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