Rollup merge of #70229 - matthiaskrgr:cl3ppy, r=Mark-Simulacrum

more clippy fixes

* remove unused unit values (clippy::unused_unit)
* make some let-if-bindings more idiomatic (clippy::useless_let_if_seq)
* clarify when we pass () to functions (clippy::unit_arg)
* don't redundantly repeat field names (clippy::redundant_field_names)
* remove redundant returns (clippy::needless_return)
* use let instead of match for matches with single bindings (clippy::match_single_binding)
* don't convert results to options just for matching (clippy::if_let_some_result)

diff --cc src/librustc/ty/query/plumbing.rs
Simple merge