Remove old dart2js code.

sdk/lib/_internal/compiler/implementation/elements/modelx.dart

-// Copyright (c) 2013, 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 elements.modelx;
-
-import 'elements.dart';
-import '../constants/expressions.dart';
-import '../helpers/helpers.dart';  // Included for debug helpers.
-import '../tree/tree.dart';
-import '../util/util.dart';
-import '../resolution/resolution.dart';
-import '../resolution/class_members.dart' show ClassMemberMixin;
-
-import '../dart2jslib.dart' show invariant,
-                                 InterfaceType,
-                                 DartType,
-                                 TypeVariableType,
-                                 TypedefType,
-                                 DualKind,
-                                 MessageKind,
-                                 DiagnosticListener,
-                                 Script,
-                                 FunctionType,
-                                 Selector,
-                                 Constant,
-                                 Compiler,
-                                 Backend,
-                                 isPrivateName;
-
-import '../dart_types.dart';
-
-import '../scanner/scannerlib.dart' show
-    EOF_TOKEN,
-    ErrorToken,
-    Token;
-
-import '../ordered_typeset.dart' show OrderedTypeSet;
-
-import 'visitor.dart' show ElementVisitor;
-
-abstract class DeclarationSite {
-}
-
-abstract class ElementX extends Element {
-  static int elementHashCode = 0;
-
-  final String name;
-  final ElementKind kind;
-  final Element enclosingElement;
-  final int hashCode = ++elementHashCode;
-  Link<MetadataAnnotation> metadata = const Link<MetadataAnnotation>();
-
-  ElementX(this.name, this.kind, this.enclosingElement) {
-    assert(isErroneous || implementationLibrary != null);
-  }
-
-  Modifiers get modifiers => Modifiers.EMPTY;
-
-  Node parseNode(DiagnosticListener listener) {
-    listener.internalError(this,
-        'parseNode not implemented on $this.');
-    return null;
-  }
-
-  DartType computeType(Compiler compiler) {
-    compiler.internalError(this,
-        "computeType not implemented on $this.");
-    return null;
-  }
-
-  void addMetadata(MetadataAnnotationX annotation) {
-    assert(annotation.annotatedElement == null);
-    annotation.annotatedElement = this;
-    addMetadataInternal(annotation);
-  }
-
-  void addMetadataInternal(MetadataAnnotation annotation) {
-    metadata = metadata.prepend(annotation);
-  }
-
-  bool get isClosure => false;
-  bool get isClassMember {
-    // Check that this element is defined in the scope of a Class.
-    return enclosingElement != null && enclosingElement.isClass;
-  }
-  bool get isInstanceMember => false;
-  bool get isDeferredLoaderGetter => false;
-
-  bool get isFactoryConstructor => modifiers.isFactory;
-  bool get isConst => modifiers.isConst;
-  bool get isFinal => modifiers.isFinal;
-  bool get isStatic => modifiers.isStatic;
-  bool get isOperator => Elements.isOperatorName(name);
-  bool get impliesType => (kind.category & ElementCategory.IMPLIES_TYPE) != 0;
-
-  bool get isPatched => false;
-
-  bool get isPatch => false;
-
-  bool get isImplementation => true;
-
-  bool get isDeclaration => true;
-
-  bool get isInjected => !isPatch && implementationLibrary.isPatch;
-
-  Element get implementation => this;
-
-  Element get declaration => this;
-
-  Element get patch {
-    throw new UnsupportedError('patch is not supported on $this');
-  }
-
-  Element get origin {
-    throw new UnsupportedError('origin is not supported on $this');
-  }
-
-  bool get isSynthesized => false;
-
-  bool get isForwardingConstructor => false;
-
-  bool get isMixinApplication => false;
-
-  bool get isLocal => false;
-
-  // TODO(johnniwinther): This breaks for libraries (for which enclosing
-  // elements are null) and is invalid for top level variable declarations for
-  // which the enclosing element is a VariableDeclarations and not a compilation
-  // unit.
-  bool get isTopLevel {
-    return enclosingElement != null && enclosingElement.isCompilationUnit;
-  }
-
-  bool get isAssignable {
-    if (isFinal || isConst) return false;
-    if (isFunction || isGenerativeConstructor) return false;
-    return true;
-  }
-
-  Token get position => null;
-
-  Token findMyName(Token token) {
-    return findNameToken(token, isConstructor, name, enclosingElement.name);
-  }
-
-  static Token findNameToken(Token token, bool isConstructor, String name,
-                             String enclosingClassName) {
-    // We search for the token that has the name of this element.
-    // For constructors, that doesn't work because they may have
-    // named formed out of multiple tokens (named constructors) so
-    // for those we search for the class name instead.
-    String needle = isConstructor ? enclosingClassName : name;
-    // The unary '-' operator has a special element name (specified).
-    if (needle == 'unary-') needle = '-';
-    for (Token t = token; EOF_TOKEN != t.kind; t = t.next) {
-      if (t is !ErrorToken && needle == t.value) return t;
-    }
-    return token;
-  }
-
-  CompilationUnitElement get compilationUnit {
-    Element element = this;
-    while (!element.isCompilationUnit) {
-      element = element.enclosingElement;
-    }
-    return element;
-  }
-
-  LibraryElement get library => enclosingElement.library;
-
-  LibraryElement get implementationLibrary {
-    Element element = this;
-    while (!identical(element.kind, ElementKind.LIBRARY)) {
-      element = element.enclosingElement;
-    }
-    return element;
-  }
-
-  ClassElement get enclosingClass {
-    for (Element e = this; e != null; e = e.enclosingElement) {
-      if (e.isClass) return e;
-    }
-    return null;
-  }
-
-  Element get enclosingClassOrCompilationUnit {
-   for (Element e = this; e != null; e = e.enclosingElement) {
-      if (e.isClass || e.isCompilationUnit) return e;
-    }
-    return null;
-  }
-
-  Element get outermostEnclosingMemberOrTopLevel {
-    // TODO(lrn): Why is this called "Outermost"?
-    // TODO(johnniwinther): Clean up this method: This method does not return
-    // the outermost for elements in closure classses, but some call-sites rely
-    // on that behavior.
-    for (Element e = this; e != null; e = e.enclosingElement) {
-      if (e.isClassMember || e.isTopLevel) {
-        return e;
-      }
-    }
-    return null;
-  }
-
-  ClassElement get contextClass {
-    ClassElement cls;
-    for (Element e = this; e != null; e = e.enclosingElement) {
-      if (e.isClass) {
-        // Record [e] instead of returning it directly. We need the last class
-        // in the chain since the first classes might be closure classes.
-        cls = e.declaration;
-      }
-    }
-    return cls;
-  }
-
-  /**
-   * Creates the scope for this element.
-   */
-  Scope buildScope() => enclosingElement.buildScope();
-
-  String toString() {
-    // TODO(johnniwinther): Test for nullness of name, or make non-nullness an
-    // invariant for all element types?
-    var nameText = name != null ? name : '?';
-    if (enclosingElement != null && !isTopLevel) {
-      String holderName = enclosingElement.name != null
-          ? enclosingElement.name
-          : '${enclosingElement.kind}?';
-      return '$kind($holderName#${nameText})';
-    } else {
-      return '$kind(${nameText})';
-    }
-  }
-
-  String _fixedBackendName = null;
-  bool _isNative = false;
-  bool get isNative => _isNative;
-  bool get hasFixedBackendName => _fixedBackendName != null;
-  String get fixedBackendName => _fixedBackendName;
-  // Marks this element as a native element.
-  void setNative(String name) {
-    _isNative = true;
-    _fixedBackendName = name;
-  }
-  void setFixedBackendName(String name) {
-    _fixedBackendName = name;
-  }
-
-  FunctionElement asFunctionElement() => null;
-
-  bool get isAbstract => modifiers.isAbstract;
-  bool isForeign(Backend backend) => backend.isForeign(this);
-
-  void diagnose(Element context, DiagnosticListener listener) {}
-
-  bool get hasTreeElements => analyzableElement.hasTreeElements;
-
-  TreeElements get treeElements => analyzableElement.treeElements;
-
-  AnalyzableElement get analyzableElement {
-    Element element = outermostEnclosingMemberOrTopLevel;
-    if (element.isAbstractField || element.isPrefix) return element.library;
-    return element;
-  }
-
-  DeclarationSite get declarationSite => null;
-}
-
-class ErroneousElementX extends ElementX implements ErroneousElement {
-  final MessageKind messageKind;
-  final Map messageArguments;
-
-  ErroneousElementX(this.messageKind, this.messageArguments,
-                    String name, Element enclosing)
-      : super(name, ElementKind.ERROR, enclosing);
-
-  bool get isTopLevel => false;
-
-  bool get isSynthesized => true;
-
-  AbstractFieldElement abstractField;
-
-  unsupported() {
-    throw 'unsupported operation on erroneous element';
-  }
-
-  Link<MetadataAnnotation> get metadata => unsupported();
-  bool get hasNode => false;
-  get node => unsupported();
-  get hasResolvedAst => false;
-  get resolvedAst => unsupported();
-  get type => unsupported();
-  get cachedNode => unsupported();
-  get functionSignature => unsupported();
-  get patch => null;
-  get origin => this;
-  get immediateRedirectionTarget => unsupported();
-  get nestedClosures => unsupported();
-  get memberContext => unsupported();
-  get executableContext => unsupported();
-
-  bool get isRedirectingFactory => unsupported();
-
-  computeSignature(compiler) => unsupported();
-
-  bool get hasFunctionSignature => false;
-
-  get effectiveTarget => this;
-
-  computeEffectiveTargetType(InterfaceType newType) => unsupported();
-
-  get definingConstructor => null;
-
-  FunctionElement asFunctionElement() => this;
-
-  String get message => '${messageKind.message(messageArguments)}';
-
-  String toString() => '<$name: $message>';
-
-  accept(ElementVisitor visitor) => visitor.visitErroneousElement(this);
-}
-
-/// A message attached to a [WarnOnUseElementX].
-class WrappedMessage {
-  /// The message position. If [:null:] the position of the reference to the
-  /// [WarnOnUseElementX] is used.
-  final Spannable spannable;
-
-  /**
-   * The message to report on resolving a wrapped element.
-   */
-  final MessageKind messageKind;
-
-  /**
-   * The message arguments to report on resolving a wrapped element.
-   */
-  final Map messageArguments;
-
-  WrappedMessage(this.spannable, this.messageKind, this.messageArguments);
-}
-
-class WarnOnUseElementX extends ElementX implements WarnOnUseElement {
-  /// Warning to report on resolving this element.
-  final WrappedMessage warning;
-
-  /// Info to report on resolving this element.
-  final WrappedMessage info;
-
-  /// The element whose usage cause a warning.
