Start working on unparse validation.

lib/compiler/implementation/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class WorkItem {
   final Element element;
   TreeElements resolutionTree;
   bool allowSpeculativeOptimization = true;
   List<HTypeGuard> guards = const <HTypeGuard>[];
 
@@ skipping 107 matching lines @@
     } finally {
       _currentElement = old;
     }
   }
 
   List<CompilerTask> tasks;
   ScannerTask scanner;
   DietParserTask dietParser;
   ParserTask parser;
   TreeValidatorTask validator;
+  UnparseValidator unparseValidator;
   ResolverTask resolver;
   TypeCheckerTask checker;
   Backend backend;
   ConstantHandler constantHandler;
   EnqueueTask enqueuer;
 
   static final SourceString MAIN = const SourceString('main');
   static final SourceString NO_SUCH_METHOD = const SourceString('noSuchMethod');
   static final SourceString NO_SUCH_METHOD_EXCEPTION =
       const SourceString('NoSuchMethodException');
   static final SourceString START_ROOT_ISOLATE =
       const SourceString('startRootIsolate');
   bool enabledNoSuchMethod = false;
 
   Stopwatch codegenProgress;
 
   Compiler([this.tracer = const Tracer(),
             this.enableTypeAssertions = false,
-            bool emitJavascript = true])
+            bool emitJavascript = true,
+            validateUnparse = false])
       : libraries = new Map<String, LibraryElement>(),
         world = new World(),
         codegenProgress = new Stopwatch.start() {
     namer = new Namer(this);
     constantHandler = new ConstantHandler(this);
     scanner = new ScannerTask(this);
     dietParser = new DietParserTask(this);
     parser = new ParserTask(this);
     validator = new TreeValidatorTask(this);
+    unparseValidator = new UnparseValidator(this, validateUnparse);
     resolver = new ResolverTask(this);
     checker = new TypeCheckerTask(this);
     backend = emitJavascript ?
         new JavaScriptBackend(this) : new DartBackend(this);
     enqueuer = new EnqueueTask(this);
     tasks = [scanner, dietParser, parser, resolver, checker,
-             constantHandler, enqueuer];
+             unparseValidator, constantHandler, enqueuer];
   }
 
   Universe get codegenWorld() => enqueuer.codegen.universe;
 
   int getNextFreeClassId() => nextFreeClassId++;
 
   void ensure(bool condition) {
     if (!condition) cancel('failed assertion in leg');
   }
 
@@ skipping 194 matching lines @@
     if (!enqueuer.codegen.queue.isEmpty()) {
       internalErrorOnElement(enqueuer.codegen.queue.first().element,
                              "work list is not empty");
     }
   }
 
   TreeElements analyzeElement(Element element) {
     assert(parser !== null);
     Node tree = parser.parse(element);
     validator.validate(tree);
+    unparseValidator.check(element);
     TreeElements elements = resolver.resolve(element);
     checker.check(tree, elements);
     return elements;
   }
 
   TreeElements analyze(WorkItem work) {
     work.resolutionTree = analyzeElement(work.element);
     return work.resolutionTree;
   }
 
@@ skipping 199 matching lines @@
   }
 }
 
 class SourceSpan {
   final Uri uri;
   final int begin;
   final int end;
 
   const SourceSpan(this.uri, this.begin, this.end);
 }