mcs/linq.cs

   1 //
   2 // linq.cs: support for query expressions
   3 //
   4 // Authors: Marek Safar (marek.safar@gmail.com)
   5 //
   6 // Dual licensed under the terms of the MIT X11 or GNU GPL
   7 //
   8 // Copyright 2007-2008 Novell, Inc
   9 //
  10
  11 using System;
  12 using System.Reflection;
  13 using System.Collections;
  14
  15 namespace Mono.CSharp.Linq
  16 {
  17         // NOTES:
  18         // Expression should be IExpression to save some memory and make a few things
  19         // easier to read
  20         //
  21         //
  22
  23         public class QueryExpression : AQueryClause
  24         {
  25                 LocatedToken variable;
  26
  27                 public QueryExpression (LocatedToken variable, AQueryClause query)
  28                         : base (null, query.Location)
  29                 {
  30                         this.variable = variable;
  31                         this.next = query;
  32                 }
  33
  34                 public override Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parentParameter, TransparentIdentifiersScope ti)
  35                 {
  36                         Parameter p = CreateBlockParameter (variable);
  37                         return next.BuildQueryClause (ec, lSide, p, ti);
  38                 }
  39
  40                 public override Expression DoResolve (EmitContext ec)
  41                 {
  42                         int counter = TransparentParameter.Counter;
  43
  44                         Expression e = BuildQueryClause (ec, null, null, null);
  45                         e = e.Resolve (ec);
  46
  47                         //
  48                         // Reset counter in probing mode to ensure that all transparent
  49                         // identifier anonymous types are created only once
  50                         //
  51                         if (ec.IsInProbingMode)
  52                                 TransparentParameter.Counter = counter;
  53
  54                         return e;
  55                 }
  56
  57                 protected override string MethodName {
  58                         get { throw new NotSupportedException (); }
  59                 }
  60         }
  61
  62         public abstract class AQueryClause : Expression
  63         {
  64                 class QueryExpressionAccess : MemberAccess
  65                 {
  66                         public QueryExpressionAccess (Expression expr, string methodName, Location loc)
  67                                 : base (expr, methodName, loc)
  68                         {
  69                         }
  70
  71                         public QueryExpressionAccess (Expression expr, string methodName, TypeArguments typeArguments, Location loc)
  72                                 : base (expr, methodName, typeArguments, loc)
  73                         {
  74                         }
  75
  76                         protected override Expression Error_MemberLookupFailed (Type container_type, Type qualifier_type,
  77                                 Type queried_type, string name, string class_name, MemberTypes mt, BindingFlags bf)
  78                         {
  79                                 Report.Error (1935, loc, "An implementation of `{0}' query expression pattern could not be found. " +
  80                                         "Are you missing `System.Linq' using directive or `System.Core.dll' assembly reference?",
  81                                         name);
  82                                 return null;
  83                         }
  84                 }
  85
  86                 class QueryExpressionInvocation : Invocation, MethodGroupExpr.IErrorHandler
  87                 {
  88                         public QueryExpressionInvocation (QueryExpressionAccess expr, ArrayList arguments)
  89                                 : base (expr, arguments)
  90                         {
  91                         }
  92
  93                         protected override MethodGroupExpr DoResolveOverload (EmitContext ec)
  94                         {
  95                                 mg.CustomErrorHandler = this;
  96                                 MethodGroupExpr rmg = mg.OverloadResolve (ec, ref Arguments, false, loc);
  97                                 return rmg;
  98                         }
  99
 100                         public bool NoExactMatch (EmitContext ec, MethodBase method)
 101                         {
 102 #if GMCS_SOURCE
 103                                 AParametersCollection pd = TypeManager.GetParameterData (method);
 104                                 Type source_type = pd.ExtensionMethodType;
 105                                 if (source_type != null) {
 106                                         Argument a = (Argument) Arguments [0];
 107
 108                                         if (source_type.IsGenericType && source_type.ContainsGenericParameters) {
 109                                                 TypeInferenceContext tic = new TypeInferenceContext (source_type.GetGenericArguments ());
 110                                                 tic.OutputTypeInference (ec, a.Expr, source_type);
 111                                                 if (tic.FixAllTypes ()) {
 112                                                         source_type = source_type.GetGenericTypeDefinition ().MakeGenericType (tic.InferredTypeArguments);
 113                                                 }
