error: Undefined Behavior: deallocating while item is protected: [SharedReadWrite for <TAG> (call ID)]
  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
   |
LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocating while item is protected: [SharedReadWrite for <TAG> (call ID)]
   |
   = help: this indicates a potential bug in the program: it performed an invalid operation, but the rules it violated are still experimental
   = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
           
   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
   = note: inside `<std::alloc::Global as std::alloc::Allocator>::deallocate` at RUSTLIB/alloc/src/alloc.rs:LL:CC
   = note: inside `alloc::alloc::box_free::<std::cell::Cell<i32>, std::alloc::Global>` at RUSTLIB/alloc/src/alloc.rs:LL:CC
   = note: inside `std::ptr::drop_in_place::<std::boxed::Box<std::cell::Cell<i32>>> - shim(Some(std::boxed::Box<std::cell::Cell<i32>>))` at RUSTLIB/core/src/ptr/mod.rs:LL:CC
   = note: inside `std::mem::drop::<std::boxed::Box<std::cell::Cell<i32>>>` at RUSTLIB/core/src/mem/mod.rs:LL:CC
note: inside closure at $DIR/deallocate_against_barrier2.rs:LL:CC
  --> $DIR/deallocate_against_barrier2.rs:LL:CC
   |
LL |         drop(unsafe { Box::from_raw(raw) });
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: inside `<[closure@$DIR/deallocate_against_barrier2.rs:LL:CC] as std::ops::FnOnce<(&std::cell::Cell<i32>,)>>::call_once - shim` at RUSTLIB/core/src/ops/function.rs:LL:CC
note: inside `inner` at $DIR/deallocate_against_barrier2.rs:LL:CC
  --> $DIR/deallocate_against_barrier2.rs:LL:CC
   |
LL |     f(x)
   |     ^^^^
note: inside `main` at $DIR/deallocate_against_barrier2.rs:LL:CC
  --> $DIR/deallocate_against_barrier2.rs:LL:CC
   |
LL | /     inner(Box::leak(Box::new(Cell::new(0))), |x| {
LL | |         let raw = x as *const _ as *mut Cell<i32>;
LL | |         drop(unsafe { Box::from_raw(raw) });
LL | |     });
   | |______^

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to previous error