mcs/mcs/parameter.cs

   1 //
   2 // parameter.cs: Parameter definition.
   3 //
   4 // Author: Miguel de Icaza (miguel@gnu.org)
   5 //         Marek Safar (marek.safar@seznam.cz)
   6 //
   7 // Dual licensed under the terms of the MIT X11 or GNU GPL
   8 //
   9 // Copyright 2001-2003 Ximian, Inc (http://www.ximian.com)
  10 // Copyright 2003-2008 Novell, Inc.
  11 // Copyright 2011 Xamarin Inc
  12 //
  13 //
  14 using System;
  15 using System.Text;
  16
  17 #if STATIC
  18 using MetaType = IKVM.Reflection.Type;
  19 using IKVM.Reflection;
  20 using IKVM.Reflection.Emit;
  21 #else
  22 using MetaType = System.Type;
  23 using System.Reflection;
  24 using System.Reflection.Emit;
  25 #endif
  26
  27 namespace Mono.CSharp {
  28
  29         /// <summary>
  30         ///   Abstract Base class for parameters of a method.
  31         /// </summary>
  32         public abstract class ParameterBase : Attributable
  33         {
  34                 protected ParameterBuilder builder;
  35
  36                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
  37                 {
  38 #if false
  39                         if (a.Type == pa.MarshalAs) {
  40                                 UnmanagedMarshal marshal = a.GetMarshal (this);
  41                                 if (marshal != null) {
  42                                         builder.SetMarshal (marshal);
  43                                 }
  44                                 return;
  45                         }
  46 #endif
  47                         if (a.HasSecurityAttribute) {
  48                                 a.Error_InvalidSecurityParent ();
  49                                 return;
  50                         }
  51
  52                         if (a.Type == pa.Dynamic) {
  53                                 a.Error_MisusedDynamicAttribute ();
  54                                 return;
  55                         }
  56
  57                         builder.SetCustomAttribute ((ConstructorInfo) ctor.GetMetaInfo (), cdata);
  58                 }
  59
  60                 public ParameterBuilder Builder {
  61                         get {
  62                                 return builder;
  63                         }
  64                 }
  65
  66                 public override bool IsClsComplianceRequired()
  67                 {
  68                         return false;
  69                 }
  70         }
  71
  72         /// <summary>
  73         /// Class for applying custom attributes on the return type
  74         /// </summary>
  75         public class ReturnParameter : ParameterBase
  76         {
  77                 MemberCore method;
  78
  79                 // TODO: merge method and mb
  80                 public ReturnParameter (MemberCore method, MethodBuilder mb, Location location)
  81                 {
  82                         this.method = method;
  83                         try {
  84                                 builder = mb.DefineParameter (0, ParameterAttributes.None, "");
  85                         }
  86                         catch (ArgumentOutOfRangeException) {
  87                                 method.Compiler.Report.RuntimeMissingSupport (location, "custom attributes on the return type");
  88                         }
  89                 }
  90
  91                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
  92                 {
  93                         if (a.Type == pa.CLSCompliant) {
  94                                 method.Compiler.Report.Warning (3023, 1, a.Location,
  95                                         "CLSCompliant attribute has no meaning when applied to return types. Try putting it on the method instead");
  96                         }
  97
  98                         // This occurs after Warning -28
  99                         if (builder == null)
 100                                 return;
 101
 102                         base.ApplyAttributeBuilder (a, ctor, cdata, pa);
 103                 }
 104
 105                 public override AttributeTargets AttributeTargets {
 106                         get {
 107                                 return AttributeTargets.ReturnValue;
 108                         }
 109                 }
 110
 111                 /// <summary>
 112                 /// Is never called
 113                 /// </summary>
 114                 public override string[] ValidAttributeTargets {
 115                         get {
 116                                 return null;
 117                         }
 118                 }
 119         }
 120
 121         public class ImplicitLambdaParameter : Parameter
 122         {
 123                 public ImplicitLambdaParameter (string name, Location loc)
 124                         : base (null, name, Modifier.NONE, null, loc)
 125                 {
 126                 }
 127
 128                 public override TypeSpec Resolve (IMemberContext ec, int index)
 129                 {
 130                         if (parameter_type == null)
 131                                 throw new InternalErrorException ("A type of implicit lambda parameter `{0}' is not set",
 132                                         Name);
 133
 134                         base.idx = index;
 135                         return parameter_type;
 136                 }
 137
 138                 public void SetParameterType (TypeSpec type)
 139                 {
 140                         parameter_type = type;
 141                 }
 142         }
 143
 144         public class ParamsParameter : Parameter {
 145                 public ParamsParameter (FullNamedExpression type, string name, Attributes attrs, Location loc):
 146                         base (type, name, Parameter.Modifier.PARAMS, attrs, loc)
 147                 {
 148                 }
 149
 150                 public override TypeSpec Resolve (IMemberContext ec, int index)
 151                 {
 152                         if (base.Resolve (ec, index) == null)
 153                                 return null;
 154
 155                         var ac = parameter_type as ArrayContainer;
 156                         if (ac == null || ac.Rank != 1) {
 157                                 ec.Module.Compiler.Report.Error (225, Location, "The params parameter must be a single dimensional array");
 158                                 return null;
 159                         }
 160
 161                         return parameter_type;
 162                 }
 163
 164                 public override void ApplyAttributes (MethodBuilder mb, ConstructorBuilder cb, int index, PredefinedAttributes pa)
 165                 {
 166                         base.ApplyAttributes (mb, cb, index, pa);
 167                         pa.ParamArray.EmitAttribute (builder);
 168                 }
 169         }
 170
 171         public class ArglistParameter : Parameter {
 172                 // Doesn't have proper type because it's never chosen for better conversion
 173                 public ArglistParameter (Location loc) :
 174                         base (null, String.Empty, Parameter.Modifier.NONE, null, loc)
 175                 {
 176                         parameter_type = InternalType.Arglist;
 177                 }
 178
 179                 public override void  ApplyAttributes (MethodBuilder mb, ConstructorBuilder cb, int index, PredefinedAttributes pa)
 180                 {
 181                         // Nothing to do
 182                 }
 183
 184                 public override bool CheckAccessibility (InterfaceMemberBase member)
 185                 {
 186                         return true;
 187                 }
 188
 189                 public override TypeSpec Resolve (IMemberContext ec, int index)
 190                 {
 191                         return parameter_type;
 192                 }
 193         }
 194
 195         public interface IParameterData
 196         {
 197                 Expression DefaultValue { get; }
 198                 bool HasExtensionMethodModifier { get; }
 199                 bool HasDefaultValue { get; }
