#[repr(C)] union Bar { a: &'static u8, b: usize, } const fn bar() -> u8 { unsafe { // this will error as long as this test // is run on a system whose pointers need more // than 8 bits Bar { a: &42 }.b as u8 } } fn main() { let x: &'static u8 = &(bar() + 1); //~ ERROR temporary value dropped while borrowed let y = *x; unreachable!(); }