mcs/bmcs/convert.cs

   1 //
   2 // conversion.cs: various routines for implementing conversions.
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Ravi Pratap (ravi@ximian.com)
   7 //
   8 // (C) 2001, 2002, 2003 Ximian, Inc.
   9 //
  10
  11 namespace Mono.CSharp {
  12         using System;
  13         using System.Collections;
  14         using System.Diagnostics;
  15         using System.Reflection;
  16         using System.Reflection.Emit;
  17
  18         //
  19         // A container class for all the conversion operations
  20         //
  21         public class Convert {
  22                 //
  23                 // This is used to prettify the code: a null argument is allowed
  24                 // for ImplicitStandardConversion as long as it is known that
  25                 // no anonymous method will play a role.
  26                 //
  27                 // FIXME: renamed from `const' to `static' to allow bootstraping from older
  28                 // versions of the compiler that could not cope with this construct.
  29                 //
  30                 public static EmitContext ConstantEC = null;
  31
  32                 static public void Error_CannotConvertType (Location loc, Type source, Type target)
  33                 {
  34                         Report.Error (30, loc, "Cannot convert type '" +
  35                                       TypeManager.CSharpName (source) + "' to '" +
  36                                       TypeManager.CSharpName (target) + "'");
  37                 }
  38
  39                 static Expression TypeParameter_to_Null (Expression expr, Type target_type,
  40                                                          Location loc)
  41                 {
  42                         if (!TypeParameter_to_Null (target_type)) {
  43                                 Report.Error (403, loc, "Cannot convert null to the type " +
  44                                               "parameter `{0}' becaues it could be a value " +
  45                                               "type.  Consider using `default ({0})' instead.",
  46                                               target_type);
  47                                 return null;
  48                         }
  49
  50                         return new NullCast (expr, target_type);
  51                 }
  52
  53                 static bool TypeParameter_to_Null (Type target_type)
  54                 {
  55                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (target_type);
  56                         if (gc == null)
  57                                 return false;
  58
  59                         if (gc.HasReferenceTypeConstraint)
  60                                 return true;
  61                         if (gc.HasClassConstraint && !TypeManager.IsValueType (gc.ClassConstraint))
  62                                 return true;
  63
  64                         return false;
  65                 }
  66
  67                 static Type TypeParam_EffectiveBaseType (EmitContext ec, Type t)
  68                 {
  69                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (t);
  70                         if (gc == null)
  71                                 return TypeManager.object_type;
  72
  73                         return TypeParam_EffectiveBaseType (ec, gc);
  74                 }
  75
  76                 static Type TypeParam_EffectiveBaseType (EmitContext ec, GenericConstraints gc)
  77                 {
  78                         ArrayList list = new ArrayList ();
  79                         list.Add (gc.EffectiveBaseClass);
  80                         foreach (Type t in gc.InterfaceConstraints) {
  81                                 if (!t.IsGenericParameter)
  82                                         continue;
  83
  84                                 GenericConstraints new_gc = TypeManager.GetTypeParameterConstraints (t);
  85                                 if (new_gc != null)
  86                                         list.Add (TypeParam_EffectiveBaseType (ec, new_gc));
  87                         }
  88                         return FindMostEncompassedType (ec, list);
  89                 }
  90
  91                 static Expression TypeParameterConversion (Expression expr, bool is_reference, Type target_type)
  92                 {
  93                         if (is_reference)
  94                                 return new EmptyCast (expr, target_type);
  95                         else
  96                                 return new BoxedCast (expr, target_type);
  97                 }
  98
  99                 static Expression ImplicitTypeParameterConversion (EmitContext ec, Expression expr,
 100                                                                    Type target_type)
 101                 {
 102                         Type expr_type = expr.Type;
 103
 104                         GenericConstraints gc = TypeManager.GetTypeParameterConstraints (expr_type);
 105
 106                         if (gc == null) {
 107                                 if (target_type == TypeManager.object_type)
 108                                         return new BoxedCast (expr);
 109
 110                                 return null;
 111                         }
 112
 113                         // We're converting from a type parameter which is known to be a reference type.
 114                         bool is_reference = gc.IsReferenceType;
 115                         Type base_type = TypeParam_EffectiveBaseType (ec, gc);
 116
 117                         if (TypeManager.IsSubclassOf (base_type, target_type))
 118                                 return TypeParameterConversion (expr, is_reference, target_type);
 119
 120                         if (target_type.IsInterface) {
 121                                 if (TypeManager.ImplementsInterface (base_type, target_type))
 122                                         return TypeParameterConversion (expr, is_reference, target_type);
 123
 124                                 foreach (Type t in gc.InterfaceConstraints) {
 125                                         if (TypeManager.IsSubclassOf (t, target_type))
 126                                                 return TypeParameterConversion (expr, is_reference, target_type);
 127                                 }
 128                         }
 129
 130                         foreach (Type t in gc.InterfaceConstraints) {
 131                                 if (!t.IsGenericParameter)
 132                                         continue;
 133                                 if (TypeManager.IsSubclassOf (t, target_type))
 134                                         return TypeParameterConversion (expr, is_reference, target_type);
 135                         }
 136
 137                         return null;
 138                 }
 139
 140                 static EmptyExpression MyEmptyExpr;
 141                 static public Expression WideningReferenceConversion (EmitContext ec, Expression expr, Type target_type)
 142                 {
 143                         Type expr_type = expr.Type;
 144
 145                         if (expr_type == null && expr.eclass == ExprClass.MethodGroup){
 146                                 // if we are a method group, emit a warning
 147
 148                                 expr.Emit (null);
 149                         }
 150
 151                         if (expr_type == TypeManager.void_type)
 152                                 return null;
 153
 154                         if (expr_type.IsGenericParameter)
 155                                 return ImplicitTypeParameterConversion (ec, expr, target_type);
 156
 157                         //
 158                         // notice that it is possible to write "ValueType v = 1", the ValueType here
 159                         // is an abstract class, and not really a value type, so we apply the same rules.
 160                         //
 161                         if (target_type == TypeManager.object_type) {
 162                                 //
 163                                 // A pointer type cannot be converted to object
 164                                 //
 165                                 if (expr_type.IsPointer)
 166                                         return null;
 167
 168                                 if (TypeManager.IsValueType (expr_type))
 169                                         return new BoxedCast (expr);
 170                                 if (expr_type.IsClass || expr_type.IsInterface || expr_type == TypeManager.enum_type){
 171                                         if (expr_type == TypeManager.anonymous_method_type)
 172                                                 return null;
 173                                         return new EmptyCast (expr, target_type);
 174                                 }
 175
 176                                 return null;
 177                         } else if (target_type == TypeManager.value_type) {
 178                                 if (TypeManager.IsValueType (expr_type))
 179                                         return new BoxedCast (expr);
 180                                 if (expr_type == TypeManager.null_type)
 181                                         return new NullCast (expr, target_type);
 182
 183                                 return null;
 184                         } else if (TypeManager.IsSubclassOf (expr_type, target_type)) {
 185                                 //
 186                                 // Special case: enumeration to System.Enum.
 187                                 // System.Enum is not a value type, it is a class, so we need
 188                                 // a boxing conversion
 189                                 //
 190                                 if (expr_type.IsEnum || expr_type.IsGenericParameter)
 191                                         return new BoxedCast (expr);
 192
 193                                 return new EmptyCast (expr, target_type);
 194                         }
 195
 196                         // This code is kind of mirrored inside WideningStandardConversionExists
 197                         // with the small distinction that we only probe there
 198                         //
 199                         // Always ensure that the code here and there is in sync
 200
 201                         // from the null type to any reference-type.
 202                         if (expr_type == TypeManager.null_type){
 203                                 if (target_type.IsPointer)
 204                                         return new EmptyCast (expr, target_type);
 205
 206                                 if (!target_type.IsValueType)
 207                                         return new NullCast (expr, target_type);
 208
 209                                 // VB.NET specific: Convert Nothing to value types
 210
 211                                 Expression e = NothingToPrimitiveConstants (expr, target_type);
 212                                 if (e != null)
 213                                         return e;
 214
 215                                 return new NullCast (expr, target_type);
 216                         }
 217
 218                         // from any class-type S to any interface-type T.
 219                         if (target_type.IsInterface) {
 220                                 if (target_type != TypeManager.iconvertible_type &&
 221                                     expr_type.IsValueType && (expr is Constant) &&
 222                                     !(expr is IntLiteral || expr is BoolLiteral ||
 223                                       expr is FloatLiteral || expr is DoubleLiteral ||
 224                                       expr is LongLiteral || expr is CharLiteral ||
 225                                       expr is StringLiteral || expr is DecimalLiteral ||
 226                                       expr is UIntLiteral || expr is ULongLiteral)) {
 227                                         return null;
 228                                 }
 229
 230                                 if (TypeManager.ImplementsInterface (expr_type, target_type)){
 231                                         if (expr_type.IsGenericParameter || TypeManager.IsValueType (expr_type))
 232                                                 return new BoxedCast (expr, target_type);
 233                                         else
 234                                                 return new EmptyCast (expr, target_type);
 235                                 }
 236                         }
 237
 238                         // from any interface type S to interface-type T.
 239                         if (expr_type.IsInterface && target_type.IsInterface) {
 240                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 241                                         return new EmptyCast (expr, target_type);
 242                                 else
 243                                         return null;
 244                         }
 245
 246                         // from an array-type S to an array-type of type T
 247                         if (expr_type.IsArray && target_type.IsArray) {
 248                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 249
 250                                         Type expr_element_type = TypeManager.GetElementType (expr_type);
 251
 252                                         if (MyEmptyExpr == null)
 253                                                 MyEmptyExpr = new EmptyExpression ();
 254
 255                                         MyEmptyExpr.SetType (expr_element_type);
 256                                         Type target_element_type = TypeManager.GetElementType (target_type);
 257
 258                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 259                                                 if (WideningStandardConversionExists (ConstantEC, MyEmptyExpr,
 260                                                                                       target_element_type))
 261                                                         return new EmptyCast (expr, target_type);
 262                                 }
 263                         }
 264
 265                         // from an array-type to System.Array
 266                         if (expr_type.IsArray && target_type == TypeManager.array_type)
 267                                 return new EmptyCast (expr, target_type);
 268
 269                         // from an array-type of type T to IEnumerable<T>
 270                         if (expr_type.IsArray && TypeManager.IsIEnumerable (expr_type, target_type))
 271                                 return new EmptyCast (expr, target_type);
 272
 273                         // from any delegate type to System.Delegate
 274                         if ((expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type)) &&
 275                             target_type == TypeManager.delegate_type)
 276                                 return new EmptyCast (expr, target_type);
 277
 278                         // from any array-type or delegate type into System.ICloneable.
 279                         if (expr_type.IsArray ||
 280                             expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type))
 281                                 if (target_type == TypeManager.icloneable_type)
 282                                         return new EmptyCast (expr, target_type);
 283
 284                         // from a generic type definition to a generic instance.
 285                         if (TypeManager.IsEqual (expr_type, target_type))
 286                                 return new EmptyCast (expr, target_type);
 287
 288                         return null;
 289                 }
 290
 291                 //
 292                 // Tests whether an implicit reference conversion exists between expr_type
 293                 // and target_type
 294                 //
 295                 public static bool WideningReferenceConversionExists (EmitContext ec, Expression expr, Type target_type)
 296                 {
 297                         Type expr_type = expr.Type;
 298
 299                         if (expr_type.IsGenericParameter)
 300                                 return ImplicitTypeParameterConversion (ec, expr, target_type) != null;
 301
 302                         //
 303                         // This is the boxed case.
