Prepare for decoupling analyzer ASTs from element model.

pkg/analysis_server/lib/src/services/correction/namespace.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 services.src.correction.namespace;
 
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/resolution_accessors.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/resolver/scope.dart';
 
 /**
  * Returns the [Element] exported from the given [LibraryElement].
  */
 Element getExportedElement(LibraryElement library, String name) {
   if (library == null) {
     return null;
   }
@@ skipping 116 matching lines @@
 /**
  * Returns the [ImportElementInfo] with the [ImportElement] that is referenced
  * by [prefixNode] with a [PrefixElement], maybe `null`.
  */
 ImportElementInfo internal_getImportElementInfo(SimpleIdentifier prefixNode) {
   ImportElementInfo info = new ImportElementInfo();
   // prepare environment
   AstNode parent = prefixNode.parent;
   CompilationUnit unit =
       prefixNode.getAncestor((node) => node is CompilationUnit);
-  LibraryElement libraryElement = unit.element.library;
+  LibraryElement libraryElement = elementForCompilationUnit(unit).library;
   // prepare used element
   Element usedElement = null;
   if (parent is PrefixedIdentifier) {
     PrefixedIdentifier prefixed = parent;
     if (prefixed.prefix == prefixNode) {
       usedElement = prefixed.staticElement;
       info.periodEnd = prefixed.period.end;
     }
   }
   if (parent is MethodInvocation) {
@@ skipping 19 matching lines @@
 }
 
 /**
  * Information about [ImportElement] and place where it is referenced using
  * [PrefixElement].
  */
 class ImportElementInfo {
   ImportElement element;
   int periodEnd;
 }