[Bug c++/87441] [concepts] Found compiler internal error: in tsubst at cp/pt.c:13657

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87441

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
This is enough:

template<typename X, typename Y = X>
concept bool HasBinaryAdd = requires(X x, Y y)
{
  {x + y} -> decltype(x + y);
};

void proc(HasBinaryAdd x, HasBinaryAdd y);