 304                         //
 305                         if (target_type == TypeManager.object_type) {
 306                                 if (expr_type.IsClass || TypeManager.IsValueType (expr_type) ||
 307                                     expr_type.IsInterface || expr_type == TypeManager.enum_type)
 308                                         if (target_type != TypeManager.anonymous_method_type)
 309                                         return true;
 310
 311                                 return false;
 312                         } else if (TypeManager.IsSubclassOf (expr_type, target_type))
 313                                 return true;
 314
 315                         // Please remember that all code below actually comes
 316                         // from WideningReferenceConversion so make sure code remains in sync
 317
 318                         // from any class-type S to any interface-type T.
 319                         if (target_type.IsInterface) {
 320                                 if (target_type != TypeManager.iconvertible_type &&
 321                                     expr_type.IsValueType && (expr is Constant) &&
 322                                     !(expr is IntLiteral || expr is BoolLiteral ||
 323                                       expr is FloatLiteral || expr is DoubleLiteral ||
 324                                       expr is LongLiteral || expr is CharLiteral ||
 325                                       expr is StringLiteral || expr is DecimalLiteral ||
 326                                       expr is UIntLiteral || expr is ULongLiteral)) {
 327                                         return false;
 328                                 }
 329
 330                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 331                                         return true;
 332                         }
 333
 334                         // from any interface type S to interface-type T.
 335                         if (expr_type.IsInterface && target_type.IsInterface)
 336                                 if (TypeManager.ImplementsInterface (expr_type, target_type))
 337                                         return true;
 338
 339                         // from an array-type S to an array-type of type T
 340                         if (expr_type.IsArray && target_type.IsArray) {
 341                                 if (expr_type.GetArrayRank () == target_type.GetArrayRank ()) {
 342
 343                                         Type expr_element_type = expr_type.GetElementType ();
 344
 345                                         if (MyEmptyExpr == null)
 346                                                 MyEmptyExpr = new EmptyExpression ();
 347
 348                                         MyEmptyExpr.SetType (expr_element_type);
 349                                         Type target_element_type = TypeManager.GetElementType (target_type);
 350
 351                                         if (!expr_element_type.IsValueType && !target_element_type.IsValueType)
 352                                                 if (WideningStandardConversionExists (ConstantEC, MyEmptyExpr,
 353                                                                                       target_element_type))
 354                                                         return true;
 355                                 }
 356                         }
 357
 358                         // from an array-type to System.Array
 359                         if (expr_type.IsArray && (target_type == TypeManager.array_type))
 360                                 return true;
 361
 362                         // from an array-type of type T to IEnumerable<T>
 363                         if (expr_type.IsArray && TypeManager.IsIEnumerable (expr_type, target_type))
 364                                 return true;
 365
 366                         // from any delegate type to System.Delegate
 367                         if ((expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type)) &&
 368                             target_type == TypeManager.delegate_type)
 369                                 if (target_type.IsAssignableFrom (expr_type))
 370                                         return true;
 371
 372                         // from any array-type or delegate type into System.ICloneable.
 373                         if (expr_type.IsArray ||
 374                             expr_type == TypeManager.delegate_type || TypeManager.IsDelegateType (expr_type))
 375                                 if (target_type == TypeManager.icloneable_type)
 376                                         return true;
 377
 378                         // from the null type to any reference-type.
 379                         if (expr_type == TypeManager.null_type){
 380                                 if (target_type.IsPointer)
 381                                         return true;
 382
 383                                 if (!target_type.IsValueType)
 384                                         return true;
 385                         }
 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                 /// <summary>
 395                 ///   Implicit Numeric Conversions.
 396                 ///
 397                 ///   expr is the expression to convert, returns a new expression of type
 398                 ///   target_type or null if an implicit conversion is not possible.
 399                 /// </summary>
 400                 static public Expression WideningNumericConversion (EmitContext ec, Expression expr,
 401                                                                     Type target_type, Location loc)
 402                 {
 403                         Type expr_type = expr.Type;
 404
 405                         //
 406                         // Attempt to do the implicit constant expression conversions
 407
 408                         if (expr is Constant){
 409                                 Expression e;
 410
 411                                 e = WideningConstantConversions (target_type, (Constant) expr);
 412                                 if (e != null)
 413                                         return e;
 414
 415                                 if (expr is IntConstant){
 416                                         e = TryWideningIntConversion (target_type, (IntConstant) expr);
 417
 418                                         if (e != null)
 419                                                 return e;
 420                                 }
 421                         }
 422
 423                         Type real_target_type = target_type;
 424
 425                         // VB.NET specific: Convert an enum to it's
 426                         // underlying numeric type or any type that
 427                         // it's underlyinmg type has widening
 428                         // conversion to.
 429
 430                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
 431                                 if (target_type == TypeManager.enum_type ||
 432                                     target_type == TypeManager.object_type) {
 433                                         if (expr is EnumConstant)
 434                                                 expr = ((EnumConstant) expr).Child;
 435                                         // We really need all these casts here .... :-(
 436                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
 437                                         return new EmptyCast (expr, target_type);
 438                                 }
 439
 440                                 //
 441                                 // Notice that we have kept the expr_type unmodified, which is only
 442                                 // used later on to
 443                                 if (expr is EnumConstant)
 444                                         expr = ((EnumConstant) expr).Child;
 445                                 else
 446                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
 447                                 expr_type = expr.Type;
 448
 449                                 if (expr_type == target_type)
 450                                         return expr;
 451                         }
 452
 453                         if (expr_type == TypeManager.sbyte_type){
 454                                 //
 455                                 // From sbyte to short, int, long, float, double.
 456                                 //
 457                                 if (real_target_type == TypeManager.int32_type)
 458                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 459                                 if (real_target_type == TypeManager.int64_type)
 460                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 461                                 if (real_target_type == TypeManager.double_type)
 462                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 463                                 if (real_target_type == TypeManager.float_type)
 464                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 465                                 if (real_target_type == TypeManager.short_type)
 466                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
 467                         } else if (expr_type == TypeManager.byte_type){
 468                                 //
 469                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 470                                 //
 471                                 if ((real_target_type == TypeManager.short_type) ||
 472                                     (real_target_type == TypeManager.ushort_type) ||
 473                                     (real_target_type == TypeManager.int32_type) ||
 474                                     (real_target_type == TypeManager.uint32_type))
 475                                         return new EmptyCast (expr, target_type);
 476
 477                                 if (real_target_type == TypeManager.uint64_type)
 478                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 479                                 if (real_target_type == TypeManager.int64_type)
 480                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 481                                 if (real_target_type == TypeManager.float_type)
 482                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 483                                 if (real_target_type == TypeManager.double_type)
 484                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 485                                 if (real_target_type == TypeManager.decimal_type)
 486                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 487                         } else if (expr_type == TypeManager.short_type){
 488                                 //
 489                                 // From short to int, long, float, double
 490                                 //
 491                                 if (real_target_type == TypeManager.int32_type)
 492                                         return new EmptyCast (expr, target_type);
 493                                 if (real_target_type == TypeManager.int64_type)
 494                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 495                                 if (real_target_type == TypeManager.double_type)
 496                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 497                                 if (real_target_type == TypeManager.float_type)
 498                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 499                                 if (real_target_type == TypeManager.decimal_type)
 500                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 501                         } else if (expr_type == TypeManager.ushort_type){
 502                                 //
 503                                 // From ushort to int, uint, long, ulong, float, double
 504                                 //
 505                                 if (real_target_type == TypeManager.uint32_type)
 506                                         return new EmptyCast (expr, target_type);
 507
 508                                 if (real_target_type == TypeManager.uint64_type)
 509                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 510                                 if (real_target_type == TypeManager.int32_type)
 511                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
 512                                 if (real_target_type == TypeManager.int64_type)
 513                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 514                                 if (real_target_type == TypeManager.double_type)
 515                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 516                                 if (real_target_type == TypeManager.float_type)
 517                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 518                         } else if (expr_type == TypeManager.int32_type){
 519                                 //
 520                                 // From int to long, float, double
 521                                 //
 522                                 if (real_target_type == TypeManager.int64_type)
 523                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
 524                                 if (real_target_type == TypeManager.double_type)
 525                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 526                                 if (real_target_type == TypeManager.float_type)
 527                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 528                                 if (real_target_type == TypeManager.decimal_type)
 529                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 530                         } else if (expr_type == TypeManager.uint32_type){
 531                                 //
 532                                 // From uint to long, ulong, float, double
 533                                 //
 534                                 if (real_target_type == TypeManager.int64_type)
 535                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 536                                 if (real_target_type == TypeManager.uint64_type)
 537                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
 538                                 if (real_target_type == TypeManager.double_type)
 539                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 540                                                                OpCodes.Conv_R8);
 541                                 if (real_target_type == TypeManager.float_type)
 542                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 543                                                                OpCodes.Conv_R4);
 544                         } else if (expr_type == TypeManager.uint64_type){
 545                                 //
 546                                 // From ulong to float, double
 547                                 //
 548                                 if (real_target_type == TypeManager.double_type)
 549                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 550                                                                OpCodes.Conv_R8);
 551                                 if (real_target_type == TypeManager.float_type)
 552                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
 553                                                                OpCodes.Conv_R4);
 554                         } else if (expr_type == TypeManager.int64_type){
 555                                 //
 556                                 // From long/ulong to float, double
 557                                 //
 558                                 if (real_target_type == TypeManager.double_type)
 559                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 560                                 if (real_target_type == TypeManager.float_type)
 561                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
 562                                 if (real_target_type == TypeManager.decimal_type)
 563                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
 564                         } else if (expr_type == TypeManager.float_type){
 565                                 //
 566                                 // float to double
 567                                 //
 568                                 if (real_target_type == TypeManager.double_type)
 569                                         return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
 570                         } else if (expr_type == TypeManager.decimal_type){
 571                                 //
 572                                 // From decimal to float, double
 573                                 //
 574                                 if (real_target_type == TypeManager.double_type)
 575                                         return new HelperMethodInvocation (ec, loc, TypeManager.double_type, TypeManager.convert_to_double_decimal, expr);
 576                                 if (real_target_type == TypeManager.float_type)
 577                                         return new HelperMethodInvocation (ec, loc, TypeManager.float_type, TypeManager.convert_to_single_decimal, expr);
 578                         }
 579
 580                         return null;
 581                 }
 582
 583
 584                 /// <summary>
 585                 ///  Same as WideningStandardConversionExists except that it also looks at
 586                 ///  implicit user defined conversions - needed for overload resolution
 587                 /// </summary>
 588                 public static bool WideningConversionExists (EmitContext ec, Expression expr, Type target_type)
 589                 {
 590                         if (expr is NullLiteral) {
 591                                 if (target_type.IsGenericParameter)
 592                                         return TypeParameter_to_Null (target_type);
 593
 594                                 if (TypeManager.IsNullableType (target_type))
 595                                         return true;
 596                         }
 597
 598                         if (WideningStandardConversionExists (ec, expr, target_type))
 599                                 return true;
 600
 601                         //
 602                         // VB.NET has no notion of User defined conversions
 603                         //
 604
 605 //                      Expression dummy = ImplicitUserConversion (ec, expr, target_type, Location.Null);
 606
 607 //                      if (dummy != null)
 608 //                              return true;
 609
 610                         return false;
 611                 }
 612
 613                 //
 614                 // VB.NET has no notion of User defined conversions
 615                 //
 616
 617 //              public static bool ImplicitUserConversionExists (EmitContext ec, Type source, Type target)
 618 //              {
 619 //                      Expression dummy = ImplicitUserConversion (
 620 //                              ec, new EmptyExpression (source), target, Location.Null);
 621 //                      return dummy != null;
 622 //              }
 623
 624                 /// <summary>
 625                 ///  Determines if a standard implicit conversion exists from
 626                 ///  expr_type to target_type
 627                 ///
 628                 ///  ec should point to a real EmitContext if expr.Type is TypeManager.anonymous_method_type.
