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 //   Marek Safar (marek.safar@gmail.com)
   8 //
   9 // Copyright 2001, 2002, 2003 Ximian, Inc.
  10 // Copyright 2003-2008 Novell, Inc.
  11 //
  12
  13 namespace Mono.CSharp {
  14         using System;
  15         using System.Collections;
  16         using System.Diagnostics;
  17         using System.Reflection;
  18         using System.Reflection.Emit;
  19
  20         //
  21         // A container class for all the conversion operations
  22         //
  23         public class Convert {
  24 #if GMCS_SOURCE
  25                 static bool TypeParameter_to_Null (Type target_type)
  26                 {
  27                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (target_type);
  28                         if (gc == null)
  29                                 return false;
  30
  31                         if (gc.HasReferenceTypeConstraint)
  32                                 return true;
  33                         if (gc.HasClassConstraint && !TypeManager.IsValueType (gc.ClassConstraint))
  34                                 return true;
  35
  36                         return false;
  37                 }
  38
  39                 static Type TypeParam_EffectiveBaseType (GenericConstraints gc)
  40                 {
  41                         ArrayList list = new ArrayList ();
  42                         list.Add (gc.EffectiveBaseClass);
  43                         foreach (Type t in gc.InterfaceConstraints) {
  44                                 if (!TypeManager.IsGenericParameter (t))
  45                                         continue;
  46
  47                                 GenericConstraints new_gc = TypeManager.GetTypeParameterConstraints (t);
  48                                 if (new_gc != null)
  49                                         list.Add (TypeParam_EffectiveBaseType (new_gc));
  50                         }
  51                         return FindMostEncompassedType (list);
  52                 }
  53 #endif
  54
  55                 //
  56                 // From a one-dimensional array-type S[] to System.Collections.IList<S> and base
  57                 // interfaces of this interface.
  58                 //
  59                 // From a one-dimensional array-type S[] to System.Collections.IList<T> and base
  60                 // interfaces of this interface, provided there is an implicit reference conversion
  61                 // from S to T.
  62                 //
  63                 static bool Array_To_IList (Type array, Type list)
  64                 {
  65 #if GMCS_SOURCE
  66                         if (!array.IsArray || (array.GetArrayRank () != 1) || !list.IsGenericType)
  67                                 return false;
  68
  69                         Type gt = list.GetGenericTypeDefinition ();
  70                         if ((gt != TypeManager.generic_ilist_type) &&
  71                             (gt != TypeManager.generic_icollection_type) &&
  72                             (gt != TypeManager.generic_ienumerable_type))
  73                                 return false;
  74
  75                         Type element_type = TypeManager.GetElementType (array);
  76                         Type arg_type = TypeManager.GetTypeArguments (list) [0];
  77
  78                         if (element_type == arg_type)
  79                                 return true;
  80
  81                         if (MyEmptyExpr == null)
  82                                 MyEmptyExpr = new EmptyExpression ();
  83                         MyEmptyExpr.SetType (TypeManager.GetElementType (array));
  84
  85                         return ImplicitReferenceConversionCore (MyEmptyExpr, arg_type);
  86 #else
  87                         return false;
  88 #endif
  89                 }
  90
  91                 static bool IList_To_Array(Type list, Type array)
  92                 {
  93 # if GMCS_SOURCE
  94                         if (!list.IsGenericType || !array.IsArray || array.GetArrayRank() != 1)
  95                                 return false;
  96
  97                         Type gt = list.GetGenericTypeDefinition();
  98                         if (gt != TypeManager.generic_ilist_type &&
  99                                 gt != TypeManager.generic_icollection_type &&
 100                                 gt != TypeManager.generic_ienumerable_type)
 101                                 return false;
 102
 103                         Type arg_type = TypeManager.GetTypeArguments(list)[0];
 104                         Type element_type = TypeManager.GetElementType(array);
 105
 106                         if (element_type == arg_type)
 107                                 return true;
 108
 109                         if (MyEmptyExpr == null)
 110                                 MyEmptyExpr = new EmptyExpression();
 111                         MyEmptyExpr.SetType(element_type);
 112                         return ImplicitReferenceConversionExists(MyEmptyExpr, arg_type) || ExplicitReferenceConversionExists(element_type, arg_type);
 113 #else
 114                         return false;
 115 #endif
 116                 }
 117
 118                 static Expression ImplicitTypeParameterConversion (Expression expr,
 119                                                                    Type target_type)
 120                 {
 121 #if GMCS_SOURCE
 122                         Type expr_type = expr.Type;
 123
 124                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (expr_type);
 125
 126                         if (gc == null) {
 127                                 if (target_type == TypeManager.object_type)
 128                                         return new BoxedCast (expr, target_type);
 129
 130                                 return null;
 131                         }
 132
 133                         // We're converting from a type parameter which is known to be a reference type.
 134                         Type base_type = TypeParam_EffectiveBaseType (gc);
 135
 136                         if (TypeManager.IsSubclassOf (base_type, target_type))
 137                                 return new ClassCast (expr, target_type);
 138
 139                         if (target_type.IsInterface) {
 140                                 if (TypeManager.ImplementsInterface (base_type, target_type))
 141                                         return new ClassCast (expr, target_type);
 142
 143                                 foreach (Type t in gc.InterfaceConstraints) {
 144                                         if (TypeManager.IsSubclassOf (t, target_type))
 145                                                 return new ClassCast (expr, target_type);
 146                                         if (TypeManager.ImplementsInterface (t, target_type))
 147                                                 return new ClassCast (expr, target_type);
 148                                 }
 149                         }
 150
 151                         foreach (Type t in gc.InterfaceConstraints) {
 152                                 if (!TypeManager.IsGenericParameter (t))
 153                                         continue;
 154                                 if (TypeManager.IsSubclassOf (t, target_type))
 155                                         return new ClassCast (expr, target_type);
 156                                 if (TypeManager.ImplementsInterface (t, target_type))
 157                                         return new ClassCast (expr, target_type);
 158                         }
 159 #endif
 160                         return null;
 161                 }
 162
 163                 static bool ImplicitTypeParameterBoxingConversion (Type expr_type, Type target_type,
 164                                                                    out bool use_class_cast)
 165                 {
 166 #if GMCS_SOURCE
 167                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (expr_type);
 168
 169                         if (gc == null) {
 170                                 use_class_cast = false;
 171                                 return target_type == TypeManager.object_type;
 172                         }
 173
 174                         use_class_cast = true;
 175
 176                         if (!gc.HasReferenceTypeConstraint)
 177                                 return false;
 178
 179                         // We're converting from a type parameter which is known to be a reference type.
 180                         Type base_type = TypeParam_EffectiveBaseType (gc);
 181
 182                         if (TypeManager.IsSubclassOf (base_type, target_type))
 183                                 return true;
 184
 185                         if (target_type.IsInterface) {
 186                                 if (TypeManager.ImplementsInterface (base_type, target_type))
 187                                         return true;
 188
 189                                 foreach (Type t in gc.InterfaceConstraints) {
 190                                         if (TypeManager.IsSubclassOf (t, target_type))
 191                                                 return true;
 192                                         if (TypeManager.ImplementsInterface (t, target_type))
 193                                                 return true;
 194                                 }
 195                         }
 196
 197                         foreach (Type t in gc.InterfaceConstraints) {
 198                                 if (!TypeManager.IsGenericParameter (t))
 199                                         continue;
 200                                 if (TypeManager.IsSubclassOf (t, target_type))
 201                                         return true;
 202                                 if (TypeManager.ImplementsInterface (t, target_type))
 203                                         return true;
 204                         }
 205 #endif
 206
 207                         use_class_cast = false;
 208                         return false;
 209                 }
 210
 211                 static bool ExplicitTypeParameterConversionExists (Type source_type, Type target_type)
 212                 {
 213 #if GMCS_SOURCE
 214                         if (TypeManager.IsGenericParameter (target_type)) {
 215                                 GenericConstraints gc = TypeManager.GetTypeParameterConstraints (target_type);
 216                                 if (gc == null)
 217                                         return false;
 218
 219                                 foreach (Type iface in gc.InterfaceConstraints) {
 220                                         if (!TypeManager.IsGenericParameter (iface))
 221                                                 continue;
 222
 223                                         if (TypeManager.IsSubclassOf (source_type, iface))
 224                                                 return true;
 225                                 }
 226                         }
 227 #endif
 228                         return target_type.IsInterface;
 229                 }
 230
 231                 static Expression ExplicitTypeParameterConversion (Expression source, Type target_type)
 232                 {
 233 #if GMCS_SOURCE
 234                         Type source_type = source.Type;
 235
 236                         if (TypeManager.IsGenericParameter (target_type)) {
 237                                 GenericConstraints gc = TypeManager.GetTypeParameterConstraints (target_type);
 238                                 if (gc == null)
 239                                         return null;
 240
 241                                 foreach (Type iface in gc.InterfaceConstraints) {
 242                                         if (!TypeManager.IsGenericParameter (iface))
 243                                                 continue;
 244
 245                                         if (TypeManager.IsSubclassOf (source_type, iface))
 246                                                 return new ClassCast (source, target_type);
 247                                 }
 248                         }
 249
 250                         if (target_type.IsInterface)
 251                                 return new ClassCast (source, target_type);
 252 #endif
 253                         return null;
 254                 }
 255
 256                 static EmptyExpression MyEmptyExpr;
 257                 static Expression ImplicitReferenceConversion (Expression expr, Type target_type, bool explicit_cast)
 258                 {
 259                         Type expr_type = expr.Type;
 260
 261                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
 262                                 // if we are a method group, emit a warning
 263
 264                                 expr.Emit (null);
 265                         }
 266
 267                         if (expr_type == TypeManager.void_type)
 268                                 return null;
 269
 270                         if (TypeManager.IsGenericParameter (expr_type))
 271                                 return ImplicitTypeParameterConversion (expr, target_type);
 272
 273                         //
 274                         // from the null type to any reference-type.
 275                         //
 276                         NullLiteral nl = expr as NullLiteral;
 277                         if (nl != null) {
 278                                 return nl.ConvertImplicitly(target_type);
 279                         }
 280
 281                         if (ImplicitReferenceConversionCore (expr, target_type)) {
 282                                 //
 283                                 // Reduce implicit reference conversion to object
 284                                 //
 285                                 if (!explicit_cast && target_type == TypeManager.object_type)
 286                                         return expr;
 287
 288                                 return EmptyCast.Create (expr, target_type);
 289                         }
 290
 291                         bool use_class_cast;
 292                         if (ImplicitBoxingConversionExists (expr, target_type, out use_class_cast)) {
 293                                 if (use_class_cast)
 294                                         return new ClassCast (expr, target_type);
 295                                 else
 296                                         return new BoxedCast (expr, target_type);
 297                         }
 298
 299                         return null;
 300                 }
 301
 302                 static public bool ImplicitReferenceConversionCore (Expression expr, Type target_type)
 303                 {
 304                         Type expr_type = expr.Type;
 305
 306                         //
 307                         // notice that it is possible to write "ValueType v = 1", the ValueType here
 308                         // is an abstract class, and not really a value type, so we apply the same rules.
 309                         //
 310                         if (target_type == TypeManager.object_type) {
 311                                 //
 312                                 // A pointer type cannot be converted to object
 313                                 //
 314                                 if (expr_type.IsPointer)
 315                                         return false;
 316
 317                                 if (TypeManager.IsValueType (expr_type))
 318                                         return false;
 319                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
 320                                         return expr_type != TypeManager.anonymous_method_type;
 321                                 }
 322
 323                                 return false;
 324                         } else if (target_type == TypeManager.value_type) {
 325                                 return expr_type == TypeManager.enum_type;
 326                         } else if (TypeManager.IsSubclassOf (expr_type, target_type)) {
 327                                 //
 328                                 // Special case: enumeration to System.Enum.
 329                                 // System.Enum is not a value type, it is a class, so we need
 330                                 // a boxing conversion
 331                                 //
 332                                 if (target_type == TypeManager.enum_type || TypeManager.IsGenericParameter (expr_type))
 333                                         return false;
 334
 335                                 return true;
 336                         }
 337
 338                         // This code is kind of mirrored inside ImplicitStandardConversionExists
 339                         // with the small distinction that we only probe there
 340                         //
 341                         // Always ensure that the code here and there is in sync
 342
 343                         // from any class-type S to any interface-type T.
 344                         if (target_type.IsInterface) {
 345                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 346                                         return !TypeManager.IsGenericParameter (expr_type) &&
 347                                                 !TypeManager.IsValueType (expr_type);
 348                                 }
 349                         }
 350
 351                         // from any interface type S to interface-type T.
 352                         if (expr_type.IsInterface && target_type.IsInterface) {
 353                                 return TypeManager.ImplementsInterface (expr_type, target_type);
 354                         }
 355
 356                         // from an array-type S to an array-type of type T
 357                         if (expr_type.IsArray && target_type.IsArray) {
 358                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 359
 360                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 361
 362                                         if (MyEmptyExpr == null)
 363                                                 MyEmptyExpr = new EmptyExpression ();
 364
 365                                         MyEmptyExpr.SetType (expr_element_type);
 366                                         Type target_element_type = TypeManager.GetElementType (target_type);
 367
 368                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 369                                                 return ImplicitStandardConversionExists (
 370                                                         MyEmptyExpr, target_element_type);
 371                                 }
 372                         }
 373
 374                         // from an array-type to System.Array
 375                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 376                                 return true;
 377
 378                         // from an array-type of type T to IList<T>
 379                         if (expr_type.IsArray && Array_To_IList (expr_type, target_type))
 380                                 return true;
 381
 382                         // from any delegate type to System.Delegate
 383                         if (target_type == TypeManager.delegate_type &&
 384                                 (expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type)))
 385                                 return true;
 386
 387                         // from a generic type definition to a generic instance.
 388                         if (TypeManager.IsEqual (expr_type, target_type))
 389                                 return true;
 390
 391                         return false;
 392                 }
 393
 394                 static public bool ImplicitBoxingConversionExists (Expression expr, Type target_type,
 395                                                                    out bool use_class_cast)
 396                 {
 397                         Type expr_type = expr.Type;
 398                         use_class_cast = false;
 399
 400                         //
 401                         // From any value-type to the type object.
 402                         //
 403                         if (target_type == TypeManager.object_type) {
 404                                 //
 405                                 // A pointer type cannot be converted to object
 406                                 //
 407                                 if (expr_type.IsPointer)
 408                                         return false;
 409
 410                                 return TypeManager.IsValueType (expr_type);
 411                         }
 412
 413                         //
 414                         // From any value-type to the type System.ValueType.
 415                         //
 416                         if (target_type == TypeManager.value_type)
 417                                 return TypeManager.IsValueType (expr_type);
 418
 419                         if (target_type == TypeManager.enum_type) {
 420                                 //
 421                                 // From any enum-type to the type System.Enum.
 422                                 //
 423                                 if (expr_type.IsEnum)
 424                                         return true;
 425                                 //
 426                                 // From any nullable-type with an underlying enum-type to the type System.Enum
 427                                 //
 428                                 if (TypeManager.IsNullableType (expr_type))
 429                                         return TypeManager.GetTypeArguments (expr_type) [0].IsEnum;
 430                         }
 431
 432                         if (TypeManager.IsSubclassOf (expr_type, target_type)) {
 433                                 //
 434                                 // Don't box same type arguments
 435                                 //
 436                                 if (TypeManager.IsGenericParameter (expr_type) && expr_type != target_type)
 437                                         return true;
 438
 439                                 return false;
 440                         }
 441
 442                         // This code is kind of mirrored inside ImplicitStandardConversionExists
 443                         // with the small distinction that we only probe there
 444                         //
 445                         // Always ensure that the code here and there is in sync
 446
 447                         // from any class-type S to any interface-type T.
 448                         if (target_type.IsInterface) {
 449                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 450                                         return TypeManager.IsGenericParameter (expr_type) ||
 451                                                 TypeManager.IsValueType (expr_type);
 452                         }
 453
 454                         if (TypeManager.IsGenericParameter (expr_type))
 455                                 return ImplicitTypeParameterBoxingConversion (
 456                                         expr_type, target_type, out use_class_cast);
 457
 458                         return false;
 459                 }
 460
 461                 //
 462                 // Tests whether an implicit reference conversion exists between expr_type
 463                 // and target_type
 464                 //
 465                 public static bool ImplicitReferenceConversionExists (Expression expr, Type target_type)
 466                 {
 467                         if (target_type.IsValueType)
 468                                 return false;
 469
 470                         Type expr_type = expr.Type;
 471
 472                         // from the null type to any reference-type.
 473                         if (expr_type == TypeManager.null_type){
 474                                 return target_type != TypeManager.anonymous_method_type;
 475                         }
 476
 477                         if (TypeManager.IsGenericParameter (expr_type))
 478                                 return ImplicitTypeParameterConversion (expr, target_type) != null;
 479
 480                         bool use_class_cast;
 481                         if (ImplicitReferenceConversionCore (expr, target_type) ||
 482                             ImplicitBoxingConversionExists (expr, target_type, out use_class_cast))
 483                                 return true;
 484
 485                         return false;
 486                 }
 487
 488                 /// <summary>
 489                 ///   Implicit Numeric Conversions.
 490                 ///
 491                 ///   expr is the expression to convert, returns a new expression of type
 492                 ///   target_type or null if an implicit conversion is not possible.
