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         [ComVisible (true)]
  40         [Serializable]
  41         [ClassInterface(ClassInterfaceType.AutoDual)]
  42         public abstract class Binder
  43         {
  44                 protected Binder () {}
  45
  46                 public abstract FieldInfo BindToField (BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture);
  47                 public abstract MethodBase BindToMethod (BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state);
  48                 public abstract object ChangeType (object value, Type type, CultureInfo culture);
  49                 public abstract void ReorderArgumentArray( ref object[] args, object state);
  50                 public abstract MethodBase SelectMethod (BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers);
  51                 public abstract PropertyInfo SelectProperty( BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers);
  52
  53                 static Binder default_binder = new Default ();
  54
  55                 internal static Binder DefaultBinder {
  56                         get {
  57                                 return default_binder;
  58                         }
  59                 }
  60
  61                 internal static bool ConvertArgs (Binder binder, object[] args, ParameterInfo[] pinfo, CultureInfo culture) {
  62                         if (args == null) {
  63                                 if ( pinfo.Length == 0)
  64                                         return true;
  65                                 else
  66                                         throw new TargetParameterCountException ();
  67                         }
  68                         if (pinfo.Length != args.Length)
  69                                 throw new TargetParameterCountException ();
  70                         for (int i = 0; i < args.Length; ++i) {
  71                                 object v = binder.ChangeType (args [i], pinfo[i].ParameterType, culture);
  72                                 if ((v == null) && (args [i] != null))
  73                                         return false;
  74                                 args [i] = v;
  75                         }
  76                         return true;
  77                 }
  78
  79                 internal static int GetDerivedLevel (Type type)
  80                 {
  81                         Type searchType = type;
  82                         int level = 1;
  83
  84                         while (searchType.BaseType != null)
  85                         {
  86                                 level++;
  87                                 searchType = searchType.BaseType;
  88                         }
  89
  90                         return level;
  91                 }
  92
  93                 internal static MethodBase FindMostDerivedMatch (MethodBase [] match)
  94                 {
  95                         int highLevel = 0;
  96                         int matchId = -1;
  97                         int count = match.Length;
  98
  99                         for (int current = 0; current < count; current++)
 100                         {
 101                                 MethodBase m = match [current];
 102                                 int level = GetDerivedLevel (m.DeclaringType);
 103                                 if (level == highLevel)
 104                                         throw new AmbiguousMatchException ();
 105                                 // If the argument types differ we
 106                                 // have an ambigous match, as well
 107                                 if (matchId >= 0) {
 108                                         ParameterInfo[] p1 = m.GetParameters ();
 109                                         ParameterInfo[] p2 = match [matchId].GetParameters ();
 110                                         bool equal = true;
 111
 112                                         if (p1.Length != p2.Length)
 113                                                 equal = false;
 114                                         else {
 115                                                 int i;
 116
 117                                                 for (i = 0; i < p1.Length; ++i) {
 118                                                         if (p1 [i].ParameterType != p2 [i].ParameterType) {
 119                                                                 equal = false;
 120                                                                 break;
 121                                                         }
 122                                                 }
 123                                         }
 124
 125                                         if (!equal)
 126                                                 throw new AmbiguousMatchException ();
 127                                 }
 128
 129                                 if (level > highLevel)
 130                                 {
 131                                         highLevel = level;
 132                                         matchId = current;
 133                                 }
 134                         }
 135
 136                         return match[matchId];
 137                 }
 138
 139                 internal sealed class Default : Binder {
 140                         public override FieldInfo BindToField (BindingFlags bindingAttr, FieldInfo[] match, object value, CultureInfo culture)
 141                         {
 142                                 if (match == null)
 143                                         throw new ArgumentNullException ("match");
 144                                 foreach (FieldInfo f in match) {
 145                                         if (check_type (value.GetType (), f.FieldType))
 146                                                 return f;
 147                                 }
 148                                 return null;
 149                         }
 150
 151                         //
 152                         // FIXME: There was a MonoTODO, but it does not explain what the problem is
 153                         //
 154                         public override MethodBase BindToMethod (BindingFlags bindingAttr, MethodBase[] match, ref object[] args, ParameterModifier[] modifiers, CultureInfo culture, string[] names, out object state)
 155                         {
 156                                 Type[] types;
 157                                 if (args == null)
 158                                         types = Type.EmptyTypes;
 159                                 else {
 160                                         types = new Type [args.Length];
 161                                         for (int i = 0; i < args.Length; ++i) {
 162                                                 if (args [i] != null)
 163                                                         types [i] = args [i].GetType ();
 164                                         }
 165                                 }
 166
 167                                 MethodBase selected = null;
 168                                 if (names != null) {
 169                                         foreach (var m in match) {
 170                                                 var parameters = m.GetParameters ();
 171                                                 int i;
 172
 173                                                 /*
 174                                                  * Find the corresponding parameter for each parameter name,
 175                                                  * reorder types/modifiers array during the search.
