Issue dartdoc#1124. Get used elements from directive comments.

pkg/analyzer/test/src/task/dart_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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 2209 matching lines @@
             .evaluationResult,
         isNotNull);
   }
 }
 
 @reflectiveTest
 class GatherUsedImportedElementsTaskTest extends _AbstractDartTaskTest {
   UsedImportedElements usedElements;
   Set<String> usedElementNames;
 
-  test_perform() {
+  test_perform_inBody() {
     newSource(
         '/a.dart',
         r'''
 library lib_a;
 class A {}
 ''');
     newSource(
         '/b.dart',
         r'''
 library lib_b;
 class B {}
 ''');
     Source source = newSource(
         '/test.dart',
         r'''
 import 'a.dart';
 import 'b.dart';
 main() {
   new A();
 }''');
     _computeUsedElements(source);
     // validate
     expect(usedElementNames, unorderedEquals(['A']));
   }
 
+  test_perform_inComment_exportDirective() {
+    Source source = newSource(
+        '/test.dart',
+        r'''
+import 'dart:async';
+/// Use [Future].
+export 'dart:math';
+''');
+    _computeUsedElements(source);
+    expect(usedElementNames, unorderedEquals(['Future']));
+  }
+
+  test_perform_inComment_importDirective() {
+    Source source = newSource(
+        '/test.dart',
+        r'''
+import 'dart:async';
+/// Use [Future].
+import 'dart:math';
+''');
+    _computeUsedElements(source);
+    expect(usedElementNames, unorderedEquals(['Future']));
+  }
+
+  test_perform_inComment_libraryDirective() {
+    Source source = newSource(
+        '/test.dart',
+        r'''
+/// Use [Future].
+library test;
+import 'dart:async';
+''');
+    _computeUsedElements(source);
+    expect(usedElementNames, unorderedEquals(['Future']));
+  }
+
+  test_perform_inComment_topLevelFunction() {
+    Source source = newSource(
+        '/test.dart',
+        r'''
+import 'dart:async';
+/// Use [Future].
+main() {}
+''');
+    _computeUsedElements(source);
+    expect(usedElementNames, unorderedEquals(['Future']));
+  }
+
   void _computeUsedElements(Source source) {
     LibrarySpecificUnit target = new LibrarySpecificUnit(source, source);
     computeResult(target, USED_IMPORTED_ELEMENTS,
         matcher: isGatherUsedImportedElementsTask);
     usedElements = outputs[USED_IMPORTED_ELEMENTS];
     usedElementNames = usedElements.elements.map((e) => e.name).toSet();
   }
 }
 
 @reflectiveTest
@@ skipping 2770 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result];
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }