Roll Observatory packages and add a roll script

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';
-import 'package:analyzer/src/generated/constant.dart';
-import 'package:analyzer/src/generated/element.dart';
-import 'package:analyzer/src/generated/engine.dart'
-    hide AnalysisCache, AnalysisTask;
-import 'package:analyzer/src/generated/error.dart';
-import 'package:analyzer/src/generated/error_verifier.dart';
-import 'package:analyzer/src/generated/java_engine.dart';
-import 'package:analyzer/src/generated/parser.dart';
-import 'package:analyzer/src/generated/resolver.dart';
-import 'package:analyzer/src/generated/scanner.dart';
-import 'package:analyzer/src/generated/sdk.dart';
-import 'package:analyzer/src/generated/source.dart';
-import 'package:analyzer/src/task/driver.dart';
-import 'package:analyzer/src/task/general.dart';
-import 'package:analyzer/src/task/html.dart';
-import 'package:analyzer/src/task/inputs.dart';
-import 'package:analyzer/src/task/model.dart';
-import 'package:analyzer/task/dart.dart';
-import 'package:analyzer/task/general.dart';
-import 'package:analyzer/task/model.dart';
-
-/**
- * The [ResultCachingPolicy] for ASTs.
- */
-const ResultCachingPolicy AST_CACHING_POLICY =
-    const SimpleResultCachingPolicy(8192, 8192);
-
-/**
- * The errors produced while resolving a library directives.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ListResultDescriptor<AnalysisError> BUILD_DIRECTIVES_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'BUILD_DIRECTIVES_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The errors produced while building a library element.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ListResultDescriptor<AnalysisError> BUILD_LIBRARY_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'BUILD_LIBRARY_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * A list of the [ConstantEvaluationTarget]s defined in a unit.  This includes
- * constants defined at top level, statically inside classes, and local to
- * functions, as well as constant constructors, annotations, and default values
- * of parameters to constant constructors.
- */
-final ListResultDescriptor<ConstantEvaluationTarget> COMPILATION_UNIT_CONSTANTS =
-    new ListResultDescriptor<ConstantEvaluationTarget>(
-        'COMPILATION_UNIT_CONSTANTS', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The element model associated with a single compilation unit.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnitElement> COMPILATION_UNIT_ELEMENT =
-    new ResultDescriptor<CompilationUnitElement>(
-        'COMPILATION_UNIT_ELEMENT', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The list of [ConstantEvaluationTarget]s on which the target constant element
- * depends.
- *
- * The result is only available for targets representing a
- * [ConstantEvaluationTarget] (i.e. a constant variable declaration, a constant
- * constructor, or a parameter element with a default value).
- */
-final ListResultDescriptor<ConstantEvaluationTarget> CONSTANT_DEPENDENCIES =
-    new ListResultDescriptor<ConstantEvaluationTarget>(
-        'CONSTANT_DEPENDENCIES', const <ConstantEvaluationTarget>[]);
-
-/**
- * A [ConstantEvaluationTarget] that has been successfully constant-evaluated.
- *
- * TODO(paulberry): is ELEMENT_CACHING_POLICY the correct caching policy?
- */
-final ResultDescriptor<ConstantEvaluationTarget> CONSTANT_VALUE =
-    new ResultDescriptor<ConstantEvaluationTarget>('CONSTANT_VALUE', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The sources representing the libraries that include a given source as a part.
- *
- * The result is only available for [Source]s representing a compilation unit.
- */
-final ListResultDescriptor<Source> CONTAINING_LIBRARIES =
-    new ListResultDescriptor<Source>('CONTAINING_LIBRARIES', Source.EMPTY_LIST);
-
-/**
- * The [ResultCachingPolicy] for [Element]s.
- */
-const ResultCachingPolicy ELEMENT_CACHING_POLICY =
-    const SimpleResultCachingPolicy(-1, -1);
-
-/**
- * The sources representing the export closure of a library.
- * The [Source]s include only library sources, not their units.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ListResultDescriptor<Source> EXPORT_SOURCE_CLOSURE =
-    new ListResultDescriptor<Source>('EXPORT_SOURCE_CLOSURE', null);
-
-/**
- * The errors produced while generating hints a compilation unit.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> HINTS =
-    new ListResultDescriptor<AnalysisError>(
-        'HINT_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The sources representing the combined import/export closure of a library.
- * The [Source]s include only library sources, not their units.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ListResultDescriptor<Source> IMPORT_EXPORT_SOURCE_CLOSURE =
-    new ListResultDescriptor<Source>('IMPORT_EXPORT_SOURCE_CLOSURE', null);
-
-/**
- * The partial [LibraryElement] associated with a library.
- *
- * The [LibraryElement] and its [CompilationUnitElement]s are attached to each
- * other. Directives 'library', 'part' and 'part of' are resolved.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<LibraryElement> LIBRARY_ELEMENT1 =
-    new ResultDescriptor<LibraryElement>('LIBRARY_ELEMENT1', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The partial [LibraryElement] associated with a library.
- *
- * In addition to [LIBRARY_ELEMENT1] [LibraryElement.imports] and
- * [LibraryElement.exports] are set.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<LibraryElement> LIBRARY_ELEMENT2 =
-    new ResultDescriptor<LibraryElement>('LIBRARY_ELEMENT2', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The partial [LibraryElement] associated with a library.
- *
- * In addition to [LIBRARY_ELEMENT2] the [LibraryElement.publicNamespace] is set.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<LibraryElement> LIBRARY_ELEMENT3 =
-    new ResultDescriptor<LibraryElement>('LIBRARY_ELEMENT3', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The partial [LibraryElement] associated with a library.
- *
- * In addition to [LIBRARY_ELEMENT3] the [LibraryElement.entryPoint] is set,
- * if the library does not declare one already and one of the exported
- * libraries exports one.
- *
- * Also [LibraryElement.exportNamespace] is set.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<LibraryElement> LIBRARY_ELEMENT4 =
-    new ResultDescriptor<LibraryElement>('LIBRARY_ELEMENT4', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The partial [LibraryElement] associated with a library.
- *
- * [LIBRARY_ELEMENT4] plus resolved types for every element.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<LibraryElement> LIBRARY_ELEMENT5 =
-    new ResultDescriptor<LibraryElement>('LIBRARY_ELEMENT5', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The flag specifying whether all analysis errors are computed in a specific
- * library.
- *
- * The result is only available for [Source]s representing a library.
- */
-final ResultDescriptor<bool> LIBRARY_ERRORS_READY =
-    new ResultDescriptor<bool>('LIBRARY_ERRORS_READY', false);
-
-/**
- * The analysis errors associated with a compilation unit in a specific library.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> LIBRARY_UNIT_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'LIBRARY_UNIT_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The errors produced while parsing a compilation unit.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [Source]s representing a compilation unit.
- */
-final ListResultDescriptor<AnalysisError> PARSE_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'PARSE_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The names (resolved and not) referenced by a unit.
- *
- * The result is only available for [Source]s representing a compilation unit.
- */
-final ResultDescriptor<ReferencedNames> REFERENCED_NAMES =
-    new ResultDescriptor<ReferencedNames>('REFERENCED_NAMES', null);
-
-/**
- * The errors produced while resolving references.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> RESOLVE_REFERENCES_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'RESOLVE_REFERENCES_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The errors produced while resolving type names.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> RESOLVE_TYPE_NAMES_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'RESOLVE_TYPE_NAMES_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The partially resolved [CompilationUnit] associated with a unit.
- *
- * All declarations bound to the element defined by the declaration.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnit> RESOLVED_UNIT1 =
-    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT1', null,
-        cachingPolicy: AST_CACHING_POLICY);
-
-/**
- * The partially resolved [CompilationUnit] associated with a unit.
- *
- * All the enum member elements are built.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnit> RESOLVED_UNIT2 =
-    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT2', null,
-        cachingPolicy: AST_CACHING_POLICY);
-
-/**
- * The partially resolved [CompilationUnit] associated with a unit.
- *
- * [RESOLVED_UNIT2] with resolved type names.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnit> RESOLVED_UNIT3 =
-    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT3', null,
-        cachingPolicy: AST_CACHING_POLICY);
-
-/**
- * The partially resolved [CompilationUnit] associated with a unit.
- *
- * [RESOLVED_UNIT3] plus resolved local variables and formal parameters.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnit> RESOLVED_UNIT4 =
-    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT4', null,
-        cachingPolicy: AST_CACHING_POLICY);
-
-/**
- * The resolved [CompilationUnit] associated with a compilation unit, with
- * constants not yet resolved.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ResultDescriptor<CompilationUnit> RESOLVED_UNIT5 =
-    new ResultDescriptor<CompilationUnit>('RESOLVED_UNIT5', null,
-        cachingPolicy: AST_CACHING_POLICY);
-
-/**
- * The errors produced while scanning a compilation unit.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [Source]s representing a compilation unit.
- */
-final ListResultDescriptor<AnalysisError> SCAN_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'SCAN_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The [ResultCachingPolicy] for [TOKEN_STREAM].
- */
-const ResultCachingPolicy TOKEN_STREAM_CACHING_POLICY =
-    const SimpleResultCachingPolicy(1, 1);
-
-/**
- * The [TypeProvider] of the [AnalysisContext].
- */
-final ResultDescriptor<TypeProvider> TYPE_PROVIDER =
-    new ResultDescriptor<TypeProvider>('TYPE_PROVIDER', null);
-
-/**
- * The [UsedImportedElements] of a [LibrarySpecificUnit].
- */
-final ResultDescriptor<UsedImportedElements> USED_IMPORTED_ELEMENTS =
-    new ResultDescriptor<UsedImportedElements>('USED_IMPORTED_ELEMENTS', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The [UsedLocalElements] of a [LibrarySpecificUnit].
- */
-final ResultDescriptor<UsedLocalElements> USED_LOCAL_ELEMENTS =
-    new ResultDescriptor<UsedLocalElements>('USED_LOCAL_ELEMENTS', null,
-        cachingPolicy: ELEMENT_CACHING_POLICY);
-
-/**
- * The errors produced while resolving variable references in a compilation unit.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> VARIABLE_REFERENCE_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'VARIABLE_REFERENCE_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * The errors produced while verifying a compilation unit.
- *
- * The list will be empty if there were no errors, but will not be `null`.
- *
- * The result is only available for [LibrarySpecificUnit]s.
- */
-final ListResultDescriptor<AnalysisError> VERIFY_ERRORS =
-    new ListResultDescriptor<AnalysisError>(
-        'VERIFY_ERRORS', AnalysisError.NO_ERRORS);
-
-/**
- * Return a list of errors containing the errors from the given [errors] list
- * but with duplications removed.
- */
-List<AnalysisError> removeDuplicateErrors(List<AnalysisError> errors) {
-  if (errors.isEmpty) {
-    return errors;
-  }
-  return errors.toSet().toList();
-}
-
-/**
- * A task that builds a compilation unit element for a single compilation unit.
- */
-class BuildCompilationUnitElementTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the AST for the compilation unit.
-   */
-  static const String PARSED_UNIT_INPUT_NAME = 'PARSED_UNIT_INPUT_NAME';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildCompilationUnitElementTask', createTask, buildInputs,
-      <ResultDescriptor>[
-    COMPILATION_UNIT_ELEMENT,
-    RESOLVED_UNIT1,
-    COMPILATION_UNIT_CONSTANTS
-  ]);
-
-  /**
-   * Initialize a newly created task to build a compilation unit element for
-   * the given [target] in the given [context].
-   */
-  BuildCompilationUnitElementTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  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);
-    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);
-    }
-    //
-    // Prepare constants.
-    //
-    ConstantFinder constantFinder =
-        new ConstantFinder(context, source, librarySpecificUnit.library);
-    unit.accept(constantFinder);
-    List<ConstantEvaluationTarget> constants =
-        new List<ConstantEvaluationTarget>.from(
-            constantFinder.constantsToCompute);
-    //
-    // Record outputs.