-  final Element wrappedElement;
-
-  WarnOnUseElementX(WrappedMessage this.warning, WrappedMessage this.info,
-                    Element enclosingElement, Element wrappedElement)
-      : this.wrappedElement = wrappedElement,
-        super(wrappedElement.name, ElementKind.WARN_ON_USE, enclosingElement);
-
-  Element unwrap(DiagnosticListener listener, Spannable usageSpannable) {
-    var unwrapped = wrappedElement;
-    if (warning != null) {
-      Spannable spannable = warning.spannable;
-      if (spannable == null) spannable = usageSpannable;
-      listener.reportWarning(
-          spannable, warning.messageKind, warning.messageArguments);
-    }
-    if (info != null) {
-      Spannable spannable = info.spannable;
-      if (spannable == null) spannable = usageSpannable;
-      listener.reportInfo(
-          spannable, info.messageKind, info.messageArguments);
-    }
-    if (unwrapped.isWarnOnUse) {
-      unwrapped = unwrapped.unwrap(listener, usageSpannable);
-    }
-    return unwrapped;
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitWarnOnUseElement(this);
-}
-
-class AmbiguousElementX extends ElementX implements AmbiguousElement {
-  /**
-   * The message to report on resolving this element.
-   */
-  final MessageKind messageKind;
-
-  /**
-   * The message arguments to report on resolving this element.
-   */
-  final Map messageArguments;
-
-  /**
-   * The first element that this ambiguous element might refer to.
-   */
-  final Element existingElement;
-
-  /**
-   * The second element that this ambiguous element might refer to.
-   */
-  final Element newElement;
-
-  AmbiguousElementX(this.messageKind, this.messageArguments,
-      Element enclosingElement, Element existingElement, Element newElement)
-      : this.existingElement = existingElement,
-        this.newElement = newElement,
-        super(existingElement.name, ElementKind.AMBIGUOUS, enclosingElement);
-
-  Setlet flatten() {
-    Element element = this;
-    var set = new Setlet();
-    while (element.isAmbiguous) {
-      AmbiguousElement ambiguous = element;
-      set.add(ambiguous.newElement);
-      element = ambiguous.existingElement;
-    }
-    set.add(element);
-    return set;
-  }
-
-  void diagnose(Element context, DiagnosticListener listener) {
-    Setlet ambiguousElements = flatten();
-    MessageKind code = (ambiguousElements.length == 1)
-        ? MessageKind.AMBIGUOUS_REEXPORT : MessageKind.AMBIGUOUS_LOCATION;
-    LibraryElementX importer = context.library;
-    for (Element element in ambiguousElements) {
-      var arguments = {'name': element.name};
-      listener.reportInfo(element, code, arguments);
-      Link<Import> importers = importer.importers.getImports(element);
-      listener.withCurrentElement(importer, () {
-        for (; !importers.isEmpty; importers = importers.tail) {
-          listener.reportInfo(
-              importers.head, MessageKind.IMPORTED_HERE, arguments);
-        }
-      });
-    }
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitAmbiguousElement(this);
-
-  bool get isTopLevel => false;
-}
-
-class ScopeX {
-  final Map<String, Element> contents = new Map<String, Element>();
-
-  bool get isEmpty => contents.isEmpty;
-  Iterable<Element> get values => contents.values;
-
-  Element lookup(String name) {
-    return contents[name];
-  }
-
-  void add(Element element, DiagnosticListener listener) {
-    String name = element.name;
-    if (element.isAccessor) {
-      addAccessor(element, contents[name], listener);
-    } else {
-      Element existing = contents.putIfAbsent(name, () => element);
-      if (!identical(existing, element)) {
-        listener.reportError(
-            element, MessageKind.DUPLICATE_DEFINITION, {'name': name});
-        listener.reportInfo(existing,
-            MessageKind.EXISTING_DEFINITION, {'name': name});
-      }
-    }
-  }
-
-  /**
-   * Adds a definition for an [accessor] (getter or setter) to a scope.
-   * The definition binds to an abstract field that can hold both a getter
-   * and a setter.
-   *
-   * The abstract field is added once, for the first getter or setter, and
-   * reused if the other one is also added.
-   * The abstract field should not be treated as a proper member of the
-   * container, it's simply a way to return two results for one lookup.
-   * That is, the getter or setter does not have the abstract field as enclosing
-   * element, they are enclosed by the class or compilation unit, as is the
-   * abstract field.
-   */
-  void addAccessor(FunctionElementX accessor,
-                   Element existing,
-                   DiagnosticListener listener) {
-    void reportError(Element other) {
-      listener.reportError(accessor,
-                           MessageKind.DUPLICATE_DEFINITION,
-                           {'name': accessor.name});
-      // TODO(johnniwinther): Make this an info instead of a fatal error.
-      listener.reportFatalError(other,
-                                MessageKind.EXISTING_DEFINITION,
-                                {'name': accessor.name});
-    }
-
-    if (existing != null) {
-      if (!identical(existing.kind, ElementKind.ABSTRACT_FIELD)) {
-        reportError(existing);
-      } else {
-        AbstractFieldElementX field = existing;
-        accessor.abstractField = field;
-        if (accessor.isGetter) {
-          if (field.getter != null && field.getter != accessor) {
-            reportError(field.getter);
-          }
-          field.getter = accessor;
-        } else {
-          assert(accessor.isSetter);
-          if (field.setter != null && field.setter != accessor) {
-            reportError(field.setter);
-          }
-          field.setter = accessor;
-        }
-      }
-    } else {
-      Element container = accessor.enclosingClassOrCompilationUnit;
-      AbstractFieldElementX field =
-          new AbstractFieldElementX(accessor.name, container);
-      accessor.abstractField = field;
-      if (accessor.isGetter) {
-        field.getter = accessor;
-      } else {
-        field.setter = accessor;
-      }
-      add(field, listener);
-    }
-  }
-}
-
-class CompilationUnitElementX extends ElementX
-    implements CompilationUnitElement {
-  final Script script;
-  PartOf partTag;
-  Link<Element> localMembers = const Link<Element>();
-
-  CompilationUnitElementX(Script script, LibraryElement library)
-    : this.script = script,
-      super(script.name,
-            ElementKind.COMPILATION_UNIT,
-            library) {
-    library.addCompilationUnit(this);
-  }
-
-  void forEachLocalMember(f(Element element)) {
-    localMembers.forEach(f);
-  }
-
-  void addMember(Element element, DiagnosticListener listener) {
-    // Keep a list of top level members.
-    localMembers = localMembers.prepend(element);
-    // Provide the member to the library to build scope.
-    if (enclosingElement.isPatch) {
-      implementationLibrary.addMember(element, listener);
-    } else {
-      library.addMember(element, listener);
-    }
-  }
-
-  void setPartOf(PartOf tag, DiagnosticListener listener) {
-    LibraryElementX library = enclosingElement;
-    if (library.entryCompilationUnit == this) {
-      listener.reportError(tag, MessageKind.ILLEGAL_DIRECTIVE);
-      return;
-    }
-    if (!localMembers.isEmpty) {
-      listener.reportError(tag, MessageKind.BEFORE_TOP_LEVEL);
-      return;
-    }
-    if (partTag != null) {
-      listener.reportWarning(tag, MessageKind.DUPLICATED_PART_OF);
-      return;
-    }
-    partTag = tag;
-    LibraryName libraryTag = library.libraryTag;
-    String actualName = tag.name.toString();
-    if (libraryTag != null) {
-      String expectedName = libraryTag.name.toString();
-      if (expectedName != actualName) {
-        listener.reportWarning(tag.name,
-            MessageKind.LIBRARY_NAME_MISMATCH,
-            {'libraryName': expectedName});
-      }
-    } else {
-      listener.reportWarning(library,
-          MessageKind.MISSING_LIBRARY_NAME,
-          {'libraryName': actualName});
-      listener.reportInfo(tag.name,
-          MessageKind.THIS_IS_THE_PART_OF_TAG);
-    }
-  }
-
-  bool get hasMembers => !localMembers.isEmpty;
-
-  int compareTo(CompilationUnitElement other) {
-    if (this == other) return 0;
-    return '${script.readableUri}'.compareTo('${other.script.readableUri}');
-  }
-
-  Element get analyzableElement => library;
-
-  accept(ElementVisitor visitor) => visitor.visitCompilationUnitElement(this);
-}
-
-class Importers {
-  Map<Element, Link<Import>> importers = new Map<Element, Link<Import>>();
-
-  Link<Import> getImports(Element element) {
-    Link<Import> imports = importers[element];
-    return imports != null ? imports : const Link<Import>();
-  }
-
-  Import getImport(Element element) => getImports(element).head;
-
-  void registerImport(Element element, Import import) {
-    if (import == null) return;
-
-    importers[element] =
-        importers.putIfAbsent(element, () => const Link<Import>())
-          .prepend(import);
-  }
-}
-
-class ImportScope {
-  /**
-   * Map for elements imported through import declarations.
-   *
-   * Addition to the map is performed by [addImport]. Lookup is done trough
-   * [find].
-   */
-  final Map<String, Element> importScope =
-      new Map<String, Element>();
-
-  /**
-   * Adds [element] to the import scope of this library.
-   *
-   * If an element by the same name is already in the imported scope, an
-   * [ErroneousElement] will be put in the imported scope, allowing for
-   * detection of ambiguous uses of imported names.
-   */
-  void addImport(Element enclosingElement,
-                 Element element,
-                 Import import,
-                 DiagnosticListener listener) {
-    LibraryElementX library = enclosingElement.library;
-    Importers importers = library.importers;
-
-    String name = element.name;
-
-    // The loadLibrary function always shadows existing bindings to that name.
-    if (element.isDeferredLoaderGetter) {
-      importScope.remove(name);
-      // TODO(sigurdm): Print a hint.
-    }
-    Element existing = importScope.putIfAbsent(name, () => element);
-    importers.registerImport(element, import);
-
-    void registerWarnOnUseElement(Import import,
-                                  MessageKind messageKind,
-                                  Element hidingElement,
-                                  Element hiddenElement) {
-      Uri hiddenUri = hiddenElement.library.canonicalUri;
-      Uri hidingUri = hidingElement.library.canonicalUri;
-      Element element = new WarnOnUseElementX(
-          new WrappedMessage(
-              null, // Report on reference to [hidingElement].
-              messageKind,
-              {'name': name, 'hiddenUri': hiddenUri, 'hidingUri': hidingUri}),
-          new WrappedMessage(
-              listener.spanFromSpannable(import),
-              MessageKind.IMPORTED_HERE,
-              {'name': name}),
-          enclosingElement, hidingElement);
-      importScope[name] = element;
-      importers.registerImport(element, import);
-    }
-
-    if (existing != element) {
-      Import existingImport = importers.getImport(existing);
-      Element newElement;
-      if (existing.library.isPlatformLibrary &&
-          !element.library.isPlatformLibrary) {
-        // [existing] is implicitly hidden.
-        registerWarnOnUseElement(
-            import, MessageKind.HIDDEN_IMPORT, element, existing);
-      } else if (!existing.library.isPlatformLibrary &&
-                 element.library.isPlatformLibrary) {
-        // [element] is implicitly hidden.
-        if (import == null) {
-          // [element] is imported implicitly (probably through dart:core).
