Fixes the following nightly clippy lints: - ~~[map_flatten](https://rust-lang.github.io/rust-clippy/master/index.html#map_flatten)~~ (Fixed on main) - ~~[needless_borrow](https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow)~~ (Fixed on main) - [return_self_not_must_use](https://rust-lang.github.io/rust-clippy/master/index.html#return_self_not_must_use) (Added in 1.59.0) - ~~[unnecessary_lazy_evaluations](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_lazy_evaluations)~~ (Fixed on main) - [extra_unused_lifetimes](https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_lifetimes) outside of macros - [let_unit_value](https://rust-lang.github.io/rust-clippy/master/index.html#let_unit_value)
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