anchor.diff:          constant
           integer
           string_expr
  +        fidentifier
           .
   
   Terminals
  
positive.code: msg_elem -> message_def:                '$1'.
  msg_elem -> enum_def:                   '$1'.
  msg_elem -> extensions_def:             {extensions,lists:sort('$1')}.
  
  opt_field_opts -> field_opts:           '$1'.
  opt_field_opts -> '$empty':             [].
  
negative.code: -export([fetch_imports/1]).
  
  identifier_name({identifier, _Line, Name}) -> list_to_atom(Name).
  
  kw_to_identifier({Kw, Line}) ->
      {identifier, Line, atom_to_list(Kw)}.
  
  literal_value({_TokenType, _Line, Value}) -> Value.
  
  