-          registerWarnOnUseElement(
-              existingImport, MessageKind.HIDDEN_IMPLICIT_IMPORT,
-              existing, element);
-        } else {
-          registerWarnOnUseElement(
-              import, MessageKind.HIDDEN_IMPORT, existing, element);
-        }
-      } else {
-        Element ambiguousElement = new AmbiguousElementX(
-            MessageKind.DUPLICATE_IMPORT, {'name': name},
-            enclosingElement, existing, element);
-        importScope[name] = ambiguousElement;
-        importers.registerImport(ambiguousElement, import);
-        importers.registerImport(ambiguousElement, existingImport);
-      }
-    }
-  }
-
-  Element operator [](String name) => importScope[name];
-}
-
-class LibraryElementX
-    extends ElementX with AnalyzableElementX, PatchMixin<LibraryElementX>
-    implements LibraryElement {
-  final Uri canonicalUri;
-  CompilationUnitElement entryCompilationUnit;
-  Link<CompilationUnitElement> compilationUnits =
-      const Link<CompilationUnitElement>();
-  LinkBuilder<LibraryTag> tagsBuilder = new LinkBuilder<LibraryTag>();
-  List<LibraryTag> tagsCache;
-  LibraryName libraryTag;
-  bool canUseNative = false;
-  Link<Element> localMembers = const Link<Element>();
-  final ScopeX localScope = new ScopeX();
-  final ImportScope importScope = new ImportScope();
-
-  /// A mapping from an imported element to the "import" tag.
-  final Importers importers = new Importers();
-
-  /**
-   * Link for elements exported either through export declarations or through
-   * declaration. This field should not be accessed directly but instead through
-   * the [exports] getter.
-   *
-   * [LibraryDependencyHandler] sets this field through [setExports] when the
-   * library is loaded.
-   */
-  Link<Element> slotForExports;
-
-  final Map<LibraryDependency, LibraryElement> tagMapping =
-      new Map<LibraryDependency, LibraryElement>();
-
-  LibraryElementX(Script script,
-                  [Uri canonicalUri, LibraryElementX origin])
-    : this.canonicalUri =
-          ((canonicalUri == null) ? script.readableUri : canonicalUri),
-      super(script.name, ElementKind.LIBRARY, null) {
-    entryCompilationUnit = new CompilationUnitElementX(script, this);
-    if (origin != null) {
-      origin.applyPatch(this);
-    }
-  }
-
-  bool get isDartCore => canonicalUri == Compiler.DART_CORE;
-
-  Link<MetadataAnnotation> get metadata {
-    return (libraryTag == null) ? super.metadata : libraryTag.metadata;
-  }
-
-  set metadata(value) {
-    // The metadata is stored on [libraryTag].
-    throw new SpannableAssertionFailure(this, 'Cannot set metadata on Library');
-  }
-
-  CompilationUnitElement get compilationUnit => entryCompilationUnit;
-
-  Element get analyzableElement => this;
-
-  void addCompilationUnit(CompilationUnitElement element) {
-    compilationUnits = compilationUnits.prepend(element);
-  }
-
-  void addTag(LibraryTag tag, DiagnosticListener listener) {
-    if (tagsCache != null) {
-      listener.internalError(tag,
-          "Library tags for $this have already been computed.");
-    }
-    tagsBuilder.addLast(tag);
-  }
-
-  Iterable<LibraryTag> get tags {
-    if (tagsCache == null) {
-      tagsCache = tagsBuilder.toList();
-      tagsBuilder = null;
-    }
-    return tagsCache;
-  }
-
-  void recordResolvedTag(LibraryDependency tag, LibraryElement library) {
-    assert(tagMapping[tag] == null);
-    tagMapping[tag] = library;
-  }
-
-  LibraryElement getLibraryFromTag(LibraryDependency tag) => tagMapping[tag];
-
-  /**
-   * Adds [element] to the import scope of this library.
-   *
-   * If an element by the same name is already in the imported scope, an
-   * [ErroneousElement] will be put in the imported scope, allowing for
-   * detection of ambiguous uses of imported names.
-   */
-  void addImport(Element element, Import import, DiagnosticListener listener) {
-    importScope.addImport(this, element, import, listener);
-  }
-
-  void addMember(Element element, DiagnosticListener listener) {
-    localMembers = localMembers.prepend(element);
-    addToScope(element, listener);
-  }
-
-  void addToScope(Element element, DiagnosticListener listener) {
-    localScope.add(element, listener);
-  }
-
-  Element localLookup(String elementName) {
-    Element result = localScope.lookup(elementName);
-    if (result == null && isPatch) {
-      result = origin.localLookup(elementName);
-    }
-    return result;
-  }
-
-  /**
-   * Returns [:true:] if the export scope has already been computed for this
-   * library.
-   */
-  bool get exportsHandled => slotForExports != null;
-
-  Link<Element> get exports {
-    assert(invariant(this, exportsHandled,
-                     message: 'Exports not handled on $this'));
-    return slotForExports;
-  }
-
-  /**
-   * Sets the export scope of this library. This method can only be called once.
-   */
-  void setExports(Iterable<Element> exportedElements) {
-    assert(invariant(this, !exportsHandled,
-        message: 'Exports already set to $slotForExports on $this'));
-    assert(invariant(this, exportedElements != null));
-    var builder = new LinkBuilder<Element>();
-    for (Element export in exportedElements) {
-      builder.addLast(export);
-    }
-    slotForExports = builder.toLink();
-  }
-
-  LibraryElement get library => isPatch ? origin : this;
-
-  /**
-   * Look up a top-level element in this library. The element could
-   * potentially have been imported from another library. Returns
-   * null if no such element exist and an [ErroneousElement] if multiple
-   * elements have been imported.
-   */
-  Element find(String elementName) {
-    Element result = localScope.lookup(elementName);
-    if (result != null) return result;
-    if (origin != null) {
-      result = origin.localScope.lookup(elementName);
-      if (result != null) return result;
-    }
-    result = importScope[elementName];
-    if (result != null) return result;
-    if (origin != null) {
-      result = origin.importScope[elementName];
-      if (result != null) return result;
-    }
-    return null;
-  }
-
-  /** Look up a top-level element in this library, but only look for
-    * non-imported elements. Returns null if no such element exist. */
-  Element findLocal(String elementName) {
-    // TODO(johnniwinther): How to handle injected elements in the patch
-    // library?
-    Element result = localScope.lookup(elementName);
-    if (result == null || result.library != this) return null;
-    return result;
-  }
-
-  Element findExported(String elementName) {
-    for (Link link = exports; !link.isEmpty; link = link.tail) {
-      Element element = link.head;
-      if (element.name == elementName) return element;
-    }
-    return null;
-  }
-
-  void forEachExport(f(Element element)) {
-    exports.forEach((Element e) => f(e));
-  }
-
-  Link<Import> getImportsFor(Element element) => importers.getImports(element);
-
-  void forEachLocalMember(f(Element element)) {
-    if (isPatch) {
-      // Patch libraries traverse both origin and injected members.
-      origin.localMembers.forEach(f);
-
-      void filterPatch(Element element) {
-        if (!element.isPatch) {
-          // Do not traverse the patch members.
-          f(element);
-        }
-      }
-      localMembers.forEach(filterPatch);
-    } else {
-      localMembers.forEach(f);
-    }
-  }
-
-  Iterable<Element> getNonPrivateElementsInScope() {
-    return localScope.values.where((Element element) {
-      // At this point [localScope] only contains members so we don't need
-      // to check for foreign or prefix elements.
-      return !isPrivateName(element.name);
-    });
-  }
-
-  bool hasLibraryName() => libraryTag != null;
-
-  /**
-   * Returns the library name, which is either the name given in the library tag
-   * or the empty string if there is no library tag.
-   */
-  String getLibraryName() {
-    if (libraryTag == null) return '';
-    return libraryTag.name.toString();
-  }
-
-  /**
-   * Returns the library name (as defined by the library tag) or for script
-   * (which have no library tag) the script file name. The latter case is used
-   * to private 'library name' for scripts to use for instance in dartdoc.
-   *
-   * Note: the returned filename will still be escaped ("a%20b.dart" instead of
-   * "a b.dart").
-   */
-  String getLibraryOrScriptName() {
-    if (libraryTag != null) {
-      return libraryTag.name.toString();
-    } else {
-      // Use the file name as script name.
-      String path = canonicalUri.path;
-      return path.substring(path.lastIndexOf('/') + 1);
-    }
-  }
-
-  Scope buildScope() => new LibraryScope(this);
-
-  bool get isPlatformLibrary => canonicalUri.scheme == 'dart';
-
-  bool get isPackageLibrary => canonicalUri.scheme == 'package';
-
-  bool get isInternalLibrary =>
-      isPlatformLibrary && canonicalUri.path.startsWith('_');
-
-  String toString() {
-    if (origin != null) {
-      return 'patch library(${canonicalUri})';
-    } else if (patch != null) {
-      return 'origin library(${canonicalUri})';
-    } else {
-      return 'library(${canonicalUri})';
-    }
-  }
-
-  int compareTo(LibraryElement other) {
-    if (this == other) return 0;
-    return getLibraryOrScriptName().compareTo(other.getLibraryOrScriptName());
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitLibraryElement(this);
-
-  // TODO(johnniwinther): Remove these when issue 18630 is fixed.
-  LibraryElementX get patch => super.patch;
-  LibraryElementX get origin => super.origin;
-}
-
-class PrefixElementX extends ElementX implements PrefixElement {
-  Token firstPosition;
-
-  final ImportScope importScope = new ImportScope();
-
-  bool get isDeferred => _deferredImport != null;
-
-  // Only needed for deferred imports.
-  Import _deferredImport;
-  Import get deferredImport => _deferredImport;
-
-  PrefixElementX(String prefix, Element enclosing, this.firstPosition)
-      : super(prefix, ElementKind.PREFIX, enclosing);
-
-  bool get isTopLevel => false;
-
-  Element lookupLocalMember(String memberName) => importScope[memberName];
-
-  DartType computeType(Compiler compiler) => const DynamicType();
-
-  Token get position => firstPosition;
-
-  void addImport(Element element, Import import, DiagnosticListener listener) {
-    importScope.addImport(this, element, import, listener);
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitPrefixElement(this);
-
-  void markAsDeferred(Import deferredImport) {
-    _deferredImport = deferredImport;
-  }
-}
-
-class TypedefElementX extends ElementX
-    with AstElementMixin,
-         AnalyzableElementX,
-         TypeDeclarationElementX<TypedefType>
-    implements TypedefElement {
-  Typedef cachedNode;
-
-  /**
-   * The type annotation which defines this typedef.
-   */
-  DartType alias;
-
-  /// [:true:] if the typedef has been checked for cyclic reference.
-  bool hasBeenCheckedForCycles = false;
-
-  int resolutionState = STATE_NOT_STARTED;
-
-  TypedefElementX(String name, Element enclosing)
-      : super(name, ElementKind.TYPEDEF, enclosing);
-
-  bool get hasNode => cachedNode != null;
-
-  Typedef get node {
-    assert(invariant(this, cachedNode != null,
-        message: "Node has not been computed for $this."));
-    return cachedNode;
-  }
-
-  /**
-   * Function signature for a typedef of a function type. The signature is
-   * kept to provide full information about parameter names through the mirror
-   * system.
