Issue 20890. Fix for NPE in the 'Add show' QA.

pkg/analysis_server/test/services/correction/assist_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.correction.assist;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/correction/assist.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
@@ skipping 893 matching lines @@
     assertNoAssistAt('import ', AssistKind.IMPORT_ADD_SHOW);
   }
 
   void test_importAddShow_BAD_unused() {
     _indexTestUnit('''
 import 'dart:math';
 ''');
     assertNoAssistAt('import ', AssistKind.IMPORT_ADD_SHOW);
   }
 
+  void test_importAddShow_OK_hasUnresolvedIdentifier() {
+    _indexTestUnit('''
+import 'dart:math';
+main(x) {
+  PI;
+  return x.foo();
+}
+''');
+    assertHasAssistAt('import ', AssistKind.IMPORT_ADD_SHOW, '''
+import 'dart:math' show PI;
+main(x) {
+  PI;
+  return x.foo();
+}
+''');
+  }
+
   void test_importAddShow_OK_onDirective() {
     _indexTestUnit('''
 import 'dart:math';
 main() {
   PI;
   E;
   max(1, 2);
 }
 ''');
     assertHasAssistAt('import ', AssistKind.IMPORT_ADD_SHOW, '''
@@ skipping 1294 matching lines @@
   void _indexTestUnit(String code) {
     resolveTestUnit(code);
     index.indexUnit(context, testUnit);
   }
 
   void _setStartEndSelection() {
     offset = findOffset('// start\n') + '// start\n'.length;
     length = findOffset('// end') - offset;
   }
 }