[Bug c++/67147] [concepts] ICE on checking concept with default template arguments

[andrew.n.sutton at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67147

--- Comment #6 from Andrew Sutton <andrew.n.sutton at gmail dot com> ---
There's a test for this PR in the concepts-cxx2a branch.