mcs/mcs/eval.cs

   1 //
   2 // eval.cs: Evaluation and Hosting API for the C# compiler
   3 //
   4 // Authors:
   5 //   Miguel de Icaza (miguel@gnome.org)
   6 //   Marek Safar (marek.safar@gmail.com)
   7 //
   8 // Dual licensed under the terms of the MIT X11 or GNU GPL
   9 //
  10 // Copyright 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
  11 // Copyright 2004-2011 Novell, Inc
  12 //
  13
  14 using System;
  15 using System.Threading;
  16 using System.Collections.Generic;
  17 using System.Reflection;
  18 using System.Reflection.Emit;
  19 using System.IO;
  20 using System.Text;
  21 using System.Linq;
  22
  23 namespace Mono.CSharp
  24 {
  25
  26         /// <summary>
  27         ///   Evaluator: provides an API to evaluate C# statements and
  28         ///   expressions dynamically.
  29         /// </summary>
  30         /// <remarks>
  31         ///   This class exposes static methods to evaluate expressions in the
  32         ///   current program.
  33         ///
  34         ///   To initialize the evaluator with a number of compiler
  35         ///   options call the Init(string[]args) method with a set of
  36         ///   command line options that the compiler recognizes.
  37         ///
  38         ///   To interrupt execution of a statement, you can invoke the
  39         ///   Evaluator.Interrupt method.
  40         /// </remarks>
  41         public class Evaluator {
  42
  43                 enum ParseMode {
  44                         // Parse silently, do not output any error messages
  45                         Silent,
  46
  47                         // Report errors during parse
  48                         ReportErrors,
  49
  50                         // Auto-complete, means that the tokenizer will start producing
  51                         // GETCOMPLETIONS tokens when it reaches a certain point.
  52                         GetCompletions
  53                 }
  54
  55                 static object evaluator_lock = new object ();
  56                 static volatile bool invoking;
  57
  58                 static int count;
  59                 static Thread invoke_thread;
  60
  61                 readonly Dictionary<string, Tuple<FieldSpec, FieldInfo>> fields;
  62
  63                 Type base_class;
  64                 bool inited;
  65
  66                 readonly CompilerContext ctx;
  67                 readonly ModuleContainer module;
  68                 readonly ReflectionImporter importer;
  69
  70                 // TODO: somehow merge with module
  71                 NamespaceEntry ns;
  72
  73                 public Evaluator (CompilerSettings settings, Report report)
  74                 {
  75                         ctx = new CompilerContext (settings, report);
  76
  77                         module = new ModuleContainer (ctx);
  78                         module.Evaluator = this;
  79
  80                         // FIXME: Importer needs this assembly for internalsvisibleto
  81                         module.SetDeclaringAssembly (new AssemblyDefinitionDynamic (module, "evaluator"));
  82                         importer = new ReflectionImporter (module, ctx.BuildinTypes);
  83
  84                         InteractiveBaseClass = typeof (InteractiveBase);
  85                         fields = new Dictionary<string, Tuple<FieldSpec, FieldInfo>> ();
  86                 }
  87
  88                 void Init ()
  89                 {
  90                         var loader = new DynamicLoader (importer, ctx);
  91
  92                         CompilerCallableEntryPoint.Reset ();
  93                         RootContext.ToplevelTypes = module;
  94
  95                         //var startup_files = new List<string> ();
  96                         //foreach (CompilationUnit file in Location.SourceFiles)
  97                         //    startup_files.Add (file.Path);
  98
  99                         loader.LoadReferences (module);
 100                         ctx.BuildinTypes.CheckDefinitions (module);
 101                         module.InitializePredefinedTypes ();
 102
 103                         inited = true;
 104                 }
 105
 106                 static void Reset ()
 107                 {
 108                         CompilerCallableEntryPoint.PartialReset ();
 109
 110                         Location.AddFile (null, "{interactive}");
 111                         Location.Initialize ();
 112                 }
 113
 114                 /// <summary>
 115                 ///   If true, turns type expressions into valid expressions
 116                 ///   and calls the describe method on it
 117                 /// </summary>
 118                 public bool DescribeTypeExpressions;
 119
 120                 /// <summary>
 121                 ///   The base class for the classes that host the user generated code
 122                 /// </summary>
 123                 /// <remarks>
 124                 ///
 125                 ///   This is the base class that will host the code
 126                 ///   executed by the Evaluator.  By default
 127                 ///   this is the Mono.CSharp.InteractiveBase class
 128                 ///   which is useful for interactive use.
 129                 ///
 130                 ///   By changing this property you can control the
 131                 ///   base class and the static members that are
 132                 ///   available to your evaluated code.
 133                 /// </remarks>
 134                 public Type InteractiveBaseClass {
 135                         get {
 136                                 return base_class;
 137                         }
 138                         set {
 139                                 base_class = value;
 140
 141                                 if (value != null && typeof (InteractiveBase).IsAssignableFrom (value))
 142                                         InteractiveBase.Evaluator = this;
 143                         }
 144                 }
 145
 146                 /// <summary>
 147                 ///   Interrupts the evaluation of an expression executing in Evaluate.