-    //
-    outputs[COMPILATION_UNIT_ELEMENT] = element;
-    outputs[RESOLVED_UNIT1] = unit;
-    outputs[COMPILATION_UNIT_CONSTANTS] = constants;
-  }
-
-  /**
-   * 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)
-    };
-  }
-
-  /**
-   * Create a [BuildCompilationUnitElementTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildCompilationUnitElementTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildCompilationUnitElementTask(context, target);
-  }
-}
-
-/**
- * A task that builds imports and export directive elements for a library.
- */
-class BuildDirectiveElementsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the defining [LIBRARY_ELEMENT1].
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The name of the input for [RESOLVED_UNIT1] of a library unit.
-   */
-  static const String UNIT_INPUT_NAME = 'UNIT_INPUT_NAME';
-
-  /**
-   * The input with a list of [LIBRARY_ELEMENT3]s of imported libraries.
-   */
-  static const String IMPORTS_LIBRARY_ELEMENT_INPUT_NAME =
-      'IMPORTS_LIBRARY_ELEMENT1_INPUT_NAME';
-
-  /**
-   * The input with a list of [LIBRARY_ELEMENT3]s of exported libraries.
-   */
-  static const String EXPORTS_LIBRARY_ELEMENT_INPUT_NAME =
-      'EXPORTS_LIBRARY_ELEMENT_INPUT_NAME';
-
-  /**
-   * The input with a list of [SOURCE_KIND]s of imported libraries.
-   */
-  static const String IMPORTS_SOURCE_KIND_INPUT_NAME =
-      'IMPORTS_SOURCE_KIND_INPUT_NAME';
-
-  /**
-   * The input with a list of [SOURCE_KIND]s of exported libraries.
-   */
-  static const String EXPORTS_SOURCE_KIND_INPUT_NAME =
-      'EXPORTS_SOURCE_KIND_INPUT_NAME';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildDirectiveElementsTask', createTask, buildInputs, <ResultDescriptor>[
-    LIBRARY_ELEMENT2,
-    BUILD_DIRECTIVES_ERRORS
-  ]);
-
-  BuildDirectiveElementsTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    List<AnalysisError> errors = <AnalysisError>[];
-    //
-    // Prepare inputs.
-    //
-    LibraryElementImpl libraryElement = getRequiredInput(LIBRARY_INPUT);
-    CompilationUnit libraryUnit = getRequiredInput(UNIT_INPUT_NAME);
-    Map<Source, LibraryElement> importLibraryMap =
-        getRequiredInput(IMPORTS_LIBRARY_ELEMENT_INPUT_NAME);
-    Map<Source, LibraryElement> exportLibraryMap =
-        getRequiredInput(EXPORTS_LIBRARY_ELEMENT_INPUT_NAME);
-    Map<Source, SourceKind> importSourceKindMap =
-        getRequiredInput(IMPORTS_SOURCE_KIND_INPUT_NAME);
-    Map<Source, SourceKind> exportSourceKindMap =
-        getRequiredInput(EXPORTS_SOURCE_KIND_INPUT_NAME);
-    Source librarySource = libraryElement.source;
-    //
-    // Resolve directives.
-    //
-    HashMap<String, PrefixElementImpl> nameToPrefixMap =
-        new HashMap<String, PrefixElementImpl>();
-    List<ImportElement> imports = <ImportElement>[];
-    List<ExportElement> exports = <ExportElement>[];
-    bool explicitlyImportsCore = false;
-    for (Directive directive in libraryUnit.directives) {
-      if (directive is ImportDirective) {
-        ImportDirective importDirective = directive;
-        String uriContent = importDirective.uriContent;
-        if (DartUriResolver.isDartExtUri(uriContent)) {
-          libraryElement.hasExtUri = true;
-        }
-        Source importedSource = importDirective.source;
-        if (importedSource != null && context.exists(importedSource)) {
-          // The imported source will be null if the URI in the import
-          // directive was invalid.
-          LibraryElement importedLibrary = importLibraryMap[importedSource];
-          if (importedLibrary != null) {
-            if (importedLibrary.isDartCore) {
-              explicitlyImportsCore = true;
-            }
-            ImportElementImpl importElement =
-                new ImportElementImpl(directive.offset);
-            StringLiteral uriLiteral = importDirective.uri;
-            if (uriLiteral != null) {
-              importElement.uriOffset = uriLiteral.offset;
-              importElement.uriEnd = uriLiteral.end;
-            }
-            importElement.uri = uriContent;
-            importElement.deferred = importDirective.deferredKeyword != null;
-            importElement.combinators = _buildCombinators(importDirective);
-            importElement.importedLibrary = importedLibrary;
-            SimpleIdentifier prefixNode = directive.prefix;
-            if (prefixNode != null) {
-              importElement.prefixOffset = prefixNode.offset;
-              String prefixName = prefixNode.name;
-              PrefixElementImpl prefix = nameToPrefixMap[prefixName];
-              if (prefix == null) {
-                prefix = new PrefixElementImpl.forNode(prefixNode);
-                nameToPrefixMap[prefixName] = prefix;
-              }
-              importElement.prefix = prefix;
-              prefixNode.staticElement = prefix;
-            }
-            directive.element = importElement;
-            imports.add(importElement);
-            if (importSourceKindMap[importedSource] != SourceKind.LIBRARY) {
-              ErrorCode errorCode = (importElement.isDeferred
-                  ? StaticWarningCode.IMPORT_OF_NON_LIBRARY
-                  : CompileTimeErrorCode.IMPORT_OF_NON_LIBRARY);
-              errors.add(new AnalysisError(importedSource, uriLiteral.offset,
-                  uriLiteral.length, errorCode, [uriLiteral.toSource()]));
-            }
-          }
-        }
-      } else if (directive is ExportDirective) {
-        ExportDirective exportDirective = directive;
-        Source exportedSource = exportDirective.source;
-        if (exportedSource != null && context.exists(exportedSource)) {
-          // The exported source will be null if the URI in the export
-          // directive was invalid.
-          LibraryElement exportedLibrary = exportLibraryMap[exportedSource];
-          if (exportedLibrary != null) {
-            ExportElementImpl exportElement =
-                new ExportElementImpl(directive.offset);
-            StringLiteral uriLiteral = exportDirective.uri;
-            if (uriLiteral != null) {
-              exportElement.uriOffset = uriLiteral.offset;
-              exportElement.uriEnd = uriLiteral.end;
-            }
-            exportElement.uri = exportDirective.uriContent;
-            exportElement.combinators = _buildCombinators(exportDirective);
-            exportElement.exportedLibrary = exportedLibrary;
-            directive.element = exportElement;
-            exports.add(exportElement);
-            if (exportSourceKindMap[exportedSource] != SourceKind.LIBRARY) {
-              errors.add(new AnalysisError(exportedSource, uriLiteral.offset,
-                  uriLiteral.length, CompileTimeErrorCode.EXPORT_OF_NON_LIBRARY,
-                  [uriLiteral.toSource()]));
-            }
-          }
-        }
-      }
-    }
-    //
-    // Ensure "dart:core" import.
-    //
-    Source coreLibrarySource = context.sourceFactory.forUri(DartSdk.DART_CORE);
-    if (!explicitlyImportsCore && coreLibrarySource != librarySource) {
-      ImportElementImpl importElement = new ImportElementImpl(-1);
-      importElement.importedLibrary = importLibraryMap[coreLibrarySource];
-      importElement.synthetic = true;
-      imports.add(importElement);
-    }
-    //
-    // Populate the library element.
-    //
-    libraryElement.imports = imports;
-    libraryElement.exports = exports;
-    //
-    // Record outputs.
-    //
-    outputs[LIBRARY_ELEMENT2] = libraryElement;
-    outputs[BUILD_DIRECTIVES_ERRORS] = errors;
-  }
-
-  /**
-   * 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 library [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      LIBRARY_INPUT: LIBRARY_ELEMENT1.of(source),
-      UNIT_INPUT_NAME:
-          RESOLVED_UNIT1.of(new LibrarySpecificUnit(source, source)),
-      IMPORTS_LIBRARY_ELEMENT_INPUT_NAME:
-          IMPORTED_LIBRARIES.of(source).toMapOf(LIBRARY_ELEMENT1),
-      EXPORTS_LIBRARY_ELEMENT_INPUT_NAME:
-          EXPORTED_LIBRARIES.of(source).toMapOf(LIBRARY_ELEMENT1),
-      IMPORTS_SOURCE_KIND_INPUT_NAME:
-          IMPORTED_LIBRARIES.of(source).toMapOf(SOURCE_KIND),
-      EXPORTS_SOURCE_KIND_INPUT_NAME:
-          EXPORTED_LIBRARIES.of(source).toMapOf(SOURCE_KIND)
-    };
-  }
-
-  /**
-   * Create a [BuildDirectiveElementsTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildDirectiveElementsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildDirectiveElementsTask(context, target);
-  }
-
-  /**
-   * Build the element model representing the combinators declared by
-   * the given [directive].
-   */
-  static List<NamespaceCombinator> _buildCombinators(
-      NamespaceDirective directive) {
-    List<NamespaceCombinator> combinators = <NamespaceCombinator>[];
-    for (Combinator combinator in directive.combinators) {
-      if (combinator is ShowCombinator) {
-        ShowElementCombinatorImpl show = new ShowElementCombinatorImpl();
-        show.offset = combinator.offset;
-        show.end = combinator.end;
-        show.shownNames = _getIdentifiers(combinator.shownNames);
-        combinators.add(show);
-      } else if (combinator is HideCombinator) {
-        HideElementCombinatorImpl hide = new HideElementCombinatorImpl();
-        hide.hiddenNames = _getIdentifiers(combinator.hiddenNames);
-        combinators.add(hide);
-      }
-    }
-    return combinators;
-  }
-
-  /**
-   * Return the lexical identifiers associated with the given [identifiers].
-   */
-  static List<String> _getIdentifiers(NodeList<SimpleIdentifier> identifiers) {
-    return identifiers.map((identifier) => identifier.name).toList();
-  }
-}
-
-/**
- * A task that builds the elements representing the members of enum
- * declarations.
- */
-class BuildEnumMemberElementsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The name of the [RESOLVED_UNIT1] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildEnumMemberElementsTask', createTask, buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT2]);
-
-  BuildEnumMemberElementsTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    //
-    // Record outputs.
-    //
-    EnumMemberBuilder builder = new EnumMemberBuilder(typeProvider);
-    unit.accept(builder);
-    outputs[RESOLVED_UNIT2] = unit;
-  }
-
-  /**
-   * 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>{
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request),
-      UNIT_INPUT: RESOLVED_UNIT1.of(unit)
-    };
-  }
-
-  /**
-   * Create a [BuildEnumMemberElementsTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildEnumMemberElementsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildEnumMemberElementsTask(context, target);
-  }
-}
-
-/**
- * A task that builds [EXPORT_NAMESPACE] and [LIBRARY_ELEMENT4] for a library.
- */
-class BuildExportNamespaceTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input for [LIBRARY_ELEMENT3] of a library.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildExportNamespaceTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_ELEMENT4]);
-
-  BuildExportNamespaceTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    LibraryElementImpl library = getRequiredInput(LIBRARY_INPUT);
-    //
-    // Compute export namespace.
-    //
-    ExportNamespaceBuilder builder = new ExportNamespaceBuilder();
-    Namespace namespace = builder.build(library);
-    library.exportNamespace = namespace;
-    //
-    // Update entry point.
-    //
-    if (library.entryPoint == null) {
-      Iterable<Element> exportedElements = namespace.definedNames.values;
-      library.entryPoint = exportedElements.firstWhere(
-          (element) => element is FunctionElement && element.isEntryPoint,
-          orElse: () => null);
-    }
-    //
-    // Record outputs.
