mcs/mcs/convert.cs

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