anchor.diff:  build_dot(Dot, {dot, _, _} = Left, Right) ->
     {dot, token_meta(Dot), {dot_fullname(Left), token_symbol(Right)}}.
   
  +build_bitstring_element(Token) ->
  +  Symbol = token_symbol(Token),
  +  E = case is_integer(Symbol) of
  +        true -> Symbol;
  +        false -> throw_invalid_bitstring_element(Token)
  +      end,
  +  {list, token_meta(Token), [E]}.
  +
   build_bitstring(Marker, Args) ->
     {bitstring, token_meta(Marker), Args}.
   
  
positive.code: 
  %% Bitstring
  
  bitstring_arg_list  -> bitstring_arg_list list_container : ['$2' | '$1'].
  
  bitstring_args      -> bitstring_arg_list : lists:reverse('$1').
  bitstring_args      -> values : '$1'.
  
  bitstring_container -> '<<' '>>' : build_bitstring('$1', []).
  bitstring_container -> '<<' bitstring_args '>>' : build_bitstring('$1', '$2').
  
negative.code:     grammar
      expression expression_list expressions
      number signed_number atom_expr
      bitstring_arg commas_bitstring_arg bitstring_arg_list bitstring_args bitstring_container
      quote_expr backquote_expr unquote_expr unquote_splicing_expr
      value comma_value value_list values
      open_paren close_paren open_bracket close_bracket list_container cons_list
  