-   *
-   * The [functionSignature] is not available until the typedef element has been
-   * resolved.
-   */
-  FunctionSignature functionSignature;
-
-  TypedefType computeType(Compiler compiler) {
-    if (thisTypeCache != null) return thisTypeCache;
-    Typedef node = parseNode(compiler);
-    setThisAndRawTypes(compiler, createTypeVariables(node.typeParameters));
-    ensureResolved(compiler);
-    return thisTypeCache;
-  }
-
-  void ensureResolved(Compiler compiler) {
-    if (resolutionState == STATE_NOT_STARTED) {
-      compiler.resolver.resolve(this);
-    }
-  }
-
-  TypedefType createType(List<DartType> typeArguments) {
-    return new TypedefType(this, typeArguments);
-  }
-
-  Scope buildScope() {
-    return new TypeDeclarationScope(enclosingElement.buildScope(), this);
-  }
-
-  void checkCyclicReference(Compiler compiler) {
-    if (hasBeenCheckedForCycles) return;
-    var visitor = new TypedefCyclicVisitor(compiler, this);
-    computeType(compiler).accept(visitor, null);
-    hasBeenCheckedForCycles = true;
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitTypedefElement(this);
-
-  // A typedef cannot be patched therefore defines itself.
-  AstElement get definingElement => this;
-}
-
-// This class holds common information for a list of variable or field
-// declarations. It contains the node, and the type. A [VariableElementX]
-// forwards its [computeType] and [parseNode] methods to this class.
-class VariableList implements DeclarationSite {
-  VariableDefinitions definitions;
-  DartType type;
-  final Modifiers modifiers;
-  Link<MetadataAnnotation> metadata = const Link<MetadataAnnotation>();
-
-  VariableList(Modifiers this.modifiers);
-
-  VariableList.node(VariableDefinitions node, this.type)
-      : this.definitions = node,
-        this.modifiers = node.modifiers {
-    assert(modifiers != null);
-  }
-
-  VariableDefinitions parseNode(Element element, DiagnosticListener listener) {
-    return definitions;
-  }
-
-  DartType computeType(Element element, Compiler compiler) => type;
-}
-
-abstract class VariableElementX extends ElementX with AstElementMixin
-    implements VariableElement {
-  final Token token;
-  final VariableList variables;
-  VariableDefinitions definitionsCache;
-  Expression initializerCache;
-
-  Modifiers get modifiers => variables.modifiers;
-
-  VariableElementX(String name,
-                   ElementKind kind,
-                   Element enclosingElement,
-                   VariableList variables,
-                   this.token)
-    : this.variables = variables,
-      super(name, kind, enclosingElement);
-
-  // TODO(johnniwinther): Ensure that the [TreeElements] for this variable hold
-  // the mappings for all its metadata.
-  Link<MetadataAnnotation> get metadata => variables.metadata;
-
-  void addMetadataInternal(MetadataAnnotation annotation) {
-    variables.metadata = variables.metadata.prepend(annotation);
-  }
-
-  // A variable cannot be patched therefore defines itself.
-  AstElement get definingElement => this;
-
-  bool get hasNode => definitionsCache != null;
-
-  VariableDefinitions get node {
-    assert(invariant(this, definitionsCache != null,
-        message: "Node has not been computed for $this."));
-    return definitionsCache;
-  }
-
-  Expression get initializer {
-    assert(invariant(this, definitionsCache != null,
-        message: "Initializer has not been computed for $this."));
-    return initializerCache;
-  }
-
-  Node parseNode(DiagnosticListener listener) {
-    if (definitionsCache != null) return definitionsCache;
-
-    VariableDefinitions definitions = variables.parseNode(this, listener);
-    createDefinitions(definitions);
-    return definitionsCache;
-  }
-
-  void createDefinitions(VariableDefinitions definitions) {
-    assert(invariant(this, definitionsCache == null,
-        message: "VariableDefinitions has already been computed for $this."));
-    Expression node;
-    int count = 0;
-    for (Link<Node> link = definitions.definitions.nodes;
-         !link.isEmpty; link = link.tail) {
-      Expression initializedIdentifier = link.head;
-      Identifier identifier = initializedIdentifier.asIdentifier();
-      if (identifier == null) {
-        SendSet sendSet = initializedIdentifier.asSendSet();
-        identifier = sendSet.selector.asIdentifier();
-        if (identical(name, identifier.source)) {
-          node = initializedIdentifier;
-          initializerCache = sendSet.arguments.first;
-        }
-      } else if (identical(name, identifier.source)) {
-        node = initializedIdentifier;
-      }
-      count++;
-    }
-    invariant(definitions, node != null, message: "Could not find '$name'.");
-    if (count == 1) {
-      definitionsCache = definitions;
-    } else {
-      // Create a [VariableDefinitions] node for the single definition of
-      // [node].
-      definitionsCache = new VariableDefinitions(definitions.type,
-          definitions.modifiers, new NodeList(
-              definitions.definitions.beginToken,
-              const Link<Node>().prepend(node),
-              definitions.definitions.endToken));
-    }
-  }
-
-  DartType computeType(Compiler compiler) {
-    if (variables.type != null) return variables.type;
-    // Call [parseNode] to ensure that [definitionsCache] and [initializerCache]
-    // are set as a consequence of calling [computeType].
-    return compiler.withCurrentElement(this, () {
-      parseNode(compiler);
-      return variables.computeType(this, compiler);
-    });
-  }
-
-  DartType get type {
-    assert(invariant(this, variables.type != null,
-        message: "Type has not been computed for $this."));
-    return variables.type;
-  }
-
-  bool get isInstanceMember => isClassMember && !isStatic;
-
-  // Note: cachedNode.beginToken will not be correct in all
-  // cases, for example, for function typed parameters.
-  Token get position => token;
-
-  accept(ElementVisitor visitor) => visitor.visitVariableElement(this);
-
-  DeclarationSite get declarationSite => variables;
-}
-
-class LocalVariableElementX extends VariableElementX
-    implements LocalVariableElement {
-  LocalVariableElementX(String name,
-                        ExecutableElement enclosingElement,
-                        VariableList variables,
-                        Token token)
-      : super(name, ElementKind.VARIABLE, enclosingElement, variables, token) {
-    createDefinitions(variables.definitions);
-  }
-
-  // TODO(johnniwinther): Remove this when the dart `backend_ast` does not need
-  // [Element] for entities.
-  LocalVariableElementX.synthetic(String name,
-                                  ExecutableElement enclosingElement,
-                                  VariableList variables)
-      : super(name, ElementKind.VARIABLE, enclosingElement, variables, null);
-
-  ExecutableElement get executableContext => enclosingElement;
-
-  ExecutableElement get memberContext => executableContext.memberContext;
-
-  bool get isLocal => true;
-}
-
-class FieldElementX extends VariableElementX
-    with AnalyzableElementX implements FieldElement {
-  List<FunctionElement> nestedClosures = new List<FunctionElement>();
-
-  FieldElementX(Identifier name,
-                Element enclosingElement,
-                VariableList variables)
-    : super(name.source, ElementKind.FIELD, enclosingElement,
-            variables, name.token);
-
-  accept(ElementVisitor visitor) => visitor.visitFieldElement(this);
-
-  MemberElement get memberContext => this;
-
-  void reuseElement() {
-    super.reuseElement();
-    nestedClosures.clear();
-  }
-}
-
-/// [Element] for a parameter-like element.
-class FormalElementX extends ElementX
-    with AstElementMixin
-    implements FormalElement {
-  final VariableDefinitions definitions;
-  final Identifier identifier;
-  DartType typeCache;
-
-  /**
-   * Function signature for a variable with a function type. The signature is
-   * kept to provide full information about parameter names through the mirror
-   * system.
-   */
-  FunctionSignature functionSignatureCache;
-
-  FormalElementX(ElementKind elementKind,
-                 FunctionTypedElement enclosingElement,
-                 this.definitions,
-                 Identifier identifier)
-      : this.identifier = identifier,
-        super(identifier.source, elementKind, enclosingElement);
-
-  FunctionTypedElement get functionDeclaration => enclosingElement;
-
-  Modifiers get modifiers => definitions.modifiers;
-
-  Token get position => identifier.getBeginToken();
-
-  Node parseNode(DiagnosticListener listener) => definitions;
-
-  DartType computeType(Compiler compiler) {
-    assert(invariant(this, type != null,
-        message: "Parameter type has not been set for $this."));
-    return type;
-  }
-
-  DartType get type {
-    assert(invariant(this, typeCache != null,
-            message: "Parameter type has not been set for $this."));
-        return typeCache;
-  }
-
-  FunctionSignature get functionSignature {
-    assert(invariant(this, typeCache != null,
-            message: "Parameter signature has not been set for $this."));
-    return functionSignatureCache;
-  }
-
-  bool get hasNode => true;
-
-  VariableDefinitions get node => definitions;
-
-  FunctionType get functionType => type;
-
-  accept(ElementVisitor visitor) => visitor.visitFormalElement(this);
-
-  // A parameter is defined by the declaration element.
-  AstElement get definingElement => declaration;
-}
-
-/// [Element] for a formal parameter.
-///
-/// A [ParameterElementX] can be patched. A parameter of an external method is
-/// patched with the corresponding parameter of the patch method. This is done
-/// to ensure that default values on parameters are computed once (on the
-/// origin parameter) but can be found through both the origin and the patch.
-abstract class ParameterElementX extends FormalElementX
-  with PatchMixin<ParameterElement> implements ParameterElement {
-  final Expression initializer;
-
-  ParameterElementX(ElementKind elementKind,
-                    FunctionElement functionDeclaration,
-                    VariableDefinitions definitions,
-                    Identifier identifier,
-                    this.initializer)
-      : super(elementKind, functionDeclaration, definitions, identifier);
-
-  FunctionElement get functionDeclaration => enclosingElement;
-
-  ExecutableElement get executableContext => enclosingElement;
-
-  MemberElement get memberContext => executableContext.memberContext;
-
-  accept(ElementVisitor visitor) => visitor.visitParameterElement(this);
-
-  bool get isLocal => true;
-}
-
-class LocalParameterElementX extends ParameterElementX
-    implements LocalParameterElement {
-  LocalParameterElementX(FunctionElement functionDeclaration,
-                         VariableDefinitions definitions,
-                         Identifier identifier,
-                         Expression initializer)
-      : super(ElementKind.PARAMETER, functionDeclaration,
-              definitions, identifier, initializer);
-}
-
-/// Parameters in constructors that directly initialize fields. For example:
-/// `A(this.field)`.