 200                 Parameter.Modifier ModFlags { get; }
 201                 string Name { get; }
 202         }
 203
 204         //
 205         // Parameter information created by parser
 206         //
 207         public class Parameter : ParameterBase, IParameterData, ILocalVariable // TODO: INamedBlockVariable
 208         {
 209                 [Flags]
 210                 public enum Modifier : byte {
 211                         NONE    = 0,
 212                         PARAMS  = 1 << 0,
 213                         REF = 1 << 1,
 214                         OUT = 1 << 2,
 215                         This = 1 << 3,
 216                         CallerMemberName = 1 << 4,
 217                         CallerLineNumber = 1 << 5,
 218                         CallerFilePath = 1 << 6,
 219
 220                         RefOutMask = REF | OUT,
 221                         ModifierMask = PARAMS | REF | OUT | This,
 222                         CallerMask = CallerMemberName | CallerLineNumber | CallerFilePath
 223                 }
 224
 225                 static readonly string[] attribute_targets = new string[] { "param" };
 226                 static readonly string[] attribute_targets_primary = new string[] { "param", "field" };
 227
 228                 FullNamedExpression texpr;
 229                 Modifier modFlags;
 230                 string name;
 231                 Expression default_expr;
 232                 protected TypeSpec parameter_type;
 233                 readonly Location loc;
 234                 protected int idx;
 235                 public bool HasAddressTaken;
 236
 237                 Constructor primary_constructor;
 238                 TemporaryVariableReference expr_tree_variable;
 239
 240                 HoistedParameter hoisted_variant;
 241
 242                 public Parameter (FullNamedExpression type, string name, Modifier mod, Attributes attrs, Location loc)
 243                 {
 244                         this.name = name;
 245                         modFlags = mod;
 246                         this.loc = loc;
 247                         texpr = type;
 248
 249                         // Only assign, attributes will be attached during resolve
 250                         base.attributes = attrs;
 251                 }
 252
 253                 #region Properties
 254
 255                 public Expression DefaultExpression {
 256                         get {
 257                                 return default_expr;
 258                         }
 259                 }
 260
 261                 public DefaultParameterValueExpression DefaultValue {
 262                         get {
 263                                 return default_expr as DefaultParameterValueExpression;
 264                         }
 265                         set {
 266                                 default_expr = value;
 267                         }
 268                 }
 269
 270                 Expression IParameterData.DefaultValue {
 271                         get {
 272                                 var expr = default_expr as DefaultParameterValueExpression;
 273                                 return expr == null ? default_expr : expr.Child;
 274                         }
 275                 }
 276
 277                 bool HasOptionalExpression {
 278                         get {
 279                                 return default_expr is DefaultParameterValueExpression;
 280                         }
 281                 }
 282
 283                 public Location Location {
 284                         get {
 285                                 return loc;
 286                         }
 287                 }
 288
 289                 public Modifier ParameterModifier {
 290                         get {
 291                                 return modFlags;
 292                         }
 293                 }
 294
 295                 public TypeSpec Type {
 296                         get {
 297                                 return parameter_type;
 298                         }
 299                         set {
 300                                 parameter_type = value;
 301                         }
 302                 }
 303
 304                 public FullNamedExpression TypeExpression  {
 305                         get {
 306                                 return texpr;
 307                         }
 308                 }
 309
 310                 public override string[] ValidAttributeTargets {
 311                         get {
 312                                 return primary_constructor != null ? attribute_targets_primary : attribute_targets;
 313                         }
 314                 }
 315
 316                 #endregion
 317
 318                 public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
 319                 {
 320                         if (a.Target == AttributeTargets.Field) {
 321                                 var field = MemberCache.FindMember (primary_constructor.Spec.DeclaringType, MemberFilter.Field (name, parameter_type), BindingRestriction.DeclaredOnly);
 322                                 ((Field)field.MemberDefinition).ApplyAttributeBuilder (a, ctor, cdata, pa);
 323                                 return;
 324                         }
 325
 326                         if (a.Type == pa.In && ModFlags == Modifier.OUT) {
 327                                 a.Report.Error (36, a.Location, "An out parameter cannot have the `In' attribute");
 328                                 return;
 329                         }
 330
 331                         if (a.Type == pa.ParamArray) {
 332                                 a.Report.Error (674, a.Location, "Do not use `System.ParamArrayAttribute'. Use the `params' keyword instead");
 333                                 return;
 334                         }
 335
 336                         if (a.Type == pa.Out && (ModFlags & Modifier.REF) != 0 &&
 337                             !OptAttributes.Contains (pa.In)) {
 338                                 a.Report.Error (662, a.Location,
 339                                         "Cannot specify only `Out' attribute on a ref parameter. Use both `In' and `Out' attributes or neither");
 340                                 return;
 341                         }
 342
 343                         if (a.Type == pa.CLSCompliant) {
 344                                 a.Report.Warning (3022, 1, a.Location, "CLSCompliant attribute has no meaning when applied to parameters. Try putting it on the method instead");
 345                         } else if (a.Type == pa.DefaultParameterValue || a.Type == pa.OptionalParameter) {
 346                                 if (HasOptionalExpression) {
 347                                         a.Report.Error (1745, a.Location,
 348                                                 "Cannot specify `{0}' attribute on optional parameter `{1}'",
 349                                                 a.Type.GetSignatureForError ().Replace ("Attribute", ""), Name);
 350                                 }
 351
 352                                 if (a.Type == pa.DefaultParameterValue)
 353                                         return;
 354                         } else if (a.Type == pa.CallerMemberNameAttribute) {
 355                                 if ((modFlags & Modifier.CallerMemberName) == 0) {
 356                                         a.Report.Error (4022, a.Location,
 357                                                 "The CallerMemberName attribute can only be applied to parameters with default value");
 358                                 }
 359                         } else if (a.Type == pa.CallerLineNumberAttribute) {
 360                                 if ((modFlags & Modifier.CallerLineNumber) == 0) {
 361                                         a.Report.Error (4020, a.Location,
 362                                                 "The CallerLineNumber attribute can only be applied to parameters with default value");
 363                                 }
 364                         } else if (a.Type == pa.CallerFilePathAttribute) {