 114                                         }
 115
 116                                         if (!Convert.ImplicitConversionExists (ec, a.Expr, source_type)) {
 117                                                 Report.Error (1936, loc, "An implementation of `{0}' query expression pattern for source type `{1}' could not be found",
 118                                                         mg.Name, TypeManager.CSharpName (a.Type));
 119                                                 return true;
 120                                         }
 121                                 }
 122
 123                                 if (!method.IsGenericMethod)
 124                                         return false;
 125
 126                                 Report.Error (1942, loc, "Type inference failed to infer type argument for `{0}' clause. " +
 127                                         "Try specifying the type argument explicitly",
 128                                         mg.Name.ToLower ());
 129                                 return true;
 130 #else
 131                                 return false;
 132 #endif
 133                         }
 134                 }
 135
 136                 public AQueryClause next;
 137                 /*protected*/ public Expression expr;
 138
 139                 protected AQueryClause (Expression expr, Location loc)
 140                 {
 141                         this.expr = expr;
 142                         this.loc = loc;
 143                 }
 144
 145                 protected override void CloneTo (CloneContext clonectx, Expression target)
 146                 {
 147                         AQueryClause t = (AQueryClause) target;
 148                         if (expr != null)
 149                                 t.expr = expr.Clone (clonectx);
 150
 151                         if (next != null)
 152                                 t.next = (AQueryClause)next.Clone (clonectx);
 153                 }
 154
 155                 public override Expression CreateExpressionTree (EmitContext ec)
 156                 {
 157                         // Should not be reached
 158                         throw new NotSupportedException ("ET");
 159                 }
 160
 161                 public override Expression DoResolve (EmitContext ec)
 162                 {
 163                         return expr.DoResolve (ec);
 164                 }
 165
 166                 public virtual Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parameter, TransparentIdentifiersScope ti)
 167                 {
 168                         ArrayList args = new ArrayList (1);
 169                         args.Add (CreateSelectorArgument (ec, expr, parameter, ti));
 170                         lSide = CreateQueryExpression (lSide, args);
 171                         if (next != null) {
 172                                 Select s = next as Select;
 173                                 if (s == null || s.IsRequired (parameter))
 174                                         return next.BuildQueryClause (ec, lSide, parameter, ti);
 175
 176                                 // Skip transparent select clause if any clause follows
 177                                 if (next.next != null)
 178                                         return next.next.BuildQueryClause (ec, lSide, parameter, ti);
 179                         }
 180
 181                         return lSide;
 182                 }
 183
 184                 protected static Parameter CreateBlockParameter (LocatedToken li)
 185                 {
 186                         return new ImplicitQueryParameter (li);
 187                 }
 188
 189                 protected Invocation CreateQueryExpression (Expression lSide, ArrayList arguments)
 190                 {
 191                         return new QueryExpressionInvocation (
 192                                 new QueryExpressionAccess (lSide, MethodName, loc), arguments);
 193                 }
 194
 195                 protected Invocation CreateQueryExpression (Expression lSide, TypeArguments typeArguments, ArrayList arguments)
 196                 {
 197                         return new QueryExpressionInvocation (
 198                                 new QueryExpressionAccess (lSide, MethodName, typeArguments, loc), arguments);
 199                 }
 200
 201                 protected Argument CreateSelectorArgument (EmitContext ec, Expression expr, Parameter parameter, TransparentIdentifiersScope ti)
 202                 {
 203                         return CreateSelectorArgument (ec, expr, new Parameter [] { parameter }, ti);
 204                 }
 205
 206                 protected Argument CreateSelectorArgument (EmitContext ec, Expression expr, Parameter[] parameters, TransparentIdentifiersScope ti)
 207                 {
 208                         Parameters p = new Parameters (parameters);
 209
 210                         LambdaExpression selector = new LambdaExpression (p, loc);
 211                         selector.Block = new SelectorBlock (ec.CurrentBlock, p, ti, loc);
 212                         selector.Block.AddStatement (new ContextualReturn (expr));
 213
 214                         return new Argument (selector);
 215                 }
 216
 217                 public override void Emit (EmitContext ec)
 218                 {
 219                         throw new NotSupportedException ();
 220                 }
 221
 222                 protected abstract string MethodName { get; }
 223
