mcs/class/corlib/System.Reflection/Binder.cs

   1 // System.Reflection.Binder
   2 //
   3 // Authors:
   4 //      Sean MacIsaac (macisaac@ximian.com)
   5 //      Paolo Molaro (lupus@ximian.com)
   6 //      Gonzalo Paniagua Javier (gonzalo@ximian.com)
   7 //
   8 // (C) Ximian, Inc. 2001 - 2003
   9 // (c) Copyright 2004 Novell, Inc. (http://www.novell.com)
  10
  11 //
  12 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  13 //
  14 // Permission is hereby granted, free of charge, to any person obtaining
  15 // a copy of this software and associated documentation files (the
  16 // "Software"), to deal in the Software without restriction, including
  17 // without limitation the rights to use, copy, modify, merge, publish,
  18 // distribute, sublicense, and/or sell copies of the Software, and to
  19 // permit persons to whom the Software is furnished to do so, subject to
  20 // the following conditions:
  21 //
  22 // The above copyright notice and this permission notice shall be
  23 // included in all copies or substantial portions of the Software.
  24 //
  25 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  26 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  27 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  28 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  29 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  30 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  31 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  32 //
  33
  34 using System.Globalization;
  35 using System.Runtime.InteropServices;
  36
  37 namespace System.Reflection
  38 {
  39 #if NET_2_0
  40         [ComVisible (true)]
  41 #endif
  42         [Serializable]
  43         [ClassInterface(ClassInterfaceType.AutoDual)]
  44         public abstract class Binder
  45         {
  46                 protected Binder () {}
  47
  48                 public abstract FieldInfo BindToField (BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture);
  49                 public abstract MethodBase BindToMethod (BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state);
  50                 public abstract object ChangeType (object value, Type type, CultureInfo culture);
  51                 public abstract void ReorderArgumentArray( ref object[] args, object state);
  52                 public abstract MethodBase SelectMethod (BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers);
  53                 public abstract PropertyInfo SelectProperty( BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers);
  54
  55                 static Binder default_binder = new Default ();
  56
  57                 internal static Binder DefaultBinder {
  58                         get {
  59                                 return default_binder;
  60                         }
  61                 }
  62
  63                 internal static bool ConvertArgs (Binder binder, object[] args, ParameterInfo[] pinfo, CultureInfo culture) {
  64                         if (args == null) {
  65                                 if ( pinfo.Length == 0)
  66                                         return true;
  67                                 else
  68                                         throw new TargetParameterCountException ();
  69                         }
  70                         if (pinfo.Length != args.Length)
  71                                 throw new TargetParameterCountException ();
  72                         for (int i = 0; i < args.Length; ++i) {
  73                                 object v = binder.ChangeType (args [i], pinfo[i].ParameterType, culture);
  74                                 if ((v == null) && (args [i] != null))
  75                                         return false;
  76                                 args [i] = v;
  77                         }
  78                         return true;
  79                 }
  80
  81                 internal static int GetDerivedLevel (Type type)
  82                 {
  83                         Type searchType = type;
  84                         int level = 1;
  85
  86                         while (searchType.BaseType != null)
  87                         {
  88                                 level++;
  89                                 searchType = searchType.BaseType;
  90                         }
  91
  92                         return level;
  93                 }
  94
  95                 internal static MethodBase FindMostDerivedMatch (MethodBase [] match)
  96                 {
  97                         int highLevel = 0;
  98                         int matchId = -1;
  99                         int count = match.Length;
 100
 101                         for (int current = 0; current < count; current++)
 102                         {
 103                                 MethodBase m = match [current];
 104                                 int level = GetDerivedLevel (m.DeclaringType);
 105                                 if (level == highLevel)
 106                                         throw new AmbiguousMatchException ();
 107                                 // If the argument types differ we
 108                                 // have an ambigous match, as well
 109                                 if (matchId >= 0) {
 110                                         ParameterInfo[] p1 = m.GetParameters ();
 111                                         ParameterInfo[] p2 = match [matchId].GetParameters ();
 112                                         bool equal = true;
 113
 114                                         if (p1.Length != p2.Length)
 115                                                 equal = false;
 116                                         else {
 117                                                 int i;
 118
 119                                                 for (i = 0; i < p1.Length; ++i) {
 120                                                         if (p1 [i].ParameterType != p2 [i].ParameterType) {
