72568552fd
Reduce the amount of untracked state in TyCtxt -- Take 2 Main part of #85153 The offending line (https://github.com/rust-lang/rust/pull/85153#discussion_r642866298) is replaced by a FIXME until the possible bug and the perf concern are both resolved. r? `@Aaron1011`
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.