[Bug c++/83542] template deduction failure when using pack in both deduced and non-deduced contexts

[barry.revzin at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83542

--- Comment #1 from Barry Revzin <barry.revzin at gmail dot com> ---
This slightly different example:

template <typename... T>
struct list { };

template <typename... T, typename U>
void foo(list<T...>, list<U>, void(*)(T..., U)) 
{ }


void f(int, int) { } 

int main()
{
    foo(list<int>{}, list<int>{}, &f);
}


fails with a different error:

foo.cxx: In function ‘int main()’:
foo.cxx:13:37: error: no matching function for call to ‘foo(list<int>,
list<int>, void (*)(int, int))’
     foo(list<int>{}, list<int>{}, &f);
                                     ^
foo.cxx:5:6: note: candidate: template<class ... T, class U> void foo(list<T
...>, list<U>, void (*)(T ..., U))
 void foo(list<T...>, list<U>, void(*)(T..., U))
      ^~~
foo.cxx:5:6: note:   template argument deduction/substitution failed:
foo.cxx:13:37: note:   candidate expects 1 argument, 2 provided
     foo(list<int>{}, list<int>{}, &f);
                                     ^