 493                 /// </summary>
 494                 static public Expression ImplicitNumericConversion (Expression expr,
 495                                                                     Type target_type)
 496                 {
 497                         Type expr_type = expr.Type;
 498                         Type real_target_type = target_type;
 499
 500                         if (expr_type == TypeManager.sbyte_type){
 501                                 //
 502                                 // From sbyte to short, int, long, float, double, decimal
 503                                 //
 504                                 if (real_target_type == TypeManager.int32_type)
 505                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 506                                 if (real_target_type == TypeManager.int64_type)
 507                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 508                                 if (real_target_type == TypeManager.double_type)
 509                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 510                                 if (real_target_type == TypeManager.float_type)
 511                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 512                                 if (real_target_type == TypeManager.short_type)
 513                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 514                                 if (real_target_type == TypeManager.decimal_type)
 515                                         return new CastToDecimal (expr);
 516                         } else if (expr_type == TypeManager.byte_type){
 517                                 //
 518                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 519                                 //
 520                                 if (real_target_type == TypeManager.int32_type || real_target_type == TypeManager.uint32_type ||
 521                                     real_target_type == TypeManager.short_type || real_target_type == TypeManager.ushort_type)
 522                                         return EmptyCast.Create (expr, target_type);
 523
 524                                 if (real_target_type == TypeManager.uint64_type)
 525                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 526                                 if (real_target_type == TypeManager.int64_type)
 527                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 528                                 if (real_target_type == TypeManager.float_type)
 529                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 530                                 if (real_target_type == TypeManager.double_type)
 531                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 532                                 if (real_target_type == TypeManager.decimal_type)
 533                                         return new CastToDecimal (expr);
 534
 535                         } else if (expr_type == TypeManager.short_type){
 536                                 //
 537                                 // From short to int, long, float, double, decimal
 538                                 //
 539                                 if (real_target_type == TypeManager.int32_type)
 540                                         return EmptyCast.Create (expr, target_type);
 541                                 if (real_target_type == TypeManager.int64_type)
 542                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 543                                 if (real_target_type == TypeManager.double_type)
 544                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 545                                 if (real_target_type == TypeManager.float_type)
 546                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 547                                 if (real_target_type == TypeManager.decimal_type)
 548                                         return new CastToDecimal (expr);
 549
 550                         } else if (expr_type == TypeManager.ushort_type){
 551                                 //
 552                                 // From ushort to int, uint, long, ulong, float, double, decimal
 553                                 //
 554                                 if (real_target_type == TypeManager.int32_type || real_target_type == TypeManager.uint32_type)
 555                                         return EmptyCast.Create (expr, target_type);
 556
 557                                 if (real_target_type == TypeManager.uint64_type)
 558                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 559                                 if (real_target_type == TypeManager.int64_type)
 560                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 561                                 if (real_target_type == TypeManager.double_type)
 562                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 563                                 if (real_target_type == TypeManager.float_type)
 564                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 565                                 if (real_target_type == TypeManager.decimal_type)
 566                                         return new CastToDecimal (expr);
 567                         } else if (expr_type == TypeManager.int32_type){
 568                                 //
 569                                 // From int to long, float, double, decimal
 570                                 //
 571                                 if (real_target_type == TypeManager.int64_type)
 572                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 573                                 if (real_target_type == TypeManager.double_type)
 574                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 575                                 if (real_target_type == TypeManager.float_type)
 576                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 577                                 if (real_target_type == TypeManager.decimal_type)
 578                                         return new CastToDecimal (expr);
 579                         } else if (expr_type == TypeManager.uint32_type){
 580                                 //
 581                                 // From uint to long, ulong, float, double, decimal
 582                                 //
 583                                 if (real_target_type == TypeManager.int64_type)
 584                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 585                                 if (real_target_type == TypeManager.uint64_type)
 586                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 587                                 if (real_target_type == TypeManager.double_type)
 588                                         return new OpcodeCast (new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un), target_type, OpCodes.Conv_R8);
 589                                 if (real_target_type == TypeManager.float_type)
 590                                         return new OpcodeCast (new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un), target_type, OpCodes.Conv_R4);
 591                                 if (real_target_type == TypeManager.decimal_type)
 592                                         return new CastToDecimal (expr);
 593                         } else if (expr_type == TypeManager.int64_type){
 594                                 //
 595                                 // From long/ulong to float, double
 596                                 //
 597                                 if (real_target_type == TypeManager.double_type)
 598                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 599                                 if (real_target_type == TypeManager.float_type)
 600                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 601                                 if (real_target_type == TypeManager.decimal_type)
 602                                         return new CastToDecimal (expr);
 603                         } else if (expr_type == TypeManager.uint64_type){
 604                                 //
 605                                 // From ulong to float, double
 606                                 //
 607                                 if (real_target_type == TypeManager.double_type)
 608                                         return new OpcodeCast (new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un), target_type, OpCodes.Conv_R8);
 609                                 if (real_target_type == TypeManager.float_type)
 610                                         return new OpcodeCast (new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un), target_type, OpCodes.Conv_R4);
 611                                 if (real_target_type == TypeManager.decimal_type)
 612                                         return new CastToDecimal (expr);
 613                         } else if (expr_type == TypeManager.char_type){
 614                                 //
 615                                 // From char to ushort, int, uint, long, ulong, float, double, decimal
 616                                 //
 617                                 if ((real_target_type == TypeManager.ushort_type) ||
 618                                     (real_target_type == TypeManager.int32_type) ||
 619                                     (real_target_type == TypeManager.uint32_type))
 620                                         return EmptyCast.Create (expr, target_type);
 621                                 if (real_target_type == TypeManager.uint64_type)
 622                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 623                                 if (real_target_type == TypeManager.int64_type)
 624                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 625                                 if (real_target_type == TypeManager.float_type)
 626                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 627                                 if (real_target_type == TypeManager.double_type)
 628                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 629                                 if (real_target_type == TypeManager.decimal_type)
 630                                         return new CastToDecimal (expr);
 631                         } else if (expr_type == TypeManager.float_type){
 632                                 //
 633                                 // float to double
 634                                 //
 635                                 if (real_target_type == TypeManager.double_type)
 636                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 637                         }
 638
 639                         return null;
 640                 }
 641
 642                 /// <summary>
 643                 ///  Same as ImplicitStandardConversionExists except that it also looks at
 644                 ///  implicit user defined conversions - needed for overload resolution
 645                 /// </summary>
 646                 public static bool ImplicitConversionExists (EmitContext ec, Expression expr, Type target_type)
 647                 {
 648 #if GMCS_SOURCE
 649                         if (expr is NullLiteral) {
 650                                 if (TypeManager.IsGenericParameter (target_type))
 651                                         return TypeParameter_to_Null (target_type);
 652
 653                                 if (TypeManager.IsNullableType (target_type))
 654                                         return true;
 655                         }
 656 #endif
 657                         if (ImplicitStandardConversionExists (expr, target_type))
 658                                 return true;
 659
 660                         if (expr.Type == TypeManager.anonymous_method_type) {
 661                                 if (!TypeManager.IsDelegateType (target_type) &&
 662                                         TypeManager.DropGenericTypeArguments (target_type) != TypeManager.expression_type)
 663                                         return false;
 664
 665                                 AnonymousMethodExpression ame = (AnonymousMethodExpression) expr;
 666                                 return ame.ImplicitStandardConversionExists (ec, target_type);
 667                         }
 668
 669                         return ImplicitUserConversion (ec, expr, target_type, Location.Null) != null;
 670                 }
 671
 672                 public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 673                 {
 674                         return ImplicitUserConversion (ec, new EmptyExpression (source), target, Location.Null) != null;
 675                 }
 676
 677                 /// <summary>
 678                 ///  Determines if a standard implicit conversion exists from
 679                 ///  expr_type to target_type
 680                 ///
 681                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 682                 /// </summary>
 683                 public static bool ImplicitStandardConversionExists (Expression expr, Type target_type)
 684                 {
 685                         Type expr_type = expr.Type;
 686 #if GMCS_SOURCE
 687                         if (TypeManager.IsNullableType (target_type)) {
 688                                 // if implicit standard conversion S -> T exists, S -> T? and S? -> T? also exists
 689                                 target_type = TypeManager.GetTypeArguments (target_type) [0];
 690
 691                                 // S? -> T?
 692                                 if (TypeManager.IsNullableType (expr_type)) {
 693                                         EmptyExpression new_expr = EmptyExpression.Grab ();
 694                                         new_expr.SetType (TypeManager.GetTypeArguments (expr_type) [0]);
 695                                         bool retval = ImplicitStandardConversionExists (new_expr, target_type);
 696                                         EmptyExpression.Release (new_expr);
 697                                         return retval;
 698                                 }
 699                         }
 700 #endif
 701                         if (expr_type == TypeManager.void_type)
 702                                 return false;
 703
 704                         //Console.WriteLine ("Expr is {0}", expr);
 705                         //Console.WriteLine ("{0} -> {1} ?", expr_type, target_type);
 706                         if (TypeManager.IsEqual (expr_type, target_type))
 707                                 return true;
 708
 709
 710                         // First numeric conversions
 711
 712                         if (expr_type == TypeManager.sbyte_type){
 713                                 //
 714                                 // From sbyte to short, int, long, float, double, decimal
 715                                 //
 716                                 if ((target_type == TypeManager.int32_type) ||
 717                                     (target_type == TypeManager.int64_type) ||
 718                                     (target_type == TypeManager.double_type) ||
 719                                     (target_type == TypeManager.float_type)  ||
 720                                     (target_type == TypeManager.short_type) ||
 721                                     (target_type == TypeManager.decimal_type))
 722                                         return true;
 723
 724                         } else if (expr_type == TypeManager.byte_type){
 725                                 //
 726                                 // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
 727                                 //
 728                                 if ((target_type == TypeManager.short_type) ||
 729                                     (target_type == TypeManager.ushort_type) ||
 730                                     (target_type == TypeManager.int32_type) ||
 731                                     (target_type == TypeManager.uint32_type) ||
 732                                     (target_type == TypeManager.uint64_type) ||
 733                                     (target_type == TypeManager.int64_type) ||
 734                                     (target_type == TypeManager.float_type) ||
 735                                     (target_type == TypeManager.double_type) ||
 736                                     (target_type == TypeManager.decimal_type))
 737                                         return true;
 738
 739                         } else if (expr_type == TypeManager.short_type){
 740                                 //
 741                                 // From short to int, long, double, float, decimal
 742                                 //
 743                                 if ((target_type == TypeManager.int32_type) ||
 744                                     (target_type == TypeManager.int64_type) ||
 745                                     (target_type == TypeManager.double_type) ||
 746                                     (target_type == TypeManager.float_type) ||
 747                                     (target_type == TypeManager.decimal_type))
 748                                         return true;
 749
 750                         } else if (expr_type == TypeManager.ushort_type){
 751                                 //
 752                                 // From ushort to int, uint, long, ulong, double, float, decimal
 753                                 //
 754                                 if ((target_type == TypeManager.uint32_type) ||
 755                                     (target_type == TypeManager.uint64_type) ||
 756                                     (target_type == TypeManager.int32_type) ||
 757                                     (target_type == TypeManager.int64_type) ||
 758                                     (target_type == TypeManager.double_type) ||
 759                                     (target_type == TypeManager.float_type) ||
 760                                     (target_type == TypeManager.decimal_type))
 761                                         return true;
 762
 763                         } else if (expr_type == TypeManager.int32_type){
 764                                 //
 765                                 // From int to long, double, float, decimal
 766                                 //
 767                                 if ((target_type == TypeManager.int64_type) ||
 768                                     (target_type == TypeManager.double_type) ||
 769                                     (target_type == TypeManager.float_type) ||
 770                                     (target_type == TypeManager.decimal_type))
 771                                         return true;
 772
 773                         } else if (expr_type == TypeManager.uint32_type){
 774                                 //
 775                                 // From uint to long, ulong, double, float, decimal
 776                                 //
 777                                 if ((target_type == TypeManager.int64_type) ||
 778                                     (target_type == TypeManager.uint64_type) ||
 779                                     (target_type == TypeManager.double_type) ||
 780                                     (target_type == TypeManager.float_type) ||
 781                                     (target_type == TypeManager.decimal_type))
 782                                         return true;
 783
 784                         } else if ((expr_type == TypeManager.uint64_type) ||
 785                                    (expr_type == TypeManager.int64_type)) {
 786                                 //
 787                                 // From long/ulong to double, float, decimal
 788                                 //
 789                                 if ((target_type == TypeManager.double_type) ||
 790                                     (target_type == TypeManager.float_type) ||
 791                                     (target_type == TypeManager.decimal_type))
 792                                         return true;
 793
 794                         } else if (expr_type == TypeManager.char_type){
 795                                 //
 796                                 // From char to ushort, int, uint, ulong, long, float, double, decimal
 797                                 //
 798                                 if ((target_type == TypeManager.ushort_type) ||
 799                                     (target_type == TypeManager.int32_type) ||
 800                                     (target_type == TypeManager.uint32_type) ||
 801                                     (target_type == TypeManager.uint64_type) ||
 802                                     (target_type == TypeManager.int64_type) ||
 803                                     (target_type == TypeManager.float_type) ||
 804                                     (target_type == TypeManager.double_type) ||
 805                                     (target_type == TypeManager.decimal_type))
 806                                         return true;
 807
 808                         } else if (expr_type == TypeManager.float_type){
 809                                 //
 810                                 // float to double
 811                                 //
 812                                 if (target_type == TypeManager.double_type)
 813                                         return true;
 814                         }
 815
 816                         if (expr.eclass == ExprClass.MethodGroup){
 817                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 818                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 819                                         if (mg != null){
 820                                                 return DelegateCreation.ImplicitStandardConversionExists (mg, target_type) != null;
 821                                         }
 822                                 }
 823
 824                                 return false;
 825                         }
 826
 827                         if (ImplicitReferenceConversionExists (expr, target_type))
 828                                 return true;
 829
 830                         //
 831                         // Implicit Constant Expression Conversions
 832                         //
 833                         if (expr is IntConstant){
 834                                 int value = ((IntConstant) expr).Value;
 835
 836                                 if (target_type == TypeManager.sbyte_type){
 837                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 838                                                 return true;
 839                                 } else if (target_type == TypeManager.byte_type){
 840                                         if (value >= 0 && value <= Byte.MaxValue)
 841                                                 return true;
 842                                 } else if (target_type == TypeManager.short_type){
 843                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 844                                                 return true;
 845                                 } else if (target_type == TypeManager.ushort_type){
 846                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 847                                                 return true;
 848                                 } else if (target_type == TypeManager.uint32_type){
 849                                         if (value >= 0)
 850                                                 return true;
 851                                 } else if (target_type == TypeManager.uint64_type){
 852                                          //
 853                                          // we can optimize this case: a positive int32
 854                                          // always fits on a uint64.  But we need an opcode
 855                                          // to do it.
