anchor.diff:  fragment
   OctalDigitOrUnderscore
       :   OctalDigit
  -    |   '_'
  +    |   Underscore
       ;
   
   fragment
  
positive.code: fragment
  BinaryDigitOrUnderscore
      :   BinaryDigit
      |   '_'
      ;
  
  // §3.10.2 Floating-Point Literals
  
negative.code: fragment
  HexDigitOrUnderscore
      :   HexDigit
      |   Underscore
      ;
  
  fragment
  