760                                         continue;
 761                                 }
 762
 763                                 expr.SetType (best);
 764                                 if (ImplicitStandardConversionExists (ec, expr, t))
 765                                         best = t;
 766                         }
 767
 768                         foreach (Type t in types) {
 769                                 if (best == t)
 770                                         continue;
 771                                 expr.SetType (t);
 772                                 if (!ImplicitStandardConversionExists (ec, expr, best)) {
 773                                         best = null;
 774                                         break;
 775                                 }
 776                         }
 777
 778                         EmptyExpression.Release (expr);
 779
 780                         return best;
 781                 }
 782
 783                 /// <summary>
 784                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 785                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 786                 ///   for explicit and implicit conversion operators.
 787                 /// </summary>
 788                 static public Type FindMostSpecificSource (EmitContext ec, IList list,
 789                                                            Expression source, bool apply_explicit_conv_rules,
 790                                                            Location loc)
 791                 {
 792                         ArrayList src_types_set = new ArrayList ();
 793
 794                         //
 795                         // If any operator converts from S then Sx = S
 796                         //
 797                         Type source_type = source.Type;
 798                         foreach (MethodBase mb in list){
 799                                 ParameterData pd = TypeManager.GetParameterData (mb);
 800                                 Type param_type = pd.ParameterType (0);
 801
 802                                 if (param_type == source_type)
 803                                         return param_type;
 804
 805                                 src_types_set.Add (param_type);
 806                         }
 807
 808                         //
 809                         // Explicit Conv rules
 810                         //
 811                         if (apply_explicit_conv_rules) {
 812                                 ArrayList candidate_set = new ArrayList ();
 813
 814                                 foreach (Type param_type in src_types_set){
 815                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 816                                                 candidate_set.Add (param_type);
 817                                 }
 818
 819                                 if (candidate_set.Count != 0)
 820                                         return FindMostEncompassedType (ec, candidate_set);
 821                         }
 822
 823                         //
 824                         // Final case
 825                         //
 826                         if (apply_explicit_conv_rules)
 827                                 return FindMostEncompassingType (ec, src_types_set);
 828                         else
 829                                 return FindMostEncompassedType (ec, src_types_set);
 830                 }
 831
 832                 /// <summary>
 833                 ///  Finds the most specific target Tx according to section 13.4.4
 834                 /// </summary>
 835                 static public Type FindMostSpecificTarget (EmitContext ec, IList list,
 836                                                            Type target, bool apply_explicit_conv_rules,
 837                                                            Location loc)
 838                 {
 839                         ArrayList tgt_types_set = new ArrayList ();
 840
 841                         //
 842                         // If any operator converts to T then Tx = T
 843                         //
 844                         foreach (MethodInfo mi in list){
 845                                 Type ret_type = mi.ReturnType;
 846                                 if (ret_type == target)
 847                                         return ret_type;
 848
 849                                 tgt_types_set.Add (ret_type);
 850                         }
 851
 852                         //
 853                         // Explicit conv rules
 854                         //
 855                         if (apply_explicit_conv_rules) {
 856                                 ArrayList candidate_set = new ArrayList ();
 857
 858                                 EmptyExpression expr = EmptyExpression.Grab ();
 859
 860                                 foreach (Type ret_type in tgt_types_set){
 861                                         expr.SetType (ret_type);
 862
 863                                         if (ImplicitStandardConversionExists (ec, expr, target))
 864                                                 candidate_set.Add (ret_type);
 865                                 }
 866
 867                                 EmptyExpression.Release (expr);
 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 void AddConversionOperators (EmitContext ec, ArrayList list,
 901                                                     Expression source, Type target_type,
 902                                                     bool look_for_explicit,
 903                                                     MethodGroupExpr mg)
 904                 {
 905                         if (mg == null)
 906                                 return;
 907
 908                         Type source_type = source.Type;
 909                         EmptyExpression expr = EmptyExpression.Grab ();
 910                         foreach (MethodInfo m in mg.Methods) {
 911                                 ParameterData pd = TypeManager.GetParameterData (m);
 912                                 Type return_type = m.ReturnType;
 913                                 Type arg_type = pd.ParameterType (0);
 914
 915                                 if (source_type != arg_type) {
 916                                         if (!ImplicitStandardConversionExists (ec, source, arg_type)) {
 917                                                 if (!look_for_explicit)
 918                                                         continue;
 919                                                 expr.SetType (arg_type);
 920                                                 if (!ImplicitStandardConversionExists (ec, expr, source_type))
 921                                                         continue;
 922                                         }
 923                                 }
 924
 925                                 if (target_type != return_type) {
 926                                         expr.SetType (return_type);
 927                                         if (!ImplicitStandardConversionExists (ec, expr, target_type)) {
 928                                                 if (!look_for_explicit)
 929                                                         continue;
 930                                                 expr.SetType (target_type);
 931                                                 if (!ImplicitStandardConversionExists (ec, expr, return_type))
 932                                                         continue;
 933                                         }
 934                                 }
 935
