Rollup of 14 pull requests
Successful merges:
- #75180 (Implement Error for &(impl Error))
- #78578 (Permit mutable references in all const contexts)
- #79174 (Make std::future a re-export of core::future)
- #79884 (Replace magic numbers with existing constants)
- #80855 (Expand assert!(expr, args..) to include $crate for hygiene on 2021.)
- #80933 (Fix sysroot option not being honored across rustc)
- #81259 (Replace version_check dependency with own version parsing code)
- #81264 (Add unstable option to control doctest run directory)
- #81279 (Small refactor in typeck)
- #81297 (Don't provide backend_optimization_level query for extern crates)
- #81302 (Fix rendering of stabilization version for trait implementors)
- #81310 (Do not mark unit variants as used when in path pattern)
- #81320 (Make bad shlex parsing a pretty error)
- #81338 (Clean up `dominators_given_rpo`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
d3163e9655