Add several run rustfix annotations
Adds `run-rustfix` to 18 of the tests from the tracking issue #3630.
Each test has its own commit, to make reviewing easier (hopefully this is easier to review than 18 separate PRs).
## Changes
- `cfg_attr_rustfmt`: Custom inner attributes are unstable. Let's disable the lint for inner attributes until [#54726](https://github.com/rust-lang/rust/issues/54726) stabilizes
- `collapsible_if`: unrelated cyclomatic_complexity warning that can be ignored
- `duration_subsec`: Simply needed `#![allow(dead_code)]`
- `excessive_precision`: Fixed by `#!allow(dead_code,unused_variables)`
- `explicit_write`: Fixed by `#![allow(unused_imports)]`
- `inconsistent_digit_grouping`: Avoid triggering `clippy::excessive_precision` lint
- `infallible_destructuring_match`: Fixed by `#![allow(dead_code, unreachable_code, unused_variables)]`
- `into_iter_on_ref`: Triggered unrelated `clippy::useless_vec` lint
- `large_digit_groups`: Avoid triggering `clippy::excessive_precision` lint
- `map_clone`: Fixed by `#![allow(clippy::iter_cloned_collect)]`
- `mem_replace`: Suggestion causes import to be unused, fixed by `#![allow(unused_imports)]`
- `precedence`: Allow some unrelated lints, and change out-of-range `0b1111_1111i8` literal
- `redundant_field_names`: Allow dead code, and remove stabilized feature toggles
- `replace_consts`: Fixed by `#![allow(unused_variables)]`
- `starts_ends_with`: Fixed by `#![allow(unused_must_use)]`
- `types`: Fixed by `#![allow(dead_code, unused_variables)]`
- `unit_arg`: Fixed by `#[allow(unused_must_use)]`
- `unnecessary_fold`: Fixed by adding type annotations and adding `#![allow(dead_code)]`
Update Readme for (arguably) better readability
Move final instruction to run clippy into a third step in the Readme so it's easier to spot at a quick glance.
Restrict `use_self` on nested items
Fixes#3637Fixes#3463
These changes make it so that nested items aren't visited any more by the `use_self` lint.
I think visiting nested items should be possible (so that it uses a different `item_path` for the nested item), but I'm not sure whether it's viable and what the best approach would be.
- Can `item_path` be changed to a new `Self` path before visiting the item, and then changing it back afterwards?
- Alternatively, could a new visitor be created, re-using `check_trait_method_impl_decl`?
cast_ref_to_mut lint
I see this pattern way too often, and it's completely wrong. In fact, due to how common this incorrect pattern is, [the Rustonomicon specifically points this out](https://doc.rust-lang.org/nomicon/transmutes.html).
> - Transmuting an & to &mut is UB
> - Transmuting an & to &mut is always UB
> - No you can't do it
> - No you're not special
This is my first lint.
