Improve type information and minor clean up

pkg/analyzer/lib/src/dart/ast/ast.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.ast.ast;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 877 matching lines @@
     AstNode root = this;
     AstNode parent = this.parent;
     while (parent != null) {
       root = parent;
       parent = root.parent;
     }
     return root;
   }
 
   @override
-  AstNode getAncestor(Predicate<AstNode> predicate) {
+  AstNode/*=E*/ getAncestor/*<E extends AstNode>*/(
+      Predicate<AstNode> predicate) {
     // TODO(brianwilkerson) It is a bug that this method can return `this`.
     AstNode node = this;
     while (node != null && !predicate(node)) {
       node = node.parent;
     }
-    return node;
+    return node as AstNode/*=E*/;
   }
 
   @override
-  Object getProperty(String name) {
+  Object/*=E*/ getProperty/*<E>*/(String name) {
     if (_propertyMap == null) {
       return null;
     }
-    return _propertyMap[name];
+    return _propertyMap[name] as Object/*=E*/;
   }
 
   @override
   void setProperty(String name, Object value) {
     if (value == null) {
       if (_propertyMap != null) {
         _propertyMap.remove(name);
         if (_propertyMap.isEmpty) {
           _propertyMap = null;
         }
@@ skipping 10109 matching lines @@
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
       visitor.visitYieldStatement(this);
 
   @override
   void visitChildren(AstVisitor visitor) {
     _expression?.accept(visitor);
   }
 }