 224                 public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 225                 {
 226                         // Nothing to mutate
 227                 }
 228
 229                 public virtual AQueryClause Next {
 230                         set {
 231                                 next = value;
 232                         }
 233                 }
 234
 235                 public AQueryClause Tail {
 236                         get {
 237                                 return next == null ? this : next.Tail;
 238                         }
 239                 }
 240         }
 241
 242         //
 243         // A query clause with an identifier (range variable)
 244         //
 245         public abstract class ARangeVariableQueryClause : AQueryClause
 246         {
 247                 LocatedToken variable;
 248                 protected Expression element_selector;
 249
 250                 protected ARangeVariableQueryClause (LocatedToken variable, Expression expr, Location loc)
 251                         : base (expr, loc)
 252                 {
 253                         this.variable = variable;
 254                 }
 255
 256                 protected virtual void AddSelectorArguments (EmitContext ec, ArrayList args, Parameter parentParameter,
 257                         ref Parameter parameter, TransparentIdentifiersScope ti)
 258                 {
 259                         args.Add (CreateSelectorArgument (ec, expr, parentParameter, ti));
 260                         args.Add (CreateSelectorArgument (ec, element_selector,
 261                                 new Parameter [] { parentParameter, parameter }, ti));
 262                 }
 263
 264                 //
 265                 // Customization for range variables which not only creates a lambda expression but
 266                 // also builds a chain of range varible pairs
 267                 //
 268                 public override Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parentParameter, TransparentIdentifiersScope ti)
 269                 {
 270                         Parameter parameter = CreateBlockParameter (variable);
 271
 272                         if (next != null) {
 273                                 //
 274                                 // Builds transparent identifiers, each identifier includes its parent
 275                                 // type at index 0, and new value at index 1. This is not valid for the
 276                                 // first one which includes two values directly.
 277                                 //
 278                                 ArrayList transp_args = new ArrayList (2);
 279                                 transp_args.Add (new AnonymousTypeParameter (parentParameter));
 280                                 transp_args.Add (CreateAnonymousTypeVariable (parameter));
 281                                 element_selector = new AnonymousTypeDeclaration (transp_args, (TypeContainer) ec.TypeContainer, loc);
 282                         }
 283
 284                         ArrayList args = new ArrayList ();
 285                         AddSelectorArguments (ec, args, parentParameter, ref parameter, ti);
 286
 287                         lSide = CreateQueryExpression (lSide, args);
 288                         if (next != null) {
 289                                 //
 290                                 // Parameter identifiers go to the scope
 291                                 //
 292                                 string[] identifiers;
 293                                 if (ti == null) {
 294                                         identifiers = new string [] { parentParameter.Name, parameter.Name };
 295                                 } else {
 296                                         identifiers = new string [] { parameter.Name };
 297                                 }
 298
 299                                 TransparentParameter tp = new TransparentParameter (loc);
 300                                 return next.BuildQueryClause (ec, lSide, tp,
 301                                         new TransparentIdentifiersScope (ti, tp, identifiers));
 302                         }
 303
 304                         return lSide;
 305                 }
 306
 307                 protected override void CloneTo (CloneContext clonectx, Expression target)
 308                 {
 309                         ARangeVariableQueryClause t = (ARangeVariableQueryClause) target;
 310                         if (element_selector != null)
 311                                 t.element_selector = element_selector.Clone (clonectx);
 312                         base.CloneTo (clonectx, t);
 313                 }
 314
 315                 //
 316                 // For transparent identifiers, creates an instance of variable expression
 317                 //
 318                 protected virtual AnonymousTypeParameter CreateAnonymousTypeVariable (Parameter parameter)
 319                 {
 320                         return new AnonymousTypeParameter (parameter);
 321                 }
 322         }
 323
 324         public class QueryStartClause : AQueryClause
 325         {
 326                 public QueryStartClause (Expression expr)
 327                         : base (expr, expr.Location)
 328                 {
 329                 }
 330
 331                 public override Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parameter, TransparentIdentifiersScope ti)
 332                 {
