[Bug c++/104255] parsing trailing return type fails with parameter pack expansion when two parameter packs at present

[nickhuang99 at hotmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104255

--- Comment #1 from qingzhe huang <nickhuang99 at hotmail dot com> ---
Just a FYI, this version is a bit simplified from this original code.
(https://www.godbolt.org/z/n7ajzr46f) because this is an actual meaningful
function to reverse a given index_sequence. You can see if trailing return type
works, it doesn't need to define the function body so that the template
function works exactly like a meta function.


template<size_t...Indexes, size_t...Numbers>
auto get_reverse_sequence_helper(index_sequence<Indexes...>indexes, 
            index_sequence<Numbers...>numbers)
// If this trailing return type is OK, we don't need actually define 
// function body.
->index_sequence< (getSeqByIndex<Indexes, Numbers...>(numbers))... >
{
    return index_sequence< (getSeqByIndex<Indexes, Numbers...>(numbers))...
>{};
}