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, target_type);
  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, target_type);
  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, target_type);
  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                 static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 180                 {
 181                         if (target_type.IsValueType)
 182                                 return false;
 183
 184                         Type expr_type = expr.Type;
 185
 186                         //
 187                         // This is the boxed case.
 188                         //
 189                         if (target_type == TypeManager.object_type) {
 190                                 if (expr_type.IsClass || expr_type.IsValueType ||
 191                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 192                                         if (target_type != TypeManager.anonymous_method_type)
 193                                                 return true;
 194
 195                                 return false;
 196                         } else if (expr_type.IsSubclassOf (target_type))
 197                                 return true;
 198
 199                         // Please remember that all code below actually comes
 200                         // from ImplicitReferenceConversion so make sure code remains in sync
 201
 202                         // from any class-type S to any interface-type T.
 203                         if (target_type.IsInterface) {
 204                                 if (target_type != TypeManager.iconvertible_type &&
 205                                     expr_type.IsValueType && (expr is Constant) &&
 206                                     !(expr is IntLiteral || expr is BoolLiteral ||
 207                                       expr is FloatLiteral || expr is DoubleLiteral ||
 208                                       expr is LongLiteral || expr is CharLiteral ||
 209                                       expr is StringLiteral || expr is DecimalLiteral ||
 210                                       expr is UIntLiteral || expr is ULongLiteral)) {
 211                                         return false;
 212                                 }
 213
 214                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 215                                         return true;
 216                         }
 217
 218                         // from any interface type S to interface-type T.
 219                         if (expr_type.IsInterface && target_type.IsInterface)
 220                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 221                                         return true;
 222
 223                         // from an array-type S to an array-type of type T
 224                         if (expr_type.IsArray && target_type.IsArray) {
 225                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 226
 227                                         Type expr_element_type = expr_type.GetElementType ();
 228
 229                                         if (MyEmptyExpr == null)
 230                                                 MyEmptyExpr = new EmptyExpression ();
 231
 232                                         MyEmptyExpr.SetType (expr_element_type);
 233                                         Type target_element_type = TypeManager.GetElementType (target_type);
 234
 235                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 236                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 237                                                                                       target_element_type))
 238                                                         return true;
 239                                 }
 240                         }
 241
 242                         // from an array-type to System.Array
 243                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 244                                 return true;
 245
 246                         // from any delegate type to System.Delegate
 247                         if ((expr_type == TypeManager.delegate_type ||
 248                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 249                             target_type == TypeManager.delegate_type)
 250                                 if (target_type.IsAssignableFrom (expr_type))
 251                                         return true;
 252
 253                         // from any array-type or delegate type into System.ICloneable.
 254                         if (expr_type.IsArray ||
 255                             expr_type == TypeManager.delegate_type ||
 256                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 257                                 if (target_type == TypeManager.icloneable_type)
 258                                         return true;
 259
 260                         // from the null type to any reference-type.
 261                         if (expr_type == TypeManager.null_type){
 262                                 if (target_type.IsPointer)
 263                                         return true;
 264
 265                                 if (!target_type.IsValueType)
 266                                         return true;
 267                         }
 268                         return false;
 269                 }
 270
 271                 /// <summary>
 272                 ///   Implicit Numeric Conversions.
 273                 ///
 274                 ///   expr is the expression to convert, returns a new expression of type
 275                 ///   target_type or null if an implicit conversion is not possible.
 276                 /// </summary>
 277                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 278                                                                     Type target_type, Location loc)
 279                 {
 280                         Type expr_type = expr.Type;
 281
 282                         //
 283                         // Attempt to do the implicit constant expression conversions
 284
 285                         if (expr is Constant){
 286                                 if (expr is IntConstant){
 287                                         Expression e;
 288
 289                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 290
 291                                         if (e != null)
 292                                                 return e;
 293                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 294                                         //
 295                                         // Try the implicit constant expression conversion
 296                                         // from long to ulong, instead of a nice routine,
 297                                         // we just inline it
 298                                         //
 299                                         long v = ((LongConstant) expr).Value;
 300                                         if (v >= 0)
 301                                                 return new ULongConstant ((ulong) v, expr.Location);
 302                                 }
 303                         }
 304
 305                         Type real_target_type = target_type;
 306
 307                         if (expr_type == TypeManager.sbyte_type){
 308                                 //
 309                                 // From sbyte to short, int, long, float, double, decimal
 310                                 //
 311                                 if (real_target_type == TypeManager.int32_type)
 312                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 313                                 if (real_target_type == TypeManager.int64_type)
 314                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 315                                 if (real_target_type == TypeManager.double_type)
 316                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 317                                 if (real_target_type == TypeManager.float_type)
 318                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 319                                 if (real_target_type == TypeManager.short_type)
 320                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 321                                 if (real_target_type == TypeManager.decimal_type)
 322                                         return new CastToDecimal (ec, expr);
 323                         } else if (expr_type == TypeManager.byte_type){
 324                                 //
 325                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 326                                 //
 327                                 if ((real_target_type == TypeManager.short_type) ||
 328                                     (real_target_type == TypeManager.ushort_type) ||
 329                                     (real_target_type == TypeManager.int32_type) ||
 330                                     (real_target_type == TypeManager.uint32_type))
 331                                         return new EmptyCast (expr, target_type);
 332
 333                                 if (real_target_type == TypeManager.uint64_type)
 334                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 335                                 if (real_target_type == TypeManager.int64_type)
 336                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 337                                 if (real_target_type == TypeManager.float_type)
 338                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 339                                 if (real_target_type == TypeManager.double_type)
 340                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 341                                 if (real_target_type == TypeManager.decimal_type)
 342                                         return new CastToDecimal (ec, expr);
 343
 344                         } else if (expr_type == TypeManager.short_type){
 345                                 //
 346                                 // From short to int, long, float, double, decimal
 347                                 //
 348                                 if (real_target_type == TypeManager.int32_type)
 349                                         return new EmptyCast (expr, target_type);
 350                                 if (real_target_type == TypeManager.int64_type)
 351                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 352                                 if (real_target_type == TypeManager.double_type)
 353                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 354                                 if (real_target_type == TypeManager.float_type)
 355                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 356                                 if (real_target_type == TypeManager.decimal_type)
 357                                         return new CastToDecimal (ec, expr);
 358
 359                         } else if (expr_type == TypeManager.ushort_type){
 360                                 //
 361                                 // From ushort to int, uint, long, ulong, float, double, decimal
 362                                 //
 363                                 if (real_target_type == TypeManager.uint32_type)
 364                                         return new EmptyCast (expr, target_type);
 365
 366                                 if (real_target_type == TypeManager.uint64_type)
 367                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 368                                 if (real_target_type == TypeManager.int32_type)
 369                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 370                                 if (real_target_type == TypeManager.int64_type)
 371                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 372                                 if (real_target_type == TypeManager.double_type)