-class InitializingFormalElementX extends ParameterElementX
-    implements InitializingFormalElement {
-  FieldElement fieldElement;
-
-  InitializingFormalElementX(ConstructorElement constructorDeclaration,
-                             VariableDefinitions variables,
-                             Identifier identifier,
-                             Expression initializer,
-                             this.fieldElement)
-      : super(ElementKind.INITIALIZING_FORMAL, constructorDeclaration,
-              variables, identifier, initializer);
-
-  accept(ElementVisitor visitor) => visitor.visitFieldParameterElement(this);
-
-  MemberElement get memberContext => enclosingElement;
-
-  bool get isLocal => false;
-}
-
-
-class AbstractFieldElementX extends ElementX implements AbstractFieldElement {
-  FunctionElementX getter;
-  FunctionElementX setter;
-
-  AbstractFieldElementX(String name, Element enclosing)
-      : super(name, ElementKind.ABSTRACT_FIELD, enclosing);
-
-  DartType computeType(Compiler compiler) {
-    throw "internal error: AbstractFieldElement has no type";
-  }
-
-  Node parseNode(DiagnosticListener listener) {
-    throw "internal error: AbstractFieldElement has no node";
-  }
-
-  Token get position {
-    // The getter and setter may be defined in two different
-    // compilation units.  However, we know that one of them is
-    // non-null and defined in the same compilation unit as the
-    // abstract element.
-    // TODO(lrn): No we don't know that if the element from the same
-    // compilation unit is patched.
-    //
-    // We need to make sure that the position returned is relative to
-    // the compilation unit of the abstract element.
-    if (getter != null
-        && identical(getter.compilationUnit, compilationUnit)) {
-      return getter.position;
-    } else {
-      return setter.position;
-    }
-  }
-
-  Modifiers get modifiers {
-    // The resolver ensures that the flags match (ignoring abstract).
-    if (getter != null) {
-      return new Modifiers.withFlags(
-          getter.modifiers.nodes,
-          getter.modifiers.flags | Modifiers.FLAG_ABSTRACT);
-    } else {
-      return new Modifiers.withFlags(
-          setter.modifiers.nodes,
-          setter.modifiers.flags | Modifiers.FLAG_ABSTRACT);
-    }
-  }
-
-  bool get isInstanceMember {
-    return isClassMember && !isStatic;
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitAbstractFieldElement(this);
-
-  bool get isAbstract {
-    return getter != null && getter.isAbstract
-        || setter != null && setter.isAbstract;
-  }
-}
-
-// TODO(johnniwinther): [FunctionSignature] should be merged with
-// [FunctionType].
-// TODO(karlklose): all these lists should have element type [FormalElement].
-class FunctionSignatureX implements FunctionSignature {
-  final Link<Element> requiredParameters;
-  final Link<Element> optionalParameters;
-  final int requiredParameterCount;
-  final int optionalParameterCount;
-  final bool optionalParametersAreNamed;
-  final List<Element> orderedOptionalParameters;
-  final FunctionType type;
-  final bool hasOptionalParameters;
-
-  FunctionSignatureX(this.requiredParameters,
-                     Link<Element> optionalParameters,
-                     this.requiredParameterCount,
-                     this.optionalParameterCount,
-                     this.optionalParametersAreNamed,
-                     this.orderedOptionalParameters,
-                     this.type)
-      : optionalParameters = optionalParameters,
-        hasOptionalParameters = !optionalParameters.isEmpty;
-
-  void forEachRequiredParameter(void function(Element parameter)) {
-    for (Link<Element> link = requiredParameters;
-         !link.isEmpty;
-         link = link.tail) {
-      function(link.head);
-    }
-  }
-
-  void forEachOptionalParameter(void function(Element parameter)) {
-    for (Link<Element> link = optionalParameters;
-         !link.isEmpty;
-         link = link.tail) {
-      function(link.head);
-    }
-  }
-
-  Element get firstOptionalParameter => optionalParameters.head;
-
-  void forEachParameter(void function(Element parameter)) {
-    forEachRequiredParameter(function);
-    forEachOptionalParameter(function);
-  }
-
-  void orderedForEachParameter(void function(Element parameter)) {
-    forEachRequiredParameter(function);
-    orderedOptionalParameters.forEach(function);
-  }
-
-  int get parameterCount => requiredParameterCount + optionalParameterCount;
-
-  /**
-   * Check whether a function with this signature can be used instead of a
-   * function with signature [signature] without causing a `noSuchMethod`
-   * exception/call.
-   */
-  bool isCompatibleWith(FunctionSignature signature) {
-    if (optionalParametersAreNamed) {
-      if (!signature.optionalParametersAreNamed) {
-        return requiredParameterCount == signature.parameterCount;
-      }
-      // If both signatures have named parameters, then they must have
-      // the same number of required parameters, and the names in
-      // [signature] must all be in [:this:].
-      if (requiredParameterCount != signature.requiredParameterCount) {
-        return false;
-      }
-      Set<String> names = optionalParameters.mapToSet(
-          (Element element) => element.name);
-      for (Element namedParameter in signature.optionalParameters) {
-        if (!names.contains(namedParameter.name)) {
-          return false;
-        }
-      }
-    } else {
-      if (signature.optionalParametersAreNamed) return false;
-      // There must be at least as many arguments as in the other signature, but
-      // this signature must not have more required parameters.  Having more
-      // optional parameters is not a problem, they simply are never provided
-      // by call sites of a call to a method with the other signature.
-      int otherTotalCount = signature.parameterCount;
-      return requiredParameterCount <= otherTotalCount
-          && parameterCount >= otherTotalCount;
-    }
-    return true;
-  }
-}
-
-abstract class BaseFunctionElementX
-    extends ElementX with PatchMixin<FunctionElement>, AstElementMixin
-    implements FunctionElement {
-  DartType typeCache;
-  final Modifiers modifiers;
-
-  List<FunctionElement> nestedClosures = new List<FunctionElement>();
-
-  FunctionSignature functionSignatureCache;
-
-  final bool _hasNoBody;
-
-  AbstractFieldElement abstractField;
-
-  BaseFunctionElementX(String name,
-                       ElementKind kind,
-                       Modifiers this.modifiers,
-                       Element enclosing,
-                       bool hasNoBody)
-      : super(name, kind, enclosing),
-        _hasNoBody = hasNoBody {
-    assert(modifiers != null);
-  }
-
-  bool get isInstanceMember {
-    return isClassMember
-           && !isConstructor
-           && !isStatic;
-  }
-
-  bool get hasFunctionSignature => functionSignatureCache != null;
-
-  FunctionSignature computeSignature(Compiler compiler) {
-    if (functionSignatureCache != null) return functionSignatureCache;
-    compiler.withCurrentElement(this, () {
-      functionSignatureCache = compiler.resolver.resolveSignature(this);
-    });
-    return functionSignatureCache;
-  }
-
-  FunctionSignature get functionSignature {
-    assert(invariant(this, functionSignatureCache != null,
-        message: "Function signature has not been computed for $this."));
-    return functionSignatureCache;
-  }
-
-  FunctionType computeType(Compiler compiler) {
-    if (typeCache != null) return typeCache;
-    typeCache = computeSignature(compiler).type;
-    return typeCache;
-  }
-
-  FunctionType get type {
-    assert(invariant(this, typeCache != null,
-        message: "Type has not been computed for $this."));
-    return typeCache;
-  }
-
-  FunctionElement asFunctionElement() => this;
-
-  String toString() {
-    if (isPatch) {
-      return 'patch ${super.toString()}';
-    } else if (isPatched) {
-      return 'origin ${super.toString()}';
-    } else {
-      return super.toString();
-    }
-  }
-
-  bool get isAbstract {
-    return !modifiers.isExternal &&
-           (isFunction || isAccessor) &&
-           _hasNoBody;
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitFunctionElement(this);
-
-  // A function is defined by the implementation element.
-  AstElement get definingElement => implementation;
-}
-
-abstract class FunctionElementX extends BaseFunctionElementX
-    with AnalyzableElementX implements MemberElement {
-  FunctionElementX(String name,
-                   ElementKind kind,
-                   Modifiers modifiers,
-                   Element enclosing,
-                   bool hasNoBody)
-      : super(name, kind, modifiers, enclosing, hasNoBody);
-
-  MemberElement get memberContext => this;
-
-  void reuseElement() {
-    super.reuseElement();
-    nestedClosures.clear();
-    functionSignatureCache = null;
-    typeCache = null;
-  }
-}
-
-class LocalFunctionElementX extends BaseFunctionElementX
-    implements LocalFunctionElement {
-  final FunctionExpression node;
-
-  LocalFunctionElementX(String name,
-                        FunctionExpression this.node,
-                        ElementKind kind,
-                        Modifiers modifiers,
-                        ExecutableElement enclosing)
-      : super(name, kind, modifiers, enclosing, false);
-
-  ExecutableElement get executableContext => enclosingElement;
-
-  MemberElement get memberContext => executableContext.memberContext;
-
-  bool get hasNode => true;
-
-  FunctionExpression parseNode(DiagnosticListener listener) => node;
-
-  Token get position {
-    // Use the name as position if this is not an unnamed closure.
-    if (node.name != null) {
-      return node.name.getBeginToken();
-    } else {
-      return node.getBeginToken();
-    }
-  }
-
-  bool get isLocal => true;
-}
-
-abstract class ConstructorElementX extends FunctionElementX
-    implements ConstructorElement {
-
-  ConstructorElementX(String name,
-                      ElementKind kind,
-                      Modifiers modifiers,
-                      Element enclosing)
-        : super(name, kind, modifiers, enclosing, false);
-
-  FunctionElement immediateRedirectionTarget;
-
-  bool get isRedirectingFactory => immediateRedirectionTarget != null;
-
-  /// This field is set by the post process queue when checking for cycles.
-  ConstructorElement internalEffectiveTarget;
-  DartType effectiveTargetType;
-
-  void set effectiveTarget(ConstructorElement constructor) {
-    assert(constructor != null && internalEffectiveTarget == null);
-    internalEffectiveTarget = constructor;
-  }
-
-  ConstructorElement get effectiveTarget {
-    if (Elements.isErroneousElement(immediateRedirectionTarget)) {
-      return immediateRedirectionTarget;
-    }
-    assert(!isRedirectingFactory || internalEffectiveTarget != null);
-    return isRedirectingFactory ? internalEffectiveTarget : this;
-  }
-
-  InterfaceType computeEffectiveTargetType(InterfaceType newType) {
-    if (!isRedirectingFactory) return newType;
-    assert(invariant(this, effectiveTargetType != null,
-        message: 'Redirection target type has not yet been computed for '
-                 '$this.'));
-    return effectiveTargetType.substByContext(newType);
-  }
-
-  ConstructorElement get definingConstructor => null;
-
-  ClassElement get enclosingClass => enclosingElement;
-}
-
-class DeferredLoaderGetterElementX extends FunctionElementX {
-  final PrefixElement prefix;
-
-  DeferredLoaderGetterElementX(PrefixElement prefix)
-      : this.prefix = prefix,
-        super("loadLibrary",
-              ElementKind.FUNCTION,
-              Modifiers.EMPTY,
-              prefix, true);
-
-  FunctionSignature computeSignature(Compiler compiler) {
-    if (functionSignatureCache != null) return functionSignature;
-    compiler.withCurrentElement(this, () {
-      DartType inner = new FunctionType(this);
-      functionSignatureCache = new FunctionSignatureX(const Link(),
-          const Link(), 0, 0, false, [], inner);
-    });
-    return functionSignatureCache;
-  }
-
-  bool get isClassMember => false;
-
-  bool isForeign(Backend backend) => true;
-
-  bool get isSynthesized => true;
-
-  bool get isFunction => false;
-
-  bool get isDeferredLoaderGetter => true;
-
-  bool get isGetter => true;
-
-  bool get isTopLevel => true;
-  // By having position null, the enclosing elements location is printed in
-  // error messages.
