[Bug c++/103186] redefinition of template symbol error with strange error diagnostic

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103186

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Reduced testcase for the first issue (note it is a different error but the
problem is the same):
using Callback = void();
template <typename ValueType>
struct GetSetHelper
{
    static void set( Callback callback_ = []() {}  ){}
};
template <typename First>
void m()
{
    GetSetHelper<First>::set();
}
template <typename... Types>
void n( )
{
    ( ( m<Types>( ) ), ... );
}
int main()
{
    GetSetHelper<signed>::set();
    n<signed, unsigned>( );
}