 373                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 374                                 if (real_target_type == TypeManager.float_type)
 375                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 376                                 if (real_target_type == TypeManager.decimal_type)
 377                                         return new CastToDecimal (ec, expr);
 378                         } else if (expr_type == TypeManager.int32_type){
 379                                 //
 380                                 // From int to long, float, double, decimal
 381                                 //
 382                                 if (real_target_type == TypeManager.int64_type)
 383                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 384                                 if (real_target_type == TypeManager.double_type)
 385                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 386                                 if (real_target_type == TypeManager.float_type)
 387                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 388                                 if (real_target_type == TypeManager.decimal_type)
 389                                         return new CastToDecimal (ec, expr);
 390                         } else if (expr_type == TypeManager.uint32_type){
 391                                 //
 392                                 // From uint to long, ulong, float, double, decimal
 393                                 //
 394                                 if (real_target_type == TypeManager.int64_type)
 395                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 396                                 if (real_target_type == TypeManager.uint64_type)
 397                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 398                                 if (real_target_type == TypeManager.double_type)
 399                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 400                                                                OpCodes.Conv_R8);
 401                                 if (real_target_type == TypeManager.float_type)
 402                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 403                                                                OpCodes.Conv_R4);
 404                                 if (real_target_type == TypeManager.decimal_type)
 405                                         return new CastToDecimal (ec, expr);
 406                         } else if (expr_type == TypeManager.int64_type){
 407                                 //
 408                                 // From long/ulong to float, double
 409                                 //
 410                                 if (real_target_type == TypeManager.double_type)
 411                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 412                                 if (real_target_type == TypeManager.float_type)
 413                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 414                                 if (real_target_type == TypeManager.decimal_type)
 415                                         return new CastToDecimal (ec, expr);
 416                         } else if (expr_type == TypeManager.uint64_type){
 417                                 //
 418                                 // From ulong to float, double
 419                                 //
 420                                 if (real_target_type == TypeManager.double_type)
 421                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 422                                                                OpCodes.Conv_R8);
 423                                 if (real_target_type == TypeManager.float_type)
 424                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 425                                                                OpCodes.Conv_R4);
 426                                 if (real_target_type == TypeManager.decimal_type)
 427                                         return new CastToDecimal (ec, expr);
 428                         } else if (expr_type == TypeManager.char_type){
 429                                 //
 430                                 // From char to ushort, int, uint, long, ulong, float, double, decimal
 431                                 //
 432                                 if ((real_target_type == TypeManager.ushort_type) ||
 433                                     (real_target_type == TypeManager.int32_type) ||
 434                                     (real_target_type == TypeManager.uint32_type))
 435                                         return new EmptyCast (expr, target_type);
 436                                 if (real_target_type == TypeManager.uint64_type)
 437                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 438                                 if (real_target_type == TypeManager.int64_type)
 439                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 440                                 if (real_target_type == TypeManager.float_type)
 441                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 442                                 if (real_target_type == TypeManager.double_type)
 443                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 444                                 if (real_target_type == TypeManager.decimal_type)
 445                                         return new CastToDecimal (ec, expr);
 446                         } else if (expr_type == TypeManager.float_type){
 447                                 //
 448                                 // float to double
 449                                 //
 450                                 if (real_target_type == TypeManager.double_type)
 451                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 452                         }
 453
 454                         return null;
 455                 }
 456
 457
 458                 /// <summary>
 459                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 460                 ///  implicit user defined conversions - needed for overload resolution
 461                 /// </summary>
 462                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 463                 {
 464                         if (ImplicitStandardConversionExists (ec, expr, target_type))
 465                                 return true;
 466
 467                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 468
 469                         if (dummy != null)
 470                                 return true;
 471
 472                         return false;
 473                 }
 474
 475                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 476                 {
 477                         Expression dummy = ImplicitUserConversion (
 478                                 ec, new EmptyExpression (source), target, Location.Null);
 479                         return dummy != null;
 480                 }
 481
 482                 /// <summary>
 483                 ///  Determines if a standard implicit conversion exists from
 484                 ///  expr_type to target_type
 485                 ///
 486                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 487                 /// </summary>
 488                 public static bool ImplicitStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 489                 {
 490                         Type expr_type = expr.Type;
 491
 492                         if (expr_type == TypeManager.void_type)
 493                                 return false;
 494
 495                         if (expr_type == target_type)
 496                                 return true;
 497
 498
 499                         // First numeric conversions
 500
 501                         if (expr_type == TypeManager.sbyte_type){
 502                                 //
 503                                 // From sbyte to short, int, long, float, double, decimal
 504                                 //
 505                                 if ((target_type == TypeManager.int32_type) ||
 506                                     (target_type == TypeManager.int64_type) ||
 507                                     (target_type == TypeManager.double_type) ||
 508                                     (target_type == TypeManager.float_type)  ||
 509                                     (target_type == TypeManager.short_type) ||
 510                                     (target_type == TypeManager.decimal_type))
 511                                         return true;
 512
 513                         } else if (expr_type == TypeManager.byte_type){
 514                                 //
 515                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 516                                 //
 517                                 if ((target_type == TypeManager.short_type) ||
 518                                     (target_type == TypeManager.ushort_type) ||
 519                                     (target_type == TypeManager.int32_type) ||
 520                                     (target_type == TypeManager.uint32_type) ||
 521                                     (target_type == TypeManager.uint64_type) ||
 522                                     (target_type == TypeManager.int64_type) ||
 523                                     (target_type == TypeManager.float_type) ||
 524                                     (target_type == TypeManager.double_type) ||
 525                                     (target_type == TypeManager.decimal_type))
 526                                         return true;
 527
 528                         } else if (expr_type == TypeManager.short_type){
 529                                 //
 530                                 // From short to int, long, double, float, decimal
 531                                 //
 532                                 if ((target_type == TypeManager.int32_type) ||
 533                                     (target_type == TypeManager.int64_type) ||
 534                                     (target_type == TypeManager.double_type) ||
 535                                     (target_type == TypeManager.float_type) ||
 536                                     (target_type == TypeManager.decimal_type))
 537                                         return true;
 538
 539                         } else if (expr_type == TypeManager.ushort_type){
 540                                 //
 541                                 // From ushort to int, uint, long, ulong, double, float, decimal
 542                                 //
 543                                 if ((target_type == TypeManager.uint32_type) ||
 544                                     (target_type == TypeManager.uint64_type) ||
 545                                     (target_type == TypeManager.int32_type) ||
 546                                     (target_type == TypeManager.int64_type) ||
 547                                     (target_type == TypeManager.double_type) ||
 548                                     (target_type == TypeManager.float_type) ||
 549                                     (target_type == TypeManager.decimal_type))
 550                                         return true;
 551
 552                         } else if (expr_type == TypeManager.int32_type){
 553                                 //
 554                                 // From int to long, double, float, decimal
 555                                 //
 556                                 if ((target_type == TypeManager.int64_type) ||
 557                                     (target_type == TypeManager.double_type) ||
 558                                     (target_type == TypeManager.float_type) ||
 559                                     (target_type == TypeManager.decimal_type))
 560                                         return true;
