code: def p_ref_type(self, p):
          '''ref_type : IDENTIFIER'''
          p[0] = ast.DefinedType(p[1], lineno=p.lineno(1)f p_ref_type(self, p):
          '''ref_type : IDENTIFIER'''
          p[0] = ast.DefinedType(p[1], lineno=p.lineno(1))
docs: ref_type : IDENTIFIER