 365                                 if ((modFlags & Modifier.CallerFilePath) == 0) {
 366                                         a.Report.Error (4021, a.Location,
 367                                                 "The CallerFilePath attribute can only be applied to parameters with default value");
 368                                 }
 369                         }
 370
 371                         base.ApplyAttributeBuilder (a, ctor, cdata, pa);
 372                 }
 373
 374                 public virtual bool CheckAccessibility (InterfaceMemberBase member)
 375                 {
 376                         if (parameter_type == null)
 377                                 return true;
 378
 379                         return member.IsAccessibleAs (parameter_type);
 380                 }
 381
 382                 // <summary>
 383                 //   Resolve is used in method definitions
 384                 // </summary>
 385                 public virtual TypeSpec Resolve (IMemberContext rc, int index)
 386                 {
 387                         if (parameter_type != null)
 388                                 return parameter_type;
 389
 390                         if (attributes != null)
 391                                 attributes.AttachTo (this, rc);
 392
 393                         var ctor = rc.CurrentMemberDefinition as Constructor;
 394                         if (ctor != null && ctor.IsPrimaryConstructor)
 395                                 primary_constructor = ctor;
 396
 397                         parameter_type = texpr.ResolveAsType (rc);
 398                         if (parameter_type == null)
 399                                 return null;
 400
 401                         this.idx = index;
 402
 403                         if ((modFlags & Parameter.Modifier.RefOutMask) != 0 && parameter_type.IsSpecialRuntimeType) {
 404                                 rc.Module.Compiler.Report.Error (1601, Location, "Method or delegate parameter cannot be of type `{0}'",
 405                                         GetSignatureForError ());
 406                                 return null;
 407                         }
 408
 409                         VarianceDecl.CheckTypeVariance (parameter_type,
 410                                 (modFlags & Parameter.Modifier.RefOutMask) != 0 ? Variance.None : Variance.Contravariant,
 411                                 rc);
 412
 413                         if (parameter_type.IsStatic) {
 414                                 rc.Module.Compiler.Report.Error (721, Location, "`{0}': static types cannot be used as parameters",
 415                                         texpr.GetSignatureForError ());
 416                                 return parameter_type;
 417                         }
 418
 419                         if ((modFlags & Modifier.This) != 0 && (parameter_type.IsPointer || parameter_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic)) {
 420                                 rc.Module.Compiler.Report.Error (1103, Location, "The extension method cannot be of type `{0}'",
 421                                         parameter_type.GetSignatureForError ());
 422                         }
 423
 424                         return parameter_type;
 425                 }
 426
 427                 void ResolveCallerAttributes (ResolveContext rc)
 428                 {
 429                         var pa = rc.Module.PredefinedAttributes;
 430                         TypeSpec caller_type;
 431
 432                         foreach (var attr in attributes.Attrs) {
 433                                 var atype = attr.ResolveTypeForComparison ();
 434                                 if (atype == null)
 435                                         continue;
 436
 437                                 if (atype == pa.CallerMemberNameAttribute) {
 438                                         caller_type = rc.BuiltinTypes.String;
 439                                         if (caller_type != parameter_type && !Convert.ImplicitReferenceConversionExists (caller_type, parameter_type)) {
 440                                                 rc.Report.Error (4019, attr.Location,
 441                                                         "The CallerMemberName attribute cannot be applied because there is no standard conversion from `{0}' to `{1}'",
 442                                                         caller_type.GetSignatureForError (), parameter_type.GetSignatureForError ());
 443                                         }
 444
 445                                         modFlags |= Modifier.CallerMemberName;
 446                                         continue;
 447                                 }
 448
 449                                 if (atype == pa.CallerLineNumberAttribute) {
 450                                         caller_type = rc.BuiltinTypes.Int;
 451                                         if (caller_type != parameter_type && !Convert.ImplicitNumericConversionExists (caller_type, parameter_type)) {
 452                                                 rc.Report.Error (4017, attr.Location,
 453                                                         "The CallerMemberName attribute cannot be applied because there is no standard conversion from `{0}' to `{1}'",
 454                                                         caller_type.GetSignatureForError (), parameter_type.GetSignatureForError ());
 455                                         }
 456
 457                                         modFlags |= Modifier.CallerLineNumber;
 458                                         continue;
 459                                 }
 460
 461                                 if (atype == pa.CallerFilePathAttribute) {
 462                                         caller_type = rc.BuiltinTypes.String;
 463                                         if (caller_type != parameter_type && !Convert.ImplicitReferenceConversionExists (caller_type, parameter_type)) {
 464                                                 rc.Report.Error (4018, attr.Location,
 465                                                         "The CallerFilePath attribute cannot be applied because there is no standard conversion from `{0}' to `{1}'",
 466                                                         caller_type.GetSignatureForError (), parameter_type.GetSignatureForError ());
 467                                         }
 468
 469                                         modFlags |= Modifier.CallerFilePath;
 470                                         continue;
 471                                 }
 472                         }
 473                 }
 474
 475                 public void ResolveDefaultValue (ResolveContext rc)
 476                 {
 477                         //
 478                         // Default value was specified using an expression
 479                         //
 480                         if (default_expr != null) {
 481                                 ((DefaultParameterValueExpression)default_expr).Resolve (rc, this);
 482                                 if (attributes != null)
 483                                         ResolveCallerAttributes (rc);
 484
 485                                 return;
 486                         }
 487
 488                         if (attributes == null)
 489                                 return;
 490
 491                         var pa = rc.Module.PredefinedAttributes;
 492                         var def_attr = attributes.Search (pa.DefaultParameterValue);
 493                         if (def_attr != null) {
 494                                 if (def_attr.Resolve () == null)
 495                                         return;
 496
 497                                 var default_expr_attr = def_attr.GetParameterDefaultValue ();
 498                                 if (default_expr_attr == null)
 499                                         return;
 500
 501                                 var dpa_rc = def_attr.CreateResolveContext ();
 502                                 default_expr = default_expr_attr.Resolve (dpa_rc);
 503