 561
 562                         } else if (expr_type == TypeManager.uint32_type){
 563                                 //
 564                                 // From uint to long, ulong, double, float, decimal
 565                                 //
 566                                 if ((target_type == TypeManager.int64_type) ||
 567                                     (target_type == TypeManager.uint64_type) ||
 568                                     (target_type == TypeManager.double_type) ||
 569                                     (target_type == TypeManager.float_type) ||
 570                                     (target_type == TypeManager.decimal_type))
 571                                         return true;
 572
 573                         } else if ((expr_type == TypeManager.uint64_type) ||
 574                                    (expr_type == TypeManager.int64_type)) {
 575                                 //
 576                                 // From long/ulong to double, float, decimal
 577                                 //
 578                                 if ((target_type == TypeManager.double_type) ||
 579                                     (target_type == TypeManager.float_type) ||
 580                                     (target_type == TypeManager.decimal_type))
 581                                         return true;
 582
 583                         } else if (expr_type == TypeManager.char_type){
 584                                 //
 585                                 // From char to ushort, int, uint, ulong, long, float, double, decimal
 586                                 //
 587                                 if ((target_type == TypeManager.ushort_type) ||
 588                                     (target_type == TypeManager.int32_type) ||
 589                                     (target_type == TypeManager.uint32_type) ||
 590                                     (target_type == TypeManager.uint64_type) ||
 591                                     (target_type == TypeManager.int64_type) ||
 592                                     (target_type == TypeManager.float_type) ||
 593                                     (target_type == TypeManager.double_type) ||
 594                                     (target_type == TypeManager.decimal_type))
 595                                         return true;
 596
 597                         } else if (expr_type == TypeManager.float_type){
 598                                 //
 599                                 // float to double
 600                                 //
 601                                 if (target_type == TypeManager.double_type)
 602                                         return true;
 603                         }
 604
 605                         if (expr.eclass == ExprClass.MethodGroup){
 606                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 607                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 608                                         if (mg != null){
 609                                                 //
 610                                                 // This should not happen frequently, so we can create an object
 611                                                 // to test compatibility
 612                                                 //
 613                                                 Expression c = ImplicitDelegateCreation.Create (
 614                                                         ec, mg, target_type, true, Location.Null);
 615                                                 return c != null;
 616                                         }
 617                                 }
 618                         }
 619
 620                         if (ImplicitReferenceConversionExists (expr, target_type))
 621                                 return true;
 622
 623                         //
 624                         // Implicit Constant Expression Conversions
 625                         //
 626                         if (expr is IntConstant){
 627                                 int value = ((IntConstant) expr).Value;
 628
 629                                 if (target_type == TypeManager.sbyte_type){
 630                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 631                                                 return true;
 632                                 } else if (target_type == TypeManager.byte_type){
 633                                         if (value >= 0 && value <= Byte.MaxValue)
 634                                                 return true;
 635                                 } else if (target_type == TypeManager.short_type){
 636                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 637                                                 return true;
 638                                 } else if (target_type == TypeManager.ushort_type){
 639                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 640                                                 return true;
 641                                 } else if (target_type == TypeManager.uint32_type){
 642                                         if (value >= 0)
 643                                                 return true;
 644                                 } else if (target_type == TypeManager.uint64_type){
 645                                          //
 646                                          // we can optimize this case: a positive int32
 647                                          // always fits on a uint64.  But we need an opcode
 648                                          // to do it.
 649                                          //
 650                                         if (value >= 0)
 651                                                 return true;
 652                                 }
 653
 654                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 655                                         return true;
 656                         }
 657
 658                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 659                                 //
 660                                 // Try the implicit constant expression conversion
 661                                 // from long to ulong, instead of a nice routine,
 662                                 // we just inline it
 663                                 //
 664                                 long v = ((LongConstant) expr).Value;
 665                                 if (v >= 0)
 666                                         return true;
 667                         }
 668
 669                         if ((target_type == TypeManager.enum_type ||
 670                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 671                              expr is IntLiteral){
 672                                 IntLiteral i = (IntLiteral) expr;
 673
 674                                 if (i.Value == 0)
 675                                         return true;
 676                         }
 677
 678                         //
 679                         // If `expr_type' implements `target_type' (which is an iface)
 680                         // see TryImplicitIntConversion
 681                         //
 682                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 683                                 return true;
 684
 685                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 686                                 return true;
 687
 688                         if (expr_type == TypeManager.anonymous_method_type){
 689                                 if (!TypeManager.IsDelegateType (target_type))
 690                                         return false;
 691
 692                                 AnonymousMethod am = (AnonymousMethod) expr;
 693
 694                                 Expression conv = am.Compatible (ec, target_type, true);
 695                                 if (conv != null)
 696                                         return true;
 697                         }
 698
 699                         return false;
 700                 }
 701
 702                 /// <summary>
 703                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 704                 ///  amongst the methods in the MethodGroupExpr
 705                 /// </summary>
 706                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 707                 {
 708                         Type best = null;
 709
 710                         if (types.Count == 0)
 711                                 return null;
 712
 713                         if (types.Count == 1)
 714                                 return (Type) types [0];
 715
 716                         EmptyExpression expr = EmptyExpression.Grab ();
 717
 718                         foreach (Type t in types) {
 719                                 if (best == null) {
 720                                         best = t;
 721                                         continue;
 722                                 }
 723
 724                                 expr.SetType (t);
 725                                 if (ImplicitStandardConversionExists (ec, expr, best))
 726                                         best = t;
 727                         }
 728
 729                         expr.SetType (best);
 730                         foreach (Type t in types) {
 731                                 if (best == t)
 732                                         continue;
 733                                 if (!ImplicitStandardConversionExists (ec, expr, t)) {
 734                                         best = null;
 735                                         break;
 736                                 }
 737                         }
 738
 739                         EmptyExpression.Release (expr);
 740
 741                         return best;
 742                 }
 743
 744                 /// <summary>
 745                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 746                 ///  amongst the types in the given set
 747                 /// </summary>
 748                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 749                 {
 750                         Type best = null;
 751
 752                         if (types.Count == 0)
 753                                 return null;
 754
 755                         if (types.Count == 1)
 756                                 return (Type) types [0];
 757
 758                         EmptyExpression expr = EmptyExpression.Grab ();
 759
 760                         foreach (Type t in types) {
 761                                 if (best == null) {
 762                                         best = t;
 763                                         continue;
 764                                 }
 765
 766                                 expr.SetType (best);
 767                                 if (ImplicitStandardConversionExists (ec, expr, t))
 768                                         best = t;
 769                         }
 770
 771                         foreach (Type t in types) {
 772                                 if (best == t)
 773                                         continue;
 774                                 expr.SetType (t);
 775                                 if (!ImplicitStandardConversionExists (ec, expr, best)) {
 776                                         best = null;
 777                                         break;
 778                                 }
 779                         }
 780
 781                         EmptyExpression.Release (expr);
 782
 783                         return best;
 784                 }
 785
 786                 /// <summary>
 787                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 788                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 789                 ///   for explicit and implicit conversion operators.