 936                                 list.Add (m);
 937                         }
 938
 939                         EmptyExpression.Release (expr);
 940                 }
 941
 942                 /// <summary>
 943                 ///   Computes the list of the user-defined conversion
 944                 ///   operators from source_type to target_type.  `look_for_explicit'
 945                 ///   controls whether we should also include the list of explicit
 946                 ///   operators
 947                 /// </summary>
 948                 static IList GetConversionOperators (EmitContext ec,
 949                                                      Expression source, Type target_type,
 950                                                      Location loc, bool look_for_explicit)
 951                 {
 952                         ArrayList ret = new ArrayList (4);
 953
 954                         Type source_type = source.Type;
 955
 956                         if (source_type != TypeManager.decimal_type) {
 957                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 958                                         Expression.MethodLookup (
 959                                                 ec, source_type, "op_Implicit", loc) as MethodGroupExpr);
 960                                 if (look_for_explicit) {
 961                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 962                                                 Expression.MethodLookup (
 963                                                         ec, source_type, "op_Explicit", loc) as MethodGroupExpr);
 964                                 }
 965                         }
 966
 967                         if (target_type != TypeManager.decimal_type) {
 968                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 969                                         Expression.MethodLookup (
 970                                                 ec, target_type, "op_Implicit", loc) as MethodGroupExpr);
 971                                 if (look_for_explicit) {
 972                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 973                                                 Expression.MethodLookup (
 974                                                         ec, target_type, "op_Explicit", loc) as MethodGroupExpr);
 975                                 }
 976                         }
 977
 978                         return ret;
 979                 }
 980
 981                 static DoubleHash explicit_conv = new DoubleHash (100);
 982                 static DoubleHash implicit_conv = new DoubleHash (100);
 983
 984                 /// <summary>
 985                 ///   User-defined conversions
 986                 /// </summary>
 987                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 988                                                                 Type target, Location loc,
 989                                                                 bool look_for_explicit)
 990                 {
 991                         Type source_type = source.Type;
 992                         MethodInfo method = null;
 993                         Type most_specific_source = null;
 994                         Type most_specific_target = null;
 995
 996                         object o;
 997                         DoubleHash hash = look_for_explicit ? explicit_conv : implicit_conv;
 998
 999                         if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
1000                                 method = (MethodInfo) o;
1001                                 if (method != null) {
1002                                         ParameterData pd = TypeManager.GetParameterData (method);
1003                                         most_specific_source = pd.ParameterType (0);
1004                                         most_specific_target = method.ReturnType;
1005                                 }
1006                         } else {
1007                                 IList ops = GetConversionOperators (ec, source, target, loc, look_for_explicit);
1008                                 if (ops == null || ops.Count == 0) {
1009                                         method = null;
1010                                         goto skip;
1011                                 }
1012
1013                                 most_specific_source = FindMostSpecificSource (ec, ops, source, look_for_explicit, loc);
1014                                 if (most_specific_source == null) {
1015                                         method = null;
1016                                         goto skip;
1017                                 }
1018
1019                                 most_specific_target = FindMostSpecificTarget (ec, ops, target, look_for_explicit, loc);
1020                                 if (most_specific_target == null) {
1021                                         method = null;
1022                                         goto skip;
1023                                 }
1024
1025                                 int count = 0;
1026
1027                                 foreach (MethodInfo m in ops) {
1028                                         ParameterData pd = TypeManager.GetParameterData (m);
1029
1030                                         if (pd.ParameterType (0) == most_specific_source &&
1031                                             m.ReturnType == most_specific_target) {
1032                                                 method = m;
1033                                                 count++;
1034                                         }
1035                                 }
1036                                 if (count > 1)
1037                                         method = null;
1038
1039                         skip:
1040                                 if (!(source is Constant))
1041                                         hash.Insert (source_type, target, method);
1042                         }
1043
1044                         if (method == null)
1045                                 return null;
1046
1047                         //
1048                         // This will do the conversion to the best match that we
1049                         // found.  Now we need to perform an implict standard conversion
1050                         // if the best match was not the type that we were requested
1051                         // by target.
1052                         //
1053                         if (look_for_explicit)
1054                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1055                         else
1056                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1057
1058                         if (source == null)
1059                                 return null;
1060
1061                         Expression e;
1062                         e =  new UserCast (method, source, loc);
1063                         if (e.Type != target){
1064                                 if (!look_for_explicit)
1065                                         e = ImplicitConversionStandard (ec, e, target, loc);
1066                                 else
1067                                         e = ExplicitConversionStandard (ec, e, target, loc);
1068                         }
1069
1070                         return e;
1071                 }
1072
1073                 /// <summary>
1074                 ///   Converts implicitly the resolved expression `expr' into the
1075                 ///   `target_type'.  It returns a new expression that can be used
1076                 ///   in a context that expects a `target_type'.