 856                                          //
 857                                         if (value >= 0)
 858                                                 return true;
 859                                 }
 860
 861                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 862                                         return true;
 863                         }
 864
 865                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 866                                 //
 867                                 // Try the implicit constant expression conversion
 868                                 // from long to ulong, instead of a nice routine,
 869                                 // we just inline it
 870                                 //
 871                                 long v = ((LongConstant) expr).Value;
 872                                 if (v >= 0)
 873                                         return true;
 874                         }
 875
 876                         //
 877                         // If `expr_type' implements `target_type' (which is an iface)
 878                         // see TryImplicitIntConversion
 879                         //
 880                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 881                                 return true;
 882
 883                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 884                                 return true;
 885
 886                         return false;
 887                 }
 888
 889                 /// <summary>
 890                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 891                 ///  amongst the methods in the MethodGroupExpr
 892                 /// </summary>
 893                 static Type FindMostEncompassedType (ArrayList types)
 894                 {
 895                         Type best = null;
 896
 897                         if (types.Count == 0)
 898                                 return null;
 899
 900                         if (types.Count == 1)
 901                                 return (Type) types [0];
 902
 903                         EmptyExpression expr = EmptyExpression.Grab ();
 904
 905                         foreach (Type t in types) {
 906                                 if (best == null) {
 907                                         best = t;
 908                                         continue;
 909                                 }
 910
 911                                 expr.SetType (t);
 912                                 if (ImplicitStandardConversionExists (expr, best))
 913                                         best = t;
 914                         }
 915
 916                         expr.SetType (best);
 917                         foreach (Type t in types) {
 918                                 if (best == t)
 919                                         continue;
 920                                 if (!ImplicitStandardConversionExists (expr, t)) {
 921                                         best = null;
 922                                         break;
 923                                 }
 924                         }
 925
 926                         EmptyExpression.Release (expr);
 927
 928                         return best;
 929                 }
 930
 931                 /// <summary>
 932                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 933                 ///  amongst the types in the given set
 934                 /// </summary>
 935                 static Type FindMostEncompassingType (ArrayList types)
 936                 {
 937                         Type best = null;
 938
 939                         if (types.Count == 0)
 940                                 return null;
 941
 942                         if (types.Count == 1)
 943                                 return (Type) types [0];
 944
 945                         EmptyExpression expr = EmptyExpression.Grab ();
 946
 947                         foreach (Type t in types) {
 948                                 if (best == null) {
 949                                         best = t;
 950                                         continue;
 951                                 }
 952
 953                                 expr.SetType (best);
 954                                 if (ImplicitStandardConversionExists (expr, t))
 955                                         best = t;
 956                         }
 957
 958                         foreach (Type t in types) {
 959                                 if (best == t)
 960                                         continue;
 961                                 expr.SetType (t);
 962                                 if (!ImplicitStandardConversionExists (expr, best)) {
 963                                         best = null;
 964                                         break;
 965                                 }
 966                         }
 967
 968                         EmptyExpression.Release (expr);
 969
 970                         return best;
 971                 }
 972
 973                 /// <summary>
 974                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 975                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 976                 ///   for explicit and implicit conversion operators.
 977                 /// </summary>
 978                 static public Type FindMostSpecificSource (IList list,
 979                                                            Expression source, bool apply_explicit_conv_rules)
 980                 {
 981                         ArrayList src_types_set = new ArrayList ();
 982
 983                         //
 984                         // If any operator converts from S then Sx = S
 985                         //
 986                         Type source_type = source.Type;
 987                         foreach (MethodBase mb in list){
 988                                 ParameterData pd = TypeManager.GetParameterData (mb);
 989                                 Type param_type = pd.ParameterType (0);
 990
 991                                 if (param_type == source_type)
 992                                         return param_type;
 993
 994                                 src_types_set.Add (param_type);
 995                         }
 996
 997                         //
 998                         // Explicit Conv rules
 999                         //
1000                         if (apply_explicit_conv_rules) {
1001                                 ArrayList candidate_set = new ArrayList ();
1002
1003                                 foreach (Type param_type in src_types_set){
1004                                         if (ImplicitStandardConversionExists (source, param_type))
1005                                                 candidate_set.Add (param_type);
1006                                 }
1007
1008                                 if (candidate_set.Count != 0)
1009                                         return FindMostEncompassedType (candidate_set);
1010                         }
1011
1012                         //
1013                         // Final case
1014                         //
1015                         if (apply_explicit_conv_rules)
1016                                 return FindMostEncompassingType (src_types_set);
1017                         else
1018                                 return FindMostEncompassedType (src_types_set);
1019                 }
1020
1021                 /// <summary>
1022                 ///  Finds the most specific target Tx according to section 13.4.4
1023                 /// </summary>
1024                 static public Type FindMostSpecificTarget (IList list,
1025                                                            Type target, bool apply_explicit_conv_rules)
1026                 {
1027                         ArrayList tgt_types_set = new ArrayList ();
1028
1029                         //
1030                         // If any operator converts to T then Tx = T
1031                         //
1032                         foreach (MethodInfo mi in list){
1033                                 Type ret_type = TypeManager.TypeToCoreType (mi.ReturnType);
1034                                 if (ret_type == target)
1035                                         return ret_type;
1036
1037                                 tgt_types_set.Add (ret_type);
1038                         }
1039
1040                         //
1041                         // Explicit conv rules
1042                         //
1043                         if (apply_explicit_conv_rules) {
1044                                 ArrayList candidate_set = new ArrayList ();
1045
1046                                 EmptyExpression expr = EmptyExpression.Grab ();
1047
1048                                 foreach (Type ret_type in tgt_types_set){
1049                                         expr.SetType (ret_type);
1050
1051                                         if (ImplicitStandardConversionExists (expr, target))
1052                                                 candidate_set.Add (ret_type);
1053                                 }
1054
1055                                 EmptyExpression.Release (expr);
1056
1057                                 if (candidate_set.Count != 0)
1058                                         return FindMostEncompassingType (candidate_set);
1059                         }
1060
1061                         //
1062                         // Okay, final case !
1063                         //
1064                         if (apply_explicit_conv_rules)
1065                                 return FindMostEncompassedType (tgt_types_set);
1066                         else
1067                                 return FindMostEncompassingType (tgt_types_set);
1068                 }
1069
1070                 /// <summary>
1071                 ///  User-defined Implicit conversions
1072                 /// </summary>
1073                 static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
1074                                                                  Type target, Location loc)
1075                 {
1076                         Expression expr = UserDefinedConversion (ec, source, target, loc, false);
1077                         if (expr != null && !TypeManager.IsEqual (expr.Type, target))
1078                                 expr = ImplicitConversionStandard (ec, expr, target, loc);
1079
1080                         return expr;
1081                 }
1082
1083                 /// <summary>
1084                 ///  User-defined Explicit conversions
1085                 /// </summary>
1086                 static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
1087                                                                  Type target, Location loc)
1088                 {
1089                         Expression expr = UserDefinedConversion (ec, source, target, loc, true);
1090                         if (expr != null && !TypeManager.IsEqual (expr.Type, target))
1091                                 expr = ExplicitConversionStandard (ec, expr, target, loc);
1092
1093                         return expr;
1094                 }
1095
1096                 static void AddConversionOperators (ArrayList list,
1097                                                     Expression source, Type target_type,
1098                                                     bool look_for_explicit,
1099                                                     MethodGroupExpr mg)
1100                 {
1101                         if (mg == null)
1102                                 return;
1103
1104                         Type source_type = source.Type;
1105                         EmptyExpression expr = EmptyExpression.Grab ();
1106
1107                         //
1108                         // LAMESPEC: Undocumented IntPtr/UIntPtr conversions
1109                         // IntPtr -> uint uses int
1110                         // UIntPtr -> long uses ulong
1111                         //
1112                         if (source_type == TypeManager.intptr_type) {
1113                                 if (target_type == TypeManager.uint32_type)
1114                                         target_type = TypeManager.int32_type;
1115                         } else if (source_type == TypeManager.uintptr_type) {
1116                                 if (target_type == TypeManager.int64_type)
1117                                         target_type = TypeManager.uint64_type;
1118                         }
1119
1120                         foreach (MethodInfo m in mg.Methods) {
1121                                 ParameterData pd = TypeManager.GetParameterData (m);
1122                                 Type return_type = TypeManager.TypeToCoreType (m.ReturnType);
1123                                 Type arg_type = pd.ParameterType (0);
1124
1125                                 if (source_type != arg_type) {
1126                                         if (!ImplicitStandardConversionExists (source, arg_type)) {
1127                                                 if (!look_for_explicit)
1128                                                         continue;
1129                                                 expr.SetType (arg_type);
1130                                                 if (!ImplicitStandardConversionExists (expr, source_type))
1131                                                         continue;
1132                                         }
1133                                 }
1134
1135                                 if (target_type != return_type) {
1136                                         expr.SetType (return_type);
1137                                         if (!ImplicitStandardConversionExists (expr, target_type)) {
1138                                                 if (!look_for_explicit)
1139                                                         continue;
1140                                                 expr.SetType (target_type);
1141                                                 if (!ImplicitStandardConversionExists (expr, return_type))
1142                                                         continue;
1143                                         }
1144                                 }
1145
1146                                 // See LAMESPEC: Exclude IntPtr -> int conversion
1147                                 if (source_type == TypeManager.uintptr_type && return_type == TypeManager.uint32_type)
1148                                         continue;
1149
1150                                 list.Add (m);
1151                         }
1152
1153                         EmptyExpression.Release (expr);
1154                 }
1155
1156                 /// <summary>
1157                 ///   Compute the user-defined conversion operator from source_type to target_type.
