`BorrowingIteratorProtocol` false positive?

I am hitting a compilation error, which I think is a false positive, attempting to upgrade some code to use BorrowingIteratorProtocol since it compiles fine if I remove the first condition from the if statement (tested with the 6.4.x-snapshot-2026-08-14, nightly, and devsnapshot toolchains on Arch Linux). Is it actually a false positive, if so I'll open an issue on github, or am I holding it wrong? Godbolt for small reproducer. ▶ small reproducer ▶ compilation error