1077                 /// </summary>
1078                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1079                                                              Type target_type, Location loc)
1080                 {
1081                         Expression e;
1082
1083                         if (target_type == null)
1084                                 throw new Exception ("Target type is null");
1085
1086                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1087                         if (e != null)
1088                                 return e;
1089
1090                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1091                         if (e != null)
1092                                 return e;
1093
1094                         return null;
1095                 }
1096
1097
1098                 /// <summary>
1099                 ///   Attempts to apply the `Standard Implicit
1100                 ///   Conversion' rules to the expression `expr' into
1101                 ///   the `target_type'.  It returns a new expression
1102                 ///   that can be used in a context that expects a
1103                 ///   `target_type'.
1104                 ///
1105                 ///   This is different from `ImplicitConversion' in that the
1106                 ///   user defined implicit conversions are excluded.
1107                 /// </summary>
1108                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1109                                                                      Type target_type, Location loc)
1110                 {
1111                         Type expr_type = expr.Type;
1112                         Expression e;
1113
1114                         if (expr.eclass == ExprClass.MethodGroup){
1115                                 if (!TypeManager.IsDelegateType (target_type)){
1116                                         return null;
1117                                 }
1118
1119                                 //
1120                                 // Only allow anonymous method conversions on post ISO_1
1121                                 //
1122                                 if (RootContext.Version != LanguageVersion.ISO_1){
1123                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1124                                         if (mg != null)
1125                                                 return ImplicitDelegateCreation.Create (
1126                                                         ec, mg, target_type, false, loc);
1127                                 }
1128                         }
1129
1130                         if (expr_type == target_type && expr_type != TypeManager.null_type)
1131                                 return expr;
1132
1133                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1134                         if (e != null)
1135                                 return e;
1136
1137                         e = ImplicitReferenceConversion (expr, target_type);
1138                         if (e != null)
1139                                 return e;
1140
1141                         if ((target_type == TypeManager.enum_type ||
1142                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1143                             expr is IntLiteral){
1144                                 IntLiteral i = (IntLiteral) expr;
1145
1146                                 if (i.Value == 0)
1147                                         return new EnumConstant ((Constant) expr, target_type);
1148                         }
1149
1150                         if (ec.InUnsafe) {
1151                                 if (expr_type.IsPointer){
1152                                         if (target_type == TypeManager.void_ptr_type)
1153                                                 return new EmptyCast (expr, target_type);
1154
1155                                         //
1156                                         // yep, comparing pointer types cant be done with
1157                                         // t1 == t2, we have to compare their element types.
1158                                         //
1159                                         if (target_type.IsPointer){
1160                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1161                                                         return expr;
1162                                         }
1163                                 }
1164
1165                                 if (target_type.IsPointer) {
1166                                         if (expr_type == TypeManager.null_type)
1167                                                 return new EmptyCast (NullPointer.Null, target_type);
1168
1169                                         if (expr_type == TypeManager.void_ptr_type)
1170                                                 return new EmptyCast (expr, target_type);
1171                                 }
1172                         }
1173
1174                         if (expr_type == TypeManager.anonymous_method_type){
1175                                 if (!TypeManager.IsDelegateType (target_type)){
1176                                         Report.Error (1660, loc,
1177                                                 "Cannot convert anonymous method block to type `{0}' because it is not a delegate type",
1178                                                 TypeManager.CSharpName (target_type));
1179                                         return null;
1180                                 }
1181
1182                                 AnonymousMethod am = (AnonymousMethod) expr;
1183                                 int errors = Report.Errors;
1184
1185                                 Expression conv = am.Compatible (ec, target_type, false);
1186                                 if (conv != null)
1187                                         return conv;
1188
1189                                 //
1190                                 // We return something instead of null, to avoid
1191                                 // the duplicate error, since am.Compatible would have
1192                                 // reported that already
1193                                 //
1194                                 if (errors != Report.Errors)
1195                                         return new EmptyCast (expr, target_type);
1196                         }
1197
1198                         return null;
1199                 }
1200
1201                 /// <summary>
1202                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1203                 ///   into a different data type using casts (See Implicit Constant
1204                 ///   Expression Conversions)
1205                 /// </summary>
1206                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1207                 {
1208                         int value = ic.Value;
1209
1210                         if (target_type == TypeManager.sbyte_type){
1211                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1212                                         return new SByteConstant ((sbyte) value);
1213                         } else if (target_type == TypeManager.byte_type){
1214                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1215                                         return new ByteConstant ((byte) value);
1216                         } else if (target_type == TypeManager.short_type){
1217                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1218                                         return new ShortConstant ((short) value);
1219                         } else if (target_type == TypeManager.ushort_type){
1220                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1221                                         return new UShortConstant ((ushort) value);
1222                         } else if (target_type == TypeManager.uint32_type){
1223                                 if (value >= 0)
1224                                         return new UIntConstant ((uint) value);
1225                         } else if (target_type == TypeManager.uint64_type){
1226                                 //
1227                                 // we can optimize this case: a positive int32
1228                                 // always fits on a uint64.  But we need an opcode
1229                                 // to do it.
