Improve type information and minor clean up

pkg/analyzer/lib/src/dart/element/member.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.member;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 497 matching lines @@
   @override
   CompilationUnit get unit => _baseElement.unit;
 
   @override
   String computeDocumentationComment() => documentationComment;
 
   @override
   AstNode computeNode() => _baseElement.computeNode();
 
   @override
-  Element getAncestor(Predicate<Element> predicate) =>
+  Element/*=E*/ getAncestor/*<E extends Element >*/(Predicate<Element> predicate) =>
       baseElement.getAncestor(predicate);
 
   @override
   String getExtendedDisplayName(String shortName) =>
       _baseElement.getExtendedDisplayName(shortName);
 
   @override
   bool isAccessibleIn(LibraryElement library) =>
       _baseElement.isAccessibleIn(library);
 
@@ skipping 164 matching lines @@
   @override
   SourceRange get visibleRange => baseElement.visibleRange;
 
   @override
   accept(ElementVisitor visitor) => visitor.visitParameterElement(this);
 
   @override
   FormalParameter computeNode() => baseElement.computeNode();
 
   @override
-  Element getAncestor(Predicate<Element> predicate) {
+  Element/*=E*/ getAncestor/*<E extends Element>*/(Predicate<Element> predicate) {
     Element element = baseElement.getAncestor(predicate);
     ParameterizedType definingType = this.definingType;
     if (definingType is InterfaceType) {
-      InterfaceType definingInterfaceType = definingType;
       if (element is ConstructorElement) {
-        return ConstructorMember.from(element, definingInterfaceType);
+        return ConstructorMember.from(element, definingType) as Element/*=E*/;
       } else if (element is MethodElement) {
-        return MethodMember.from(element, definingInterfaceType);
+        return MethodMember.from(element, definingType) as Element/*=E*/;
       } else if (element is PropertyAccessorElement) {
-        return PropertyAccessorMember.from(element, definingInterfaceType);
+        return PropertyAccessorMember.from(element, definingType) as Element/*=E*/;
       }
     }
-    return element;
+    return element as Element/*=E*/;
   }
 
   @override
   String toString() {
     ParameterElement baseElement = this.baseElement;
     String left = "";
     String right = "";
     while (true) {
       if (baseElement.parameterKind == ParameterKind.NAMED) {
         left = "{";
@@ skipping 312 matching lines @@
   DartObject computeConstantValue() => baseElement.computeConstantValue();
 
   @override
   void visitChildren(ElementVisitor visitor) {
     // TODO(brianwilkerson) We need to finish implementing the accessors used
     // below so that we can safely invoke them.
     super.visitChildren(visitor);
     baseElement.initializer?.accept(visitor);
   }
 }