Fix prelinker when a local name shadows an import prefix.

pkg/analyzer/test/src/summary/summary_common.dart

 // Copyright (c) 2015, 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.test.src.summary.summary_common;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
@@ skipping 8862 matching lines @@
     addNamedSource('/a.dart', 'class C {} class D {}');
     serializeLibraryText('''
 import 'a.dart';
 class C {}
 C c;
 D d;''');
     checkTypeRef(findVariable('c').type, null, null, 'C');
     checkTypeRef(findVariable('d').type, absUri('/a.dart'), 'a.dart', 'D');
   }
 
+  test_localNameShadowsImportPrefix() {
+    serializeLibraryText('import "dart:async" as a; class a {}; a x;');
+    checkTypeRef(findVariable('x').type, null, null, 'a');
+  }
+
   test_metadata_classDeclaration() {
     checkAnnotationA(
         serializeClassText('const a = null; @a class C {}').annotations);
   }
 
   test_metadata_classTypeAlias() {
     checkAnnotationA(serializeClassText(
             'const a = null; @a class C = D with E; class D {} class E {}',
             className: 'C')
         .annotations);
@@ skipping 1719 matching lines @@
 class _PrefixExpectation {
   final ReferenceKind kind;
   final String name;
   final String absoluteUri;
   final String relativeUri;
   final int numTypeParameters;
 
   _PrefixExpectation(this.kind, this.name,
       {this.absoluteUri, this.relativeUri, this.numTypeParameters: 0});
 }