1158                 ///   `look_for_explicit' controls whether we should also include the list of explicit operators
1159                 /// </summary>
1160                 static MethodInfo GetConversionOperator (Type container_type, Expression source, Type target_type, bool look_for_explicit)
1161                 {
1162                         ArrayList ops = new ArrayList (4);
1163
1164                         Type source_type = source.Type;
1165
1166                         if (source_type != TypeManager.decimal_type) {
1167                                 AddConversionOperators (ops, source, target_type, look_for_explicit,
1168                                         Expression.MethodLookup (container_type, source_type, "op_Implicit", Location.Null) as MethodGroupExpr);
1169                                 if (look_for_explicit) {
1170                                         AddConversionOperators (ops, source, target_type, look_for_explicit,
1171                                                 Expression.MethodLookup (
1172                                                         container_type, source_type, "op_Explicit", Location.Null) as MethodGroupExpr);
1173                                 }
1174                         }
1175
1176                         if (target_type != TypeManager.decimal_type) {
1177                                 AddConversionOperators (ops, source, target_type, look_for_explicit,
1178                                         Expression.MethodLookup (container_type, target_type, "op_Implicit", Location.Null) as MethodGroupExpr);
1179                                 if (look_for_explicit) {
1180                                         AddConversionOperators (ops, source, target_type, look_for_explicit,
1181                                                 Expression.MethodLookup (
1182                                                         container_type, target_type, "op_Explicit", Location.Null) as MethodGroupExpr);
1183                                 }
1184                         }
1185
1186                         if (ops.Count == 0)
1187                                 return null;
1188
1189                         Type most_specific_source = FindMostSpecificSource (ops, source, look_for_explicit);
1190                         if (most_specific_source == null)
1191                                 return null;
1192
1193                         Type most_specific_target = FindMostSpecificTarget (ops, target_type, look_for_explicit);
1194                         if (most_specific_target == null)
1195                                 return null;
1196
1197                         MethodInfo method = null;
1198
1199                         foreach (MethodInfo m in ops) {
1200                                 if (TypeManager.TypeToCoreType (m.ReturnType) != most_specific_target)
1201                                         continue;
1202                                 if (TypeManager.GetParameterData (m).ParameterType (0) != most_specific_source)
1203                                         continue;
1204                                 // Ambiguous: more than one conversion operator satisfies the signature.
1205                                 if (method != null)
1206                                         return null;
1207                                 method = m;
1208                         }
1209
1210                         return method;
1211                 }
1212
1213                 static DoubleHash explicit_conv = new DoubleHash (100);
1214                 static DoubleHash implicit_conv = new DoubleHash (100);
1215
1216                 /// <summary>
1217                 ///   User-defined conversions
1218                 /// </summary>
1219                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
1220                                                                 Type target, Location loc,
1221                                                                 bool look_for_explicit)
1222                 {
1223                         Type source_type = source.Type;
1224                         MethodInfo method = null;
1225
1226                         object o;
1227                         DoubleHash hash;
1228                         if (look_for_explicit) {
1229                                 hash = explicit_conv;
1230                         } else {
1231                                 // Implicit user operators cannot convert to interfaces
1232                                 if (target.IsInterface)
1233                                         return null;
1234
1235                                 hash = implicit_conv;
1236                         }
1237
1238                         if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
1239                                 method = (MethodInfo) o;
1240                         } else {
1241                                 method = GetConversionOperator (null, source, target, look_for_explicit);
1242                                 if (!(source is Constant))
1243                                         hash.Insert (source_type, target, method);
1244                         }
1245
1246                         if (method == null)
1247                                 return null;
1248
1249                         Type most_specific_source = TypeManager.GetParameterData (method).ParameterType (0);
1250
1251                         //
1252                         // This will do the conversion to the best match that we
1253                         // found.  Now we need to perform an implict standard conversion
1254                         // if the best match was not the type that we were requested
1255                         // by target.
1256                         //
1257                         if (look_for_explicit)
1258                                 source = ExplicitConversionStandard (ec, source, most_specific_source, loc);
1259                         else
1260                                 source = ImplicitConversionStandard (ec, source, most_specific_source, loc);
1261
1262                         if (source == null)
1263                                 return null;
1264
1265                         return new UserCast (method, source, loc);
1266                 }
1267
1268                 /// <summary>
1269                 ///   Converts implicitly the resolved expression `expr' into the
1270                 ///   `target_type'.  It returns a new expression that can be used
1271                 ///   in a context that expects a `target_type'.
1272                 /// </summary>
1273                 static public Expression ImplicitConversion (EmitContext ec, Expression expr,
1274                                                              Type target_type, Location loc)
1275                 {
1276                         Expression e;
1277
1278                         if (target_type == null)
1279                                 throw new Exception ("Target type is null");
1280
1281                         e = ImplicitConversionStandard (ec, expr, target_type, loc);
1282                         if (e != null)
1283                                 return e;
1284
1285                         e = ImplicitUserConversion (ec, expr, target_type, loc);
1286                         if (e != null)
1287                                 return e;
1288
1289                         return null;
1290                 }
1291
1292
1293                 /// <summary>
1294                 ///   Attempts to apply the `Standard Implicit
1295                 ///   Conversion' rules to the expression `expr' into
1296                 ///   the `target_type'.  It returns a new expression
1297                 ///   that can be used in a context that expects a
1298                 ///   `target_type'.
1299                 ///
1300                 ///   This is different from `ImplicitConversion' in that the
1301                 ///   user defined implicit conversions are excluded.
1302                 /// </summary>
1303                 static public Expression ImplicitConversionStandard (EmitContext ec, Expression expr,
1304                                                                      Type target_type, Location loc)
1305                 {
1306                         return ImplicitConversionStandard (ec, expr, target_type, loc, false);
1307                 }
1308
1309                 static Expression ImplicitConversionStandard (EmitContext ec, Expression expr, Type target_type, Location loc, bool explicit_cast)
1310                 {
1311                         Type expr_type = expr.Type;
1312                         Expression e;
1313
1314 #if GMCS_SOURCE
1315                         if (TypeManager.IsNullableType (target_type)) {
1316                                 //
1317                                 // From null to any nullable type
1318                                 //
1319                                 if (expr_type == TypeManager.null_type)
1320                                         return Nullable.LiftedNull.Create (target_type, loc);
1321
1322                                 Type target = TypeManager.GetTypeArguments (target_type) [0];
1323
1324                                 if (TypeManager.IsNullableType (expr_type)) {
1325                                         Type etype = TypeManager.GetTypeArguments (expr_type) [0];
1326                                         if (TypeManager.IsEqual (etype, target))
1327                                                 return expr;
1328
1329                                         return new Nullable.LiftedConversion (
1330                                                 expr, target_type, false, false, loc).Resolve (ec);
1331                                 } else {
1332                                         e = ImplicitConversion (ec, expr, target, loc);
1333                                         if (e != null)
1334                                                 return Nullable.Wrap.Create (e, target_type);
1335                                 }
1336                         }
1337 #endif
1338                         if (expr.eclass == ExprClass.MethodGroup){
1339                                 if (!TypeManager.IsDelegateType (target_type)){
1340                                         return null;
1341                                 }
1342
1343                                 //
1344                                 // Only allow anonymous method conversions on post ISO_1
1345                                 //
1346                                 if (RootContext.Version != LanguageVersion.ISO_1){
1347                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1348                                         if (mg != null)
1349                                                 return ImplicitDelegateCreation.Create (
1350                                                         ec, mg, target_type, loc);
1351                                 }
1352                         }
1353
1354                         if (expr_type.Equals (target_type)) {
1355                                 if (expr_type != TypeManager.null_type && expr_type != TypeManager.anonymous_method_type)
1356                                         return expr;
1357                                 return null;
1358                         }
1359
1360                         //
1361                         // Attempt to do the implicit constant expression conversions
1362                         //
1363                         Constant c = expr as Constant;
1364                         if (c != null) {
1365                                 //
1366                                 // If `target_type' is an interface and the type of `ic' implements the interface
1367                                 // e.g. target_type is IComparable, IConvertible, IFormattable
1368                                 //
1369                                 if (c.Type == TypeManager.int32_type && target_type.IsInterface && target_type.IsAssignableFrom (c.Type))
1370                                         return new BoxedCast (c, target_type);
1371
1372                                 try {
1373                                         c = c.ConvertImplicitly (target_type);
1374                                 } catch {
1375                                         Console.WriteLine ("Conversion error happened in line {0}", loc);
1376                                         throw;
1377                                 }
1378                                 if (c != null)
1379                                         return c;
1380                         }
1381
1382                         e = ImplicitNumericConversion (expr, target_type);
1383                         if (e != null)
1384                                 return e;
1385
1386                         e = ImplicitReferenceConversion (expr, target_type, explicit_cast);
1387                         if (e != null)
1388                                 return e;
1389
1390                         if (TypeManager.IsEnumType (target_type) && expr is IntLiteral){
1391                                 IntLiteral i = (IntLiteral) expr;
1392
1393                                 if (i.Value == 0)
1394                                         return new EnumConstant ((Constant) expr, target_type);
1395                         }
1396
1397                         if (ec.InUnsafe) {
1398                                 if (expr_type.IsPointer){
1399                                         if (target_type == TypeManager.void_ptr_type)
1400                                                 return EmptyCast.Create (expr, target_type);
1401
1402                                         //
1403                                         // yep, comparing pointer types cant be done with
1404                                         // t1 == t2, we have to compare their element types.