 148                 /// </summary>
 149                 /// <remarks>
 150                 ///   Use this method to interrupt long-running invocations.
 151                 /// </remarks>
 152                 public void Interrupt ()
 153                 {
 154                         if (!inited || !invoking)
 155                                 return;
 156
 157                         if (invoke_thread != null)
 158                                 invoke_thread.Abort ();
 159                 }
 160
 161                 /// <summary>
 162                 ///   Compiles the input string and returns a delegate that represents the compiled code.
 163                 /// </summary>
 164                 /// <remarks>
 165                 ///
 166                 ///   Compiles the input string as a C# expression or
 167                 ///   statement, unlike the Evaluate method, the
 168                 ///   resulting delegate can be invoked multiple times
 169                 ///   without incurring in the compilation overhead.
 170                 ///
 171                 ///   If the return value of this function is null,
 172                 ///   this indicates that the parsing was complete.
 173                 ///   If the return value is a string it indicates
 174                 ///   that the input string was partial and that the
 175                 ///   invoking code should provide more code before
 176                 ///   the code can be successfully compiled.
 177                 ///
 178                 ///   If you know that you will always get full expressions or
 179                 ///   statements and do not care about partial input, you can use
 180                 ///   the other Compile overload.
 181                 ///
 182                 ///   On success, in addition to returning null, the
 183                 ///   compiled parameter will be set to the delegate
 184                 ///   that can be invoked to execute the code.
 185                 ///
 186             /// </remarks>
 187                 public string Compile (string input, out CompiledMethod compiled)
 188                 {
 189                         if (input == null || input.Length == 0){
 190                                 compiled = null;
 191                                 return null;
 192                         }
 193
 194                         lock (evaluator_lock){
 195                                 if (!inited)
 196                                         Init ();
 197                                 else
 198                                         ctx.Report.Printer.Reset ();
 199
 200                                 bool partial_input;
 201                                 CSharpParser parser = ParseString (ParseMode.Silent, input, out partial_input);
 202                                 if (parser == null){
 203                                         compiled = null;
 204                                         if (partial_input)
 205                                                 return input;
 206
 207                                         ParseString (ParseMode.ReportErrors, input, out partial_input);
 208                                         return null;
 209                                 }
 210
 211                                 Class parser_result = parser.InteractiveResult;
 212                                 compiled = CompileBlock (parser_result, parser.undo, ctx.Report);
 213                                 return null;
 214                         }
 215                 }
 216
 217                 /// <summary>
 218                 ///   Compiles the input string and returns a delegate that represents the compiled code.
 219                 /// </summary>
 220                 /// <remarks>
 221                 ///
 222                 ///   Compiles the input string as a C# expression or
 223                 ///   statement, unlike the Evaluate method, the
 224                 ///   resulting delegate can be invoked multiple times
 225                 ///   without incurring in the compilation overhead.
 226                 ///
 227                 ///   This method can only deal with fully formed input
 228                 ///   strings and does not provide a completion mechanism.
 229                 ///   If you must deal with partial input (for example for
 230                 ///   interactive use) use the other overload.
 231                 ///
 232                 ///   On success, a delegate is returned that can be used
 233                 ///   to invoke the method.
 234                 ///
 235                 /// </remarks>
 236                 public CompiledMethod Compile (string input)
 237                 {
 238                         CompiledMethod compiled;
 239
 240                         // Ignore partial inputs
 241                         if (Compile (input, out compiled) != null){
 242                                 // Error, the input was partial.
 243                                 return null;
 244                         }
 245
 246                         // Either null (on error) or the compiled method.
 247                         return compiled;
 248                 }
 249
 250                 /// <summary>
 251                 ///   Evaluates and expression or statement and returns any result values.
 252                 /// </summary>
 253                 /// <remarks>
 254                 ///   Evaluates the input string as a C# expression or
 255                 ///   statement.  If the input string is an expression
 256                 ///   the result will be stored in the result variable
 257                 ///   and the result_set variable will be set to true.
 258                 ///
 259                 ///   It is necessary to use the result/result_set
 260                 ///   pair to identify when a result was set (for
 261                 ///   example, execution of user-provided input can be
 262                 ///   an expression, a statement or others, and
 263                 ///   result_set would only be set if the input was an
 264                 ///   expression.
 265                 ///
 266                 ///   If the return value of this function is null,
 267                 ///   this indicates that the parsing was complete.
 268                 ///   If the return value is a string, it indicates
 269                 ///   that the input is partial and that the user
 270                 ///   should provide an updated string.
