mcs/mcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 //
  23                 // This is used to prettify the code: a null argument is allowed
  24                 // for ImplicitStandardConversion as long as it is known that
  25                 // no anonymous method will play a role.
  26                 //
  27                 // FIXME: renamed from `const' to `static' to allow bootstraping from older
  28                 // versions of the compiler that could not cope with this construct.
  29                 //
  30                 public static EmitContext ConstantEC = null;
  31
  32                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  33                 {
  34                         Report.Error (30, loc, "Cannot convert type '" +
  35                                       TypeManager.CSharpName (source) + "' to '" +
  36                                       TypeManager.CSharpName (target) + "'");
  37                 }
  38
  39                 static EmptyExpression MyEmptyExpr;
  40                 static public Expression ImplicitReferenceConversion (Expression expr, Type target_type)
  41                 {
  42                         Type expr_type = expr.Type;
  43
  44                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
  45                                 // if we are a method group, emit a warning
  46
  47                                 expr.Emit (null);
  48                         }
  49
  50                         if (expr_type == TypeManager.void_type)
  51                                 return null;
  52
  53                         //
  54                         // notice that it is possible to write "ValueType v = 1", the ValueType here
  55                         // is an abstract class, and not really a value type, so we apply the same rules.
  56                         //
  57                         if (target_type == TypeManager.object_type) {
  58                                 //
  59                                 // A pointer type cannot be converted to object
  60                                 //
  61                                 if (expr_type.IsPointer)
  62                                         return null;
  63
  64                                 if (expr_type.IsValueType)
  65                                         return new BoxedCast (expr);
  66                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
  67                                         if (expr_type == TypeManager.anonymous_method_type)
  68                                                 return null;
  69                                         return new EmptyCast (expr, target_type);
  70                                 }
  71
  72                                 return null;
  73                         } else if (target_type == TypeManager.value_type) {
  74                                 if (expr_type.IsValueType)
  75                                         return new BoxedCast (expr);
  76                                 if (expr_type == TypeManager.null_type)
  77                                         return new NullCast (expr, target_type);
  78
  79                                 return null;
  80                         } else if (expr_type.IsSubclassOf (target_type)) {
  81                                 //
  82                                 // Special case: enumeration to System.Enum.
  83                                 // System.Enum is not a value type, it is a class, so we need
  84                                 // a boxing conversion
  85                                 //
  86                                 if (expr_type.IsEnum)
  87                                         return new BoxedCast (expr);
  88
  89                                 return new EmptyCast (expr, target_type);
  90                         }
  91
  92                         // This code is kind of mirrored inside ImplicitStandardConversionExists
  93                         // with the small distinction that we only probe there
  94                         //
  95                         // Always ensure that the code here and there is in sync
  96
  97                         // from the null type to any reference-type.
  98                         if (expr_type == TypeManager.null_type){
  99                                 if (target_type.IsPointer)
 100                                         return new EmptyCast (NullPointer.Null, target_type);
 101
 102                                 if (!target_type.IsValueType)
 103                                         return new NullCast (expr, target_type);
 104                         }
 105
 106                         // from any class-type S to any interface-type T.
 107                         if (target_type.IsInterface) {
 108                                 if (target_type != TypeManager.iconvertible_type &&
 109                                     expr_type.IsValueType && (expr is Constant) &&
 110                                     !(expr is IntLiteral || expr is BoolLiteral ||
 111                                       expr is FloatLiteral || expr is DoubleLiteral ||
 112                                       expr is LongLiteral || expr is CharLiteral ||
 113                                       expr is StringLiteral || expr is DecimalLiteral ||
 114                                       expr is UIntLiteral || expr is ULongLiteral)) {
 115                                         return null;
 116                                 }
 117
 118                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 119                                         if (expr_type.IsClass)
 120                                                 return new EmptyCast (expr, target_type);
 121                                         else if (expr_type.IsValueType)
 122                                                 return new BoxedCast (expr, target_type);
 123                                         else
 124                                                 return new EmptyCast (expr, target_type);
 125                                 }
 126                         }
 127
 128                         // from any interface type S to interface-type T.
 129                         if (expr_type.IsInterface && target_type.IsInterface) {
 130                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 131                                         return new EmptyCast (expr, target_type);
 132                                 else
 133                                         return null;
 134                         }
 135
 136                         // from an array-type S to an array-type of type T
 137                         if (expr_type.IsArray && target_type.IsArray) {
 138                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 139
 140                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 141
 142                                         if (MyEmptyExpr == null)
 143                                                 MyEmptyExpr = new EmptyExpression ();
 144
 145                                         MyEmptyExpr.SetType (expr_element_type);
 146                                         Type target_element_type = TypeManager.GetElementType (target_type);
 147
 148                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 149                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 150                                                                                       target_element_type))
 151                                                         return new EmptyCast (expr, target_type);
 152                                 }
 153                         }
 154
 155                         // from an array-type to System.Array
 156                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 157                                 return new EmptyCast (expr, target_type);
 158
 159                         // from any delegate type to System.Delegate
 160                         if ((expr_type == TypeManager.delegate_type ||
 161                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 162                             target_type == TypeManager.delegate_type)
 163                                 return new EmptyCast (expr, target_type);
 164
 165                         // from any array-type or delegate type into System.ICloneable.
 166                         if (expr_type.IsArray ||
 167                             expr_type == TypeManager.delegate_type ||
 168                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 169                                 if (target_type == TypeManager.icloneable_type)
 170                                         return new EmptyCast (expr, target_type);
 171
 172                         return null;
 173                 }
 174
 175                 //
 176                 // Tests whether an implicit reference conversion exists between expr_type
 177                 // and target_type
 178                 //
 179                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 180                 {
 181                         Type expr_type = expr.Type;
 182
 183                         //
 184                         // This is the boxed case.
 185                         //
 186                         if (target_type == TypeManager.object_type) {
 187                                 if (expr_type.IsClass || expr_type.IsValueType ||
 188                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 189                                         if (target_type != TypeManager.anonymous_method_type)
 190                                                 return true;
 191
 192                                 return false;
 193                         } else if (expr_type.IsSubclassOf (target_type))
 194                                 return true;
 195
 196                         // Please remember that all code below actually comes
 197                         // from ImplicitReferenceConversion so make sure code remains in sync
 198
 199                         // from any class-type S to any interface-type T.
 200                         if (target_type.IsInterface) {
 201                                 if (target_type != TypeManager.iconvertible_type &&
 202                                     expr_type.IsValueType && (expr is Constant) &&
 203                                     !(expr is IntLiteral || expr is BoolLiteral ||
 204                                       expr is FloatLiteral || expr is DoubleLiteral ||
 205                                       expr is LongLiteral || expr is CharLiteral ||
 206                                       expr is StringLiteral || expr is DecimalLiteral ||
 207                                       expr is UIntLiteral || expr is ULongLiteral)) {
 208                                         return false;
 209                                 }
 210
 211                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 212                                         return true;
 213                         }
 214
 215                         // from any interface type S to interface-type T.
 216                         if (expr_type.IsInterface && target_type.IsInterface)
 217                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 218                                         return true;
 219
 220                         // from an array-type S to an array-type of type T
 221                         if (expr_type.IsArray && target_type.IsArray) {
 222                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 223
 224                                         Type expr_element_type = expr_type.GetElementType ();
 225
 226                                         if (MyEmptyExpr == null)
 227                                                 MyEmptyExpr = new EmptyExpression ();
 228
 229                                         MyEmptyExpr.SetType (expr_element_type);
 230                                         Type target_element_type = TypeManager.GetElementType (target_type);
 231
 232                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 233                                                 if (ImplicitStandardConversionExists (ConstantEC, MyEmptyExpr,
 234                                                                                       target_element_type))
 235                                                         return true;
 236                                 }
 237                         }
 238
 239                         // from an array-type to System.Array
 240                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 241                                 return true;
 242
 243                         // from any delegate type to System.Delegate
 244                         if ((expr_type == TypeManager.delegate_type ||
 245                              expr_type.IsSubclassOf (TypeManager.delegate_type)) &&
 246                             target_type == TypeManager.delegate_type)
 247                                 if (target_type.IsAssignableFrom (expr_type))
 248                                         return true;
 249
 250                         // from any array-type or delegate type into System.ICloneable.
