FP expected !, found () `if (() = return) {}`

[matthiaskrgr]

fn main() {
    if (() = return) {}
}

this compiles with rustc but ra diag shows

at crate ra, file /tmp/ra/src/main.rs: Error RustcHardError("E0308") from LineCol { line: 1, col: 8 } to LineCol { line: 1, col: 10 }: expected !, found ()

[matthiaskrgr]

probably similar:

fn main() {
    () = panic!();
}