anchor.diff:          |   'n' 
           |   'f' 
           |   'r'
  -        |   's' 
  +        //|   's' 
           |   '\"' 
           |   '\''
           )          
  
positive.code:     -> ^(FLOAT_CST FLOATLITERAL)
      | QUOTEDLITERAL
      -> ^(QUOTE_CST QUOTEDLITERAL)
      | CHARLITERAL
      -> ^(CHAR_CST CHARLITERAL)
      ;
  
  stringExpression
  
negative.code:     | 'override'
      | 'optional'
      | 'mutable'
      | 'extension'
      | 'volatile'
      ;
  