 333                         return next.BuildQueryClause (ec, expr, parameter, ti);
 334                 }
 335
 336                 public override Expression DoResolve (EmitContext ec)
 337                 {
 338                         Expression e = BuildQueryClause (ec, null, null, null);
 339                         return e.Resolve (ec);
 340                 }
 341
 342                 protected override string MethodName {
 343                         get { throw new NotSupportedException (); }
 344                 }
 345         }
 346
 347         public class Cast : QueryStartClause
 348         {
 349                 // We don't have to clone cast type
 350                 readonly Expression type_expr;
 351
 352                 public Cast (Expression type, Expression expr)
 353                         : base (expr)
 354                 {
 355                         this.type_expr = type;
 356                 }
 357
 358                 public override Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parameter, TransparentIdentifiersScope ti)
 359                 {
 360                         lSide = CreateQueryExpression (expr, new TypeArguments (loc, type_expr), null);
 361                         if (next != null)
 362                                 return next.BuildQueryClause (ec, lSide, parameter, ti);
 363
 364                         return lSide;
 365                 }
 366
 367                 protected override string MethodName {
 368                         get { return "Cast"; }
 369                 }
 370         }
 371
 372         public class GroupBy : AQueryClause
 373         {
 374                 Expression element_selector;
 375
 376                 public GroupBy (Expression elementSelector, Expression keySelector, Location loc)
 377                         : base (keySelector, loc)
 378                 {
 379                         this.element_selector = elementSelector;
 380                 }
 381
 382                 public override Expression BuildQueryClause (EmitContext ec, Expression lSide, Parameter parameter, TransparentIdentifiersScope ti)
 383                 {
 384                         ArrayList args = new ArrayList (2);
 385                         args.Add (CreateSelectorArgument (ec, expr, parameter, ti));
 386
 387                         // A query can be optimized when selector is not group by specific
 388                         if (!element_selector.Equals (lSide))
 389                                 args.Add (CreateSelectorArgument (ec, element_selector, parameter, ti));
 390
 391                         lSide = CreateQueryExpression (lSide, args);
 392                         if (next != null)
 393                                 return next.BuildQueryClause (ec, lSide, parameter, ti);
 394
 395                         return lSide;
 396                 }
 397
 398                 protected override void CloneTo (CloneContext clonectx, Expression target)
 399                 {
 400                         GroupBy t = (GroupBy) target;
 401                         t.element_selector = element_selector.Clone (clonectx);
 402                         base.CloneTo (clonectx, t);
 403                 }
 404
 405                 protected override string MethodName {
 406                         get { return "GroupBy"; }
 407                 }
 408         }
 409
 410         public class Join : ARangeVariableQueryClause
 411         {
 412                 Expression projection;
 413                 Expression inner_selector, outer_selector;
 414
 415                 public Join (LocatedToken variable, Expression inner, Expression outerSelector, Expression innerSelector, Location loc)
 416                         : base (variable, inner, loc)
 417                 {
 418                         this.outer_selector = outerSelector;
 419                         this.inner_selector = innerSelector;
 420                 }
 421
 422                 protected override void AddSelectorArguments (EmitContext ec, ArrayList args, Parameter parentParameter,
 423                         ref Parameter parameter, TransparentIdentifiersScope ti)
 424                 {
 425                         args.Add (new Argument (expr));
 426                         args.Add (CreateSelectorArgument (ec, outer_selector, parentParameter, ti));
 427                         args.Add (CreateSelectorArgument (ec, inner_selector, parameter, ti));
 428
 429                         parameter = CreateResultSelectorParameter (parameter);
 430                         if (projection == null) {
 431                                 ArrayList join_args = new ArrayList (2);
 432                                 join_args.Add (new AnonymousTypeParameter (parentParameter));
 433                                 join_args.Add (new AnonymousTypeParameter (parameter));
 434                                 projection = new AnonymousTypeDeclaration (join_args, (TypeContainer) ec.TypeContainer, loc);
 435                         }
 436
 437                         args.Add (CreateSelectorArgument (ec, projection,
 438                                 new Parameter [] { parentParameter, parameter }, ti));
 439                 }
 440
 441                 protected override void CloneTo (CloneContext clonectx, Expression target)
 442                 {
 443                         Join t = (Join) target;
 444                         t.projection = projection.Clone (clonectx);
 445                         t.inner_selector = inner_selector.Clone (clonectx);
