Post #2313508

@yosh@toot.yosh.is @chrisdenton@hachyderm.io this issue describes only the T-libs-api change, i.e. the change to Infallible, which is a library type. The PR to stabilize the never type has been nominated for T-lang: https://github.com/rust-lang/rust/pull/155499 (and is currently waiting on crater on a separate experiment / library backports)