 251                         if (expr_type.IsArray ||
 252                             expr_type == TypeManager.delegate_type ||
 253                             expr_type.IsSubclassOf (TypeManager.delegate_type))
 254                                 if (target_type == TypeManager.icloneable_type)
 255                                         return true;
 256
 257                         // from the null type to any reference-type.
 258                         if (expr_type == TypeManager.null_type){
 259                                 if (target_type.IsPointer)
 260                                         return true;
 261
 262                                 if (!target_type.IsValueType)
 263                                         return true;
 264                         }
 265                         return false;
 266                 }
 267
 268                 /// <summary>
 269                 ///   Implicit Numeric Conversions.
 270                 ///
 271                 ///   expr is the expression to convert, returns a new expression of type
 272                 ///   target_type or null if an implicit conversion is not possible.
 273                 /// </summary>
 274                 static public Expression ImplicitNumericConversion (EmitContext ec, Expression expr,
 275                                                                     Type target_type, Location loc)
 276                 {
 277                         Type expr_type = expr.Type;
 278
 279                         //
 280                         // Attempt to do the implicit constant expression conversions
 281
 282                         if (expr is Constant){
 283                                 if (expr is IntConstant){
 284                                         Expression e;
 285
 286                                         e = TryImplicitIntConversion (target_type, (IntConstant) expr);
 287
 288                                         if (e != null)
 289                                                 return e;
 290                                 } else if (expr is LongConstant && target_type == TypeManager.uint64_type){
 291                                         //
 292                                         // Try the implicit constant expression conversion
 293                                         // from long to ulong, instead of a nice routine,
 294                                         // we just inline it
 295                                         //
 296                                         long v = ((LongConstant) expr).Value;
 297                                         if (v >= 0)
 298                                                 return new ULongConstant ((ulong) v);
 299                                 }
 300                         }
 301
 302                         Type real_target_type = target_type;
 303
 304                         if (expr_type == TypeManager.sbyte_type){
 305                                 //
 306                                 // From sbyte to short, int, long, float, double, decimal
 307                                 //
 308                                 if (real_target_type == TypeManager.int32_type)
 309                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 310                                 if (real_target_type == TypeManager.int64_type)
 311                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 312                                 if (real_target_type == TypeManager.double_type)
 313                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 314                                 if (real_target_type == TypeManager.float_type)
 315                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 316                                 if (real_target_type == TypeManager.short_type)
 317                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 318                                 if (real_target_type == TypeManager.decimal_type)
 319                                         return new CastToDecimal (ec, expr);
 320                         } else if (expr_type == TypeManager.byte_type){
 321                                 //
 322                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 323                                 //
 324                                 if ((real_target_type == TypeManager.short_type) ||
 325                                     (real_target_type == TypeManager.ushort_type) ||
 326                                     (real_target_type == TypeManager.int32_type) ||
 327                                     (real_target_type == TypeManager.uint32_type))
 328                                         return new EmptyCast (expr, target_type);
 329
 330                                 if (real_target_type == TypeManager.uint64_type)
 331                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 332                                 if (real_target_type == TypeManager.int64_type)
 333                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 334                                 if (real_target_type == TypeManager.float_type)
 335                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 336                                 if (real_target_type == TypeManager.double_type)
 337                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 338                                 if (real_target_type == TypeManager.decimal_type)
 339                                         return new CastToDecimal (ec, expr);
 340
 341                         } else if (expr_type == TypeManager.short_type){
 342                                 //
 343                                 // From short to int, long, float, double, decimal
 344                                 //
 345                                 if (real_target_type == TypeManager.int32_type)
 346                                         return new EmptyCast (expr, target_type);
 347                                 if (real_target_type == TypeManager.int64_type)
 348                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 349                                 if (real_target_type == TypeManager.double_type)
 350                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 351                                 if (real_target_type == TypeManager.float_type)
 352                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 353                                 if (real_target_type == TypeManager.decimal_type)
 354                                         return new CastToDecimal (ec, expr);
 355
 356                         } else if (expr_type == TypeManager.ushort_type){
 357                                 //
 358                                 // From ushort to int, uint, long, ulong, float, double, decimal
 359                                 //
 360                                 if (real_target_type == TypeManager.uint32_type)
 361                                         return new EmptyCast (expr, target_type);
 362
 363                                 if (real_target_type == TypeManager.uint64_type)
 364                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 365                                 if (real_target_type == TypeManager.int32_type)
 366                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 367                                 if (real_target_type == TypeManager.int64_type)
 368                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 369                                 if (real_target_type == TypeManager.double_type)
 370                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 371                                 if (real_target_type == TypeManager.float_type)
 372                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 373                                 if (real_target_type == TypeManager.decimal_type)
 374                                         return new CastToDecimal (ec, expr);
 375                         } else if (expr_type == TypeManager.int32_type){
 376                                 //
 377                                 // From int to long, float, double, decimal
 378                                 //
 379                                 if (real_target_type == TypeManager.int64_type)
 380                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 381                                 if (real_target_type == TypeManager.double_type)
 382                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 383                                 if (real_target_type == TypeManager.float_type)
 384                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 385                                 if (real_target_type == TypeManager.decimal_type)
 386                                         return new CastToDecimal (ec, expr);
 387                         } else if (expr_type == TypeManager.uint32_type){
 388                                 //
 389                                 // From uint to long, ulong, float, double, decimal
 390                                 //
 391                                 if (real_target_type == TypeManager.int64_type)
 392                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 393                                 if (real_target_type == TypeManager.uint64_type)
 394                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 395                                 if (real_target_type == TypeManager.double_type)
 396                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 397                                                                OpCodes.Conv_R8);
 398                                 if (real_target_type == TypeManager.float_type)
 399                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 400                                                                OpCodes.Conv_R4);
 401                                 if (real_target_type == TypeManager.decimal_type)
 402                                         return new CastToDecimal (ec, expr);
 403                         } else if (expr_type == TypeManager.int64_type){
 404                                 //
 405                                 // From long/ulong to float, double
 406                                 //
 407                                 if (real_target_type == TypeManager.double_type)
 408                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 409                                 if (real_target_type == TypeManager.float_type)
 410                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 411                                 if (real_target_type == TypeManager.decimal_type)
 412                                         return new CastToDecimal (ec, expr);
 413                         } else if (expr_type == TypeManager.uint64_type){
 414                                 //
 415                                 // From ulong to float, double
 416                                 //
 417                                 if (real_target_type == TypeManager.double_type)
 418                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 419                                                                OpCodes.Conv_R8);
 420                                 if (real_target_type == TypeManager.float_type)
 421                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 422                                                                OpCodes.Conv_R4);
 423                                 if (real_target_type == TypeManager.decimal_type)
 424                                         return new CastToDecimal (ec, expr);
 425                         } else if (expr_type == TypeManager.char_type){
 426                                 //
 427                                 // From char to ushort, int, uint, long, ulong, float, double, decimal
 428                                 //
 429                                 if ((real_target_type == TypeManager.ushort_type) ||
 430                                     (real_target_type == TypeManager.int32_type) ||
 431                                     (real_target_type == TypeManager.uint32_type))
 432                                         return new EmptyCast (expr, target_type);
 433                                 if (real_target_type == TypeManager.uint64_type)
 434                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 435                                 if (real_target_type == TypeManager.int64_type)