 446                         t.outer_selector = outer_selector.Clone (clonectx);
 447                         base.CloneTo (clonectx, t);
 448                 }
 449
 450                 protected virtual Parameter CreateResultSelectorParameter (Parameter parameter)
 451                 {
 452                         return parameter;
 453                 }
 454
 455                 public override AQueryClause Next {
 456                         set {
 457                                 // Use select as join projection
 458                                 if (value is Select) {
 459                                         projection = value.expr;
 460                                         next = value.next;
 461                                         return;
 462                                 }
 463
 464                                 base.Next = value;
 465                         }
 466                 }
 467
 468                 protected override string MethodName {
 469                         get { return "Join"; }
 470                 }
 471         }
 472
 473         public class GroupJoin : Join
 474         {
 475                 readonly LocatedToken into_variable;
 476
 477                 public GroupJoin (LocatedToken variable, Expression inner, Expression outerSelector, Expression innerSelector,
 478                         LocatedToken into, Location loc)
 479                         : base (variable, inner, outerSelector, innerSelector, loc)
 480                 {
 481                         this.into_variable = into;
 482                 }
 483
 484                 protected override Parameter CreateResultSelectorParameter (Parameter parameter)
 485                 {
 486                         //
 487                         // into variable is used as result selector and it's passed as
 488                         // transparent identifiers to the next clause
 489                         //
 490                         return CreateBlockParameter (into_variable);
 491                 }
 492
 493                 protected override string MethodName {
 494                         get { return "GroupJoin"; }
 495                 }
 496         }
 497
 498         public class Let : ARangeVariableQueryClause
 499         {
 500                 class RangeAnonymousTypeParameter : AnonymousTypeParameter
 501                 {
 502                         readonly Parameter parameter;
 503
 504                         public RangeAnonymousTypeParameter (Expression initializer, Parameter parameter)
 505                                 : base (initializer, parameter.Name, parameter.Location)
 506                         {
 507                                 this.parameter = parameter;
 508                         }
 509
 510                         public override Expression DoResolve (EmitContext ec)
 511                         {
 512                                 Expression e = base.DoResolve (ec);
 513                                 if (e != null) {
 514                                         //
 515                                         // Spread resolved initializer type
 516                                         //
 517                                         ((ImplicitLambdaParameter) parameter).Type = type;
 518                                 }
 519
 520                                 return e;
 521                         }
 522
 523                         protected override void Error_InvalidInitializer (string initializer)
 524                         {
 525                                 Report.Error (1932, loc, "A range variable `{0}' cannot be initialized with `{1}'",
 526                                         Name, initializer);
 527                         }
 528                 }
 529
 530                 public Let (LocatedToken variable, Expression expr, Location loc)
 531                         : base (variable, expr, loc)
 532                 {
 533                 }
 534
 535                 protected override void AddSelectorArguments (EmitContext ec, ArrayList args, Parameter parentParameter,
 536                         ref Parameter parameter, TransparentIdentifiersScope ti)
 537                 {
 538                         args.Add (CreateSelectorArgument (ec, element_selector, parentParameter, ti));
 539                 }
 540
 541                 protected override AnonymousTypeParameter CreateAnonymousTypeVariable (Parameter parameter)
 542                 {
 543                         return new RangeAnonymousTypeParameter (expr, parameter);
 544                 }
 545
 546                 protected override string MethodName {
 547                         get { return "Select"; }
 548                 }
 549         }
 550
 551         public class Select : AQueryClause
 552         {
 553                 public Select (Expression expr, Location loc)
 554                         : base (expr, loc)
 555                 {
 556                 }
 557
 558                 //
 559                 // For queries like `from a orderby a select a'
 560                 // the projection is transparent and select clause can be safely removed
 561                 //
 562                 public bool IsRequired (Parameter parameter)
 563                 {
 564                         SimpleName sn = expr as SimpleName;
 565                         if (sn == null)
 566                                 return true;
 567
 568                         return sn.Name != parameter.Name;
 569                 }
 570
 571                 protected override string MethodName {
