OptionParser::List#accept

# File tmp/rubies/ruby-3.1.3/lib/optparse.rb, line 787
def accept(t, pat = /.*/m, &block)
  if pat
    pat.respond_to?(:match) or
      raise TypeError, "has no `match'", ParseError.filter_backtrace(caller(2))
  else
    pat = t if t.respond_to?(:match)
  end
  unless block
    block = pat.method(:convert).to_proc if pat.respond_to?(:convert)
  end
  @atype[t] = [pat, block]
end