anchor.diff:     * bundle. The bundle is then put into the [_byteStore] and returned.
      */
     PackageBundle _getUnlinked(_File file) {
  +    // By accessing 'contentHash' we ensure that the current file state
  +    // has some version of the file content hash, so we will be able to
  +    // use it to attempt to get the current unlinked bundle.
  +    String key = '${file.contentHash}.unlinked';
       return _getCurrentUnlinked(file) ??
           _logger.run('Create unlinked for $file', () {
  -          String key = '${file.contentHash}.unlinked';
             UnlinkedUnitBuilder unlinkedUnit = serializeAstUnlinked(file.unit);
             PackageBundleAssembler assembler = new PackageBundleAssembler();
             assembler.addUnlinkedUnitWithHash(
  
positive.code:   final List<String> imported = <String>[];
    final List<String> exported = <String>[];
    final List<String> parted = <String>[];
  }
  
negative.code:   /**
     * Verify the API signatures for the changed files, and decide which linked
     * libraries should be invalidated, and files reanalyzed.
     *
     * TODO(scheglov) I see that adding a local var changes (full) API signature.
     */
    void _verifyUnlinkedSignatureOfChangedFiles() {
      if (_filesToVerifyUnlinkedSignature.isEmpty) {
  