1230                                 //
1231                                 if (value >= 0)
1232                                         return new ULongConstant ((ulong) value);
1233                         } else if (target_type == TypeManager.double_type)
1234                                 return new DoubleConstant ((double) value);
1235                         else if (target_type == TypeManager.float_type)
1236                                 return new FloatConstant ((float) value);
1237
1238                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1239                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1240                                 Constant e = (Constant) ic;
1241
1242                                 //
1243                                 // Possibly, we need to create a different 0 literal before passing
1244                                 // to EnumConstant
1245                                 //
1246                                 if (underlying == TypeManager.int64_type)
1247                                         e = new LongLiteral (0);
1248                                 else if (underlying == TypeManager.uint64_type)
1249                                         e = new ULongLiteral (0);
1250
1251                                 return new EnumConstant (e, target_type);
1252                         }
1253
1254                         //
1255                         // If `target_type' is an interface and the type of `ic' implements the interface
1256                         // e.g. target_type is IComparable, IConvertible, IFormattable
1257                         //
1258                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1259                                 return new BoxedCast (ic);
1260
1261                         return null;
1262                 }
1263
1264                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1265                 {
1266                         if (source.Name == target.Name){
1267                                 Report.ExtraInformation (loc,
1268                                          String.Format (
1269                                                 "The type {0} has two conflicting definitions, one comes from {1} and the other from {2}",
1270                                                 source.Name, source.Assembly.FullName, target.Assembly.FullName));
1271
1272                         }
1273                         Report.Error (29, loc, "Cannot implicitly convert type {0} to `{1}'",
1274                                       source == TypeManager.anonymous_method_type ?
1275                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1276                                       TypeManager.CSharpName (target));
1277                 }
1278
1279                 /// <summary>
1280                 ///   Attempts to implicitly convert `source' into `target_type', using
1281                 ///   ImplicitConversion.  If there is no implicit conversion, then
1282                 ///   an error is signaled
1283                 /// </summary>
1284                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1285                                                                      Type target_type, Location loc)
1286                 {
1287                         Expression e;
1288
1289                         e = ImplicitConversion (ec, source, target_type, loc);
1290                         if (e != null)
1291                                 return e;
1292
1293                         if (source is DoubleLiteral) {
1294                                 if (target_type == TypeManager.float_type) {
1295                                         Error_664 (loc, "float", "f");
1296                                         return null;
1297                                 }
1298                                 if (target_type == TypeManager.decimal_type) {
1299                                         Error_664 (loc, "decimal", "m");
1300                                         return null;
1301                                 }
1302                         }
1303
1304                         if (source is Constant){
1305                                 Constant c = (Constant) source;
1306
1307                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1308                                 return null;
1309                         }
1310
1311                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1312
1313                         return null;
1314                 }
1315
1316                 static void Error_664 (Location loc, string type, string suffix) {
1317                         Report.Error (664, loc,
1318                                 "Literal of type double cannot be implicitly converted to type `{0}'. Add suffix `{1}' to create a literal of this type",
1319                                 type, suffix);
1320                 }
1321
1322                 /// <summary>
1323                 ///   Performs the explicit numeric conversions
1324                 /// </summary>
1325                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1326                 {
1327                         Type expr_type = expr.Type;
1328
1329                         //
1330                         // If we have an enumeration, extract the underlying type,
1331                         // use this during the comparison, but wrap around the original
1332                         // target_type
1333                         //
1334                         Type real_target_type = target_type;
1335
1336                         if (TypeManager.IsEnumType (real_target_type))
1337                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1338
1339                         if (ImplicitStandardConversionExists (ec, expr, real_target_type)){
1340                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1341
1342                                 if (real_target_type != target_type)
1343                                         return new EmptyCast (ce, target_type);
1344                                 return ce;
1345                         }
1346
1347                         if (expr_type == TypeManager.sbyte_type){
1348                                 //
1349                                 // From sbyte to byte, ushort, uint, ulong, char
1350                                 //
1351                                 if (real_target_type == TypeManager.byte_type)
1352                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1353                                 if (real_target_type == TypeManager.ushort_type)
1354                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1355                                 if (real_target_type == TypeManager.uint32_type)
1356                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1357                                 if (real_target_type == TypeManager.uint64_type)
1358                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1359                                 if (real_target_type == TypeManager.char_type)
1360                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1361                         } else if (expr_type == TypeManager.byte_type){
1362                                 //
1363                                 // From byte to sbyte and char
1364                                 //
1365                                 if (real_target_type == TypeManager.sbyte_type)
1366                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1367                                 if (real_target_type == TypeManager.char_type)
1368                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1369                         } else if (expr_type == TypeManager.short_type){
1370                                 //
1371                                 // From short to sbyte, byte, ushort, uint, ulong, char
1372                                 //
1373                                 if (real_target_type == TypeManager.sbyte_type)