 504                                 if (default_expr is BoxedCast)
 505                                         default_expr = ((BoxedCast) default_expr).Child;
 506
 507                                 Constant c = default_expr as Constant;
 508                                 if (c == null) {
 509                                         if (parameter_type.BuiltinType == BuiltinTypeSpec.Type.Object) {
 510                                                 rc.Report.Error (1910, default_expr.Location,
 511                                                         "Argument of type `{0}' is not applicable for the DefaultParameterValue attribute",
 512                                                         default_expr.Type.GetSignatureForError ());
 513                                         } else {
 514                                                 rc.Report.Error (1909, default_expr.Location,
 515                                                         "The DefaultParameterValue attribute is not applicable on parameters of type `{0}'",
 516                                                         default_expr.Type.GetSignatureForError ());
 517                                         }
 518
 519                                         default_expr = null;
 520                                         return;
 521                                 }
 522
 523                                 if (TypeSpecComparer.IsEqual (default_expr.Type, parameter_type) ||
 524                                         (default_expr is NullConstant && TypeSpec.IsReferenceType (parameter_type) && !parameter_type.IsGenericParameter) ||
 525                                         parameter_type.BuiltinType == BuiltinTypeSpec.Type.Object) {
 526                                         return;
 527                                 }
 528
 529                                 //
 530                                 // LAMESPEC: Some really weird csc behaviour which we have to mimic
 531                                 // User operators returning same type as parameter type are considered
 532                                 // valid for this attribute only
 533                                 //
 534                                 // struct S { public static implicit operator S (int i) {} }
 535                                 //
 536                                 // void M ([DefaultParameterValue (3)]S s)
 537                                 //
 538                                 var expr = Convert.ImplicitUserConversion (dpa_rc, default_expr, parameter_type, loc);
 539                                 if (expr != null && TypeSpecComparer.IsEqual (expr.Type, parameter_type)) {
 540                                         return;
 541                                 }
 542
 543                                 rc.Report.Error (1908, default_expr.Location, "The type of the default value should match the type of the parameter");
 544                                 return;
 545                         }
 546
 547                         var opt_attr = attributes.Search (pa.OptionalParameter);
 548                         if (opt_attr != null) {
 549                                 default_expr = EmptyExpression.MissingValue;
 550                         }
 551                 }
 552
 553                 public bool HasDefaultValue {
 554                         get { return default_expr != null; }
 555                 }
 556
 557                 public bool HasExtensionMethodModifier {
 558                         get { return (modFlags & Modifier.This) != 0; }
 559                 }
 560
 561                 //
 562                 // Hoisted parameter variant
 563                 //
 564                 public HoistedParameter HoistedVariant {
 565                         get {
 566                                 return hoisted_variant;
 567                         }
 568                         set {
 569                                 hoisted_variant = value;
 570                         }
 571                 }
 572
 573                 public Modifier ModFlags {
 574                         get { return modFlags & ~Modifier.This; }
 575                 }
 576
 577                 public string Name {
 578                         get { return name; }
 579                         set { name = value; }
 580                 }
 581
 582                 public override AttributeTargets AttributeTargets {
 583                         get {
 584                                 return AttributeTargets.Parameter;
 585                         }
 586                 }
 587
 588                 public void Error_DuplicateName (Report r)
 589                 {
 590                         r.Error (100, Location, "The parameter name `{0}' is a duplicate", Name);
 591                 }
 592
 593                 public virtual string GetSignatureForError ()
 594                 {
 595                         string type_name;
 596                         if (parameter_type != null)
 597                                 type_name = parameter_type.GetSignatureForError ();
 598                         else
 599                                 type_name = texpr.GetSignatureForError ();
 600
 601                         string mod = GetModifierSignature (modFlags);
 602                         if (mod.Length > 0)
 603                                 return String.Concat (mod, " ", type_name);
 604
 605                         return type_name;
 606                 }
 607
 608                 public static string GetModifierSignature (Modifier mod)
 609                 {
 610                         switch (mod) {
 611                         case Modifier.OUT:
 612                                 return "out";
 613                         case Modifier.PARAMS:
 614                                 return "params";
 615                         case Modifier.REF:
 616                                 return "ref";
 617                         case Modifier.This:
 618                                 return "this";
 619                         default:
 620                                 return "";
 621                         }
 622                 }
 623
 624                 public void IsClsCompliant (IMemberContext ctx)
 625                 {
 626                         if (parameter_type.IsCLSCompliant ())
 627                                 return;
 628
 629                         ctx.Module.Compiler.Report.Warning (3001, 1, Location,
 630                                 "Argument type `{0}' is not CLS-compliant", parameter_type.GetSignatureForError ());
 631                 }
 632
 633                 public virtual void ApplyAttributes (MethodBuilder mb, ConstructorBuilder cb, int index, PredefinedAttributes pa)
 634                 {
 635                         if (builder != null)
 636                                 throw new InternalErrorException ("builder already exists");
 637
 638                         var pattrs = ParametersCompiled.GetParameterAttribute (modFlags);
 639                         if (HasOptionalExpression)
 640                                 pattrs |= ParameterAttributes.Optional;
 641
 642                         if (mb == null)
 643                                 builder = cb.DefineParameter (index, pattrs, Name);
 644                         else
 645                                 builder = mb.DefineParameter (index, pattrs, Name);
 646
 647                         if (OptAttributes != null)
 648                                 OptAttributes.Emit ();
 649
 650                         if (HasDefaultValue && default_expr.Type != null) {
 651                                 //
 652                                 // Emit constant values for true constants only, the other
 653                                 // constant-like expressions will rely on default value expression
 654                                 //
 655                                 var def_value = DefaultValue;
 656                                 Constant c = def_value != null ? def_value.Child as Constant : default_expr as Constant;
 657                                 if (c != null) {