 436                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 437                                 if (real_target_type == TypeManager.float_type)
 438                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 439                                 if (real_target_type == TypeManager.double_type)
 440                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 441                                 if (real_target_type == TypeManager.decimal_type)
 442                                         return new CastToDecimal (ec, expr);
 443                         } else if (expr_type == TypeManager.float_type){
 444                                 //
 445                                 // float to double
 446                                 //
 447                                 if (real_target_type == TypeManager.double_type)
 448                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 449                         }
 450
 451                         return null;
 452                 }
 453
 454
 455                 /// <summary>
 456                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 457                 ///  implicit user defined conversions - needed for overload resolution
 458                 /// </summary>
 459                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 460                 {
 461                         if (ImplicitStandardConversionExists (ec, expr, target_type))
 462                                 return true;
 463
 464                         Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 465
 466                         if (dummy != null)
 467                                 return true;
 468
 469                         return false;
 470                 }
 471
 472                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 473                 {
 474                         Expression dummy = ImplicitUserConversion (
 475                                 ec, new EmptyExpression (source), target, Location.Null);
 476                         return dummy != null;
 477                 }
 478
 479                 /// <summary>
 480                 ///  Determines if a standard implicit conversion exists from
 481                 ///  expr_type to target_type
 482                 ///
 483                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 484                 /// </summary>
 485                 public static bool ImplicitStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 486                 {
 487                         Type expr_type = expr.Type;
 488
 489                         if (expr_type == TypeManager.void_type)
 490                                 return false;
 491
 492                         if (expr_type == target_type)
 493                                 return true;
 494
 495
 496                         // First numeric conversions
 497
 498                         if (expr_type == TypeManager.sbyte_type){
 499                                 //
 500                                 // From sbyte to short, int, long, float, double, decimal
 501                                 //
 502                                 if ((target_type == TypeManager.int32_type) ||
 503                                     (target_type == TypeManager.int64_type) ||
 504                                     (target_type == TypeManager.double_type) ||
 505                                     (target_type == TypeManager.float_type)  ||
 506                                     (target_type == TypeManager.short_type) ||
 507                                     (target_type == TypeManager.decimal_type))
 508                                         return true;
 509
 510                         } else if (expr_type == TypeManager.byte_type){
 511                                 //
 512                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 513                                 //
 514                                 if ((target_type == TypeManager.short_type) ||
 515                                     (target_type == TypeManager.ushort_type) ||
 516                                     (target_type == TypeManager.int32_type) ||
 517                                     (target_type == TypeManager.uint32_type) ||
 518                                     (target_type == TypeManager.uint64_type) ||
 519                                     (target_type == TypeManager.int64_type) ||
 520                                     (target_type == TypeManager.float_type) ||
 521                                     (target_type == TypeManager.double_type) ||
 522                                     (target_type == TypeManager.decimal_type))
 523                                         return true;
 524
 525                         } else if (expr_type == TypeManager.short_type){
 526                                 //
 527                                 // From short to int, long, double, float, decimal
 528                                 //
 529                                 if ((target_type == TypeManager.int32_type) ||
 530                                     (target_type == TypeManager.int64_type) ||
 531                                     (target_type == TypeManager.double_type) ||
 532                                     (target_type == TypeManager.float_type) ||
 533                                     (target_type == TypeManager.decimal_type))
 534                                         return true;
 535
 536                         } else if (expr_type == TypeManager.ushort_type){
 537                                 //
 538                                 // From ushort to int, uint, long, ulong, double, float, decimal
 539                                 //
 540                                 if ((target_type == TypeManager.uint32_type) ||
 541                                     (target_type == TypeManager.uint64_type) ||
 542                                     (target_type == TypeManager.int32_type) ||
 543                                     (target_type == TypeManager.int64_type) ||
 544                                     (target_type == TypeManager.double_type) ||
 545                                     (target_type == TypeManager.float_type) ||
 546                                     (target_type == TypeManager.decimal_type))
 547                                         return true;
 548
 549                         } else if (expr_type == TypeManager.int32_type){
 550                                 //
 551                                 // From int to long, double, float, decimal
 552                                 //
 553                                 if ((target_type == TypeManager.int64_type) ||
 554                                     (target_type == TypeManager.double_type) ||
 555                                     (target_type == TypeManager.float_type) ||
 556                                     (target_type == TypeManager.decimal_type))
 557                                         return true;
 558
 559                         } else if (expr_type == TypeManager.uint32_type){
 560                                 //
 561                                 // From uint to long, ulong, double, float, decimal
 562                                 //
 563                                 if ((target_type == TypeManager.int64_type) ||
 564                                     (target_type == TypeManager.uint64_type) ||
 565                                     (target_type == TypeManager.double_type) ||
 566                                     (target_type == TypeManager.float_type) ||
 567                                     (target_type == TypeManager.decimal_type))
 568                                         return true;
 569
 570                         } else if ((expr_type == TypeManager.uint64_type) ||
 571                                    (expr_type == TypeManager.int64_type)) {
 572                                 //
 573                                 // From long/ulong to double, float, decimal
 574                                 //
 575                                 if ((target_type == TypeManager.double_type) ||
 576                                     (target_type == TypeManager.float_type) ||
 577                                     (target_type == TypeManager.decimal_type))
 578                                         return true;
 579
 580                         } else if (expr_type == TypeManager.char_type){
 581                                 //
 582                                 // From char to ushort, int, uint, ulong, long, float, double, decimal
 583                                 //
 584                                 if ((target_type == TypeManager.ushort_type) ||
 585                                     (target_type == TypeManager.int32_type) ||
 586                                     (target_type == TypeManager.uint32_type) ||
 587                                     (target_type == TypeManager.uint64_type) ||
 588                                     (target_type == TypeManager.int64_type) ||
 589                                     (target_type == TypeManager.float_type) ||
 590                                     (target_type == TypeManager.double_type) ||
 591                                     (target_type == TypeManager.decimal_type))
 592                                         return true;
 593
 594                         } else if (expr_type == TypeManager.float_type){
 595                                 //
 596                                 // float to double
 597                                 //
 598                                 if (target_type == TypeManager.double_type)
 599                                         return true;
 600                         }
 601
 602                         if (expr.eclass == ExprClass.MethodGroup){
 603                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 604                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 605                                         if (mg != null){
 606                                                 //
 607                                                 // This should not happen frequently, so we can create an object
 608                                                 // to test compatibility
 609                                                 //
 610                                                 Expression c = ImplicitDelegateCreation.Create (
 611                                                         ec, mg, target_type, true, Location.Null);
 612                                                 return c != null;
 613                                         }
 614                                 }
 615                         }
 616
 617                         if (ImplicitReferenceConversionExists (expr, target_type))
 618                                 return true;
 619
 620                         //
 621                         // Implicit Constant Expression Conversions
 622                         //
 623                         if (expr is IntConstant){
 624                                 int value = ((IntConstant) expr).Value;
 625
 626                                 if (target_type == TypeManager.sbyte_type){
 627                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 628                                                 return true;
 629                                 } else if (target_type == TypeManager.byte_type){
 630                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 631                                                 return true;
 632                                 } else if (target_type == TypeManager.short_type){
 633                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 634                                                 return true;
 635                                 } else if (target_type == TypeManager.ushort_type){
 636                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 637                                                 return true;
 638                                 } else if (target_type == TypeManager.uint32_type){
 639                                         if (value >= 0)
 640                                                 return true;
 641                                 } else if (target_type == TypeManager.uint64_type){
 642                                          //
 643                                          // we can optimize this case: a positive int32
 644                                          // always fits on a uint64.  But we need an opcode
 645                                          // to do it.