 790                 /// </summary>
 791                 static public Type FindMostSpecificSource (EmitContext ec, IList list,
 792                                                            Expression source, bool apply_explicit_conv_rules,
 793                                                            Location loc)
 794                 {
 795                         ArrayList src_types_set = new ArrayList ();
 796
 797                         //
 798                         // If any operator converts from S then Sx = S
 799                         //
 800                         Type source_type = source.Type;
 801                         foreach (MethodBase mb in list){
 802                                 ParameterData pd = TypeManager.GetParameterData (mb);
 803                                 Type param_type = pd.ParameterType (0);
 804
 805                                 if (param_type == source_type)
 806                                         return param_type;
 807
 808                                 src_types_set.Add (param_type);
 809                         }
 810
 811                         //
 812                         // Explicit Conv rules
 813                         //
 814                         if (apply_explicit_conv_rules) {
 815                                 ArrayList candidate_set = new ArrayList ();
 816
 817                                 foreach (Type param_type in src_types_set){
 818                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 819                                                 candidate_set.Add (param_type);
 820                                 }
 821
 822                                 if (candidate_set.Count != 0)
 823                                         return FindMostEncompassedType (ec, candidate_set);
 824                         }
 825
 826                         //
 827                         // Final case
 828                         //
 829                         if (apply_explicit_conv_rules)
 830                                 return FindMostEncompassingType (ec, src_types_set);
 831                         else
 832                                 return FindMostEncompassedType (ec, src_types_set);
 833                 }
 834
 835                 /// <summary>
 836                 ///  Finds the most specific target Tx according to section 13.4.4
 837                 /// </summary>
 838                 static public Type FindMostSpecificTarget (EmitContext ec, IList list,
 839                                                            Type target, bool apply_explicit_conv_rules,
 840                                                            Location loc)
 841                 {
 842                         ArrayList tgt_types_set = new ArrayList ();
 843
 844                         //
 845                         // If any operator converts to T then Tx = T
 846                         //
 847                         foreach (MethodInfo mi in list){
 848                                 Type ret_type = mi.ReturnType;
 849                                 if (ret_type == target)
 850                                         return ret_type;
 851
 852                                 tgt_types_set.Add (ret_type);
 853                         }
 854
 855                         //
 856                         // Explicit conv rules
 857                         //
 858                         if (apply_explicit_conv_rules) {
 859                                 ArrayList candidate_set = new ArrayList ();
 860
 861                                 EmptyExpression expr = EmptyExpression.Grab ();
 862
 863                                 foreach (Type ret_type in tgt_types_set){
 864                                         expr.SetType (ret_type);
 865
 866                                         if (ImplicitStandardConversionExists (ec, expr, target))
 867                                                 candidate_set.Add (ret_type);
 868                                 }
 869
 870                                 EmptyExpression.Release (expr);
 871
 872                                 if (candidate_set.Count != 0)
 873                                         return FindMostEncompassingType (ec, candidate_set);
 874                         }
 875
 876                         //
 877                         // Okay, final case !
 878                         //
 879                         if (apply_explicit_conv_rules)
 880                                 return FindMostEncompassedType (ec, tgt_types_set);
 881                         else
 882                                 return FindMostEncompassingType (ec, tgt_types_set);
 883                 }
 884
 885                 /// <summary>
 886                 ///  User-defined Implicit conversions
 887                 /// </summary>
 888                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 889                                                                  Type target, Location loc)
 890                 {
 891                         return UserDefinedConversion (ec, source, target, loc, false);
 892                 }
 893
 894                 /// <summary>
 895                 ///  User-defined Explicit conversions
 896                 /// </summary>
 897                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 898                                                                  Type target, Location loc)
 899                 {
 900                         return UserDefinedConversion (ec, source, target, loc, true);
 901                 }
 902
 903                 static void AddConversionOperators (EmitContext ec, ArrayList list,
 904                                                     Expression source, Type target_type,
 905                                                     bool look_for_explicit,
 906                                                     MethodGroupExpr mg)
 907                 {
 908                         if (mg == null)
 909                                 return;
 910
 911                         Type source_type = source.Type;
 912                         EmptyExpression expr = EmptyExpression.Grab ();
 913                         foreach (MethodInfo m in mg.Methods) {
 914                                 ParameterData pd = TypeManager.GetParameterData (m);
 915                                 Type return_type = m.ReturnType;
 916                                 Type arg_type = pd.ParameterType (0);
 917
 918                                 if (source_type != arg_type) {
 919                                         if (!ImplicitStandardConversionExists (ec, source, arg_type)) {
 920                                                 if (!look_for_explicit)
 921                                                         continue;
 922                                                 expr.SetType (arg_type);
 923                                                 if (!ImplicitStandardConversionExists (ec, expr, source_type))
 924                                                         continue;
 925                                         }
 926                                 }
 927
 928                                 if (target_type != return_type) {
 929                                         expr.SetType (return_type);
 930                                         if (!ImplicitStandardConversionExists (ec, expr, target_type)) {
 931                                                 if (!look_for_explicit)
 932                                                         continue;
 933                                                 expr.SetType (target_type);
 934                                                 if (!ImplicitStandardConversionExists (ec, expr, return_type))
 935                                                         continue;
 936                                         }
 937                                 }
 938
 939                                 list.Add (m);
 940                         }
 941
 942                         EmptyExpression.Release (expr);
 943                 }
 944
 945                 /// <summary>
 946                 ///   Computes the list of the user-defined conversion
 947                 ///   operators from source_type to target_type.  `look_for_explicit'
 948                 ///   controls whether we should also include the list of explicit
 949                 ///   operators
 950                 /// </summary>
 951                 static IList GetConversionOperators (EmitContext ec,
 952                                                      Expression source, Type target_type,
 953                                                      Location loc, bool look_for_explicit)
 954                 {
 955                         ArrayList ret = new ArrayList (4);
 956
 957                         Type source_type = source.Type;
 958
 959                         if (source_type != TypeManager.decimal_type) {
 960                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 961                                         Expression.MethodLookup (
 962                                                 ec, source_type, "op_Implicit", loc) as MethodGroupExpr);
 963                                 if (look_for_explicit) {
 964                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 965                                                 Expression.MethodLookup (
 966                                                         ec, source_type, "op_Explicit", loc) as MethodGroupExpr);
 967                                 }
 968                         }
 969
 970                         if (target_type != TypeManager.decimal_type) {
 971                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 972                                         Expression.MethodLookup (
 973                                                 ec, target_type, "op_Implicit", loc) as MethodGroupExpr);
 974                                 if (look_for_explicit) {
 975                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 976                                                 Expression.MethodLookup (
 977                                                         ec, target_type, "op_Explicit", loc) as MethodGroupExpr);
 978                                 }
 979                         }
 980
 981                         return ret;
 982                 }
 983
 984                 static DoubleHash explicit_conv = new DoubleHash (100);
 985                 static DoubleHash implicit_conv = new DoubleHash (100);
 986
 987                 /// <summary>
 988                 ///   User-defined conversions
 989                 /// </summary>
 990                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 991                                                                 Type target, Location loc,
 992                                                                 bool look_for_explicit)
 993                 {
 994                         Type source_type = source.Type;
 995                         MethodInfo method = null;
 996                         Type most_specific_source = null;
 997                         Type most_specific_target = null;
 998
 999                         object o;
1000                         DoubleHash hash = look_for_explicit ? explicit_conv : implicit_conv;
1001
1002                         if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
1003                                 method = (MethodInfo) o;
1004                                 if (method != null) {
1005                                         ParameterData pd = TypeManager.GetParameterData (method);
1006                                         most_specific_source = pd.ParameterType (0);
1007                                         most_specific_target = method.ReturnType;
1008                                 }
1009                         } else {
1010                                 IList ops = GetConversionOperators (ec, source, target, loc, look_for_explicit);
1011                                 if (ops == null || ops.Count == 0) {
1012                                         method = null;
1013                                         goto skip;
1014                                 }
1015
1016                                 most_specific_source = FindMostSpecificSource (ec, ops, source, look_for_explicit, loc);
1017                                 if (most_specific_source == null) {
1018                                         method = null;
1019                                         goto skip;
1020                                 }
1021
1022                                 most_specific_target = FindMostSpecificTarget (ec, ops, target, look_for_explicit, loc);
1023                                 if (most_specific_target == null) {
1024                                         method = null;
1025                                         goto skip;
1026                                 }
1027
1028                                 int count = 0;
1029
1030                                 foreach (MethodInfo m in ops) {
1031                                         ParameterData pd = TypeManager.GetParameterData (m);
1032
1033                                         if (pd.ParameterType (0) == most_specific_source &&
1034                                             m.ReturnType == most_specific_target) {
1035                                                 method = m;
1036                                                 count++;
1037                                         }
1038                                 }
1039                                 if (count > 1)
1040                                         method = null;
1041
1042                         skip:
1043                                 if (!(source is Constant))
1044                                         hash.Insert (source_type, target, method);
1045                         }
1046
1047                         if (method == null)
1048                                 return null;
1049
1050                         //
1051                         // This will do the conversion to the best match that we
1052                         // found.  Now we need to perform an implict standard conversion
1053                         // if the best match was not the type that we were requested
1054                         // by target.