-  Token get position => null;
-
-  FunctionExpression parseNode(DiagnosticListener listener) => null;
-
-  bool get hasNode => false;
-
-  FunctionExpression get node => null;
-}
-
-class ConstructorBodyElementX extends BaseFunctionElementX
-    implements ConstructorBodyElement {
-  ConstructorElement constructor;
-
-  ConstructorBodyElementX(FunctionElement constructor)
-      : this.constructor = constructor,
-        super(constructor.name,
-              ElementKind.GENERATIVE_CONSTRUCTOR_BODY,
-              Modifiers.EMPTY,
-              constructor.enclosingElement, false) {
-    functionSignatureCache = constructor.functionSignature;
-  }
-
-  bool get hasNode => constructor.hasNode;
-
-  FunctionExpression get node => constructor.node;
-
-  bool get isInstanceMember => true;
-
-  FunctionType computeType(Compiler compiler) {
-    compiler.internalError(this, '$this.computeType.');
-    return null;
-  }
-
-  Token get position => constructor.position;
-
-  Element get outermostEnclosingMemberOrTopLevel => constructor;
-
-  Element get analyzableElement => constructor.analyzableElement;
-
-  accept(ElementVisitor visitor) => visitor.visitConstructorBodyElement(this);
-
-  MemberElement get memberContext => constructor;
-}
-
-/**
- * A constructor that is not defined in the source code but rather implied by
- * the language semantics.
- *
- * This class is used to represent default constructors and forwarding
- * constructors for mixin applications.
- */
-class SynthesizedConstructorElementX extends ConstructorElementX {
-  final ConstructorElement definingConstructor;
-  final bool isDefaultConstructor;
-
-  SynthesizedConstructorElementX(String name,
-                                 this.definingConstructor,
-                                 Element enclosing,
-                                 this.isDefaultConstructor)
-      : super(name,
-              ElementKind.GENERATIVE_CONSTRUCTOR,
-              Modifiers.EMPTY,
-              enclosing);
-
-  SynthesizedConstructorElementX.forDefault(superMember, Element enclosing)
-      : this('', superMember, enclosing, true);
-
-  FunctionExpression parseNode(DiagnosticListener listener) => null;
-
-  bool get hasNode => false;
-
-  FunctionExpression get node => null;
-
-  Token get position => enclosingElement.position;
-
-  bool get isSynthesized => true;
-
-  FunctionSignature computeSignature(compiler) {
-    if (functionSignatureCache != null) return functionSignatureCache;
-    if (isDefaultConstructor) {
-      return functionSignatureCache = new FunctionSignatureX(
-          const Link<Element>(), const Link<Element>(), 0, 0, false,
-          const <Element>[],
-          new FunctionType(this, enclosingClass.thisType));
-    }
-    if (definingConstructor.isErroneous) {
-      return functionSignatureCache =
-          compiler.objectClass.localLookup('').computeSignature(compiler);
-    }
-    // TODO(johnniwinther): Ensure that the function signature (and with it the
-    // function type) substitutes type variables correctly.
-    return functionSignatureCache =
-        definingConstructor.computeSignature(compiler);
-  }
-
-  accept(ElementVisitor visitor) {
-    return visitor.visitFunctionElement(this);
-  }
-}
-
-abstract class TypeDeclarationElementX<T extends GenericType>
-    implements TypeDeclarationElement {
-  /**
-   * The `this type` for this type declaration.
-   *
-   * The type of [:this:] is the generic type based on this element in which
-   * the type arguments are the declared type variables. For instance,
-   * [:List<E>:] for [:List:] and [:Map<K,V>:] for [:Map:].
-   *
-   * For a class declaration this is the type of [:this:].
-   *
-   * This type is computed in [computeType].
-   */
-  T thisTypeCache;
-
-  /**
-   * The raw type for this type declaration.
-   *
-   * The raw type is the generic type base on this element in which the type
-   * arguments are all [dynamic]. For instance [:List<dynamic>:] for [:List:]
-   * and [:Map<dynamic,dynamic>:] for [:Map:]. For non-generic classes [rawType]
-   * is the same as [thisType].
-   *
-   * The [rawType] field is a canonicalization of the raw type and should be
-   * used to distinguish explicit and implicit uses of the [dynamic]
-   * type arguments. For instance should [:List:] be the [rawType] of the
-   * [:List:] class element whereas [:List<dynamic>:] should be its own
-   * instantiation of [InterfaceType] with [:dynamic:] as type argument. Using
-   * this distinction, we can print the raw type with type arguments only when
-   * the input source has used explicit type arguments.
-   *
-   * This type is computed together with [thisType] in [computeType].
-   */
-  T rawTypeCache;
-
-  T get thisType {
-    assert(invariant(this, thisTypeCache != null,
-                     message: 'This type has not been computed for $this'));
-    return thisTypeCache;
-  }
-
-  T get rawType {
-    assert(invariant(this, rawTypeCache != null,
-                     message: 'Raw type has not been computed for $this'));
-    return rawTypeCache;
-  }
-
-  T createType(List<DartType> typeArguments);
-
-  void setThisAndRawTypes(Compiler compiler, List<DartType> typeParameters) {
-    assert(invariant(this, thisTypeCache == null,
-        message: "This type has already been set on $this."));
-    assert(invariant(this, rawTypeCache == null,
-        message: "Raw type has already been set on $this."));
-    thisTypeCache = createType(typeParameters);
-    if (typeParameters.isEmpty) {
-      rawTypeCache = thisTypeCache;
-    } else {
-      List<DartType> dynamicParameters =
-          new List.filled(typeParameters.length, const DynamicType());
-      rawTypeCache = createType(dynamicParameters);
-    }
-  }
-
-  List<DartType> get typeVariables => thisType.typeArguments;
-
-  /**
-   * Creates the type variables, their type and corresponding element, for the
-   * type variables declared in [parameter] on [element]. The bounds of the type
-   * variables are not set until [element] has been resolved.
-   */
-  List<DartType> createTypeVariables(NodeList parameters) {
-    if (parameters == null) return const <DartType>[];
-
-    // Create types and elements for type variable.
-    Link<Node> nodes = parameters.nodes;
-    List<DartType> arguments =
-        new List.generate(nodes.slowLength(), (_) {
-      TypeVariable node = nodes.head;
-      String variableName = node.name.source;
-      nodes = nodes.tail;
-      TypeVariableElementX variableElement =
-          new TypeVariableElementX(variableName, this, node);
-      TypeVariableType variableType = new TypeVariableType(variableElement);
-      variableElement.typeCache = variableType;
-      return variableType;
-    }, growable: false);
-    return arguments;
-  }
-
-  bool get isResolved => resolutionState == STATE_DONE;
-}
-
-abstract class BaseClassElementX extends ElementX
-    with AstElementMixin,
-         AnalyzableElementX,
-         TypeDeclarationElementX<InterfaceType>,
-         PatchMixin<ClassElement>,
-         ClassMemberMixin
-    implements ClassElement {
-  final int id;
-
-  DartType supertype;
-  Link<DartType> interfaces;
-  String nativeTagInfo;
-  int supertypeLoadState;
-  int resolutionState;
-  bool isProxy = false;
-  bool hasIncompleteHierarchy = false;
-
-  // backendMembers are members that have been added by the backend to simplify
-  // compilation. They don't have any user-side counter-part.
-  Link<Element> backendMembers = const Link<Element>();
-
-  OrderedTypeSet allSupertypesAndSelf;
-
-  Link<DartType> get allSupertypes => allSupertypesAndSelf.supertypes;
-
-  int get hierarchyDepth => allSupertypesAndSelf.maxDepth;
-
-  BaseClassElementX(String name,
-                    Element enclosing,
-                    this.id,
-                    int initialState)
-      : supertypeLoadState = initialState,
-        resolutionState = initialState,
-        super(name, ElementKind.CLASS, enclosing);
-
-  int get hashCode => id;
-
-  bool get hasBackendMembers => !backendMembers.isEmpty;
-
-  bool get isUnnamedMixinApplication => false;
-
-  InterfaceType computeType(Compiler compiler) {
-    if (thisTypeCache == null) {
-      computeThisAndRawType(compiler, computeTypeParameters(compiler));
-    }
-    return thisTypeCache;
-  }
-
-  void computeThisAndRawType(Compiler compiler, List<DartType> typeVariables) {
-    if (thisTypeCache == null) {
-      if (origin == null) {
-        setThisAndRawTypes(compiler, typeVariables);
-      } else {
-        thisTypeCache = origin.computeType(compiler);
-        rawTypeCache = origin.rawType;
-      }
-    }
-  }
-
-  InterfaceType createType(List<DartType> typeArguments) {
-    return new InterfaceType(this, typeArguments);
-  }
-
-  List<DartType> computeTypeParameters(Compiler compiler);
-
-  InterfaceType asInstanceOf(ClassElement cls) {
-    if (cls == this) return thisType;
-    return allSupertypesAndSelf.asInstanceOf(cls);
-  }
-
-  bool get isObject {
-    assert(invariant(this, isResolved,
-        message: "isObject has not been computed for $this."));
-    return supertype == null;
-  }
-
-  void ensureResolved(Compiler compiler) {
-    if (resolutionState == STATE_NOT_STARTED) {
-      compiler.resolver.resolveClass(this);
-    }
-  }
-
-  void setDefaultConstructor(FunctionElement constructor, Compiler compiler);
-
-  void addBackendMember(Element member) {
-    // TODO(ngeoffray): Deprecate this method.
-    assert(member.isGenerativeConstructorBody);
-    backendMembers = backendMembers.prepend(member);
-  }
-
-  void reverseBackendMembers() {
-    backendMembers = backendMembers.reverse();
-  }
-
-  /**
-   * Lookup local members in the class. This will ignore constructors.
-   */
-  Element lookupLocalMember(String memberName) {
-    var result = localLookup(memberName);
-    if (result != null && result.isConstructor) return null;
-    return result;
-  }
-
-  /// Lookup a synthetic element created by the backend.
-  Element lookupBackendMember(String memberName) {
-    for (Element element in backendMembers) {
-      if (element.name == memberName) {
-        return element;
-      }
-    }
-    return null;
-  }
-  /**
-   * Lookup super members for the class. This will ignore constructors.
-   */
-  Element lookupSuperMember(String memberName) {
-    return lookupSuperMemberInLibrary(memberName, library);
-  }
-
-  /**
-   * Lookup super members for the class that is accessible in [library].