 646                                          //
 647                                         if (value >= 0)
 648                                                 return true;
 649                                 }
 650
 651                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 652                                         return true;
 653                         }
 654
 655                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 656                                 //
 657                                 // Try the implicit constant expression conversion
 658                                 // from long to ulong, instead of a nice routine,
 659                                 // we just inline it
 660                                 //
 661                                 long v = ((LongConstant) expr).Value;
 662                                 if (v > 0)
 663                                         return true;
 664                         }
 665
 666                         if ((target_type == TypeManager.enum_type ||
 667                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 668                              expr is IntLiteral){
 669                                 IntLiteral i = (IntLiteral) expr;
 670
 671                                 if (i.Value == 0)
 672                                         return true;
 673                         }
 674
 675                         //
 676                         // If `expr_type' implements `target_type' (which is an iface)
 677                         // see TryImplicitIntConversion
 678                         //
 679                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 680                                 return true;
 681
 682                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 683                                 return true;
 684
 685                         if (expr_type == TypeManager.anonymous_method_type){
 686                                 if (!TypeManager.IsDelegateType (target_type))
 687                                         return false;
 688
 689                                 AnonymousMethod am = (AnonymousMethod) expr;
 690
 691                                 Expression conv = am.Compatible (ec, target_type, true);
 692                                 if (conv != null)
 693                                         return true;
 694                         }
 695
 696                         return false;
 697                 }
 698
 699                 /// <summary>
 700                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 701                 ///  amongst the methods in the MethodGroupExpr
 702                 /// </summary>
 703                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 704                 {
 705                         Type best = null;
 706
 707                         EmptyExpression expr = EmptyExpression.Grab ();
 708
 709                         foreach (Type t in types) {
 710                                 if (best == null) {
 711                                         best = t;
 712                                         continue;
 713                                 }
 714
 715                                 expr.SetType (t);
 716                                 if (ImplicitStandardConversionExists (ec, expr, best))
 717                                         best = t;
 718                         }
 719
 720                         expr.SetType (best);
 721                         foreach (Type t in types) {
 722                                 if (best == t)
 723                                         continue;
 724                                 if (!ImplicitStandardConversionExists (ec, expr, t)) {
 725                                         best = null;
 726                                         break;
 727                                 }
 728                         }
 729
 730                         EmptyExpression.Release (expr);
 731
 732                         return best;
 733                 }
 734
 735                 /// <summary>
 736                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 737                 ///  amongst the types in the given set
 738                 /// </summary>
 739                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 740                 {
 741                         Type best = null;
 742
 743                         EmptyExpression expr = EmptyExpression.Grab ();
 744
 745                         foreach (Type t in types) {
 746                                 if (best == null) {
 747                                         best = t;
 748                                         continue;
 749                                 }
 750
 751                                 expr.SetType (best);
 752                                 if (ImplicitStandardConversionExists (ec, expr, t))
 753                                         best = t;
 754                         }
 755
 756                         foreach (Type t in types) {
 757                                 if (best == t)
 758                                         continue;
 759                                 expr.SetType (t);
 760                                 if (!ImplicitStandardConversionExists (ec, expr, best)) {
 761                                         best = null;
 762                                         break;
 763                                 }
 764                         }
 765
 766                         EmptyExpression.Release (expr);
 767
 768                         return best;
 769                 }
 770
 771                 /// <summary>
 772                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 773                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 774                 ///   for explicit and implicit conversion operators.
 775                 /// </summary>
 776                 static public Type FindMostSpecificSource (EmitContext ec, IList list,
 777                                                            Expression source, bool apply_explicit_conv_rules,
 778                                                            Location loc)
 779                 {
 780                         ArrayList src_types_set = new ArrayList ();
 781
 782                         //
 783                         // If any operator converts from S then Sx = S
 784                         //
 785                         Type source_type = source.Type;
 786                         foreach (MethodBase mb in list){
 787                                 ParameterData pd = TypeManager.GetParameterData (mb);
 788                                 Type param_type = pd.ParameterType (0);
 789
 790                                 if (param_type == source_type)
 791                                         return param_type;
 792
 793                                 src_types_set.Add (param_type);
 794                         }
 795
 796                         //
 797                         // Explicit Conv rules
 798                         //
 799                         if (apply_explicit_conv_rules) {
 800                                 ArrayList candidate_set = new ArrayList ();
 801
 802                                 foreach (Type param_type in src_types_set){
 803                                         if (ImplicitStandardConversionExists (ec, source, param_type))
 804                                                 candidate_set.Add (param_type);
 805                                 }
 806
 807                                 if (candidate_set.Count != 0)
 808                                         return FindMostEncompassedType (ec, candidate_set);
 809                         }
 810
 811                         //
 812                         // Final case
 813                         //
 814                         if (apply_explicit_conv_rules)
 815                                 return FindMostEncompassingType (ec, src_types_set);
 816                         else
 817                                 return FindMostEncompassedType (ec, src_types_set);
 818                 }
 819
 820                 /// <summary>
 821                 ///  Finds the most specific target Tx according to section 13.4.4
 822                 /// </summary>
 823                 static public Type FindMostSpecificTarget (EmitContext ec, IList list,
 824                                                            Type target, bool apply_explicit_conv_rules,
 825                                                            Location loc)
 826                 {
 827                         ArrayList tgt_types_set = new ArrayList ();
 828
 829                         //
 830                         // If any operator converts to T then Tx = T
 831                         //
 832                         foreach (MethodInfo mi in list){
 833                                 Type ret_type = mi.ReturnType;
 834                                 if (ret_type == target)
 835                                         return ret_type;
 836
 837                                 tgt_types_set.Add (ret_type);
 838                         }
 839
 840                         //
 841                         // Explicit conv rules
 842                         //
 843                         if (apply_explicit_conv_rules) {
 844                                 ArrayList candidate_set = new ArrayList ();
 845
 846                                 EmptyExpression expr = EmptyExpression.Grab ();
 847
 848                                 foreach (Type ret_type in tgt_types_set){
 849                                         expr.SetType (ret_type);
 850
 851                                         if (ImplicitStandardConversionExists (ec, expr, target))
 852                                                 candidate_set.Add (ret_type);
 853                                 }
 854
 855                                 EmptyExpression.Release (expr);
 856
 857                                 if (candidate_set.Count != 0)
 858                                         return FindMostEncompassingType (ec, candidate_set);
 859                         }
 860
 861                         //
 862                         // Okay, final case !
 863                         //
 864                         if (apply_explicit_conv_rules)
 865                                 return FindMostEncompassedType (ec, tgt_types_set);
 866                         else
 867                                 return FindMostEncompassingType (ec, tgt_types_set);
 868                 }
 869
 870                 /// <summary>
 871                 ///  User-defined Implicit conversions
 872                 /// </summary>
 873                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
 874                                                                  Type target, Location loc)
 875                 {
 876                         return UserDefinedConversion (ec, source, target, loc, false);
 877                 }
 878
 879                 /// <summary>
 880                 ///  User-defined Explicit conversions
 881                 /// </summary>
 882                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
 883                                                                  Type target, Location loc)
 884                 {
 885                         return UserDefinedConversion (ec, source, target, loc, true);
 886                 }
 887
 888                 static void AddConversionOperators (EmitContext ec, ArrayList list,
 889                                                     Expression source, Type target_type,
 890                                                     bool look_for_explicit,
 891                                                     MethodGroupExpr mg)
 892                 {
 893                         if (mg == null)
 894                                 return;
 895
 896                         Type source_type = source.Type;
 897                         EmptyExpression expr = EmptyExpression.Grab ();
 898                         foreach (MethodInfo m in mg.Methods) {
 899                                 ParameterData pd = TypeManager.GetParameterData (m);
 900                                 Type return_type = m.ReturnType;
 901                                 Type arg_type = pd.ParameterType (0);
 902
 903                                 if (source_type != arg_type) {
 904                                         if (!ImplicitStandardConversionExists (ec, source, arg_type)) {
 905                                                 if (!look_for_explicit)
 906                                                         continue;
 907                                                 expr.SetType (arg_type);
 908                                                 if (!ImplicitStandardConversionExists (ec, expr, source_type))
 909                                                         continue;
 910                                         }
 911                                 }
 912
 913                                 if (target_type != return_type) {
 914                                         expr.SetType (return_type);
 915                                         if (!ImplicitStandardConversionExists (ec, expr, target_type)) {
 916                                                 if (!look_for_explicit)
 917                                                         continue;
 918                                                 expr.SetType (target_type);
 919                                                 if (!ImplicitStandardConversionExists (ec, expr, return_type))
 920                                                         continue;
 921                                         }
 922                                 }
 923
 924                                 list.Add (m);
 925                         }
 926
 927                         EmptyExpression.Release (expr);
 928                 }
 929
 930                 /// <summary>
 931                 ///   Computes the list of the user-defined conversion
 932                 ///   operators from source_type to target_type.  `look_for_explicit'
 933                 ///   controls whether we should also include the list of explicit
 934                 ///   operators
 935                 /// </summary>
 936                 static IList GetConversionOperators (EmitContext ec,
 937                                                      Expression source, Type target_type,
 938                                                      Location loc, bool look_for_explicit)
 939                 {
 940                         ArrayList ret = new ArrayList (4);
 941
 942                         Type source_type = source.Type;
 943
 944                         if (source_type != TypeManager.decimal_type) {
 945                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 946                                         Expression.MethodLookup (
 947                                                 ec, source_type, "op_Implicit", loc) as MethodGroupExpr);
 948                                 if (look_for_explicit) {
 949                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 950                                                 Expression.MethodLookup (
 951                                                         ec, source_type, "op_Explicit", loc) as MethodGroupExpr);
 952                                 }
 953                         }
 954
 955                         if (target_type != TypeManager.decimal_type) {
 956                                 AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 957                                         Expression.MethodLookup (
 958                                                 ec, target_type, "op_Implicit", loc) as MethodGroupExpr);
 959                                 if (look_for_explicit) {
 960                                         AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
 961                                                 Expression.MethodLookup (
 962                                                         ec, target_type, "op_Explicit", loc) as MethodGroupExpr);
 963                                 }
 964                         }
 965
 966                         return ret;
 967                 }
 968
 969                 static DoubleHash explicit_conv = new DoubleHash (100);
 970                 static DoubleHash implicit_conv = new DoubleHash (100);
 971
 972                 /// <summary>
 973                 ///   User-defined conversions
 974                 /// </summary>
 975                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
 976                                                                 Type target, Location loc,
 977                                                                 bool look_for_explicit)
 978                 {
 979                         Type source_type = source.Type;
 980                         MethodInfo method = null;
 981                         Type most_specific_source = null;
 982                         Type most_specific_target = null;
 983
 984                         object o;
 985                         DoubleHash hash = look_for_explicit ? explicit_conv : implicit_conv;
 986
 987                         if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
 988                                 method = (MethodInfo) o;
 989                                 if (method != null) {
 990                                         ParameterData pd = TypeManager.GetParameterData (method);
 991                                         most_specific_source = pd.ParameterType (0);
 992                                         most_specific_target = method.ReturnType;
 993                                 }
 994                         } else {
 995                                 IList ops = GetConversionOperators (ec, source, target, loc, look_for_explicit);
 996                                 if (ops == null || ops.Count == 0) {
 997                                         method = null;
 998                                         goto skip;
 999                                 }
1000
1001                                 most_specific_source = FindMostSpecificSource (ec, ops, source, look_for_explicit, loc);
1002                                 if (most_specific_source == null) {
1003                                         method = null;
1004                                         goto skip;
1005                                 }
1006
1007                                 most_specific_target = FindMostSpecificTarget (ec, ops, target, look_for_explicit, loc);
1008                                 if (most_specific_target == null) {
1009                                         method = null;
1010                                         goto skip;
1011                                 }
1012
1013                                 int count = 0;
1014
1015                                 foreach (MethodInfo m in ops) {
1016                                         ParameterData pd = TypeManager.GetParameterData (m);
1017
1018                                         if (pd.ParameterType (0) == most_specific_source &&
1019                                             m.ReturnType == most_specific_target) {
1020                                                 method = m;
1021                                                 count++;
1022                                         }
1023                                 }
1024                                 if (count > 1)
1025                                         method = null;
1026
1027                         skip:
1028                                 if (!(source is Constant))
1029                                         hash.Insert (source_type, target, method);
1030                         }
1031
1032                         if (method == null)
1033                                 return null;
1034
1035                         //
1036                         // This will do the conversion to the best match that we
1037                         // found.  Now we need to perform an implict standard conversion
1038                         // if the best match was not the type that we were requested
1039                         // by target.
1040                         //
1041                         if (look_for_explicit)
1042                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1043                         else
1044                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1045
1046                         if (source == null)
1047                                 return null;
1048
1049                         Expression e;
1050                         e =  new UserCast (method, source, loc);
1051                         if (e.Type != target){
1052                                 if (!look_for_explicit)
1053                                         e = ImplicitConversionStandard (ec, e, target, loc);
1054                                 else
1055                                         e = ExplicitConversionStandard (ec, e, target, loc);
1056                         }
1057
1058                         return e;
1059                 }
1060
1061                 /// <summary>
1062                 ///   Converts implicitly the resolved expression `expr' into the
1063                 ///   `target_type'.  It returns a new expression that can be used
1064                 ///   in a context that expects a `target_type'.
1065                 /// </summary>
1066                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1067                                                              Type target_type, Location loc)
1068                 {
1069                         Expression e;
1070
1071                         if (target_type == null)
1072                                 throw new Exception ("Target type is null");
1073
1074                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1075                         if (e != null)
1076                                 return e;
1077
1078                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1079                         if (e != null)
1080                                 return e;
1081
1082                         return null;
1083                 }
1084
1085
1086                 /// <summary>
1087                 ///   Attempts to apply the `Standard Implicit
1088                 ///   Conversion' rules to the expression `expr' into
1089                 ///   the `target_type'.  It returns a new expression
1090                 ///   that can be used in a context that expects a
1091                 ///   `target_type'.
1092                 ///
1093                 ///   This is different from `ImplicitConversion' in that the
1094                 ///   user defined implicit conversions are excluded.
1095                 /// </summary>
1096                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1097                                                                      Type target_type, Location loc)
1098                 {
1099                         Type expr_type = expr.Type;
1100                         Expression e;
1101
1102                         if (expr.eclass == ExprClass.MethodGroup){
1103                                 if (!TypeManager.IsDelegateType (target_type)){
1104                                         return null;
1105                                 }
1106
1107                                 //
1108                                 // Only allow anonymous method conversions on post ISO_1
1109                                 //
1110                                 if (RootContext.Version != LanguageVersion.ISO_1){
1111                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1112                                         if (mg != null)
1113                                                 return ImplicitDelegateCreation.Create (
1114                                                         ec, mg, target_type, false, loc);
1115                                 }
1116                         }
1117
1118                         if (expr_type == target_type && expr_type != TypeManager.null_type)
1119                                 return expr;
1120
1121                         e = ImplicitNumericConversion (ec, expr, target_type, loc);
1122                         if (e != null)
1123                                 return e;
1124
1125                         e = ImplicitReferenceConversion (expr, target_type);
1126                         if (e != null)
1127                                 return e;
1128
1129                         if ((target_type == TypeManager.enum_type ||
1130                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1131                             expr is IntLiteral){
1132                                 IntLiteral i = (IntLiteral) expr;
1133
1134                                 if (i.Value == 0)
1135                                         return new EnumConstant ((Constant) expr, target_type);
1136                         }
1137
1138                         if (ec.InUnsafe) {
1139                                 if (expr_type.IsPointer){
1140                                         if (target_type == TypeManager.void_ptr_type)
1141                                                 return new EmptyCast (expr, target_type);
1142
1143                                         //
1144                                         // yep, comparing pointer types cant be done with
1145                                         // t1 == t2, we have to compare their element types.
1146                                         //
1147                                         if (target_type.IsPointer){
1148                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1149                                                         return expr;
1150                                         }
1151                                 }
1152
1153                                 if (target_type.IsPointer) {
1154                                         if (expr_type == TypeManager.null_type)
1155                                                 return new EmptyCast (NullPointer.Null, target_type);
1156
1157                                         if (expr_type == TypeManager.void_ptr_type)
1158                                                 return new EmptyCast (expr, target_type);
1159                                 }
1160                         }
1161
1162                         if (expr_type == TypeManager.anonymous_method_type){
1163                                 if (!TypeManager.IsDelegateType (target_type)){
1164                                         Report.Error (1660, loc,
1165                                                               "Cannot convert anonymous method to `{0}', since it is not a delegate",
1166                                                               TypeManager.CSharpName (target_type));
1167                                         return null;
1168                                 }
1169
1170                                 AnonymousMethod am = (AnonymousMethod) expr;
1171                                 int errors = Report.Errors;
1172
1173                                 Expression conv = am.Compatible (ec, target_type, false);
1174                                 if (conv != null)
1175                                         return conv;
1176
1177                                 //
1178                                 // We return something instead of null, to avoid
1179                                 // the duplicate error, since am.Compatible would have
1180                                 // reported that already
1181                                 //
1182                                 if (errors != Report.Errors)
1183                                         return new EmptyCast (expr, target_type);
1184                         }
1185
1186                         return null;
1187                 }
1188
1189                 /// <summary>
1190                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1191                 ///   into a different data type using casts (See Implicit Constant
1192                 ///   Expression Conversions)
1193                 /// </summary>
1194                 static public Expression TryImplicitIntConversion (Type target_type, IntConstant ic)
1195                 {
1196                         int value = ic.Value;
1197
1198                         if (target_type == TypeManager.sbyte_type){
1199                                 if (value >= SByte.MinValue && value <= SByte.MaxValue)
1200                                         return new SByteConstant ((sbyte) value);
1201                         } else if (target_type == TypeManager.byte_type){
1202                                 if (value >= Byte.MinValue && value <= Byte.MaxValue)
1203                                         return new ByteConstant ((byte) value);
1204                         } else if (target_type == TypeManager.short_type){
1205                                 if (value >= Int16.MinValue && value <= Int16.MaxValue)
1206                                         return new ShortConstant ((short) value);
1207                         } else if (target_type == TypeManager.ushort_type){
1208                                 if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
1209                                         return new UShortConstant ((ushort) value);
1210                         } else if (target_type == TypeManager.uint32_type){
1211                                 if (value >= 0)
1212                                         return new UIntConstant ((uint) value);
1213                         } else if (target_type == TypeManager.uint64_type){
1214                                 //
1215                                 // we can optimize this case: a positive int32
1216                                 // always fits on a uint64.  But we need an opcode
1217                                 // to do it.
