Use NonNull pointer in the place of references in AtomicRef and AtomicRefMut to avoid noalias related soundness bug.

[Imberflur]

With this test added:

#[test]fndrop_and_borrow_in_fn_call(){fndrop_and_borrow(cell:&AtomicRefCell<Bar>,borrow:AtomicRef<'_,Bar>){drop(borrow);*cell.borrow_mut() = Bar::default();}let a = AtomicRefCell::new(Bar::default());let borrow = a.borrow();drop_and_borrow(&a, borrow);}

Running cargo +nightly miri test produces:

test drop_and_borrow_in_fn_call ... error:UndefinedBehavior: not granting access to tag <236157> because that would remove [SharedReadOnlyfor <236092>] which is strongly protected because it is an argument of call 64948
--> /home/imbris/projects/atomic_refcell/src/lib.rs:144:33
|
144 | value:unsafe{&mut*self.value.get()},
| ^^^^^^^^^^^^^^^^^^^^^^ not granting access to tag <236157> because that would remove [SharedReadOnlyfor <236092>] which is strongly protected because it is an argument of call 64948
|
= help: this indicates a potential bug in the program: it performed an invalid operation, but the StackedBorrows 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
help: <236157> was created by a SharedReadWrite retag at offsets [0x8..0xc]
--> /home/imbris/projects/atomic_refcell/src/lib.rs:144:39
|
144 | value:unsafe{&mut*self.value.get()},
| ^^^^^^^^^^^^^^^^
help: <236092> is this argument
--> tests/basic.rs:96:51
|
96 | fn drop_and_borrow(cell:&AtomicRefCell<Bar>, borrow:AtomicRef<'_,Bar>){
| ^^^^^^
= note:BACKTRACE(of the first span):
= note: inside `atomic_refcell::AtomicRefCell::<Bar>::borrow_mut` at /home/imbris/projects/atomic_refcell/src/lib.rs:144:33:144:55note: inside `drop_and_borrow_in_fn_call::drop_and_borrow`
--> tests/basic.rs:98:10
|
98 | *cell.borrow_mut() = Bar::default();
| ^^^^^^^^^^^^^^^^^
note: inside `drop_and_borrow_in_fn_call`
--> tests/basic.rs:103:5
|
103 | drop_and_borrow(&a, borrow);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
note:inside closure
--> tests/basic.rs:95:33
|
94 | #[test]
| ------- in this procedural macro expansion
95 | fn drop_and_borrow_in_fn_call(){
| ^
= note: this error originates in the attribute macro `test` (in Nightlybuilds, run with -Z macro-backtrace for more info)

This PR replaces the reference with NonNull<T> which is the same fix applied for std::cell::RefCell.

[Imberflur]

Forgot Send/Sync impls! They are added now.

[cuviper]

I think you'll want to update Debug too, like I had to fix in rust-lang/rust#97225.

[Imberflur]

I updated Debug, thanks for the note!

[bholley]

Thanks. Sorry for the long-delay reviewing this, I had to page a bunch of stuff back in. I've released this as 0.1.10.