Add an UNUSED_SHOWN_NAMES hint to the analyzer

pkg/analyzer/test/src/summary/resynthesize_test.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 test.src.serialization.elements_test;
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/constant/value.dart';
@@ skipping 3144 matching lines @@
     checkLibrary('import "dart:async" hide Stream show Future; Future f;');
   }
 
   test_import_prefixed() {
     addLibrarySource('/a.dart', 'library a; class C {}');
     checkLibrary('import "a.dart" as a; a.C c;');
   }
 
   test_import_show() {
     addLibrary('dart:async');
-    checkLibrary('import "dart:async" show Future, Stream; Future f;');
+    checkLibrary('''
+import "dart:async" show Future, Stream;
+Future f;
+Stream s;
+''');
   }
 
   test_imports() {
     addLibrarySource('/a.dart', 'library a; class C {}');
     addLibrarySource('/b.dart', 'library b; class D {}');
     checkLibrary('import "a.dart"; import "b.dart"; C c; D d;');
   }
 
   test_inferred_function_type_for_variable_in_generic_function() {
     // In the code below, `x` has an inferred type of `() => int`, with 2
@@ skipping 1137 matching lines @@
       fail('Unexpectedly tried to get unlinked summary for $uri');
     }
     return serializedUnit;
   }
 
   @override
   bool hasLibrarySummary(String uri) {
     return true;
   }
 }