New Lint: inspect_then_for_each
**Work In Progress**
This PR addresses [Issue 5209](https://github.com/rust-lang/rust-clippy/issues/5209) and adds a new lint called `inspect_then_for_each`.
Current seek some guidance.
If you added a new lint, here's a checklist for things that will be
checked during review or continuous integration.
- \[x] Followed [lint naming conventions][lint_naming]
- \[x] Added passing UI tests (including committed `.stderr` file)
- \[x] `cargo test` passes locally
- \[x] Executed `cargo dev update_lints`
- \[x] Added lint documentation
- \[x] Run `cargo dev fmt`
[lint_naming]: https://rust-lang.github.io/rfcs/0344-conventions-galore.html#lints
---
changelog: Add [`inspect_for_each`] lint for the use of `inspect().for_each()` on `Iterators`.
Add a note to `as_conversions`
I have seen a couple of examples where there are some misunderstandings of `as_conversions` ([1](https://github.com/rust-lang/rust-clippy/issues/5890#issuecomment-671852546), [2](https://github.com/rust-lang/rust-clippy/issues/6116#issuecomment-704251710) and [3](https://github.com/rust-lang/rust-clippy/issues/6428)). This PR adds the note that explains its purpose and relationship with other `as` related casts. Open question: should I list every related lints for discoverbility, or just suggest how to find these? I chose the former because there's no way to list only and all `as` related lints (e.g. on All the Clippt Lints, 'cast' includes some noises, but `cast_` excludes some) even though I cannot guarantee the list will be updated to include future changes.
---
changelog: Add a note to the document of `as_conversions`
- Don't add backticks for the reason a lint was removed. This is almost
never a code block, and when it is the backticks should be in the reason
itself.
- Don't assume clippy is the only tool that needs to be checked for
backwards compatibility
New lint: redundant_slicing
changelog: Added lint: `redundant_slicing`
fixes#6519
This will trigger on any type which implements `Index<RangeFull>` that returns the input type. This would be a false positive if the implementation does something other than return itself, but I'm not sure why you would ever want to do that.
Fix the ICE 6539
Fixes#6539
It happened because `zero_sized_map_values` used `layout_of` with types from type aliases, which is essentially the same as the ICE 4968.
---
changelog: Fix an ICE in `zero_sized_map_values`
Fix FP with empty return for `needless_return` lint
This fixes a false positive in `needless_return` lint, when triggered in a closure using `return` statement without value.
Fixes: #6501
changelog: none
Case sensitive file extensions
Closes#6425
Looks for ends_with methods calls with case sensitive extension comparisons.
changelog: Add new lint that warns about case-sensitive file extension comparisons.
