mcs/mcs/convert.cs

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