 629                 /// </summary>
 630                 public static bool WideningStandardConversionExists (EmitContext ec, Expression expr, Type target_type)
 631                 {
 632                         Type expr_type = expr.Type;
 633
 634                         if (expr_type == TypeManager.void_type)
 635                                 return false;
 636
 637                         //Console.WriteLine ("Expr is {0}", expr);
 638                         //Console.WriteLine ("{0} -> {1} ?", expr_type, target_type);
 639                         if (expr_type.Equals (target_type))
 640                                 return true;
 641
 642
 643                         // First numeric conversions
 644
 645                         if (expr_type == TypeManager.sbyte_type){
 646                                 //
 647                                 // From sbyte to short, int, long, float, double.
 648                                 //
 649                                 if ((target_type == TypeManager.int32_type) ||
 650                                     (target_type == TypeManager.int64_type) ||
 651                                     (target_type == TypeManager.double_type) ||
 652                                     (target_type == TypeManager.float_type)  ||
 653                                     (target_type == TypeManager.short_type) ||
 654                                     (target_type == TypeManager.decimal_type))
 655                                         return true;
 656
 657                         } else if (expr_type == TypeManager.byte_type){
 658                                 //
 659                                 // From byte to short, ushort, int, uint, long, ulong, float, double
 660                                 //
 661                                 if ((target_type == TypeManager.short_type) ||
 662                                     (target_type == TypeManager.ushort_type) ||
 663                                     (target_type == TypeManager.int32_type) ||
 664                                     (target_type == TypeManager.uint32_type) ||
 665                                     (target_type == TypeManager.uint64_type) ||
 666                                     (target_type == TypeManager.int64_type) ||
 667                                     (target_type == TypeManager.float_type) ||
 668                                     (target_type == TypeManager.double_type) ||
 669                                     (target_type == TypeManager.decimal_type))
 670                                         return true;
 671
 672                         } else if (expr_type == TypeManager.short_type){
 673                                 //
 674                                 // From short to int, long, float, double
 675                                 //
 676                                 if ((target_type == TypeManager.int32_type) ||
 677                                     (target_type == TypeManager.int64_type) ||
 678                                     (target_type == TypeManager.double_type) ||
 679                                     (target_type == TypeManager.float_type) ||
 680                                     (target_type == TypeManager.decimal_type))
 681                                         return true;
 682
 683                         } else if (expr_type == TypeManager.ushort_type){
 684                                 //
 685                                 // From ushort to int, uint, long, ulong, float, double
 686                                 //
 687                                 if ((target_type == TypeManager.uint32_type) ||
 688                                     (target_type == TypeManager.uint64_type) ||
 689                                     (target_type == TypeManager.int32_type) ||
 690                                     (target_type == TypeManager.int64_type) ||
 691                                     (target_type == TypeManager.double_type) ||
 692                                     (target_type == TypeManager.float_type) ||
 693                                     (target_type == TypeManager.decimal_type))
 694                                         return true;
 695
 696                         } else if (expr_type == TypeManager.int32_type){
 697                                 //
 698                                 // From int to long, float, double
 699                                 //
 700                                 if ((target_type == TypeManager.int64_type) ||
 701                                     (target_type == TypeManager.double_type) ||
 702                                     (target_type == TypeManager.float_type) ||
 703                                     (target_type == TypeManager.decimal_type))
 704                                         return true;
 705
 706                         } else if (expr_type == TypeManager.uint32_type){
 707                                 //
 708                                 // From uint to long, ulong, float, double
 709                                 //
 710                                 if ((target_type == TypeManager.int64_type) ||
 711                                     (target_type == TypeManager.uint64_type) ||
 712                                     (target_type == TypeManager.double_type) ||
 713                                     (target_type == TypeManager.float_type) ||
 714                                     (target_type == TypeManager.decimal_type))
 715                                         return true;
 716
 717                         } else if ((expr_type == TypeManager.uint64_type) ||
 718                                    (expr_type == TypeManager.int64_type)) {
 719                                 //
 720                                 // From long/ulong to float, double
 721                                 //
 722                                 if ((target_type == TypeManager.double_type) ||
 723                                     (target_type == TypeManager.float_type) ||
 724                                     (target_type == TypeManager.decimal_type))
 725                                         return true;
 726
 727                         } else if (expr_type == TypeManager.char_type){
 728                                 //
 729                                 // From char to ushort, int, uint, long, ulong, float, double
 730                                 //
 731                                 if ((target_type == TypeManager.ushort_type) ||
 732                                     (target_type == TypeManager.int32_type) ||
 733                                     (target_type == TypeManager.uint32_type) ||
 734                                     (target_type == TypeManager.uint64_type) ||
 735                                     (target_type == TypeManager.int64_type) ||
 736                                     (target_type == TypeManager.float_type) ||
 737                                     (target_type == TypeManager.double_type) ||
 738                                     (target_type == TypeManager.decimal_type))
 739                                         return true;
 740
 741                         } else if (expr_type == TypeManager.float_type){
 742                                 //
 743                                 // float to double
 744                                 //
 745                                 if (target_type == TypeManager.double_type)
 746                                         return true;
 747                         }
 748
 749                         if (expr.eclass == ExprClass.MethodGroup){
 750                                 if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
 751                                         MethodGroupExpr mg = expr as MethodGroupExpr;
 752                                         if (mg != null){
 753                                                 //
 754                                                 // This should not happen frequently, so we can create an object
 755                                                 // to test compatibility
 756                                                 //
 757                                                 Expression c = ImplicitDelegateCreation.Create (ec, mg, target_type, Location.Null);
 758                                                 return c != null;
 759                                         }
 760                                 }
 761                         }
 762
 763                         if (WideningReferenceConversionExists (ec, expr, target_type))
 764                                 return true;
 765
 766                         //
 767                         // Implicit Constant Expression Conversions
 768                         //
 769                         if (expr is IntConstant){
 770                                 int value = ((IntConstant) expr).Value;
 771
 772                                 if (target_type == TypeManager.sbyte_type){
 773                                         if (value >= SByte.MinValue && value <= SByte.MaxValue)
 774                                                 return true;
 775                                 } else if (target_type == TypeManager.byte_type){
 776                                         if (Byte.MinValue >= 0 && value <= Byte.MaxValue)
 777                                                 return true;
 778                                 } else if (target_type == TypeManager.short_type){
 779                                         if (value >= Int16.MinValue && value <= Int16.MaxValue)
 780                                                 return true;
 781                                 } else if (target_type == TypeManager.ushort_type){
 782                                         if (value >= UInt16.MinValue && value <= UInt16.MaxValue)
 783                                                 return true;
 784                                 } else if (target_type == TypeManager.uint32_type){
 785                                         if (value >= 0)
 786                                                 return true;
 787                                 } else if (target_type == TypeManager.uint64_type){
 788                                          //
 789                                          // we can optimize this case: a positive int32
 790                                          // always fits on a uint64.  But we need an opcode
 791                                          // to do it.
 792                                          //
 793                                         if (value >= 0)
 794                                                 return true;
 795                                 }
 796
 797                                 if (value == 0 && expr is IntLiteral && TypeManager.IsEnumType (target_type))
 798                                         return true;
 799                         }
 800
 801                         if (expr is LongConstant && target_type == TypeManager.uint64_type){
 802                                 //
 803                                 // Try the implicit constant expression conversion
 804                                 // from long to ulong, instead of a nice routine,
 805                                 // we just inline it
 806                                 //
 807                                 long v = ((LongConstant) expr).Value;
 808                                 if (v > 0)
 809                                         return true;
 810                         }
 811
 812                         if ((target_type == TypeManager.enum_type ||
 813                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
 814                              expr is IntLiteral){
 815                                 IntLiteral i = (IntLiteral) expr;
 816
 817                                 if (i.Value == 0)
 818                                         return true;
 819                         }
 820
 821                         //
 822                         // If `expr_type' implements `target_type' (which is an iface)
 823                         // see TryWideningIntConversion
 824                         //
 825                         if (target_type.IsInterface && target_type.IsAssignableFrom (expr_type))
 826                                 return true;
 827
 828                         if (target_type == TypeManager.void_ptr_type && expr_type.IsPointer)
 829                                 return true;
 830
 831                         if (TypeManager.IsNullableType (expr_type) && TypeManager.IsNullableType (target_type))
 832                                 return true;
 833
 834                         if (expr_type == TypeManager.anonymous_method_type){
 835                                 if (!TypeManager.IsDelegateType (target_type))
 836                                         return false;
 837
 838                                 AnonymousMethod am = (AnonymousMethod) expr;
 839
 840                                 Expression conv = am.Compatible (ec, target_type, true);
 841                                 if (conv != null)
 842                                         return true;
 843                         }
 844
 845                         return false;
 846                 }
 847
 848                 //
 849                 // Used internally by FindMostEncompassedType, this is used
 850                 // to avoid creating lots of objects in the tight loop inside
 851                 // FindMostEncompassedType
 852                 //
 853                 static EmptyExpression priv_fmet_param;
 854
 855                 /// <summary>
 856                 ///  Finds "most encompassed type" according to the spec (13.4.2)
 857                 ///  amongst the methods in the MethodGroupExpr
 858                 /// </summary>
 859                 static Type FindMostEncompassedType (EmitContext ec, ArrayList types)
 860                 {
 861                         Type best = null;
 862
 863                         if (priv_fmet_param == null)
 864                                 priv_fmet_param = new EmptyExpression ();
 865
 866                         foreach (Type t in types){
 867                                 priv_fmet_param.SetType (t);
 868
 869                                 if (best == null) {
 870                                         best = t;
 871                                         continue;
 872                                 }
 873
 874                                 if (WideningStandardConversionExists (ec, priv_fmet_param, best))
 875                                         best = t;
 876                         }
 877
 878                         return best;
 879                 }
 880
 881                 //
 882                 // Used internally by FindMostEncompassingType, this is used
 883                 // to avoid creating lots of objects in the tight loop inside
 884                 // FindMostEncompassingType
 885                 //
 886                 static EmptyExpression priv_fmee_ret;
 887
 888                 /// <summary>
 889                 ///  Finds "most encompassing type" according to the spec (13.4.2)
 890                 ///  amongst the types in the given set
 891                 /// </summary>
 892                 static Type FindMostEncompassingType (EmitContext ec, ArrayList types)
 893                 {
 894                         Type best = null;
 895
 896                         if (priv_fmee_ret == null)
 897                                 priv_fmee_ret = new EmptyExpression ();
 898
 899                         foreach (Type t in types){
 900                                 priv_fmee_ret.SetType (best);
 901
 902                                 if (best == null) {
 903                                         best = t;
 904                                         continue;
 905                                 }
 906
 907                                 if (WideningStandardConversionExists (ec, priv_fmee_ret, t))
 908                                         best = t;
 909                         }
 910
 911                         return best;
 912                 }
 913
 914                 //
 915                 // Used to avoid creating too many objects
 916                 //
 917                 static EmptyExpression priv_fms_expr;
 918
 919                 /// <summary>
 920                 ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
 921                 ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
 922                 ///   for explicit and implicit conversion operators.