1405                                         //
1406                                         if (target_type.IsPointer){
1407                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1408                                                         return expr;
1409
1410                                                 //return null;
1411                                         }
1412                                 }
1413
1414                                 if (expr_type == TypeManager.null_type && target_type.IsPointer)
1415                                         return EmptyCast.Create (NullPointer.Null, target_type);
1416                         }
1417
1418                         if (expr_type == TypeManager.anonymous_method_type){
1419                                 AnonymousMethodExpression ame = (AnonymousMethodExpression) expr;
1420                                 Expression am = ame.Compatible (ec, target_type);
1421                                 if (am != null)
1422                                         return am.DoResolve (ec);
1423                         }
1424
1425                         return null;
1426                 }
1427
1428                 /// <summary>
1429                 ///   Attempts to implicitly convert `source' into `target_type', using
1430                 ///   ImplicitConversion.  If there is no implicit conversion, then
1431                 ///   an error is signaled
1432                 /// </summary>
1433                 static public Expression ImplicitConversionRequired (EmitContext ec, Expression source,
1434                                                                      Type target_type, Location loc)
1435                 {
1436                         Expression e = ImplicitConversion (ec, source, target_type, loc);
1437                         if (e != null)
1438                                 return e;
1439
1440                         source.Error_ValueCannotBeConverted (ec, loc, target_type, false);
1441                         return null;
1442                 }
1443
1444                 /// <summary>
1445                 ///   Performs the explicit numeric conversions
1446                 ///
1447                 /// There are a few conversions that are not part of the C# standard,
1448                 /// they were interim hacks in the C# compiler that were supposed to
1449                 /// become explicit operators in the UIntPtr class and IntPtr class,
1450                 /// but for historical reasons it did not happen, so the C# compiler
1451                 /// ended up with these special hacks.
1452                 ///
1453                 /// See bug 59800 for details.
1454                 ///
1455                 /// The conversion are:
1456                 ///   UIntPtr->SByte
1457                 ///   UIntPtr->Int16
1458                 ///   UIntPtr->Int32
1459                 ///   IntPtr->UInt64
1460                 ///   UInt64->IntPtr
1461                 ///   SByte->UIntPtr
1462                 ///   Int16->UIntPtr
1463                 ///
1464                 /// </summary>
1465                 public static Expression ExplicitNumericConversion (Expression expr, Type target_type)
1466                 {
1467                         Type expr_type = expr.Type;
1468                         Type real_target_type = target_type;
1469
1470                         if (expr_type == TypeManager.sbyte_type){
1471                                 //
1472                                 // From sbyte to byte, ushort, uint, ulong, char, uintptr
1473                                 //
1474                                 if (real_target_type == TypeManager.byte_type)
1475                                         return new ConvCast (expr, target_type, ConvCast.Mode.I1_U1);
1476                                 if (real_target_type == TypeManager.ushort_type)
1477                                         return new ConvCast (expr, target_type, ConvCast.Mode.I1_U2);
1478                                 if (real_target_type == TypeManager.uint32_type)
1479                                         return new ConvCast (expr, target_type, ConvCast.Mode.I1_U4);
1480                                 if (real_target_type == TypeManager.uint64_type)
1481                                         return new ConvCast (expr, target_type, ConvCast.Mode.I1_U8);
1482                                 if (real_target_type == TypeManager.char_type)
1483                                         return new ConvCast (expr, target_type, ConvCast.Mode.I1_CH);
1484
1485                                 // One of the built-in conversions that belonged in the class library
1486                                 if (real_target_type == TypeManager.uintptr_type){
1487                                         Expression u8e = new ConvCast (expr, TypeManager.uint64_type, ConvCast.Mode.I1_U8);
1488
1489                                         return new OperatorCast (u8e, TypeManager.uintptr_type, true);
1490                                 }
1491                         } else if (expr_type == TypeManager.byte_type){
1492                                 //
1493                                 // From byte to sbyte and char
1494                                 //
1495                                 if (real_target_type == TypeManager.sbyte_type)
1496                                         return new ConvCast (expr, target_type, ConvCast.Mode.U1_I1);
1497                                 if (real_target_type == TypeManager.char_type)
1498                                         return new ConvCast (expr, target_type, ConvCast.Mode.U1_CH);
1499                         } else if (expr_type == TypeManager.short_type){
1500                                 //
1501                                 // From short to sbyte, byte, ushort, uint, ulong, char, uintptr
1502                                 //
1503                                 if (real_target_type == TypeManager.sbyte_type)
1504                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_I1);
1505                                 if (real_target_type == TypeManager.byte_type)
1506                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_U1);
1507                                 if (real_target_type == TypeManager.ushort_type)
1508                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_U2);
1509                                 if (real_target_type == TypeManager.uint32_type)
1510                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_U4);
1511                                 if (real_target_type == TypeManager.uint64_type)
1512                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_U8);
1513                                 if (real_target_type == TypeManager.char_type)
1514                                         return new ConvCast (expr, target_type, ConvCast.Mode.I2_CH);
1515
1516                                 // One of the built-in conversions that belonged in the class library
1517                                 if (real_target_type == TypeManager.uintptr_type){
1518                                         Expression u8e = new ConvCast (expr, TypeManager.uint64_type, ConvCast.Mode.I2_U8);
1519
1520                                         return new OperatorCast (u8e, TypeManager.uintptr_type, true);
1521                                 }
1522                         } else if (expr_type == TypeManager.ushort_type){
1523                                 //
1524                                 // From ushort to sbyte, byte, short, char
1525                                 //
1526                                 if (real_target_type == TypeManager.sbyte_type)
1527                                         return new ConvCast (expr, target_type, ConvCast.Mode.U2_I1);
1528                                 if (real_target_type == TypeManager.byte_type)
1529                                         return new ConvCast (expr, target_type, ConvCast.Mode.U2_U1);
1530                                 if (real_target_type == TypeManager.short_type)
1531                                         return new ConvCast (expr, target_type, ConvCast.Mode.U2_I2);
1532                                 if (real_target_type == TypeManager.char_type)
1533                                         return new ConvCast (expr, target_type, ConvCast.Mode.U2_CH);
1534                         } else if (expr_type == TypeManager.int32_type){
1535                                 //
1536                                 // From int to sbyte, byte, short, ushort, uint, ulong, char, uintptr
1537                                 //
1538                                 if (real_target_type == TypeManager.sbyte_type)
1539                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_I1);
1540                                 if (real_target_type == TypeManager.byte_type)
1541                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_U1);
1542                                 if (real_target_type == TypeManager.short_type)
1543                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_I2);
1544                                 if (real_target_type == TypeManager.ushort_type)
1545                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_U2);
1546                                 if (real_target_type == TypeManager.uint32_type)
1547                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_U4);
1548                                 if (real_target_type == TypeManager.uint64_type)
1549                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_U8);
1550                                 if (real_target_type == TypeManager.char_type)
1551                                         return new ConvCast (expr, target_type, ConvCast.Mode.I4_CH);
1552
1553                                 // One of the built-in conversions that belonged in the class library
1554                                 if (real_target_type == TypeManager.uintptr_type){
1555                                         Expression u8e = new ConvCast (expr, TypeManager.uint64_type, ConvCast.Mode.I2_U8);
1556
1557                                         return new OperatorCast (u8e, TypeManager.uintptr_type, true);
1558                                 }
1559                         } else if (expr_type == TypeManager.uint32_type){
1560                                 //
1561                                 // From uint to sbyte, byte, short, ushort, int, char
1562                                 //
1563                                 if (real_target_type == TypeManager.sbyte_type)
1564                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_I1);
1565                                 if (real_target_type == TypeManager.byte_type)
1566                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_U1);
1567                                 if (real_target_type == TypeManager.short_type)
1568                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_I2);
1569                                 if (real_target_type == TypeManager.ushort_type)
1570                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_U2);
1571                                 if (real_target_type == TypeManager.int32_type)
1572                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_I4);
1573                                 if (real_target_type == TypeManager.char_type)
1574                                         return new ConvCast (expr, target_type, ConvCast.Mode.U4_CH);
1575                         } else if (expr_type == TypeManager.int64_type){
1576                                 //
1577                                 // From long to sbyte, byte, short, ushort, int, uint, ulong, char
1578                                 //
1579                                 if (real_target_type == TypeManager.sbyte_type)
1580                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_I1);
1581                                 if (real_target_type == TypeManager.byte_type)
1582                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_U1);
1583                                 if (real_target_type == TypeManager.short_type)
1584                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_I2);
1585                                 if (real_target_type == TypeManager.ushort_type)
1586                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_U2);
1587                                 if (real_target_type == TypeManager.int32_type)
1588                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_I4);
1589                                 if (real_target_type == TypeManager.uint32_type)
1590                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_U4);
1591                                 if (real_target_type == TypeManager.uint64_type)
1592                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_U8);
1593                                 if (real_target_type == TypeManager.char_type)
1594                                         return new ConvCast (expr, target_type, ConvCast.Mode.I8_CH);
1595                         } else if (expr_type == TypeManager.uint64_type){
1596                                 //
1597                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1598                                 //
1599                                 if (real_target_type == TypeManager.sbyte_type)
1600                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_I1);
1601                                 if (real_target_type == TypeManager.byte_type)
1602                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_U1);
1603                                 if (real_target_type == TypeManager.short_type)
1604                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_I2);
1605                                 if (real_target_type == TypeManager.ushort_type)
1606                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_U2);
1607                                 if (real_target_type == TypeManager.int32_type)
1608                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_I4);
1609                                 if (real_target_type == TypeManager.uint32_type)
1610                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_U4);
1611                                 if (real_target_type == TypeManager.int64_type)
1612                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_I8);
1613                                 if (real_target_type == TypeManager.char_type)
1614                                         return new ConvCast (expr, target_type, ConvCast.Mode.U8_CH);
1615
1616                                 // One of the built-in conversions that belonged in the class library
1617                                 if (real_target_type == TypeManager.intptr_type){
1618                                         return new OperatorCast (EmptyCast.Create (expr, TypeManager.int64_type),
1619                                                                  TypeManager.intptr_type, true);
1620                                 }
1621                         } else if (expr_type == TypeManager.char_type){
1622                                 //
1623                                 // From char to sbyte, byte, short
1624                                 //
1625                                 if (real_target_type == TypeManager.sbyte_type)