1055                         //
1056                         if (look_for_explicit)
1057                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1058                         else
1059                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1060
1061                         if (source == null)
1062                                 return null;
1063
1064                         Expression e;
1065                         e =  new UserCast (method, source, loc);
1066                         if (e.Type != target){
1067                                 if (!look_for_explicit)
1068                                         e = ImplicitConversionStandard (ec, e, target, loc);
1069                                 else
1070                                         e = ExplicitConversionStandard (ec, e, target, loc);
1071                         }
1072
1073                         return e;
1074                 }
1075
1076                 /// <summary>
1077                 ///   Converts implicitly the resolved expression `expr' into the
1078                 ///   `target_type'.  It returns a new expression that can be used
1079                 ///   in a context that expects a `target_type'.
1080                 /// </summary>
1081                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1082                                                              Type target_type, Location loc)
1083                 {
1084                         Expression e;
1085
1086                         if (target_type == null)
1087                                 throw new Exception ("Target type is null");
1088
1089                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1090                         if (e != null)
1091                                 return e;
1092
1093                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1094                         if (e != null)
1095                                 return e;
1096
1097                         return null;
1098                 }
1099
1100
1101                 /// <summary>
1102                 ///   Attempts to apply the `Standard Implicit
1103                 ///   Conversion' rules to the expression `expr' into
1104                 ///   the `target_type'.  It returns a new expression
1105                 ///   that can be used in a context that expects a
1106                 ///   `target_type'.
1107                 ///
1108                 ///   This is different from `ImplicitConversion' in that the
1109                 ///   user defined implicit conversions are excluded.
1110                 /// </summary>
1111                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1112                                                                      Type target_type, Location loc)
1113                 {
1114                         Type expr_type = expr.Type;
1115                         Expression e;
1116
1117                         if (expr.eclass == ExprClass.MethodGroup){
1118                                 if (!TypeManager.IsDelegateType (target_type)){
1119                                         return null;
1120                                 }
1121
1122                                 //
1123                                 // Only allow anonymous method conversions on post ISO_1
1124                                 //
1125                                 if (RootContext.Version != LanguageVersion.ISO_1){
1126                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1127                                         if (mg != null)
1128                                                 return ImplicitDelegateCreation.Create (
1129                                                         ec, mg, target_type, false, loc);
1130                                 }
1131                         }
1132
1133                         if (expr_type == target_type && expr_type != TypeManager.null_type)
1134                                 return expr;
1135
1136                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1137                         if (e != null)
1138                                 return e;
1139
1140                         e = ImplicitReferenceConversion (expr, target_type);
1141                         if (e != null)
1142                                 return e;
1143
1144                         if ((target_type == TypeManager.enum_type ||
1145                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1146                             expr is IntLiteral){
1147                                 IntLiteral i = (IntLiteral) expr;
1148
1149                                 if (i.Value == 0)
1150                                         return new EnumConstant ((Constant) expr, target_type);
1151                         }
1152
1153                         if (ec.InUnsafe) {
1154                                 if (expr_type.IsPointer){
1155                                         if (target_type == TypeManager.void_ptr_type)
1156                                                 return new EmptyCast (expr, target_type);
1157
1158                                         //
1159                                         // yep, comparing pointer types cant be done with
1160                                         // t1 == t2, we have to compare their element types.
1161                                         //
1162                                         if (target_type.IsPointer){
1163                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1164                                                         return expr;
1165                                         }
1166                                 }
1167
1168                                 if (target_type.IsPointer) {
1169                                         if (expr_type == TypeManager.null_type)
1170                                                 return new EmptyCast (NullPointer.Null, target_type);
1171
1172                                         if (expr_type == TypeManager.void_ptr_type)
1173                                                 return new EmptyCast (expr, target_type);
1174                                 }
1175                         }
1176
1177                         if (expr_type == TypeManager.anonymous_method_type){
1178                                 if (!TypeManager.IsDelegateType (target_type)){
1179                                         Report.Error (1660, loc,
1180                                                 "Cannot convert anonymous method block to type `{0}' because it is not a delegate type",
1181                                                 TypeManager.CSharpName (target_type));
1182                                         return null;
1183                                 }
1184
1185                                 AnonymousMethod am = (AnonymousMethod) expr;
1186                                 int errors = Report.Errors;
1187
1188                                 Expression conv = am.Compatible (ec, target_type, false);
1189                                 if (conv != null)
1190                                         return conv;
1191
1192                                 //
1193                                 // We return something instead of null, to avoid
1194                                 // the duplicate error, since am.Compatible would have
1195                                 // reported that already
1196                                 //
1197                                 if (errors != Report.Errors)
1198                                         return new EmptyCast (expr, target_type);
1199                         }
1200
1201                         return null;
1202                 }
1203
1204                 /// <summary>
1205                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1206                 ///   into a different data type using casts (See Implicit Constant
1207                 ///   Expression Conversions)
1208                 /// </summary>
1209                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1210                 {
1211                         int value = ic.Value;
1212
1213                         if (target_type == TypeManager.sbyte_type){
1214                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1215                                         return new SByteConstant ((sbyte) value, ic.Location);
1216                         } else if (target_type == TypeManager.byte_type){
1217                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1218                                         return new ByteConstant ((byte) value, ic.Location);
1219                         } else if (target_type == TypeManager.short_type){
1220                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1221                                         return new ShortConstant ((short) value, ic.Location);
1222                         } else if (target_type == TypeManager.ushort_type){
1223                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1224                                         return new UShortConstant ((ushort) value, ic.Location);
1225                         } else if (target_type == TypeManager.uint32_type){
1226                                 if (value >= 0)
1227                                         return new UIntConstant ((uint) value, ic.Location);
1228                         } else if (target_type == TypeManager.uint64_type){
1229                                 //
1230                                 // we can optimize this case: a positive int32
1231                                 // always fits on a uint64.  But we need an opcode
1232                                 // to do it.