1218                                 //
1219                                 if (value >= 0)
1220                                         return new ULongConstant ((ulong) value);
1221                         } else if (target_type == TypeManager.double_type)
1222                                 return new DoubleConstant ((double) value);
1223                         else if (target_type == TypeManager.float_type)
1224                                 return new FloatConstant ((float) value);
1225
1226                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1227                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1228                                 Constant e = (Constant) ic;
1229
1230                                 //
1231                                 // Possibly, we need to create a different 0 literal before passing
1232                                 // to EnumConstant
1233                                 //
1234                                 if (underlying == TypeManager.int64_type)
1235                                         e = new LongLiteral (0);
1236                                 else if (underlying == TypeManager.uint64_type)
1237                                         e = new ULongLiteral (0);
1238
1239                                 return new EnumConstant (e, target_type);
1240                         }
1241
1242                         //
1243                         // If `target_type' is an interface and the type of `ic' implements the interface
1244                         // e.g. target_type is IComparable, IConvertible, IFormattable
1245                         //
1246                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1247                                 return new BoxedCast (ic);
1248
1249                         return null;
1250                 }
1251
1252                 static public void Error_CannotImplicitConversion (Location loc, Type source, Type target)
1253                 {
1254                         if (source.Name == target.Name){
1255                                 Report.ExtraInformation (loc,
1256                                          String.Format (
1257                                                 "The type {0} has two conflicting definitions, one comes from {1} and the other from {2}",
1258                                                 source.Name, source.Assembly.FullName, target.Assembly.FullName));
1259
1260                         }
1261                         Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
1262                                       source == TypeManager.anonymous_method_type ?
1263                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1264                                       TypeManager.CSharpName (target));
1265                 }
1266
1267                 /// <summary>
1268                 ///   Attempts to implicitly convert `source' into `target_type', using
1269                 ///   ImplicitConversion.  If there is no implicit conversion, then
1270                 ///   an error is signaled
1271                 /// </summary>
1272                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1273                                                                      Type target_type, Location loc)
1274                 {
1275                         Expression e;
1276
1277                         e = ImplicitConversion (ec, source, target_type, loc);
1278                         if (e != null)
1279                                 return e;
1280
1281                         if (source is DoubleLiteral) {
1282                                 if (target_type == TypeManager.float_type) {
1283                                         Error_664 (loc, "float", "f");
1284                                         return null;
1285                                 }
1286                                 if (target_type == TypeManager.decimal_type) {
1287                                         Error_664 (loc, "decimal", "m");
1288                                         return null;
1289                                 }
1290                         }
1291
1292                         if (source is Constant){
1293                                 Constant c = (Constant) source;
1294
1295                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1296                                 return null;
1297                         }
1298
1299                         Error_CannotImplicitConversion (loc, source.Type, target_type);
1300
1301                         return null;
1302                 }
1303
1304                 static void Error_664 (Location loc, string type, string suffix) {
1305                         Report.Error (664, loc,
1306                                 "Literal of type double cannot be implicitly converted to type '{0}'. Add suffix '{1}' to create a literal of this type",
1307                                 type, suffix);
1308                 }
1309
1310                 /// <summary>
1311                 ///   Performs the explicit numeric conversions
1312                 /// </summary>
1313                 static Expression ExplicitNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1314                 {
1315                         Type expr_type = expr.Type;
1316
1317                         //
1318                         // If we have an enumeration, extract the underlying type,
1319                         // use this during the comparison, but wrap around the original
1320                         // target_type
1321                         //
1322                         Type real_target_type = target_type;
1323
1324                         if (TypeManager.IsEnumType (real_target_type))
1325                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1326
1327                         if (ImplicitStandardConversionExists (ec, expr, real_target_type)){
1328                                 Expression ce = ImplicitConversionStandard (ec, expr, real_target_type, loc);
1329
1330                                 if (real_target_type != target_type)
1331                                         return new EmptyCast (ce, target_type);
1332                                 return ce;
1333                         }
1334
1335                         if (expr_type == TypeManager.sbyte_type){
1336                                 //
1337                                 // From sbyte to byte, ushort, uint, ulong, char
1338                                 //
1339                                 if (real_target_type == TypeManager.byte_type)
1340                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1341                                 if (real_target_type == TypeManager.ushort_type)
1342                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1343                                 if (real_target_type == TypeManager.uint32_type)
1344                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1345                                 if (real_target_type == TypeManager.uint64_type)
1346                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1347                                 if (real_target_type == TypeManager.char_type)
1348                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1349                         } else if (expr_type == TypeManager.byte_type){
1350                                 //
1351                                 // From byte to sbyte and char
1352                                 //
1353                                 if (real_target_type == TypeManager.sbyte_type)
1354                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1355                                 if (real_target_type == TypeManager.char_type)
1356                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_CH);
1357                         } else if (expr_type == TypeManager.short_type){
1358                                 //
1359                                 // From short to sbyte, byte, ushort, uint, ulong, char
1360                                 //
1361                                 if (real_target_type == TypeManager.sbyte_type)
1362                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1363                                 if (real_target_type == TypeManager.byte_type)
1364                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1365                                 if (real_target_type == TypeManager.ushort_type)
1366                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1367                                 if (real_target_type == TypeManager.uint32_type)
1368                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1369                                 if (real_target_type == TypeManager.uint64_type)
1370                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1371                                 if (real_target_type == TypeManager.char_type)
1372                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_CH);
1373                         } else if (expr_type == TypeManager.ushort_type){
1374                                 //
1375                                 // From ushort to sbyte, byte, short, char
1376                                 //
1377                                 if (real_target_type == TypeManager.sbyte_type)
1378                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1379                                 if (real_target_type == TypeManager.byte_type)
1380                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1381                                 if (real_target_type == TypeManager.short_type)
1382                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1383                                 if (real_target_type == TypeManager.char_type)
1384                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1385                         } else if (expr_type == TypeManager.int32_type){
1386                                 //
1387                                 // From int to sbyte, byte, short, ushort, uint, ulong, char
1388                                 //
1389                                 if (real_target_type == TypeManager.sbyte_type)
1390                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1391                                 if (real_target_type == TypeManager.byte_type)
1392                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1393                                 if (real_target_type == TypeManager.short_type)
1394                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1395                                 if (real_target_type == TypeManager.ushort_type)
1396                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1397                                 if (real_target_type == TypeManager.uint32_type)
1398                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1399                                 if (real_target_type == TypeManager.uint64_type)
1400                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1401                                 if (real_target_type == TypeManager.char_type)
1402                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_CH);
1403                         } else if (expr_type == TypeManager.uint32_type){
1404                                 //
1405                                 // From uint to sbyte, byte, short, ushort, int, char
1406                                 //
1407                                 if (real_target_type == TypeManager.sbyte_type)
1408                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1409                                 if (real_target_type == TypeManager.byte_type)
1410                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1411                                 if (real_target_type == TypeManager.short_type)
1412                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1413                                 if (real_target_type == TypeManager.ushort_type)
1414                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1415                                 if (real_target_type == TypeManager.int32_type)
1416                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1417                                 if (real_target_type == TypeManager.char_type)
1418                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1419                         } else if (expr_type == TypeManager.int64_type){
1420                                 //
1421                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1422                                 //
1423                                 if (real_target_type == TypeManager.sbyte_type)
1424                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1425                                 if (real_target_type == TypeManager.byte_type)
1426                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1427                                 if (real_target_type == TypeManager.short_type)
1428                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1429                                 if (real_target_type == TypeManager.ushort_type)
1430                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1431                                 if (real_target_type == TypeManager.int32_type)
1432                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1433                                 if (real_target_type == TypeManager.uint32_type)
1434                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1435                                 if (real_target_type == TypeManager.uint64_type)