 923                 /// </summary>
 924                 static public Type FindMostSpecificSource (EmitContext ec, MethodGroupExpr me,
 925                                                            Expression source, bool apply_explicit_conv_rules,
 926                                                            Location loc)
 927                 {
 928                         ArrayList src_types_set = new ArrayList ();
 929
 930                         if (priv_fms_expr == null)
 931                                 priv_fms_expr = new EmptyExpression ();
 932
 933                         //
 934                         // If any operator converts from S then Sx = S
 935                         //
 936                         Type source_type = source.Type;
 937                         foreach (MethodBase mb in me.Methods){
 938                                 ParameterData pd = Invocation.GetParameterData (mb);
 939                                 Type param_type = pd.ParameterType (0);
 940
 941                                 if (param_type == source_type)
 942                                         return param_type;
 943
 944                                 if (apply_explicit_conv_rules) {
 945                                         //
 946                                         // From the spec :
 947                                         // Find the set of applicable user-defined conversion operators, U.  This set
 948                                         // consists of the
 949                                         // user-defined implicit or explicit conversion operators declared by
 950                                         // the classes or structs in D that convert from a type encompassing
 951                                         // or encompassed by S to a type encompassing or encompassed by T
 952                                         //
 953                                         priv_fms_expr.SetType (param_type);
 954                                         if (WideningStandardConversionExists (ec, priv_fms_expr, source_type))
 955                                                 src_types_set.Add (param_type);
 956                                         else {
 957                                                 if (WideningStandardConversionExists (ec, source, param_type))
 958                                                         src_types_set.Add (param_type);
 959                                         }
 960                                 } else {
 961                                         //
 962                                         // Only if S is encompassed by param_type
 963                                         //
 964                                         if (WideningStandardConversionExists (ec, source, param_type))
 965                                                 src_types_set.Add (param_type);
 966                                 }
 967                         }
 968
 969                         //
 970                         // Explicit Conv rules
 971                         //
 972                         if (apply_explicit_conv_rules) {
 973                                 ArrayList candidate_set = new ArrayList ();
 974
 975                                 foreach (Type param_type in src_types_set){
 976                                         if (WideningStandardConversionExists (ec, source, param_type))
 977                                                 candidate_set.Add (param_type);
 978                                 }
 979
 980                                 if (candidate_set.Count != 0)
 981                                         return FindMostEncompassedType (ec, candidate_set);
 982                         }
 983
 984                         //
 985                         // Final case
 986                         //
 987                         if (apply_explicit_conv_rules)
 988                                 return FindMostEncompassingType (ec, src_types_set);
 989                         else
 990                                 return FindMostEncompassedType (ec, src_types_set);
 991                 }
 992
 993                 //
 994                 // Useful in avoiding proliferation of objects
 995                 //
 996                 static EmptyExpression priv_fmt_expr;
 997
 998                 /// <summary>
 999                 ///  Finds the most specific target Tx according to section 13.4.4
1000                 /// </summary>
1001                 static public Type FindMostSpecificTarget (EmitContext ec, MethodGroupExpr me,
1002                                                            Type target, bool apply_explicit_conv_rules,
1003                                                            Location loc)
1004                 {
1005                         ArrayList tgt_types_set = new ArrayList ();
1006
1007                         if (priv_fmt_expr == null)
1008                                 priv_fmt_expr = new EmptyExpression ();
1009
1010                         //
1011                         // If any operator converts to T then Tx = T
1012                         //
1013                         foreach (MethodInfo mi in me.Methods){
1014                                 Type ret_type = mi.ReturnType;
1015
1016                                 if (ret_type == target)
1017                                         return ret_type;
1018
1019                                 if (apply_explicit_conv_rules) {
1020                                         //
1021                                         // From the spec :
1022                                         // Find the set of applicable user-defined conversion operators, U.
1023                                         //
1024                                         // This set consists of the
1025                                         // user-defined implicit or explicit conversion operators declared by
1026                                         // the classes or structs in D that convert from a type encompassing
1027                                         // or encompassed by S to a type encompassing or encompassed by T
1028                                         //
1029                                         priv_fms_expr.SetType (ret_type);
1030                                         if (WideningStandardConversionExists (ec, priv_fms_expr, target))
1031                                                 tgt_types_set.Add (ret_type);
1032                                         else {
1033                                                 priv_fms_expr.SetType (target);
1034                                                 if (WideningStandardConversionExists (ec, priv_fms_expr, ret_type))
1035                                                         tgt_types_set.Add (ret_type);
1036                                         }
1037                                 } else {
1038                                         //
1039                                         // Only if T is encompassed by param_type
1040                                         //
1041                                         priv_fms_expr.SetType (ret_type);
1042                                         if (WideningStandardConversionExists (ec, priv_fms_expr, target))
1043                                                 tgt_types_set.Add (ret_type);
1044                                 }
1045                         }
1046
1047                         //
1048                         // Explicit conv rules
1049                         //
1050                         if (apply_explicit_conv_rules) {
1051                                 ArrayList candidate_set = new ArrayList ();
1052
1053                                 foreach (Type ret_type in tgt_types_set){
1054                                         priv_fmt_expr.SetType (ret_type);
1055
1056                                         if (WideningStandardConversionExists (ec, priv_fmt_expr, target))
1057                                                 candidate_set.Add (ret_type);
1058                                 }
1059
1060                                 if (candidate_set.Count != 0)
1061                                         return FindMostEncompassingType (ec, candidate_set);
1062                         }
1063
1064                         //
1065                         // Okay, final case !
1066                         //
1067                         if (apply_explicit_conv_rules)
1068                                 return FindMostEncompassedType (ec, tgt_types_set);
1069                         else
1070                                 return FindMostEncompassingType (ec, tgt_types_set);
1071                 }
1072
1073                 /// <summary>
1074                 ///  User-defined Implicit conversions
1075                 /// </summary>
1076
1077                 //
1078                 // VB.NET has no notion of User defined conversions
1079                 //
1080
1081 //              static public Expression ImplicitUserConversion (EmitContext ec, Expression source,
1082 //                                                               Type target, Location loc)
1083 //              {
1084 //                      return UserDefinedConversion (ec, source, target, loc, false);
1085 //              }
1086
1087                 /// <summary>
1088                 ///  User-defined Explicit conversions
1089                 /// </summary>
1090
1091                 //
1092                 // VB.NET has no notion of User defined conversions
1093                 //
1094
1095 //              static public Expression ExplicitUserConversion (EmitContext ec, Expression source,
1096 //                                                               Type target, Location loc)
1097 //              {
1098 //                      return UserDefinedConversion (ec, source, target, loc, true);
1099 //              }
1100
1101                 static DoubleHash explicit_conv = new DoubleHash (100);
1102                 static DoubleHash implicit_conv = new DoubleHash (100);
1103                 /// <summary>
1104                 ///   Computes the MethodGroup for the user-defined conversion
1105                 ///   operators from source_type to target_type.  `look_for_explicit'
1106                 ///   controls whether we should also include the list of explicit
1107                 ///   operators
1108                 /// </summary>
1109                 static MethodGroupExpr GetConversionOperators (EmitContext ec,
1110                                                                Type source_type, Type target_type,
1111                                                                Location loc, bool look_for_explicit)
1112                 {
1113                         Expression mg1 = null, mg2 = null;
1114                         Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
1115                         string op_name;
1116
1117                         op_name = "op_Implicit";
1118
1119                         MethodGroupExpr union3;
1120                         object r;
1121                         if ((look_for_explicit ? explicit_conv : implicit_conv).Lookup (source_type, target_type, out r))
1122                                 return (MethodGroupExpr) r;
1123
1124                         mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
1125                         if (source_type.BaseType != null)
1126                                 mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
1127
1128                         if (mg1 == null)
1129                                 union3 = (MethodGroupExpr) mg2;
1130                         else if (mg2 == null)
1131                                 union3 = (MethodGroupExpr) mg1;
1132                         else
1133                                 union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
1134
1135                         mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
1136                         if (mg1 != null){
1137                                 if (union3 != null)
1138                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
1139                                 else
1140                                         union3 = (MethodGroupExpr) mg1;
1141                         }
1142
1143                         if (target_type.BaseType != null)
1144                                 mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
1145
1146                         if (mg1 != null){
1147                                 if (union3 != null)
1148                                         union3 = Invocation.MakeUnionSet (union3, mg1, loc);
1149                                 else
1150                                         union3 = (MethodGroupExpr) mg1;
1151                         }
1152
1153                         MethodGroupExpr union4 = null;
1154
1155                         if (look_for_explicit) {
1156                                 op_name = "op_Explicit";
1157
1158                                 mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
1159                                 if (source_type.BaseType != null)
1160                                         mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
1161
1162                                 mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
1163                                 if (target_type.BaseType != null)
1164                                         mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
1165
1166                                 MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
1167                                 MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
1168
1169                                 union4 = Invocation.MakeUnionSet (union5, union6, loc);
1170                         }
1171
1172                         MethodGroupExpr ret = Invocation.MakeUnionSet (union3, union4, loc);
1173                         (look_for_explicit ? explicit_conv : implicit_conv).Insert (source_type, target_type, ret);
1174                         return ret;
1175                 }
1176
1177                 /// <summary>
1178                 ///   User-defined conversions
1179                 /// </summary>
1180
1181                 //
1182                 // VB.NET has no notion of User defined conversions. This method is not used.
1183                 //
1184                 static public Expression UserDefinedConversion (EmitContext ec, Expression source,
1185                                                                 Type target, Location loc,
1186                                                                 bool look_for_explicit)
1187                 {
1188                         MethodGroupExpr union;
1189                         Type source_type = source.Type;
1190                         MethodBase method = null;
1191
1192                         if (TypeManager.IsNullableType (source_type) && TypeManager.IsNullableType (target))
1193                                 return new Nullable.LiftedConversion (
1194                                         source, target, true, look_for_explicit, loc).Resolve (ec);
1195
1196                         union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
1197                         if (union == null)
1198                                 return null;
1199
1200                         Type most_specific_source, most_specific_target;
1201
1202                         most_specific_source = FindMostSpecificSource (ec, union, source, look_for_explicit, loc);
1203                         if (most_specific_source == null)
1204                                 return null;
1205
1206                         most_specific_target = FindMostSpecificTarget (ec, union, target, look_for_explicit, loc);
1207                         if (most_specific_target == null)
1208                                 return null;
1209
1210                         int count = 0;
1211
1212
1213                         foreach (MethodBase mb in union.Methods){
1214                                 ParameterData pd = Invocation.GetParameterData (mb);
1215                                 MethodInfo mi = (MethodInfo) mb;
1216
1217                                 if (pd.ParameterType (0) == most_specific_source &&
1218                                     mi.ReturnType == most_specific_target) {
1219                                         method = mb;
1220                                         count++;
1221                                 }
1222                         }
1223
1224                         if (method == null || count > 1)
1225                                 return null;
1226
1227
1228                         //
1229                         // This will do the conversion to the best match that we
1230                         // found.  Now we need to perform an implict standard conversion
1231                         // if the best match was not the type that we were requested
1232                         // by target.
1233                         //
1234                         if (look_for_explicit)
1235                                 source = WideningAndNarrowingConversionStandard (ec, source, most_specific_source, loc);
1236                         else
1237                                 source = WideningConversionStandard (ec, source, most_specific_source, loc);
1238
1239                         if (source == null)
1240                                 return null;
1241
1242                         Expression e;
1243                         e =  new UserCast ((MethodInfo) method, source, loc);
1244                         if (e.Type != target){
1245                                 if (!look_for_explicit)
1246                                         e = WideningConversionStandard (ec, e, target, loc);
1247                                 else
1248                                         e = WideningAndNarrowingConversionStandard (ec, e, target, loc);
1249                         }
1250
1251                         return e;
1252                 }
1253
1254                 /// <summary>
1255                 ///   Converts implicitly the resolved expression `expr' into the
1256                 ///   `target_type'.  It returns a new expression that can be used
1257                 ///   in a context that expects a `target_type'.
1258                 /// </summary>
1259                 static public Expression WideningConversion (EmitContext ec, Expression expr,
1260                                                              Type target_type, Location loc)
1261                 {
1262                         Expression e;
1263
1264                         if (target_type == null)
1265                                 throw new Exception ("Target type is null");
1266
1267                         e = WideningConversionStandard (ec, expr, target_type, loc);
1268                         if (e != null)
1269                                 return e;
1270
1271                         //
1272                         // VB.NET has no notion of User defined conversions
1273                         //
1274
1275 //                      e = ImplicitUserConversion (ec, expr, target_type, loc);
1276 //                      if (e != null)
1277 //                              return e;
1278
1279                         return null;
1280                 }
1281
1282
1283                 /// <summary>
1284                 ///   Attempts to apply the `Standard Implicit
1285                 ///   Conversion' rules to the expression `expr' into
1286                 ///   the `target_type'.  It returns a new expression
1287                 ///   that can be used in a context that expects a
1288                 ///   `target_type'.