1233                                 //
1234                                 if (value >= 0)
1235                                         return new ULongConstant ((ulong) value, ic.Location);
1236                         } else if (target_type == TypeManager.double_type)
1237                                 return new DoubleConstant ((double) value, ic.Location);
1238                         else if (target_type == TypeManager.float_type)
1239                                 return new FloatConstant ((float) value, ic.Location);
1240
1241                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1242                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1243                                 Constant e = (Constant) ic;
1244
1245                                 //
1246                                 // Possibly, we need to create a different 0 literal before passing
1247                                 // to EnumConstant
1248                                 //
1249                                 if (underlying == TypeManager.int64_type)
1250                                         e = new LongLiteral (0, ic.Location);
1251                                 else if (underlying == TypeManager.uint64_type)
1252                                         e = new ULongLiteral (0, ic.Location);
1253
1254                                 return new EnumConstant (e, target_type);
1255                         }
1256
1257                         //
1258                         // If `target_type' is an interface and the type of `ic' implements the interface
1259                         // e.g. target_type is IComparable, IConvertible, IFormattable
1260                         //
1261                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1262                                 return new BoxedCast (ic, target_type);
1263
1264                         return null;
1265                 }
1266
1267                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1268                 {
1269                         if (source.Name == target.Name){
1270                                 Report.ExtraInformation (loc,
1271                                          String.Format (
1272                                                 "The type {0} has two conflicting definitions, one comes from {1} and the other from {2}",
1273                                                 source.Name, source.Assembly.FullName, target.Assembly.FullName));
1274
1275                         }
1276
1277                         // TODO: Missing explicit numeric check
1278                         //ExplicitNumericConversion
1279
1280                         if (ExplicitReferenceConversionExists (source, target)) {
1281                                 Report.Error (266, loc, "Cannot implicitly convert type `{0}' to `{1}'. An explicit conversion exists (are you missing a cast?)",
1282                                         TypeManager.CSharpName (source), TypeManager.CSharpName (target));
1283                                 return;
1284                         }
1285
1286                         Report.Error (29, loc, "Cannot implicitly convert type {0} to `{1}'",
1287                                       source == TypeManager.anonymous_method_type ?
1288                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1289                                       TypeManager.CSharpName (target));
1290                 }
1291
1292                 /// <summary>
1293                 ///   Attempts to implicitly convert `source' into `target_type', using
1294                 ///   ImplicitConversion.  If there is no implicit conversion, then
1295                 ///   an error is signaled
1296                 /// </summary>
1297                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1298                                                                      Type target_type, Location loc)
1299                 {
1300                         Expression e;
1301
1302                         e = ImplicitConversion (ec, source, target_type, loc);
1303                         if (e != null)
1304                                 return e;
1305
1306                         if (source is DoubleLiteral) {
1307                                 if (target_type == TypeManager.float_type) {
1308                                         Error_664 (loc, "float", "f");
1309                                         return null;
1310                                 }
1311                                 if (target_type == TypeManager.decimal_type) {
1312                                         Error_664 (loc, "decimal", "m");
1313                                         return null;
1314                                 }
1315                         }
1316
1317                         source.Error_ValueCannotBeConverted (loc, target_type);
1318                         return null;
1319                 }
1320
1321                 static void Error_664 (Location loc, string type, string suffix) {
1322                         Report.Error (664, loc,
1323                                 "Literal of type double cannot be implicitly converted to type `{0}'. Add suffix `{1}' to create a literal of this type",
1324                                 type, suffix);
1325                 }
1326
1327                 /// <summary>
1328                 ///   Performs the explicit numeric conversions
1329                 /// </summary>
1330                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1331                 {
1332                         Type expr_type = expr.Type;
1333
1334                         //
1335                         // If we have an enumeration, extract the underlying type,
1336                         // use this during the comparison, but wrap around the original
1337                         // target_type
1338                         //
1339                         Type real_target_type = target_type;
1340
1341                         if (TypeManager.IsEnumType (real_target_type))
1342                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1343
1344                         if (ImplicitStandardConversionExists (ec, expr, real_target_type)){
1345                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1346
1347                                 if (real_target_type != target_type)
1348                                         return new EmptyCast (ce, target_type);
1349                                 return ce;
1350                         }
1351
1352                         if (expr_type == TypeManager.sbyte_type){
1353                                 //
1354                                 // From sbyte to byte, ushort, uint, ulong, char
1355                                 //
1356                                 if (real_target_type == TypeManager.byte_type)
1357                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1358                                 if (real_target_type == TypeManager.ushort_type)
1359                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1360                                 if (real_target_type == TypeManager.uint32_type)
1361                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1362                                 if (real_target_type == TypeManager.uint64_type)
1363                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1364                                 if (real_target_type == TypeManager.char_type)
1365                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1366                         } else if (expr_type == TypeManager.byte_type){
1367                                 //
1368                                 // From byte to sbyte and char
1369                                 //
1370                                 if (real_target_type == TypeManager.sbyte_type)
1371                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1372                                 if (real_target_type == TypeManager.char_type)
1373                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1374                         } else if (expr_type == TypeManager.short_type){
1375                                 //
1376                                 // From short to sbyte, byte, ushort, uint, ulong, char
1377                                 //
1378                                 if (real_target_type == TypeManager.sbyte_type)
1379                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1380                                 if (real_target_type == TypeManager.byte_type)
1381                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1382                                 if (real_target_type == TypeManager.ushort_type)
1383                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1384                                 if (real_target_type == TypeManager.uint32_type)
1385                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1386                                 if (real_target_type == TypeManager.uint64_type)
1387                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1388                                 if (real_target_type == TypeManager.char_type)
1389                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1390                         } else if (expr_type == TypeManager.ushort_type){
1391                                 //
1392                                 // From ushort to sbyte, byte, short, char
1393                                 //
1394                                 if (real_target_type == TypeManager.sbyte_type)
1395                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1396                                 if (real_target_type == TypeManager.byte_type)
1397                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1398                                 if (real_target_type == TypeManager.short_type)
1399                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1400                                 if (real_target_type == TypeManager.char_type)
1401                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1402                         } else if (expr_type == TypeManager.int32_type){
1403                                 //
1404                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1405                                 //
1406                                 if (real_target_type == TypeManager.sbyte_type)
1407                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1408                                 if (real_target_type == TypeManager.byte_type)
1409                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1410                                 if (real_target_type == TypeManager.short_type)
1411                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1412                                 if (real_target_type == TypeManager.ushort_type)
1413                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1414                                 if (real_target_type == TypeManager.uint32_type)
1415                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1416                                 if (real_target_type == TypeManager.uint64_type)
1417                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1418                                 if (real_target_type == TypeManager.char_type)
1419                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1420                         } else if (expr_type == TypeManager.uint32_type){
1421                                 //
1422                                 // From uint to sbyte, byte, short, ushort, int, char
1423                                 //
1424                                 if (real_target_type == TypeManager.sbyte_type)
1425                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1426                                 if (real_target_type == TypeManager.byte_type)
1427                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1428                                 if (real_target_type == TypeManager.short_type)
1429                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1430                                 if (real_target_type == TypeManager.ushort_type)
1431                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1432                                 if (real_target_type == TypeManager.int32_type)
1433                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1434                                 if (real_target_type == TypeManager.char_type)
1435                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1436                         } else if (expr_type == TypeManager.int64_type){
1437                                 //
1438                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1439                                 //
1440                                 if (real_target_type == TypeManager.sbyte_type)
1441                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1442                                 if (real_target_type == TypeManager.byte_type)
1443                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1444                                 if (real_target_type == TypeManager.short_type)
1445                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1446                                 if (real_target_type == TypeManager.ushort_type)
1447                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1448                                 if (real_target_type == TypeManager.int32_type)
1449                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1450                                 if (real_target_type == TypeManager.uint32_type)
