Rollup of 7 pull requests
Successful merges:
- #50233 (Make `Vec::new` a `const fn`)
- #50312 (Add more links in panic docs)
- #50316 (Fix some broken links in docs.)
- #50325 (Add a few more tests for proc macro feature gating)
- #50327 (Display correct unused field suggestion for nested struct patterns)
- #50330 (check that #[used] is used only on statics)
- #50344 (Update Cargo to 2018-04-28
122fd5be5201913d42e219e132d6569493583bca)
Failed merges: