Incorrect message in shadow_unrelated

[Riateche]

cargo clippy -V
clippy 0.0.212 (2e26fdc 2018-11-22)

Code:

#![deny(clippy::shadow_unrelated)]

enum A {
    B { cast: i32, },
    C
}

fn fun(cast: u32) {
    let a = A::C;
    if let A::B { cast } = a {
        println!("{}", cast);
    }
}

fn main() {
    println!("Hello, world!");
}

Error message:

error: `cast` is shadowed by `a`

It's unclear how cast can be shadowed by a, given that they have different names. Something like "cast shadowed by cast" or "cast variable shadowed by an if let binding" might be more understandable.