Issue 26207. Fix for renaming top-level functions with offset 0.

pkg/analyzer/test/src/summary/index_unit_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.
 
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';
@@ skipping 801 matching lines @@
   print(foo);
   print(foo());
 }
 ''');
     FunctionElement element = findElement('foo');
     assertThat(element)
       ..isReferencedAt('foo);', false)
       ..isInvokedAt('foo());', false);
   }
 
+  void test_isReferencedBy_FunctionElement_with_LibraryElement() {
+    addSource(
+        '/foo.dart',
+        r'''
+bar() {}
+''');
+    _indexTestUnit('''
+import "foo.dart";
+main() {
+  bar();
+}
+''');
+    LibraryElement fooLibrary = testLibraryElement.imports[0].importedLibrary;
+    assertThat(fooLibrary)..isReferencedAt('"foo.dart";', true, length: 10);
+    {
+      FunctionElement bar = fooLibrary.definingCompilationUnit.functions[0];
+      assertThat(bar)..isInvokedAt('bar();', false);
+    }
+  }
+
   void test_isReferencedBy_FunctionTypeAliasElement() {
     _indexTestUnit('''
 typedef A();
 main(A p) {
 }
 ''');
     Element element = findElement('A');
     assertThat(element)..isReferencedAt('A p) {', false);
   }
 
@@ skipping 457 matching lines @@
   final bool isQualified;
 
   _Relation(this.kind, this.offset, this.length, this.isQualified);
 
   @override
   String toString() {
     return '_Relation{kind: $kind, offset: $offset, length: $length, '
         'isQualified: $isQualified}';
   }
 }