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

pkg/analyzer/lib/src/summary/idl.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.
 
 /**
  * This file is an "idl" style description of the summary format.  It
  * contains abstract classes which declare the interface for reading data from
  * summaries.  It is parsed and transformed into code that implements the
  * summary format.
  *
@@ skipping 323 matching lines @@
   loadLibrary,
 
   /**
    * The synthetic `index` getter of an enum.
    */
   enumIndex,
 
   /**
    * The synthetic `values` getter of an enum.
    */
-  enumValues
+  enumValues,
+
+  /**
+   * The containing unit itself.
+   */
+  unit
 }
 
 /**
  * Information about a dependency that exists between one library and another
  * due to an "import" declaration.
  */
 abstract class LinkedDependency extends base.SummaryClass {
   /**
    * URI for the compilation units listed in the library's `part` declarations.
    * These URIs are relative to the importing library.
@@ skipping 2324 matching lines @@
    */
   @Id(11)
   int get visibleLength;
 
   /**
    * If a local variable, the beginning of the visible range; zero otherwise.
    */
   @Id(12)
   int get visibleOffset;
 }