 658                                         if (c.Type.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
 659                                                 pa.DecimalConstant.EmitAttribute (builder, (decimal) c.GetValue (), c.Location);
 660                                         } else {
 661                                                 builder.SetConstant (c.GetValue ());
 662                                         }
 663                                 } else if (default_expr.Type.IsStruct || default_expr.Type.IsGenericParameter) {
 664                                         //
 665                                         // Handles special case where default expression is used with value-type or type parameter
 666                                         //
 667                                         // void Foo (S s = default (S)) {}
 668                                         //
 669                                         builder.SetConstant (null);
 670                                 }
 671                         }
 672
 673                         if (parameter_type != null) {
 674                                 if (parameter_type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
 675                                         pa.Dynamic.EmitAttribute (builder);
 676                                 } else if (parameter_type.HasDynamicElement) {
 677                                         pa.Dynamic.EmitAttribute (builder, parameter_type, Location);
 678                                 }
 679                         }
 680                 }
 681
 682                 public Parameter Clone ()
 683                 {
 684                         Parameter p = (Parameter) MemberwiseClone ();
 685                         if (attributes != null)
 686                                 p.attributes = attributes.Clone ();
 687
 688                         return p;
 689                 }
 690
 691                 public ExpressionStatement CreateExpressionTreeVariable (BlockContext ec)
 692                 {
 693                         if ((modFlags & Modifier.RefOutMask) != 0)
 694                                 ec.Report.Error (1951, Location, "An expression tree parameter cannot use `ref' or `out' modifier");
 695
 696                         expr_tree_variable = TemporaryVariableReference.Create (ResolveParameterExpressionType (ec, Location).Type, ec.CurrentBlock.ParametersBlock, Location);
 697                         expr_tree_variable = (TemporaryVariableReference) expr_tree_variable.Resolve (ec);
 698
 699                         Arguments arguments = new Arguments (2);
 700                         arguments.Add (new Argument (new TypeOf (parameter_type, Location)));
 701                         arguments.Add (new Argument (new StringConstant (ec.BuiltinTypes, Name, Location)));
 702                         return new SimpleAssign (ExpressionTreeVariableReference (),
 703                                 Expression.CreateExpressionFactoryCall (ec, "Parameter", null, arguments, Location));
 704                 }
 705
 706                 public void Emit (EmitContext ec)
 707                 {
 708                         ec.EmitArgumentLoad (idx);
 709                 }
 710
 711                 public void EmitAssign (EmitContext ec)
 712                 {
 713                         ec.EmitArgumentStore (idx);
 714                 }
 715
 716                 public void EmitAddressOf (EmitContext ec)
 717                 {
 718                         if ((ModFlags & Modifier.RefOutMask) != 0) {
 719                                 ec.EmitArgumentLoad (idx);
 720                         } else {
 721                                 ec.EmitArgumentAddress (idx);
 722                         }
 723                 }
 724
 725                 public TemporaryVariableReference ExpressionTreeVariableReference ()
 726                 {
 727                         return expr_tree_variable;
 728                 }
 729
 730                 //
 731                 // System.Linq.Expressions.ParameterExpression type
 732                 //
 733                 public static TypeExpr ResolveParameterExpressionType (IMemberContext ec, Location location)
 734                 {
 735                         TypeSpec p_type = ec.Module.PredefinedTypes.ParameterExpression.Resolve ();
 736                         return new TypeExpression (p_type, location);
 737                 }
 738
 739                 public void Warning_UselessOptionalParameter (Report Report)
 740                 {
 741                         Report.Warning (1066, 1, Location,
 742                                 "The default value specified for optional parameter `{0}' will never be used",
 743                                 Name);
 744                 }
 745         }
 746
 747         //
 748         // Imported or resolved parameter information
 749         //
 750         public class ParameterData : IParameterData
 751         {
 752                 readonly string name;
 753                 readonly Parameter.Modifier modifiers;
 754                 readonly Expression default_value;
 755
 756                 public ParameterData (string name, Parameter.Modifier modifiers)
 757                 {
 758                         this.name = name;
 759                         this.modifiers = modifiers;
 760                 }
 761
 762                 public ParameterData (string name, Parameter.Modifier modifiers, Expression defaultValue)
 763                         : this (name, modifiers)
 764                 {
 765                         this.default_value = defaultValue;
 766                 }
 767
 768                 #region IParameterData Members
 769
 770                 public Expression DefaultValue {
 771                         get { return default_value; }
 772                 }
 773
 774                 public bool HasExtensionMethodModifier {
 775                         get { return (modifiers & Parameter.Modifier.This) != 0; }
 776                 }
 777
 778                 public bool HasDefaultValue {
 779                         get { return default_value != null; }
 780                 }
 781
 782                 public Parameter.Modifier ModFlags {
 783                         get { return modifiers; }
 784                 }
 785
 786                 public string Name {
 787                         get { return name; }
 788                 }
 789
 790                 #endregion
 791         }
 792
 793         public abstract class AParametersCollection
 794         {
 795                 protected bool has_arglist;
 796                 protected bool has_params;
 797
 798                 // Null object pattern
 799                 protected IParameterData [] parameters;
 800                 protected TypeSpec [] types;
 801
 802                 public CallingConventions CallingConvention {
 803                         get {
 804                                 return has_arglist ?
 805                                         CallingConventions.VarArgs :
 806                                         CallingConventions.Standard;
 807                         }
 808                 }
 809
 810                 public int Count {
 811                         get { return parameters.Length; }
 812                 }
 813
 814                 public TypeSpec ExtensionMethodType {
 815                         get {
 816                                 if (Count == 0)
 817                                         return null;
 818
 819                                 return FixedParameters [0].HasExtensionMethodModifier ?
 820                                         types [0] : null;
 821                         }
 822                 }
 823
 824                 public IParameterData [] FixedParameters {
 825                         get {
 826                                 return parameters;
 827                         }
 828                 }
 829
 830                 public static ParameterAttributes GetParameterAttribute (Parameter.Modifier modFlags)
 831                 {
 832                         return (modFlags & Parameter.Modifier.OUT) != 0 ?
