Unnecessary_cast wrongly triggers on primitive methods of i32

Summary

I tried to see if this bug existed on all the integer number types, and while I haven't exhaustively tested every primitive method, count_ones(), as I used in my example, is correctly handled on:

i8   , u8,
i16  , u16
 __  , u32
i64  , u64
i128 , u128

It seems to me that this only fails when i is i32

Other methods that fail with i32 are: (count_zeros(), ilog2(), trailing_ones(), trailing_zeroes()...) <- not exhaustive

Lint Name

unnecessary_cast

Reproducer

I tried this code:

fn main() {
    for i in 1..(1 << 4) {
        println!("{}", (i as i32).count_ones() << 2 );
    }
}

I saw this happen:

warning: casting to the same type is unnecessary (`i32` -> `i32`)
 --> src/main.rs:3:24
  |
3 |         println!("{}", (i as i32).count_ones() << 2 );
  |                        ^^^^^^^^^^ help: try: `i`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
  = note: `#[warn(clippy::unnecessary_cast)]` on by default

I expected to see this happen:

no warning, allowing clippy to go through with its suggestion for i32 would result in a compiler error

Version

rustc 1.71.1 (eb26296b5 2023-08-03)
binary: rustc
commit-hash: eb26296b556cef10fb713a38f3d16b9886080f26
commit-date: 2023-08-03
host: aarch64-apple-darwin
release: 1.71.1
LLVM version: 16.0.5

Additional Labels

@rustbot label +I-suggestion-causes-error

Start by reproducing the unnecessary_cast warning with the provided Rust example, then trace the lint's handling of primitive methods on i32, especially count_ones(), count_zeros(), ilog2(), and the trailing-bit methods. Done means the lint no longer suggests removing a cast when that suggestion causes a compiler error, while the reported behavior for the other integer types remains correct.