1436                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1437                                 if (real_target_type == TypeManager.char_type)
1438                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_CH);
1439                         } else if (expr_type == TypeManager.uint64_type){
1440                                 //
1441                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1442                                 //
1443                                 if (real_target_type == TypeManager.sbyte_type)
1444                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1445                                 if (real_target_type == TypeManager.byte_type)
1446                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1447                                 if (real_target_type == TypeManager.short_type)
1448                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1449                                 if (real_target_type == TypeManager.ushort_type)
1450                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1451                                 if (real_target_type == TypeManager.int32_type)
1452                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1453                                 if (real_target_type == TypeManager.uint32_type)
1454                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1455                                 if (real_target_type == TypeManager.int64_type)
1456                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1457                                 if (real_target_type == TypeManager.char_type)
1458                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1459                         } else if (expr_type == TypeManager.char_type){
1460                                 //
1461                                 // From char to sbyte, byte, short
1462                                 //
1463                                 if (real_target_type == TypeManager.sbyte_type)
1464                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I1);
1465                                 if (real_target_type == TypeManager.byte_type)
1466                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_U1);
1467                                 if (real_target_type == TypeManager.short_type)
1468                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.CH_I2);
1469                         } else if (expr_type == TypeManager.float_type){
1470                                 //
1471                                 // From float to sbyte, byte, short,
1472                                 // ushort, int, uint, long, ulong, char
1473                                 // or decimal
1474                                 //
1475                                 if (real_target_type == TypeManager.sbyte_type)
1476                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1477                                 if (real_target_type == TypeManager.byte_type)
1478                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U1);
1479                                 if (real_target_type == TypeManager.short_type)
1480                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I2);
1481                                 if (real_target_type == TypeManager.ushort_type)
1482                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1483                                 if (real_target_type == TypeManager.int32_type)
1484                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I4);
1485                                 if (real_target_type == TypeManager.uint32_type)
1486                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1487                                 if (real_target_type == TypeManager.int64_type)
1488                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I8);
1489                                 if (real_target_type == TypeManager.uint64_type)
1490                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1491                                 if (real_target_type == TypeManager.char_type)
1492                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
1493                                 if (real_target_type == TypeManager.decimal_type)
1494                                         return new CastToDecimal (ec, expr, true);
1495                         } else if (expr_type == TypeManager.double_type){
1496                                 //
1497                                 // From double to sbyte, byte, short,
1498                                 // ushort, int, uint, long, ulong,
1499                                 // char, float or decimal
1500                                 //
1501                                 if (real_target_type == TypeManager.sbyte_type)
1502                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1503                                 if (real_target_type == TypeManager.byte_type)
1504                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1505                                 if (real_target_type == TypeManager.short_type)
1506                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1507                                 if (real_target_type == TypeManager.ushort_type)
1508                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1509                                 if (real_target_type == TypeManager.int32_type)
1510                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1511                                 if (real_target_type == TypeManager.uint32_type)
1512                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1513                                 if (real_target_type == TypeManager.int64_type)
1514                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1515                                 if (real_target_type == TypeManager.uint64_type)
1516                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1517                                 if (real_target_type == TypeManager.char_type)
1518                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
1519                                 if (real_target_type == TypeManager.float_type)
1520                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1521                                 if (real_target_type == TypeManager.decimal_type)
1522                                         return new CastToDecimal (ec, expr, true);
1523                         } else if (expr_type == TypeManager.decimal_type) {
1524                                 //
1525                                 // From decimal to sbyte, byte, short, ushort, int, uint,
1526                                 // long, ulong, char, double or float
1527                                 //
1528                                 if (real_target_type == TypeManager.sbyte_type ||
1529                                     real_target_type == TypeManager.byte_type ||
1530                                     real_target_type == TypeManager.short_type ||
1531                                     real_target_type == TypeManager.ushort_type ||
1532                                     real_target_type == TypeManager.int32_type ||
1533                                     real_target_type == TypeManager.uint32_type ||
1534                                     real_target_type == TypeManager.int64_type ||
1535                                     real_target_type == TypeManager.uint64_type ||
1536                                     real_target_type == TypeManager.char_type ||
1537                                     real_target_type == TypeManager.double_type ||
1538                                     real_target_type == TypeManager.float_type)
1539                                         return new CastFromDecimal (ec, expr, target_type);
1540                         }
1541                         return null;
1542                 }
1543
1544                 /// <summary>
1545                 ///  Returns whether an explicit reference conversion can be performed
1546                 ///  from source_type to target_type
1547                 /// </summary>
1548                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1549                 {
1550                         bool target_is_value_type = target_type.IsValueType;
1551
1552                         if (source_type == target_type)
1553                                 return true;
1554
1555                         //
1556                         // From object to any reference type
1557                         //
1558                         if (source_type == TypeManager.object_type && !target_is_value_type)
1559                                 return true;
1560
1561                         //
1562                         // From any class S to any class-type T, provided S is a base class of T
1563                         //
1564                         if (target_type.IsSubclassOf (source_type))
1565                                 return true;
1566
1567                         //
1568                         // From any interface type S to any interface T provided S is not derived from T
1569                         //
1570                         if (source_type.IsInterface && target_type.IsInterface){
1571                                 if (!target_type.IsSubclassOf (source_type))
1572                                         return true;
1573                         }
1574
1575                         //
1576                         // From any class type S to any interface T, provided S is not sealed
1577                         // and provided S does not implement T.
1578                         //
1579                         if (target_type.IsInterface && !source_type.IsSealed &&
1580                             !TypeManager.ImplementsInterface (source_type, target_type))
1581                                 return true;
1582
1583                         //
1584                         // From any interface-type S to to any class type T, provided T is not
1585                         // sealed, or provided T implements S.
1586                         //
1587                         if (source_type.IsInterface &&
1588                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1589                                 return true;
1590
1591
1592                         // From an array type S with an element type Se to an array type T with an
1593                         // element type Te provided all the following are true:
1594                         //     * S and T differe only in element type, in other words, S and T
1595                         //       have the same number of dimensions.
1596                         //     * Both Se and Te are reference types
1597                         //     * An explicit referenc conversions exist from Se to Te
1598                         //
1599                         if (source_type.IsArray && target_type.IsArray) {
1600                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1601
1602                                         Type source_element_type = TypeManager.GetElementType (source_type);
1603                                         Type target_element_type = TypeManager.GetElementType (target_type);
1604
1605                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1606                                                 if (ExplicitReferenceConversionExists (source_element_type,
1607                                                                                        target_element_type))
1608                                                         return true;
1609                                 }
1610                         }
1611
1612
1613                         // From System.Array to any array-type
1614                         if (source_type == TypeManager.array_type &&
1615                             target_type.IsArray){
1616                                 return true;
1617                         }
1618
1619                         //
1620                         // From System delegate to any delegate-type
1621                         //
1622                         if (source_type == TypeManager.delegate_type &&
1623                             target_type.IsSubclassOf (TypeManager.delegate_type))
1624                                 return true;
1625
1626                         //
1627                         // From ICloneable to Array or Delegate types
1628                         //
1629                         if (source_type == TypeManager.icloneable_type &&
1630                             (target_type == TypeManager.array_type ||
1631                              target_type == TypeManager.delegate_type))
1632                                 return true;
1633
1634                         return false;
1635                 }
1636
1637                 /// <summary>
1638                 ///   Implements Explicit Reference conversions
1639                 /// </summary>
1640                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1641                 {
1642                         Type source_type = source.Type;
1643                         bool target_is_value_type = target_type.IsValueType;
1644
1645                         //
1646                         // From object to any reference type
1647                         //
1648                         if (source_type == TypeManager.object_type && !target_is_value_type)
1649                                 return new ClassCast (source, target_type);
1650
1651                         //
1652                         // Unboxing conversion.