1626                                         return new ConvCast (expr, target_type, ConvCast.Mode.CH_I1);
1627                                 if (real_target_type == TypeManager.byte_type)
1628                                         return new ConvCast (expr, target_type, ConvCast.Mode.CH_U1);
1629                                 if (real_target_type == TypeManager.short_type)
1630                                         return new ConvCast (expr, target_type, ConvCast.Mode.CH_I2);
1631                         } else if (expr_type == TypeManager.float_type){
1632                                 //
1633                                 // From float to sbyte, byte, short,
1634                                 // ushort, int, uint, long, ulong, char
1635                                 // or decimal
1636                                 //
1637                                 if (real_target_type == TypeManager.sbyte_type)
1638                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_I1);
1639                                 if (real_target_type == TypeManager.byte_type)
1640                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_U1);
1641                                 if (real_target_type == TypeManager.short_type)
1642                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_I2);
1643                                 if (real_target_type == TypeManager.ushort_type)
1644                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_U2);
1645                                 if (real_target_type == TypeManager.int32_type)
1646                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_I4);
1647                                 if (real_target_type == TypeManager.uint32_type)
1648                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_U4);
1649                                 if (real_target_type == TypeManager.int64_type)
1650                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_I8);
1651                                 if (real_target_type == TypeManager.uint64_type)
1652                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_U8);
1653                                 if (real_target_type == TypeManager.char_type)
1654                                         return new ConvCast (expr, target_type, ConvCast.Mode.R4_CH);
1655                                 if (real_target_type == TypeManager.decimal_type)
1656                                         return new CastToDecimal (expr, true);
1657                         } else if (expr_type == TypeManager.double_type){
1658                                 //
1659                                 // From double to sbyte, byte, short,
1660                                 // ushort, int, uint, long, ulong,
1661                                 // char, float or decimal
1662                                 //
1663                                 if (real_target_type == TypeManager.sbyte_type)
1664                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_I1);
1665                                 if (real_target_type == TypeManager.byte_type)
1666                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_U1);
1667                                 if (real_target_type == TypeManager.short_type)
1668                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_I2);
1669                                 if (real_target_type == TypeManager.ushort_type)
1670                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_U2);
1671                                 if (real_target_type == TypeManager.int32_type)
1672                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_I4);
1673                                 if (real_target_type == TypeManager.uint32_type)
1674                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_U4);
1675                                 if (real_target_type == TypeManager.int64_type)
1676                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_I8);
1677                                 if (real_target_type == TypeManager.uint64_type)
1678                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_U8);
1679                                 if (real_target_type == TypeManager.char_type)
1680                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_CH);
1681                                 if (real_target_type == TypeManager.float_type)
1682                                         return new ConvCast (expr, target_type, ConvCast.Mode.R8_R4);
1683                                 if (real_target_type == TypeManager.decimal_type)
1684                                         return new CastToDecimal (expr, true);
1685                         } else if (expr_type == TypeManager.uintptr_type){
1686                                 //
1687                                 // Various built-in conversions that belonged in the class library
1688                                 //
1689                                 // from uintptr to sbyte, short, int32
1690                                 //
1691                                 if (real_target_type == TypeManager.sbyte_type){
1692                                         Expression uint32e = new OperatorCast (expr, TypeManager.uint32_type, true);
1693                                         return new ConvCast (uint32e, TypeManager.sbyte_type, ConvCast.Mode.U4_I1);
1694                                 }
1695                                 if (real_target_type == TypeManager.short_type){
1696                                         Expression uint32e = new OperatorCast (expr, TypeManager.uint32_type, true);
1697                                         return new ConvCast (uint32e, TypeManager.sbyte_type, ConvCast.Mode.U4_I2);
1698                                 }
1699                                 if (real_target_type == TypeManager.int32_type){
1700                                         return EmptyCast.Create (new OperatorCast (expr, TypeManager.uint32_type, true),
1701                                                               TypeManager.int32_type);
1702                                 }
1703                         } else if (expr_type == TypeManager.intptr_type){
1704                                 if (real_target_type == TypeManager.uint64_type){
1705                                         return EmptyCast.Create (new OperatorCast (expr, TypeManager.int64_type, true),
1706                                                               TypeManager.uint64_type);
1707                                 }
1708                         } else if (expr_type == TypeManager.decimal_type) {
1709                                 return new CastFromDecimal (expr, target_type).Resolve ();
1710                         }
1711                         return null;
1712                 }
1713
1714                 /// <summary>
1715                 ///  Returns whether an explicit reference conversion can be performed
1716                 ///  from source_type to target_type
1717                 /// </summary>
1718                 public static bool ExplicitReferenceConversionExists (Type source_type, Type target_type)
1719                 {
1720                         bool target_is_type_param = TypeManager.IsGenericParameter (target_type);
1721                         bool target_is_value_type = target_type.IsValueType;
1722
1723                         if (source_type == target_type)
1724                                 return true;
1725
1726                         //
1727                         // From generic parameter to any type
1728                         //
1729                         if (TypeManager.IsGenericParameter (source_type))
1730                                 return ExplicitTypeParameterConversionExists (source_type, target_type);
1731
1732                         //
1733                         // From object to a generic parameter
1734                         //
1735                         if (source_type == TypeManager.object_type && target_is_type_param)
1736                                 return true;
1737
1738                         //
1739                         // From object to any reference type
1740                         //
1741                         if (source_type == TypeManager.object_type && !target_is_value_type)
1742                                 return true;
1743
1744                         //
1745                         // From any class S to any class-type T, provided S is a base class of T
1746                         //
1747                         if (TypeManager.IsSubclassOf (target_type, source_type))
1748                                 return true;
1749
1750                         //
1751                         // From any interface type S to any interface T provided S is not derived from T
1752                         //
1753                         if (source_type.IsInterface && target_type.IsInterface){
1754                                 if (!TypeManager.IsSubclassOf (target_type, source_type))
1755                                         return true;
1756                         }
1757
1758                         //
1759                         // From any class type S to any interface T, provided S is not sealed
1760                         // and provided S does not implement T.
1761                         //
1762                         if (target_type.IsInterface && !source_type.IsSealed &&
1763                             !TypeManager.ImplementsInterface (source_type, target_type))
1764                                 return true;
1765
1766                         //
1767                         // From any interface-type S to to any class type T, provided T is not
1768                         // sealed, or provided T implements S.
1769                         //
1770                         if (source_type.IsInterface &&
1771                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
1772                                 return true;
1773
1774
1775                         if (source_type.IsInterface && IList_To_Array (source_type, target_type))
1776                                 return true;
1777
1778                         // From an array type S with an element type Se to an array type T with an
1779                         // element type Te provided all the following are true:
1780                         //     * S and T differe only in element type, in other words, S and T
1781                         //       have the same number of dimensions.
1782                         //     * Both Se and Te are reference types
1783                         //     * An explicit referenc conversions exist from Se to Te
1784                         //
1785                         if (source_type.IsArray && target_type.IsArray) {
1786                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1787
1788                                         Type source_element_type = TypeManager.GetElementType (source_type);
1789                                         Type target_element_type = TypeManager.GetElementType (target_type);
1790
1791                                         if (TypeManager.IsGenericParameter (source_element_type) ||
1792                                             (!source_element_type.IsValueType && !target_element_type.IsValueType))
1793                                                 if (ExplicitReferenceConversionExists (source_element_type,
1794                                                                                        target_element_type))
1795                                                         return true;
1796                                 }
1797                         }
1798
1799
1800                         // From System.Array to any array-type
1801                         if (source_type == TypeManager.array_type &&
1802                             target_type.IsArray){
1803                                 return true;
1804                         }
1805
1806                         //
1807                         // From System delegate to any delegate-type
1808                         //
1809                         if (source_type == TypeManager.delegate_type &&
1810                             TypeManager.IsDelegateType (target_type))
1811                                 return true;
1812
1813                         return false;
1814                 }
1815
1816                 /// <summary>
1817                 ///   Implements Explicit Reference conversions
1818                 /// </summary>
1819                 static Expression ExplicitReferenceConversion (Expression source, Type target_type)
1820                 {
1821                         Type source_type = source.Type;
1822                         bool target_is_type_param = TypeManager.IsGenericParameter (target_type);
1823                         bool target_is_value_type = target_type.IsValueType;
1824
1825                         //
1826                         // From object to a generic parameter
1827                         //
1828                         if (source_type == TypeManager.object_type && target_is_type_param)
1829                                 return new UnboxCast (source, target_type);
1830
1831                         //
1832                         // Explicit type parameter conversion.
1833                         //
1834
1835                         if (TypeManager.IsGenericParameter (source_type))
1836                                 return ExplicitTypeParameterConversion (source, target_type);
1837
1838                         //
1839                         // From object to any reference type
1840                         //
1841                         if (source_type == TypeManager.object_type && !target_is_value_type)
1842                                 return new ClassCast (source, target_type);
1843
1844                         //
1845                         // Unboxing conversion.
1846                         //
1847                         if (((source_type == TypeManager.enum_type &&
1848                                 !(source is TypeCast)) ||
1849                                 source_type == TypeManager.value_type) && target_is_value_type)
1850                                 return new UnboxCast (source, target_type);
1851
1852                         //
1853                         // From any class S to any class-type T, provided S is a base class of T
1854                         //
1855                         if (TypeManager.IsSubclassOf (target_type, source_type))
1856                                 return new ClassCast (source, target_type);
1857
1858                         //
1859                         // From any interface type S to any interface T provided S is not derived from T
1860                         //
1861                         if (source_type.IsInterface && target_type.IsInterface){
1862                                 if (TypeManager.ImplementsInterface (source_type, target_type))
1863                                         return null;
1864                                 else
1865                                         return new ClassCast (source, target_type);
1866                         }
1867
1868                         //
1869                         // From any class type S to any interface T, provides S is not sealed
1870                         // and provided S does not implement T.
