[Bug c++/94644] New: Wrong is_nothrow_move_constructible result if used in a template first

[rafael at espindo dot la]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94644

            Bug ID: 94644
           Summary: Wrong is_nothrow_move_constructible result if used in
                    a template first
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rafael at espindo dot la
  Target Milestone: ---

Tested with c5bac7d127f288fd2f8a1f15c3f30da5903141c6.

Given

-----------------------------------------------
#include <type_traits>
struct future_state_base {
protected:
    ~future_state_base() noexcept;
};
#ifdef foo
    static_assert(std::is_nothrow_move_constructible<future_state_base>::value,
        "future_state_base's move constructor must not throw");
#endif
template <typename... T>
struct future_state : public future_state_base {
    static_assert(std::is_nothrow_move_constructible<future_state_base>::value,
        "future_state_base's move constructor must not throw");
};
void f(future_state<int> x) {
}
-----------------------------------------------

g++ produces no error with just -c, but if I add -Dfoo both static asserts
fails. With clang, and libstdc++, I get one or two errors depending on whether
-Dfoo is used.