 176                                                  */
 177                                                 Type[] newTypes = (Type[])types.Clone ();
 178                                                 ParameterModifier[] newModifiers = modifiers != null ? (ParameterModifier[])modifiers.Clone () : null;
 179                                                 for (i = 0; i < names.Length; ++i) {
 180                                                         /* Find the corresponding parameter */
 181                                                         int nindex = -1;
 182                                                         for (int j = 0; j < parameters.Length; ++j) {
 183                                                                 if (parameters [j].Name == names [i]) {
 184                                                                         nindex = j;
 185                                                                         break;
 186                                                                 }
 187                                                         }
 188                                                         if (nindex == -1)
 189                                                                 break;
 190                                                         if (i < newTypes.Length && nindex < types.Length)
 191                                                                 newTypes [i] = types [nindex];
 192                                                         if (modifiers != null && i < newModifiers.Length && nindex < modifiers.Length)
 193                                                                 newModifiers [i] = modifiers [nindex];
 194                                                 }
 195                                                 if (i < names.Length)
 196                                                         continue;
 197
 198                                                 selected = SelectMethod (bindingAttr, new MethodBase [] { m }, newTypes, newModifiers, true);
 199                                                 if (selected != null)
 200                                                         break;
 201                                         }
 202                                 } else {
 203                                         selected = SelectMethod (bindingAttr, match, types, modifiers, true);
 204                                 }
 205
 206                                 state = null;
 207                                 if (selected != null && names != null)
 208                                         ReorderParameters (names, ref args, selected);
 209
 210                                 if (selected != null) {
 211                                         if (args == null)
 212                                                 args = new object [0];
 213
 214                                         AdjustArguments (selected, ref args);
 215                                 }
 216
 217                                 return selected;
 218                         }
 219
 220                         // probably belongs in ReorderArgumentArray
 221                         static void AdjustArguments (MethodBase selected, ref object [] args)
 222                         {
 223                                 var parameters = selected.GetParameters ();
 224                                 var parameters_length = parameters.Length;
 225                                 if (parameters_length == 0)
 226                                         return;
 227
 228                                 var last_parameter = parameters [parameters.Length - 1];
 229                                 Type last_parameter_type = last_parameter.ParameterType;
 230                                 if (!Attribute.IsDefined (last_parameter, typeof (ParamArrayAttribute)))
 231                                         return;
 232
 233                                 var args_length = args.Length;
 234                                 var param_args_count = args_length + 1 - parameters_length;
 235                                 var first_vararg_index = args_length - param_args_count;
 236                                 if (first_vararg_index < args_length) {
 237                                         var first_vararg = args [first_vararg_index];
 238                                         if (first_vararg != null && first_vararg.GetType () == last_parameter_type)
 239                                                 return;
 240                                 }
 241
 242                                 var params_args = Array.CreateInstance (last_parameter_type.GetElementType (), param_args_count);
 243                                 for (int i = 0; i < param_args_count; i++)
 244                                         params_args.SetValue (args [first_vararg_index + i], i);
 245
 246                                 var adjusted = new object [parameters_length];
 247                                 Array.Copy (args, adjusted, parameters_length - 1);
 248
 249                                 adjusted [adjusted.Length - 1] = params_args;
 250                                 args = adjusted;
 251                         }
 252
 253                         void ReorderParameters (string [] names, ref object [] args, MethodBase selected)
 254                         {
 255                                 object [] newArgs = new object [args.Length];
 256                                 Array.Copy (args, newArgs, args.Length);
 257                                 ParameterInfo [] plist = selected.GetParameters ();
 258                                 for (int n = 0; n < names.Length; n++)
 259                                         for (int p = 0; p < plist.Length; p++) {
