Fix ICE when `start` lang item has wrong generics
In my previous pr #87875 I missed the requirements on the `start` lang item due to its relative difficulty to test and opting for more conservative estimates. This fixes that by updating the requirement to be exactly one generic type.
The `start` lang item should have exactly one generic type for the return type of the `main` fn ptr passed to it. I believe having zero would previously *sometimes* compile (often with the use of `fn() -> ()` as the fn ptr but it was likely UB to call if the return type of `main` was not `()` as far as I know) however it also sometimes would not for various errors including ICEs and LLVM errors depending on exact situations. Having more than 1 generic has always failed with an ICE because only the one generic type is expected and provided.
Fixes#79559, fixes#73584, fixes#83117 (all duplicates)
Relevant to #9307
r? ````@cjgillot````
Re-write shadow lints
changelog: Move shadow_unrelated to restriction
changelog: The shadow lints find a lot more shadows and are not limited to certain patterns
Drastically simplifies the implementation. Catches a lot more cases.
I removed the "initialization happens here" note. It is not helpful IMO.
Closes#318Fixes#2890Fixes#6563Fixes#7588Fixes#7620
fix bug for large_enum_variants
Fix the discussion problem in the issue of https://github.com/rust-lang/rust-clippy/issues/7666#issuecomment-919654291
About the false positive problem of case:
```rust
enum LargeEnum6 {
A,
B([u8;255]),
C([u8;200]),
}
```
changelog: Fix largest_enum_variant wrongly identifying the second largest variant.
Rustup
This needs a review this time. Especially 521bf8f0fa cc `@camsteffen` I think this is necessary now, because `itertools` is no longer a dependency of `clippy_utils` and therefore this path can't be found 🤔
( I forgot about the sync last week. I should get to document this process better, so other people can do it when I'm not around )
changelog: none
#7594: Adding new 'while_let_some_result' linting
Excited for the opportunity to contribute to Clippy! Since the latest Bay Area Rust Meetup, I've been looking for an opportunity and found it 😄
Please let me know how I can improve this PR! Much of it is similar to ``[`if_let_some_result`]``, but I followed the description in the issue to create its own linting rules. Looking forward to feedback, and continuing to work on Clippy in the future!
changelog: Renamed Lint: `if_let_some_result` is now called [`match_result_ok`]. Now also handles `while let` case.
