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

[Louis Dionne via cfe-commits]

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@@ -37,9 +37,10 @@ struct __fn {
     _LIBCPP_ASSERT_UNCATEGORIZED(!bool(std::invoke(__comp, std::invoke(__proj, __high), std::invoke(__proj, __low))),
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ldionne wrote:

You're right, sorry for the noise. It supports a custom comparator, not a custom projection. I read too fast.

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