 260                                                 if (names [n] == plist [p].Name) {
 261                                                         newArgs [p] = args [n];
 262                                                         break;
 263                                                 }
 264                                         }
 265                                 Array.Copy (newArgs, args, args.Length);
 266                         }
 267
 268                         static bool IsArrayAssignable (Type object_type, Type target_type)
 269                         {
 270                                 if (object_type.IsArray && target_type.IsArray)
 271                                         return IsArrayAssignable (object_type.GetElementType (), target_type.GetElementType ());
 272
 273                                 if (target_type.IsAssignableFrom (object_type))
 274                                         return true;
 275
 276                                 return false;
 277                         }
 278
 279                         public override object ChangeType (object value, Type type, CultureInfo culture)
 280                         {
 281                                 if (value == null)
 282                                         return null;
 283                                 Type vtype = value.GetType ();
 284                                 if (type.IsByRef)
 285                                         type = type.GetElementType ();
 286                                 if (vtype == type || type.IsInstanceOfType (value))
 287                                         return value;
 288                                 if (vtype.IsArray && type.IsArray){
 289                                         if (IsArrayAssignable (vtype.GetElementType (), type.GetElementType ()))
 290                                                 return value;
 291                                 }
 292
 293                                 if (check_type (vtype, type)) {
 294                                         // These are not supported by Convert
 295                                         if (type.IsEnum)
 296                                                 return Enum.ToObject (type, value);
 297                                         if (vtype == typeof (Char)) {
 298                                                 if (type == typeof (double))
 299                                                         return (double)(char)value;
 300                                                 if (type == typeof (float))
 301                                                         return (float)(char)value;
 302                                         }
 303                                         if (vtype == typeof (IntPtr) && type.IsPointer)
 304                                                 return value;
 305                                         return Convert.ChangeType (value, type);
 306                                 }
 307                                 return null;
 308                         }
 309
 310                         [MonoTODO ("This method does not do anything in Mono")]
 311                         public override void ReorderArgumentArray (ref object[] args, object state)
 312                         {
 313                                 //do nothing until we support named arguments
 314                                 //throw new NotImplementedException ();
 315                         }
 316
 317                         private static bool check_type (Type from, Type to) {
 318                                 if (from == to)
 319                                         return true;
 320
 321                                 if (from == null)
 322                                         return true;
 323
 324                                 if (to.IsByRef != from.IsByRef)
 325                                         return false;
 326
 327                                 if (to.IsInterface)
 328                                         return to.IsAssignableFrom (from);
 329
 330                                 if (to.IsEnum) {
 331                                         to = Enum.GetUnderlyingType (to);
 332                                         if (from == to)
 333                                                 return true;
 334                                 }
 335
 336                                 if (to.IsGenericType && to.GetGenericTypeDefinition () == typeof (Nullable<>) && to.GetGenericArguments ()[0] == from)
 337                                         return true;
 338
 339                                 TypeCode fromt = Type.GetTypeCode (from);
 340                                 TypeCode tot = Type.GetTypeCode (to);
 341
 342                                 switch (fromt) {
 343                                 case TypeCode.Char:
 344                                         switch (tot) {
 345                                         case TypeCode.UInt16:
 346                                         case TypeCode.UInt32:
 347                                         case TypeCode.Int32:
 348                                         case TypeCode.UInt64:
 349                                         case TypeCode.Int64:
 350                                         case TypeCode.Single:
 351                                         case TypeCode.Double:
 352                                                 return true;
 353                                         }
 354                                         return to == typeof (object);
 355                                 case TypeCode.Byte:
 356                                         switch (tot) {
 357                                         case TypeCode.Char:
