Move UnwindSafe, RefUnwindSafe, AssertUnwindSafe to core

1 files changed, 4 insertions, 309 deletions

diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index 9c597e17bb5..c1c03958497 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -3,19 +3,9 @@
 #![stable(feature = "std_panic", since = "1.9.0")]
 
 use crate::any::Any;
-use crate::cell::UnsafeCell;
 use crate::collections;
-use crate::fmt;
-use crate::future::Future;
-use crate::ops::{Deref, DerefMut};
 use crate::panicking;
-use crate::pin::Pin;
-use crate::ptr::{NonNull, Unique};
-use crate::rc::Rc;
-use crate::stream::Stream;
-use crate::sync::atomic;
-use crate::sync::{Arc, Mutex, RwLock};
-use crate::task::{Context, Poll};
+use crate::sync::{Mutex, RwLock};
 use crate::thread::Result;
 
 #[doc(hidden)]
@@ -45,6 +35,9 @@ pub use crate::panicking::{set_hook, take_hook};
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 pub use core::panic::{Location, PanicInfo};
 
+#[stable(feature = "catch_unwind", since = "1.9.0")]
+pub use core::panic::{AssertUnwindSafe, RefUnwindSafe, UnwindSafe};
+
 /// Panic the current thread with the given message as the panic payload.
 ///
 /// The message can be of any (`Any + Send`) type, not just strings.
@@ -60,259 +53,16 @@ pub fn panic_any<M: 'static + Any + Send>(msg: M) -> ! {
     crate::panicking::begin_panic(msg);
 }
 
-/// A marker trait which represents "panic safe" types in Rust.
-///
-/// This trait is implemented by default for many types and behaves similarly in
-/// terms of inference of implementation to the [`Send`] and [`Sync`] traits. The
-/// purpose of this trait is to encode what types are safe to cross a [`catch_unwind`]
-/// boundary with no fear of unwind safety.
-///
-/// ## What is unwind safety?
-///
-/// In Rust a function can "return" early if it either panics or calls a
-/// function which transitively panics. This sort of control flow is not always
-/// anticipated, and has the possibility of causing subtle bugs through a
-/// combination of two critical components:
-///
-/// 1. A data structure is in a temporarily invalid state when the thread
-///    panics.
-/// 2. This broken invariant is then later observed.
-///
-/// Typically in Rust, it is difficult to perform step (2) because catching a
-/// panic involves either spawning a thread (which in turns makes it difficult
-/// to later witness broken invariants) or using the `catch_unwind` function in this
-/// module. Additionally, even if an invariant is witnessed, it typically isn't a
-/// problem in Rust because there are no uninitialized values (like in C or C++).
-///
-/// It is possible, however, for **logical** invariants to be broken in Rust,
-/// which can end up causing behavioral bugs. Another key aspect of unwind safety
-/// in Rust is that, in the absence of `unsafe` code, a panic cannot lead to
-/// memory unsafety.
-///
-/// That was a bit of a whirlwind tour of unwind safety, but for more information
-/// about unwind safety and how it applies to Rust, see an [associated RFC][rfc].
-///
-/// [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1236-stabilize-catch-panic.md
-///
-/// ## What is `UnwindSafe`?
-///
-/// Now that we've got an idea of what unwind safety is in Rust, it's also
-/// important to understand what this trait represents. As mentioned above, one
-/// way to witness broken invariants is through the `catch_unwind` function in this
-/// module as it allows catching a panic and then re-using the environment of
-/// the closure.
-///
-/// Simply put, a type `T` implements `UnwindSafe` if it cannot easily allow
-/// witnessing a broken invariant through the use of `catch_unwind` (catching a
-/// panic). This trait is an auto trait, so it is automatically implemented for
-/// many types, and it is also structurally composed (e.g., a struct is unwind
-/// safe if all of its components are unwind safe).
-///
-/// Note, however, that this is not an unsafe trait, so there is not a succinct
-/// contract that this trait is providing. Instead it is intended as more of a
-/// "speed bump" to alert users of `catch_unwind` that broken invariants may be
-/// witnessed and may need to be accounted for.
-///
-/// ## Who implements `UnwindSafe`?
-///
-/// Types such as `&mut T` and `&RefCell<T>` are examples which are **not**
-/// unwind safe. The general idea is that any mutable state which can be shared
-/// across `catch_unwind` is not unwind safe by default. This is because it is very
-/// easy to witness a broken invariant outside of `catch_unwind` as the data is
-/// simply accessed as usual.
-///
-/// Types like `&Mutex<T>`, however, are unwind safe because they implement
-/// poisoning by default. They still allow witnessing a broken invariant, but
-/// they already provide their own "speed bumps" to do so.
-///
-/// ## When should `UnwindSafe` be used?
-///
-/// It is not intended that most types or functions need to worry about this trait.
-/// It is only used as a bound on the `catch_unwind` function and as mentioned
-/// above, the lack of `unsafe` means it is mostly an advisory. The
-/// [`AssertUnwindSafe`] wrapper struct can be used to force this trait to be
-/// implemented for any closed over variables passed to `catch_unwind`.
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "unwind_safe_trait")]
-#[rustc_on_unimplemented(
-    message = "the type `{Self}` may not be safely transferred across an unwind boundary",
-    label = "`{Self}` may not be safely transferred across an unwind boundary"
-)]
-pub auto trait UnwindSafe {}
-
-/// A marker trait representing types where a shared reference is considered
-/// unwind safe.
-///
-/// This trait is namely not implemented by [`UnsafeCell`], the root of all
-/// interior mutability.
-///
-/// This is a "helper marker trait" used to provide impl blocks for the
-/// [`UnwindSafe`] trait, for more information see that documentation.
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "ref_unwind_safe_trait")]
-#[rustc_on_unimplemented(
-    message = "the type `{Self}` may contain interior mutability and a reference may not be safely \
-               transferrable across a catch_unwind boundary",
-    label = "`{Self}` may contain interior mutability and a reference may not be safely \
-             transferrable across a catch_unwind boundary"
-)]
-pub auto trait RefUnwindSafe {}
-
-/// A simple wrapper around a type to assert that it is unwind safe.
-///
-/// When using [`catch_unwind`] it may be the case that some of the closed over
-/// variables are not unwind safe. For example if `&mut T` is captured the
-/// compiler will generate a warning indicating that it is not unwind safe. It
-/// might not be the case, however, that this is actually a problem due to the
-/// specific usage of [`catch_unwind`] if unwind safety is specifically taken into
-/// account. This wrapper struct is useful for a quick and lightweight
-/// annotation that a variable is indeed unwind safe.
-///
-/// # Examples
-///
-/// One way to use `AssertUnwindSafe` is to assert that the entire closure
-/// itself is unwind safe, bypassing all checks for all variables:
-///
-/// ```
-/// use std::panic::{self, AssertUnwindSafe};
-///
-/// let mut variable = 4;
-///
-/// // This code will not compile because the closure captures `&mut variable`
-/// // which is not considered unwind safe by default.
-///
-/// // panic::catch_unwind(|| {
-/// //     variable += 3;
-/// // });
-///
-/// // This, however, will compile due to the `AssertUnwindSafe` wrapper
-/// let result = panic::catch_unwind(AssertUnwindSafe(|| {
-///     variable += 3;
-/// }));
-/// // ...
-/// ```
-///
-/// Wrapping the entire closure amounts to a blanket assertion that all captured
-/// variables are unwind safe. This has the downside that if new captures are
-/// added in the future, they will also be considered unwind safe. Therefore,
-/// you may prefer to just wrap individual captures, as shown below. This is
-/// more annotation, but it ensures that if a new capture is added which is not
-/// unwind safe, you will get a compilation error at that time, which will
-/// allow you to consider whether that new capture in fact represent a bug or
-/// not.
-///
-/// ```
-/// use std::panic::{self, AssertUnwindSafe};
-///
-/// let mut variable = 4;
-/// let other_capture = 3;
-///
-/// let result = {
-///     let mut wrapper = AssertUnwindSafe(&mut variable);
-///     panic::catch_unwind(move || {
-///         **wrapper += other_capture;
-///     })
-/// };
-/// // ...
-/// ```
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-pub struct AssertUnwindSafe<T>(#[stable(feature = "catch_unwind", since = "1.9.0")] pub T);
-
-// Implementations of the `UnwindSafe` trait:
-//
-// * By default everything is unwind safe
-// * pointers T contains mutability of some form are not unwind safe
-// * Unique, an owning pointer, lifts an implementation
-// * Types like Mutex/RwLock which are explicitly poisoned are unwind safe
-// * Our custom AssertUnwindSafe wrapper is indeed unwind safe
-
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: ?Sized> !UnwindSafe for &mut T {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for &T {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *const T {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for *mut T {}
-#[unstable(feature = "ptr_internals", issue = "none")]
-impl<T: UnwindSafe + ?Sized> UnwindSafe for Unique<T> {}
-#[stable(feature = "nonnull", since = "1.25.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for NonNull<T> {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: ?Sized> UnwindSafe for Mutex<T> {}
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: ?Sized> UnwindSafe for RwLock<T> {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> UnwindSafe for AssertUnwindSafe<T> {}
-
-// not covered via the Shared impl above b/c the inner contents use
-// Cell/AtomicUsize, but the usage here is unwind safe so we can lift the
-// impl up one level to Arc/Rc itself
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Rc<T> {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Arc<T> {}
-
-// Pretty simple implementations for the `RefUnwindSafe` marker trait,
-// basically just saying that `UnsafeCell` is the
-// only thing which doesn't implement it (which then transitively applies to
-// everything else).
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T: ?Sized> !RefUnwindSafe for UnsafeCell<T> {}
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> RefUnwindSafe for AssertUnwindSafe<T> {}
 