 121                                                                 equal = false;
 122                                                                 break;
 123                                                         }
 124                                                 }
 125                                         }
 126
 127                                         if (!equal)
 128                                                 throw new AmbiguousMatchException ();
 129                                 }
 130
 131                                 if (level > highLevel)
 132                                 {
 133                                         highLevel = level;
 134                                         matchId = current;
 135                                 }
 136                         }
 137
 138                         return match[matchId];
 139                 }
 140
 141                 internal sealed class Default : Binder {
 142                         public override FieldInfo BindToField (BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture)
 143                         {
 144                                 if (match == null)
 145                                         throw new ArgumentNullException ("match");
 146                                 foreach (FieldInfo f in match) {
 147                                         if (check_type (value.GetType (), f.FieldType))
 148                                                 return f;
 149                                 }
 150                                 return null;
 151                         }
 152
 153                         //
 154                         // FIXME: There was a MonoTODO, but it does not explain what the problem is
 155                         //
 156                         public override MethodBase BindToMethod (BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state)
 157                         {
 158                                 Type[] types;
 159                                 if (args == null)
 160                                         types = Type.EmptyTypes;
 161                                 else {
 162                                         types = new Type [args.Length];
 163                                         for (int i = 0; i < args.Length; ++i) {
 164                                                 if (args [i] != null)
 165                                                         types [i] = args [i].GetType ();
 166                                         }
 167                                 }
 168                                 MethodBase selected = SelectMethod (bindingAttr, match, types, modifiers);
 169                                 state = null;
 170                                 if (names != null)
 171                                         ReorderParameters (names, ref args, selected);
 172                                 return selected;
 173                         }
 174
 175                         void ReorderParameters (string [] names, ref object [] args, MethodBase selected)
 176                         {
 177                                 object [] newArgs = new object [args.Length];
 178                                 Array.Copy (args, newArgs, args.Length);
 179                                 ParameterInfo [] plist = selected.GetParameters ();
 180                                 for (int n = 0; n < names.Length; n++)
 181                                         for (int p = 0; p < plist.Length; p++) {
 182                                                 if (names [n] == plist [p].Name) {
 183                                                         newArgs [p] = args [n];
 184                                                         break;
 185                                                 }
 186                                         }
 187                                 Array.Copy (newArgs, args, args.Length);
 188                         }
 189
 190                         static bool IsArrayAssignable (Type object_type, Type target_type)
 191                         {
 192                                 if (object_type.IsArray && target_type.IsArray)
 193                                         return IsArrayAssignable (object_type.GetElementType (), target_type.GetElementType ());
 194
 195                                 if (target_type.IsAssignableFrom (object_type))
 196                                         return true;
 197
 198                                 return false;
 199                         }
 200
 201                         public override object ChangeType (object value, Type type, CultureInfo culture)
 202                         {
 203                                 if (value == null)
 204                                         return null;
 205                                 Type vtype = value.GetType ();
 206                                 if (type.IsByRef)
 207                                         type = type.GetElementType ();
 208                                 if (vtype == type || type.IsInstanceOfType (value))
 209                                         return value;
 210                                 if (vtype.IsArray && type.IsArray){
 211                                         if (IsArrayAssignable (vtype.GetElementType (), type.GetElementType ()))
 212                                                 return value;
 213                                 }
 214
 215                                 if (check_type (vtype, type))
 216                                         return Convert.ChangeType (value, type);
 217                                 return null;
 218                         }
 219
 220                         [MonoTODO ("This method does not do anything in Mono")]
 221                         public override void ReorderArgumentArray (ref object[] args, object state)
 222                         {
