Work-around 'static bound requirement in io::with_bytes_reader (note: STILL UNSOUND, see #5723)
Infer default static/Owned bounds for unbounded heap fns/traits (#7264)
Change how traits fulfill builtin bounds. Still need compile compatibility fixes.
Make closure contents call out to trait_contents.
Looser restrictions on what can be captured in unbounded heap closures.
Fix pretty-printing for bounded closures. Close #7333.