1289                 ///
1290                 ///   This is different from `WideningConversion' in that the
1291                 ///   user defined implicit conversions are excluded.
1292                 /// </summary>
1293                 static public Expression WideningConversionStandard (EmitContext ec, Expression expr,
1294                                                                      Type target_type, Location loc)
1295                 {
1296                         Type expr_type = expr.Type;
1297                         Expression e;
1298
1299                         if (expr is NullLiteral) {
1300                                 if (target_type.IsGenericParameter)
1301                                         return TypeParameter_to_Null (expr, target_type, loc);
1302
1303                                 if (TypeManager.IsNullableType (target_type))
1304                                         return new Nullable.NullableLiteral (target_type, loc);
1305                         }
1306
1307                         if (TypeManager.IsNullableType (expr_type) && TypeManager.IsNullableType (target_type))
1308                                 return new Nullable.LiftedConversion (
1309                                         expr, target_type, false, false, loc).Resolve (ec);
1310
1311                         if (expr.eclass == ExprClass.MethodGroup){
1312                                 if (!TypeManager.IsDelegateType (target_type)){
1313                                         return null;
1314                                 }
1315
1316                                 //
1317                                 // Only allow anonymous method conversions on post ISO_1
1318                                 //
1319                                 if (RootContext.Version != LanguageVersion.ISO_1){
1320                                         MethodGroupExpr mg = expr as MethodGroupExpr;
1321                                         if (mg != null)
1322                                                 return ImplicitDelegateCreation.Create (ec, mg, target_type, loc);
1323                                 }
1324                         }
1325
1326                         if (expr_type.Equals (target_type) && !TypeManager.IsNullType (expr_type))
1327                                 return expr;
1328
1329                         e = WideningNumericConversion (ec, expr, target_type, loc);
1330                         if (e != null)
1331                                 return e;
1332
1333                         e = WideningReferenceConversion (ec, expr, target_type);
1334                         if (e != null)
1335                                 return e;
1336
1337                         if ((target_type == TypeManager.enum_type ||
1338                              target_type.IsSubclassOf (TypeManager.enum_type)) &&
1339                             expr is IntLiteral){
1340                                 IntLiteral i = (IntLiteral) expr;
1341
1342                                 if (i.Value == 0)
1343                                         return new EnumConstant ((Constant) expr, target_type);
1344                         }
1345
1346                         if (ec.InUnsafe) {
1347                                 if (expr_type.IsPointer){
1348                                         if (target_type == TypeManager.void_ptr_type)
1349                                                 return new EmptyCast (expr, target_type);
1350
1351                                         //
1352                                         // yep, comparing pointer types cant be done with
1353                                         // t1 == t2, we have to compare their element types.
1354                                         //
1355                                         if (target_type.IsPointer){
1356                                                 if (TypeManager.GetElementType(target_type) == TypeManager.GetElementType(expr_type))
1357                                                         return expr;
1358                                         }
1359                                 }
1360
1361                                 if (target_type.IsPointer) {
1362                                         if (expr_type == TypeManager.null_type)
1363                                                 return new EmptyCast (expr, target_type);
1364
1365                                         if (expr_type == TypeManager.void_ptr_type)
1366                                                 return new EmptyCast (expr, target_type);
1367                                 }
1368                         }
1369
1370                         if (expr_type == TypeManager.anonymous_method_type){
1371                                 if (!TypeManager.IsDelegateType (target_type)){
1372                                         Report.Error (1660, loc,
1373                                                               "Cannot convert anonymous method to `{0}', since it is not a delegate",
1374                                                               TypeManager.CSharpName (target_type));
1375                                         return null;
1376                                 }
1377
1378                                 AnonymousMethod am = (AnonymousMethod) expr;
1379                                 int errors = Report.Errors;
1380
1381                                 Expression conv = am.Compatible (ec, target_type, false);
1382                                 if (conv != null)
1383                                         return conv;
1384
1385                                 //
1386                                 // We return something instead of null, to avoid
1387                                 // the duplicate error, since am.Compatible would have
1388                                 // reported that already
1389                                 //
1390                                 if (errors != Report.Errors)
1391                                         return new EmptyCast (expr, target_type);
1392                         }
1393
1394                         //
1395                         // VB.NET specific conversions
1396                         //
1397
1398                         e = WideningStringConversions (ec, expr, target_type, loc);
1399                         if (e != null)
1400                                 return e;
1401
1402
1403                         return null;
1404                 }
1405
1406                 /// <summary>
1407                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1408                 ///   into a different data type using casts (See Implicit Constant
1409                 ///   Expression Conversions)
1410                 /// </summary>
1411                 static public Expression TryWideningIntConversion (Type target_type, IntConstant ic)
1412                 {
1413                         int value = ic.Value;
1414
1415                         if (value == 0 && ic is IntLiteral && TypeManager.IsEnumType (target_type)){
1416                                 Type underlying = TypeManager.EnumToUnderlying (target_type);
1417                                 Constant e = (Constant) ic;
1418
1419                                 //
1420                                 // Possibly, we need to create a different 0 literal before passing
1421                                 // to EnumConstant
1422                                 //
1423                                 if (underlying == TypeManager.int64_type)
1424                                         e = new LongLiteral (0);
1425                                 else if (underlying == TypeManager.uint64_type)
1426                                         e = new ULongLiteral (0);
1427
1428                                 return new EnumConstant (e, target_type);
1429                         }
1430
1431                         //
1432                         // If `target_type' is an interface and the type of `ic' implements the interface
1433                         // e.g. target_type is IComparable, IConvertible, IFormattable
1434                         //
1435                         if (target_type.IsInterface && target_type.IsAssignableFrom (ic.Type))
1436                                 return new BoxedCast (ic);
1437
1438                         return null;
1439                 }
1440
1441                 /// <summary>
1442                 ///   Attempts to perform an implicit constant conversion of the IntConstant
1443                 ///   into a different data type using casts (See Implicit Constant
1444                 ///   Expression Conversions)
1445                 /// </summary>
1446                 static public Expression WideningConstantConversions (Type target_type, Constant const_expr)
1447                 {
1448                         Constant ret_expr;
1449
1450                         Type const_expr_type = const_expr.Type;
1451                         Location loc = const_expr.Location;
1452
1453                         if (target_type == TypeManager.byte_type){
1454                                 if (const_expr_type == TypeManager.short_type ||
1455                                         const_expr_type == TypeManager.int32_type ||
1456                                         const_expr_type == TypeManager.int64_type)
1457                                                 return const_expr.ToByte (loc);
1458                         }
1459
1460                         if (target_type == TypeManager.short_type){
1461                                 if (const_expr_type == TypeManager.int32_type ||
1462                                         const_expr_type == TypeManager.int64_type)
1463                                                 return const_expr.ToShort (loc);
1464                         }
1465
1466                         if (target_type == TypeManager.int32_type){
1467                                 if (const_expr_type == TypeManager.int64_type)
1468                                         return const_expr.ToInt (loc);
1469                         }
1470
1471                         if (target_type == TypeManager.float_type) {
1472                                 if (const_expr_type == TypeManager.double_type)
1473                                         return const_expr.ToDouble (loc);
1474                         }
1475
1476                         return null;
1477                 }
1478
1479                 static public Constant NothingToPrimitiveConstants (Expression expr, Type target_type)
1480                 {
1481                         NullLiteral null_literal = (NullLiteral) expr;
1482                         Location loc = null_literal.Location;
1483                         Type real_target_type = target_type ;
1484                         Constant retval = null;
1485
1486                         if (null_literal == null)
1487                                 throw new Exception ("FIXME: I was expecting that I would always get only NullLiterals");
1488
1489                         if (target_type.IsSubclassOf(TypeManager.enum_type))
1490                                 real_target_type = TypeManager.EnumToUnderlying (target_type);
1491
1492                         if (real_target_type == TypeManager.bool_type)
1493                                 retval = null_literal.ToBoolean (loc);
1494                         else if (real_target_type == TypeManager.byte_type)
1495                                 retval = null_literal.ToByte (loc);
1496                         else if (real_target_type == TypeManager.short_type)
1497                                 retval = null_literal.ToShort (loc);
1498                         else if (real_target_type == TypeManager.int32_type)
1499                                 retval = null_literal.ToInt (loc);
1500                         else if (real_target_type == TypeManager.int64_type)
1501                                 null_literal.ToLong (loc);
1502                         else if (real_target_type == TypeManager.decimal_type)
1503                                 retval = null_literal.ToDecimal (loc);
1504                         else if (real_target_type == TypeManager.float_type)
1505                                 retval = null_literal.ToLong (loc);
1506                         else if (real_target_type == TypeManager.double_type)
1507                                 retval = null_literal.ToDouble (loc);
1508                         else if (real_target_type == TypeManager.char_type)
1509                                 retval = null_literal.ToChar (loc);
1510                         else if (real_target_type == TypeManager.string_type)
1511                                 retval = new StringConstant (null);
1512
1513                         if (real_target_type != target_type && retval != null)
1514                                 retval = new EnumConstant (retval, target_type);
1515
1516                         return retval;
1517                 }
1518
1519                 static public void Error_CannotWideningConversion (Location loc, Type source, Type target)
1520                 {
1521                         if (source.Name == target.Name){
1522                                 Report.ExtraInformation (loc,
1523                                          String.Format (
1524                                                 "The type {0} has two conflicting definitons, one comes from {0} and the other from {1}",
1525                                                 source.Assembly.FullName, target.Assembly.FullName));
1526
1527                         }
1528                         Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
1529                                       source == TypeManager.anonymous_method_type ?
