NoMatchingPatternKeyError#matchee

static VALUE
no_matching_pattern_key_err_matchee(VALUE self)
{
    VALUE matchee;

    matchee = rb_ivar_lookup(self, id_matchee, Qundef);
    if (!UNDEF_P(matchee)) return matchee;
    rb_raise(rb_eArgError, "no matchee is available");
}