fix code completion import dart exception

pkg/analysis_server/test/services/completion/imported_computer_test.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 test.services.completion.toplevel;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/imported_computer.dart';
 import '../../reflective_tests.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 144 matching lines @@
   }
 
   test_local_name2() {
     addSource('/testA.dart', 'var T1;');
     addTestSource('import "/testA.dart"; class C {a() {var ^}}');
     return computeFull().then((_) {
       assertNotSuggested('T1');
     });
   }
 
+  test_import_dart() {
+    addTestSource('import "dart^"; main() {}');
+    return computeFull().then((_) {
+      assertNotSuggested('T1');
+    });
+  }
+
   test_topLevelVar() {
     addSource('/testA.dart', 'String T1; var _T2;');
     addTestSource('import "/testA.dart"; class C {foo(){^}}');
     return computeFull().then((_) {
       assertSuggestTopLevelVar('T1', 'String');
       assertNotSuggested('_T2');
     });
   }
 
   test_topLevelVar_name() {
@@ skipping 14 matching lines @@
 
   test_topLevelVar_notImported() {
     addSource('/testA.dart', 'var T1; var _T2;');
     addTestSource('class C {foo(){^}}');
     return computeFull(true).then((_) {
       assertSuggestTopLevelVar('T1', null, CompletionRelevance.LOW);
       assertNotSuggested('_T2');
     });
   }
 }