 271                 /// </remarks>
 272                 public string Evaluate (string input, out object result, out bool result_set)
 273                 {
 274                         CompiledMethod compiled;
 275
 276                         result_set = false;
 277                         result = null;
 278
 279                         input = Compile (input, out compiled);
 280                         if (input != null)
 281                                 return input;
 282
 283                         if (compiled == null)
 284                                 return null;
 285
 286                         //
 287                         // The code execution does not need to keep the compiler lock
 288                         //
 289                         object retval = typeof (QuitValue);
 290
 291                         try {
 292                                 invoke_thread = System.Threading.Thread.CurrentThread;
 293                                 invoking = true;
 294                                 compiled (ref retval);
 295                         } catch (ThreadAbortException e){
 296                                 Thread.ResetAbort ();
 297                                 Console.WriteLine ("Interrupted!\n{0}", e);
 298                         } finally {
 299                                 invoking = false;
 300                         }
 301
 302                         //
 303                         // We use a reference to a compiler type, in this case
 304                         // Driver as a flag to indicate that this was a statement
 305                         //
 306                         if (!ReferenceEquals (retval, typeof (QuitValue))) {
 307                                 result_set = true;
 308                                 result = retval;
 309                         }
 310
 311                         return null;
 312                 }
 313
 314                 public string [] GetCompletions (string input, out string prefix)
 315                 {
 316                         prefix = "";
 317                         if (input == null || input.Length == 0)
 318                                 return null;
 319
 320                         lock (evaluator_lock){
 321                                 if (!inited)
 322                                         Init ();
 323
 324                                 bool partial_input;
 325                                 CSharpParser parser = ParseString (ParseMode.GetCompletions, input, out partial_input);
 326                                 if (parser == null){
 327                                         if (CSharpParser.yacc_verbose_flag != 0)
 328                                                 Console.WriteLine ("DEBUG: No completions available");
 329                                         return null;
 330                                 }
 331
 332                                 Class parser_result = parser.InteractiveResult;
 333
 334 #if NET_4_0
 335                                 var access = AssemblyBuilderAccess.RunAndCollect;
 336 #else
 337                                 var access = AssemblyBuilderAccess.Run;
 338 #endif
 339                                 var a = new AssemblyDefinitionDynamic (module, "completions");
 340                                 a.Create (AppDomain.CurrentDomain, access);
 341                                 module.SetDeclaringAssembly (a);
 342
 343                                 // Need to setup MemberCache
 344                                 parser_result.CreateType ();
 345
 346                                 var method = parser_result.Methods[0] as Method;
 347                                 BlockContext bc = new BlockContext (method, method.Block, TypeManager.void_type);
 348
 349                                 try {
 350                                         method.Block.Resolve (null, bc, method);
 351                                 } catch (CompletionResult cr) {
 352                                         prefix = cr.BaseText;
 353                                         return cr.Result;
 354                                 }
 355                         }
 356                         return null;
 357                 }
 358
 359                 /// <summary>
 360                 ///   Executes the given expression or statement.
 361                 /// </summary>
 362                 /// <remarks>
 363                 ///    Executes the provided statement, returns true
 364                 ///    on success, false on parsing errors.  Exceptions
 365                 ///    might be thrown by the called code.
 366                 /// </remarks>
 367                 public bool Run (string statement)
 368                 {
 369                         object result;
 370                         bool result_set;
 371
 372                         return Evaluate (statement, out result, out result_set) == null;
 373                 }
 374
 375                 /// <summary>
 376                 ///   Evaluates and expression or statement and returns the result.
 377                 /// </summary>
 378                 /// <remarks>
 379                 ///   Evaluates the input string as a C# expression or
 380                 ///   statement and returns the value.
 381                 ///
 382                 ///   This method will throw an exception if there is a syntax error,
 383                 ///   of if the provided input is not an expression but a statement.
 384                 /// </remarks>
 385                 public object Evaluate (string input)
 386                 {
 387                         object result;
 388                         bool result_set;
 389
 390                         string r = Evaluate (input, out result, out result_set);
 391
 392                         if (r != null)
 393                                 throw new ArgumentException ("Syntax error on input: partial input");
 394
 395                         if (result_set == false)
 396                                 throw new ArgumentException ("The expression did not set a result");
 397
 398                         return result;
 399                 }
 400
 401                 enum InputKind {
 402                         EOF,
 403                         StatementOrExpression,
 404                         CompilationUnit,
 405                         Error
 406                 }
 407
 408                 //
 409                 // Deambiguates the input string to determine if we
 410                 // want to process a statement or if we want to
 411                 // process a compilation unit.
 412                 //
 413                 // This is done using a top-down predictive parser,
 414                 // since the yacc/jay parser can not deambiguage this
 415                 // without more than one lookahead token.   There are very
 416                 // few ambiguities.
 417                 //
 418                 InputKind ToplevelOrStatement (SeekableStreamReader seekable)
 419                 {
 420                         Tokenizer tokenizer = new Tokenizer (seekable, (CompilationUnit) Location.SourceFiles [0], ctx);
 421
 422                         int t = tokenizer.token ();
 423                         switch (t){
 424                         case Token.EOF:
 425                                 return InputKind.EOF;
 426
 427                         // These are toplevels
 428                         case Token.EXTERN:
 429                         case Token.OPEN_BRACKET:
 430                         case Token.ABSTRACT:
 431                         case Token.CLASS:
 432                         case Token.ENUM:
 433                         case Token.INTERFACE:
 434                         case Token.INTERNAL:
 435                         case Token.NAMESPACE:
 436                         case Token.PRIVATE:
 437                         case Token.PROTECTED:
 438                         case Token.PUBLIC:
 439                         case Token.SEALED:
 440                         case Token.STATIC:
 441                         case Token.STRUCT:
 442                                 return InputKind.CompilationUnit;
 443
 444                         // Definitely expression
 445                         case Token.FIXED:
 446                         case Token.BOOL:
 447                         case Token.BYTE:
 448                         case Token.CHAR:
 449                         case Token.DECIMAL:
 450                         case Token.DOUBLE:
 451                         case Token.FLOAT:
 452                         case Token.INT:
 453                         case Token.LONG:
 454                         case Token.NEW:
 455                         case Token.OBJECT:
 456                         case Token.SBYTE:
 457                         case Token.SHORT:
 458                         case Token.STRING:
 459                         case Token.UINT:
 460                         case Token.ULONG:
 461                                 return InputKind.StatementOrExpression;
 462
 463                         // These need deambiguation help
 464                         case Token.USING:
 465                                 t = tokenizer.token ();
 466                                 if (t == Token.EOF)
 467                                         return InputKind.EOF;
 468
 469                                 if (t == Token.IDENTIFIER)
 470                                         return InputKind.CompilationUnit;
 471                                 return InputKind.StatementOrExpression;
 472
 473
 474                         // Distinguish between:
 475                         //    delegate opt_anonymous_method_signature block
 476                         //    delegate type
 477                         case Token.DELEGATE:
 478                                 t = tokenizer.token ();
 479                                 if (t == Token.EOF)
 480                                         return InputKind.EOF;
 481                                 if (t == Token.OPEN_PARENS || t == Token.OPEN_BRACE)
 482                                         return InputKind.StatementOrExpression;
 483                                 return InputKind.CompilationUnit;
 484
 485                         // Distinguih between:
 486                         //    unsafe block
 487                         //    unsafe as modifier of a type declaration
 488                         case Token.UNSAFE:
 489                                 t = tokenizer.token ();
 490                                 if (t == Token.EOF)
 491                                         return InputKind.EOF;
 492                                 if (t == Token.OPEN_PARENS)
 493                                         return InputKind.StatementOrExpression;
 494                                 return InputKind.CompilationUnit;
 495
 496                         // These are errors: we list explicitly what we had
 497                         // from the grammar, ERROR and then everything else
 498
 499                         case Token.READONLY:
 500                         case Token.OVERRIDE:
 501                         case Token.ERROR:
 502                                 return InputKind.Error;
 503
 504                         // This catches everything else allowed by
 505                         // expressions.  We could add one-by-one use cases
 506                         // if needed.
 507                         default:
 508                                 return InputKind.StatementOrExpression;
 509                         }
 510                 }
 511
 512                 //
 513                 // Parses the string @input and returns a CSharpParser if succeeful.
 514                 //
 515                 // if @silent is set to true then no errors are
 516                 // reported to the user.  This is used to do various calls to the
 517                 // parser and check if the expression is parsable.
 518                 //
 519                 // @partial_input: if @silent is true, then it returns whether the
 520                 // parsed expression was partial, and more data is needed
 521                 //
 522                 CSharpParser ParseString (ParseMode mode, string input, out bool partial_input)
 523                 {
 524                         partial_input = false;
 525                         Reset ();
 526                         Tokenizer.LocatedToken.Initialize ();
 527
 528                         Stream s = new MemoryStream (Encoding.Default.GetBytes (input));
 529                         SeekableStreamReader seekable = new SeekableStreamReader (s, Encoding.Default);
 530
 531                         InputKind kind = ToplevelOrStatement (seekable);
 532                         if (kind == InputKind.Error){
 533                                 if (mode == ParseMode.ReportErrors)
 534                                         ctx.Report.Error (-25, "Detection Parsing Error");
 535                                 partial_input = false;
 536                                 return null;
 537                         }
 538
 539                         if (kind == InputKind.EOF){
 540                                 if (mode == ParseMode.ReportErrors)
 541                                         Console.Error.WriteLine ("Internal error: EOF condition should have been detected in a previous call with silent=true");