 833                                 ParameterAttributes.Out : ParameterAttributes.None;
 834                 }
 835
 836                 // Very expensive operation
 837                 public MetaType[] GetMetaInfo ()
 838                 {
 839                         MetaType[] types;
 840                         if (has_arglist) {
 841                                 if (Count == 1)
 842                                         return MetaType.EmptyTypes;
 843
 844                                 types = new MetaType[Count - 1];
 845                         } else {
 846                                 if (Count == 0)
 847                                         return MetaType.EmptyTypes;
 848
 849                                 types = new MetaType[Count];
 850                         }
 851
 852                         for (int i = 0; i < types.Length; ++i) {
 853                                 types[i] = Types[i].GetMetaInfo ();
 854
 855                                 if ((FixedParameters[i].ModFlags & Parameter.Modifier.RefOutMask) == 0)
 856                                         continue;
 857
 858                                 // TODO MemberCache: Should go to MetaInfo getter
 859                                 types [i] = types [i].MakeByRefType ();
 860                         }
 861
 862                         return types;
 863                 }
 864
 865                 //
 866                 // Returns the parameter information based on the name
 867                 //
 868                 public int GetParameterIndexByName (string name)
 869                 {
 870                         for (int idx = 0; idx < Count; ++idx) {
 871                                 if (parameters [idx].Name == name)
 872                                         return idx;
 873                         }
 874
 875                         return -1;
 876                 }
 877
 878                 public string GetSignatureForDocumentation ()
 879                 {
 880                         if (IsEmpty)
 881                                 return string.Empty;
 882
 883                         StringBuilder sb = new StringBuilder ("(");
 884                         for (int i = 0; i < Count; ++i) {
 885                                 if (i != 0)
 886                                         sb.Append (",");
 887
 888                                 sb.Append (types [i].GetSignatureForDocumentation ());
 889
 890                                 if ((parameters[i].ModFlags & Parameter.Modifier.RefOutMask) != 0)
 891                                         sb.Append ("@");
 892                         }
 893                         sb.Append (")");
 894
 895                         return sb.ToString ();
 896                 }
 897
 898                 public string GetSignatureForError ()
 899                 {
 900                         return GetSignatureForError ("(", ")", Count);
 901                 }
 902
 903                 public string GetSignatureForError (string start, string end, int count)
 904                 {
 905                         StringBuilder sb = new StringBuilder (start);
 906                         for (int i = 0; i < count; ++i) {
 907                                 if (i != 0)
 908                                         sb.Append (", ");
 909                                 sb.Append (ParameterDesc (i));
 910                         }
 911                         sb.Append (end);
 912                         return sb.ToString ();
 913                 }
 914
 915                 public bool HasArglist {
 916                         get { return has_arglist; }
 917                 }
 918
 919                 public bool HasExtensionMethodType {
 920                         get {
 921                                 if (Count == 0)
 922                                         return false;
 923
 924                                 return FixedParameters [0].HasExtensionMethodModifier;
 925                         }
 926                 }
 927
 928                 public bool HasParams {
 929                         get { return has_params; }
 930                 }
 931
 932                 public bool IsEmpty {
 933                         get { return parameters.Length == 0; }
 934                 }
 935
 936                 public AParametersCollection Inflate (TypeParameterInflator inflator)
 937                 {
 938                         TypeSpec[] inflated_types = null;
 939                         bool default_value = false;
 940
 941                         for (int i = 0; i < Count; ++i) {
 942                                 var inflated_param = inflator.Inflate (types[i]);
 943                                 if (inflated_types == null) {
 944                                         if (inflated_param == types[i])
 945                                                 continue;
 946
 947                                         default_value |= FixedParameters[i].HasDefaultValue;
 948                                         inflated_types = new TypeSpec[types.Length];
 949                                         Array.Copy (types, inflated_types, types.Length);
 950                                 } else {
 951                                         if (inflated_param == types[i])
 952                                                 continue;
 953
 954                                         default_value |= FixedParameters[i].HasDefaultValue;
 955                                 }
 956
 957                                 inflated_types[i] = inflated_param;
 958                         }
 959
 960                         if (inflated_types == null)
 961                                 return this;
 962
 963                         var clone = (AParametersCollection) MemberwiseClone ();
 964                         clone.types = inflated_types;
 965
 966                         //
 967                         // Default expression is original expression from the parameter
 968                         // declaration context which can be of nested enum in generic class type.
 969                         // In such case we end up with expression type of G<T>.E and e.g. parameter
 970                         // type of G<int>.E and conversion would fail without inflate in this
 971                         // context.
 972                         //
 973                         if (default_value) {
 974                                 clone.parameters = new IParameterData[Count];
 975                                 for (int i = 0; i < Count; ++i) {
 976                                         var fp = FixedParameters[i];
 977                                         clone.FixedParameters[i] = fp;
 978
 979                                         if (!fp.HasDefaultValue)
 980                                                 continue;
 981
 982                                         var expr = fp.DefaultValue;
 983
 984                                         if (inflated_types[i] == expr.Type)
 985                                                 continue;
 986
 987                                         var c = expr as Constant;
 988                                         if (c != null) {
 989                                                 //
 990                                                 // It may fail we are inflating before type validation is done
 991                                                 //
 992                                                 c = Constant.ExtractConstantFromValue (inflated_types[i], c.GetValue (), expr.Location);
 993                                                 if (c == null)
 994                                                         expr = new DefaultValueExpression (new TypeExpression (inflated_types[i], expr.Location), expr.Location);
 995                                                 else
 996                                                         expr = c;
 997                                         } else if (expr is DefaultValueExpression)
 998                                                 expr = new DefaultValueExpression (new TypeExpression (inflated_types[i], expr.Location), expr.Location);
 999
1000                                         clone.FixedParameters[i] = new ParameterData (fp.Name, fp.ModFlags, expr);
1001                                 }
1002                         }
1003
1004                         return clone;
1005                 }
1006
1007                 public string ParameterDesc (int pos)
1008                 {
1009                         if (types == null || types [pos] == null)
1010                                 return ((Parameter)FixedParameters [pos]).GetSignatureForError ();
1011
1012                         string type = types [pos].GetSignatureForError ();
1013                         if (FixedParameters [pos].HasExtensionMethodModifier)
1014                                 return "this " + type;
1015
1016                         var mod = FixedParameters[pos].ModFlags & Parameter.Modifier.ModifierMask;
1017                         if (mod == 0)
1018                                 return type;
1019
1020                         return Parameter.GetModifierSignature (mod) + " " + type;
1021                 }
1022
1023                 public TypeSpec[] Types {
1024                         get { return types; }
1025                         set { types = value; }
1026                 }
1027         }
1028
1029         //
1030         // A collection of imported or resolved parameters
1031         //
1032         public class ParametersImported : AParametersCollection
1033         {
1034                 public ParametersImported (IParameterData [] parameters, TypeSpec [] types, bool hasArglist, bool hasParams)
1035                 {
1036                         this.parameters = parameters;
1037                         this.types = types;
1038                         this.has_arglist = hasArglist;
1039                         this.has_params = hasParams;
1040                 }
1041
1042                 public ParametersImported (IParameterData[] param, TypeSpec[] types, bool hasParams)
1043                 {
1044                         this.parameters = param;
1045                         this.types = types;
1046                         this.has_params = hasParams;
1047                 }
1048         }
1049
1050         /// <summary>
1051         ///   Represents the methods parameters
1052         /// </summary>
1053         public class ParametersCompiled : AParametersCollection
1054         {
1055                 public static readonly ParametersCompiled EmptyReadOnlyParameters = new ParametersCompiled ();
1056
1057                 // Used by C# 2.0 delegates
1058                 public static readonly ParametersCompiled Undefined = new ParametersCompiled ();
1059
1060                 private ParametersCompiled ()
1061                 {
1062                         parameters = new Parameter [0];
