Add an UNUSED_SHOWN_NAMES hint to the analyzer

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 2820 matching lines @@
         r'''
 library lib1;
 class A {}
 class B {}''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [HintCode.UNUSED_IMPORT]);
     assertNoErrors(source2);
     verify([source, source2]);
   }
 
+  void test_unusedShownName() {
+    Source source = addSource(r'''
+library L;
+import 'lib1.dart' show A, B;
+A a;''');
+    Source source2 = addNamedSource(
+        "/lib1.dart", r'''
+library lib1;
+class A {}
+class B {}''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [HintCode.UNUSED_SHOWN_NAME]);
+    assertNoErrors(source2);
+    verify([source, source2]);
+  }
+
+  void test_unusedShownName_as() {
+    Source source = addSource(r'''
+library L;
+import 'lib1.dart' as p show A, B;
+p.A a;''');
+    Source source2 = addNamedSource(
+        "/lib1.dart", r'''
+library lib1;
+class A {}
+class B {}''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [HintCode.UNUSED_SHOWN_NAME]);
+    assertNoErrors(source2);
+    verify([source, source2]);
+  }
+
+  void test_unusedShownName_duplicates() {
+    Source source = addSource(r'''
+library L;
+import 'lib1.dart' show A, B;
+import 'lib1.dart' show C, D;
+A a;
+C c;''');
+    Source source2 = addNamedSource(
+        "/lib1.dart", r'''
+library lib1;
+class A {}
+class B {}
+class C {}
+class D {}''');
+    computeLibrarySourceErrors(source);
+    assertErrors(source, [
+        HintCode.UNUSED_SHOWN_NAME,
+        HintCode.UNUSED_SHOWN_NAME]);
+    assertNoErrors(source2);
+    verify([source, source2]);
+  }
+
   void test_unusedLocalVariable_inCatch_exception() {
     enableUnusedLocalVariable = true;
     Source source = addSource(r'''
 main() {
   try {
   } on String catch (exception) {
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(source, [HintCode.UNUSED_CATCH_CLAUSE]);
@@ skipping 248 matching lines @@
   n() {
     var a = m(), b = m();
   }
 }''');
     computeLibrarySourceErrors(source);
     assertErrors(
         source, [HintCode.USE_OF_VOID_RESULT, HintCode.USE_OF_VOID_RESULT]);
     verify([source]);
   }
 }