Rollup merge of #144022 - connortsui20:sync_nonpoison, r=tgross35

Implementation: `#[feature(sync_nonpoison)]`, `#[feature(nonpoison_mutex)]`

Continuation of https://github.com/rust-lang/rust/pull/134663

Tracking Issue: https://github.com/rust-lang/rust/issues/134645

This PR implements a new `sync/nonpoison` module, as well as the `nonpoison` variant of the `Mutex` lock.

There are 2 main changes here, the first is the new `nonpoison::mutex` module, and the second is the `mutex` integration tests.

For the `nonpoison::mutex` module, I did my best to align it with the current state of the `poison::mutex` module. This means that several unstable features (`mapped_lock_guards`, `lock_value_accessors`, and `mutex_data_ptr`) are also in the new `nonpoison::mutex` module, under their respective feature gates. Everything else in that file is under the correct feature gate (`#[unstable(feature = "nonpoison_mutex", issue = "134645")]`).

Everything in the `nonpoison::mutex` file is essentially identical in spirit, as we are simply removing the error case from the original `poison::mutex`.

The second big change is in the integration tests. I created a macro called that allows us to duplicate tests that are "generic" over the different mutex types, in that the poison mutex is always `unwrap`ped.

~~I think that there is an argument against doing this, as it can make the tests a bit harder to understand (and language server capabilities are weaker within macros), but I think the benefit of code deduplication here is worth it. Note that it is definitely possible to generalize this (with a few tweaks) to testing the other `nonpoison` locks when they eventually get implemented, but I'll leave that for a later discussion.~~

8 files changed, 1038 insertions, 202 deletions

diff --git a/library/std/src/sync/mod.rs b/library/std/src/sync/mod.rs
index e67b4f6f22f..6ef3bf25cf6 100644
--- a/library/std/src/sync/mod.rs
+++ b/library/std/src/sync/mod.rs
@@ -225,6 +225,8 @@ pub use self::poison::{MappedMutexGuard, MappedRwLockReadGuard, MappedRwLockWrit
 pub mod mpmc;
 pub mod mpsc;
 
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub mod nonpoison;
 #[unstable(feature = "sync_poison_mod", issue = "134646")]
 pub mod poison;
 
