Handle clash of prefix/non-prefix imports.

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

 // Copyright (c) 2012, 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;
 
 
 import '../tree/tree.dart';
 import '../util/util.dart';
 import '../resolution/resolution.dart';
@@ skipping 682 matching lines @@
   Element findLocal(SourceString elementName);
   void forEachExport(f(Element element));
 
   bool hasLibraryName();
   String getLibraryOrScriptName();
 
   int compareTo(LibraryElement other);
 }
 
 abstract class PrefixElement extends Element {
-  Map<SourceString, Element> get imported;
+  void addImport(Element element, Import import, DiagnosticListener listener);
   Element lookupLocalMember(SourceString memberName);
 }
 
 abstract class TypedefElement extends Element
     implements TypeDeclarationElement {
   TypedefType get thisType;
   TypedefType get rawType;
   DartType get alias;
   FunctionSignature get functionSignature;
   Link<DartType> get typeVariables;
@@ skipping 259 matching lines @@
   int get resolutionState;
   Token get beginToken;
   Token get endToken;
 
   // TODO(kasperl): Try to get rid of these.
   void set annotatedElement(Element value);
   void set resolutionState(int value);
 
   MetadataAnnotation ensureResolved(Compiler compiler);
 }