#![feature(rustc_attrs, const_let, const_fn)] #[rustc_layout_scalar_valid_range_start(1)] #[repr(transparent)] pub(crate) struct NonZero(pub(crate) T); fn main() {} const fn foo() -> NonZero { let mut x = unsafe { NonZero(1) }; x.0 = 0; //~ ERROR statements in constant functions are unstable //~^ ERROR mutation of layout constrained field is unsafe x } const fn bar() -> NonZero { let mut x = unsafe { NonZero(1) }; unsafe { x.0 = 0 }; //~ ERROR statements in constant functions are unstable x }