diff --git a/library/std/src/sync/nonpoison.rs b/library/std/src/sync/nonpoison.rs
new file mode 100644
index 00000000000..2bbf226dc2c
--- /dev/null
+++ b/library/std/src/sync/nonpoison.rs
@@ -0,0 +1,37 @@
+//! Non-poisoning synchronous locks.
+//!
+//! The difference from the locks in the [`poison`] module is that the locks in this module will not
+//! become poisoned when a thread panics while holding a guard.
+//!
+//! [`poison`]: super::poison
+
+use crate::fmt;
+
+/// A type alias for the result of a nonblocking locking method.
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub type TryLockResult<Guard> = Result<Guard, WouldBlock>;
+
+/// A lock could not be acquired at this time because the operation would otherwise block.
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub struct WouldBlock;
+
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+impl fmt::Debug for WouldBlock {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "WouldBlock".fmt(f)
+    }
+}
+
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+impl fmt::Display for WouldBlock {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        "try_lock failed because the operation would block".fmt(f)
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+pub use self::mutex::MappedMutexGuard;
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+pub use self::mutex::{Mutex, MutexGuard};
+
+mod mutex;
diff --git a/library/std/src/sync/nonpoison/mutex.rs b/library/std/src/sync/nonpoison/mutex.rs
new file mode 100644
index 00000000000..b6861c78f00
--- /dev/null
+++ b/library/std/src/sync/nonpoison/mutex.rs
@@ -0,0 +1,611 @@
+use crate::cell::UnsafeCell;
+use crate::fmt;
+use crate::marker::PhantomData;
+use crate::mem::{self, ManuallyDrop};
+use crate::ops::{Deref, DerefMut};
+use crate::ptr::NonNull;
+use crate::sync::nonpoison::{TryLockResult, WouldBlock};
+use crate::sys::sync as sys;
+
+/// A mutual exclusion primitive useful for protecting shared data that does not keep track of
+/// lock poisoning.
+///
+/// For more information about mutexes, check out the documentation for the poisoning variant of
+/// this lock at [`poison::Mutex`].
+///
+/// [`poison::Mutex`]: crate::sync::poison::Mutex
+///
+/// # Examples
+///
+/// Note that this `Mutex` does **not** propagate threads that panic while holding the lock via
+/// poisoning. If you need this functionality, see [`poison::Mutex`].
+///
+/// ```
+/// #![feature(nonpoison_mutex)]
+///
+/// use std::thread;
+/// use std::sync::{Arc, nonpoison::Mutex};
+///
+/// let mutex = Arc::new(Mutex::new(0u32));
+/// let mut handles = Vec::new();
+///
+/// for n in 0..10 {
+///     let m = Arc::clone(&mutex);
+///     let handle = thread::spawn(move || {
+///         let mut guard = m.lock();
+///         *guard += 1;
+///         panic!("panic from thread {n} {guard}")
+///     });
+///     handles.push(handle);
+/// }
+///
+/// for h in handles {
+///     let _ = h.join();
+/// }
+///
+/// println!("Finished, locked {} times", mutex.lock());
+/// ```
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "NonPoisonMutex")]
+pub struct Mutex<T: ?Sized> {
+    inner: sys::Mutex,
+    data: UnsafeCell<T>,
+}
+
+/// `T` must be `Send` for a [`Mutex`] to be `Send` because it is possible to acquire
+/// the owned `T` from the `Mutex` via [`into_inner`].
+///
+/// [`into_inner`]: Mutex::into_inner
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+unsafe impl<T: ?Sized + Send> Send for Mutex<T> {}
+
+/// `T` must be `Send` for [`Mutex`] to be `Sync`.
+/// This ensures that the protected data can be accessed safely from multiple threads
+/// without causing data races or other unsafe behavior.
+///
+/// [`Mutex<T>`] provides mutable access to `T` to one thread at a time. However, it's essential
+/// for `T` to be `Send` because it's not safe for non-`Send` structures to be accessed in
+/// this manner. For instance, consider [`Rc`], a non-atomic reference counted smart pointer,
+/// which is not `Send`. With `Rc`, we can have multiple copies pointing to the same heap
+/// allocation with a non-atomic reference count. If we were to use `Mutex<Rc<_>>`, it would
+/// only protect one instance of `Rc` from shared access, leaving other copies vulnerable
+/// to potential data races.
+///
+/// Also note that it is not necessary for `T` to be `Sync` as `&T` is only made available
+/// to one thread at a time if `T` is not `Sync`.
+///
+/// [`Rc`]: crate::rc::Rc
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+unsafe impl<T: ?Sized + Send> Sync for Mutex<T> {}
+
+/// An RAII implementation of a "scoped lock" of a mutex. When this structure is
+/// dropped (falls out of scope), the lock will be unlocked.
+///
+/// The data protected by the mutex can be accessed through this guard via its
+/// [`Deref`] and [`DerefMut`] implementations.
+///
+/// This structure is created by the [`lock`] and [`try_lock`] methods on
+/// [`Mutex`].
+///
+/// [`lock`]: Mutex::lock
+/// [`try_lock`]: Mutex::try_lock
+#[must_use = "if unused the Mutex will immediately unlock"]
+#[must_not_suspend = "holding a MutexGuard across suspend \
+                      points can cause deadlocks, delays, \
+                      and cause Futures to not implement `Send`"]
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+#[clippy::has_significant_drop]
+#[cfg_attr(not(test), rustc_diagnostic_item = "NonPoisonMutexGuard")]
+pub struct MutexGuard<'a, T: ?Sized + 'a> {
+    lock: &'a Mutex<T>,
+}
+
+/// A [`MutexGuard`] is not `Send` to maximize platform portablity.
+///
+/// On platforms that use POSIX threads (commonly referred to as pthreads) there is a requirement to
+/// release mutex locks on the same thread they were acquired.
+/// For this reason, [`MutexGuard`] must not implement `Send` to prevent it being dropped from
+/// another thread.
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized> !Send for MutexGuard<'_, T> {}
+
+/// `T` must be `Sync` for a [`MutexGuard<T>`] to be `Sync`
+/// because it is possible to get a `&T` from `&MutexGuard` (via `Deref`).
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+unsafe impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T> {}
+
+// FIXME(nonpoison_condvar): Use this link instead: [`Condvar`]: crate::sync::nonpoison::Condvar
+/// An RAII mutex guard returned by `MutexGuard::map`, which can point to a
+/// subfield of the protected data. When this structure is dropped (falls out
+/// of scope), the lock will be unlocked.
+///
+/// The main difference between `MappedMutexGuard` and [`MutexGuard`] is that the
+/// former cannot be used with [`Condvar`], since that could introduce soundness issues if the
+/// locked object is modified by another thread while the `Mutex` is unlocked.
+///
+/// The data protected by the mutex can be accessed through this guard via its
+/// [`Deref`] and [`DerefMut`] implementations.
+///
+/// This structure is created by the [`map`] and [`filter_map`] methods on
+/// [`MutexGuard`].
+///
+/// [`map`]: MutexGuard::map
+/// [`filter_map`]: MutexGuard::filter_map
+/// [`Condvar`]: crate::sync::Condvar
+#[must_use = "if unused the Mutex will immediately unlock"]
+#[must_not_suspend = "holding a MappedMutexGuard across suspend \
+                      points can cause deadlocks, delays, \
+                      and cause Futures to not implement `Send`"]
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+// #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+#[clippy::has_significant_drop]
+pub struct MappedMutexGuard<'a, T: ?Sized + 'a> {
+    // NB: we use a pointer instead of `&'a mut T` to avoid `noalias` violations, because a
+    // `MappedMutexGuard` argument doesn't hold uniqueness for its whole scope, only until it drops.