 572                         get { return "Select"; }
 573                 }
 574         }
 575
 576         public class SelectMany : ARangeVariableQueryClause
 577         {
 578                 public SelectMany (LocatedToken variable, Expression expr)
 579                         : base (variable, expr, expr.Location)
 580                 {
 581                 }
 582
 583                 protected override string MethodName {
 584                         get { return "SelectMany"; }
 585                 }
 586
 587                 public override AQueryClause Next {
 588                         set {
 589                                 element_selector = value.expr;
 590
 591                                 // Can be optimized as SelectMany element selector
 592                                 if (value is Select)
 593                                         return;
 594
 595                                 next = value;
 596                         }
 597                 }
 598         }
 599
 600         public class Where : AQueryClause
 601         {
 602                 public Where (Expression expr, Location loc)
 603                         : base (expr, loc)
 604                 {
 605                 }
 606
 607                 protected override string MethodName {
 608                         get { return "Where"; }
 609                 }
 610         }
 611
 612         public class OrderByAscending : AQueryClause
 613         {
 614                 public OrderByAscending (Expression expr)
 615                         : base (expr, expr.Location)
 616                 {
 617                 }
 618
 619                 protected override string MethodName {
 620                         get { return "OrderBy"; }
 621                 }
 622         }
 623
 624         public class OrderByDescending : AQueryClause
 625         {
 626                 public OrderByDescending (Expression expr)
 627                         : base (expr, expr.Location)
 628                 {
 629                 }
 630
 631                 protected override string MethodName {
 632                         get { return "OrderByDescending"; }
 633                 }
 634         }
 635
 636         public class ThenByAscending : OrderByAscending
 637         {
 638                 public ThenByAscending (Expression expr)
 639                         : base (expr)
 640                 {
 641                 }
 642
 643                 protected override string MethodName {
 644                         get { return "ThenBy"; }
 645                 }
 646         }
 647
 648         public class ThenByDescending : OrderByDescending
 649         {
 650                 public ThenByDescending (Expression expr)
 651                         : base (expr)
 652                 {
 653                 }
 654
 655                 protected override string MethodName {
 656                         get { return "ThenByDescending"; }
 657                 }
 658         }
 659
 660         class ImplicitQueryParameter : ImplicitLambdaParameter
 661         {
 662                 public sealed class ImplicitType : Expression
 663                 {
 664                         public static ImplicitType Instance = new ImplicitType ();
 665
 666                         private ImplicitType ()
 667                         {
 668                         }
 669
 670                         protected override void CloneTo (CloneContext clonectx, Expression target)
 671                         {
 672                                 // Nothing to clone
 673                         }
 674
 675                         public override Expression CreateExpressionTree (EmitContext ec)
 676                         {
 677                                 throw new NotSupportedException ();
 678                         }
 679
 680                         public override Expression DoResolve (EmitContext ec)
 681                         {
 682                                 throw new NotSupportedException ();
 683                         }
 684
 685                         public override void Emit (EmitContext ec)
 686                         {
 687                                 throw new NotSupportedException ();
 688                         }
 689
 690                         public override void MutateHoistedGenericType (AnonymousMethodStorey storey)
 691                         {
 692                                 throw new NotSupportedException ();
 693                         }
 694                 }
 695
 696                 public ImplicitQueryParameter (LocatedToken variable)
 697                         : base (variable.Value, variable.Location)
 698                 {
 699                 }
 700         }
 701
 702         //
 703         // Transparent parameters are used to package up the intermediate results
 704         // and pass them onto next clause
 705         //
 706         public class TransparentParameter : ImplicitLambdaParameter
 707         {
 708                 public static int Counter;
 709                 const string ParameterNamePrefix = "<>__TranspIdent";
 710
 711                 public TransparentParameter (Location loc)
 712                         : base (ParameterNamePrefix + Counter++, loc)
 713                 {
 714                 }
 715         }
 716
 717         //
 718         // Transparent identifiers are stored in nested anonymous types, each type can contain
 719         // up to 2 identifiers or 1 identifier and parent type.