 542                                 partial_input = true;
 543                                 return null;
 544
 545                         }
 546                         seekable.Position = 0;
 547
 548                         if (ns == null)
 549                                 ns = new NamespaceEntry (module, null, Location.SourceFiles[0], null);
 550
 551                         CSharpParser parser = new CSharpParser (seekable, Location.SourceFiles [0], module, ns);
 552
 553                         if (kind == InputKind.StatementOrExpression){
 554                                 parser.Lexer.putback_char = Tokenizer.EvalStatementParserCharacter;
 555                                 ctx.Settings.StatementMode = true;
 556                         } else {
 557                                 parser.Lexer.putback_char = Tokenizer.EvalCompilationUnitParserCharacter;
 558                                 ctx.Settings.StatementMode = false;
 559                         }
 560
 561                         if (mode == ParseMode.GetCompletions)
 562                                 parser.Lexer.CompleteOnEOF = true;
 563
 564                         ReportPrinter old_printer = null;
 565                         if ((mode == ParseMode.Silent || mode == ParseMode.GetCompletions) && CSharpParser.yacc_verbose_flag == 0)
 566                                 old_printer = ctx.Report.SetPrinter (new StreamReportPrinter (TextWriter.Null));
 567
 568                         try {
 569                                 parser.parse ();
 570                         } finally {
 571                                 if (ctx.Report.Errors != 0){
 572                                         if (mode != ParseMode.ReportErrors  && parser.UnexpectedEOF)
 573                                                 partial_input = true;
 574
 575                                         if (parser.undo != null)
 576                                                 parser.undo.ExecuteUndo ();
 577
 578                                         parser = null;
 579                                 }
 580
 581                                 if (old_printer != null)
 582                                         ctx.Report.SetPrinter (old_printer);
 583                         }
 584                         return parser;
 585                 }
 586
 587                 CompiledMethod CompileBlock (Class host, Undo undo, Report Report)
 588                 {
 589                         string current_debug_name = "eval-" + count + ".dll";
 590                         ++count;
 591 #if STATIC
 592                         throw new NotSupportedException ();
 593 #else
 594                         AssemblyDefinitionDynamic assembly;
 595                         AssemblyBuilderAccess access;
 596
 597                         if (Environment.GetEnvironmentVariable ("SAVE") != null) {
 598                                 access = AssemblyBuilderAccess.RunAndSave;
 599                                 assembly = new AssemblyDefinitionDynamic (module, current_debug_name, current_debug_name);
 600                                 assembly.Importer = importer;
 601                         } else {
 602 #if NET_4_0
 603                                 access = AssemblyBuilderAccess.RunAndCollect;
 604 #else
 605                                 access = AssemblyBuilderAccess.Run;
 606 #endif
 607                                 assembly = new AssemblyDefinitionDynamic (module, current_debug_name);
 608                         }
 609
 610                         assembly.Create (AppDomain.CurrentDomain, access);
 611
 612                         Method expression_method;
 613                         if (host != null) {
 614                                 var base_class_imported = importer.ImportType (base_class);
 615                                 var baseclass_list = new List<FullNamedExpression> (1) {
 616                                         new TypeExpression (base_class_imported, host.Location)
 617                                 };
 618
 619                                 host.AddBasesForPart (host, baseclass_list);
 620
 621                                 host.CreateType ();
 622                                 host.DefineType ();
 623                                 host.Define ();
 624
 625                                 expression_method = (Method) host.Methods[0];
 626                         } else {
 627                                 expression_method = null;
 628                         }
 629
 630                         module.CreateType ();
 631                         module.Define ();
 632
 633                         if (Report.Errors != 0){
 634                                 if (undo != null)
 635                                         undo.ExecuteUndo ();
 636
 637                                 return null;
 638                         }
 639
 640                         if (host != null){
 641                                 host.EmitType ();
 642                         }
 643
 644                         module.Emit ();
 645                         if (Report.Errors != 0){
 646                                 if (undo != null)
 647                                         undo.ExecuteUndo ();
 648                                 return null;
 649                         }
 650
 651                         module.CloseType ();
 652                         if (host != null)
 653                                 host.CloseType ();
 654
 655                         if (access == AssemblyBuilderAccess.RunAndSave)
 656                                 assembly.Save ();
 657
 658                         if (host == null)
 659                                 return null;
 660
 661                         //
 662                         // Unlike Mono, .NET requires that the MethodInfo is fetched, it cant
 663                         // work from MethodBuilders.   Retarded, I know.
 664                         //
 665                         var tt = assembly.Builder.GetType (host.TypeBuilder.Name);
 666                         var mi = tt.GetMethod (expression_method.Name);
 667
 668                         if (host.Fields != null) {
 669                                 //
 670                                 // We need to then go from FieldBuilder to FieldInfo
 671                                 // or reflection gets confused (it basically gets confused, and variables override each
 672                                 // other).