+    // `NonNull` is covariant over `T`, so we add a `PhantomData<&'a mut T>` field
+    // below for the correct variance over `T` (invariance).
+    data: NonNull<T>,
+    inner: &'a sys::Mutex,
+    _variance: PhantomData<&'a mut T>,
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+// #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized> !Send for MappedMutexGuard<'_, T> {}
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+// #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+unsafe impl<T: ?Sized + Sync> Sync for MappedMutexGuard<'_, T> {}
+
+impl<T> Mutex<T> {
+    /// Creates a new mutex in an unlocked state ready for use.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mutex = Mutex::new(0);
+    /// ```
+    #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    #[inline]
+    pub const fn new(t: T) -> Mutex<T> {
+        Mutex { inner: sys::Mutex::new(), data: UnsafeCell::new(t) }
+    }
+
+    /// Returns the contained value by cloning it.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    /// #![feature(lock_value_accessors)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mut mutex = Mutex::new(7);
+    ///
+    /// assert_eq!(mutex.get_cloned(), 7);
+    /// ```
+    #[unstable(feature = "lock_value_accessors", issue = "133407")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn get_cloned(&self) -> T
+    where
+        T: Clone,
+    {
+        self.lock().clone()
+    }
+
+    /// Sets the contained value.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    /// #![feature(lock_value_accessors)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mut mutex = Mutex::new(7);
+    ///
+    /// assert_eq!(mutex.get_cloned(), 7);
+    /// mutex.set(11);
+    /// assert_eq!(mutex.get_cloned(), 11);
+    /// ```
+    #[unstable(feature = "lock_value_accessors", issue = "133407")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn set(&self, value: T) {
+        if mem::needs_drop::<T>() {
+            // If the contained value has a non-trivial destructor, we
+            // call that destructor after the lock has been released.
+            drop(self.replace(value))
+        } else {
+            *self.lock() = value;
+        }
+    }
+
+    /// Replaces the contained value with `value`, and returns the old contained value.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    /// #![feature(lock_value_accessors)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mut mutex = Mutex::new(7);
+    ///
+    /// assert_eq!(mutex.replace(11), 7);
+    /// assert_eq!(mutex.get_cloned(), 11);
+    /// ```
+    #[unstable(feature = "lock_value_accessors", issue = "133407")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn replace(&self, value: T) -> T {
+        let mut guard = self.lock();
+        mem::replace(&mut *guard, value)
+    }
+}
+
+impl<T: ?Sized> Mutex<T> {
+    /// Acquires a mutex, blocking the current thread until it is able to do so.
+    ///
+    /// This function will block the local thread until it is available to acquire
+    /// the mutex. Upon returning, the thread is the only thread with the lock
+    /// held. An RAII guard is returned to allow scoped unlock of the lock. When
+    /// the guard goes out of scope, the mutex will be unlocked.
+    ///
+    /// The exact behavior on locking a mutex in the thread which already holds
+    /// the lock is left unspecified. However, this function will not return on
+    /// the second call (it might panic or deadlock, for example).
+    ///
+    /// # Panics
+    ///
+    /// This function might panic when called if the lock is already held by
+    /// the current thread.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    ///
+    /// use std::sync::{Arc, nonpoison::Mutex};
+    /// use std::thread;
+    ///
+    /// let mutex = Arc::new(Mutex::new(0));
+    /// let c_mutex = Arc::clone(&mutex);
+    ///
+    /// thread::spawn(move || {
+    ///     *c_mutex.lock() = 10;
+    /// }).join().expect("thread::spawn failed");
+    /// assert_eq!(*mutex.lock(), 10);
+    /// ```
+    #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn lock(&self) -> MutexGuard<'_, T> {
+        unsafe {
+            self.inner.lock();
+            MutexGuard::new(self)
+        }
+    }
+
+    /// Attempts to acquire this lock.
+    ///
+    /// This function does not block. If the lock could not be acquired at this time, then
+    /// [`WouldBlock`] is returned. Otherwise, an RAII guard is returned.
+    ///
+    /// The lock will be unlocked when the guard is dropped.
+    ///
+    /// # Errors
+    ///
+    /// If the mutex could not be acquired because it is already locked, then this call will return
+    /// the [`WouldBlock`] error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::{Arc, Mutex};
+    /// use std::thread;
+    ///
+    /// let mutex = Arc::new(Mutex::new(0));
+    /// let c_mutex = Arc::clone(&mutex);
+    ///
+    /// thread::spawn(move || {
+    ///     let mut lock = c_mutex.try_lock();
+    ///     if let Ok(ref mut mutex) = lock {
+    ///         **mutex = 10;
+    ///     } else {
+    ///         println!("try_lock failed");
+    ///     }
+    /// }).join().expect("thread::spawn failed");
+    /// assert_eq!(*mutex.lock().unwrap(), 10);
+    /// ```
+    #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn try_lock(&self) -> TryLockResult<MutexGuard<'_, T>> {
+        unsafe { if self.inner.try_lock() { Ok(MutexGuard::new(self)) } else { Err(WouldBlock) } }
+    }
+
+    /// Consumes this mutex, returning the underlying data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mutex = Mutex::new(0);
+    /// assert_eq!(mutex.into_inner(), 0);
+    /// ```
+    #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn into_inner(self) -> T
+    where
+        T: Sized,
+    {
+        self.data.into_inner()
+    }
+
+    /// Returns a mutable reference to the underlying data.
+    ///
+    /// Since this call borrows the `Mutex` mutably, no actual locking needs to
+    /// take place -- the mutable borrow statically guarantees no locks exist.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(nonpoison_mutex)]
+    ///
+    /// use std::sync::nonpoison::Mutex;
+    ///
+    /// let mut mutex = Mutex::new(0);
+    /// *mutex.get_mut() = 10;
+    /// assert_eq!(*mutex.lock(), 10);
+    /// ```
+    #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn get_mut(&mut self) -> &mut T {
+        self.data.get_mut()
+    }
+
+    /// Returns a raw pointer to the underlying data.
+    ///
+    /// The returned pointer is always non-null and properly aligned, but it is
+    /// the user's responsibility to ensure that any reads and writes through it
+    /// are properly synchronized to avoid data races, and that it is not read
+    /// or written through after the mutex is dropped.
+    #[unstable(feature = "mutex_data_ptr", issue = "140368")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn data_ptr(&self) -> *mut T {
+        self.data.get()
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T> From<T> for Mutex<T> {
+    /// Creates a new mutex in an unlocked state ready for use.
+    /// This is equivalent to [`Mutex::new`].
+    fn from(t: T) -> Self {
+        Mutex::new(t)
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized + Default> Default for Mutex<T> {
+    /// Creates a `Mutex<T>`, with the `Default` value for T.
+    fn default() -> Mutex<T> {
+        Mutex::new(Default::default())
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for Mutex<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut d = f.debug_struct("Mutex");
+        match self.try_lock() {
+            Ok(guard) => {
+                d.field("data", &&*guard);
+            }
+            Err(WouldBlock) => {
+                d.field("data", &"<locked>");