 358                                         case TypeCode.UInt16:
 359                                         case TypeCode.Int16:
 360                                         case TypeCode.UInt32:
 361                                         case TypeCode.Int32:
 362                                         case TypeCode.UInt64:
 363                                         case TypeCode.Int64:
 364                                         case TypeCode.Single:
 365                                         case TypeCode.Double:
 366                                                 return true;
 367                                         }
 368                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 369                                 case TypeCode.SByte:
 370                                         switch (tot) {
 371                                         case TypeCode.Int16:
 372                                         case TypeCode.Int32:
 373                                         case TypeCode.Int64:
 374                                         case TypeCode.Single:
 375                                         case TypeCode.Double:
 376                                                 return true;
 377                                         }
 378                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 379                                 case TypeCode.UInt16:
 380                                         switch (tot) {
 381                                         case TypeCode.UInt32:
 382                                         case TypeCode.Int32:
 383                                         case TypeCode.UInt64:
 384                                         case TypeCode.Int64:
 385                                         case TypeCode.Single:
 386                                         case TypeCode.Double:
 387                                                 return true;
 388                                         }
 389                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 390                                 case TypeCode.Int16:
 391                                         switch (tot) {
 392                                         case TypeCode.Int32:
 393                                         case TypeCode.Int64:
 394                                         case TypeCode.Single:
 395                                         case TypeCode.Double:
 396                                                 return true;
 397                                         }
 398                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 399                                 case TypeCode.UInt32:
 400                                         switch (tot) {
 401                                         case TypeCode.UInt64:
 402                                         case TypeCode.Int64:
 403                                         case TypeCode.Single:
 404                                         case TypeCode.Double:
 405                                                 return true;
 406                                         }
 407                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 408                                 case TypeCode.Int32:
 409                                         switch (tot) {
 410                                         case TypeCode.Int64:
 411                                         case TypeCode.Single:
 412                                         case TypeCode.Double:
 413                                                 return true;
 414                                         }
 415                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 416                                 case TypeCode.UInt64:
 417                                 case TypeCode.Int64:
 418                                         switch (tot) {
 419                                         case TypeCode.Single:
 420                                         case TypeCode.Double:
 421                                                 return true;
 422                                         }
 423                                         return to == typeof (object) || (from.IsEnum && to == typeof (Enum));
 424                                 case TypeCode.Single:
 425                                         return tot == TypeCode.Double || to == typeof (object);
 426                                 default:
 427                                         /* TODO: handle valuetype -> byref */
 428                                         if (to == typeof (object) && from.IsValueType)
 429                                                 return true;
 430                                         if (to.IsPointer && from == typeof (IntPtr))
 431                                                 return true;
 432
 433                                         return to.IsAssignableFrom (from);
 434                                 }
 435                         }
 436
 437                         private static bool check_arguments (Type[] types, ParameterInfo[] args, bool allowByRefMatch) {
 438                                 for (int i = 0; i < types.Length; ++i) {
 439                                         bool match = check_type (types [i], args [i].ParameterType);
 440                                         if (!match && allowByRefMatch) {
 441                                                 Type param_type = args [i].ParameterType;
 442                                                 if (param_type.IsByRef)
 443                                                         match = check_type (types [i], param_type.GetElementType ());
 444                                         }
 445                                         if (!match)
