Use the explicit string 'void' to refer to void in summaries.

pkg/analyzer/lib/src/summary/prelink.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/src/summary/format.dart';
 import 'package:analyzer/src/summary/name_filter.dart';
 
 /**
  * Create a [LinkedLibraryBuilder] corresponding to the given
  * [definingUnit], which should be the defining compilation unit for a library.
@@ skipping 107 matching lines @@
 
   /**
    * Cache of values returned by [getPart].
    */
   final Map<String, UnlinkedUnit> partCache = <String, UnlinkedUnit>{};
 
   /**
    * Names defined inside the library being prelinked.
    */
   final Map<String, _Meaning> privateNamespace = <String, _Meaning>{
-    'dynamic': new _Meaning(0, ReferenceKind.classOrEnum, 0, 0)
+    'dynamic': new _Meaning(0, ReferenceKind.classOrEnum, 0, 0),
+    'void': new _Meaning(0, ReferenceKind.classOrEnum, 0, 0)
   };
 
   /**
    * List of dependencies of the library being prelinked.  This will be output
    * to [LinkedLibrary.dependencies].
    */
   final List<LinkedDependencyBuilder> dependencies = <LinkedDependencyBuilder>[
     new LinkedDependencyBuilder()
   ];
 
@@ skipping 305 matching lines @@
    * [sourceUri] is also relative.
    */
   String resolveUri(String sourceUri, String relativeUri) {
     if (sourceUri == null) {
       return relativeUri;
     } else {
       return Uri.parse(sourceUri).resolve(relativeUri).toString();
     }
   }
 }