+            }
+        }
+        d.finish_non_exhaustive()
+    }
+}
+
+impl<'mutex, T: ?Sized> MutexGuard<'mutex, T> {
+    unsafe fn new(lock: &'mutex Mutex<T>) -> MutexGuard<'mutex, T> {
+        return MutexGuard { lock };
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized> Deref for MutexGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.lock.data.get() }
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized> DerefMut for MutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.lock.data.get() }
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized> Drop for MutexGuard<'_, T> {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            self.lock.inner.unlock();
+        }
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for MutexGuard<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "nonpoison_mutex", issue = "134645")]
+impl<T: ?Sized + fmt::Display> fmt::Display for MutexGuard<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<'a, T: ?Sized> MutexGuard<'a, T> {
+    /// Makes a [`MappedMutexGuard`] for a component of the borrowed data, e.g.
+    /// an enum variant.
+    ///
+    /// The `Mutex` is already locked, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `MutexGuard::map(...)`. A method would interfere with methods of the
+    /// same name on the contents of the `MutexGuard` used through `Deref`.
+    #[unstable(feature = "mapped_lock_guards", issue = "117108")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn map<U, F>(orig: Self, f: F) -> MappedMutexGuard<'a, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+        U: ?Sized,
+    {
+        // SAFETY: the conditions of `MutexGuard::new` were satisfied when the original guard
+        // was created, and have been upheld throughout `map` and/or `filter_map`.
+        // The signature of the closure guarantees that it will not "leak" the lifetime of the reference
+        // passed to it. If the closure panics, the guard will be dropped.
+        let data = NonNull::from(f(unsafe { &mut *orig.lock.data.get() }));
+        let orig = ManuallyDrop::new(orig);
+        MappedMutexGuard { data, inner: &orig.lock.inner, _variance: PhantomData }
+    }
+
+    /// Makes a [`MappedMutexGuard`] for a component of the borrowed data. The
+    /// original guard is returned as an `Err(...)` if the closure returns
+    /// `None`.
+    ///
+    /// The `Mutex` is already locked, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `MutexGuard::filter_map(...)`. A method would interfere with methods of the
+    /// same name on the contents of the `MutexGuard` used through `Deref`.
+    #[unstable(feature = "mapped_lock_guards", issue = "117108")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedMutexGuard<'a, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+        U: ?Sized,
+    {
+        // SAFETY: the conditions of `MutexGuard::new` were satisfied when the original guard
+        // was created, and have been upheld throughout `map` and/or `filter_map`.
+        // The signature of the closure guarantees that it will not "leak" the lifetime of the reference
+        // passed to it. If the closure panics, the guard will be dropped.
+        match f(unsafe { &mut *orig.lock.data.get() }) {
+            Some(data) => {
+                let data = NonNull::from(data);
+                let orig = ManuallyDrop::new(orig);
+                Ok(MappedMutexGuard { data, inner: &orig.lock.inner, _variance: PhantomData })
+            }
+            None => Err(orig),
+        }
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+impl<T: ?Sized> Deref for MappedMutexGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { self.data.as_ref() }
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+impl<T: ?Sized> DerefMut for MappedMutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { self.data.as_mut() }
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+impl<T: ?Sized> Drop for MappedMutexGuard<'_, T> {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            self.inner.unlock();
+        }
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+impl<T: ?Sized + fmt::Debug> fmt::Debug for MappedMutexGuard<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "mapped_lock_guards", issue = "117108")]
+impl<T: ?Sized + fmt::Display> fmt::Display for MappedMutexGuard<'_, T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
+impl<'a, T: ?Sized> MappedMutexGuard<'a, T> {
+    /// Makes a [`MappedMutexGuard`] for a component of the borrowed data, e.g.
+    /// an enum variant.
+    ///
+    /// The `Mutex` is already locked, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `MappedMutexGuard::map(...)`. A method would interfere with methods of the
+    /// same name on the contents of the `MutexGuard` used through `Deref`.
+    #[unstable(feature = "mapped_lock_guards", issue = "117108")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn map<U, F>(mut orig: Self, f: F) -> MappedMutexGuard<'a, U>
+    where
+        F: FnOnce(&mut T) -> &mut U,
+        U: ?Sized,
+    {
+        // SAFETY: the conditions of `MutexGuard::new` were satisfied when the original guard
+        // was created, and have been upheld throughout `map` and/or `filter_map`.
+        // The signature of the closure guarantees that it will not "leak" the lifetime of the reference
+        // passed to it. If the closure panics, the guard will be dropped.
+        let data = NonNull::from(f(unsafe { orig.data.as_mut() }));
+        let orig = ManuallyDrop::new(orig);
+        MappedMutexGuard { data, inner: orig.inner, _variance: PhantomData }
+    }
+
+    /// Makes a [`MappedMutexGuard`] for a component of the borrowed data. The
+    /// original guard is returned as an `Err(...)` if the closure returns
+    /// `None`.
+    ///
+    /// The `Mutex` is already locked, so this cannot fail.
+    ///
+    /// This is an associated function that needs to be used as
+    /// `MappedMutexGuard::filter_map(...)`. A method would interfere with methods of the
+    /// same name on the contents of the `MutexGuard` used through `Deref`.
+    #[unstable(feature = "mapped_lock_guards", issue = "117108")]
+    // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
+    pub fn filter_map<U, F>(mut orig: Self, f: F) -> Result<MappedMutexGuard<'a, U>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut U>,
+        U: ?Sized,
+    {
+        // SAFETY: the conditions of `MutexGuard::new` were satisfied when the original guard
+        // was created, and have been upheld throughout `map` and/or `filter_map`.
+        // The signature of the closure guarantees that it will not "leak" the lifetime of the reference
+        // passed to it. If the closure panics, the guard will be dropped.
+        match f(unsafe { orig.data.as_mut() }) {
+            Some(data) => {
+                let data = NonNull::from(data);
+                let orig = ManuallyDrop::new(orig);
+                Ok(MappedMutexGuard { data, inner: orig.inner, _variance: PhantomData })
+            }
+            None => Err(orig),
+        }
+    }
+}
diff --git a/library/std/src/sync/poison.rs b/library/std/src/sync/poison.rs
index 0c05f152ef8..b901a5701a4 100644
--- a/library/std/src/sync/poison.rs
+++ b/library/std/src/sync/poison.rs
@@ -13,7 +13,9 @@
 //! depend on the primitive. See [#Overview] below.
 //!
 //! For the alternative implementations that do not employ poisoning,
-//! see `std::sync::nonpoisoning`.
+//! see [`std::sync::nonpoison`].
+//!
+//! [`std::sync::nonpoison`]: crate::sync::nonpoison
 //!
 //! # Overview
 //!
@@ -56,8 +58,6 @@
 //!   while it is locked exclusively (write mode). If a panic occurs in any reader,
 //!   then the lock will not be poisoned.
 
