https://gcc.gnu.org/g:5924c7d584640665db174c7545ae6c2b784af27c commit r13-2826-g5924c7d584640665db174c7545ae6c2b784af27c Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Sep 23 22:04:24 2022 +0100 libstdc++: Add test for type traits not having friend access This ensures that the std::is_assignable and std::is_assignable_v traits are evaluated "in a context unrelated" to the argument types. libstdc++-v3/ChangeLog: * testsuite/20_util/is_assignable/requirements/access.cc: New test. Diff: --- .../20_util/is_assignable/requirements/access.cc | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/libstdc++-v3/testsuite/20_util/is_assignable/requirements/access.cc b/libstdc++-v3/testsuite/20_util/is_assignable/requirements/access.cc new file mode 100644 index 00000000000..a96fba654cd --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/is_assignable/requirements/access.cc @@ -0,0 +1,22 @@ +// { dg-do compile { target c++11 } } + +#include <type_traits> + +class S { + operator int(); + friend void g(); // #1 +}; + +void +g() +{ + int i = 0; + S s; + i = s; // this works, because we're inside a friend. + + // But the traits are evaluated in "a context unrelated to either type". + static_assert( ! std::is_assignable<int&, S>::value, "unfriendly"); +#if __cplusplus >= 201703L + static_assert( ! std::is_assignable_v<int&, S>, "unfriendly"); +#endif +}