-   * This will ignore constructors.
-   */
-  Element lookupSuperMemberInLibrary(String memberName,
-                                     LibraryElement library) {
-    bool isPrivate = isPrivateName(memberName);
-    for (ClassElement s = superclass; s != null; s = s.superclass) {
-      // Private members from a different library are not visible.
-      if (isPrivate && !identical(library, s.library)) continue;
-      Element e = s.lookupLocalMember(memberName);
-      if (e == null) continue;
-      // Static members are not inherited.
-      if (e.isStatic) continue;
-      return e;
-    }
-    return null;
-  }
-
-  /**
-   * Find the first member in the class chain with the given [selector].
-   *
-   * This method is NOT to be used for resolving
-   * unqualified sends because it does not implement the scoping
-   * rules, where library scope comes before superclass scope.
-   *
-   * When called on the implementation element both members declared in the
-   * origin and the patch class are returned.
-   */
-  Element lookupSelector(Selector selector) {
-    return internalLookupSelector(selector, false);
-  }
-
-  Element lookupSuperSelector(Selector selector) {
-    return internalLookupSelector(selector, true);
-  }
-
-  Element internalLookupSelector(Selector selector,
-                                 bool isSuperLookup) {
-    String name = selector.name;
-    bool isPrivate = isPrivateName(name);
-    LibraryElement library = selector.library;
-    for (ClassElement current = isSuperLookup ? superclass : this;
-         current != null;
-         current = current.superclass) {
-      Element member = current.lookupLocalMember(name);
-      if (member == null && current.isPatched) {
-        // Doing lookups on selectors is done after resolution, so it
-        // is safe to look in the patch class.
-        member = current.patch.lookupLocalMember(name);
-      }
-      if (member == null) continue;
-      // Private members from a different library are not visible.
-      if (isPrivate && !identical(library, member.library)) continue;
-      // Static members are not inherited.
-      if (member.isStatic && !identical(this, current)) continue;
-      // If we find an abstract field we have to make sure that it has
-      // the getter or setter part we're actually looking
-      // for. Otherwise, we continue up the superclass chain.
-      if (member.isAbstractField) {
-        AbstractFieldElement field = member;
-        FunctionElement getter = field.getter;
-        FunctionElement setter = field.setter;
-        if (selector.isSetter) {
-          // Abstract members can be defined in a super class.
-          if (setter != null && !setter.isAbstract) return setter;
-        } else {
-          assert(selector.isGetter || selector.isCall);
-          if (getter != null && !getter.isAbstract) return getter;
-        }
-      // Abstract members can be defined in a super class.
-      } else if (!member.isAbstract) {
-        return member;
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Find the first member in the class chain with the given
-   * [memberName]. This method is NOT to be used for resolving
-   * unqualified sends because it does not implement the scoping
-   * rules, where library scope comes before superclass scope.
-   */
-  Element lookupMember(String memberName) {
-    Element localMember = lookupLocalMember(memberName);
-    return localMember == null ? lookupSuperMember(memberName) : localMember;
-  }
-
-  /**
-   * Returns true if the [fieldMember] shadows another field.  The given
-   * [fieldMember] must be a member of this class, i.e. if there is a field of
-   * the same name in the superclass chain.
-   *
-   * This method also works if the [fieldMember] is private.
-   */
-  bool hasFieldShadowedBy(Element fieldMember) {
-    assert(fieldMember.isField);
-    String fieldName = fieldMember.name;
-    bool isPrivate = isPrivateName(fieldName);
-    LibraryElement memberLibrary = fieldMember.library;
-    ClassElement lookupClass = this.superclass;
-    while (lookupClass != null) {
-      Element foundMember = lookupClass.lookupLocalMember(fieldName);
-      if (foundMember != null) {
-        if (foundMember.isField) {
-          if (!isPrivate || memberLibrary == foundMember.library) {
-            // Private fields can only be shadowed by a field declared in the
-            // same library.
-            return true;
-          }
-        }
-      }
-      lookupClass = lookupClass.superclass;
-    }
-    return false;
-  }
-
-  Element validateConstructorLookupResults(Selector selector,
-                                           Element result,
-                                           Element noMatch(Element)) {
-    if (result == null
-        || !result.isConstructor
-        || (isPrivateName(selector.name)
-            && result.library != selector.library)) {
-      result = noMatch != null ? noMatch(result) : null;
-    }
-    return result;
-  }
-
-  // TODO(aprelev@gmail.com): Peter believes that it would be great to
-  // make noMatch a required argument. Peter's suspicion is that most
-  // callers of this method would benefit from using the noMatch method.
-  Element lookupConstructor(Selector selector, [Element noMatch(Element)]) {
-    Element result = localLookup(selector.name);
-    return validateConstructorLookupResults(selector, result, noMatch);
-  }
-
-  Link<Element> get constructors {
-    // TODO(ajohnsen): See if we can avoid this method at some point.
-    Link<Element> result = const Link<Element>();
-    // TODO(johnniwinther): Should we include injected constructors?
-    forEachMember((_, Element member) {
-      if (member.isConstructor) result = result.prepend(member);
-    });
-    return result;
-  }
-
-  /**
-   * Returns the super class, if any.
-   *
-   * The returned element may not be resolved yet.
-   */
-  ClassElement get superclass {
-    assert(supertypeLoadState == STATE_DONE);
-    return supertype == null ? null : supertype.element;
-  }
-
-  /**
-   * Runs through all members of this class.
-   *
-   * The enclosing class is passed to the callback. This is useful when
-   * [includeSuperAndInjectedMembers] is [:true:].
-   *
-   * When called on an implementation element both the members in the origin
-   * and patch class are included.
-   */
-  // TODO(johnniwinther): Clean up lookup to get rid of the include predicates.
-  void forEachMember(void f(ClassElement enclosingClass, Element member),
-                     {includeBackendMembers: false,
-                      includeSuperAndInjectedMembers: false}) {
-    bool includeInjectedMembers = includeSuperAndInjectedMembers || isPatch;
-    ClassElement classElement = declaration;
-    do {
-      // Iterate through the members in textual order, which requires
-      // to reverse the data structure [localMembers] we created.
-      // Textual order may be important for certain operations, for
-      // example when emitting the initializers of fields.
-      classElement.forEachLocalMember((e) => f(classElement, e));
-      if (includeBackendMembers) {
-        classElement.forEachBackendMember((e) => f(classElement, e));
-      }
-      if (includeInjectedMembers) {
-        if (classElement.patch != null) {
-          classElement.patch.forEachLocalMember((e) {
-            if (!e.isPatch) f(classElement, e);
-          });
-        }
-      }
-      classElement = includeSuperAndInjectedMembers
-          ? classElement.superclass
-          : null;
-    } while (classElement != null);
-  }
-
-  /**
-   * Runs through all instance-field members of this class.
-   *
-   * The enclosing class is passed to the callback. This is useful when
-   * [includeSuperAndInjectedMembers] is [:true:].
-   *
-   * When called on the implementation element both the fields declared in the
-   * origin and in the patch are included.
-   */
-  void forEachInstanceField(void f(ClassElement enclosingClass,
-                                   FieldElement field),
-                            {bool includeSuperAndInjectedMembers: false}) {
-    // Filters so that [f] is only invoked with instance fields.
-    void fieldFilter(ClassElement enclosingClass, Element member) {
-      if (member.isInstanceMember && member.kind == ElementKind.FIELD) {
-        f(enclosingClass, member);
-      }
-    }
-
-    forEachMember(fieldFilter,
-        includeSuperAndInjectedMembers: includeSuperAndInjectedMembers);
-  }
-
-  /// Similar to [forEachInstanceField] but visits static fields.
-  void forEachStaticField(void f(ClassElement enclosingClass, Element field)) {
-    // Filters so that [f] is only invoked with static fields.
-    void fieldFilter(ClassElement enclosingClass, Element member) {
-      if (!member.isInstanceMember && member.kind == ElementKind.FIELD) {
-        f(enclosingClass, member);
-      }
-    }
-
-    forEachMember(fieldFilter);
-  }
-
-  void forEachBackendMember(void f(Element member)) {
-    backendMembers.forEach(f);
-  }
-
-  bool implementsInterface(ClassElement intrface) {
-    for (DartType implementedInterfaceType in allSupertypes) {
-      ClassElement implementedInterface = implementedInterfaceType.element;
-      if (identical(implementedInterface, intrface)) {
-        return true;
-      }
-    }
-    return false;
-  }
-
-  /**
-   * Returns true if [this] is a subclass of [cls].
-   *
-   * This method is not to be used for checking type hierarchy and
-   * assignments, because it does not take parameterized types into
-   * account.
-   */
-  bool isSubclassOf(ClassElement cls) {
-    // Use [declaration] for both [this] and [cls], because
-    // declaration classes hold the superclass hierarchy.
-    cls = cls.declaration;
-    for (ClassElement s = declaration; s != null; s = s.superclass) {
-      if (identical(s, cls)) return true;
-    }
-    return false;
-  }
-
-  bool get isNative => nativeTagInfo != null;
-
-  void setNative(String name) {
-    // TODO(johnniwinther): Assert that this is only called once. The memory
-    // compiler copies pre-processed elements into a new compiler through
-    // [Compiler.onLibraryScanned] and thereby causes multiple calls to this
-    // method.
-    assert(invariant(this, nativeTagInfo == null || nativeTagInfo == name,
-        message: "Native tag info set inconsistently on $this: "
-                 "Existing name '$nativeTagInfo', new name '$name'."));
-    nativeTagInfo = name;
-  }
-
-  FunctionType get callType {
-    MemberSignature member =
-        lookupInterfaceMember(const PublicName(Compiler.CALL_OPERATOR_NAME));
-    return member != null && member.isMethod ? member.type : null;
-  }
-
-  // TODO(johnniwinther): Remove these when issue 18630 is fixed.
-  ClassElement get patch => super.patch;
-  ClassElement get origin => super.origin;
-
-  // A class declaration is defined by the declaration element.
-  AstElement get definingElement => declaration;
-}
-
-abstract class ClassElementX extends BaseClassElementX {
-  Link<Element> localMembersReversed = const Link<Element>();
-  final ScopeX localScope = new ScopeX();
-
-  Link<Element> localMembersCache;
-
-  Link<Element> get localMembers {
-    if (localMembersCache == null) {
-      localMembersCache = localMembersReversed.reverse();
-    }
-    return localMembersCache;
-  }
-
-  ClassElementX(String name, Element enclosing, int id, int initialState)
-      : super(name, enclosing, id, initialState);
-
-  ClassNode parseNode(Compiler compiler);
-
-  bool get isMixinApplication => false;
-  bool get hasLocalScopeMembers => !localScope.isEmpty;
-
-  void addMember(Element element, DiagnosticListener listener) {
-    localMembersCache = null;
-    localMembersReversed = localMembersReversed.prepend(element);
-    addToScope(element, listener);
-  }
-
-  void addToScope(Element element, DiagnosticListener listener) {
-    if (element.isField && element.name == name) {
-      listener.reportError(element, MessageKind.MEMBER_USES_CLASS_NAME);
-    }
-    localScope.add(element, listener);
-  }
-
-  Element localLookup(String elementName) {
-    Element result = localScope.lookup(elementName);
-    if (result == null && isPatch) {
-      result = origin.localLookup(elementName);
-    }
-    return result;
-  }
-
-  void forEachLocalMember(void f(Element member)) {
-    localMembers.forEach(f);
-  }
-
-  bool get hasConstructor {
-    // Search in scope to be sure we search patched constructors.