 223                                 //do nothing until we support named arguments
 224                                 //throw new NotImplementedException ();
 225                         }
 226
 227                         private static bool check_type (Type from, Type to) {
 228                                 if (from == to)
 229                                         return true;
 230
 231                                 if (from == null)
 232                                         return true;
 233
 234                                 TypeCode fromt = Type.GetTypeCode (from);
 235                                 TypeCode tot = Type.GetTypeCode (to);
 236
 237                                 if (to.IsByRef != from.IsByRef)
 238                                         return false;
 239
 240                                 if (to.IsInterface)
 241                                         return to.IsAssignableFrom (from);
 242
 243                                 switch (fromt) {
 244                                 case TypeCode.Char:
 245                                         switch (tot) {
 246                                         case TypeCode.UInt16:
 247                                         case TypeCode.UInt32:
 248                                         case TypeCode.Int32:
 249                                         case TypeCode.UInt64:
 250                                         case TypeCode.Int64:
 251                                         case TypeCode.Single:
 252                                         case TypeCode.Double:
 253                                                 return true;
 254                                         }
 255                                         return to == typeof (object);
 256                                 case TypeCode.Byte:
 257                                         switch (tot) {
 258                                         case TypeCode.Char:
 259                                         case TypeCode.UInt16:
 260                                         case TypeCode.Int16:
 261                                         case TypeCode.UInt32:
 262                                         case TypeCode.Int32:
 263                                         case TypeCode.UInt64:
 264                                         case TypeCode.Int64:
 265                                         case TypeCode.Single:
 266                                         case TypeCode.Double:
 267                                                 return true;
 268                                         }
 269                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 270                                 case TypeCode.SByte:
 271                                         switch (tot) {
 272                                         case TypeCode.Int16:
 273                                         case TypeCode.Int32:
 274                                         case TypeCode.Int64:
 275                                         case TypeCode.Single:
 276                                         case TypeCode.Double:
 277                                                 return true;
 278                                         }
 279                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 280                                 case TypeCode.UInt16:
 281                                         switch (tot) {
 282                                         case TypeCode.UInt32:
 283                                         case TypeCode.Int32:
 284                                         case TypeCode.UInt64:
 285                                         case TypeCode.Int64:
 286                                         case TypeCode.Single:
 287                                         case TypeCode.Double:
 288                                                 return true;
 289                                         }
 290                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 291                                 case TypeCode.Int16:
 292                                         switch (tot) {
 293                                         case TypeCode.Int32:
 294                                         case TypeCode.Int64:
 295                                         case TypeCode.Single:
 296                                         case TypeCode.Double:
 297                                                 return true;
 298                                         }
 299                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 300                                 case TypeCode.UInt32:
 301                                         switch (tot) {
 302                                         case TypeCode.UInt64:
 303                                         case TypeCode.Int64:
 304                                         case TypeCode.Single:
 305                                         case TypeCode.Double:
 306                                                 return true;
 307                                         }
 308                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 309                                 case TypeCode.Int32:
 310                                         switch (tot) {
 311                                         case TypeCode.Int64:
 312                                         case TypeCode.Single:
 313                                         case TypeCode.Double:
 314                                                 return true;
 315                                         }
 316                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 317                                 case TypeCode.UInt64:
 318                                 case TypeCode.Int64:
 319                                         switch (tot) {
 320                                         case TypeCode.Single:
 321                                         case TypeCode.Double:
 322                                                 return true;