-    //
-    outputs[LIBRARY_ELEMENT4] = library;
-  }
-
-  /**
-   * 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 library [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      LIBRARY_INPUT: LIBRARY_ELEMENT3.of(source),
-      'exportsLibraryPublicNamespace':
-          EXPORT_SOURCE_CLOSURE.of(source).toMapOf(LIBRARY_ELEMENT3)
-    };
-  }
-
-  /**
-   * Create a [BuildExportNamespaceTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildExportNamespaceTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildExportNamespaceTask(context, target);
-  }
-}
-
-/**
- * A task that builds a library element for a Dart library.
- */
-class BuildLibraryElementTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the defining [RESOLVED_UNIT1].
-   */
-  static const String DEFINING_UNIT_INPUT = 'DEFINING_UNIT_INPUT';
-
-  /**
-   * The name of the input whose value is a list of built [RESOLVED_UNIT1]s
-   * of the parts sourced by a library.
-   */
-  static const String PARTS_UNIT_INPUT = 'PARTS_UNIT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildLibraryElementTask', createTask, buildInputs, <ResultDescriptor>[
-    BUILD_LIBRARY_ERRORS,
-    LIBRARY_ELEMENT1,
-    IS_LAUNCHABLE
-  ]);
-
-  /**
-   * The constant used as an unknown common library name in parts.
-   */
-  static const String _UNKNOWN_LIBRARY_NAME = 'unknown-library-name';
-
-  /**
-   * Initialize a newly created task to build a library element for the given
-   * [target] in the given [context].
-   */
-  BuildLibraryElementTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    List<AnalysisError> errors = <AnalysisError>[];
-    //
-    // Prepare inputs.
-    //
-    Source librarySource = getRequiredSource();
-    CompilationUnit definingCompilationUnit =
-        getRequiredInput(DEFINING_UNIT_INPUT);
-    List<CompilationUnit> partUnits = getRequiredInput(PARTS_UNIT_INPUT);
-    //
-    // Process inputs.
-    //
-    CompilationUnitElementImpl definingCompilationUnitElement =
-        definingCompilationUnit.element;
-    Map<Source, CompilationUnit> partUnitMap =
-        new HashMap<Source, CompilationUnit>();
-    for (CompilationUnit partUnit in partUnits) {
-      Source partSource = partUnit.element.source;
-      partUnitMap[partSource] = partUnit;
-    }
-    //
-    // Update "part" directives.
-    //
-    LibraryIdentifier libraryNameNode = null;
-    String partsLibraryName = _UNKNOWN_LIBRARY_NAME;
-    bool hasPartDirective = false;
-    FunctionElement entryPoint =
-        _findEntryPoint(definingCompilationUnitElement);
-    List<Directive> directivesToResolve = <Directive>[];
-    List<CompilationUnitElementImpl> sourcedCompilationUnits =
-        <CompilationUnitElementImpl>[];
-    for (Directive directive in definingCompilationUnit.directives) {
-      if (directive is LibraryDirective) {
-        if (libraryNameNode == null) {
-          libraryNameNode = directive.name;
-          directivesToResolve.add(directive);
-        }
-      } else if (directive is PartDirective) {
-        PartDirective partDirective = directive;
-        StringLiteral partUri = partDirective.uri;
-        Source partSource = partDirective.source;
-        hasPartDirective = true;
-        CompilationUnit partUnit = partUnitMap[partSource];
-        if (partUnit != null) {
-          CompilationUnitElementImpl partElement = partUnit.element;
-          partElement.uriOffset = partUri.offset;
-          partElement.uriEnd = partUri.end;
-          partElement.uri = partDirective.uriContent;
-          //
-          // Validate that the part contains a part-of directive with the same
-          // name as the library.
-          //
-          if (context.exists(partSource)) {
-            String partLibraryName =
-                _getPartLibraryName(partSource, partUnit, directivesToResolve);
-            if (partLibraryName == null) {
-              errors.add(new AnalysisError(librarySource, partUri.offset,
-                  partUri.length, CompileTimeErrorCode.PART_OF_NON_PART,
-                  [partUri.toSource()]));
-            } else if (libraryNameNode == null) {
-              if (partsLibraryName == _UNKNOWN_LIBRARY_NAME) {
-                partsLibraryName = partLibraryName;
-              } else if (partsLibraryName != partLibraryName) {
-                partsLibraryName = null;
-              }
-            } else if (libraryNameNode.name != partLibraryName) {
-              errors.add(new AnalysisError(librarySource, partUri.offset,
-                  partUri.length, StaticWarningCode.PART_OF_DIFFERENT_LIBRARY, [
-                libraryNameNode.name,
-                partLibraryName
-              ]));
-            }
-          }
-          if (entryPoint == null) {
-            entryPoint = _findEntryPoint(partElement);
-          }
-          directive.element = partElement;
-          sourcedCompilationUnits.add(partElement);
-        }
-      }
-    }
-    if (hasPartDirective && libraryNameNode == null) {
-      AnalysisError error;
-      if (partsLibraryName != _UNKNOWN_LIBRARY_NAME &&
-          partsLibraryName != null) {
-        error = new AnalysisErrorWithProperties(librarySource, 0, 0,
-            ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART)
-          ..setProperty(ErrorProperty.PARTS_LIBRARY_NAME, partsLibraryName);
-      } else {
-        error = new AnalysisError(librarySource, 0, 0,
-            ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART);
-      }
-      errors.add(error);
-    }
-    //
-    // Create and populate the library element.
-    //
-    AnalysisContext owningContext = context;
-    if (context is InternalAnalysisContext) {
-      InternalAnalysisContext internalContext = context;
-      owningContext = internalContext.getContextFor(librarySource);
-    }
-    LibraryElementImpl libraryElement =
-        new LibraryElementImpl.forNode(owningContext, libraryNameNode);
-    libraryElement.definingCompilationUnit = definingCompilationUnitElement;
-    libraryElement.entryPoint = entryPoint;
-    libraryElement.parts = sourcedCompilationUnits;
-    for (Directive directive in directivesToResolve) {
-      directive.element = libraryElement;
-    }
-    if (sourcedCompilationUnits.isNotEmpty) {
-      _patchTopLevelAccessors(libraryElement);
-    }
-    //
-    // Record outputs.
-    //
-    outputs[BUILD_LIBRARY_ERRORS] = errors;
-    outputs[LIBRARY_ELEMENT1] = libraryElement;
-    outputs[IS_LAUNCHABLE] = entryPoint != null;
-  }
-
-  /**
-   * Add all of the non-synthetic [getters] and [setters] defined in the given
-   * [unit] that have no corresponding accessor to one of the given collections.
-   */
-  void _collectAccessors(Map<String, PropertyAccessorElement> getters,
-      List<PropertyAccessorElement> setters, CompilationUnitElement unit) {
-    for (PropertyAccessorElement accessor in unit.accessors) {
-      if (accessor.isGetter) {
-        if (!accessor.isSynthetic && accessor.correspondingSetter == null) {
-          getters[accessor.displayName] = accessor;
-        }
-      } else {
-        if (!accessor.isSynthetic && accessor.correspondingGetter == null) {
-          setters.add(accessor);
-        }
-      }
-    }
-  }
-
-  /**
-   * Return the top-level [FunctionElement] entry point, or `null` if the given
-   * [element] does not define an entry point.
-   */
-  FunctionElement _findEntryPoint(CompilationUnitElementImpl element) {
-    for (FunctionElement function in element.functions) {
-      if (function.isEntryPoint) {
-        return function;
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Return the name of the library that the given part is declared to be a
-   * part of, or `null` if the part does not contain a part-of directive.
-   */
-  String _getPartLibraryName(Source partSource, CompilationUnit partUnit,
-      List<Directive> directivesToResolve) {
-    for (Directive directive in partUnit.directives) {
-      if (directive is PartOfDirective) {
-        directivesToResolve.add(directive);
-        LibraryIdentifier libraryName = directive.libraryName;
-        if (libraryName != null) {
-          return libraryName.name;
-        }
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Look through all of the compilation units defined for the given [library],
-   * looking for getters and setters that are defined in different compilation
-   * units but that have the same names. If any are found, make sure that they
-   * have the same variable element.
-   */
-  void _patchTopLevelAccessors(LibraryElementImpl library) {
-    HashMap<String, PropertyAccessorElement> getters =
-        new HashMap<String, PropertyAccessorElement>();
-    List<PropertyAccessorElement> setters = <PropertyAccessorElement>[];
-    _collectAccessors(getters, setters, library.definingCompilationUnit);
-    for (CompilationUnitElement unit in library.parts) {
-      _collectAccessors(getters, setters, unit);
-    }
-    for (PropertyAccessorElement setter in setters) {
-      PropertyAccessorElement getter = getters[setter.displayName];
-      if (getter != null) {
-        TopLevelVariableElementImpl variable = getter.variable;
-        TopLevelVariableElementImpl setterVariable = setter.variable;
-        CompilationUnitElementImpl setterUnit = setterVariable.enclosingElement;
-        setterUnit.replaceTopLevelVariable(setterVariable, variable);
-        variable.setter = setter;
-        (setter as PropertyAccessorElementImpl).variable = variable;
-      }
-    }
-  }
-
-  /**
-   * 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
-   * [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      DEFINING_UNIT_INPUT:
-          RESOLVED_UNIT1.of(new LibrarySpecificUnit(source, source)),
-      PARTS_UNIT_INPUT: INCLUDED_PARTS.of(source).toList((Source unit) {
-        return RESOLVED_UNIT1.of(new LibrarySpecificUnit(source, unit));
-      })
-    };
-  }
-
-  /**
-   * Create a [BuildLibraryElementTask] based on the given [target] in the
-   * given [context].
-   */
-  static BuildLibraryElementTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildLibraryElementTask(context, target);
-  }
-}
-
-/**
- * A task that builds [PUBLIC_NAMESPACE] for a library.
- */
-class BuildPublicNamespaceTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input for [LIBRARY_ELEMENT2] of a library.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildPublicNamespaceTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_ELEMENT3]);
-
-  BuildPublicNamespaceTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    LibraryElementImpl library = getRequiredInput(LIBRARY_INPUT);
-    library.publicNamespace = new PublicNamespaceBuilder().build(library);
-    outputs[LIBRARY_ELEMENT3] = library;
-  }
-
-  /**
-   * 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 library [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{LIBRARY_INPUT: LIBRARY_ELEMENT2.of(source)};
-  }
-
-  /**
-   * Create a [BuildPublicNamespaceTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildPublicNamespaceTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildPublicNamespaceTask(context, target);
-  }
-}
-
-/**
- * A task that builds [EXPORT_SOURCE_CLOSURE] of a library.
- */
-class BuildSourceExportClosureTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the export closure.
-   */
-  static const String EXPORT_INPUT = 'EXPORT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildSourceExportClosureTask', createTask, buildInputs,
-      <ResultDescriptor>[EXPORT_SOURCE_CLOSURE]);
-
-  BuildSourceExportClosureTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    List<Source> exportClosure = getRequiredInput(EXPORT_INPUT);
-    //
-    // Record output.
-    //
-    outputs[EXPORT_SOURCE_CLOSURE] = exportClosure;
-  }
-
-  /**
-   * 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 library [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      EXPORT_INPUT: new _ExportSourceClosureTaskInput(source, LIBRARY_ELEMENT2)
-    };
-  }
-
-  /**
-   * Create a [BuildSourceExportClosureTask] based on the given [target] in
-   * the given [context].
-   */
-  static BuildSourceExportClosureTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildSourceExportClosureTask(context, target);
-  }
-}
-
-/**
- * A task that builds [IMPORT_EXPORT_SOURCE_CLOSURE] of a library, and also
- * sets [IS_CLIENT].
- */
-class BuildSourceImportExportClosureTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the import/export closure.
-   */
-  static const String IMPORT_EXPORT_INPUT = 'IMPORT_EXPORT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildSourceImportExportClosureTask', createTask, buildInputs,
-      <ResultDescriptor>[IMPORT_EXPORT_SOURCE_CLOSURE, IS_CLIENT]);
-
-  BuildSourceImportExportClosureTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    List<Source> importExportClosure = getRequiredInput(IMPORT_EXPORT_INPUT);
-    Source htmlSource = context.sourceFactory.forUri(DartSdk.DART_HTML);
-    //
-    // Record outputs.
-    //
-    outputs[IMPORT_EXPORT_SOURCE_CLOSURE] = importExportClosure;
-    outputs[IS_CLIENT] = importExportClosure.contains(htmlSource);
-  }
-
-  /**
-   * 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 library [libSource].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      IMPORT_EXPORT_INPUT:
-          new _ImportExportSourceClosureTaskInput(source, LIBRARY_ELEMENT2)
-    };
-  }
-
-  /**
-   * Create a [BuildSourceImportExportClosureTask] based on the given [target]
-   * in the given [context].
-   */
-  static BuildSourceImportExportClosureTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildSourceImportExportClosureTask(context, target);
-  }
-}
-
-/**
- * A task that builds [TYPE_PROVIDER] for a context.
- */
-class BuildTypeProviderTask extends SourceBasedAnalysisTask {
-  /**
-   * The [PUBLIC_NAMESPACE] input of the `dart:core` library.
-   */
-  static const String CORE_INPUT = 'CORE_INPUT';
-
-  /**
-   * The [PUBLIC_NAMESPACE] input of the `dart:async` library.
-   */
-  static const String ASYNC_INPUT = 'ASYNC_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'BuildTypeProviderTask', createTask, buildInputs,
-      <ResultDescriptor>[TYPE_PROVIDER]);
-
-  BuildTypeProviderTask(
-      InternalAnalysisContext context, AnalysisContextTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    LibraryElement coreLibrary = getRequiredInput(CORE_INPUT);
-    LibraryElement asyncLibrary = getRequiredInput(ASYNC_INPUT);
-    Namespace coreNamespace = coreLibrary.publicNamespace;
-    Namespace asyncNamespace = asyncLibrary.publicNamespace;
-    //
-    // Record outputs.
-    //
-    TypeProvider typeProvider =
-        new TypeProviderImpl.forNamespaces(coreNamespace, asyncNamespace);
-    (context as InternalAnalysisContext).typeProvider = typeProvider;
-    outputs[TYPE_PROVIDER] = typeProvider;
-  }
-
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    AnalysisContextTarget contextTarget = target;
-    SourceFactory sourceFactory = contextTarget.context.sourceFactory;
-    Source coreSource = sourceFactory.forUri(DartSdk.DART_CORE);
-    Source asyncSource = sourceFactory.forUri(DartSdk.DART_ASYNC);
-    return <String, TaskInput>{
-      CORE_INPUT: LIBRARY_ELEMENT3.of(coreSource),
-      ASYNC_INPUT: LIBRARY_ELEMENT3.of(asyncSource)
-    };
-  }
-
-  /**
-   * Create a [BuildTypeProviderTask] based on the given [context].
-   */
-  static BuildTypeProviderTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new BuildTypeProviderTask(context, target);
-  }
-}
-
-/**
- * A task that computes [CONSTANT_DEPENDENCIES] for a constant.
- */
-class ComputeConstantDependenciesTask extends ConstantEvaluationAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT5] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ComputeConstantDependenciesTask', createTask, buildInputs,
-      <ResultDescriptor>[CONSTANT_DEPENDENCIES]);
-
-  ComputeConstantDependenciesTask(
-      InternalAnalysisContext context, ConstantEvaluationTarget constant)
-      : super(context, constant);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    // Note: UNIT_INPUT is not needed.  It is merely a bookkeeping dependency
-    // to ensure that resolution has occurred before we attempt to determine
-    // constant dependencies.
-    //
-    ConstantEvaluationTarget constant = target;
-    AnalysisContext context = constant.context;
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    //
-    // Compute dependencies.
-    //
-    List<ConstantEvaluationTarget> dependencies = <ConstantEvaluationTarget>[];
-    new ConstantEvaluationEngine(typeProvider, context.declaredVariables)
-        .computeDependencies(constant, dependencies.add);
-    //
-    // Record outputs.
-    //
-    outputs[CONSTANT_DEPENDENCIES] = dependencies;
-  }
-
-  /**
-   * 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) {
-    if (target is Element) {
-      CompilationUnitElementImpl unit = target
-          .getAncestor((Element element) => element is CompilationUnitElement);
-      return <String, TaskInput>{
-        UNIT_INPUT: RESOLVED_UNIT5
-            .of(new LibrarySpecificUnit(unit.librarySource, target.source)),
-        TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-      };
-    } else if (target is ConstantEvaluationTarget_Annotation) {
-      return <String, TaskInput>{
-        UNIT_INPUT: RESOLVED_UNIT5
-            .of(new LibrarySpecificUnit(target.librarySource, target.source)),
-        TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-      };
-    }
-    throw new AnalysisException(
-        'Cannot build inputs for a ${target.runtimeType}');
-  }
-
-  /**
-   * Create a [ResolveUnitReferencesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ComputeConstantDependenciesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ComputeConstantDependenciesTask(context, target);
-  }
-}
-
-/**
- * A task that computes the value of a constant ([CONSTANT_VALUE]) and
- * stores it in the element model.
- */
-class ComputeConstantValueTask extends ConstantEvaluationAnalysisTask {
-  /**
-   * The name of the input which ensures that dependent constants are evaluated
-   * before the target.
-   */
-  static const String DEPENDENCIES_INPUT = 'DEPENDENCIES_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ComputeConstantValueTask', createTask, buildInputs,
-      <ResultDescriptor>[CONSTANT_VALUE]);
-
-  ComputeConstantValueTask(
-      InternalAnalysisContext context, ConstantEvaluationTarget constant)
-      : super(context, constant);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  bool get handlesDependencyCycles => true;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    // Note: DEPENDENCIES_INPUT is not needed.  It is merely a bookkeeping
-    // dependency to ensure that the constants that this constant depends on
-    // are computed first.
-    ConstantEvaluationTarget constant = target;
-    AnalysisContext context = constant.context;
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    //
-    // Compute the value of the constant, or report an error if there was a
-    // cycle.
-    //
-    ConstantEvaluationEngine constantEvaluationEngine =
-        new ConstantEvaluationEngine(typeProvider, context.declaredVariables);
-    if (dependencyCycle == null) {
-      constantEvaluationEngine.computeConstantValue(constant);
-    } else {
-      List<ConstantEvaluationTarget> constantsInCycle =
-          <ConstantEvaluationTarget>[];
-      for (WorkItem workItem in dependencyCycle) {
-        if (workItem.descriptor == DESCRIPTOR) {
-          constantsInCycle.add(workItem.target);
-        }
-      }
-      assert(constantsInCycle.isNotEmpty);
-      constantEvaluationEngine.generateCycleError(constantsInCycle, constant);
-    }
-    //
-    // Record outputs.
-    //
-    outputs[CONSTANT_VALUE] = constant;
-  }
-
-  /**
-   * 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) {
-    ConstantEvaluationTarget evaluationTarget = target;
-    return <String, TaskInput>{
-      DEPENDENCIES_INPUT:
-          CONSTANT_DEPENDENCIES.of(evaluationTarget).toListOf(CONSTANT_VALUE),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [ComputeConstantValueTask] based on the given [target] in the
-   * given [context].
-   */
-  static ComputeConstantValueTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ComputeConstantValueTask(context, target);
-  }
-}
-
-/**
- * A base class for analysis tasks whose target is expected to be a
- * [ConstantEvaluationTarget].
- */
-abstract class ConstantEvaluationAnalysisTask extends AnalysisTask {
-  /**
-   * Initialize a newly created task to perform analysis within the given
-   * [context] in order to produce results for the given [constant].
-   */
-  ConstantEvaluationAnalysisTask(
-      AnalysisContext context, ConstantEvaluationTarget constant)
-      : super(context, constant);
-
-  @override
-  String get description {
-    Source source = target.source;
-    String sourceName = source == null ? '<unknown source>' : source.fullName;
-    return '${descriptor.name} for element $target in source $sourceName';
-  }
-}
-
-/**
- * Interface for [AnalysisTarget]s for which constant evaluation can be
- * performed.
- */
-abstract class ConstantEvaluationTarget extends AnalysisTarget {
-  /**
-   * Return the [AnalysisContext] which should be used to evaluate this
-   * constant.
-   */
-  AnalysisContext get context;
-}
-
-/**
- * A task that computes a list of the libraries containing the target source.
- */
-class ContainingLibrariesTask extends SourceBasedAnalysisTask {
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ContainingLibrariesTask', createTask, buildInputs,
-      <ResultDescriptor>[CONTAINING_LIBRARIES]);
-
-  ContainingLibrariesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    // TODO(brianwilkerson) This value can change as new libraries are analyzed
-    // so we need some way of making sure that this result is removed from the
-    // cache appropriately.
-    Source source = getRequiredSource();
-    outputs[CONTAINING_LIBRARIES] = context.getLibrariesContaining(source);
-  }
-
-  /**
-   * 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) {
-    return <String, TaskInput>{};
-  }
-
-  /**
-   * Create a [ContainingLibrariesTask] based on the given [target] in the given
-   * [context].
-   */
-  static ContainingLibrariesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ContainingLibrariesTask(context, target);
-  }
-}
-
-/**
- * The description for a change in a Dart source.
- */
-class DartDelta extends Delta {
-  bool hasDirectiveChange = false;
-
-  final Set<String> addedNames = new Set<String>();
-  final Set<String> changedNames = new Set<String>();
-  final Set<String> removedNames = new Set<String>();
-
-  final Set<Source> invalidatedSources = new Set<Source>();
-
-  DartDelta(Source source) : super(source) {
-    invalidatedSources.add(source);
-  }
-
-  void elementAdded(Element element) {
-    addedNames.add(element.name);
-  }
-
-  void elementChanged(Element element) {
-    changedNames.add(element.name);
-  }
-
-  void elementRemoved(Element element) {
-    removedNames.add(element.name);
-  }
-
-  bool isNameAffected(String name) {
-    return addedNames.contains(name) ||
-        changedNames.contains(name) ||
-        removedNames.contains(name);
-  }
-
-  bool nameChanged(String name) {
-    return changedNames.add(name);
-  }
-
-  @override
-  DeltaResult validate(InternalAnalysisContext context, AnalysisTarget target,
-      ResultDescriptor descriptor) {
-    if (hasDirectiveChange) {
-      return DeltaResult.INVALIDATE;
-    }
-    // Prepare target source.
-    Source targetSource = null;
-    if (target is Source) {
-      targetSource = target;
-    }
-    if (target is LibrarySpecificUnit) {
-      targetSource = target.library;
-    }
-    if (target is Element) {
-      targetSource = target.source;
-    }
-    // Keep results that are updated incrementally.
-    // If we want to analyze only some references to the source being changed,
-    // we need to keep the same instances of CompilationUnitElement and
-    // LibraryElement.
-    if (targetSource == source) {
-      if (ParseDartTask.DESCRIPTOR.results.contains(descriptor)) {
-        return DeltaResult.KEEP_CONTINUE;
-      }
-      if (BuildCompilationUnitElementTask.DESCRIPTOR.results
-          .contains(descriptor)) {
-        return DeltaResult.KEEP_CONTINUE;
-      }
-      if (BuildLibraryElementTask.DESCRIPTOR.results.contains(descriptor)) {
-        return DeltaResult.KEEP_CONTINUE;
-      }
-      return DeltaResult.INVALIDATE;
-    }
-    // Use the target library dependency information to decide whether
-    // the delta affects the library.
