rustc/tests/ui/lint/force-warn/allowed-deny-by-default-lint.rs

// --force-warn $LINT causes $LINT (which is deny-by-default) to warn
// despite $LINT being allowed in module
// compile-flags: --force-warn mutable_transmutes
// check-pass

#![allow(mutable_transmutes)]
fn main() {
    unsafe {
        let y = std::mem::transmute::<&i32, &mut i32>(&5); //~WARN: undefined behavior
    }
}