Use implicit (not explicit) rules for promotability by default in `const fn` For crater run. See https://github.com/rust-lang/const-eval/pull/54#discussion_r469995552. cc #75586
Use implicit (not explicit) rules for promotability by default in `const fn` For crater run. See https://github.com/rust-lang/const-eval/pull/54#discussion_r469995552. cc #75586