[clang-tools-extra] [libc++] Prevent calling the projection more than three times (PR #66315)

[Louis Dionne via cfe-commits]

ldionne wrote:

> Any idea why the CI is failing? It mentions line 86 not being constexpr because of assert, but it doesn't seem like I've done anything which should affect that...

I looked into it a bit and I think the CI is failing because of the `std::forward` problem. The assertion on line 86 fails because we don't respect the value category returned by the projection, which is basically that problem.

https://github.com/llvm/llvm-project/pull/66315