cannot parse if let

[bblum]

#[mutate]
pub fn if_let() -> bool {
    let x = Some(true);
    if let Some(b) = x {
        b
    } else {
        false
    }
}

error: expected expression, found statement (`let`)
   --> src/test.rs:10:8
    |
167 |     if let Some(b) = x {
    |        ^^^ expected expression
    |
    = note: variable declaration using `let` is a statement