1374                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1375                                 if (real_target_type == TypeManager.byte_type)
1376                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1377                                 if (real_target_type == TypeManager.ushort_type)
1378                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1379                                 if (real_target_type == TypeManager.uint32_type)
1380                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1381                                 if (real_target_type == TypeManager.uint64_type)
1382                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1383                                 if (real_target_type == TypeManager.char_type)
1384                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1385                         } else if (expr_type == TypeManager.ushort_type){
1386                                 //
1387                                 // From ushort to sbyte, byte, short, char
1388                                 //
1389                                 if (real_target_type == TypeManager.sbyte_type)
1390                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1391                                 if (real_target_type == TypeManager.byte_type)
1392                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1393                                 if (real_target_type == TypeManager.short_type)
1394                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1395                                 if (real_target_type == TypeManager.char_type)
1396                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1397                         } else if (expr_type == TypeManager.int32_type){
1398                                 //
1399                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1400                                 //
1401                                 if (real_target_type == TypeManager.sbyte_type)
1402                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1403                                 if (real_target_type == TypeManager.byte_type)
1404                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1405                                 if (real_target_type == TypeManager.short_type)
1406                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1407                                 if (real_target_type == TypeManager.ushort_type)
1408                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1409                                 if (real_target_type == TypeManager.uint32_type)
1410                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1411                                 if (real_target_type == TypeManager.uint64_type)
1412                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1413                                 if (real_target_type == TypeManager.char_type)
1414                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1415                         } else if (expr_type == TypeManager.uint32_type){
1416                                 //
1417                                 // From uint to sbyte, byte, short, ushort, int, char
1418                                 //
1419                                 if (real_target_type == TypeManager.sbyte_type)
1420                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1421                                 if (real_target_type == TypeManager.byte_type)
1422                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1423                                 if (real_target_type == TypeManager.short_type)
1424                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1425                                 if (real_target_type == TypeManager.ushort_type)
1426                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1427                                 if (real_target_type == TypeManager.int32_type)
1428                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1429                                 if (real_target_type == TypeManager.char_type)
1430                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1431                         } else if (expr_type == TypeManager.int64_type){
1432                                 //
1433                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1434                                 //
1435                                 if (real_target_type == TypeManager.sbyte_type)
1436                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1437                                 if (real_target_type == TypeManager.byte_type)
1438                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1439                                 if (real_target_type == TypeManager.short_type)
1440                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1441                                 if (real_target_type == TypeManager.ushort_type)
1442                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1443                                 if (real_target_type == TypeManager.int32_type)
1444                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1445                                 if (real_target_type == TypeManager.uint32_type)
1446                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1447                                 if (real_target_type == TypeManager.uint64_type)
1448                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1449                                 if (real_target_type == TypeManager.char_type)
1450                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1451                         } else if (expr_type == TypeManager.uint64_type){
1452                                 //
1453                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1454                                 //
1455                                 if (real_target_type == TypeManager.sbyte_type)
1456                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1457                                 if (real_target_type == TypeManager.byte_type)
1458                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1459                                 if (real_target_type == TypeManager.short_type)
1460                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1461                                 if (real_target_type == TypeManager.ushort_type)
1462                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1463                                 if (real_target_type == TypeManager.int32_type)
1464                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1465                                 if (real_target_type == TypeManager.uint32_type)
1466                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1467                                 if (real_target_type == TypeManager.int64_type)
1468                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1469                                 if (real_target_type == TypeManager.char_type)
1470                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1471                         } else if (expr_type == TypeManager.char_type){
1472                                 //
1473                                 // From char to sbyte, byte, short
1474                                 //
1475                                 if (real_target_type == TypeManager.sbyte_type)
1476                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1477                                 if (real_target_type == TypeManager.byte_type)
1478                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1479                                 if (real_target_type == TypeManager.short_type)
1480                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1481                         } else if (expr_type == TypeManager.float_type){
1482                                 //
1483                                 // From float to sbyte, byte, short,
