useless_vec does not consider mutability

[horacimacias]

I tried this code:

fn on_mut_slice(_: &mut [u8]) {}
fn main() { 
    on_mut_slice(&mut vec![]);
}

I expected to see this happen:
clippy to suggest I could use a mutable reference to a slice.
e.g:

help: you can use a slice directly: `&mut []`

Instead, this happened:
clippy suggested I could use a slice, not mutable, so applying the suggestion results in code not compiling.
suggestion

help: you can use a slice directly: `&[]`

compiler error:

   |     on_mut_slice(&[]);
   |                  ^^^ types differ in mutability

Meta

• cargo clippy -V: clippy 0.1.51 (2fd73fab 2021-03-23)
• rustc -Vv:

  rustc 1.51.0 (2fd73fabe 2021-03-23)
  

binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-apple-darwin
release: 1.51.0
LLVM version: 11.0.1