1871                         //
1872                         if (target_type.IsInterface &&
1873                                 (!source_type.IsSealed || source_type.IsArray) &&       // SRE: IsSealed does not work with aggregates
1874                                 !TypeManager.ImplementsInterface (source_type, target_type)) {
1875                                 return new ClassCast (source, target_type);
1876                         }
1877
1878                         //
1879                         // From any interface-type S to to any class type T, provided T is not
1880                         // sealed, or provided T implements S.
1881                         //
1882                         if (source_type.IsInterface) {
1883                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
1884                                         if (target_type.IsClass)
1885                                                 return new ClassCast (source, target_type);
1886                                         else
1887                                                 return new UnboxCast (source, target_type);
1888                                 }
1889
1890                                 //
1891                                 // From System.Collecitons.Generic.IList<T> and its base interfaces to a one-dimensional
1892                                 // array type S[], provided there is an implicit or explicit reference conversion from S to T.
1893                                 //
1894                                 if (IList_To_Array (source_type, target_type))
1895                                         return new ClassCast (source, target_type);
1896
1897                                 return null;
1898                         }
1899
1900                         // From an array type S with an element type Se to an array type T with an
1901                         // element type Te provided all the following are true:
1902                         //     * S and T differe only in element type, in other words, S and T
1903                         //       have the same number of dimensions.
1904                         //     * Both Se and Te are reference types
1905                         //     * An explicit referenc conversions exist from Se to Te
1906                         //
1907                         if (source_type.IsArray && target_type.IsArray) {
1908                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
1909
1910                                         Type source_element_type = TypeManager.GetElementType (source_type);
1911                                         Type target_element_type = TypeManager.GetElementType (target_type);
1912
1913                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
1914                                                 if (ExplicitReferenceConversionExists (source_element_type,
1915                                                                                        target_element_type))
1916                                                         return new ClassCast (source, target_type);
1917                                 }
1918                         }
1919
1920
1921                         // From System.Array to any array-type
1922                         if (source_type == TypeManager.array_type &&
1923                             target_type.IsArray) {
1924                                 return new ClassCast (source, target_type);
1925                         }
1926
1927                         //
1928                         // From System delegate to any delegate-type
1929                         //
1930                         if (source_type == TypeManager.delegate_type &&
1931                             TypeManager.IsDelegateType (target_type))
1932                                 return new ClassCast (source, target_type);
1933
1934                         return null;
1935                 }
1936
1937                 /// <summary>
1938                 ///   Performs an explicit conversion of the expression `expr' whose
1939                 ///   type is expr.Type to `target_type'.
1940                 /// </summary>
1941                 static public Expression ExplicitConversionCore (EmitContext ec, Expression expr,
1942                                                                  Type target_type, Location loc)
1943                 {
1944                         Type expr_type = expr.Type;
1945
1946                         // Explicit conversion includes implicit conversion and it used for enum underlying types too
1947                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, loc, true);
1948                         if (ne != null)
1949                                 return ne;
1950
1951                         //
1952                         // Unboxing conversions; only object types can be convertible to enum
1953                         //
1954                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
1955                                 return new UnboxCast (expr, target_type);
1956
1957                         if (TypeManager.IsEnumType (expr_type)) {
1958                                 Expression underlying = EmptyCast.Create (expr, TypeManager.GetEnumUnderlyingType (expr_type));
1959                                 expr = ExplicitConversionCore (ec, underlying, target_type, loc);
1960                                 if (expr != null)
1961                                         return expr;
1962
1963                                 return ExplicitUserConversion (ec, underlying, target_type, loc);
1964                         }
1965
1966                         if (TypeManager.IsEnumType (target_type)){
1967                                 if (expr_type == TypeManager.enum_type)
1968                                         return new UnboxCast (expr, target_type);
1969
1970                                 Expression ce = ExplicitConversionCore (ec, expr, TypeManager.GetEnumUnderlyingType (target_type), loc);
1971                                 if (ce != null)
1972                                         return EmptyCast.Create (ce, target_type);
1973
1974                                 //
1975                                 // LAMESPEC: IntPtr and UIntPtr conversion to any Enum is allowed
1976                                 //
1977                 if (expr_type == TypeManager.intptr_type || expr_type == TypeManager.uintptr_type) {
1978                                         ne = ExplicitUserConversion (ec, expr, TypeManager.GetEnumUnderlyingType (target_type), loc);
1979                                         if (ne != null)
1980                                                 return ExplicitConversionCore (ec, ne, target_type, loc);
1981                 }
1982
1983                                 return null;
1984                         }
1985
1986                         ne = ExplicitNumericConversion (expr, target_type);
1987                         if (ne != null)
1988                                 return ne;
1989
1990                         //
1991                         // Skip the ExplicitReferenceConversion because we can not convert
1992                         // from Null to a ValueType, and ExplicitReference wont check against
1993                         // null literal explicitly
1994                         //
1995                         if (expr_type != TypeManager.null_type){
1996                                 ne = ExplicitReferenceConversion (expr, target_type);
1997                                 if (ne != null)
1998                                         return ne;
1999                         }
2000
2001                         if (ec.InUnsafe){
2002                                 ne = ExplicitUnsafe (expr, target_type);
2003                                 if (ne != null)
2004                                         return ne;
2005                         }
2006
2007                         return null;
2008                 }
2009
2010                 public static Expression ExplicitUnsafe (Expression expr, Type target_type)
2011                 {
2012                         Type expr_type = expr.Type;
2013
2014                         if (target_type.IsPointer){
2015                                 if (expr_type.IsPointer)
2016                                         return EmptyCast.Create (expr, target_type);
2017
2018                                 if (expr_type == TypeManager.sbyte_type ||
2019                                         expr_type == TypeManager.short_type ||
2020                                         expr_type == TypeManager.int32_type)
2021                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
2022
2023                                 if (expr_type == TypeManager.ushort_type ||
2024                                         expr_type == TypeManager.uint32_type ||
2025                                         expr_type == TypeManager.uint64_type || expr_type == TypeManager.int64_type ||
2026                                         expr_type == TypeManager.byte_type)
2027                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
2028                         }
2029
2030                         if (expr_type.IsPointer){
2031                                 if (target_type == TypeManager.sbyte_type)
2032                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
2033                                 else if (target_type == TypeManager.byte_type)
2034                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
2035                                 else if (target_type == TypeManager.short_type)
2036                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
2037                                 else if (target_type == TypeManager.ushort_type)
2038                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
2039                                 else if (target_type == TypeManager.int32_type)
2040                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
2041                                 else if (target_type == TypeManager.uint32_type)
2042                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
2043                                 else if (target_type == TypeManager.uint64_type || target_type == TypeManager.int64_type)
2044                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
2045                         }
2046                         return null;
2047                 }
2048
2049                 /// <summary>
2050                 ///   Same as ExplicitConversion, only it doesn't include user defined conversions
2051                 /// </summary>
2052                 static public Expression ExplicitConversionStandard (EmitContext ec, Expression expr,
2053                                                                      Type target_type, Location l)
2054                 {
2055                         int errors = Report.Errors;
2056                         Expression ne = ImplicitConversionStandard (ec, expr, target_type, l);
2057                         if (Report.Errors > errors)
2058                                 return null;
2059
2060                         if (ne != null)
2061                                 return ne;
2062
2063                         ne = ExplicitNumericConversion (expr, target_type);
2064                         if (ne != null)
2065                                 return ne;
2066
2067                         ne = ExplicitReferenceConversion (expr, target_type);
2068                         if (ne != null)
2069                                 return ne;
2070
2071                         if (ec.InUnsafe && expr.Type == TypeManager.void_ptr_type && target_type.IsPointer)
2072                                 return EmptyCast.Create (expr, target_type);
2073
2074                         expr.Error_ValueCannotBeConverted (ec, l, target_type, true);
2075                         return null;
2076                 }
2077
2078                 /// <summary>
2079                 ///   Performs an explicit conversion of the expression `expr' whose
2080                 ///   type is expr.Type to `target_type'.
2081                 /// </summary>
2082                 static public Expression ExplicitConversion (EmitContext ec, Expression expr,
2083                         Type target_type, Location loc)
2084                 {
2085                         Expression e;
2086 #if GMCS_SOURCE
2087                         Type expr_type = expr.Type;
2088                         if (TypeManager.IsNullableType (target_type)) {
2089                                 if (TypeManager.IsNullableType (expr_type)) {
2090                                         e = new Nullable.LiftedConversion (
2091                                                 expr, target_type, false, true, loc).Resolve (ec);
2092                                         if (e != null)
2093                                                 return e;
2094                                 } else if (expr_type == TypeManager.object_type) {
2095                                         return new UnboxCast (expr, target_type);
2096                                 } else {
2097                                         Type target = TypeManager.GetTypeArguments (target_type) [0];
2098
2099                                         e = ExplicitConversionCore (ec, expr, target, loc);
2100                                         if (e != null)
2101                                                 return Nullable.Wrap.Create (e, target_type);
2102                                 }
2103                         } else if (TypeManager.IsNullableType (expr_type)) {
2104                                 e = Nullable.Unwrap.Create (expr, ec);
2105
2106                                 bool use_class_cast;
2107                                 if (ImplicitBoxingConversionExists (e, target_type, out use_class_cast))
2108                                         return new BoxedCast (expr, target_type);
2109
2110                                 e = ExplicitConversion (ec, e, target_type, loc);
2111                                 if (e != null)
2112                                         e = EmptyCast.Create (e, target_type);
2113                                 return e;
2114                         }
2115 #endif
2116                         e = ExplicitConversionCore (ec, expr, target_type, loc);
2117                         if (e != null)
2118                                 return e;
2119
2120                         e = ExplicitUserConversion (ec, expr, target_type, loc);
2121                         if (e != null)
2122                                 return e;
2123
2124                         expr.Error_ValueCannotBeConverted (ec, loc, target_type, true);
2125                         return null;
2126                 }
2127         }
2128 }