1484                                 // ushort, int, uint, long, ulong, char
1485                                 // or decimal
1486                                 //
1487                                 if (real_target_type == TypeManager.sbyte_type)
1488                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1489                                 if (real_target_type == TypeManager.byte_type)
1490                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1491                                 if (real_target_type == TypeManager.short_type)
1492                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1493                                 if (real_target_type == TypeManager.ushort_type)
1494                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1495                                 if (real_target_type == TypeManager.int32_type)
1496                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1497                                 if (real_target_type == TypeManager.uint32_type)
1498                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1499                                 if (real_target_type == TypeManager.int64_type)
1500                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1501                                 if (real_target_type == TypeManager.uint64_type)
1502                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1503                                 if (real_target_type == TypeManager.char_type)
1504                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1505                                 if (real_target_type == TypeManager.decimal_type)
1506                                         return new CastToDecimal (ec, expr, true);
1507                         } else if (expr_type == TypeManager.double_type){
1508                                 //
1509                                 // From double to sbyte, byte, short,
1510                                 // ushort, int, uint, long, ulong,
1511                                 // char, float or decimal
1512                                 //
1513                                 if (real_target_type == TypeManager.sbyte_type)
1514                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1515                                 if (real_target_type == TypeManager.byte_type)
1516                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1517                                 if (real_target_type == TypeManager.short_type)
1518                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1519                                 if (real_target_type == TypeManager.ushort_type)
1520                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1521                                 if (real_target_type == TypeManager.int32_type)
1522                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1523                                 if (real_target_type == TypeManager.uint32_type)
1524                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1525                                 if (real_target_type == TypeManager.int64_type)
1526                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1527                                 if (real_target_type == TypeManager.uint64_type)
1528                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1529                                 if (real_target_type == TypeManager.char_type)
1530                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1531                                 if (real_target_type == TypeManager.float_type)
1532                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1533                                 if (real_target_type == TypeManager.decimal_type)
1534                                         return new CastToDecimal (ec, expr, true);
1535                         } else if (expr_type == TypeManager.decimal_type) {
1536                                 //
1537                                 // From decimal to sbyte, byte, short, ushort, int, uint,
1538                                 // long, ulong, char, double or float
1539                                 //
1540                                 if (real_target_type == TypeManager.sbyte_type ||
1541                                     real_target_type == TypeManager.byte_type ||
1542                                     real_target_type == TypeManager.short_type ||
1543                                     real_target_type == TypeManager.ushort_type ||
1544                                     real_target_type == TypeManager.int32_type ||
1545                                     real_target_type == TypeManager.uint32_type ||
1546                                     real_target_type == TypeManager.int64_type ||
1547                                     real_target_type == TypeManager.uint64_type ||
1548                                     real_target_type == TypeManager.char_type ||
1549                                     real_target_type == TypeManager.double_type ||
1550                                     real_target_type == TypeManager.float_type)
1551                                         return new CastFromDecimal (ec, expr, target_type);
1552                         }
1553                         return null;
1554                 }
1555
1556                 /// <summary>
1557                 ///  Returns whether an explicit reference conversion can be performed
1558                 ///  from source_type to target_type
1559                 /// </summary>
1560                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1561                 {
1562                         bool target_is_value_type = target_type.IsValueType;
1563
1564                         if (source_type == target_type)
1565                                 return true;
1566
1567                         //
1568                         // From object to any reference type
1569                         //
1570                         if (source_type == TypeManager.object_type && !target_is_value_type)
1571                                 return true;
1572
1573                         //
1574                         // From any class S to any class-type T, provided S is a base class of T
1575                         //
1576                         if (target_type.IsSubclassOf (source_type))
1577                                 return true;
1578
1579                         //
1580                         // From any interface type S to any interface T provided S is not derived from T
1581                         //
1582                         if (source_type.IsInterface && target_type.IsInterface){
1583                                 if (!target_type.IsSubclassOf (source_type))
1584                                         return true;
1585                         }
1586
1587                         //
1588                         // From any class type S to any interface T, provided S is not sealed
1589                         // and provided S does not implement T.
1590                         //
1591                         if (target_type.IsInterface && !source_type.IsSealed &&
1592                             !TypeManager.ImplementsInterface (source_type, target_type))
1593                                 return true;
1594
1595                         //
1596                         // From any interface-type S to to any class type T, provided T is not
1597                         // sealed, or provided T implements S.
1598                         //
1599                         if (source_type.IsInterface &&
1600                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1601                                 return true;
1602
1603
1604                         // From an array type S with an element type Se to an array type T with an
1605                         // element type Te provided all the following are true:
1606                         //     * S and T differe only in element type, in other words, S and T
1607                         //       have the same number of dimensions.
