Auto merge of #51448 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 13 pull requests

Successful merges:

 - #50143 (Add deprecation lint for duplicated `macro_export`s)
 - #51099 (Fix Issue 38777)
 - #51276 (Dedup auto traits in trait objects.)
 - #51298 (Stabilize unit tests with non-`()` return type)
 - #51360 (Suggest parentheses when a struct literal needs them)
 - #51391 (Use spans pointing at the inside of a rustdoc attribute)
 - #51394 (Use scope tree depths to speed up `nearest_common_ancestor`.)
 - #51396 (Make the size of Option<NonZero*> a documented guarantee.)
 - #51401 (Warn on `repr` without hints)
 - #51412 (Avoid useless Vec clones in pending_obligations().)
 - #51427 (compiletest: autoremove duplicate .nll.* files (#51204))
 - #51436 (Do not require stage 2 compiler for rustdoc)
 - #51437 (rustbuild: generate full list of dependencies for metadata)

Failed merges: