Issue 23389. Report error in the renamed element be invisible after rename.

pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart

Index: pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart
diff --git a/pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart b/pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart
index 51f27c477f08c2c93a230730ce32848e3dd505b1..cabfb4d8d2545fbff9331edc69b0b453938479dc 100644
--- a/pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart
+++ b/pkg/analysis_server/lib/src/services/refactoring/rename_unit_member.dart
@@ -15,6 +15,7 @@ import 'package:analysis_server/src/services/refactoring/refactoring.dart';
 import 'package:analysis_server/src/services/refactoring/rename.dart';
 import 'package:analysis_server/src/services/search/element_visitors.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
+import 'package:analyzer/src/generated/ast.dart' show Identifier;
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 
@@ -127,13 +128,14 @@ class _RenameUnitMemberValidator {
   _RenameUnitMemberValidator.forRename(
       this.searchEngine, this.element, this.name)
       : isRename = true {
-    library = element.getAncestor((e) => e is LibraryElement);
+    library = element.library;
     elementKind = element.kind;
   }
 
   Future<RefactoringStatus> validate() async {
     _validateWillConflict();
     if (isRename) {
+      await _validateWillBeInvisible();
       await _validateWillBeShadowed();
     }
     await _validateWillShadow();
@@ -165,15 +167,31 @@ class _RenameUnitMemberValidator {
   }
 
   /**
-   * Validates if any usage of [element] renamed to [name] will be shadowed.
+   * Validates if any usage of [element] renamed to [name] will be invisible.
    */
-  Future _validateWillBeShadowed() async {
-    if (!isRename) {
+  Future _validateWillBeInvisible() async {

[Brian Wilkerson, 2015/06/01 17:32:29]

It's sad to see this method duplicated. Could we move it to a base class that
both extend?

+    if (!Identifier.isPrivateName(name)) {
       return;
     }
     List<SearchMatch> references = await searchEngine.searchReferences(element);
     for (SearchMatch reference in references) {
       Element refElement = reference.element;
+      LibraryElement refLibrary = refElement.library;
+      if (refLibrary != library) {
+        String message = format("Renamed {0} will be invisible in '{1}'.",
+            getElementKindName(element), getElementQualifiedName(refLibrary));
+        result.addError(message, newLocation_fromMatch(reference));
+      }
+    }
+  }
+
+  /**
+   * Validates if any usage of [element] renamed to [name] will be shadowed.
+   */
+  Future _validateWillBeShadowed() async {
+    List<SearchMatch> references = await searchEngine.searchReferences(element);
+    for (SearchMatch reference in references) {
+      Element refElement = reference.element;
       ClassElement refClass = refElement.getAncestor((e) => e is ClassElement);
       if (refClass != null) {
         visitChildren(refClass, (shadow) {