| // Demonstrate that "rogue" `DerefMut` impls for `&T` are not allowed. |
| // |
| // https://github.com/rust-lang/rust/issues/66544 |
| |
| use std::cell::Cell; |
| use std::marker::PhantomPinned; |
| use std::ops::DerefMut; |
| use std::pin::Pin; |
| |
| struct MyType<'a>(Cell<Option<&'a mut MyType<'a>>>, PhantomPinned); |
| |
| impl<'a> DerefMut for &'a MyType<'a> { |
| //~^ ERROR E0751 |
| fn deref_mut(&mut self) -> &mut MyType<'a> { |
| self.0.take().unwrap() |
| } |
| } |
| |
| fn main() { |
| let mut unpinned = MyType(Cell::new(None), PhantomPinned); |
| let bad_addr = &unpinned as *const MyType<'_> as usize; |
| let p = Box::pin(MyType(Cell::new(Some(&mut unpinned)), PhantomPinned)); |
| |
| // p_ref is okay: it does not point to the bad_addr |
| let mut p_ref: Pin<&MyType<'_>> = p.as_ref(); |
| assert_ne!(bad_addr, &*p_ref as *const _ as usize); |
| |
| // but p_mut does point to bad_addr! this is unsound |
| let p_mut: Pin<&mut MyType<'_>> = p_ref.as_mut(); |
| assert_eq!(bad_addr, &*p_mut as *const _ as usize); |
| |
| println!("oh no!"); |
| } |
