https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105644
--- Comment #2 from Namniav <namniav at gmail dot com> --- Now Clang also crashes on the original example(https://github.com/llvm/llvm-project/issues/64607), although its cause may be different to GCC's. I can't remember why I used `get` instead of `std::get` in original code because I didn't really know how ADL finds function templates. The issue still exists with `std::get`. Here is a modified and GCC-only reduced version: https://godbolt.org/z/MMYMrGE3z ```c++ template<typename T, int I> concept C = (sizeof(I) + sizeof(T) > 0); template<typename T, int...I> constexpr bool check() { return ((requires(T t) { { (I, t) } -> C<I>; }) && ...); } template<class T> concept tuple_like = check<T, 0>(); static_assert(tuple_like<int>); ``` Noted that GCC doesn't consider using `I` in `-> C<I>` as using a parameter pack, I have to use it in comma expression `(I, t)` to get a fold expression, otherwise GCC complains "operand of fold expression has no unexpanded parameter packs". I suspect that GCC has problem with such case. It some how explains, for GCC only, why replacing `std::tuple_element_t<I, T>&` with `int&` "fixes" the issue.
