Improve type information and minor clean up

pkg/analyzer/lib/src/dart/element/element.dart

 // Copyright (c) 2014, 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.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2049 matching lines @@
   AstNode computeNode() => getNodeMatching((node) => node is AstNode);
 
   /**
    * Set this element as the enclosing element for given [element].
    */
   void encloseElement(ElementImpl element) {
     element.enclosingElement = this;
   }
 
   @override
-  Element getAncestor(Predicate<Element> predicate) {
+  Element/*=E*/ getAncestor/*<E extends Element >*/(
+      Predicate<Element> predicate) {
     Element ancestor = _enclosingElement;
     while (ancestor != null && !predicate(ancestor)) {
       ancestor = ancestor.enclosingElement;
     }
-    return ancestor;
+    return ancestor as Element/*=E*/;
   }
 
   /**
    * Return the child of this element that is uniquely identified by the given
    * [identifier], or `null` if there is no such child.
    */
   ElementImpl getChild(String identifier) => null;
 
   @override
   String getExtendedDisplayName(String shortName) {
@@ skipping 2060 matching lines @@
   @override
   accept(ElementVisitor visitor) => visitor.visitMultiplyDefinedElement(this);
 
   @override
   String computeDocumentationComment() => null;
 
   @override
   AstNode computeNode() => null;
 
   @override
-  Element getAncestor(Predicate<Element> predicate) => null;
+  Element/*=E*/ getAncestor/*<E extends Element >*/(
+          Predicate<Element> predicate) =>
+      null;
 
   @override
   String getExtendedDisplayName(String shortName) {
     if (shortName != null) {
       return shortName;
     }
     return displayName;
   }
 
   @override
@@ skipping 819 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }