Issue 24440. Fix for renaming libraries using 'part of' directives.

pkg/analyzer/test/generated/all_the_rest_test.dart

 // Copyright (c) 2014, 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 engine.all_the_rest_test;
 
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 6950 matching lines @@
     CompilationUnit cu = _resolveContents(code);
     int offset = code.indexOf('foo(0)');
     AstNode node = new NodeLocator(offset).searchWithin(cu);
     MethodInvocation invocation =
         node.getAncestor((n) => n is MethodInvocation);
     Element element = ElementLocator.locate(invocation);
     EngineTestCase.assertInstanceOf(
         (obj) => obj is FunctionElement, FunctionElement, element);
   }
 
+  void test_locate_PartOfDirective() {
+    Source librarySource = addNamedSource(
+        '/lib.dart',
+        '''
+library my.lib;
+part 'part.dart';
+''');
+    Source unitSource = addNamedSource(
+        '/part.dart',
+        '''
+part of my.lib;
+''');
+    CompilationUnit unit =
+        analysisContext.resolveCompilationUnit2(unitSource, librarySource);
+    PartOfDirective partOf = unit.directives.first;
+    Element element = ElementLocator.locate(partOf);
+    EngineTestCase.assertInstanceOf(
+        (obj) => obj is LibraryElement, LibraryElement, element);
+  }
+
   void test_locate_PostfixExpression() {
     AstNode id = _findNodeIn("++", "int addOne(int x) => x++;");
     Element element = ElementLocator.locate(id);
     EngineTestCase.assertInstanceOf(
         (obj) => obj is MethodElement, MethodElement, element);
   }
 
   void test_locate_PrefixedIdentifier() {
     AstNode id = _findNodeIn(
         "int",
@@ skipping 2325 matching lines @@
     if (_expectedExternalScriptName == null) {
       expect(scriptSource, isNull, reason: "script $scriptIndex");
     } else {
       expect(scriptSource, isNotNull, reason: "script $scriptIndex");
       String actualExternalScriptName = scriptSource.shortName;
       expect(actualExternalScriptName, _expectedExternalScriptName,
           reason: "script $scriptIndex");
     }
   }
 }