-    if (targetSource != null) {
-      List<Source> librarySources =
-          context.getLibrariesContaining(targetSource);
-      for (Source librarySource in librarySources) {
-        AnalysisCache cache = context.analysisCache;
-        ReferencedNames referencedNames =
-            cache.getValue(librarySource, REFERENCED_NAMES);
-        if (referencedNames == null) {
-          return DeltaResult.INVALIDATE;
-        }
-        referencedNames.addChangedElements(this);
-        if (referencedNames.isAffectedBy(this)) {
-          return DeltaResult.INVALIDATE;
-        }
-      }
-      return DeltaResult.STOP;
-    }
-    // We don't know what to do with the given target, invalidate it.
-    return DeltaResult.INVALIDATE;
-  }
-}
-
-/**
- * A task that merges all of the errors for a single source into a single list
- * of errors.
- */
-class DartErrorsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [BUILD_DIRECTIVES_ERRORS] input.
-   */
-  static const String BUILD_DIRECTIVES_ERRORS_INPUT = 'BUILD_DIRECTIVES_ERRORS';
-
-  /**
-   * The name of the [BUILD_LIBRARY_ERRORS] input.
-   */
-  static const String BUILD_LIBRARY_ERRORS_INPUT = 'BUILD_LIBRARY_ERRORS';
-
-  /**
-   * The name of the [LIBRARY_UNIT_ERRORS] input.
-   */
-  static const String LIBRARY_UNIT_ERRORS_INPUT = 'LIBRARY_UNIT_ERRORS';
-
-  /**
-   * The name of the [PARSE_ERRORS] input.
-   */
-  static const String PARSE_ERRORS_INPUT = 'PARSE_ERRORS';
-
-  /**
-   * The name of the [SCAN_ERRORS] input.
-   */
-  static const String SCAN_ERRORS_INPUT = 'SCAN_ERRORS';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('DartErrorsTask',
-      createTask, buildInputs, <ResultDescriptor>[DART_ERRORS]);
-
-  DartErrorsTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    List<List<AnalysisError>> errorLists = <List<AnalysisError>>[];
-    errorLists.add(getRequiredInput(BUILD_DIRECTIVES_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(BUILD_LIBRARY_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(PARSE_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(SCAN_ERRORS_INPUT));
-    Map<Source, List<AnalysisError>> unitErrors =
-        getRequiredInput(LIBRARY_UNIT_ERRORS_INPUT);
-    for (List<AnalysisError> errors in unitErrors.values) {
-      errorLists.add(errors);
-    }
-    //
-    // Record outputs.
-    //
-    outputs[DART_ERRORS] = AnalysisError.mergeLists(errorLists);
-  }
-
-  /**
-   * 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) {
-    Source source = target;
-    return <String, TaskInput>{
-      BUILD_DIRECTIVES_ERRORS_INPUT: BUILD_DIRECTIVES_ERRORS.of(source),
-      BUILD_LIBRARY_ERRORS_INPUT: BUILD_LIBRARY_ERRORS.of(source),
-      PARSE_ERRORS_INPUT: PARSE_ERRORS.of(source),
-      SCAN_ERRORS_INPUT: SCAN_ERRORS.of(source),
-      LIBRARY_UNIT_ERRORS_INPUT: CONTAINING_LIBRARIES
-          .of(source)
-          .toMap((Source library) {
-        LibrarySpecificUnit unit = new LibrarySpecificUnit(library, source);
-        return LIBRARY_UNIT_ERRORS.of(unit);
-      })
-    };
-  }
-
-  /**
-   * Create a [DartErrorsTask] based on the given [target] in the given
-   * [context].
-   */
-  static DartErrorsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new DartErrorsTask(context, target);
-  }
-}
-
-/**
- * A task that builds [RESOLVED_UNIT] for a unit.
- */
-class EvaluateUnitConstantsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT5] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [CONSTANT_VALUE] input.
-   */
-  static const String CONSTANT_VALUES = 'CONSTANT_VALUES';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'EvaluateUnitConstantsTask', createTask, buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT]);
-
-  EvaluateUnitConstantsTask(AnalysisContext context, LibrarySpecificUnit target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    // No actual work needs to be performed; the task manager will ensure that
-    // all constants are evaluated before this method is called.
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    outputs[RESOLVED_UNIT] = unit;
-  }
-
-  /**
-   * 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>{
-      'libraryElement': LIBRARY_ELEMENT.of(unit.library),
-      UNIT_INPUT: RESOLVED_UNIT5.of(unit),
-      CONSTANT_VALUES:
-          COMPILATION_UNIT_CONSTANTS.of(unit).toListOf(CONSTANT_VALUE)
-    };
-  }
-
-  /**
-   * Create an [EvaluateUnitConstantsTask] based on the given [target] in
-   * the given [context].
-   */
-  static EvaluateUnitConstantsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new EvaluateUnitConstantsTask(context, target);
-  }
-}
-
-/**
- * The helper for building the export [Namespace] of a [LibraryElement].
- */
-class ExportNamespaceBuilder {
-  /**
-   * Build the export [Namespace] of the given [LibraryElement].
-   */
-  Namespace build(LibraryElement library) {
-    return new Namespace(
-        _createExportMapping(library, new HashSet<LibraryElement>()));
-  }
-
-  /**
-   * Create a mapping table representing the export namespace of the given
-   * [library].
-   *
-   * The given [visitedElements] a set of libraries that do not need to be
-   * visited when processing the export directives of the given library because
-   * all of the names defined by them will be added by another library.
-   */
-  HashMap<String, Element> _createExportMapping(
-      LibraryElement library, HashSet<LibraryElement> visitedElements) {
-    visitedElements.add(library);
-    try {
-      HashMap<String, Element> definedNames = new HashMap<String, Element>();
-      // Add names of the export directives.
-      for (ExportElement element in library.exports) {
-        LibraryElement exportedLibrary = element.exportedLibrary;
-        if (exportedLibrary != null &&
-            !visitedElements.contains(exportedLibrary)) {
-          //
-          // The exported library will be null if the URI does not reference a
-          // valid library.
-          //
-          HashMap<String, Element> exportedNames =
-              _createExportMapping(exportedLibrary, visitedElements);
-          exportedNames = _applyCombinators(exportedNames, element.combinators);
-          definedNames.addAll(exportedNames);
-        }
-      }
-      // Add names of the public namespace.
-      {
-        Namespace publicNamespace = library.publicNamespace;
-        if (publicNamespace != null) {
-          definedNames.addAll(publicNamespace.definedNames);
-        }
-      }
-      return definedNames;
-    } finally {
-      visitedElements.remove(library);
-    }
-  }
-
-  /**
-   * Apply the given [combinators] to all of the names in [definedNames].
-   */
-  static HashMap<String, Element> _applyCombinators(
-      HashMap<String, Element> definedNames,
-      List<NamespaceCombinator> combinators) {
-    for (NamespaceCombinator combinator in combinators) {
-      if (combinator is HideElementCombinator) {
-        _hide(definedNames, combinator.hiddenNames);
-      } else if (combinator is ShowElementCombinator) {
-        definedNames = _show(definedNames, combinator.shownNames);
-      }
-    }
-    return definedNames;
-  }
-
-  /**
-   * Hide all of the [hiddenNames] by removing them from the given
-   * [definedNames].
-   */
-  static void _hide(
-      HashMap<String, Element> definedNames, List<String> hiddenNames) {
-    for (String name in hiddenNames) {
-      definedNames.remove(name);
-      definedNames.remove('$name=');
-    }
-  }
-
-  /**
-   * Show only the given [shownNames] by removing all other names from the given
-   * [definedNames].
-   */
-  static HashMap<String, Element> _show(
-      HashMap<String, Element> definedNames, List<String> shownNames) {
-    HashMap<String, Element> newNames = new HashMap<String, Element>();
-    for (String name in shownNames) {
-      Element element = definedNames[name];
-      if (element != null) {
-        newNames[name] = element;
-      }
-      String setterName = '$name=';
-      element = definedNames[setterName];
-      if (element != null) {
-        newNames[setterName] = element;
-      }
-    }
-    return newNames;
-  }
-}
-
-/**
- * A task that builds [USED_IMPORTED_ELEMENTS] for a unit.
- */
-class GatherUsedImportedElementsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT5] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'GatherUsedImportedElementsTask', createTask, buildInputs,
-      <ResultDescriptor>[USED_IMPORTED_ELEMENTS]);
-
-  GatherUsedImportedElementsTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    LibraryElement libraryElement = unitElement.library;
-    //
-    // Prepare used imported elements.
-    //
-    GatherUsedImportedElementsVisitor visitor =
-        new GatherUsedImportedElementsVisitor(libraryElement);
-    unit.accept(visitor);
-    //
-    // Record outputs.
-    //
-    outputs[USED_IMPORTED_ELEMENTS] = visitor.usedElements;
-  }
-
-  /**
-   * 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>{UNIT_INPUT: RESOLVED_UNIT5.of(unit)};
-  }
-
-  /**
-   * Create a [GatherUsedImportedElementsTask] based on the given [target] in
-   * the given [context].
-   */
-  static GatherUsedImportedElementsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new GatherUsedImportedElementsTask(context, target);
-  }
-}
-
-/**
- * A task that builds [USED_LOCAL_ELEMENTS] for a unit.
- */
-class GatherUsedLocalElementsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT5] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'GatherUsedLocalElementsTask', createTask, buildInputs,
-      <ResultDescriptor>[USED_LOCAL_ELEMENTS]);
-
-  GatherUsedLocalElementsTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    LibraryElement libraryElement = unitElement.library;
-    //
-    // Prepare used local elements.
-    //
-    GatherUsedLocalElementsVisitor visitor =
-        new GatherUsedLocalElementsVisitor(libraryElement);
-    unit.accept(visitor);
-    //
-    // Record outputs.
-    //
-    outputs[USED_LOCAL_ELEMENTS] = visitor.usedElements;
-  }
-
-  /**
-   * 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>{UNIT_INPUT: RESOLVED_UNIT5.of(unit)};
-  }
-
-  /**
-   * Create a [GatherUsedLocalElementsTask] based on the given [target] in
-   * the given [context].
-   */
-  static GatherUsedLocalElementsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new GatherUsedLocalElementsTask(context, target);
-  }
-}
-
-/**
- * A task that generates [HINTS] for a unit.
- */
-class GenerateHintsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT5] input.
-   */
-  static const String RESOLVED_UNIT_INPUT = 'RESOLVED_UNIT';
-
-  /**
-   * The name of a list of [USED_LOCAL_ELEMENTS] for each library unit input.
-   */
-  static const String USED_LOCAL_ELEMENTS_INPUT = 'USED_LOCAL_ELEMENTS';
-
-  /**
-   * The name of a list of [USED_IMPORTED_ELEMENTS] for each library unit input.
-   */
-  static const String USED_IMPORTED_ELEMENTS_INPUT = 'USED_IMPORTED_ELEMENTS';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'GenerateHintsTask', createTask, buildInputs, <ResultDescriptor>[HINTS]);
-
-  GenerateHintsTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    AnalysisOptions analysisOptions = context.analysisOptions;
-    if (!analysisOptions.hint) {
-      outputs[HINTS] = AnalysisError.NO_ERRORS;
-      return;
-    }
-    //
-    // Prepare collectors.
-    //
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    Source source = getRequiredSource();
-    ErrorReporter errorReporter = new ErrorReporter(errorListener, source);
-    //
-    // Prepare inputs.
-    //
-    CompilationUnit unit = getRequiredInput(RESOLVED_UNIT_INPUT);
-    List<UsedImportedElements> usedImportedElementsList =
-        getRequiredInput(USED_IMPORTED_ELEMENTS_INPUT);
-    List<UsedLocalElements> usedLocalElementsList =
-        getRequiredInput(USED_LOCAL_ELEMENTS_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    LibraryElement libraryElement = unitElement.library;
-    //
-    // Generate errors.
-    //
-    unit.accept(new DeadCodeVerifier(errorReporter));
-    // Verify imports.
-    {
-      ImportsVerifier verifier = new ImportsVerifier();
-      verifier.addImports(unit);
-      usedImportedElementsList.forEach(verifier.removeUsedElements);
-      verifier.generateDuplicateImportHints(errorReporter);
-      verifier.generateUnusedImportHints(errorReporter);
-    }
-    // Unused local elements.
-    {
-      UsedLocalElements usedElements =
-          new UsedLocalElements.merge(usedLocalElementsList);
-      UnusedLocalElementsVerifier visitor =
-          new UnusedLocalElementsVerifier(errorListener, usedElements);
-      unitElement.accept(visitor);
-    }
-    // Dart2js analysis.
-    if (analysisOptions.dart2jsHint) {
-      unit.accept(new Dart2JSVerifier(errorReporter));
-    }
-    // Dart best practices.
-    InheritanceManager inheritanceManager =
-        new InheritanceManager(libraryElement);
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    unit.accept(new BestPracticesVerifier(errorReporter, typeProvider));
-    unit.accept(new OverrideVerifier(errorReporter, inheritanceManager));
-    // Find to-do comments.
-    new ToDoFinder(errorReporter).findIn(unit);
-    //
-    // Record outputs.
-    //
-    outputs[HINTS] = errorListener.errors;
-  }
-
-  /**
-   * 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;
-    Source libSource = unit.library;
-    return <String, TaskInput>{
-      RESOLVED_UNIT_INPUT: RESOLVED_UNIT.of(unit),
-      USED_LOCAL_ELEMENTS_INPUT: UNITS.of(libSource).toList((unit) {
-        LibrarySpecificUnit target = new LibrarySpecificUnit(libSource, unit);
-        return USED_LOCAL_ELEMENTS.of(target);
-      }),
-      USED_IMPORTED_ELEMENTS_INPUT: UNITS.of(libSource).toList((unit) {
-        LibrarySpecificUnit target = new LibrarySpecificUnit(libSource, unit);
-        return USED_IMPORTED_ELEMENTS.of(target);
-      }),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [GenerateHintsTask] based on the given [target] in
-   * the given [context].
-   */
-  static GenerateHintsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new GenerateHintsTask(context, target);
-  }
-}
-
-/**
- * A task computes all of the errors of all of the units for a single
- * library source and sets the [LIBRARY_ERRORS_READY] flag.
- */
-class LibraryErrorsReadyTask extends SourceBasedAnalysisTask {
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'LibraryErrorsReadyTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_ERRORS_READY]);
-
-  LibraryErrorsReadyTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    outputs[LIBRARY_ERRORS_READY] = true;
-  }
-
-  /**
-   * 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 [library].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    Source source = target;
-    return <String, TaskInput>{
-      'allErrors': UNITS.of(source).toListOf(DART_ERRORS)
-    };
-  }
-
-  /**
-   * Create a [LibraryErrorsReadyTask] based on the given [target] in the given
-   * [context].
-   */
-  static LibraryErrorsReadyTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new LibraryErrorsReadyTask(context, target);
-  }
-}
-
-/**
- * A task that merges all of the errors for a single source into a single list
- * of errors.
- */
-class LibraryUnitErrorsTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [HINTS] input.
-   */
-  static const String HINTS_INPUT = 'HINTS';
-
-  /**
-   * The name of the [RESOLVE_REFERENCES_ERRORS] input.
-   */
-  static const String RESOLVE_REFERENCES_ERRORS_INPUT =
-      'RESOLVE_REFERENCES_ERRORS';
-
-  /**
-   * The name of the [RESOLVE_TYPE_NAMES_ERRORS] input.
-   */
-  static const String RESOLVE_TYPE_NAMES_ERRORS_INPUT =
-      'RESOLVE_TYPE_NAMES_ERRORS';
-
-  /**
-   * The name of the [VARIABLE_REFERENCE_ERRORS] input.
-   */
-  static const String VARIABLE_REFERENCE_ERRORS_INPUT =
-      'VARIABLE_REFERENCE_ERRORS';
-
-  /**
-   * The name of the [VERIFY_ERRORS] input.
-   */
-  static const String VERIFY_ERRORS_INPUT = 'VERIFY_ERRORS';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'LibraryUnitErrorsTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_UNIT_ERRORS]);
-
-  LibraryUnitErrorsTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    List<List<AnalysisError>> errorLists = <List<AnalysisError>>[];
-    errorLists.add(getRequiredInput(HINTS_INPUT));
-    errorLists.add(getRequiredInput(RESOLVE_REFERENCES_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(RESOLVE_TYPE_NAMES_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(VARIABLE_REFERENCE_ERRORS_INPUT));
-    errorLists.add(getRequiredInput(VERIFY_ERRORS_INPUT));
-    //
-    // Record outputs.
-    //
-    outputs[LIBRARY_UNIT_ERRORS] = AnalysisError.mergeLists(errorLists);
-  }
-
-  /**
-   * 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 [unit].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    LibrarySpecificUnit unit = target;
-    return <String, TaskInput>{
-      HINTS_INPUT: HINTS.of(unit),
-      RESOLVE_REFERENCES_ERRORS_INPUT: RESOLVE_REFERENCES_ERRORS.of(unit),
-      RESOLVE_TYPE_NAMES_ERRORS_INPUT: RESOLVE_TYPE_NAMES_ERRORS.of(unit),
-      VARIABLE_REFERENCE_ERRORS_INPUT: VARIABLE_REFERENCE_ERRORS.of(unit),
-      VERIFY_ERRORS_INPUT: VERIFY_ERRORS.of(unit)
-    };
-  }
-
-  /**
-   * Create a [LibraryUnitErrorsTask] based on the given [target] in the given
-   * [context].
-   */
-  static LibraryUnitErrorsTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new LibraryUnitErrorsTask(context, target);
-  }
-}
-
-/**
- * A task that parses the content of a Dart file, producing an AST structure.
- */
-class ParseDartTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the line information produced for the
-   * file.
-   */
-  static const String LINE_INFO_INPUT_NAME = 'LINE_INFO_INPUT_NAME';
-
-  /**
-   * The name of the input whose value is the modification time of the file.
-   */
-  static const String MODIFICATION_TIME_INPUT_NAME =
-      'MODIFICATION_TIME_INPUT_NAME';
-
-  /**
-   * The name of the input whose value is the token stream produced for the file.
-   */
-  static const String TOKEN_STREAM_INPUT_NAME = 'TOKEN_STREAM_INPUT_NAME';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('ParseDartTask',
-      createTask, buildInputs, <ResultDescriptor>[
-    EXPLICITLY_IMPORTED_LIBRARIES,
-    EXPORTED_LIBRARIES,
-    IMPORTED_LIBRARIES,
-    INCLUDED_PARTS,
-    PARSE_ERRORS,
-    PARSED_UNIT,
-    SOURCE_KIND,
-    UNITS
-  ]);
-
-  /**
-   * Initialize a newly created task to parse the content of the Dart file
-   * associated with the given [target] in the given [context].
-   */
-  ParseDartTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    Source source = getRequiredSource();
-    LineInfo lineInfo = getRequiredInput(LINE_INFO_INPUT_NAME);
-    int modificationTime = getRequiredInput(MODIFICATION_TIME_INPUT_NAME);
-    Token tokenStream = getRequiredInput(TOKEN_STREAM_INPUT_NAME);
-
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    Parser parser = new Parser(source, errorListener);
-    AnalysisOptions options = context.analysisOptions;
-    parser.parseFunctionBodies = options.analyzeFunctionBodiesPredicate(source);
-    parser.parseGenericMethods = options.enableGenericMethods;
-    CompilationUnit unit = parser.parseCompilationUnit(tokenStream);
-    unit.lineInfo = lineInfo;
-
-    bool hasNonPartOfDirective = false;
-    bool hasPartOfDirective = false;
-    HashSet<Source> explicitlyImportedSourceSet = new HashSet<Source>();
-    HashSet<Source> exportedSourceSet = new HashSet<Source>();
-    HashSet<Source> includedSourceSet = new HashSet<Source>();
-    for (Directive directive in unit.directives) {
-      if (directive is PartOfDirective) {
-        hasPartOfDirective = true;
-      } else {
-        hasNonPartOfDirective = true;
-        if (directive is UriBasedDirective) {
-          Source referencedSource =
-              resolveDirective(context, source, directive, errorListener);
-          if (referencedSource != null) {
-            if (directive is ExportDirective) {
-              exportedSourceSet.add(referencedSource);
-            } else if (directive is ImportDirective) {
-              explicitlyImportedSourceSet.add(referencedSource);
-            } else if (directive is PartDirective) {
-              includedSourceSet.add(referencedSource);
-            } else {
-              throw new AnalysisException(
-                  '$runtimeType failed to handle a ${directive.runtimeType}');
-            }
-          }
-        }
-      }
-    }
-    //
-    // Always include "dart:core" source.
-    //
-    HashSet<Source> importedSourceSet =
-        new HashSet.from(explicitlyImportedSourceSet);
-    Source coreLibrarySource = context.sourceFactory.forUri(DartSdk.DART_CORE);
-    importedSourceSet.add(coreLibrarySource);
-    //
-    // Compute kind.
-    //
-    SourceKind sourceKind = SourceKind.LIBRARY;
-    if (modificationTime == -1) {
-      sourceKind = SourceKind.UNKNOWN;
-    } else if (hasPartOfDirective && !hasNonPartOfDirective) {
-      sourceKind = SourceKind.PART;
-    }
-    //
-    // Record outputs.
-    //
-    List<Source> explicitlyImportedSources =
-        explicitlyImportedSourceSet.toList();
-    List<Source> exportedSources = exportedSourceSet.toList();
-    List<Source> importedSources = importedSourceSet.toList();
-    List<Source> includedSources = includedSourceSet.toList();
-    List<AnalysisError> parseErrors =
-        removeDuplicateErrors(errorListener.errors);
-    List<Source> unitSources = <Source>[source]..addAll(includedSourceSet);
-    outputs[EXPLICITLY_IMPORTED_LIBRARIES] = explicitlyImportedSources;
-    outputs[EXPORTED_LIBRARIES] = exportedSources;
-    outputs[IMPORTED_LIBRARIES] = importedSources;
-    outputs[INCLUDED_PARTS] = includedSources;
-    outputs[PARSE_ERRORS] = parseErrors;
-    outputs[PARSED_UNIT] = unit;
-    outputs[SOURCE_KIND] = sourceKind;
-    outputs[UNITS] = unitSources;
-  }
-
-  /**
-   * 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
-   * [source].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    return <String, TaskInput>{
-      LINE_INFO_INPUT_NAME: LINE_INFO.of(target),
-      MODIFICATION_TIME_INPUT_NAME: MODIFICATION_TIME.of(target),
-      TOKEN_STREAM_INPUT_NAME: TOKEN_STREAM.of(target)
-    };
-  }
-
-  /**
-   * Create a [ParseDartTask] based on the given [target] in the given
-   * [context].
-   */
-  static ParseDartTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ParseDartTask(context, target);
-  }
-
-  /**
-   * Return the result of resolving the URI of the given URI-based [directive]
-   * against the URI of the given library, or `null` if the URI is not valid.
-   *
-   * Resolution is to be performed in the given [context]. Errors should be
-   * reported to the [errorListener].
