docs: def p_elseif_list(p):
      '''elseif_list : empty
                     | elseif_list ELSEIF LPAREN expr RPAREN statement'''
      if len(p) == 2:
          p[0] = []
      else:
          p[0] = p[1] + [ast.ElseIf(p[4], p[6], lineno=p.lineno(2))]