 446                                                 return false;
 447                                 }
 448                                 return true;
 449                         }
 450
 451                         public override MethodBase SelectMethod (BindingFlags bindingAttr, MethodBase [] match, Type [] types, ParameterModifier [] modifiers)
 452                         {
 453                                 return SelectMethod (bindingAttr, match, types, modifiers,
 454                                         false);
 455                         }
 456
 457                         MethodBase SelectMethod (BindingFlags bindingAttr, MethodBase[] match, Type[] types, ParameterModifier[] modifiers, bool allowByRefMatch)
 458                         {
 459                                 MethodBase m;
 460                                 int i, j;
 461
 462                                 if (match == null)
 463                                         throw new ArgumentNullException ("match");
 464
 465                                 /* first look for an exact match... */
 466                                 MethodBase exact_match = null;
 467                                 for (i = 0; i < match.Length; ++i) {
 468                                         m = match [i];
 469                                         ParameterInfo[] args = m.GetParameters ();
 470                                         if (args.Length != types.Length)
 471                                                 continue;
 472                                         for (j = 0; j < types.Length; ++j) {
 473                                                 if (types [j] != args [j].ParameterType)
 474                                                         break;
 475                                         }
 476                                         if (j == types.Length) {
 477                                                 if (exact_match != null) {
 478                                                         exact_match = null;
 479                                                         break;
 480                                                 } else {
 481                                                         exact_match = m;
 482                                                 }
 483                                         }
 484                                 }
 485                                 if (exact_match != null)
 486                                         return exact_match;
 487
 488                                 /* Try methods with ParamArray attribute */
 489                                 bool isdefParamArray = false;
 490                                 Type elementType = null;
 491                                 for (i = 0; i < match.Length; ++i) {
 492                                         m = match [i];
 493                                         ParameterInfo[] args = m.GetParameters ();
 494                                         if (args.Length > types.Length + 1)
 495                                                 continue;
 496                                         else if (args.Length == 0)
 497                                                 continue;
 498                                         isdefParamArray = Attribute.IsDefined (args [args.Length - 1], typeof (ParamArrayAttribute));
 499                                         if (!isdefParamArray)
 500                                                 continue;
 501                                         elementType = args [args.Length - 1].ParameterType.GetElementType ();
 502                                         for (j = 0; j < types.Length; ++j) {
 503                                                 if (j < (args.Length - 1) && types [j] != args [j].ParameterType)
 504                                                         break;
 505                                                 else if (j >= (args.Length - 1) && types [j] != elementType)
 506                                                         break;
 507                                         }
 508                                         if (j == types.Length)
 509                                                 return m;
 510                                 }
 511
 512                                 if ((int)(bindingAttr & BindingFlags.ExactBinding) != 0)
 513                                         return null;
 514
 515                                 MethodBase result = null;
 516                                 for (i = 0; i < match.Length; ++i) {
 517                                         m = match [i];
 518                                         ParameterInfo[] args = m.GetParameters ();
 519                                         if (args.Length != types.Length)
 520                                                 continue;
 521                                         if (!check_arguments (types, args, allowByRefMatch))
 522                                                 continue;
 523
 524                                         if (result != null)
 525                                                 result = GetBetterMethod (result, m, types);
 526                                         else
 527                                                 result = m;
 528                                 }
 529
 530                                 return result;
 531                         }
 532
 533                         MethodBase GetBetterMethod (MethodBase m1, MethodBase m2, Type [] types)
 534                         {
 535                                 ParameterInfo [] pl1 = m1.GetParameters ();
 536                                 ParameterInfo [] pl2 = m2.GetParameters ();
 537                                 int prev = 0;
 538                                 for (int i = 0; i < pl1.Length; i++) {