1063                         types = TypeSpec.EmptyTypes;
1064                 }
1065
1066                 private ParametersCompiled (IParameterData[] parameters, TypeSpec[] types)
1067                 {
1068                         this.parameters = parameters;
1069                     this.types = types;
1070                 }
1071
1072                 public ParametersCompiled (params Parameter[] parameters)
1073                 {
1074                         if (parameters == null || parameters.Length == 0)
1075                                 throw new ArgumentException ("Use EmptyReadOnlyParameters");
1076
1077                         this.parameters = parameters;
1078                         int count = parameters.Length;
1079
1080                         for (int i = 0; i < count; i++){
1081                                 has_params |= (parameters [i].ModFlags & Parameter.Modifier.PARAMS) != 0;
1082                         }
1083                 }
1084
1085                 public ParametersCompiled (Parameter [] parameters, bool has_arglist) :
1086                         this (parameters)
1087                 {
1088                         this.has_arglist = has_arglist;
1089                 }
1090
1091                 public static ParametersCompiled CreateFullyResolved (Parameter p, TypeSpec type)
1092                 {
1093                         return new ParametersCompiled (new Parameter [] { p }, new TypeSpec [] { type });
1094                 }
1095
1096                 public static ParametersCompiled CreateFullyResolved (Parameter[] parameters, TypeSpec[] types)
1097                 {
1098                         return new ParametersCompiled (parameters, types);
1099                 }
1100
1101                 //
1102                 // TODO: This does not fit here, it should go to different version of AParametersCollection
1103                 // as the underlying type is not Parameter and some methods will fail to cast
1104                 //
1105                 public static AParametersCollection CreateFullyResolved (params TypeSpec[] types)
1106                 {
1107                         var pd = new ParameterData [types.Length];
1108                         for (int i = 0; i < pd.Length; ++i)
1109                                 pd[i] = new ParameterData (null, Parameter.Modifier.NONE, null);
1110
1111                         return new ParametersCompiled (pd, types);
1112                 }
1113
1114                 public static ParametersCompiled CreateImplicitParameter (FullNamedExpression texpr, Location loc)
1115                 {
1116                         return new ParametersCompiled (
1117                                 new[] { new Parameter (texpr, "value", Parameter.Modifier.NONE, null, loc) },
1118                                 null);
1119                 }
1120
1121                 public void CheckConstraints (IMemberContext mc)
1122                 {
1123                         foreach (Parameter p in parameters) {
1124                                 //
1125                                 // It's null for compiler generated types or special types like __arglist
1126                                 //
1127                                 if (p.TypeExpression != null)
1128                                         ConstraintChecker.Check (mc, p.Type, p.TypeExpression.Location);
1129                         }
1130                 }
1131
1132                 //
1133                 // Returns non-zero value for equal CLS parameter signatures
1134                 //
1135                 public static int IsSameClsSignature (AParametersCollection a, AParametersCollection b)
1136                 {
1137                         int res = 0;
1138
1139                         for (int i = 0; i < a.Count; ++i) {
1140                                 var a_type = a.Types[i];
1141                                 var b_type = b.Types[i];
1142                                 if (TypeSpecComparer.Override.IsEqual (a_type, b_type)) {
1143                                         if ((a.FixedParameters[i].ModFlags & Parameter.Modifier.RefOutMask) != (b.FixedParameters[i].ModFlags & Parameter.Modifier.RefOutMask))
1144                                                 res |= 1;
1145
1146                                         continue;
1147                                 }
1148
1149                                 var ac_a = a_type as ArrayContainer;
1150                                 if (ac_a == null)
1151                                         return 0;
1152
1153                                 var ac_b = b_type as ArrayContainer;
1154                                 if (ac_b == null)
1155                                         return 0;
1156
1157                                 if (ac_a.Element is ArrayContainer || ac_b.Element is ArrayContainer) {
1158                                         res |= 2;
1159                                         continue;
1160                                 }
1161
1162                                 if (ac_a.Rank != ac_b.Rank && TypeSpecComparer.Override.IsEqual (ac_a.Element, ac_b.Element)) {
1163                                         res |= 1;
1164                                         continue;
1165                                 }
1166
1167                                 return 0;
1168                         }
1169
1170                         return res;
1171                 }
1172
1173                 public static ParametersCompiled MergeGenerated (CompilerContext ctx, ParametersCompiled userParams, bool checkConflicts, Parameter compilerParams, TypeSpec compilerTypes)
1174                 {
1175                         return MergeGenerated (ctx, userParams, checkConflicts,
1176                                 new Parameter [] { compilerParams },
1177                                 new TypeSpec [] { compilerTypes });
1178                 }
1179
1180                 //
1181                 // Use this method when you merge compiler generated parameters with user parameters
1182                 //
1183                 public static ParametersCompiled MergeGenerated (CompilerContext ctx, ParametersCompiled userParams, bool checkConflicts, Parameter[] compilerParams, TypeSpec[] compilerTypes)
1184                 {
1185                         Parameter[] all_params = new Parameter [userParams.Count + compilerParams.Length];
1186                         userParams.FixedParameters.CopyTo(all_params, 0);
1187
1188                         TypeSpec [] all_types;
1189                         if (userParams.types != null) {
1190                                 all_types = new TypeSpec [all_params.Length];
1191                                 userParams.Types.CopyTo (all_types, 0);
1192                         } else {
1193                                 all_types = null;
1194                         }
1195
1196                         int last_filled = userParams.Count;
1197                         int index = 0;
1198                         foreach (Parameter p in compilerParams) {
1199                                 for (int i = 0; i < last_filled; ++i) {
1200                                         while (p.Name == all_params [i].Name) {
1201                                                 if (checkConflicts && i < userParams.Count) {
1202                                                         ctx.Report.Error (316, userParams[i].Location,
1203                                                                 "The parameter name `{0}' conflicts with a compiler generated name", p.Name);
1204                                                 }
1205                                                 p.Name = '_' + p.Name;
1206                                         }
1207                                 }
1208                                 all_params [last_filled] = p;
1209                                 if (all_types != null)
1210                                         all_types [last_filled] = compilerTypes [index++];
1211                                 ++last_filled;
1212                         }
1213
1214                         ParametersCompiled parameters = new ParametersCompiled (all_params, all_types);
1215                         parameters.has_params = userParams.has_params;
1216                         return parameters;
1217                 }
1218
1219                 //
1220                 // Parameters checks for members which don't have a block
1221                 //
1222                 public void CheckParameters (MemberCore member)
1223                 {
1224                         for (int i = 0; i < parameters.Length; ++i) {
1225                                 var name = parameters[i].Name;
1226                                 for (int ii = i + 1; ii < parameters.Length; ++ii) {
1227                                         if (parameters[ii].Name == name)
1228                                                 this[ii].Error_DuplicateName (member.Compiler.Report);
1229                                 }
1230                         }
1231                 }
1232
1233                 public bool Resolve (IMemberContext ec)
1234                 {
1235                         if (types != null)
1236                                 return true;
1237
1238                         types = new TypeSpec [Count];
1239
1240                         bool ok = true;
1241                         Parameter p;
1242                         for (int i = 0; i < FixedParameters.Length; ++i) {
1243                                 p = this [i];
1244                                 TypeSpec t = p.Resolve (ec, i);
1245                                 if (t == null) {
1246                                         ok = false;
1247                                         continue;
1248                                 }
1249
1250                                 types [i] = t;
1251                         }
1252
1253                         return ok;
1254                 }
1255
1256                 public void ResolveDefaultValues (MemberCore m)
1257                 {
1258                         ResolveContext rc = null;
1259                         for (int i = 0; i < parameters.Length; ++i) {
1260                                 Parameter p = (Parameter) parameters [i];
1261
1262                                 //
1263                                 // Try not to enter default values resolution if there are is not any default value possible
1264                                 //
1265                                 if (p.HasDefaultValue || p.OptAttributes != null) {
1266                                         if (rc == null)
1267                                                 rc = new ResolveContext (m);
1268
1269                                         p.ResolveDefaultValue (rc);
1270                                 }
1271                         }
1272                 }
1273
1274                 // Define each type attribute (in/out/ref) and
1275                 // the argument names.