-   */
-  static Source resolveDirective(AnalysisContext context, Source librarySource,
-      UriBasedDirective directive, AnalysisErrorListener errorListener) {
-    StringLiteral uriLiteral = directive.uri;
-    String uriContent = uriLiteral.stringValue;
-    if (uriContent != null) {
-      uriContent = uriContent.trim();
-      directive.uriContent = uriContent;
-    }
-    UriValidationCode code = directive.validate();
-    if (code == null) {
-      String encodedUriContent = Uri.encodeFull(uriContent);
-      Source source =
-          context.sourceFactory.resolveUri(librarySource, encodedUriContent);
-      directive.source = source;
-      return source;
-    }
-    if (code == UriValidationCode.URI_WITH_DART_EXT_SCHEME) {
-      return null;
-    }
-    if (code == UriValidationCode.URI_WITH_INTERPOLATION) {
-      errorListener.onError(new AnalysisError(librarySource, uriLiteral.offset,
-          uriLiteral.length, CompileTimeErrorCode.URI_WITH_INTERPOLATION));
-      return null;
-    }
-    if (code == UriValidationCode.INVALID_URI) {
-      errorListener.onError(new AnalysisError(librarySource, uriLiteral.offset,
-          uriLiteral.length, CompileTimeErrorCode.INVALID_URI, [uriContent]));
-      return null;
-    }
-    throw new AnalysisException('Failed to handle validation code: $code');
-  }
-}
-
-/**
- * The helper for building the public [Namespace] of a [LibraryElement].
- */
-class PublicNamespaceBuilder {
-  final HashMap<String, Element> definedNames = new HashMap<String, Element>();
-
-  /**
-   * Build a public [Namespace] of the given [library].
-   */
-  Namespace build(LibraryElement library) {
-    definedNames.clear();
-    _addPublicNames(library.definingCompilationUnit);
-    library.parts.forEach(_addPublicNames);
-    return new Namespace(definedNames);
-  }
-
-  /**
-   * Add the given [element] if it has a publicly visible name.
-   */
-  void _addIfPublic(Element element) {
-    String name = element.name;
-    if (name != null && !Scope.isPrivateName(name)) {
-      definedNames[name] = element;
-    }
-  }
-
-  /**
-   * Add all of the public top-level names that are defined in the given
-   * [compilationUnit].
-   */
-  void _addPublicNames(CompilationUnitElement compilationUnit) {
-    compilationUnit.accessors.forEach(_addIfPublic);
-    compilationUnit.enums.forEach(_addIfPublic);
-    compilationUnit.functions.forEach(_addIfPublic);
-    compilationUnit.functionTypeAliases.forEach(_addIfPublic);
-    compilationUnit.types.forEach(_addIfPublic);
-  }
-}
-
-/**
- * Information about a library - which names it uses, which names it defines
- * with their externally visible dependencies.
- */
-class ReferencedNames {
-  final Set<String> names = new Set<String>();
-  final Map<String, Set<String>> userToDependsOn = <String, Set<String>>{};
-
-  /**
-   * Updates [delta] by adding names that are changed in this library.
-   */
-  void addChangedElements(DartDelta delta) {
-    bool hasProgress = true;
-    while (hasProgress) {
-      hasProgress = false;
-      userToDependsOn.forEach((user, dependencies) {
-        for (String dependency in dependencies) {
-          if (delta.isNameAffected(dependency)) {
-            if (delta.nameChanged(user)) {
-              hasProgress = true;
-            }
-          }
-        }
-      });
-    }
-  }
-
-  /**
-   * Returns `true` if the library described by this object is affected by
-   * the given [delta].
-   */
-  bool isAffectedBy(DartDelta delta) {
-    for (String name in names) {
-      if (delta.isNameAffected(name)) {
-        return true;
-      }
-    }
-    return false;
-  }
-}
-
-/**
- * A builder for creating [ReferencedNames].
- *
- * TODO(scheglov) Record dependencies for all other top-level declarations.
- */
-class ReferencedNamesBuilder extends RecursiveAstVisitor {
-  final ReferencedNames names;
-  int bodyLevel = 0;
-  Set<String> dependsOn;
-
-  ReferencedNamesBuilder(this.names);
-
-  ReferencedNames build(CompilationUnit unit) {
-    unit.accept(this);
-    return names;
-  }
-
-  @override
-  visitBlockFunctionBody(BlockFunctionBody node) {
-    try {
-      bodyLevel++;
-      super.visitBlockFunctionBody(node);
-    } finally {
-      bodyLevel--;
-    }
-  }
-
-  @override
-  visitClassDeclaration(ClassDeclaration node) {
-    dependsOn = new Set<String>();
-    super.visitClassDeclaration(node);
-    names.userToDependsOn[node.name.name] = dependsOn;
-    dependsOn = null;
-  }
-
-  @override
-  visitExpressionFunctionBody(ExpressionFunctionBody node) {
-    try {
-      bodyLevel++;
-      super.visitExpressionFunctionBody(node);
-    } finally {
-      bodyLevel--;
-    }
-  }
-
-  @override
-  visitSimpleIdentifier(SimpleIdentifier node) {
-    if (!node.inDeclarationContext()) {
-      String name = node.name;
-      names.names.add(name);
-      if (dependsOn != null && bodyLevel == 0) {
-        dependsOn.add(name);
-      }
-    }
-  }
-}
-
-/**
- * A task that finishes resolution by requesting [RESOLVED_UNIT_NO_CONSTANTS] for every
- * unit in the libraries closure and produces [LIBRARY_ELEMENT].
- */
-class ResolveLibraryReferencesTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [LIBRARY_ELEMENT5] input.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The name of the list of [RESOLVED_UNIT5] input.
-   */
-  static const String UNITS_INPUT = 'UNITS_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ResolveLibraryReferencesTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_ELEMENT, REFERENCED_NAMES]);
-
-  ResolveLibraryReferencesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    //
-    // Prepare inputs.
-    //
-    LibraryElement library = getRequiredInput(LIBRARY_INPUT);
-    List<CompilationUnit> units = getRequiredInput(UNITS_INPUT);
-    // Compute referenced names.
-    ReferencedNames referencedNames = new ReferencedNames();
-    for (CompilationUnit unit in units) {
-      new ReferencedNamesBuilder(referencedNames).build(unit);
-    }
-    //
-    // Record outputs.
-    //
-    outputs[LIBRARY_ELEMENT] = library;
-    outputs[REFERENCED_NAMES] = referencedNames;
-  }
-
-  /**
-   * 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) {
-    Source source = target;
-    return <String, TaskInput>{
-      LIBRARY_INPUT: LIBRARY_ELEMENT5.of(source),
-      UNITS_INPUT: UNITS.of(source).toList((Source unit) =>
-          RESOLVED_UNIT5.of(new LibrarySpecificUnit(source, unit))),
-      'resolvedUnits': IMPORT_EXPORT_SOURCE_CLOSURE
-          .of(source)
-          .toMapOf(UNITS)
-          .toFlattenList((Source library, Source unit) =>
-              RESOLVED_UNIT5.of(new LibrarySpecificUnit(library, unit))),
-    };
-  }
-
-  /**
-   * Create a [ResolveLibraryReferencesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ResolveLibraryReferencesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ResolveLibraryReferencesTask(context, target);
-  }
-}
-
-/**
- * An artifitial task that does nothing except to force type names resolution
- * for the defining and part units of a library.
- */
-class ResolveLibraryTypeNamesTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [LIBRARY_ELEMENT4] input.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ResolveLibraryTypeNamesTask', createTask, buildInputs,
-      <ResultDescriptor>[LIBRARY_ELEMENT5]);
-
-  ResolveLibraryTypeNamesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    LibraryElement library = getRequiredInput(LIBRARY_INPUT);
-    outputs[LIBRARY_ELEMENT5] = library;
-  }
-
-  /**
-   * 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) {
-    Source source = target;
-    return <String, TaskInput>{
-      'resolvedUnit': UNITS.of(source).toList((Source unit) =>
-          RESOLVED_UNIT3.of(new LibrarySpecificUnit(source, unit))),
-      LIBRARY_INPUT: LIBRARY_ELEMENT4.of(source)
-    };
-  }
-
-  /**
-   * Create a [ResolveLibraryTypeNamesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ResolveLibraryTypeNamesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ResolveLibraryTypeNamesTask(context, target);
-  }
-}
-
-/**
- * A task that builds [RESOLVED_UNIT5] for a unit.
- */
-class ResolveUnitReferencesTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [LIBRARY_ELEMENT5] input.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The name of the [RESOLVED_UNIT4] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ResolveUnitReferencesTask', createTask, buildInputs, <ResultDescriptor>[
-    RESOLVE_REFERENCES_ERRORS,
-    RESOLVED_UNIT5
-  ]);
-
-  ResolveUnitReferencesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    //
-    // Prepare inputs.
-    //
-    LibraryElement libraryElement = getRequiredInput(LIBRARY_INPUT);
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    //
-    // Resolve references.
-    //
-    InheritanceManager inheritanceManager =
-        new InheritanceManager(libraryElement);
-    AstVisitor visitor = new ResolverVisitor(
-        libraryElement, unitElement.source, typeProvider, errorListener,
-        inheritanceManager: inheritanceManager);
-    unit.accept(visitor);
-    //
-    // Record outputs.
-    //
-    outputs[RESOLVE_REFERENCES_ERRORS] =
-        removeDuplicateErrors(errorListener.errors);
-    outputs[RESOLVED_UNIT5] = unit;
-  }
-
-  /**
-   * 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>{
-      'fullyBuiltLibraryElements': IMPORT_EXPORT_SOURCE_CLOSURE
-          .of(unit.library)
-          .toListOf(LIBRARY_ELEMENT5),
-      LIBRARY_INPUT: LIBRARY_ELEMENT5.of(unit.library),
-      UNIT_INPUT: RESOLVED_UNIT4.of(unit),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [ResolveUnitReferencesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ResolveUnitReferencesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ResolveUnitReferencesTask(context, target);
-  }
-}
-
-/**
- * A task that builds [RESOLVED_UNIT3] for a unit.
- */
-class ResolveUnitTypeNamesTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the defining [LIBRARY_ELEMENT4].
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The name of the [RESOLVED_UNIT2] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ResolveUnitTypeNamesTask', createTask, buildInputs, <ResultDescriptor>[
-    RESOLVE_TYPE_NAMES_ERRORS,
-    RESOLVED_UNIT3
-  ]);
-
-  ResolveUnitTypeNamesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    //
-    // Prepare inputs.
-    //
-    LibraryElement library = getRequiredInput(LIBRARY_INPUT);
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    //
-    // Resolve TypeName nodes.
-    //
-    TypeResolverVisitor visitor = new TypeResolverVisitor(
-        library, unitElement.source, typeProvider, errorListener);
-    unit.accept(visitor);
-    //
-    // Record outputs.
-    //
-    outputs[RESOLVE_TYPE_NAMES_ERRORS] =
-        removeDuplicateErrors(errorListener.errors);
-    outputs[RESOLVED_UNIT3] = unit;
-  }
-
-  /**
-   * 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>{
-      'importsExportNamespace':
-          IMPORTED_LIBRARIES.of(unit.library).toMapOf(LIBRARY_ELEMENT4),
-      LIBRARY_INPUT: LIBRARY_ELEMENT4.of(unit.library),
-      UNIT_INPUT: RESOLVED_UNIT2.of(unit),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [ResolveUnitTypeNamesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ResolveUnitTypeNamesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ResolveUnitTypeNamesTask(context, target);
-  }
-}
-
-/**
- * A task that builds [RESOLVED_UNIT4] for a unit.
- */
-class ResolveVariableReferencesTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [LIBRARY_ELEMENT1] input.
-   */
-  static const String LIBRARY_INPUT = 'LIBRARY_INPUT';
-
-  /**
-   * The name of the [RESOLVED_UNIT3] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
-      'ResolveVariableReferencesTask', createTask, buildInputs,
-      <ResultDescriptor>[RESOLVED_UNIT4, VARIABLE_REFERENCE_ERRORS]);
-
-  ResolveVariableReferencesTask(
-      InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    //
-    // Prepare inputs.
-    //
-    LibraryElement libraryElement = getRequiredInput(LIBRARY_INPUT);
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    //
-    // Resolve local variables.
-    //
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    Scope nameScope = new LibraryScope(libraryElement, errorListener);
-    AstVisitor visitor = new VariableResolverVisitor(
-        libraryElement, unitElement.source, typeProvider, errorListener,
-        nameScope: nameScope);
-    unit.accept(visitor);
-    //
-    // Record outputs.