 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
 impl<T: ?Sized> RefUnwindSafe for Mutex<T> {}
 #[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
 impl<T: ?Sized> RefUnwindSafe for RwLock<T> {}
 
-#[cfg(target_has_atomic_load_store = "ptr")]
-#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
-impl RefUnwindSafe for atomic::AtomicIsize {}
-#[cfg(target_has_atomic_load_store = "8")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicI8 {}
-#[cfg(target_has_atomic_load_store = "16")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicI16 {}
-#[cfg(target_has_atomic_load_store = "32")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicI32 {}
-#[cfg(target_has_atomic_load_store = "64")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicI64 {}
-#[cfg(target_has_atomic_load_store = "128")]
-#[unstable(feature = "integer_atomics", issue = "32976")]
-impl RefUnwindSafe for atomic::AtomicI128 {}
-
-#[cfg(target_has_atomic_load_store = "ptr")]
-#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
-impl RefUnwindSafe for atomic::AtomicUsize {}
-#[cfg(target_has_atomic_load_store = "8")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicU8 {}
-#[cfg(target_has_atomic_load_store = "16")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicU16 {}
-#[cfg(target_has_atomic_load_store = "32")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicU32 {}
-#[cfg(target_has_atomic_load_store = "64")]
-#[stable(feature = "integer_atomics_stable", since = "1.34.0")]
-impl RefUnwindSafe for atomic::AtomicU64 {}
-#[cfg(target_has_atomic_load_store = "128")]
-#[unstable(feature = "integer_atomics", issue = "32976")]
-impl RefUnwindSafe for atomic::AtomicU128 {}
-
-#[cfg(target_has_atomic_load_store = "8")]
-#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
-impl RefUnwindSafe for atomic::AtomicBool {}
-
-#[cfg(target_has_atomic_load_store = "ptr")]
-#[stable(feature = "unwind_safe_atomic_refs", since = "1.14.0")]
-impl<T> RefUnwindSafe for atomic::AtomicPtr<T> {}
-
 // https://github.com/rust-lang/rust/issues/62301
 #[stable(feature = "hashbrown", since = "1.36.0")]
 impl<K, V, S> UnwindSafe for collections::HashMap<K, V, S>
@@ -323,61 +73,6 @@ where
 {
 }
 
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> Deref for AssertUnwindSafe<T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        &self.0
-    }
-}
-
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<T> DerefMut for AssertUnwindSafe<T> {
-    fn deref_mut(&mut self) -> &mut T {
-        &mut self.0
-    }
-}
-
-#[stable(feature = "catch_unwind", since = "1.9.0")]
-impl<R, F: FnOnce() -> R> FnOnce<()> for AssertUnwindSafe<F> {
-    type Output = R;
-
-    extern "rust-call" fn call_once(self, _args: ()) -> R {
-        (self.0)()
-    }
-}
-
-#[stable(feature = "std_debug", since = "1.16.0")]
-impl<T: fmt::Debug> fmt::Debug for AssertUnwindSafe<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("AssertUnwindSafe").field(&self.0).finish()
-    }
-}
-
-#[stable(feature = "futures_api", since = "1.36.0")]
-impl<F: Future> Future for AssertUnwindSafe<F> {
-    type Output = F::Output;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let pinned_field = unsafe { Pin::map_unchecked_mut(self, |x| &mut x.0) };
-        F::poll(pinned_field, cx)
-    }
-}
-
-#[unstable(feature = "async_stream", issue = "79024")]
-impl<S: Stream> Stream for AssertUnwindSafe<S> {
-    type Item = S::Item;
-
-    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<S::Item>> {
-        unsafe { self.map_unchecked_mut(|x| &mut x.0) }.poll_next(cx)
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.0.size_hint()
-    }
-}
-
 /// Invokes a closure, capturing the cause of an unwinding panic if one occurs.
 ///
 /// This function will return `Ok` with the closure's result if the closure