https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97942
--- Comment #1 from David Friberg <davveston at gmail dot com> ---
Somewhat related, we may note that GCC accepts-valid the following program, say
(D):
class A { class B {}; };
template<typename T, typename U> struct S {};
template<typename U> struct S<A::B, U> {};
template<typename T> struct S<T, A::B> {};
int main() {}
which is valid as per [temp.class.spec]/10
(https://timsong-cpp.github.io/cppwp/n4861/temp.class.spec#10), which covers
waiving of access checking for template arguments in the simple-template-id of
partial specializations, a paragraph that was also added as part of P0692R1.