 720         //
 721         public class TransparentIdentifiersScope
 722         {
 723                 readonly string [] identifiers;
 724                 readonly TransparentIdentifiersScope parent;
 725                 readonly TransparentParameter parameter;
 726
 727                 public TransparentIdentifiersScope (TransparentIdentifiersScope parent,
 728                         TransparentParameter parameter, string [] identifiers)
 729                 {
 730                         this.parent = parent;
 731                         this.parameter = parameter;
 732                         this.identifiers = identifiers;
 733                 }
 734
 735                 public MemberAccess GetIdentifier (string name)
 736                 {
 737                         TransparentIdentifiersScope ident = FindIdentifier (name);
 738                         if (ident == null)
 739                                 return null;
 740
 741                         return new MemberAccess (CreateIdentifierNestingExpression (ident), name);
 742                 }
 743
 744                 TransparentIdentifiersScope FindIdentifier (string name)
 745                 {
 746                         foreach (string s in identifiers) {
 747                                 if (s == name)
 748                                         return this;
 749                         }
 750
 751                         if (parent == null)
 752                                 return null;
 753
 754                         return parent.FindIdentifier (name);
 755                 }
 756
 757                 Expression CreateIdentifierNestingExpression (TransparentIdentifiersScope end)
 758                 {
 759                         Expression expr = new SimpleName (parameter.Name, parameter.Location);
 760                         TransparentIdentifiersScope current = this;
 761                         while (current != end)
 762                         {
 763                                 current = current.parent;
 764                                 expr = new MemberAccess (expr, current.parameter.Name);
 765                         }
 766
 767                         return expr;
 768                 }
 769         }
 770
 771         //
 772         // Lambda expression block which contains transparent identifiers
 773         //
 774         class SelectorBlock : ToplevelBlock
 775         {
 776                 readonly TransparentIdentifiersScope transparent_identifiers;
 777
 778                 public SelectorBlock (Block block, Parameters parameters,
 779                         TransparentIdentifiersScope transparentIdentifiers, Location loc)
 780                         : base (block, parameters, loc)
 781                 {
 782                         this.transparent_identifiers = transparentIdentifiers;
 783                 }
 784
 785                 public override Expression GetTransparentIdentifier (string name)
 786                 {
 787                         Expression expr = null;
 788                         if (transparent_identifiers != null)
 789                                 expr = transparent_identifiers.GetIdentifier (name);
 790
 791                         if (expr != null || Container == null)
 792                                 return expr;
 793
 794                         return Container.GetTransparentIdentifier (name);
 795                 }
 796         }
 797
 798         //
 799         // This block is actually never used, it is used by parser only
 800         //
 801         public class QueryBlock : ExplicitBlock
 802         {
 803                 public QueryBlock (Block parent, Location start)
 804                         : base (parent, start, Location.Null)
 805                 {
 806                         range_variables = new System.Collections.Specialized.HybridDictionary ();
 807                 }
 808
 809                 protected override void AddVariable (LocalInfo li)
 810                 {
 811                         string name = li.Name;
 812                         if (range_variables.Contains (name)) {
 813                                 LocalInfo conflict = (LocalInfo) range_variables [name];
 814                                 Report.SymbolRelatedToPreviousError (conflict.Location, name);
 815                                 Error_AlreadyDeclared (li.Location, name);
 816                                 return;
 817                         }
 818
 819                         range_variables.Add (name, li);
 820                         Explicit.AddKnownVariable (name, li);
 821                 }
 822
 823                 protected override void Error_AlreadyDeclared (Location loc, string var, string reason)
 824                 {
 825                         Report.Error (1931, loc, "A range variable `{0}' conflicts with a previous declaration of `{0}'",
 826                                 var);
 827                 }
 828
 829                 protected override void Error_AlreadyDeclared (Location loc, string var)
 830                 {
 831                         Report.Error (1930, loc, "A range variable `{0}' has already been declared in this scope",
 832                                 var);
 833                 }
 834
 835                 protected override void Error_AlreadyDeclaredTypeParameter (Location loc, string name)
 836                 {
 837                         Report.Error (1948, loc, "A range variable `{0}' conflicts with a method type parameter",
 838                                 name);
 839                 }
 840         }
 841 }