anchor.diff:      tryEval
       ;
     inherit (lib)
  +    boolToString
       filter
       getAttr
       isString
  
positive.code:       filter = path: type: filter path type && orig.filter path type;
        name = if name != null then name else orig.name;
      };
  
    # Filter sources by a list of regular expressions.
    #
  
negative.code: 
      sourceByRegex
      sourceFilesBySuffices
  
      trace
      ;
  }
  