one type is more general than the other: note: expected reference `&_` found reference `&_` (note: the lifetime requirement is introduced here: [arrow points at nothing])

Code

fn main() {
    let outputs_rgb: &mut [[u8; 12]] = &mut [];
    fn gaming(_: &[u8; 12]) -> &[u8] {
        unimplemented!()
    }
    outputs_rgb.sort_unstable_by_key(gaming);
}

Current output

error[E0308]: mismatched types
    --> test.rs:6:5
     |
6    |     outputs_rgb.sort_unstable_by_key(gaming);
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ one type is more general than the other
     |
     = note: expected reference `&_`
                found reference `&_`
note: the lifetime requirement is introduced here
    --> D:\Users\nabijaczleweli\.rustup\toolchains\stable-x86_64-pc-windows-gnu\lib/rustlib/src/rust\library\core\src\slice\mod.rs:3029:25
     |
3029 |         F: FnMut(&T) -> K,
     |                         ^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.

Desired output

idk. literally anything else i think lol

Rust Version

rustc 1.84.1 (e71f9a9a9 2025-01-27)
binary: rustc
commit-hash: e71f9a9a98b0faf423844bf0ba7438f29dc27d58
commit-date: 2025-01-27
host: x86_64-pc-windows-gnu
release: 1.84.1
LLVM version: 19.1.5

Reproduce the example with rustc 1.84.1 and inspect the lifetime requirement reported at rustlib/src/rust/library/core/src/slice/mod.rs:3029. Trace how this requirement reaches the E0308 diagnostic and determine what clearer explanation can be produced. Done means the same code reports an understandable diagnostic, covered by an appropriate compiler diagnostic test.