-    //
-    outputs[RESOLVED_UNIT4] = unit;
-    outputs[VARIABLE_REFERENCE_ERRORS] =
-        removeDuplicateErrors(errorListener.errors);
-  }
-
-  /**
-   * 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>{
-      LIBRARY_INPUT: LIBRARY_ELEMENT1.of(unit.library),
-      UNIT_INPUT: RESOLVED_UNIT1.of(unit),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [ResolveVariableReferencesTask] based on the given [target] in
-   * the given [context].
-   */
-  static ResolveVariableReferencesTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ResolveVariableReferencesTask(context, target);
-  }
-}
-
-/**
- * A task that scans the content of a file, producing a set of Dart tokens.
- */
-class ScanDartTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the input whose value is the content of the file.
-   */
-  static const String CONTENT_INPUT_NAME = 'CONTENT_INPUT_NAME';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('ScanDartTask',
-      createTask, buildInputs, <ResultDescriptor>[
-    LINE_INFO,
-    SCAN_ERRORS,
-    TOKEN_STREAM
-  ]);
-
-  /**
-   * Initialize a newly created task to access the content of the source
-   * associated with the given [target] in the given [context].
-   */
-  ScanDartTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    Source source = getRequiredSource();
-
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    if (context.getModificationStamp(target.source) < 0) {
-      String message = 'Content could not be read';
-      if (context is InternalAnalysisContext) {
-        CacheEntry entry =
-            (context as InternalAnalysisContext).getCacheEntry(target);
-        CaughtException exception = entry.exception;
-        if (exception != null) {
-          message = exception.toString();
-        }
-      }
-      errorListener.onError(new AnalysisError(
-          source, 0, 0, ScannerErrorCode.UNABLE_GET_CONTENT, [message]));
-    }
-    if (target is DartScript) {
-      DartScript script = target;
-      List<ScriptFragment> fragments = script.fragments;
-      if (fragments.length < 1) {
-        throw new AnalysisException('Cannot scan scripts with no fragments');
-      } else if (fragments.length > 1) {
-        throw new AnalysisException(
-            'Cannot scan scripts with multiple fragments');
-      }
-      ScriptFragment fragment = fragments[0];
-
-      Scanner scanner = new Scanner(source,
-          new SubSequenceReader(fragment.content, fragment.offset),
-          errorListener);
-      scanner.setSourceStart(fragment.line, fragment.column);
-      scanner.preserveComments = context.analysisOptions.preserveComments;
-
-      outputs[TOKEN_STREAM] = scanner.tokenize();
-      outputs[LINE_INFO] = new LineInfo(scanner.lineStarts);
-      outputs[SCAN_ERRORS] = removeDuplicateErrors(errorListener.errors);
-    } else if (target is Source) {
-      String content = getRequiredInput(CONTENT_INPUT_NAME);
-
-      Scanner scanner =
-          new Scanner(source, new CharSequenceReader(content), errorListener);
-      scanner.preserveComments = context.analysisOptions.preserveComments;
-
-      outputs[TOKEN_STREAM] = scanner.tokenize();
-      outputs[LINE_INFO] = new LineInfo(scanner.lineStarts);
-      outputs[SCAN_ERRORS] = removeDuplicateErrors(errorListener.errors);
-    } else {
-      throw new AnalysisException(
-          'Cannot scan Dart code from a ${target.runtimeType}');
-    }
-  }
-
-  /**
-   * 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
-   * [source].
-   */
-  static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
-    if (target is Source) {
-      return <String, TaskInput>{CONTENT_INPUT_NAME: CONTENT.of(target)};
-    } else if (target is DartScript) {
-      // This task does not use the following input; it is included only to add
-      // a dependency between this value and the containing source so that when
-      // the containing source is modified these results will be invalidated.
-      return <String, TaskInput>{'-': DART_SCRIPTS.of(target.source)};
-    }
-    throw new AnalysisException(
-        'Cannot build inputs for a ${target.runtimeType}');
-  }
-
-  /**
-   * Create a [ScanDartTask] based on the given [target] in the given [context].
-   */
-  static ScanDartTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new ScanDartTask(context, target);
-  }
-}
-
-/**
- * A task that builds [VERIFY_ERRORS] for a unit.
- */
-class VerifyUnitTask extends SourceBasedAnalysisTask {
-  /**
-   * The name of the [RESOLVED_UNIT] input.
-   */
-  static const String UNIT_INPUT = 'UNIT_INPUT';
-
-  /**
-   * The name of the [TYPE_PROVIDER] input.
-   */
-  static const String TYPE_PROVIDER_INPUT = 'TYPE_PROVIDER_INPUT';
-
-  /**
-   * The task descriptor describing this kind of task.
-   */
-  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('VerifyUnitTask',
-      createTask, buildInputs, <ResultDescriptor>[VERIFY_ERRORS]);
-
-  /**
-   * The [ErrorReporter] to report errors to.
-   */
-  ErrorReporter errorReporter;
-
-  VerifyUnitTask(InternalAnalysisContext context, AnalysisTarget target)
-      : super(context, target);
-
-  @override
-  TaskDescriptor get descriptor => DESCRIPTOR;
-
-  @override
-  void internalPerform() {
-    RecordingErrorListener errorListener = new RecordingErrorListener();
-    Source source = getRequiredSource();
-    errorReporter = new ErrorReporter(errorListener, source);
-    //
-    // Prepare inputs.
-    //
-    TypeProvider typeProvider = getRequiredInput(TYPE_PROVIDER_INPUT);
-    CompilationUnit unit = getRequiredInput(UNIT_INPUT);
-    CompilationUnitElement unitElement = unit.element;
-    LibraryElement libraryElement = unitElement.library;
-    //
-    // Validate the directives.
-    //
-    validateDirectives(unit);
-    //
-    // Use the ConstantVerifier to compute errors.
-    //
-    ConstantVerifier constantVerifier = new ConstantVerifier(
-        errorReporter, libraryElement, typeProvider, context.declaredVariables);
-    unit.accept(constantVerifier);
-    //
-    // Use the ErrorVerifier to compute errors.
-    //
-    ErrorVerifier errorVerifier = new ErrorVerifier(errorReporter,
-        libraryElement, typeProvider, new InheritanceManager(libraryElement));
-    unit.accept(errorVerifier);
-    //
-    // Record outputs.
-    //
-    outputs[VERIFY_ERRORS] = removeDuplicateErrors(errorListener.errors);
-  }
-
-  /**
-   * Check each directive in the given [unit] to see if the referenced source
-   * exists and report an error if it does not.
-   */
-  void validateDirectives(CompilationUnit unit) {
-    for (Directive directive in unit.directives) {
-      if (directive is UriBasedDirective) {
-        validateReferencedSource(directive);
-      }
-    }
-  }
-
-  /**
-   * Check the given [directive] to see if the referenced source exists and
-   * report an error if it does not.
-   */
-  void validateReferencedSource(UriBasedDirective directive) {
-    Source source = directive.source;
-    if (source != null) {
-      if (context.exists(source)) {
-        return;
-      }
-    } else {
-      // Don't report errors already reported by ParseDartTask.resolveDirective
-      if (directive.validate() != null) {
-        return;
-      }
-    }
-    StringLiteral uriLiteral = directive.uri;
-    errorReporter.reportErrorForNode(CompileTimeErrorCode.URI_DOES_NOT_EXIST,
-        uriLiteral, [directive.uriContent]);
-  }
-
-  /**
-   * 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>{
-      'resolvedUnits': IMPORT_EXPORT_SOURCE_CLOSURE
-          .of(unit.library)
-          .toMapOf(UNITS)
-          .toFlattenList((Source library, Source unit) =>
-              RESOLVED_UNIT.of(new LibrarySpecificUnit(library, unit))),
-      UNIT_INPUT: RESOLVED_UNIT.of(unit),
-      TYPE_PROVIDER_INPUT: TYPE_PROVIDER.of(AnalysisContextTarget.request)
-    };
-  }
-
-  /**
-   * Create a [VerifyUnitTask] based on the given [target] in
-   * the given [context].
-   */
-  static VerifyUnitTask createTask(
-      AnalysisContext context, AnalysisTarget target) {
-    return new VerifyUnitTask(context, target);
-  }
-}
-
-/**
- * A [TaskInput] whose value is a list of library sources exported directly
- * or indirectly by the target [Source].
- *
- * [resultDescriptor] is the type of result which should be produced for each
- * target [Source].
- */
-class _ExportSourceClosureTaskInput extends TaskInputImpl<List<Source>> {
-  final Source target;
-  final ResultDescriptor resultDescriptor;
-
-  _ExportSourceClosureTaskInput(this.target, this.resultDescriptor);
-
-  @override
-  TaskInputBuilder<List<Source>> createBuilder() =>
-      new _SourceClosureTaskInputBuilder(
-          target, _SourceClosureKind.EXPORT, resultDescriptor);
-}
-
-/**
- * A [TaskInput] whose value is a list of library sources imported or exported,
- * directly or indirectly by the target [Source].
- *
- * [resultDescriptor] is the type of result which should be produced for each
- * target [Source].
- */
-class _ImportExportSourceClosureTaskInput extends TaskInputImpl<List<Source>> {
-  final Source target;
-  final ResultDescriptor resultDescriptor;
-
-  _ImportExportSourceClosureTaskInput(this.target, this.resultDescriptor);
-
-  @override
-  TaskInputBuilder<List<Source>> createBuilder() =>
-      new _SourceClosureTaskInputBuilder(
-          target, _SourceClosureKind.IMPORT_EXPORT, resultDescriptor);
-}
-
-/**
- * A [TaskInput] whose value is a list of library sources imported directly
- * or indirectly by the target [Source].
- *
- * [resultDescriptor] is the type of result which should be produced for each
- * target [Source].
- */
-class _ImportSourceClosureTaskInput extends TaskInputImpl<List<Source>> {
-  final Source target;
-  final ResultDescriptor resultDescriptor;
-
-  _ImportSourceClosureTaskInput(this.target, this.resultDescriptor);
-
-  @override
-  TaskInputBuilder<List<Source>> createBuilder() =>
-      new _SourceClosureTaskInputBuilder(
-          target, _SourceClosureKind.IMPORT, resultDescriptor);
-}
-
-/**
- * The kind of the source closure to build.
- */
-enum _SourceClosureKind { IMPORT, EXPORT, IMPORT_EXPORT }
-
-/**
- * A [TaskInputBuilder] to build values for [_ImportSourceClosureTaskInput].
- */
-class _SourceClosureTaskInputBuilder implements TaskInputBuilder<List<Source>> {
-  final _SourceClosureKind kind;
-  final Set<LibraryElement> _libraries = new HashSet<LibraryElement>();
-  final List<Source> _newSources = <Source>[];
-
-  @override
-  final ResultDescriptor currentResult;
-
-  Source currentTarget;
-
-  _SourceClosureTaskInputBuilder(
-      Source librarySource, this.kind, this.currentResult) {
-    _newSources.add(librarySource);
-  }
-
-  @override
-  void set currentValue(Object value) {
-    LibraryElement library = value;
-    if (_libraries.add(library)) {
-      if (kind == _SourceClosureKind.IMPORT ||
-          kind == _SourceClosureKind.IMPORT_EXPORT) {
-        for (ImportElement importElement in library.imports) {
-          Source importedSource = importElement.importedLibrary.source;
-          _newSources.add(importedSource);
-        }
-      }
-      if (kind == _SourceClosureKind.EXPORT ||
-          kind == _SourceClosureKind.IMPORT_EXPORT) {
-        for (ExportElement exportElement in library.exports) {
-          Source exportedSource = exportElement.exportedLibrary.source;
-          _newSources.add(exportedSource);
-        }
-      }
-    }
-  }
-
-  @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;
-  }
-}