 539                                         int cmp = CompareCloserType (pl1 [i].ParameterType, pl2 [i].ParameterType);
 540                                         if (cmp != 0 && prev != 0 && prev != cmp)
 541                                                 throw new AmbiguousMatchException ();
 542                                         if (cmp != 0)
 543                                                 prev = cmp;
 544                                 }
 545                                 if (prev != 0)
 546                                         return prev > 0 ? m2 : m1;
 547
 548                                 Type dt1 = m1.DeclaringType;
 549                                 Type dt2 = m2.DeclaringType;
 550                                 if (dt1 != dt2) {
 551                                         if (dt1.IsSubclassOf(dt2))
 552                                                 return m1;
 553                                         if (dt2.IsSubclassOf(dt1))
 554                                                 return m2;
 555                                 }
 556
 557                                 bool va1 = (m1.CallingConvention & CallingConventions.VarArgs) != 0;
 558                                 bool va2 = (m2.CallingConvention & CallingConventions.VarArgs) != 0;
 559                                 if (va1 && !va2)
 560                                         return m2;
 561                                 if (va2 && !va1)
 562                                         return m1;
 563
 564                                 throw new AmbiguousMatchException ();
 565                         }
 566
 567                         int CompareCloserType (Type t1, Type t2)
 568                         {
 569                                 if (t1 == t2)
 570                                         return 0;
 571                                 if (t1.IsGenericParameter && !t2.IsGenericParameter)
 572                                         return 1; // t2
 573                                 if (!t1.IsGenericParameter && t2.IsGenericParameter)
 574                                         return -1; // t1
 575                                 if (t1.HasElementType && t2.HasElementType)
 576                                         return CompareCloserType (
 577                                                 t1.GetElementType (),
 578                                                 t2.GetElementType ());
 579
 580                                 if (t1.IsSubclassOf (t2))
 581                                         return -1; // t1
 582                                 if (t2.IsSubclassOf (t1))
 583                                         return 1; // t2
 584
 585                                 if (t1.IsInterface && Array.IndexOf (t2.GetInterfaces (), t1) >= 0)
 586                                         return 1; // t2
 587                                 if (t2.IsInterface && Array.IndexOf (t1.GetInterfaces (), t2) >= 0)
 588                                         return -1; // t1
 589
 590                                 // What kind of cases could reach here?
 591                                 return 0;
 592                         }
 593
 594                         public override PropertyInfo SelectProperty (BindingFlags bindingAttr, PropertyInfo[] match, Type returnType, Type[] indexes, ParameterModifier[] modifiers)
 595                         {
 596                                 if (match == null || match.Length == 0)
 597                                         throw new ArgumentException ("No properties provided", "match");
 598
 599                                 bool haveRet = (returnType != null);
 600                                 int idxlen = (indexes != null) ? indexes.Length : -1;
 601                                 PropertyInfo result = null;
 602                                 int i;
 603                                 int best_score = Int32.MaxValue - 1;
 604                                 int fail_score = Int32.MaxValue;
 605                                 int level = 0;
 606
 607                                 for (i = match.Length - 1; i >= 0; i--) {
 608                                         PropertyInfo p = match [i];
 609                                         ParameterInfo[] args = p.GetIndexParameters ();
 610                                         if (idxlen >= 0 && idxlen != args.Length)
 611                                                 continue;
 612
 613                                         if (haveRet && p.PropertyType != returnType)
 614                                                 continue;
 615
 616                                         int score = Int32.MaxValue - 1;
 617                                         if (idxlen > 0) {
 618                                                 score = check_arguments_with_score (indexes, args);
 619                                                 if (score == -1)
 620                                                         continue;
 621                                         }
 622
 623                                         int new_level = GetDerivedLevel (p.DeclaringType);
 624                                         if (result != null) {
 625                                                 if (best_score < score)
 626                                                         continue;
 627
 628                                                 if (best_score == score) {
 629                                                         if (level == new_level) {
 630                                                                 // Keep searching. May be there's something
 631                                                                 // better for us.
 632                                                                 fail_score = score;
 633                                                                 continue;
 634                                                         }
 635
 636                                                         if (level > new_level)
 637                                                                 continue;
 638                                                 }
 639                                         }
 640
 641                                         result = p;
 642                                         best_score = score;
 643                                         level = new_level;
 644                                 }
 645
 646                                 if (fail_score <= best_score)
 647                                         throw new AmbiguousMatchException ();
 648
 649                                 return result;
 650                         }
 651
 652                         static int check_arguments_with_score (Type [] types, ParameterInfo [] args)
 653                         {
 654                                 int worst = -1;
 655
 656                                 for (int i = 0; i < types.Length; ++i) {
 657                                         int res = check_type_with_score (types [i], args [i].ParameterType);
 658                                         if (res == -1)
 659                                                 return -1;
 660
 661                                         if (worst < res)
 662                                                 worst = res;
 663                                 }
 664
 665                                 return worst;
 666                         }
 667
 668                         // 0 -> same type or null and !valuetype
 669                         // 1 -> to == Enum
 670                         // 2 -> value type that don't lose data
 671                         // 3 -> to == IsAssignableFrom
 672                         // 4 -> to == object
 673                         static int check_type_with_score (Type from, Type to)
 674                         {
 675                                 if (from == null)
 676                                         return to.IsValueType ? -1 : 0;
 677
 678                                 if (from == to)
 679                                         return 0;
 680
 681                                 if (to == typeof (object))
 682                                         return 4;
 683
 684                                 TypeCode fromt = Type.GetTypeCode (from);
 685                                 TypeCode tot = Type.GetTypeCode (to);
 686
 687                                 switch (fromt) {
 688                                 case TypeCode.Char:
 689                                         switch (tot) {
 690                                         case TypeCode.UInt16:
 691                                                 return 0;
 692
 693                                         case TypeCode.UInt32:
 694                                         case TypeCode.Int32:
 695                                         case TypeCode.UInt64:
 696                                         case TypeCode.Int64:
 697                                         case TypeCode.Single:
 698                                         case TypeCode.Double:
 699                                                 return 2;
 700                                         }
 701                                         return -1;
 702                                 case TypeCode.Byte:
 703                                         switch (tot) {
 704                                         case TypeCode.Char:
 705                                         case TypeCode.UInt16:
 706                                         case TypeCode.Int16:
 707                                         case TypeCode.UInt32:
 708                                         case TypeCode.Int32:
 709                                         case TypeCode.UInt64:
 710                                         case TypeCode.Int64:
 711                                         case TypeCode.Single:
 712                                         case TypeCode.Double:
 713                                                 return 2;
 714                                         }
 715                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 716                                 case TypeCode.SByte:
 717                                         switch (tot) {
 718                                         case TypeCode.Int16:
 719                                         case TypeCode.Int32:
 720                                         case TypeCode.Int64:
 721                                         case TypeCode.Single:
 722                                         case TypeCode.Double:
 723                                                 return 2;
 724                                         }
 725                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 726                                 case TypeCode.UInt16:
 727                                         switch (tot) {
 728                                         case TypeCode.UInt32:
 729                                         case TypeCode.Int32:
 730                                         case TypeCode.UInt64:
 731                                         case TypeCode.Int64:
 732                                         case TypeCode.Single:
 733                                         case TypeCode.Double:
 734                                                 return 2;
 735                                         }
 736                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 737                                 case TypeCode.Int16:
 738                                         switch (tot) {
 739                                         case TypeCode.Int32:
 740                                         case TypeCode.Int64:
 741                                         case TypeCode.Single:
 742                                         case TypeCode.Double:
 743                                                 return 2;
 744                                         }
 745                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 746                                 case TypeCode.UInt32:
 747                                         switch (tot) {
 748                                         case TypeCode.UInt64:
 749                                         case TypeCode.Int64:
 750                                         case TypeCode.Single:
 751                                         case TypeCode.Double:
 752                                                 return 2;
 753                                         }
 754                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 755                                 case TypeCode.Int32:
 756                                         switch (tot) {
 757                                         case TypeCode.Int64:
 758                                         case TypeCode.Single:
 759                                         case TypeCode.Double:
 760                                                 return 2;
 761                                         }
 762                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 763                                 case TypeCode.UInt64:
 764                                 case TypeCode.Int64:
 765                                         switch (tot) {
 766                                         case TypeCode.Single:
 767                                         case TypeCode.Double:
 768                                                 return 2;
 769                                         }
 770                                         return (from.IsEnum && to == typeof (Enum)) ? 1 : -1;
 771                                 case TypeCode.Single:
 772                                         return tot == TypeCode.Double ? 2 : -1;
 773                                 default:
 774                                         return (to.IsAssignableFrom (from)) ? 3 : -1;
 775                                 }
 776                         }
 777                 }
 778         }
 779 }
 780