https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69623
--- Comment #9 from jim x <xmh970252187 at gmail dot com> --- After reading [temp.deduct.call] p1 more carefully, I think you're right. Since the first function parameter pack does not participate in template argument deduction, the deduction will start to perform from the second function parameter to the last.
