#![feature(transmutability)] use std::mem::{Assume, BikeshedIntrinsicFrom}; #[repr(C)] struct W<'a>(&'a ()); fn test<'a>() where W<'a>: BikeshedIntrinsicFrom< (), { Assume { alignment: true, lifetimes: true, safety: true, validity: true } }, >, { } fn main() { test(); //~^ ERROR `()` cannot be safely transmuted into `W<'_>` }