1608                         //     * Both Se and Te are reference types
1609                         //     * An explicit referenc conversions exist from Se to Te
1610                         //
1611                         if (source_type.IsArray && target_type.IsArray) {
1612                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1613
1614                                         Type source_element_type = TypeManager.GetElementType (source_type);
1615                                         Type target_element_type = TypeManager.GetElementType (target_type);
1616
1617                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1618                                                 if (ExplicitReferenceConversionExists (source_element_type,
1619                                                                                        target_element_type))
1620                                                         return true;
1621                                 }
1622                         }
1623
1624
1625                         // From System.Array to any array-type
1626                         if (source_type == TypeManager.array_type &&
1627                             target_type.IsArray){
1628                                 return true;
1629                         }
1630
1631                         //
1632                         // From System delegate to any delegate-type
1633                         //
1634                         if (source_type == TypeManager.delegate_type &&
1635                             target_type.IsSubclassOf (TypeManager.delegate_type))
1636                                 return true;
1637
1638                         //
1639                         // From ICloneable to Array or Delegate types
1640                         //
1641                         if (source_type == TypeManager.icloneable_type &&
1642                             (target_type == TypeManager.array_type ||
1643                              target_type == TypeManager.delegate_type))
1644                                 return true;
1645
1646                         return false;
1647                 }
1648
1649                 /// <summary>
1650                 ///   Implements Explicit Reference conversions
1651                 /// </summary>
1652                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1653                 {
1654                         Type source_type = source.Type;
1655                         bool target_is_value_type = target_type.IsValueType;
1656
1657                         //
1658                         // From object to any reference type
1659                         //
1660                         if (source_type == TypeManager.object_type && !target_is_value_type)
1661                                 return new ClassCast (source, target_type);
1662
1663                         //
1664                         // Unboxing conversion.
1665                         //
1666                         if (((source_type == TypeManager.enum_type &&
1667                                 !(source is EmptyCast)) ||
1668                                 source_type == TypeManager.value_type) && target_is_value_type)
1669                                 return new UnboxCast (source, target_type);
1670
1671                         //
1672                         // From any class S to any class-type T, provided S is a base class of T
1673                         //
1674                         if (target_type.IsSubclassOf (source_type))
1675                                 return new ClassCast (source, target_type);
1676
1677                         //
1678                         // From any interface type S to any interface T provided S is not derived from T
1679                         //
1680                         if (source_type.IsInterface && target_type.IsInterface){
1681                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1682                                         return null;
1683                                 else
1684                                         return new ClassCast (source, target_type);
1685                         }
1686
1687                         //
1688                         // From any class type S to any interface T, provides S is not sealed
1689                         // and provided S does not implement T.
1690                         //
1691                         if (target_type.IsInterface && !source_type.IsSealed) {
1692                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1693                                         return null;
1694                                 else
1695                                         return new ClassCast (source, target_type);
1696
1697                         }
1698
1699                         //
1700                         // From any interface-type S to to any class type T, provided T is not
1701                         // sealed, or provided T implements S.
1702                         //
1703                         if (source_type.IsInterface) {
1704                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1705                                         if (target_type.IsClass)
1706                                                 return new ClassCast (source, target_type);
1707                                         else
1708                                                 return new UnboxCast (source, target_type);
1709                                 }
1710
1711                                 return null;
1712                         }
1713
1714                         // From an array type S with an element type Se to an array type T with an
1715                         // element type Te provided all the following are true:
1716                         //     * S and T differe only in element type, in other words, S and T
1717                         //       have the same number of dimensions.
1718                         //     * Both Se and Te are reference types
1719                         //     * An explicit referenc conversions exist from Se to Te
1720                         //
1721                         if (source_type.IsArray && target_type.IsArray) {
1722                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1723
1724                                         Type source_element_type = TypeManager.GetElementType (source_type);
1725                                         Type target_element_type = TypeManager.GetElementType (target_type);
1726
1727                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1728                                                 if (ExplicitReferenceConversionExists (source_element_type,
1729                                                                                        target_element_type))
1730                                                         return new ClassCast (source, target_type);
1731                                 }
1732                         }
1733
1734
1735                         // From System.Array to any array-type
1736                         if (source_type == TypeManager.array_type &&
1737                             target_type.IsArray) {
1738                                 return new ClassCast (source, target_type);
1739                         }
1740
1741                         //
1742                         // From System delegate to any delegate-type
1743                         //
1744                         if (source_type == TypeManager.delegate_type &&
1745                             target_type.IsSubclassOf (TypeManager.delegate_type))
1746                                 return new ClassCast (source, target_type);
1747
1748                         //
1749                         // From ICloneable to Array or Delegate types
1750                         //
1751                         if (source_type == TypeManager.icloneable_type &&
1752                             (target_type == TypeManager.array_type ||
1753                              target_type == TypeManager.delegate_type))
1754                                 return new ClassCast (source, target_type);
1755
1756                         return null;
1757                 }
1758
1759                 /// <summary>
1760                 ///   Performs an explicit conversion of the expression `expr' whose
1761                 ///   type is expr.Type to `target_type'.