1530                                       "anonymous method" : "`" + TypeManager.CSharpName (source) + "'",
1531                                       TypeManager.CSharpName (target));
1532                 }
1533
1534                 /// <summary>
1535                 ///   Attempts to implicitly convert `source' into `target_type', using
1536                 ///   WideningConversion.  If there is no implicit conversion, then
1537                 ///   an error is signaled
1538                 /// </summary>
1539                 static public Expression WideningConversionRequired (EmitContext ec, Expression source,
1540                                                                      Type target_type, Location loc)
1541                 {
1542                         Expression e;
1543
1544                         int errors = Report.Errors;
1545                         e = WideningConversion (ec, source, target_type, loc);
1546                         if (Report.Errors > errors)
1547                                 return null;
1548                         if (e != null)
1549                                 return e;
1550
1551                         if (source is DoubleLiteral) {
1552                                 if (target_type == TypeManager.float_type) {
1553                                         Error_664 (loc, "float", "f");
1554                                         return null;
1555                                 }
1556                                 if (target_type == TypeManager.decimal_type) {
1557                                         Error_664 (loc, "decimal", "m");
1558                                         return null;
1559                                 }
1560                         }
1561
1562                         if (source is Constant){
1563                                 Constant c = (Constant) source;
1564
1565                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
1566                                 return null;
1567                         }
1568
1569                         Error_CannotWideningConversion (loc, source.Type, target_type);
1570
1571                         return null;
1572                 }
1573
1574                 static void Error_664 (Location loc, string type, string suffix) {
1575                         Report.Error (664, loc,
1576                                 "Literal of type double cannot be implicitly converted to type '{0}'. Add suffix '{1}' to create a literal of this type",
1577                                 type, suffix);
1578                 }
1579
1580                 /// <summary>
1581                 ///   Performs the explicit numeric conversions
1582                 /// </summary>
1583
1584                 /// <summary>
1585                 ///   Performs the explicit numeric conversions
1586                 /// </summary>
1587                 static Expression NarrowingNumericConversion (EmitContext ec, Expression expr, Type target_type, Location loc)
1588                 {
1589                         Type expr_type = expr.Type;
1590
1591                         //
1592                         // If we have an enumeration, extract the underlying type,
1593                         // use this during the comparison, but wrap around the original
1594                         // target_type
1595                         //
1596                         Type real_target_type = target_type;
1597
1598                         if (TypeManager.IsEnumType (real_target_type))
1599                                 real_target_type = TypeManager.EnumToUnderlying (real_target_type);
1600
1601                         if (WideningStandardConversionExists (ec, expr, real_target_type)){
1602                                 Expression ce = WideningConversionStandard (ec, expr, real_target_type, loc);
1603
1604                                 if (real_target_type != target_type)
1605                                         return new EmptyCast (ce, target_type);
1606                                 return ce;
1607                         }
1608
1609                         if (expr_type == TypeManager.sbyte_type){
1610                                 //
1611                                 // From sbyte to byte, ushort, uint, ulong, char
1612                                 //
1613                                 if (real_target_type == TypeManager.byte_type)
1614                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U1);
1615                                 if (real_target_type == TypeManager.ushort_type)
1616                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U2);
1617                                 if (real_target_type == TypeManager.uint32_type)
1618                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U4);
1619                                 if (real_target_type == TypeManager.uint64_type)
1620                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_U8);
1621                                 if (real_target_type == TypeManager.char_type)
1622                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I1_CH);
1623                         } else if (expr_type == TypeManager.byte_type){
1624                                 //
1625                                 // From byte to sbyte and char
1626                                 //
1627                                 if (real_target_type == TypeManager.sbyte_type)
1628                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U1_I1);
1629                         } else if (expr_type == TypeManager.short_type){
1630                                 //
1631                                 // From short to byte
1632                                 //
1633                                 if (real_target_type == TypeManager.sbyte_type)
1634                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_I1);
1635                                 if (real_target_type == TypeManager.byte_type)
1636                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U1);
1637                                 if (real_target_type == TypeManager.ushort_type)
1638                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U2);
1639                                 if (real_target_type == TypeManager.uint32_type)
1640                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U4);
1641                                 if (real_target_type == TypeManager.uint64_type)
1642                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I2_U8);
1643                         } else if (expr_type == TypeManager.ushort_type){
1644                                 //
1645                                 // From ushort to sbyte, byte, short, char
1646                                 //
1647                                 if (real_target_type == TypeManager.sbyte_type)
1648                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I1);
1649                                 if (real_target_type == TypeManager.byte_type)
1650                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_U1);
1651                                 if (real_target_type == TypeManager.short_type)
1652                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_I2);
1653                                 if (real_target_type == TypeManager.char_type)
1654                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U2_CH);
1655                         } else if (expr_type == TypeManager.int32_type){
1656                                 //
1657                                 // From int to byte, short
1658                                 //
1659                                 if (real_target_type == TypeManager.sbyte_type)
1660                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I1);
1661                                 if (real_target_type == TypeManager.byte_type)
1662                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U1);
1663                                 if (real_target_type == TypeManager.short_type)
1664                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_I2);
1665                                 if (real_target_type == TypeManager.ushort_type)
1666                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U2);
1667                                 if (real_target_type == TypeManager.uint32_type)
1668                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U4);
1669                                 if (real_target_type == TypeManager.uint64_type)
1670                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I4_U8);
1671                         } else if (expr_type == TypeManager.uint32_type){
1672                                 //
1673                                 // From uint to sbyte, byte, short, ushort, int, char
1674                                 //
1675                                 if (real_target_type == TypeManager.sbyte_type)
1676                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I1);
1677                                 if (real_target_type == TypeManager.byte_type)
1678                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U1);
1679                                 if (real_target_type == TypeManager.short_type)
1680                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I2);
1681                                 if (real_target_type == TypeManager.ushort_type)
1682                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_U2);
1683                                 if (real_target_type == TypeManager.int32_type)
1684                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_I4);
1685                                 if (real_target_type == TypeManager.char_type)
1686                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U4_CH);
1687                         } else if (expr_type == TypeManager.int64_type){
1688                                 //
1689                                 // From long to byte, short, int
1690                                 //
1691                                 if (real_target_type == TypeManager.sbyte_type)
1692                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I1);
1693                                 if (real_target_type == TypeManager.byte_type)
1694                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U1);
1695                                 if (real_target_type == TypeManager.short_type)
1696                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I2);
1697                                 if (real_target_type == TypeManager.ushort_type)
1698                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U2);
1699                                 if (real_target_type == TypeManager.int32_type)
1700                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_I4);
1701                                 if (real_target_type == TypeManager.uint32_type)
1702                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U4);
1703                                 if (real_target_type == TypeManager.uint64_type)
1704                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.I8_U8);
1705                         } else if (expr_type == TypeManager.uint64_type){
1706                                 //
1707                                 // From ulong to sbyte, byte, short, ushort, int, uint, long, char
1708                                 //
1709                                 if (real_target_type == TypeManager.sbyte_type)
1710                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I1);
1711                                 if (real_target_type == TypeManager.byte_type)
1712                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U1);
1713                                 if (real_target_type == TypeManager.short_type)
1714                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I2);
1715                                 if (real_target_type == TypeManager.ushort_type)
1716                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U2);
1717                                 if (real_target_type == TypeManager.int32_type)
1718                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I4);
1719                                 if (real_target_type == TypeManager.uint32_type)
1720                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_U4);
1721                                 if (real_target_type == TypeManager.int64_type)
1722                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_I8);
1723                                 if (real_target_type == TypeManager.char_type)
1724                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.U8_CH);
1725                         } else if (expr_type == TypeManager.float_type){
1726                                 //
1727                                 // From float to byte, short, int, long, decimal
1728                                 //
1729                                 if (real_target_type == TypeManager.sbyte_type)
1730                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_I1);
1731                                 if (real_target_type == TypeManager.byte_type)
1732                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1733                                 if (real_target_type == TypeManager.short_type)
1734                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1735                                 if (real_target_type == TypeManager.ushort_type)
1736                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U2);
1737                                 if (real_target_type == TypeManager.int32_type)
1738                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1739                                 if (real_target_type == TypeManager.uint32_type)
1740                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U4);
1741                                 if (real_target_type == TypeManager.int64_type)
1742                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1743                                 if (real_target_type == TypeManager.uint64_type)
1744                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
1745                                 if (real_target_type == TypeManager.decimal_type)
1746                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
1747                         } else if (expr_type == TypeManager.double_type){
1748                                 //
1749                                 // From double to byte, short, int, long, float, decimal
1750                                 //
1751                                 if (real_target_type == TypeManager.sbyte_type)
1752                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I1);
1753                                 if (real_target_type == TypeManager.byte_type)
1754                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_U1);
1755                                 if (real_target_type == TypeManager.short_type)
1756                                         return new FloatingToFixedCast (ec, expr, target_type, ConvCast.Mode.R8_I2);
1757                                 if (real_target_type == TypeManager.ushort_type)
1758                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U2);
1759                                 if (real_target_type == TypeManager.int32_type)
1760                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I4);
1761                                 if (real_target_type == TypeManager.uint32_type)
1762                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U4);
1763                                 if (real_target_type == TypeManager.int64_type)
1764                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_I8);
1765                                 if (real_target_type == TypeManager.uint64_type)
1766                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_U8);
1767
1768                                 if (real_target_type == TypeManager.float_type)
1769                                         return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
1770                                 if (real_target_type == TypeManager.decimal_type)
1771                                         return new ImplicitNew (ec, "System", "Decimal", loc, expr);
1772                         } else if (expr_type == TypeManager.decimal_type){
1773                                 //
1774                                 // From decimal to byte, short, int, long
1775                                 //
1776                                 if (real_target_type == TypeManager.byte_type)
1777                                         return new HelperMethodInvocation (ec, loc, TypeManager.byte_type, TypeManager.convert_to_byte_decimal, expr);
1778                                 if (real_target_type == TypeManager.short_type)
1779                                         return new HelperMethodInvocation (ec, loc, TypeManager.short_type, TypeManager.convert_to_int16_decimal, expr);
1780                                 if (real_target_type == TypeManager.int32_type)
1781                                         return new HelperMethodInvocation (ec, loc, TypeManager.int32_type, TypeManager.convert_to_int32_decimal, expr);
1782                                 if (real_target_type == TypeManager.int64_type)
1783                                         return new HelperMethodInvocation (ec, loc, TypeManager.int64_type, TypeManager.convert_to_int64_decimal, expr);
1784                         }
1785
1786                         return null;
1787                 }
1788
1789                 /// <summary>
1790                 /// VB.NET specific: Convert to and from boolean
1791                 /// </summary>
1792
1793                 static public Expression BooleanConversions (EmitContext ec, Expression expr,
1794                                                                     Type target_type, Location loc)
1795                 {
1796                         Type expr_type = expr.Type;
1797                         Type real_target_type = target_type;
1798
1799                         if (expr_type == TypeManager.bool_type) {
1800
1801                                 //
1802                                 // From boolean to byte, short, int,
1803                                 // long, float, double, decimal
1804                                 //
1805
1806                                 if (real_target_type == TypeManager.byte_type)
1807                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_U1);
1808                                 if (real_target_type == TypeManager.short_type)
1809                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I2);
1810                                 if (real_target_type == TypeManager.int32_type)
1811                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I4);
1812                                 if (real_target_type == TypeManager.int64_type)
1813                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_I8);
1814                                 if (real_target_type == TypeManager.float_type)
1815                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_R4);
1816                                 if (real_target_type == TypeManager.double_type)
1817                                         return new BooleanToNumericCast (expr, target_type, OpCodes.Conv_R8);
1818                                 if (real_target_type == TypeManager.decimal_type) {
1819                                         return new HelperMethodInvocation (ec, expr.Location, TypeManager.decimal_type, TypeManager.msvbcs_decimaltype_from_boolean, expr);
1820                                 }
1821                         } if (real_target_type == TypeManager.bool_type) {
1822
1823                                 //
1824                                 // From byte, short, int, long, float,
1825                                 // double, decimal to boolean