1653                         //
1654                         if (((source_type == TypeManager.enum_type &&
1655                                 !(source is EmptyCast)) ||
1656                                 source_type == TypeManager.value_type) && target_is_value_type)
1657                                 return new UnboxCast (source, target_type);
1658
1659                         //
1660                         // From any class S to any class-type T, provided S is a base class of T
1661                         //
1662                         if (target_type.IsSubclassOf (source_type))
1663                                 return new ClassCast (source, target_type);
1664
1665                         //
1666                         // From any interface type S to any interface T provided S is not derived from T
1667                         //
1668                         if (source_type.IsInterface && target_type.IsInterface){
1669                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1670                                         return null;
1671                                 else
1672                                         return new ClassCast (source, target_type);
1673                         }
1674
1675                         //
1676                         // From any class type S to any interface T, provides S is not sealed
1677                         // and provided S does not implement T.
1678                         //
1679                         if (target_type.IsInterface && !source_type.IsSealed) {
1680                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1681                                         return null;
1682                                 else
1683                                         return new ClassCast (source, target_type);
1684
1685                         }
1686
1687                         //
1688                         // From any interface-type S to to any class type T, provided T is not
1689                         // sealed, or provided T implements S.
1690                         //
1691                         if (source_type.IsInterface) {
1692                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1693                                         if (target_type.IsClass)
1694                                                 return new ClassCast (source, target_type);
1695                                         else
1696                                                 return new UnboxCast (source, target_type);
1697                                 }
1698
1699                                 return null;
1700                         }
1701
1702                         // From an array type S with an element type Se to an array type T with an
1703                         // element type Te provided all the following are true:
1704                         //     * S and T differe only in element type, in other words, S and T
1705                         //       have the same number of dimensions.
1706                         //     * Both Se and Te are reference types
1707                         //     * An explicit referenc conversions exist from Se to Te
1708                         //
1709                         if (source_type.IsArray && target_type.IsArray) {
1710                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1711
1712                                         Type source_element_type = TypeManager.GetElementType (source_type);
1713                                         Type target_element_type = TypeManager.GetElementType (target_type);
1714
1715                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1716                                                 if (ExplicitReferenceConversionExists (source_element_type,
1717                                                                                        target_element_type))
1718                                                         return new ClassCast (source, target_type);
1719                                 }
1720                         }
1721
1722
1723                         // From System.Array to any array-type
1724                         if (source_type == TypeManager.array_type &&
1725                             target_type.IsArray) {
1726                                 return new ClassCast (source, target_type);
1727                         }
1728
1729                         //
1730                         // From System delegate to any delegate-type
1731                         //
1732                         if (source_type == TypeManager.delegate_type &&
1733                             target_type.IsSubclassOf (TypeManager.delegate_type))
1734                                 return new ClassCast (source, target_type);
1735
1736                         //
1737                         // From ICloneable to Array or Delegate types
1738                         //
1739                         if (source_type == TypeManager.icloneable_type &&
1740                             (target_type == TypeManager.array_type ||
1741                              target_type == TypeManager.delegate_type))
1742                                 return new ClassCast (source, target_type);
1743
1744                         return null;
1745                 }
1746
1747                 /// <summary>
1748                 ///   Performs an explicit conversion of the expression `expr' whose
1749                 ///   type is expr.Type to `target_type'.
1750                 /// </summary>
1751                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
1752                                                              Type target_type, Location loc)
1753                 {
1754                         Type expr_type = expr.Type;
1755                         Type original_expr_type = expr_type;
1756
1757                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
1758                                 if (target_type == TypeManager.enum_type ||
1759                                     target_type == TypeManager.object_type) {
1760                                         if (expr is EnumConstant)
1761                                                 expr = ((EnumConstant) expr).Child;
1762                                         // We really need all these casts here .... :-(
1763                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
1764                                         return new EmptyCast (expr, target_type);
1765                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
1766                                            target_type.IsSubclassOf (TypeManager.enum_type))
1767                                         return new UnboxCast (expr, target_type);
1768
1769                                 //
1770                                 // Notice that we have kept the expr_type unmodified, which is only
1771                                 // used later on to
1772                                 if (expr is EnumConstant)
1773                                         expr = ((EnumConstant) expr).Child;
1774                                 else
1775                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
1776                                 expr_type = expr.Type;
1777                         }
1778
1779                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc);
1780
1781                         if (ne != null)
1782                                 return ne;
1783
1784                         ne = ExplicitNumericConversion (ec, expr, target_type, loc);
1785                         if (ne != null)
1786                                 return ne;
1787
1788                         //
1789                         // Unboxing conversion.
1790                         //
1791                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1792                                 return new UnboxCast (expr, target_type);
1793
1794                         //
1795                         // Skip the ExplicitReferenceConversion because we can not convert
1796                         // from Null to a ValueType, and ExplicitReference wont check against
1797                         // null literal explicitly
1798                         //
1799                         if (expr_type != TypeManager.null_type){
1800                                 ne = ExplicitReferenceConversion (expr, target_type);
1801                                 if (ne != null)
1802                                         return ne;
1803                         }
1804
1805                         if (ec.InUnsafe){
1806                                 if (target_type.IsPointer){
1807                                         if (expr_type.IsPointer)
1808                                                 return new EmptyCast (expr, target_type);
1809
1810                                         if (expr_type == TypeManager.sbyte_type ||
1811                                             expr_type == TypeManager.short_type ||
1812                                             expr_type == TypeManager.int32_type ||
1813                                             expr_type == TypeManager.int64_type)
1814                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
1815
1816                                         if (expr_type == TypeManager.ushort_type ||
1817                                             expr_type == TypeManager.uint32_type ||
1818                                             expr_type == TypeManager.uint64_type ||
1819                                             expr_type == TypeManager.byte_type)
1820                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
1821                                 }
1822                                 if (expr_type.IsPointer){
1823                                         Expression e = null;
1824
1825                                         if (target_type == TypeManager.sbyte_type)
1826                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
1827                                         else if (target_type == TypeManager.byte_type)
1828                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
1829                                         else if (target_type == TypeManager.short_type)
1830                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
1831                                         else if (target_type == TypeManager.ushort_type)
1832                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
1833                                         else if (target_type == TypeManager.int32_type)
1834                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
1835                                         else if (target_type == TypeManager.uint32_type)
1836                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
1837                                         else if (target_type == TypeManager.uint64_type)
1838                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
1839                                         else if (target_type == TypeManager.int64_type){
1840                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
1841                                         }
1842
1843                                         if (e != null){
1844                                                 Expression ci, ce;
1845
1846                                                 ci = ImplicitConversionStandard (ec, e, target_type, loc);
1847
1848                                                 if (ci != null)
1849                                                         return ci;
1850
1851                                                 ce = ExplicitNumericConversion (ec, e, target_type, loc);
1852                                                 if (ce != null)
1853                                                         return ce;
1854                                                 //
1855                                                 // We should always be able to go from an uint32
1856                                                 // implicitly or explicitly to the other integral
1857                                                 // types
1858                                                 //
1859                                                 throw new Exception ("Internal compiler error");
1860                                         }
1861                                 }
1862                         }
1863
1864                         ne = ExplicitUserConversion (ec, expr, target_type, loc);
1865                         if (ne != null)
1866                                 return ne;
1867
1868                         if (expr is NullLiteral){
1869                                 Report.Error (37, loc, "Cannot convert null to value type `" +
1870                                               TypeManager.CSharpName (target_type) + "'");
1871                                 return null;
1872                         }
1873
1874                         Error_CannotConvertType (loc, original_expr_type, target_type);
1875                         return null;
1876                 }
1877
1878                 /// <summary>
1879                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
1880                 /// </summary>
1881                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
1882                                                                   Type target_type, Location l)
1883                 {
1884                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
1885
1886                         if (ne != null)
1887                                 return ne;
1888
1889                         ne = ExplicitNumericConversion (ec, expr, target_type, l);
1890                         if (ne != null)
1891                                 return ne;
1892
1893                         ne = ExplicitReferenceConversion (expr, target_type);
1894                         if (ne != null)
1895                                 return ne;
1896
1897                         Error_CannotConvertType (l, expr.Type, target_type);
1898                         return null;
1899                 }
1900         }
1901 }