 323                                         }
 324                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 325                                 case TypeCode.Single:
 326                                         return tot == TypeCode.Double || to == typeof (object);
 327                                 default:
 328                                         /* TODO: handle valuetype -> byref */
 329                                         if (to == typeof (object) && from.IsValueType)
 330                                                 return true;
 331
 332                                         return to.IsAssignableFrom (from);
 333                                 }
 334                         }
 335
 336                         private static bool check_arguments (Type[] types, ParameterInfo[] args) {
 337                                 for (int i = 0; i < types.Length; ++i) {
 338                                         if (!check_type (types [i], args [i].ParameterType))
 339                                                 return false;
 340                                 }
 341                                 return true;
 342                         }
 343
 344                         public override MethodBase SelectMethod (BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers)
 345                         {
 346                                 MethodBase m;
 347                                 int i, j;
 348
 349                                 if (match == null)
 350                                         throw new ArgumentNullException ("match");
 351
 352                                 /* first look for an exact match... */
 353                                 for (i = 0; i < match.Length; ++i) {
 354                                         m = match [i];
 355                                         ParameterInfo[] args = m.GetParameters ();
 356                                         if (args.Length != types.Length)
 357                                                 continue;
 358                                         for (j = 0; j < types.Length; ++j) {
 359                                                 if (types [j] != args [j].ParameterType)
 360                                                         break;
 361                                         }
 362                                         if (j == types.Length)
 363                                                 return m;
 364                                 }
 365
 366                                 /* Try methods with ParamArray attribute */
 367                                 bool isdefParamArray = false;
 368                                 Type elementType = null;
 369                                 for (i = 0; i < match.Length; ++i) {
 370                                         m = match [i];
 371                                         ParameterInfo[] args = m.GetParameters ();
 372                                         if (args.Length > types.Length)
 373                                                 continue;
 374                                         else if (args.Length == 0)
 375                                                 continue;
 376                                         isdefParamArray = Attribute.IsDefined (args [args.Length - 1], typeof (ParamArrayAttribute));
 377                                         if (!isdefParamArray)
 378                                                 continue;
 379                                         elementType = args [args.Length - 1].ParameterType.GetElementType ();
 380                                         for (j = 0; j < types.Length; ++j) {
 381                                                 if (j < (args.Length - 1) && types [j] != args [j].ParameterType)
 382                                                         break;
 383                                                 else if (j >= (args.Length - 1) && types [j] != elementType)
 384                                                         break;
 385                                         }
 386                                         if (j == types.Length)
 387                                                 return m;
 388                                 }
 389
 390                                 if ((int)(bindingAttr & BindingFlags.ExactBinding) != 0)
 391                                         return null;
 392
 393                                 MethodBase result = null;
 394                                 for (i = 0; i < match.Length; ++i) {
 395                                         m = match [i];
 396                                         ParameterInfo[] args = m.GetParameters ();
 397                                         if (args.Length != types.Length)
 398                                                 continue;
 399                                         if (!check_arguments (types, args))
 400                                                 continue;
 401
 402                                         if (result != null)
 403                                                 result = GetBetterMethod (result, m, types);
 404                                         else
 405                                                 result = m;
 406                                 }
 407
 408                                 return result;
 409                         }
 410
 411                         MethodBase GetBetterMethod (MethodBase m1, MethodBase m2, Type [] types)
 412                         {
 413 #if NET_2_0
 414                                 if (m1.IsGenericMethodDefinition &&
 415                                     !m2.IsGenericMethodDefinition)
 416                                         return m2;
 417                                 if (m2.IsGenericMethodDefinition &&
 418                                     !m1.IsGenericMethodDefinition)
 419                                         return m1;
 420 #endif
 421