 673                                 //
 674                                 foreach (Field field in host.Fields) {
 675                                         var fi = tt.GetField (field.Name);
 676
 677                                         Tuple<FieldSpec, FieldInfo> old;
 678
 679                                         // If a previous value was set, nullify it, so that we do
 680                                         // not leak memory
 681                                         if (fields.TryGetValue (field.Name, out old)) {
 682                                                 if (old.Item1.MemberType.IsStruct) {
 683                                                         //
 684                                                         // TODO: Clear fields for structs
 685                                                         //
 686                                                 } else {
 687                                                         try {
 688                                                                 old.Item2.SetValue (null, null);
 689                                                         } catch {
 690                                                         }
 691                                                 }
 692                                         }
 693
 694                                         fields[field.Name] = Tuple.Create (field.Spec, fi);
 695                                 }
 696                         }
 697
 698                         return (CompiledMethod) System.Delegate.CreateDelegate (typeof (CompiledMethod), mi);
 699 #endif
 700                 }
 701
 702                 /// <summary>
 703                 ///   A sentinel value used to indicate that no value was
 704                 ///   was set by the compiled function.   This is used to
 705                 ///   differentiate between a function not returning a
 706                 ///   value and null.
 707                 /// </summary>
 708                 internal static class QuitValue { }
 709
 710                 internal Tuple<FieldSpec, FieldInfo> LookupField (string name)
 711                 {
 712                         Tuple<FieldSpec, FieldInfo> fi;
 713                         fields.TryGetValue (name, out fi);
 714                         return fi;
 715                 }
 716
 717                 static string Quote (string s)
 718                 {
 719                         if (s.IndexOf ('"') != -1)
 720                                 s = s.Replace ("\"", "\\\"");
 721
 722                         return "\"" + s + "\"";
 723                 }
 724
 725                 public string GetUsing ()
 726                 {
 727                         if (ns == null)
 728                                 return null;
 729
 730                         StringBuilder sb = new StringBuilder ();
 731                         // TODO:
 732                         //foreach (object x in ns.using_alias_list)
 733                         //    sb.AppendFormat ("using {0};\n", x);
 734
 735                         foreach (var ue in ns.Usings) {
 736                                 sb.AppendFormat ("using {0};", ue.ToString ());
 737                                 sb.Append (Environment.NewLine);
 738                         }
 739
 740                         return sb.ToString ();
 741                 }
 742
 743                 internal ICollection<string> GetUsingList ()
 744                 {
 745                         var res = new List<string> ();
 746
 747                         foreach (var ue in ns.Usings)
 748                                 res.Add (ue.ToString ());
 749                         return res;
 750                 }
 751
 752                 internal string [] GetVarNames ()
 753                 {
 754                         lock (evaluator_lock){
 755                                 return new List<string> (fields.Keys).ToArray ();
 756                         }
 757                 }
 758
 759                 public string GetVars ()
 760                 {
 761                         lock (evaluator_lock){
 762                                 StringBuilder sb = new StringBuilder ();
 763
 764                                 foreach (var de in fields){
 765                                         var fi = LookupField (de.Key);
 766                                         object value;
 767                                         try {
 768                                                 value = fi.Item2.GetValue (null);
 769                                                 if (value is string)
 770                                                         value = Quote ((string)value);
 771                                         } catch {
 772                                                 value = "<error reading value>";
 773                                         }
 774
 775                                         sb.AppendFormat ("{0} {1} = {2}", fi.Item1.MemberType.GetSignatureForError (), de.Key, value);
 776                                         sb.AppendLine ();
 777                                 }
 778
 779                                 return sb.ToString ();
 780                         }
 781                 }
 782
 783                 /// <summary>
 784                 ///    Loads the given assembly and exposes the API to the user.
 785                 /// </summary>
 786                 public void LoadAssembly (string file)
 787                 {
 788                         var loader = new DynamicLoader (importer, ctx);
 789                         var assembly = loader.LoadAssemblyFile (file);
 790                         if (assembly == null)
 791                                 return;
 792
 793                         lock (evaluator_lock){
 794                                 importer.ImportAssembly (assembly, module.GlobalRootNamespace);
 795                         }
 796                 }
 797
 798                 /// <summary>
 799                 ///    Exposes the API of the given assembly to the Evaluator
 800                 /// </summary>
 801                 public void ReferenceAssembly (Assembly a)
 802                 {
 803                         lock (evaluator_lock){
 804                                 importer.ImportAssembly (a, module.GlobalRootNamespace);
 805                         }
 806                 }
 807         }
 808
 809
 810         /// <summary>
 811         ///   A delegate that can be used to invoke the
 812         ///   compiled expression or statement.
 813         /// </summary>
 814         /// <remarks>
 815         ///   Since the Compile methods will compile
 816         ///   statements and expressions into the same
 817         ///   delegate, you can tell if a value was returned
 818         ///   by checking whether the returned value is of type
 819         ///   NoValueSet.
 820         /// </remarks>
 821
 822         public delegate void CompiledMethod (ref object retvalue);
 823
 824         /// <summary>
 825         ///   The default base class for every interaction line
 826         /// </summary>
 827         /// <remarks>
 828         ///   The expressions and statements behave as if they were
 829         ///   a static method of this class.   The InteractiveBase class
 830         ///   contains a number of useful methods, but can be overwritten
 831         ///   by setting the InteractiveBaseType property in the Evaluator
 832         /// </remarks>
 833         public class InteractiveBase {
 834                 /// <summary>
 835                 ///   Determines where the standard output of methods in this class will go.
 836                 /// </summary>
 837                 public static TextWriter Output = Console.Out;
 838
 839                 /// <summary>
 840                 ///   Determines where the standard error of methods in this class will go.
 841                 /// </summary>
 842                 public static TextWriter Error = Console.Error;
 843
 844                 /// <summary>
 845                 ///   The primary prompt used for interactive use.
 846                 /// </summary>
 847                 public static string Prompt             = "csharp> ";
 848
 849                 /// <summary>
 850                 ///   The secondary prompt used for interactive use (used when
 851                 ///   an expression is incomplete).
 852                 /// </summary>
 853                 public static string ContinuationPrompt = "      > ";
 854
 855                 /// <summary>
 856                 ///   Used to signal that the user has invoked the  `quit' statement.
 857                 /// </summary>
 858                 public static bool QuitRequested;
 859
 860                 public static Evaluator Evaluator;
 861
 862                 /// <summary>
 863                 ///   Shows all the variables defined so far.
 864                 /// </summary>
 865                 static public void ShowVars ()
 866                 {
 867                         Output.Write (Evaluator.GetVars ());
 868                         Output.Flush ();
 869                 }
 870
 871                 /// <summary>
 872                 ///   Displays the using statements in effect at this point.
 873                 /// </summary>
 874                 static public void ShowUsing ()
 875                 {
 876                         Output.Write (Evaluator.GetUsing ());
 877                         Output.Flush ();
 878                 }
 879
 880                 /// <summary>
 881                 ///   Times the execution of the given delegate
 882                 /// </summary>
 883                 static public TimeSpan Time (Action a)
 884                 {
 885                         DateTime start = DateTime.Now;
 886                         a ();
 887                         return DateTime.Now - start;
 888                 }
 889
 890                 /// <summary>
 891                 ///   Loads the assemblies from a package
 892                 /// </summary>
 893                 /// <remarks>
 894                 ///   Loads the assemblies from a package.   This is equivalent
 895                 ///   to passing the -pkg: command line flag to the C# compiler
 896                 ///   on the command line.
 897                 /// </remarks>
 898                 static public void LoadPackage (string pkg)
 899                 {
 900                         if (pkg == null){
 901                                 Error.WriteLine ("Invalid package specified");
 902                                 return;
 903                         }
 904
 905                         string pkgout = Driver.GetPackageFlags (pkg, null);
 906
 907                         string [] xargs = pkgout.Trim (new Char [] {' ', '\n', '\r', '\t'}).
 908                                 Split (new Char [] { ' ', '\t'});
 909
 910                         foreach (string s in xargs){
 911                                 if (s.StartsWith ("-r:") || s.StartsWith ("/r:") || s.StartsWith ("/reference:")){
 912                                         string lib = s.Substring (s.IndexOf (':')+1);
 913
 914                                         Evaluator.LoadAssembly (lib);
 915                                         continue;
 916                                 }
 917                         }
 918                 }
 919
 920                 /// <summary>
 921                 ///   Loads the assembly
 922                 /// </summary>
 923                 /// <remarks>
 924                 ///   Loads the specified assembly and makes its types
 925                 ///   available to the evaluator.  This is equivalent
 926                 ///   to passing the -pkg: command line flag to the C#
 927                 ///   compiler on the command line.
 928                 /// </remarks>
 929                 static public void LoadAssembly (string assembly)
 930                 {
 931                         Evaluator.LoadAssembly (assembly);
 932                 }
 933
 934                 static public void print (string obj)
 935                 {
 936                         Output.WriteLine (obj);
 937                 }
 938
 939                 static public void print (string fmt, params object [] args)
 940                 {
 941                         Output.WriteLine (fmt, args);
 942                 }
 943
 944                 /// <summary>
 945                 ///   Returns a list of available static methods.
 946                 /// </summary>
 947                 static public string help {
 948                         get {
 949                                 return "Static methods:\n" +
 950                                         "  Describe (object)       - Describes the object's type\n" +
 951                                         "  LoadPackage (package);  - Loads the given Package (like -pkg:FILE)\n" +
 952                                         "  LoadAssembly (assembly) - Loads the given assembly (like -r:ASSEMBLY)\n" +
 953                                         "  ShowVars ();            - Shows defined local variables.\n" +
 954                                         "  ShowUsing ();           - Show active using declarations.\n" +
 955                                         "  Prompt                  - The prompt used by the C# shell\n" +
 956                                         "  ContinuationPrompt      - The prompt for partial input\n" +
 957                                         "  Time(() -> { })         - Times the specified code\n" +
 958                                         "  print (obj)             - Shorthand for Console.WriteLine\n" +
 959                                         "  quit;                   - You'll never believe it - this quits the repl!\n" +
 960                                         "  help;                   - This help text\n";
 961                         }
 962                 }
 963
 964                 /// <summary>
 965                 ///   Indicates to the read-eval-print-loop that the interaction should be finished.
