[Bug c++/67225] [concepts] Expression constraint with a constrained result turns off access checking

[andrew.n.sutton at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67225

--- Comment #7 from Andrew Sutton <andrew.n.sutton at gmail dot com> ---
It looks like there was an earlier state where access was being turned
off by one construct or another. All of the examples here fail as they're
supposed to. Added tests to concepts-cxx2a.