Fix for recording 'null' as a defined element.

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/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 2222 matching lines @@
     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
 class GatherUsedLocalElementsTaskTest extends _AbstractDartTaskTest {
+  List<Element> definedElements;
+  Set<String> definedElementNames;
   UsedLocalElements usedElements;
   Set<String> usedElementNames;
 
   test_perform_forPart_afterLibraryUpdate() {
     Source libSource = newSource(
         '/my_lib.dart',
         '''
 library my_lib;
 part 'my_part.dart';
 foo() => null;
@@ skipping 44 matching lines @@
     Source source = newSource(
         '/test.dart',
         r'''
 main() {
   var v1 = 1;
   var v2 = 2;
   print(v2);
 }''');
     _computeUsedElements(source);
     // validate
+    expect(definedElementNames, unorderedEquals(['main', 'v1', 'v2']));
     expect(usedElementNames, unorderedEquals(['v2']));
   }
 
   test_perform_method() {
     Source source = newSource(
         '/test.dart',
         r'''
 class A {
   _m1() {}
   _m2() {}
 }
 
 main(A a, p) {
   a._m2();
   p._m3();
 }
 ''');
     _computeUsedElements(source);
     // validate
+    expect(definedElementNames,
+        unorderedEquals(['A', '_m1', '_m2', 'main', 'a', 'p']));
     expect(usedElementNames, unorderedEquals(['A', 'a', 'p', '_m2']));
     expect(usedElements.members, unorderedEquals(['_m2', '_m3']));
   }
 
+  test_perform_unresolvedImportWithPrefix() {
+    Source source = newSource(
+        '/test.dart',
+        r'''
+import 'x' as p;
+''');
+    _computeUsedElements(source);
+    // validate
+    expect(definedElementNames, isEmpty);
+    expect(usedElementNames, isEmpty);
+  }
+
   void _computeUsedElements(Source source) {
     LibrarySpecificUnit target = new LibrarySpecificUnit(source, source);
     computeResult(target, USED_LOCAL_ELEMENTS,
         matcher: isGatherUsedLocalElementsTask);
+    definedElements = outputs[DEFINED_ELEMENTS];
+    definedElementNames = definedElements.map((e) => e.name).toSet();
     usedElements = outputs[USED_LOCAL_ELEMENTS];
     usedElementNames = usedElements.elements.map((e) => e.name).toSet();
   }
 }
 
 @reflectiveTest
 class GenerateHintsTaskTest extends _AbstractDartTaskTest {
   test_perform_bestPractices_missingReturn() {
     Source source = newSource(
         '/test.dart',
@@ skipping 2594 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);
   }
 }