$ cat a.cpp
#include <algorithm>
$ clang++ -std=c++20 a.cpp
In file included from a.cpp:1:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/algorithm:64:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ranges_algo.h:35:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ranges_algobase.h:38:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ranges:3526:19: error: missing 'typename' prior to dependent type name 'iterator_traits<iterator_t<_Base>>::iterator_category'
            using _Cat = iterator_traits<iterator_t<_Base>>::iterator_category;
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.