-// FIXME(sync_nonpoison) add links to sync::nonpoison to the doc comment above.
-
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::condvar::{Condvar, WaitTimeoutResult};
 #[unstable(feature = "mapped_lock_guards", issue = "117108")]
diff --git a/library/std/src/sync/poison/condvar.rs b/library/std/src/sync/poison/condvar.rs
index 7f0f3f652bc..0e9d4233c65 100644
--- a/library/std/src/sync/poison/condvar.rs
+++ b/library/std/src/sync/poison/condvar.rs
@@ -13,7 +13,7 @@ use crate::time::{Duration, Instant};
 #[stable(feature = "wait_timeout", since = "1.5.0")]
 pub struct WaitTimeoutResult(bool);
 
-// FIXME(sync_nonpoison): `WaitTimeoutResult` is actually poisoning-agnostic, it seems.
+// FIXME(nonpoison_condvar): `WaitTimeoutResult` is actually poisoning-agnostic, it seems.
 // Should we take advantage of this fact?
 impl WaitTimeoutResult {
     /// Returns `true` if the wait was known to have timed out.
diff --git a/library/std/src/sync/poison/mutex.rs b/library/std/src/sync/poison/mutex.rs
index 30325be685c..64744f18c74 100644
--- a/library/std/src/sync/poison/mutex.rs
+++ b/library/std/src/sync/poison/mutex.rs
@@ -650,7 +650,7 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for Mutex<T> {
                 d.field("data", &&**err.get_ref());
             }
             Err(TryLockError::WouldBlock) => {
-                d.field("data", &format_args!("<locked>"));
+                d.field("data", &"<locked>");
             }
         }
         d.field("poisoned", &self.poison.get());
diff --git a/library/std/tests/sync/lib.rs b/library/std/tests/sync/lib.rs
index 51190f0894f..94f1fe96b6a 100644
--- a/library/std/tests/sync/lib.rs
+++ b/library/std/tests/sync/lib.rs
@@ -6,7 +6,10 @@
 #![feature(reentrant_lock)]
 #![feature(rwlock_downgrade)]
 #![feature(std_internals)]
+#![feature(sync_nonpoison)]
+#![feature(nonpoison_mutex)]
 #![allow(internal_features)]
+#![feature(macro_metavar_expr_concat)] // For concatenating identifiers in macros.
 