1826                                 //
1827
1828                                 if (expr_type == TypeManager.byte_type ||
1829                                         expr_type == TypeManager.short_type ||
1830                                         expr_type == TypeManager.int32_type ||
1831                                         expr_type == TypeManager.int64_type ||
1832                                         expr_type == TypeManager.float_type ||
1833                                         expr_type == TypeManager.double_type)
1834                                                 return new NumericToBooleanCast (expr, expr_type);
1835                                 if (expr_type == TypeManager.decimal_type) {
1836                                         return new HelperMethodInvocation (ec, expr.Location, TypeManager.bool_type, TypeManager.convert_to_boolean_decimal, expr);
1837                                 }
1838                         }
1839
1840                         return null;
1841                 }
1842
1843                 /// <summary>
1844                 /// VB.NET specific: Widening conversions to string
1845                 /// </summary>
1846
1847                 static public Expression WideningStringConversions (EmitContext ec, Expression expr,
1848                                                                     Type target_type, Location loc)
1849
1850                 {
1851                         Type expr_type = expr.Type;
1852                         Type real_target_type = target_type;
1853
1854                         if (real_target_type == TypeManager.string_type) {
1855                                 //
1856                                 // From char to string
1857                                 //
1858                                 if (expr_type == TypeManager.char_type)
1859                                         return new HelperMethodInvocation (ec, expr.Location, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_char, expr);
1860                         }
1861
1862                         if(expr_type.IsArray && (expr_type.GetElementType() == TypeManager.char_type)) {
1863                                 //
1864                                 // From char array to string
1865                                 //
1866                                 return new ImplicitNew (ec, "System", "String", loc, expr);
1867                         }
1868
1869                         return null;
1870                 }
1871
1872                 /// <summary>
1873                 /// VB.NET specific: Narrowing conversions involving strings
1874                 /// </summary>
1875
1876                 static public Expression NarrowingStringConversions (EmitContext ec, Expression expr,
1877                                                                     Type target_type, Location loc)
1878                 {
1879                         Type expr_type = expr.Type;
1880                         Type real_target_type = target_type;
1881
1882                         // FIXME: Need to take care of Constants
1883
1884                         if (expr_type == TypeManager.string_type) {
1885
1886                                 //
1887                                 // From string to chararray, bool,
1888                                 // byte, short, char, int, long,
1889                                 // float, double, decimal and date
1890                                 //
1891
1892 //                              if (real_target_type.IsArray && (real_target_type.GetElementType() == TypeManager.char_type))
1893 //                                      return new HelperMethodInvocation (ec, loc, TypeManager.char_array_type, TypeManager.msvbcs_char_array_type_from_string, loc, expr);
1894                                 if (real_target_type == TypeManager.bool_type)
1895                                         return new HelperMethodInvocation (ec, loc, TypeManager.bool_type, TypeManager.msvbcs_booleantype_from_string, expr);
1896                                 if (real_target_type == TypeManager.byte_type)
1897                                         return new HelperMethodInvocation (ec, loc, TypeManager.byte_type, TypeManager.msvbcs_bytetype_from_string, expr);
1898                                 if (real_target_type == TypeManager.short_type)
1899                                         return new HelperMethodInvocation (ec, loc, TypeManager.short_type, TypeManager.msvbcs_shorttype_from_string, expr);
1900                                 if (real_target_type == TypeManager.char_type)
1901                                         return new HelperMethodInvocation (ec, loc, TypeManager.char_type, TypeManager.msvbcs_chartype_from_string, expr);
1902                                 if (real_target_type == TypeManager.int32_type)
1903                                         return new HelperMethodInvocation (ec, loc, TypeManager.int32_type, TypeManager.msvbcs_integertype_from_string, expr);
1904                                 if (real_target_type == TypeManager.int64_type)
1905                                         return new HelperMethodInvocation (ec, loc, TypeManager.int64_type, TypeManager.msvbcs_longtype_from_string, expr);
1906                                 if (real_target_type == TypeManager.float_type)
1907                                         return new HelperMethodInvocation (ec, loc, TypeManager.float_type, TypeManager.msvbcs_singletype_from_string, expr);
1908                                 if (real_target_type == TypeManager.double_type)
1909                                         return new HelperMethodInvocation (ec, loc, TypeManager.double_type, TypeManager.msvbcs_doubletype_from_string, expr);
1910                                 if (real_target_type == TypeManager.decimal_type)
1911                                         return new HelperMethodInvocation (ec, loc, TypeManager.decimal_type, TypeManager.msvbcs_decimaltype_from_string, expr);
1912                                 if (real_target_type == TypeManager.date_type)
1913                                         return new HelperMethodInvocation (ec, loc, TypeManager.date_type, TypeManager.msvbcs_datetype_from_string, expr);
1914                         } if (real_target_type == TypeManager.string_type) {
1915
1916                                 //
1917                                 // From bool, byte, short, char, int,
1918                                 // long, float, double, decimal and
1919                                 // date to string
1920                                 //
1921
1922                                 if (expr_type == TypeManager.bool_type)
1923                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_boolean, expr);
1924                                 if (expr_type == TypeManager.byte_type)
1925                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_byte, expr);
1926                                 if (expr_type == TypeManager.short_type)
1927                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_short, expr);
1928                                 if (expr_type == TypeManager.int32_type)
1929                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_integer, expr);
1930                                 if (expr_type == TypeManager.int64_type)
1931                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_long, expr);
1932                                 if (expr_type == TypeManager.float_type)
1933                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_single, expr);
1934                                 if (expr_type == TypeManager.double_type)
1935                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_double, expr);
1936                                 if (expr_type == TypeManager.decimal_type)
1937                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_decimal, expr);
1938                                 if (expr_type == TypeManager.date_type)
1939                                         return new HelperMethodInvocation (ec, loc, TypeManager.string_type, TypeManager.msvbcs_stringtype_from_date, expr);
1940                         }
1941
1942                         return null;
1943                 }
1944
1945
1946                 /// <summary>
1947                 /// VB.NET specific: Conversions from Object to Primitive Types
1948                 /// </summary>
1949
1950                 static public Expression ObjectTypeToPrimitiveTypes (EmitContext ec, Expression expr,
1951                                                                     Type target_type, Location loc)
1952                 {
1953                         Type expr_type = expr.Type;
1954                         Type real_target_type = target_type;
1955                         MethodInfo helper_method = null;
1956                         Expression retexpr;
1957
1958                         if (expr_type != TypeManager.object_type)
1959                                 return null;
1960
1961                         if (target_type.IsSubclassOf (TypeManager.enum_type))
1962                                 real_target_type = TypeManager.EnumToUnderlying (target_type);
1963
1964
1965                         if (real_target_type == TypeManager.bool_type)
1966                                 helper_method = TypeManager.msvbcs_booleantype_fromobject_object;
1967                         if (real_target_type == TypeManager.byte_type)
1968                                 helper_method = TypeManager.msvbcs_bytetype_fromobject_object;
1969                         if (real_target_type == TypeManager.short_type)
1970                                 helper_method = TypeManager.msvbcs_shorttype_fromobject_object;
1971                         if (real_target_type == TypeManager.char_type)
1972                                 helper_method = TypeManager.msvbcs_chartype_fromobject_object;
1973                         if (real_target_type == TypeManager.int32_type)
1974                                 helper_method = TypeManager.msvbcs_integertype_fromobject_object;
1975                         if (real_target_type == TypeManager.int64_type)
1976                                 helper_method = TypeManager.msvbcs_longtype_fromobject_object;
1977                         if (real_target_type == TypeManager.float_type)
1978                                 helper_method = TypeManager.msvbcs_singletype_fromobject_object;
1979                         if (real_target_type == TypeManager.double_type)
1980                                 helper_method = TypeManager.msvbcs_doubletype_fromobject_object;
1981                         if (real_target_type == TypeManager.decimal_type)
1982                                 helper_method = TypeManager.msvbcs_decimaltype_fromobject_object;
1983                         if (real_target_type == TypeManager.date_type)
1984                                 helper_method = TypeManager.msvbcs_datetype_fromobject_object;
1985                         if (real_target_type == TypeManager.string_type)
1986                                 helper_method = TypeManager.msvbcs_stringtype_fromobject_object;
1987
1988                         if (helper_method !=  null) {
1989                                 retexpr = new HelperMethodInvocation (ec, loc, real_target_type, helper_method, expr);
1990                                 if (target_type != real_target_type)
1991                                         retexpr = new EmptyCast (retexpr, target_type);
1992
1993                                 return retexpr;
1994                         }
1995
1996                         return null;
1997                 }
1998
1999
2000                 /// <summary>
2001                 ///  Returns whether an explicit reference conversion can be performed
2002                 ///  from source_type to target_type
2003                 /// </summary>
2004                 public static bool NarrowingReferenceConversionExists (Type source_type, Type target_type)
2005                 {
2006                         bool target_is_type_param = target_type.IsGenericParameter;
2007                         bool target_is_value_type = target_type.IsValueType;
2008
2009                         if (source_type == target_type)
2010                                 return true;
2011
2012                         //
2013                         // From generic parameter to any type
2014                         //
2015                         if (source_type.IsGenericParameter)
2016                                 return true;
2017
2018                         //
2019                         // From object to a generic parameter
2020                         //
2021                         if (source_type == TypeManager.object_type && target_is_type_param)
2022                                 return true;
2023
2024                         //
2025                         // From object to any reference type
2026                         //
2027                         if (source_type == TypeManager.object_type && !target_is_value_type)
2028                                 return true;
2029
2030                         //
2031                         // From any class S to any class-type T, provided S is a base class of T
2032                         //
2033                         if (TypeManager.IsSubclassOf (target_type, source_type))
2034                                 return true;
2035
2036                         //
2037                         // From any interface type S to any interface T provided S is not derived from T
2038                         //
2039                         if (source_type.IsInterface && target_type.IsInterface){
2040                                 if (!TypeManager.IsSubclassOf (target_type, source_type))
2041                                         return true;
2042                         }
2043
2044                         //
2045                         // From any class type S to any interface T, provided S is not sealed
2046                         // and provided S does not implement T.
2047                         //
2048                         if (target_type.IsInterface && !source_type.IsSealed &&
2049                             !TypeManager.ImplementsInterface (source_type, target_type))
2050                                 return true;
2051
2052                         //
2053                         // From any interface-type S to to any class type T, provided T is not
2054                         // sealed, or provided T implements S.
2055                         //
2056                         if (source_type.IsInterface &&
2057                             (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)))
2058                                 return true;
2059
2060
2061                         // From an array type S with an element type Se to an array type T with an
2062                         // element type Te provided all the following are true:
2063                         //     * S and T differe only in element type, in other words, S and T
2064                         //       have the same number of dimensions.
2065                         //     * Both Se and Te are reference types
2066                         //     * An explicit referenc conversions exist from Se to Te
2067                         //
2068                         if (source_type.IsArray && target_type.IsArray) {
2069                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
2070
2071                                         Type source_element_type = TypeManager.GetElementType (source_type);
2072                                         Type target_element_type = TypeManager.GetElementType (target_type);
2073
2074                                         if (source_element_type.IsGenericParameter ||
2075                                             (!source_element_type.IsValueType && !target_element_type.IsValueType))
2076                                                 if (NarrowingReferenceConversionExists (source_element_type,
2077                                                                                        target_element_type))
2078                                                         return true;
2079                                 }
2080                         }
2081
2082
2083                         // From System.Array to any array-type
2084                         if (source_type == TypeManager.array_type &&
2085                             target_type.IsArray){
2086                                 return true;
2087                         }
2088
2089                         //
2090                         // From System delegate to any delegate-type
2091                         //
2092                         if (source_type == TypeManager.delegate_type &&
2093                             TypeManager.IsDelegateType (target_type))
2094                                 return true;
2095
2096                         //
2097                         // From ICloneable to Array or Delegate types
2098                         //
2099                         if (source_type == TypeManager.icloneable_type &&
2100                             (target_type == TypeManager.array_type ||
2101                              target_type == TypeManager.delegate_type))
2102                                 return true;
2103
2104                         return false;
2105                 }
2106
2107                 /// <summary>
2108                 ///   Implements Explicit Reference conversions
2109                 /// </summary>
2110                 static Expression NarrowingReferenceConversion (Expression source, Type target_type)
2111                 {
2112                         Type source_type = source.Type;
2113                         bool target_is_type_param = target_type.IsGenericParameter;
2114                         bool target_is_value_type = target_type.IsValueType;
2115
2116                         //
2117                         // From object to a generic parameter
2118                         //
2119                         if (source_type == TypeManager.object_type && target_is_type_param)
2120                                 return new UnboxCast (source, target_type);
2121
2122                         //
2123                         // From object to any reference type
2124                         //
2125                         if (source_type == TypeManager.object_type && !target_is_value_type)
2126                                 return new ClassCast (source, target_type);
2127
2128                         //
2129                         // Unboxing conversion.
2130                         //
2131                         if (((source_type == TypeManager.enum_type &&
2132                                 !(source is EmptyCast)) ||
2133                                 source_type == TypeManager.value_type) && target_is_value_type)
2134                                 return new UnboxCast (source, target_type);
2135
2136                         //
2137                         // From any class S to any class-type T, provided S is a base class of T
2138                         //
2139                         if (TypeManager.IsSubclassOf (target_type, source_type))
2140                                 return new ClassCast (source, target_type);
2141
2142                         //
2143                         // From any interface type S to any interface T provided S is not derived from T
2144                         //
2145                         if (source_type.IsInterface && target_type.IsInterface){
2146                                 if (TypeManager.ImplementsInterface (source_type, target_type))
2147                                         return null;
2148                                 else
2149                                         return new ClassCast (source, target_type);
2150                         }
2151
2152                         //
2153                         // From any class type S to any interface T, provides S is not sealed
2154                         // and provided S does not implement T.
2155                         //
2156                         if (target_type.IsInterface && !source_type.IsSealed) {
2157                                 if (TypeManager.ImplementsInterface (source_type, target_type))
2158                                         return null;
2159                                 else
2160                                         return new ClassCast (source, target_type);
2161
2162                         }
2163
2164                         //
2165                         // From any interface-type S to to any class type T, provided T is not
2166                         // sealed, or provided T implements S.
2167                         //
2168                         if (source_type.IsInterface) {
2169                                 if (!target_type.IsSealed || TypeManager.ImplementsInterface (target_type, source_type)) {
2170                                         if (target_type.IsClass)
2171                                                 return new ClassCast (source, target_type);
2172                                         else
2173                                                 return new UnboxCast (source, target_type);
2174                                 }
2175
2176                                 return null;
2177                         }
2178
2179                         // From an array type S with an element type Se to an array type T with an
2180                         // element type Te provided all the following are true:
2181                         //     * S and T differe only in element type, in other words, S and T
2182                         //       have the same number of dimensions.
2183                         //     * Both Se and Te are reference types
2184                         //     * An explicit referenc conversions exist from Se to Te
2185                         //
2186                         if (source_type.IsArray && target_type.IsArray) {
2187                                 if (source_type.GetArrayRank () == target_type.GetArrayRank ()) {
2188
2189                                         Type source_element_type = TypeManager.GetElementType (source_type);
2190                                         Type target_element_type = TypeManager.GetElementType (target_type);
2191
2192                                         if (!source_element_type.IsValueType && !target_element_type.IsValueType)
2193                                                 if (NarrowingReferenceConversionExists (source_element_type,
2194                                                                                        target_element_type))
2195                                                         return new ClassCast (source, target_type);
2196                                 }
2197                         }
2198
2199
2200                         // From System.Array to any array-type
2201                         if (source_type == TypeManager.array_type &&
2202                             target_type.IsArray) {
2203                                 return new ClassCast (source, target_type);
2204                         }
2205
2206                         //
2207                         // From System delegate to any delegate-type
2208                         //
2209                         if (source_type == TypeManager.delegate_type &&
2210                             TypeManager.IsDelegateType (target_type))
2211                                 return new ClassCast (source, target_type);
2212
2213                         //
2214                         // From ICloneable to Array or Delegate types
2215                         //
2216                         if (source_type == TypeManager.icloneable_type &&
2217                             (target_type == TypeManager.array_type ||
2218                              target_type == TypeManager.delegate_type))
2219                                 return new ClassCast (source, target_type);
2220
2221                         return null;
2222                 }
2223
2224                 /// <summary>
2225                 ///   Performs an explicit conversion of the expression `expr' whose
2226                 ///   type is expr.Type to `target_type'.
2227                 /// </summary>
2228                 static public Expression WideningAndNarrowingConversion (EmitContext ec, Expression expr,
2229                                                              Type target_type, Location loc)
2230                 {
2231                         Type expr_type = expr.Type;
2232                         Type original_expr_type = expr_type;
2233
2234                         if (expr_type.IsSubclassOf (TypeManager.enum_type)){
2235                                 if (target_type == TypeManager.enum_type ||
2236                                     target_type == TypeManager.object_type) {
2237                                         if (expr is EnumConstant)
2238                                                 expr = ((EnumConstant) expr).Child;
2239                                         // We really need all these casts here .... :-(
2240                                         expr = new BoxedCast (new EmptyCast (expr, expr_type));
2241                                         return new EmptyCast (expr, target_type);
2242                                 } else if ((expr_type == TypeManager.enum_type) && target_type.IsValueType &&
2243                                            target_type.IsSubclassOf (TypeManager.enum_type))
2244                                         return new UnboxCast (expr, target_type);
2245
2246                                 //
2247                                 // Notice that we have kept the expr_type unmodified, which is only
2248                                 // used later on to
2249                                 if (expr is EnumConstant)
2250                                         expr = ((EnumConstant) expr).Child;
2251                                 else
2252                                         expr = new EmptyCast (expr, TypeManager.EnumToUnderlying (expr_type));
2253                                 expr_type = expr.Type;
2254                         }
2255
2256                         int errors = Report.Errors;
2257                         Expression ne = WideningConversionStandard (ec, expr, target_type, loc);
2258                         if (Report.Errors > errors)
2259                                 return null;
2260
2261                         if (ne != null)
2262                                 return ne;
2263
2264                         if (TypeManager.IsNullableType (expr.Type) && TypeManager.IsNullableType (target_type))
2265                                 return new Nullable.LiftedConversion (
2266                                         expr, target_type, false, true, loc).Resolve (ec);
2267
2268                         ne = NarrowingNumericConversion (ec, expr, target_type, loc);
2269                         if (ne != null)
2270                                 return ne;
2271
2272                         //
2273                         // Unboxing conversion.
2274                         //
2275
2276                         //
2277                         // VB.NET treats conversions from object to
2278                         // the primitive types using the helper
2279                         // routines in Microsoft.VisualBasic.dll
2280                         //
2281
2282                         ne = ObjectTypeToPrimitiveTypes(ec, expr, target_type, loc);
2283                         if (ne != null)
2284                                 return ne;
2285
2286                         if (expr_type == TypeManager.object_type && target_type.IsValueType)
2287                                 return new UnboxCast (expr, target_type);
2288
2289                         //
2290                         // Skip the NarrowingReferenceConversion because we can not convert
2291                         // from Null to a ValueType, and ExplicitReference wont check against
2292                         // null literal explicitly
2293                         //
2294                         if (expr_type != TypeManager.null_type){
2295                                 ne = NarrowingReferenceConversion (expr, target_type);
2296                                 if (ne != null)
2297                                         return ne;
2298                         }
2299
2300                 skip_explicit:
2301                         if (ec.InUnsafe){
2302                                 if (target_type.IsPointer){
2303                                         if (expr_type.IsPointer)
2304                                                 return new EmptyCast (expr, target_type);
2305
2306                                         if (expr_type == TypeManager.sbyte_type ||
2307                                             expr_type == TypeManager.byte_type ||
2308                                             expr_type == TypeManager.short_type ||
2309                                             expr_type == TypeManager.ushort_type ||
2310                                             expr_type == TypeManager.int32_type ||
2311                                             expr_type == TypeManager.uint32_type ||
2312                                             expr_type == TypeManager.uint64_type ||
2313                                             expr_type == TypeManager.int64_type)
2314                                                 return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
2315                                 }
2316                                 if (expr_type.IsPointer){
2317                                         Expression e = null;
2318
2319                                         if (target_type == TypeManager.sbyte_type)
2320                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I1);
2321                                         else if (target_type == TypeManager.byte_type)
2322                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U1);
2323                                         else if (target_type == TypeManager.short_type)
2324                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
2325                                         else if (target_type == TypeManager.ushort_type)
2326                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U2);
2327                                         else if (target_type == TypeManager.int32_type)
2328                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
2329                                         else if (target_type == TypeManager.uint32_type)
2330                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U4);
2331                                         else if (target_type == TypeManager.uint64_type)
2332                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
2333                                         else if (target_type == TypeManager.int64_type){
2334                                                 e = new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
2335                                         }
2336
2337                                         if (e != null){
2338                                                 Expression ci, ce;
2339
2340                                                 ci = WideningConversionStandard (ec, e, target_type, loc);
2341
2342                                                 if (ci != null)
2343                                                         return ci;
2344
2345                                                 ce = NarrowingNumericConversion (ec, e, target_type, loc);
2346                                                 if (ce != null)
2347                                                         return ce;
2348                                                 //
2349                                                 // We should always be able to go from an uint32
2350                                                 // implicitly or explicitly to the other integral
2351                                                 // types
2352                                                 //
2353                                                 throw new Exception ("Internal compiler error");
2354                                         }
2355                                 }
2356                         }
2357
2358                         //
2359                         // VB.NET specific conversions
2360                         //
2361
2362                         ne = BooleanConversions (ec, expr, target_type, loc);
2363                         if (ne != null)
2364                                 return ne;
2365
2366                         ne = NarrowingStringConversions (ec, expr, target_type, loc);
2367                         if (ne != null)
2368                                 return ne;
2369
2370
2371                         //
2372                         // VB.NET has no notion of User defined conversions
2373                         //
2374
2375 //                      ne = ExplicitUserConversion (ec, expr, target_type, loc);
2376 //                      if (ne != null)
2377 //                              return ne;
2378
2379                         if (expr is NullLiteral){
2380                                 Report.Error (37, loc, "Cannot convert null to value type `" +
2381                                               TypeManager.CSharpName (target_type) + "'");
2382                                 return null;
2383                         }
2384
2385                         Error_CannotConvertType (loc, original_expr_type, target_type);
2386                         return null;
2387                 }
2388
2389                 /// <summary>
2390                 ///   Same as WideningAndNarrowingConversion, only it doesn't include user defined conversions
2391                 /// </summary>
2392                 static public Expression WideningAndNarrowingConversionStandard (EmitContext ec, Expression expr,
2393                                                                      Type target_type, Location l)
2394                 {
2395                         int errors = Report.Errors;
2396                         Expression ne = WideningConversionStandard (ec, expr, target_type, l);
2397                         if (Report.Errors > errors)
2398                                 return null;
2399
2400                         if (ne != null)
2401                                 return ne;
2402
2403                         if (TypeManager.IsNullableType (expr.Type) && TypeManager.IsNullableType (target_type))
2404                                 return new Nullable.LiftedConversion (
2405                                         expr, target_type, false, true, l).Resolve (ec);
2406
2407                         ne = NarrowingNumericConversion (ec, expr, target_type, l);
2408                         if (ne != null)
2409                                 return ne;
2410
2411                         ne = NarrowingReferenceConversion (expr, target_type);
2412                         if (ne != null)
2413                                 return ne;
2414
2415                         Error_CannotConvertType (l, expr.Type, target_type);
2416                         return null;
2417                 }
2418
2419                 /// <summary>
2420                 ///   Entry point for VB.NET specific implicit conversions
2421                 /// </summary>
2422                 static public Expression ImplicitVBConversion (EmitContext ec, Expression expr,
2423                                                              Type target_type, Location loc)
2424                 {
2425                         if (RootContext.StricterTypeChecking)
2426                                 return WideningConversion (ec, expr, target_type, loc);
2427                         else
2428                                 return WideningAndNarrowingConversion(ec, expr, target_type, loc);
2429                 }
2430
2431                 /// <summary>
2432                 ///   Mandates VB.NET specific implicit conversions
2433                 /// </summary>
2434                 static public Expression ImplicitVBConversionRequired (EmitContext ec, Expression source,
2435                                                                      Type target_type, Location loc)
2436                 {
2437                         Expression e;
2438
2439
2440                         int errors = Report.Errors;
2441                         e = ImplicitVBConversion (ec, source, target_type, loc);
2442                         if (Report.Errors > errors)
2443                                 return null;
2444                         if (e != null)
2445                                 return e;
2446
2447                         if (source is DoubleLiteral) {
2448                                 if (target_type == TypeManager.float_type) {
2449                                         Error_664 (loc, "float", "f");
2450                                         return null;
2451                                 }
2452                                 if (target_type == TypeManager.decimal_type) {
2453                                         Error_664 (loc, "decimal", "m");
2454                                         return null;
2455                                 }
2456                         }
2457
2458                         if (source is Constant){
2459                                 Constant c = (Constant) source;
2460
2461                                 Expression.Error_ConstantValueCannotBeConverted (loc, c.AsString (), target_type);
2462                                 return null;
2463                         }
2464
2465                         Error_CannotWideningConversion (loc, source.Type, target_type);
2466
2467                         return null;
2468                 }
2469
2470                 /// <summary>
2471                 ///   Entry point for VB.NET specific explicit conversions
2472                 /// </summary>
2473                 static public Expression ExplicitVBConversion (EmitContext ec, Expression expr,
2474                                                              Type target_type, Location loc)
2475                 {
2476                                 return WideningAndNarrowingConversion(ec, expr, target_type, loc);
2477                 }
2478
2479         }
2480 }