 422                                 ParameterInfo [] pl1 = m1.GetParameters ();
 423                                 ParameterInfo [] pl2 = m2.GetParameters ();
 424                                 int prev = 0;
 425                                 for (int i = 0; i < pl1.Length; i++) {
 426                                         int cmp = CompareCloserType (pl1 [i].ParameterType, pl2 [i].ParameterType);
 427                                         if (cmp != 0 && prev != 0 && prev != cmp)
 428                                                 throw new AmbiguousMatchException ();
 429                                         if (cmp != 0)
 430                                                 prev = cmp;
 431                                 }
 432                                 if (prev != 0)
 433                                         return prev > 0 ? m2 : m1;
 434
 435                                 Type dt1 = m1.DeclaringType;
 436                                 Type dt2 = m2.DeclaringType;
 437                                 if (dt1 != dt2) {
 438                                         if (dt1.IsSubclassOf(dt2))
 439                                                 return m1;
 440                                         if (dt2.IsSubclassOf(dt1))
 441                                                 return m2;
 442                                 }
 443
 444                                 bool va1 = (m1.CallingConvention & CallingConventions.VarArgs) != 0;
 445                                 bool va2 = (m2.CallingConvention & CallingConventions.VarArgs) != 0;
 446                                 if (va1 && !va2)
 447                                         return m2;
 448                                 if (va2 && !va1)
 449                                         return m1;
 450
 451                                 throw new AmbiguousMatchException ();
 452                         }
 453
 454                         int CompareCloserType (Type t1, Type t2)
 455                         {
 456                                 if (t1 == t2)
 457                                         return 0;
 458 #if NET_2_0
 459                                 if (t1.IsGenericParameter && !t2.IsGenericParameter)
 460                                         return 1; // t2
 461                                 if (!t1.IsGenericParameter && t2.IsGenericParameter)
 462                                         return -1; // t1
 463 #endif
 464                                 if (t1.HasElementType && t2.HasElementType)
 465                                         return CompareCloserType (
 466                                                 t1.GetElementType (),
 467                                                 t2.GetElementType ());
 468
 469                                 if (t1.IsSubclassOf (t2))
 470                                         return -1; // t1
 471                                 if (t2.IsSubclassOf (t1))
 472                                         return 1; // t2
 473
 474                                 if (t1.IsInterface && Array.IndexOf (t2.GetInterfaces (), t1) >= 0)
 475                                         return 1; // t2
 476                                 if (t2.IsInterface && Array.IndexOf (t1.GetInterfaces (), t2) >= 0)
 477                                         return -1; // t1
 478
 479                                 // What kind of cases could reach here?
 480                                 return 0;
 481                         }
 482
 483                         public override PropertyInfo SelectProperty (BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers)
 484                         {
 485                                 if (match == null || match.Length == 0)
 486                                         throw new ArgumentException ("No properties provided", "match");
 487
 488                                 bool haveRet = (returnType != null);
 489                                 int idxlen = (indexes != null) ? indexes.Length : -1;
 490                                 PropertyInfo result = null;
 491                                 int i;
 492                                 int best_score = Int32.MaxValue - 1;
 493                                 int fail_score = Int32.MaxValue;
 494                                 int level = 0;
 495
 496                                 for (i = match.Length - 1; i >= 0; i--) {
 497                                         PropertyInfo p = match [i];
 498                                         ParameterInfo[] args = p.GetIndexParameters ();
 499                                         if (idxlen >= 0 && idxlen != args.Length)
 500                                                 continue;
 501
 502                                         if (haveRet && !check_type (p.PropertyType, returnType))
 503                                                 continue;
 504
 505                                         int score = Int32.MaxValue - 1;
 506                                         if (idxlen > 0) {
 507                                                 score = check_arguments_with_score (indexes, args);
 508                                                 if (score == -1)
 509                                                         continue;
 510                                         }
 511
 512                                         int new_level = GetDerivedLevel (p.DeclaringType);
 513                                         if (result != null) {
 514                                                 if (best_score < score)
 515                                                         continue;
 516
 517                                                 if (best_score == score) {
 518                                                         if (level == new_level) {
 519                                                                 // Keep searching. May be there's something
 520                                                                 // better for us.
