Restriction lint for function pointer casts
The existing lints for function pointer casts cover the cases where a cast is non-portable or would result in truncation, however there's currently no way to forbid numeric function pointer casts entirely.
I've added a new lint `fn_to_numeric_cast_any`, which allows one to ban _all_ numeric function pointer casts, including to `usize`. This is useful if you're writing high-level Rust and want to opt-out of potentially surprising behaviour, avoiding silent bugs from forgotten parentheses, e.g.
```rust
fn foo() -> u32 {
10
}
fn main() {
let _ = foo as usize; // oops, forgot to call foo and got a random address instead!
}
```
~~I'm open to suggestions for the naming of the lint, because `fn_to_numeric_cast_any` is a bit clunky. Ideally I'd call this lint `fn_to_numeric_cast`, but that name is already taken for the more specific lint~~. We've stuck with `fn_to_numeric_cast_any` to avoid renaming the existing lint, or choosing a different name that's too generic (like `fn_cast`).
I'm also open to changing the suggestion behaviour, as adding parentheses is only one of many possible ways to fix the lint.
changelog: add ``[`fn_to_numeric_cast_any`]`` restriction lint
Make `shadow_reuse` suggestion less verbose
Closes#7764
Make `shadow_reuse` suggestion less verbose.
changelog: [`shadow_reuse`] does not warn shadowing statement
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
