remove duplicate suggestions

pkg/analysis_services/test/completion/local_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.dart.local;
 
 import 'package:analysis_services/src/completion/local_computer.dart';
 import 'package:analysis_testing/reflective_tests.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 54 matching lines @@
     assertSuggestVariable('i');
   }
 
   test_forEach() {
     addTestSource('main(args) {for (foo in bar) {^}}');
     expect(computeFast(), isTrue);
     assertSuggestVariable('foo');
   }
 
   test_function() {
-    addTestSource('main(args) {^}');
+    addTestSource('main(args) {x.then((b) {^});}');
     expect(computeFast(), isTrue);
     assertSuggestFunction('main');
     assertSuggestParameter('args');
+    assertSuggestParameter('b');
   }
 
   test_members() {
     addTestSource('class A {var f; a() {^} var g;}');
     expect(computeFast(), isTrue);
     assertSuggestMethodName('a');
     assertSuggestField('f');
     assertSuggestField('g');
   }
 
@@ skipping 14 matching lines @@
   }
 
   test_variableDeclaration() {
     addTestSource('main() {int a = 1, b = 2 + ^;}');
     expect(computeFast(), isTrue);
     assertSuggestVariable('a');
     assertNotSuggested('b');
   }
 }