-    for (var element in localScope.values) {
-      if (element.isConstructor) return true;
-    }
-    return false;
-  }
-
-  void setDefaultConstructor(FunctionElement constructor, Compiler compiler) {
-    // The default constructor, although synthetic, is part of a class' API.
-    addMember(constructor, compiler);
-  }
-
-  List<DartType> computeTypeParameters(Compiler compiler) {
-    ClassNode node = parseNode(compiler);
-    return createTypeVariables(node.typeParameters);
-  }
-
-  Scope buildScope() => new ClassScope(enclosingElement.buildScope(), this);
-
-  String toString() {
-    if (origin != null) {
-      return 'patch ${super.toString()}';
-    } else if (patch != null) {
-      return 'origin ${super.toString()}';
-    } else {
-      return super.toString();
-    }
-  }
-}
-
-class MixinApplicationElementX extends BaseClassElementX
-    implements MixinApplicationElement {
-  final Node node;
-  final Modifiers modifiers;
-
-  Link<FunctionElement> constructors = new Link<FunctionElement>();
-
-  InterfaceType mixinType;
-
-  MixinApplicationElementX(String name, Element enclosing, int id,
-                           this.node, this.modifiers)
-      : super(name, enclosing, id, STATE_NOT_STARTED);
-
-  ClassElement get mixin => mixinType != null ? mixinType.element : null;
-
-  bool get isMixinApplication => true;
-  bool get isUnnamedMixinApplication => node is! NamedMixinApplication;
-  bool get hasConstructor => !constructors.isEmpty;
-  bool get hasLocalScopeMembers => !constructors.isEmpty;
-
-  get patch => null;
-  get origin => null;
-
-  bool get hasNode => true;
-
-  Token get position => node.getBeginToken();
-
-  Node parseNode(DiagnosticListener listener) => node;
-
-  FunctionElement lookupLocalConstructor(String name) {
-    for (Link<Element> link = constructors;
-         !link.isEmpty;
-         link = link.tail) {
-      if (link.head.name == name) return link.head;
-    }
-    return null;
-  }
-
-  Element localLookup(String name) {
-    Element constructor = lookupLocalConstructor(name);
-    if (constructor != null) return constructor;
-    if (mixin == null) return null;
-    Element mixedInElement = mixin.localLookup(name);
-    if (mixedInElement == null) return null;
-    return mixedInElement.isInstanceMember ? mixedInElement : null;
-  }
-
-  void forEachLocalMember(void f(Element member)) {
-    constructors.forEach(f);
-    if (mixin != null) mixin.forEachLocalMember((Element mixedInElement) {
-      if (mixedInElement.isInstanceMember) f(mixedInElement);
-    });
-  }
-
-  void addMember(Element element, DiagnosticListener listener) {
-    throw new UnsupportedError("Cannot add member to $this.");
-  }
-
-  void addToScope(Element element, DiagnosticListener listener) {
-    listener.internalError(this, 'Cannot add to scope of $this.');
-  }
-
-  void addConstructor(FunctionElement constructor) {
-    constructors = constructors.prepend(constructor);
-  }
-
-  void setDefaultConstructor(FunctionElement constructor, Compiler compiler) {
-    assert(!hasConstructor);
-    addConstructor(constructor);
-  }
-
-  List<DartType> computeTypeParameters(Compiler compiler) {
-    NamedMixinApplication named = node.asNamedMixinApplication();
-    if (named == null) {
-      throw new SpannableAssertionFailure(node,
-          "Type variables on unnamed mixin applications must be set on "
-          "creation.");
-    }
-    return createTypeVariables(named.typeParameters);
-  }
-
-  accept(ElementVisitor visitor) => visitor.visitMixinApplicationElement(this);
-}
-
-class LabelDefinitionX implements LabelDefinition {
-  final Label label;
-  final String labelName;
-  final JumpTarget target;
-  bool isBreakTarget = false;
-  bool isContinueTarget = false;
-
-  LabelDefinitionX(Label label, String labelName, this.target)
-      : this.label = label,
-        this.labelName = labelName;
-
-  // In case of a synthetic label, just use [labelName] for identifying the
-  // label.
-  String get name => label == null ? labelName : label.identifier.source;
-
-  void setBreakTarget() {
-    isBreakTarget = true;
-    target.isBreakTarget = true;
-  }
-
-  void setContinueTarget() {
-    isContinueTarget = true;
-    target.isContinueTarget = true;
-  }
-
-  bool get isTarget => isBreakTarget || isContinueTarget;
-
-  String toString() => 'Label:${name}';
-}
-
-class JumpTargetX implements JumpTarget {
-  final ExecutableElement executableContext;
-  final Node statement;
-  final int nestingLevel;
-  Link<LabelDefinition> labels = const Link<LabelDefinition>();
-  bool isBreakTarget = false;
-  bool isContinueTarget = false;
-
-  JumpTargetX(this.statement, this.nestingLevel, this.executableContext);
-
-  String get name => "target";
-
-  bool get isTarget => isBreakTarget || isContinueTarget;
-
-  LabelDefinition addLabel(Label label, String labelName) {
-    LabelDefinition result = new LabelDefinitionX(label, labelName, this);
-    labels = labels.prepend(result);
-    return result;
-  }
-
-  bool get isSwitch => statement is SwitchStatement;
-
-  String toString() => 'Target:$statement';
-}
-
-class TypeVariableElementX extends ElementX with AstElementMixin
-    implements TypeVariableElement {
-  final Node node;
-  TypeVariableType typeCache;
-  DartType boundCache;
-
-  TypeVariableElementX(String name, TypeDeclarationElement enclosing, this.node)
-    : super(name, ElementKind.TYPE_VARIABLE, enclosing);
-
-  TypeDeclarationElement get typeDeclaration => enclosingElement;
-
-  TypeVariableType computeType(compiler) => type;
-
-  TypeVariableType get type {
-    assert(invariant(this, typeCache != null,
-        message: "Type has not been set on $this."));
-    return typeCache;
-  }
-
-  DartType get bound {
-    assert(invariant(this, boundCache != null,
-        message: "Bound has not been set on $this."));
-    return boundCache;
-  }
-
-  bool get hasNode => true;
-
-  Node parseNode(compiler) => node;
-
-  String toString() => "${enclosingElement.toString()}.${name}";
-
-  Token get position => node.getBeginToken();
-
-  accept(ElementVisitor visitor) => visitor.visitTypeVariableElement(this);
-
-  // A type variable cannot be patched therefore defines itself.
-  AstElement get definingElement => this;
-}
-
-/**
- * A single metadata annotation.
- *
- * For example, consider:
- *
- *     class Data {
- *       const Data();
- *     }
- *
- *     const data = const Data();
- *
- *     @data
- *     class Foo {}
- *
- *     @data @data
- *     class Bar {}
- *
- * In this example, there are three instances of [MetadataAnnotation]
- * and they correspond each to a location in the source code where
- * there is an at-sign, '@'. The [constant] of each of these instances
- * are the same compile-time constant, [: const Data() :].
- *
- * The mirror system does not have a concept matching this class.
- */
-abstract class MetadataAnnotationX implements MetadataAnnotation {
-  /**
-   * The compile-time constant which this annotation resolves to.
-   * In the mirror system, this would be an object mirror.
-   */
-  ConstantExpression constant;
-  Element annotatedElement;
-  int resolutionState;
-
-  /**
-   * The beginning token of this annotation, or [:null:] if it is synthetic.
-   */
-  Token get beginToken;
-
-  MetadataAnnotationX([this.resolutionState = STATE_NOT_STARTED]);
-
-  MetadataAnnotation ensureResolved(Compiler compiler) {
-    if (annotatedElement.isClass || annotatedElement.isTypedef) {
-      TypeDeclarationElement typeDeclaration = annotatedElement;
-      typeDeclaration.ensureResolved(compiler);
-    }
-    if (resolutionState == STATE_NOT_STARTED) {
-      compiler.resolver.resolveMetadataAnnotation(this);
-    }
-    return this;
-  }
-
-  Node parseNode(DiagnosticListener listener);
-
-  String toString() => 'MetadataAnnotation($constant, $resolutionState)';
-}
-
-/// Metadata annotation on a parameter.
-class ParameterMetadataAnnotation extends MetadataAnnotationX {
-  final Metadata metadata;
-
-  ParameterMetadataAnnotation(Metadata this.metadata);
-
-  Node parseNode(DiagnosticListener listener) => metadata.expression;
-
-  Token get beginToken => metadata.getBeginToken();
-
-  Token get endToken => metadata.getEndToken();
-
-  bool get hasNode => true;
-
-  Metadata get node => metadata;
-}
-
-/// Mixin for the implementation of patched elements.
-///
-/// See [:patch_parser.dart:] for a description of the terminology.
-abstract class PatchMixin<E extends Element> implements Element {
-  // TODO(johnniwinther): Use type variables when issue 18630 is fixed.
-  Element/*E*/ patch = null;
-  Element/*E*/ origin = null;
-
-  bool get isPatch => origin != null;
-  bool get isPatched => patch != null;
-
-  bool get isImplementation => !isPatched;
-  bool get isDeclaration => !isPatch;
-
-  Element/*E*/ get implementation => isPatched ? patch : this;
-  Element/*E*/ get declaration => isPatch ? origin : this;
-
-  /// Applies a patch to this element. This method must be called at most once.
-  void applyPatch(PatchMixin<E> patch) {
-    assert(invariant(this, this.patch == null,
-                     message: "Element is patched twice."));
-    assert(invariant(this, this.origin == null,
-                     message: "Origin element is a patch."));
-    assert(invariant(patch, patch.origin == null,
-                     message: "Element is patched twice."));
-    assert(invariant(patch, patch.patch == null,
-                     message: "Patch element is patched."));
-    this.patch = patch;
-    patch.origin = this;
-  }
-}
-
-/// Abstract implementation of the [AstElement] interface.
-abstract class AstElementMixin implements AstElement {
-  /// The element whose node defines this element.
-  ///
-  /// For patched functions the defining element is the patch element found
-  /// through [implementation] since its node define the implementation of the
-  /// function. For patched classes the defining element is the origin element
-  /// found through [declaration] since its node define the inheritance relation
-  /// for the class. For unpatched elements the defining element is the element
-  /// itself.
-  AstElement get definingElement;
-
-  bool get hasResolvedAst => definingElement.hasTreeElements;
-
-  ResolvedAst get resolvedAst {
-    return new ResolvedAst(declaration,
-        definingElement.node, definingElement.treeElements);
-  }
-
-}