 mod barrier;
 mod condvar;
@@ -29,3 +32,55 @@ mod rwlock;
 
 #[path = "../common/mod.rs"]
 mod common;
+
+#[track_caller]
+fn result_unwrap<T, E: std::fmt::Debug>(x: Result<T, E>) -> T {
+    x.unwrap()
+}
+
+/// A macro that generates two test cases for both the poison and nonpoison locks.
+///
+/// To write a test that tests both `poison` and `nonpoison` locks, import any of the types
+/// under both `poison` and `nonpoison` using the module name `locks` instead. For example, write
+/// `use locks::Mutex;` instead of `use std::sync::poiosn::Mutex`. This will import the correct type
+/// for each test variant.
+///
+/// Write a test as normal in the `test_body`, but instead of calling `unwrap` on `poison` methods
+/// that return a `LockResult` or similar, call the function `maybe_unwrap(...)` on the result.
+///
+/// For example, call `maybe_unwrap(mutex.lock())` instead of `mutex.lock().unwrap()` or
+/// `maybe_unwrap(rwlock.read())` instead of `rwlock.read().unwrap()`.
+///
+/// For the `poison` types, `maybe_unwrap` will simply unwrap the `Result` (usually this is a form
+/// of `LockResult`, but it could also be other kinds of results). For the `nonpoison` types, it is
+/// a no-op (the identity function).
+///
+/// The test names will be prefiex with `poison_` or `nonpoison_`.
+macro_rules! nonpoison_and_poison_unwrap_test {
+    (
+        name: $name:ident,
+        test_body: {$($test_body:tt)*}
+    ) => {
+        // Creates the nonpoison test.
+        #[test]
+        fn ${concat(nonpoison_, $name)}() {
+            #[allow(unused_imports)]
+            use ::std::convert::identity as maybe_unwrap;
+            use ::std::sync::nonpoison as locks;
+
+            $($test_body)*
+        }
+
+        // Creates the poison test with the suffix `_unwrap_poisoned`.
+        #[test]
+        fn ${concat(poison_, $name)}() {
+            #[allow(unused_imports)]
+            use super::result_unwrap as maybe_unwrap;
+            use ::std::sync::poison as locks;
+
+            $($test_body)*
+        }
+    }
+}
+
+use nonpoison_and_poison_unwrap_test;
diff --git a/library/std/tests/sync/mutex.rs b/library/std/tests/sync/mutex.rs
index ac82914d6de..90cefc0d594 100644
--- a/library/std/tests/sync/mutex.rs
+++ b/library/std/tests/sync/mutex.rs
@@ -6,7 +6,71 @@ use std::sync::mpsc::channel;
 use std::sync::{Arc, Condvar, MappedMutexGuard, Mutex, MutexGuard, TryLockError};
 use std::{hint, mem, thread};
 
-struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Nonpoison & Poison Tests
+////////////////////////////////////////////////////////////////////////////////////////////////////
+use super::nonpoison_and_poison_unwrap_test;
+
+nonpoison_and_poison_unwrap_test!(
+    name: smoke,
+    test_body: {
+        use locks::Mutex;
+
+        let m = Mutex::new(());
+        drop(maybe_unwrap(m.lock()));
+        drop(maybe_unwrap(m.lock()));
+    }
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: lots_and_lots,
+    test_body: {
+        use locks::Mutex;
+
+        const J: u32 = 1000;
+        const K: u32 = 3;
+
+        let m = Arc::new(Mutex::new(0));
+
+        fn inc(m: &Mutex<u32>) {
+            for _ in 0..J {
+                *maybe_unwrap(m.lock()) += 1;
+            }
+        }
+
+        let (tx, rx) = channel();
+        for _ in 0..K {
+            let tx2 = tx.clone();
+            let m2 = m.clone();
+            thread::spawn(move || {
+                inc(&m2);
+                tx2.send(()).unwrap();
+            });
+            let tx2 = tx.clone();
+            let m2 = m.clone();
+            thread::spawn(move || {
+                inc(&m2);
+                tx2.send(()).unwrap();
+            });
+        }
+
+        drop(tx);
+        for _ in 0..2 * K {
+            rx.recv().unwrap();
+        }
+        assert_eq!(*maybe_unwrap(m.lock()), J * K * 2);
+    }
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: try_lock,
+    test_body: {
+        use locks::Mutex;
+
+        let m = Mutex::new(());
+        *m.try_lock().unwrap() = ();
+    }
+);
 
 #[derive(Eq, PartialEq, Debug)]
 struct NonCopy(i32);
@@ -26,58 +90,278 @@ fn test_needs_drop() {
     assert!(mem::needs_drop::<NonCopyNeedsDrop>());
 }
 
-#[derive(Clone, Eq, PartialEq, Debug)]
-struct Cloneable(i32);
+nonpoison_and_poison_unwrap_test!(
+    name: test_into_inner,
+    test_body: {
+        use locks::Mutex;
 
-#[test]
-fn smoke() {
-    let m = Mutex::new(());
-    drop(m.lock().unwrap());
-    drop(m.lock().unwrap());
-}
+        let m = Mutex::new(NonCopy(10));
+        assert_eq!(maybe_unwrap(m.into_inner()), NonCopy(10));
+    }
+);
 
-#[test]
-fn lots_and_lots() {
-    const J: u32 = 1000;
-    const K: u32 = 3;
+nonpoison_and_poison_unwrap_test!(
+    name: test_into_inner_drop,
+    test_body: {
+        use locks::Mutex;
 
