b759b2efad
remove `commit_unconditionally` `commit_unconditionally` is a noop unless we somehow inspect the current state of our snapshot. The only thing which does that is the leak check which was only used in one place where `commit_if_ok` is probably at least as, or even more, correct. r? rust-lang/types
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.