1276                 public void ApplyAttributes (IMemberContext mc, MethodBase builder)
1277                 {
1278                         if (Count == 0)
1279                                 return;
1280
1281                         MethodBuilder mb = builder as MethodBuilder;
1282                         ConstructorBuilder cb = builder as ConstructorBuilder;
1283                         var pa = mc.Module.PredefinedAttributes;
1284
1285                         for (int i = 0; i < Count; i++) {
1286                                 this [i].ApplyAttributes (mb, cb, i + 1, pa);
1287                         }
1288                 }
1289
1290                 public void VerifyClsCompliance (IMemberContext ctx)
1291                 {
1292                         foreach (Parameter p in FixedParameters)
1293                                 p.IsClsCompliant (ctx);
1294                 }
1295
1296                 public Parameter this [int pos] {
1297                         get { return (Parameter) parameters [pos]; }
1298                 }
1299
1300                 public Expression CreateExpressionTree (BlockContext ec, Location loc)
1301                 {
1302                         var initializers = new ArrayInitializer (Count, loc);
1303                         foreach (Parameter p in FixedParameters) {
1304                                 //
1305                                 // Each parameter expression is stored to local variable
1306                                 // to save some memory when referenced later.
1307                                 //
1308                                 StatementExpression se = new StatementExpression (p.CreateExpressionTreeVariable (ec), Location.Null);
1309                                 if (se.Resolve (ec)) {
1310                                         ec.CurrentBlock.AddScopeStatement (new TemporaryVariableReference.Declarator (p.ExpressionTreeVariableReference ()));
1311                                         ec.CurrentBlock.AddScopeStatement (se);
1312                                 }
1313
1314                                 initializers.Add (p.ExpressionTreeVariableReference ());
1315                         }
1316
1317                         return new ArrayCreation (
1318                                 Parameter.ResolveParameterExpressionType (ec, loc),
1319                                 initializers, loc);
1320                 }
1321
1322                 public ParametersCompiled Clone ()
1323                 {
1324                         ParametersCompiled p = (ParametersCompiled) MemberwiseClone ();
1325
1326                         p.parameters = new IParameterData [parameters.Length];
1327                         for (int i = 0; i < Count; ++i)
1328                                 p.parameters [i] = this [i].Clone ();
1329
1330                         return p;
1331                 }
1332         }
1333
1334         //
1335         // Default parameter value expression. We need this wrapper to handle
1336         // default parameter values of folded constants (e.g. indexer parameters).
1337         // The expression is resolved only once but applied to two methods which
1338         // both share reference to this expression and we ensure that resolving
1339         // this expression always returns same instance
1340         //
1341         public class DefaultParameterValueExpression : CompositeExpression
1342         {
1343                 public DefaultParameterValueExpression (Expression expr)
1344                         : base (expr)
1345                 {
1346                 }
1347
1348                 public void Resolve (ResolveContext rc, Parameter p)
1349                 {
1350                         var expr = Resolve (rc);
1351                         if (expr == null) {
1352                                 this.expr = ErrorExpression.Instance;
1353                                 return;
1354                         }
1355
1356                         expr = Child;
1357
1358                         if (!(expr is Constant || expr is DefaultValueExpression || (expr is New && ((New) expr).IsDefaultStruct))) {
1359                                 rc.Report.Error (1736, Location,
1360                                         "The expression being assigned to optional parameter `{0}' must be a constant or default value",
1361                                         p.Name);
1362
1363                                 return;
1364                         }
1365
1366                         var parameter_type = p.Type;
1367                         if (type == parameter_type)
1368                                 return;
1369
1370                         var res = Convert.ImplicitConversionStandard (rc, expr, parameter_type, Location);
1371                         if (res != null) {
1372                                 if (parameter_type.IsNullableType && res is Nullable.Wrap) {
1373                                         Nullable.Wrap wrap = (Nullable.Wrap) res;
1374                                         res = wrap.Child;
1375                                         if (!(res is Constant)) {
1376                                                 rc.Report.Error (1770, Location,
1377                                                         "The expression being assigned to nullable optional parameter `{0}' must be default value",
1378                                                         p.Name);
1379                                                 return;
1380                                         }
1381                                 }
1382
1383                                 if (!expr.IsNull && TypeSpec.IsReferenceType (parameter_type) && parameter_type.BuiltinType != BuiltinTypeSpec.Type.String) {
1384                                         rc.Report.Error (1763, Location,
1385                                                 "Optional parameter `{0}' of type `{1}' can only be initialized with `null'",
1386                                                 p.Name, parameter_type.GetSignatureForError ());
1387
1388                                         return;
1389                                 }
1390
1391                                 this.expr = res;
1392                                 return;
1393                         }
1394
1395                         rc.Report.Error (1750, Location,
1396                                 "Optional parameter expression of type `{0}' cannot be converted to parameter type `{1}'",
1397                                 type.GetSignatureForError (), parameter_type.GetSignatureForError ());
1398
1399                         this.expr = ErrorExpression.Instance;
1400                 }
1401
1402                 public override object Accept (StructuralVisitor visitor)
1403                 {
1404                         return visitor.Visit (this);
1405                 }
1406         }
1407 }