 521                                                                 fail_score = score;
 522                                                                 continue;
 523                                                         }
 524
 525                                                         if (level > new_level)
 526                                                                 continue;
 527                                                 }
 528                                         }
 529
 530                                         result = p;
 531                                         best_score = score;
 532                                         level = new_level;
 533                                 }
 534
 535                                 if (fail_score <= best_score)
 536                                         throw new AmbiguousMatchException ();
 537
 538                                 return result;
 539                         }
 540
 541                         static int check_arguments_with_score (Type [] types, ParameterInfo [] args)
 542                         {
 543                                 int worst = -1;
 544
 545                                 for (int i = 0; i < types.Length; ++i) {
 546                                         int res = check_type_with_score (types [i], args [i].ParameterType);
 547                                         if (res == -1)
 548                                                 return -1;
 549
 550                                         if (worst < res)
 551                                                 worst = res;
 552                                 }
 553
 554                                 return worst;
 555                         }
 556
 557                         // 0 -> same type or null and !valuetype
 558                         // 1 -> to == Enum
 559                         // 2 -> value type that don't lose data
 560                         // 3 -> to == IsAssignableFrom
 561                         // 4 -> to == object
 562                         static int check_type_with_score (Type from, Type to)
 563                         {
 564                                 if (from == null)
 565                                         return to.IsValueType ? -1 : 0;
 566
 567                                 if (from == to)
 568                                         return 0;
 569
 570                                 if (to == typeof (object))
 571                                         return 4;
 572
 573                                 TypeCode fromt = Type.GetTypeCode (from);
 574                                 TypeCode tot = Type.GetTypeCode (to);
 575
 576                                 switch (fromt) {
 577                                 case TypeCode.Char:
 578                                         switch (tot) {
 579                                         case TypeCode.UInt16:
 580                                                 return 0;
 581
 582                                         case TypeCode.UInt32:
 583                                         case TypeCode.Int32:
 584                                         case TypeCode.UInt64:
 585                                         case TypeCode.Int64:
 586                                         case TypeCode.Single:
 587                                         case TypeCode.Double:
 588                                                 return 2;
 589                                         }
 590                                         return -1;
 591                                 case TypeCode.Byte:
 592                                         switch (tot) {
 593                                         case TypeCode.Char:
 594                                         case TypeCode.UInt16:
 595                                         case TypeCode.Int16:
 596                                         case TypeCode.UInt32:
 597                                         case TypeCode.Int32:
 598                                         case TypeCode.UInt64:
 599                                         case TypeCode.Int64:
 600                                         case TypeCode.Single:
 601                                         case TypeCode.Double:
 602                                                 return 2;
 603                                         }
 604                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 605                                 case TypeCode.SByte:
 606                                         switch (tot) {
 607                                         case TypeCode.Int16:
 608                                         case TypeCode.Int32:
 609                                         case TypeCode.Int64:
 610                                         case TypeCode.Single:
 611                                         case TypeCode.Double:
 612                                                 return 2;
 613                                         }
 614                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 615                                 case TypeCode.UInt16:
 616                                         switch (tot) {
 617                                         case TypeCode.UInt32:
 618                                         case TypeCode.Int32:
 619                                         case TypeCode.UInt64:
 620                                         case TypeCode.Int64:
 621                                         case TypeCode.Single:
 622                                         case TypeCode.Double:
 623                                                 return 2;
 624                                         }
 625                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 626                                 case TypeCode.Int16:
 627                                         switch (tot) {
 628                                         case TypeCode.Int32:
 629                                         case TypeCode.Int64:
 630                                         case TypeCode.Single:
 631                                         case TypeCode.Double:
 632                                                 return 2;
 633                                         }
 634                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 635                                 case TypeCode.UInt32:
 636                                         switch (tot) {
 637                                         case TypeCode.UInt64:
 638                                         case TypeCode.Int64:
 639                                         case TypeCode.Single:
 640                                         case TypeCode.Double:
 641                                                 return 2;
 642                                         }
 643                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 644                                 case TypeCode.Int32:
 645                                         switch (tot) {
 646                                         case TypeCode.Int64:
 647                                         case TypeCode.Single:
 648                                         case TypeCode.Double:
 649                                                 return 2;
 650                                         }
 651                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 652                                 case TypeCode.UInt64:
 653                                 case TypeCode.Int64:
 654                                         switch (tot) {
 655                                         case TypeCode.Single:
 656                                         case TypeCode.Double:
 657                                                 return 2;
 658                                         }
 659                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 660                                 case TypeCode.Single:
 661                                         return tot == TypeCode.Double ? 2 : -1;
 662                                 default:
 663                                         return (to.IsAssignableFrom (from)) ? 3 : -1;
 664                                 }
 665                         }
 666                 }
 667         }
 668 }
 669