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

pkg/analyzer/lib/src/summary/index_unit.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 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/member.dart';
@@ skipping 186 matching lines @@
       }
     }
     throw new StateError(element.toString());
   }
 
   /**
    * Return a new [ElementInfo] for the given [element] in the given [unitId].
    * This method is static, so it cannot add any information to the index.
    */
   static ElementInfo newElementInfo(int unitId, Element element) {
+    int offset = null;
     IndexSyntheticElementKind kind = IndexSyntheticElementKind.notSynthetic;
     if (element.isSynthetic) {
       if (element is ConstructorElement) {
         kind = IndexSyntheticElementKind.constructor;
         element = element.enclosingElement;
       } else if (element is FunctionElement && element.name == 'loadLibrary') {
         kind = IndexSyntheticElementKind.loadLibrary;
         element = element.library;
       } else if (element is FieldElement) {
         FieldElement field = element;
@@ skipping 18 matching lines @@
         }
       } else if (element is TopLevelVariableElement) {
         TopLevelVariableElement property = element;
         kind = IndexSyntheticElementKind.topLevelVariable;
         element = property.getter;
         element ??= property.setter;
       } else {
         throw new ArgumentError(
             'Unsupported synthetic element ${element.runtimeType}');
       }
-    }
-    int offset = element.nameOffset;
-    if (element is LibraryElement || element is CompilationUnitElement) {
+    } else if (element is LibraryElement || element is CompilationUnitElement) {
+      kind = IndexSyntheticElementKind.unit;
       offset = 0;
     }
+    offset ??= element.nameOffset;
     return new ElementInfo(unitId, offset, kind);
   }
 }
 
 /**
  * Information about a single defined name.  Any [_DefinedNameInfo] is always
  * part of a [_UnitIndexAssembler], so [offset] should be understood within the
  * context of the compilation unit pointed to by the [_UnitIndexAssembler].
  */
 class _DefinedNameInfo {
@@ skipping 567 matching lines @@
         usedNameOffsets: nameRelations.map((r) => r.offset).toList(),
         usedNameIsQualifiedFlags:
             nameRelations.map((r) => r.isQualified).toList());
   }
 
   void defineName(String name, IndexNameKind kind, int offset) {
     _StringInfo nameInfo = pkg._getStringInfo(name);
     definedNames.add(new _DefinedNameInfo(nameInfo, kind, offset));
   }
 }