Stop defensively copying AST structures before resolution

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 519 matching lines @@
   void internalPerform() {
     //
     // Prepare inputs.
     //
     LibrarySpecificUnit librarySpecificUnit = target;
     Source source = getRequiredSource();
     CompilationUnit unit = getRequiredInput(PARSED_UNIT_INPUT_NAME);
     //
     // Build or reuse CompilationUnitElement.
     //
-    unit = AstCloner.clone(unit);
+//    unit = AstCloner.clone(unit);
     AnalysisCache analysisCache =
         (context as InternalAnalysisContext).analysisCache;
     CompilationUnitElement element =
         analysisCache.getValue(target, COMPILATION_UNIT_ELEMENT);
     if (element == null) {
       CompilationUnitBuilder builder = new CompilationUnitBuilder();
       element = builder.buildCompilationUnit(
           source, unit, librarySpecificUnit.library);
     } else {
       new DeclarationResolver().resolve(unit, element);
@@ skipping 15 matching lines @@
   }
 
   /**
    * Return a map from the names of the inputs of this kind of task to the task
    * input descriptors describing those inputs for a task with the given
    * [target].
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     LibrarySpecificUnit unit = target;
     return <String, TaskInput>{
-      PARSED_UNIT_INPUT_NAME: PARSED_UNIT.of(unit.unit)
+      PARSED_UNIT_INPUT_NAME: PARSED_UNIT.of(unit.unit, flushOnAccess: true)
     };
   }
 
   /**
    * Create a [BuildCompilationUnitElementTask] based on the given [target] in
    * the given [context].
    */
   static BuildCompilationUnitElementTask createTask(
       AnalysisContext context, AnalysisTarget target) {
     return new BuildCompilationUnitElementTask(context, target);
@@ skipping 3517 matching lines @@
           kind == _SourceClosureKind.IMPORT_EXPORT) {
         for (ExportElement exportElement in library.exports) {
           Source exportedSource = exportElement.exportedLibrary.source;
           _newSources.add(exportedSource);
         }
       }
     }
   }
 
   @override
+  bool get flushOnAccess => false;
+
+  @override
   List<Source> get inputValue {
     return _libraries.map((LibraryElement library) => library.source).toList();
   }
 
   @override
   void currentValueNotAvailable() {
     // Nothing needs to be done.  moveNext() will simply go on to the next new
     // source.
   }
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }