Fix @protected to include closure references (linter#255).

pkg/analyzer/test/generated/hint_code_test.dart

 // Copyright (c) 2016, 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 analyzer.test.generated.hint_code_test;
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 1087 matching lines @@
 }
 
 abstract class B implements A {
   int b() => a();
 }''');
     computeLibrarySourceErrors(source);
     assertNoErrors(source);
     verify([source]);
   }
 
+  void test_invalidUseOfProtectedMember_closure() {
+    Source source = addSource(r'''
+import 'package:meta/meta.dart';
+
+class A {
+  @protected
+  int a() => 42;
+}
+void main() {
+  var leak = new A().a;
+  print(leak);
+}''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [HintCode.INVALID_USE_OF_PROTECTED_MEMBER]);
+    verify([source]);
+  }
+
   void test_invalidUseOfProtectedMember_getter() {
     Source source = addSource(r'''
 import 'package:meta/meta.dart';
 class A {
   @protected
   int get a => 42;
 }
 class B {
   A a;
   int b() => a.a;
@@ skipping 2343 matching lines @@
   n() {
     var a = m(), b = m();
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [HintCode.USE_OF_VOID_RESULT, HintCode.USE_OF_VOID_RESULT]);
     verify([source]);
   }
 }