bytemuck/tests/wrapper_forgets.rs

use bytemuck::TransparentWrapper;

#[repr(transparent)]
struct Wrap(Box<u32>);

// SAFETY: it's #[repr(transparent)]
unsafe impl TransparentWrapper<Box<u32>> for Wrap {}

fn main() {
  let value = Box::new(5);
  // This used to duplicate the wrapped value, creating a double free :(
  Wrap::wrap(value);
}