 966                 /// </summary>
 967                 static public object quit {
 968                         get {
 969                                 QuitRequested = true;
 970
 971                                 // To avoid print null at the exit
 972                                 return typeof (Evaluator.QuitValue);
 973                         }
 974                 }
 975
 976 #if !NET_2_1
 977                 /// <summary>
 978                 ///   Describes an object or a type.
 979                 /// </summary>
 980                 /// <remarks>
 981                 ///   This method will show a textual representation
 982                 ///   of the object's type.  If the object is a
 983                 ///   System.Type it renders the type directly,
 984                 ///   otherwise it renders the type returned by
 985                 ///   invoking GetType on the object.
 986                 /// </remarks>
 987                 static public string Describe (object x)
 988                 {
 989                         if (x == null)
 990                                 return "<null>";
 991
 992                         var type = x as Type ?? x.GetType ();
 993
 994                         StringWriter sw = new StringWriter ();
 995                         new Outline (type, sw, true, false, false).OutlineType ();
 996                         return sw.ToString ();
 997                 }
 998 #endif
 999         }
1000
1001         class HoistedEvaluatorVariable : HoistedVariable
1002         {
1003                 public HoistedEvaluatorVariable (Field field)
1004                         : base (null, field)
1005                 {
1006                 }
1007
1008                 public override void EmitSymbolInfo ()
1009                 {
1010                 }
1011
1012                 protected override FieldExpr GetFieldExpression (EmitContext ec)
1013                 {
1014                         return new FieldExpr (field, field.Location);
1015                 }
1016         }
1017
1018         /// <summary>
1019         ///    A class used to assign values if the source expression is not void
1020         ///
1021         ///    Used by the interactive shell to allow it to call this code to set
1022         ///    the return value for an invocation.
1023         /// </summary>
1024         class OptionalAssign : SimpleAssign {
1025                 public OptionalAssign (Expression t, Expression s, Location loc)
1026                         : base (t, s, loc)
1027                 {
1028                 }
1029
1030                 protected override Expression DoResolve (ResolveContext ec)
1031                 {
1032                         CloneContext cc = new CloneContext ();
1033                         Expression clone = source.Clone (cc);
1034
1035                         //
1036                         // A useful feature for the REPL: if we can resolve the expression
1037                         // as a type, Describe the type;
1038                         //
1039                         if (ec.Module.Evaluator.DescribeTypeExpressions){
1040                                 var old_printer = ec.Report.SetPrinter (new SessionReportPrinter ());
1041                                 try {
1042                                         clone = clone.Resolve (ec);
1043                                         if (clone == null) {
1044                                                 clone = source.Clone (cc);
1045                                                 clone = clone.Resolve (ec, ResolveFlags.Type);
1046                                                 if (clone == null) {
1047                                                         clone = source.Clone (cc);
1048                                                         clone = clone.Resolve (ec);
1049                                                         return null;
1050                                                 }
1051
1052                                                 Arguments args = new Arguments (1);
1053                                                 args.Add (new Argument (new TypeOf ((TypeExpr) clone, Location)));
1054                                                 source = new Invocation (new SimpleName ("Describe", Location), args).Resolve (ec);
1055                                         }
1056                                 } finally {
1057                                         ec.Report.SetPrinter (old_printer);
1058                                 }
1059                         } else {
1060                                 clone = clone.Resolve (ec);
1061                                 if (clone == null)
1062                                         return null;
1063                         }
1064
1065                         // This means its really a statement.
1066                         if (clone.Type == TypeManager.void_type || clone is DynamicInvocation || clone is Assign) {
1067                                 return clone;
1068                         }
1069
1070                         return base.DoResolve (ec);
1071                 }
1072         }
1073
1074         public class Undo
1075         {
1076                 List<Action> undo_actions;
1077
1078                 public Undo ()
1079                 {
1080                 }
1081
1082                 public void AddTypeContainer (TypeContainer current_container, TypeContainer tc)
1083                 {
1084                         if (current_container == tc){
1085                                 Console.Error.WriteLine ("Internal error: inserting container into itself");
1086                                 return;
1087                         }
1088
1089                         if (undo_actions == null)
1090                                 undo_actions = new List<Action> ();
1091
1092                         var existing = current_container.Types.FirstOrDefault (l => l.MemberName.Basename == tc.MemberName.Basename);
1093                         if (existing != null) {
1094                                 current_container.RemoveTypeContainer (existing);
1095                                 undo_actions.Add (() => current_container.AddTypeContainer (existing));
1096                         }
1097
1098                         undo_actions.Add (() => current_container.RemoveTypeContainer (tc));
1099                 }
1100
1101                 public void ExecuteUndo ()
1102                 {
1103                         if (undo_actions == null)
1104                                 return;
1105
1106                         foreach (var p in undo_actions){
1107                                 p ();
1108                         }
1109
1110                         undo_actions = null;
1111                 }
1112         }
1113
1114 }