1762                 /// </summary>
1763                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1764                                                              Type target_type, Location loc)
1765                 {
1766                         Type expr_type = expr.Type;
1767                         Type original_expr_type = expr_type;
1768
1769                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1770                                 if (target_type == TypeManager.enum_type ||
1771                                     target_type == TypeManager.object_type) {
1772                                         if (expr is EnumConstant)
1773                                                 expr = ((EnumConstant) expr).Child;
1774                                         // We really need all these casts here .... :-(
1775                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1776                                         return new EmptyCast (expr, target_type);
1777                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1778                                            target_type.IsSubclassOf (TypeManager.enum_type))
1779                                         return new UnboxCast (expr, target_type);
1780
1781                                 //
1782                                 // Notice that we have kept the expr_type unmodified, which is only
1783                                 // used later on to
1784                                 if (expr is EnumConstant)
1785                                         expr = ((EnumConstant) expr).Child;
1786                                 else
1787                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1788                                 expr_type = expr.Type;
1789                         }
1790
1791                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1792
1793                         if (ne != null)
1794                                 return ne;
1795
1796                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1797                         if (ne != null)
1798                                 return ne;
1799
1800                         //
1801                         // Unboxing conversion.
1802                         //
1803                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1804                                 return new UnboxCast (expr, target_type);
1805
1806                         //
1807                         // Skip the ExplicitReferenceConversion because we can not convert
1808                         // from Null to a ValueType, and ExplicitReference wont check against
1809                         // null literal explicitly
1810                         //
1811                         if (expr_type != TypeManager.null_type){
1812                                 ne = ExplicitReferenceConversion (expr, target_type);
1813                                 if (ne != null)
1814                                         return ne;
1815                         }
1816
1817                         if (ec.InUnsafe){
1818                                 if (target_type.IsPointer){
1819                                         if (expr_type.IsPointer)
1820                                                 return new EmptyCast (expr, target_type);
1821
1822                                         if (expr_type == TypeManager.sbyte_type ||
1823                                             expr_type == TypeManager.short_type ||
1824                                             expr_type == TypeManager.int32_type ||
1825                                             expr_type == TypeManager.int64_type)
1826                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
1827
1828                                         if (expr_type == TypeManager.ushort_type ||
1829                                             expr_type == TypeManager.uint32_type ||
1830                                             expr_type == TypeManager.uint64_type ||
1831                                             expr_type == TypeManager.byte_type)
1832                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1833                                 }
1834                                 if (expr_type.IsPointer){
1835                                         Expression e = null;
1836
1837                                         if (target_type == TypeManager.sbyte_type)
1838                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1839                                         else if (target_type == TypeManager.byte_type)
1840                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1841                                         else if (target_type == TypeManager.short_type)
1842                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1843                                         else if (target_type == TypeManager.ushort_type)
1844                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1845                                         else if (target_type == TypeManager.int32_type)
1846                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1847                                         else if (target_type == TypeManager.uint32_type)
1848                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1849                                         else if (target_type == TypeManager.uint64_type)
1850                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1851                                         else if (target_type == TypeManager.int64_type){
1852                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1853                                         }
1854
1855                                         if (e != null){
1856                                                 Expression ci, ce;
1857
1858                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1859
1860                                                 if (ci != null)
1861                                                         return ci;
1862
1863                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1864                                                 if (ce != null)
1865                                                         return ce;
1866                                                 //
1867                                                 // We should always be able to go from an uint32
1868                                                 // implicitly or explicitly to the other integral
1869                                                 // types
1870                                                 //
1871                                                 throw new Exception ("Internal compiler error");
1872                                         }
1873                                 }
1874                         }
1875
1876                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1877                         if (ne != null)
1878                                 return ne;
1879
1880                         if (expr is NullLiteral){
1881                                 Report.Error (37, loc, "Cannot convert null to `{0}' because it is a value type",
1882                                               TypeManager.CSharpName (target_type));
1883                                 return null;
1884                         }
1885
1886                         Error_CannotConvertType (loc, original_expr_type, target_type);
1887                         return null;
1888                 }
1889
1890                 /// <summary>
1891                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1892                 /// </summary>
1893                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1894                                                                   Type target_type, Location l)
1895                 {
1896                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1897
1898                         if (ne != null)
1899                                 return ne;
1900
1901                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1902                         if (ne != null)
1903                                 return ne;
1904
1905                         ne = ExplicitReferenceConversion (expr, target_type);
1906                         if (ne != null)
1907                                 return ne;
1908
1909                         Error_CannotConvertType (l, expr.Type, target_type);
1910                         return null;
1911                 }
1912         }
1913 }