Fix stacked borrows violation with -Zmiri-tag-raw-pointers

[taiki-e]

Arc::from_raw requires raw/mut provenance: rust-lang/rust#67339

MIRIFLAGS='-Zmiri-disable-isolation -Zmiri-tag-raw-pointers' cargo miri test --test notify -- drop_non_notified

output

error: Undefined Behavior: trying to reborrow for SharedReadWrite at alloc366878, but parent tag <927530> does not have an appropriate item in the borrow stack
   --> /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ptr/non_null.rs:327:18
    |
327 |         unsafe { &*self.as_ptr() }
    |                  ^^^^^^^^^^^^^^^ trying to reborrow for SharedReadWrite at alloc366878, but parent tag <927530> does not have an appropriate item in the borrow stack
    |
    = 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::ptr::NonNull::<alloc::sync::ArcInner<event_listener::Inner>>::as_ref` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ptr/non_null.rs:327:18
    = note: inside `std::sync::Arc::<event_listener::Inner>::inner` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/sync.rs:1071:18
    = note: inside `<std::sync::Arc<event_listener::Inner> as std::clone::Clone>::clone` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/sync.rs:1329:24
    = note: inside `event_listener::Event::listen` at /Users/taiki/projects/event-listener/src/lib.rs:177:29
note: inside `drop_non_notified` at tests/notify.rs:135:18
   --> tests/notify.rs:135:18
    |
135 |     let mut l1 = event.listen();
    |                  ^^^^^^^^^^^^^^
note: inside closure at tests/notify.rs:132:1
   --> tests/notify.rs:132:1
    |
131 |   #[test]
    |   ------- in this procedural macro expansion
132 | / fn drop_non_notified() {
133 | |     let event = Event::new();
134 | |
135 | |     let mut l1 = event.listen();
...   |
142 | |     assert!(!is_notified(&mut l2));
143 | | }
    | |_^
    = note: inside `<[closure@tests/notify.rs:132:1: 143:2] as std::ops::FnOnce<()>>::call_once - shim` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
    = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
    = note: inside `test::__rust_begin_short_backtrace::<fn()>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:574:5
    = note: inside closure at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:565:30
    = note: inside `<[closure@test::run_test::{closure#1}] as std::ops::FnOnce<()>>::call_once - shim(vtable)` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
    = note: inside `<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send> as std::ops::FnOnce<()>>::call_once` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/alloc/src/boxed.rs:1854:9
    = note: inside `<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>> as std::ops::FnOnce<()>>::call_once` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:271:9
    = note: inside `std::panicking::r#try::do_call::<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>, ()>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:485:40
    = note: inside `std::panicking::r#try::<(), std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:449:19
    = note: inside `std::panic::catch_unwind::<std::panic::AssertUnwindSafe<std::boxed::Box<dyn std::ops::FnOnce() + std::marker::Send>>, ()>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panic.rs:136:14
    = note: inside `test::run_test_in_process` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:597:18
    = note: inside closure at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:491:39
    = note: inside `test::run_test::run_test_inner` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:529:13
    = note: inside `test::run_test` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:561:28
    = note: inside `test::run_tests::<[closure@test::run_tests_console::{closure#2}]>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:304:17
    = note: inside `test::run_tests_console` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/console.rs:290:5
    = note: inside `test::test_main` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:115:15
    = note: inside `test::test_main_static` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/test/src/lib.rs:134:5
    = note: inside `main`
    = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:227:5
    = note: inside `std::sys_common::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/sys_common/backtrace.rs:123:18
    = note: inside closure at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/rt.rs:145:18
    = note: inside `std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:259:13
    = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:485:40
    = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:449:19
    = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panic.rs:136:14
    = note: inside closure at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/rt.rs:128:48
    = note: inside `std::panicking::r#try::do_call::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:485:40
    = note: inside `std::panicking::r#try::<isize, [closure@std::rt::lang_start_internal::{closure#2}]>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panicking.rs:449:19
    = note: inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#2}], isize>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/panic.rs:136:14
    = note: inside `std::rt::lang_start_internal` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/rt.rs:128:20
    = note: inside `std::rt::lang_start::<()>` at /Users/taiki/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/std/src/rt.rs:144:17
    = note: this error originates in the attribute macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)