--- /dev/null
+// Creating a shared reference does not leak the data to raw pointers,
+// not even when interior mutability is involved.
+
+use std::cell::Cell;
+use std::ptr;
+
+fn main() { unsafe {
+ let x = &mut Cell::new(0);
+ let raw = x as *mut Cell<i32>;
+ let x = &mut *raw;
+ let _shr = &*x;
+ // The state here is interesting because the top of the stack is [Unique, SharedReadWrite],
+ // just like if we had done `x as *mut _`.
+ // If we said that reading from a lower item is fine if the top item is `SharedReadWrite`
+ // (one way to maybe preserve a stack discipline), then we could now read from `raw`
+ // without invalidating `x`. That would be bad! It would mean that creating `shr`
+ // leaked `x` to `raw`.
+ let _val = ptr::read(raw);
+ let _val = *x.get_mut(); //~ ERROR borrow stack
+} }