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
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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
Don't lint `suspicious_else_formatting` inside proc-macros
fixes: #7650
I'll add a test for this one soon.
changelog: Don't lint `suspicious_else_formatting` inside proc-macros
Expand box_vec lint to box_collection
fixed#7451
changelog: Expand `box_vec` into [`box_collection`], and have it error on all sorts of boxed collections
Change `while_let_on_iterator` suggestion to use `by_ref()`
It came up in the discussion #7659 that suggesting `iter.by_ref()` is a clearer suggestion than `&mut iter`. I personally think they're equivalent, but if `by_ref()` is clearer to people then that should be the suggestion.
changelog: Change `while_let_on_iterator` suggestion when using `&mut` to use `by_ref()`
