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