1451                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1452                                 if (real_target_type == TypeManager.uint64_type)
1453                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1454                                 if (real_target_type == TypeManager.char_type)
1455                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1456                         } else if (expr_type == TypeManager.uint64_type){
1457                                 //
1458                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1459                                 //
1460                                 if (real_target_type == TypeManager.sbyte_type)
1461                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1462                                 if (real_target_type == TypeManager.byte_type)
1463                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1464                                 if (real_target_type == TypeManager.short_type)
1465                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1466                                 if (real_target_type == TypeManager.ushort_type)
1467                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1468                                 if (real_target_type == TypeManager.int32_type)
1469                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1470                                 if (real_target_type == TypeManager.uint32_type)
1471                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1472                                 if (real_target_type == TypeManager.int64_type)
1473                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1474                                 if (real_target_type == TypeManager.char_type)
1475                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1476                         } else if (expr_type == TypeManager.char_type){
1477                                 //
1478                                 // From char to sbyte, byte, short
1479                                 //
1480                                 if (real_target_type == TypeManager.sbyte_type)
1481                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1482                                 if (real_target_type == TypeManager.byte_type)
1483                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1484                                 if (real_target_type == TypeManager.short_type)
1485                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1486                         } else if (expr_type == TypeManager.float_type){
1487                                 //
1488                                 // From float to sbyte, byte, short,
1489                                 // ushort, int, uint, long, ulong, char
1490                                 // or decimal
1491                                 //
1492                                 if (real_target_type == TypeManager.sbyte_type)
1493                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1494                                 if (real_target_type == TypeManager.byte_type)
1495                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1496                                 if (real_target_type == TypeManager.short_type)
1497                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1498                                 if (real_target_type == TypeManager.ushort_type)
1499                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1500                                 if (real_target_type == TypeManager.int32_type)
1501                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1502                                 if (real_target_type == TypeManager.uint32_type)
1503                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1504                                 if (real_target_type == TypeManager.int64_type)
1505                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1506                                 if (real_target_type == TypeManager.uint64_type)
1507                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1508                                 if (real_target_type == TypeManager.char_type)
1509                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1510                                 if (real_target_type == TypeManager.decimal_type)
1511                                         return new CastToDecimal (ec, expr, true);
1512                         } else if (expr_type == TypeManager.double_type){
1513                                 //
1514                                 // From double to sbyte, byte, short,
1515                                 // ushort, int, uint, long, ulong,
1516                                 // char, float or decimal
1517                                 //
1518                                 if (real_target_type == TypeManager.sbyte_type)
1519                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1520                                 if (real_target_type == TypeManager.byte_type)
1521                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1522                                 if (real_target_type == TypeManager.short_type)
1523                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1524                                 if (real_target_type == TypeManager.ushort_type)
1525                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1526                                 if (real_target_type == TypeManager.int32_type)
1527                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1528                                 if (real_target_type == TypeManager.uint32_type)
1529                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1530                                 if (real_target_type == TypeManager.int64_type)
1531                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1532                                 if (real_target_type == TypeManager.uint64_type)
1533                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1534                                 if (real_target_type == TypeManager.char_type)
1535                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1536                                 if (real_target_type == TypeManager.float_type)
1537                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1538                                 if (real_target_type == TypeManager.decimal_type)
1539                                         return new CastToDecimal (ec, expr, true);
1540                         } else if (expr_type == TypeManager.decimal_type) {
1541                                 //
1542                                 // From decimal to sbyte, byte, short, ushort, int, uint,
1543                                 // long, ulong, char, double or float
1544                                 //
1545                                 if (real_target_type == TypeManager.sbyte_type ||
1546                                     real_target_type == TypeManager.byte_type ||
1547                                     real_target_type == TypeManager.short_type ||
1548                                     real_target_type == TypeManager.ushort_type ||
1549                                     real_target_type == TypeManager.int32_type ||
1550                                     real_target_type == TypeManager.uint32_type ||
1551                                     real_target_type == TypeManager.int64_type ||
1552                                     real_target_type == TypeManager.uint64_type ||
1553                                     real_target_type == TypeManager.char_type ||
1554                                     real_target_type == TypeManager.double_type ||
1555                                     real_target_type == TypeManager.float_type)
1556                                         return new CastFromDecimal (ec, expr, target_type);
1557                         }
1558                         return null;
1559                 }
1560
1561                 /// <summary>
1562                 ///  Returns whether an explicit reference conversion can be performed
1563                 ///  from source_type to target_type
1564                 /// </summary>
1565                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1566                 {
1567                         bool target_is_value_type = target_type.IsValueType;
1568
1569                         if (source_type == target_type)
1570                                 return true;
1571
1572                         //
1573                         // From object to any reference type
1574                         //
1575                         if (source_type == TypeManager.object_type && !target_is_value_type)
1576                                 return true;
1577
1578                         //
1579                         // From any class S to any class-type T, provided S is a base class of T
1580                         //
1581                         if (target_type.IsSubclassOf (source_type))
1582                                 return true;
1583
1584                         //
1585                         // From any interface type S to any interface T provided S is not derived from T
1586                         //
1587                         if (source_type.IsInterface && target_type.IsInterface){
1588                                 if (!target_type.IsSubclassOf (source_type))
1589                                         return true;
1590                         }
1591
1592                         //
1593                         // From any class type S to any interface T, provided S is not sealed
1594                         // and provided S does not implement T.
1595                         //
1596                         if (target_type.IsInterface && !source_type.IsSealed &&
1597                             !TypeManager.ImplementsInterface (source_type, target_type))
1598                                 return true;
1599
1600                         //
1601                         // From any interface-type S to to any class type T, provided T is not
1602                         // sealed, or provided T implements S.
1603                         //
1604                         if (source_type.IsInterface &&
1605                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1606                                 return true;
1607
1608
1609                         // From an array type S with an element type Se to an array type T with an
1610                         // element type Te provided all the following are true:
1611                         //     * S and T differe only in element type, in other words, S and T
1612                         //       have the same number of dimensions.
1613                         //     * Both Se and Te are reference types
1614                         //     * An explicit referenc conversions exist from Se to Te
1615                         //
1616                         if (source_type.IsArray && target_type.IsArray) {
1617                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1618
1619                                         Type source_element_type = TypeManager.GetElementType (source_type);
1620                                         Type target_element_type = TypeManager.GetElementType (target_type);
1621
1622                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1623                                                 if (ExplicitReferenceConversionExists (source_element_type,
1624                                                                                        target_element_type))
1625                                                         return true;
1626                                 }
1627                         }
1628
1629
1630                         // From System.Array to any array-type
1631                         if (source_type == TypeManager.array_type &&
1632                             target_type.IsArray){
1633                                 return true;
1634                         }
1635
1636                         //
1637                         // From System delegate to any delegate-type
1638                         //
1639                         if (source_type == TypeManager.delegate_type &&
1640                             target_type.IsSubclassOf (TypeManager.delegate_type))
1641                                 return true;
1642
1643                         //
1644                         // From ICloneable to Array or Delegate types
1645                         //
1646                         if (source_type == TypeManager.icloneable_type &&
1647                             (target_type == TypeManager.array_type ||
1648                              target_type == TypeManager.delegate_type))
1649                                 return true;
1650
1651                         return false;
1652                 }
1653
1654                 /// <summary>
1655                 ///   Implements Explicit Reference conversions
1656                 /// </summary>
1657                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1658                 {
1659                         Type source_type = source.Type;
1660                         bool target_is_value_type = target_type.IsValueType;
1661
1662                         //
1663                         // From object to any reference type
1664                         //
1665                         if (source_type == TypeManager.object_type && !target_is_value_type)
1666                                 return new ClassCast (source, target_type);
1667
1668                         //
1669                         // Unboxing conversion.
