'enumerator  : ID
| ID EQUALS constant_expression'

def p_enumerator(self, p):

    if (len(p) == 2):
        enumerator = c_ast.Enumerator(p[1], None, self._coord(p.lineno(1)))
    else:
        enumerator = c_ast.Enumerator(p[1], p[3], self._coord(p.lineno(1)))
    self._add_identifier(enumerator.name, enumerator.coord)
    p[0] = enumerator
