Handle bad regexs in search.findTopLevelDeclarations.

pkg/analysis_server/test/search/top_level_declarations_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.search.top_level_declarations;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
@@ skipping 21 matching lines @@
     if (result != null) {
       fail('Unexpected: kind=$kind name="$name"\nin\n' + results.join('\n'));
     }
   }
 
   Future findTopLevelDeclarations(String pattern) async {
     await waitForTasksFinished();
     Request request =
         new SearchFindTopLevelDeclarationsParams(pattern).toRequest('0');
     Response response = await waitResponse(request);
+    if (response.error != null) {
+      return response.error;
+    }
     searchId =
         new SearchFindTopLevelDeclarationsResult.fromResponse(response).id;
     return waitForSearchResults();
   }
 
   SearchResult findTopLevelResult(ElementKind kind, String name) {
     for (SearchResult result in results) {
       Element element = result.path[0];
       if (element.kind == kind && element.name == name) {
         return result;
       }
     }
     return null;
   }
 
   test_startEndPattern() async {
     addTestFile('''
 class A {} // A
 class B = Object with A;
 typedef C();
 D() {}
 var E = null;
 class ABC {}
 ''');
+
     await findTopLevelDeclarations('^[A-E]\$');
     assertHasDeclaration(ElementKind.CLASS, 'A');
     assertHasDeclaration(ElementKind.CLASS, 'B');
     assertHasDeclaration(ElementKind.FUNCTION_TYPE_ALIAS, 'C');
     assertHasDeclaration(ElementKind.FUNCTION, 'D');
     assertHasDeclaration(ElementKind.TOP_LEVEL_VARIABLE, 'E');
     assertNoDeclaration(ElementKind.CLASS, 'ABC');
   }
+
+  test_invalidRegex() async {
+    var result = await findTopLevelDeclarations('[A');
+    expect(result, new isInstanceOf<RequestError>());
+  }
 }