1670                         //
1671                         if (((source_type == TypeManager.enum_type &&
1672                                 !(source is EmptyCast)) ||
1673                                 source_type == TypeManager.value_type) && target_is_value_type)
1674                                 return new UnboxCast (source, target_type);
1675
1676                         //
1677                         // From any class S to any class-type T, provided S is a base class of T
1678                         //
1679                         if (target_type.IsSubclassOf (source_type))
1680                                 return new ClassCast (source, target_type);
1681
1682                         //
1683                         // From any interface type S to any interface T provided S is not derived from T
1684                         //
1685                         if (source_type.IsInterface && target_type.IsInterface){
1686                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1687                                         return null;
1688                                 else
1689                                         return new ClassCast (source, target_type);
1690                         }
1691
1692                         //
1693                         // From any class type S to any interface T, provides S is not sealed
1694                         // and provided S does not implement T.
1695                         //
1696                         if (target_type.IsInterface && !source_type.IsSealed) {
1697                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1698                                         return null;
1699                                 else
1700                                         return new ClassCast (source, target_type);
1701
1702                         }
1703
1704                         //
1705                         // From any interface-type S to to any class type T, provided T is not
1706                         // sealed, or provided T implements S.
1707                         //
1708                         if (source_type.IsInterface) {
1709                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1710                                         if (target_type.IsClass)
1711                                                 return new ClassCast (source, target_type);
1712                                         else
1713                                                 return new UnboxCast (source, target_type);
1714                                 }
1715
1716                                 return null;
1717                         }
1718
1719                         // From an array type S with an element type Se to an array type T with an
1720                         // element type Te provided all the following are true:
1721                         //     * S and T differe only in element type, in other words, S and T
1722                         //       have the same number of dimensions.
1723                         //     * Both Se and Te are reference types
1724                         //     * An explicit referenc conversions exist from Se to Te
1725                         //
1726                         if (source_type.IsArray && target_type.IsArray) {
1727                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1728
1729                                         Type source_element_type = TypeManager.GetElementType (source_type);
1730                                         Type target_element_type = TypeManager.GetElementType (target_type);
1731
1732                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1733                                                 if (ExplicitReferenceConversionExists (source_element_type,
1734                                                                                        target_element_type))
1735                                                         return new ClassCast (source, target_type);
1736                                 }
1737                         }
1738
1739
1740                         // From System.Array to any array-type
1741                         if (source_type == TypeManager.array_type &&
1742                             target_type.IsArray) {
1743                                 return new ClassCast (source, target_type);
1744                         }
1745
1746                         //
1747                         // From System delegate to any delegate-type
1748                         //
1749                         if (source_type == TypeManager.delegate_type &&
1750                             target_type.IsSubclassOf (TypeManager.delegate_type))
1751                                 return new ClassCast (source, target_type);
1752
1753                         //
1754                         // From ICloneable to Array or Delegate types
1755                         //
1756                         if (source_type == TypeManager.icloneable_type &&
1757                             (target_type == TypeManager.array_type ||
1758                              target_type == TypeManager.delegate_type))
1759                                 return new ClassCast (source, target_type);
1760
1761                         return null;
1762                 }
1763
1764                 /// <summary>
1765                 ///   Performs an explicit conversion of the expression `expr' whose
1766                 ///   type is expr.Type to `target_type'.
1767                 /// </summary>
1768                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1769                                                              Type target_type, Location loc)
1770                 {
1771                         Type expr_type = expr.Type;
1772                         Type original_expr_type = expr_type;
1773
1774                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1775
1776                         if (ne != null)
1777                                 return ne;
1778
1779                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1780                                 if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1781                                            target_type.IsSubclassOf (TypeManager.enum_type))
1782                                         return new UnboxCast (expr, target_type);
1783
1784                                 //
1785                                 // Notice that we have kept the expr_type unmodified, which is only
1786                                 // used later on to
1787                                 if (expr is EnumConstant)
1788                                         expr = ((EnumConstant) expr).Child;
1789                                 else
1790                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1791                                 expr_type = expr.Type;
1792                         }
1793
1794                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1795                         if (ne != null)
1796                                 return ne;
1797
1798                         //
1799                         // Unboxing conversion.
1800                         //
1801                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1802                                 return new UnboxCast (expr, target_type);
1803
1804                         //
1805                         // Skip the ExplicitReferenceConversion because we can not convert
1806                         // from Null to a ValueType, and ExplicitReference wont check against
1807                         // null literal explicitly
1808                         //
1809                         if (expr_type != TypeManager.null_type){
1810                                 ne = ExplicitReferenceConversion (expr, target_type);
1811                                 if (ne != null)
1812                                         return ne;
1813                         }
1814
1815                         if (ec.InUnsafe){
1816                                 if (target_type.IsPointer){
1817                                         if (expr_type.IsPointer)
1818                                                 return new EmptyCast (expr, target_type);
1819
1820                                         if (expr_type == TypeManager.sbyte_type ||
1821                                             expr_type == TypeManager.short_type ||
1822                                             expr_type == TypeManager.int32_type ||
1823                                             expr_type == TypeManager.int64_type)
1824                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
1825
1826                                         if (expr_type == TypeManager.ushort_type ||
1827                                             expr_type == TypeManager.uint32_type ||
1828                                             expr_type == TypeManager.uint64_type ||
1829                                             expr_type == TypeManager.byte_type)
1830                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1831                                 }
1832                                 if (expr_type.IsPointer){
1833                                         Expression e = null;
1834
1835                                         if (target_type == TypeManager.sbyte_type)
1836                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1837                                         else if (target_type == TypeManager.byte_type)
1838                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1839                                         else if (target_type == TypeManager.short_type)
1840                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1841                                         else if (target_type == TypeManager.ushort_type)
1842                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1843                                         else if (target_type == TypeManager.int32_type)
1844                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1845                                         else if (target_type == TypeManager.uint32_type)
1846                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1847                                         else if (target_type == TypeManager.uint64_type)
1848                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1849                                         else if (target_type == TypeManager.int64_type){
1850                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1851                                         }
1852
1853                                         if (e != null){
1854                                                 Expression ci, ce;
1855
1856                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1857
1858                                                 if (ci != null)
1859                                                         return ci;
1860
1861                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1862                                                 if (ce != null)
1863                                                         return ce;
1864                                                 //
1865                                                 // We should always be able to go from an uint32
1866                                                 // implicitly or explicitly to the other integral
1867                                                 // types
1868                                                 //
1869                                                 throw new Exception ("Internal compiler error");
1870                                         }
1871                                 }
1872                         }
1873
1874                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1875                         if (ne != null)
1876                                 return ne;
1877
1878                         if (expr is Constant)
1879                                 expr.Error_ValueCannotBeConverted (loc, target_type);
1880                         else
1881                                 Error_CannotConvertType (loc, original_expr_type, target_type);
1882                         return null;
1883                 }
1884
1885                 /// <summary>
1886                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1887                 /// </summary>
1888                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1889                                                                   Type target_type, Location l)
1890                 {
1891                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1892
1893                         if (ne != null)
1894                                 return ne;
1895
1896                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1897                         if (ne != null)
1898                                 return ne;
1899
1900                         ne = ExplicitReferenceConversion (expr, target_type);
1901                         if (ne != null)
1902                                 return ne;
1903
1904                         Error_CannotConvertType (l, expr.Type, target_type);
1905                         return null;
1906                 }
1907         }
1908 }