-    let m = Arc::new(Mutex::new(0));
+        struct Foo(Arc<AtomicUsize>);
+        impl Drop for Foo {
+            fn drop(&mut self) {
+                self.0.fetch_add(1, Ordering::SeqCst);
+            }
+        }
 
-    fn inc(m: &Mutex<u32>) {
-        for _ in 0..J {
-            *m.lock().unwrap() += 1;
+        let num_drops = Arc::new(AtomicUsize::new(0));
+        let m = Mutex::new(Foo(num_drops.clone()));
+        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
+        {
+            let _inner = maybe_unwrap(m.into_inner());
+            assert_eq!(num_drops.load(Ordering::SeqCst), 0);
         }
+        assert_eq!(num_drops.load(Ordering::SeqCst), 1);
     }
+);
 
-    let (tx, rx) = channel();
-    for _ in 0..K {
-        let tx2 = tx.clone();
-        let m2 = m.clone();
-        thread::spawn(move || {
-            inc(&m2);
-            tx2.send(()).unwrap();
-        });
-        let tx2 = tx.clone();
-        let m2 = m.clone();
-        thread::spawn(move || {
-            inc(&m2);
-            tx2.send(()).unwrap();
-        });
+nonpoison_and_poison_unwrap_test!(
+    name: test_get_mut,
+    test_body: {
+        use locks::Mutex;
+
+        let mut m = Mutex::new(NonCopy(10));
+        *maybe_unwrap(m.get_mut()) = NonCopy(20);
+        assert_eq!(maybe_unwrap(m.into_inner()), NonCopy(20));
     }
+);
 
-    drop(tx);
-    for _ in 0..2 * K {
-        rx.recv().unwrap();
+nonpoison_and_poison_unwrap_test!(
+    name: test_get_cloned,
+    test_body: {
+        use locks::Mutex;
+
+        #[derive(Clone, Eq, PartialEq, Debug)]
+        struct Cloneable(i32);
+
+        let m = Mutex::new(Cloneable(10));
+
+        assert_eq!(maybe_unwrap(m.get_cloned()), Cloneable(10));
     }
-    assert_eq!(*m.lock().unwrap(), J * K * 2);
-}
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: test_set,
+    test_body: {
+        use locks::Mutex;
+
+        fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
+        where
+            T: Debug + Eq,
+        {
+            let m = Mutex::new(init());
+
+            assert_eq!(*maybe_unwrap(m.lock()), init());
+            maybe_unwrap(m.set(value()));
+            assert_eq!(*maybe_unwrap(m.lock()), value());
+        }
+
+        inner(|| NonCopy(10), || NonCopy(20));
+        inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
+    }
+);
+
+// Ensure that old values that are replaced by `set` are correctly dropped.
+nonpoison_and_poison_unwrap_test!(
+    name: test_set_drop,
+    test_body: {
+        use locks::Mutex;
+
+        struct Foo(Arc<AtomicUsize>);
+        impl Drop for Foo {
+            fn drop(&mut self) {
+                self.0.fetch_add(1, Ordering::SeqCst);
+            }
+        }
+
+        let num_drops = Arc::new(AtomicUsize::new(0));
+        let m = Mutex::new(Foo(num_drops.clone()));
+        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
+
+        let different = Foo(Arc::new(AtomicUsize::new(42)));
+        maybe_unwrap(m.set(different));
+        assert_eq!(num_drops.load(Ordering::SeqCst), 1);
+    }
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: test_replace,
+    test_body: {
+        use locks::Mutex;
+
+        fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
+        where
+            T: Debug + Eq,
+        {
+            let m = Mutex::new(init());
+
+            assert_eq!(*maybe_unwrap(m.lock()), init());
+            assert_eq!(maybe_unwrap(m.replace(value())), init());
+            assert_eq!(*maybe_unwrap(m.lock()), value());
+        }
 
+        inner(|| NonCopy(10), || NonCopy(20));
+        inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
+    }
+);
+
+// FIXME(nonpoison_condvar): Move this to the `condvar.rs` test file once `nonpoison::condvar` gets
+// implemented.
 #[test]
-fn try_lock() {
-    let m = Mutex::new(());
-    *m.try_lock().unwrap() = ();
+fn test_mutex_arc_condvar() {
+    struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
+
+    let packet = Packet(Arc::new((Mutex::new(false), Condvar::new())));
+    let packet2 = Packet(packet.0.clone());
+
+    let (tx, rx) = channel();
+
+    let _t = thread::spawn(move || {
+        // Wait until our parent has taken the lock.
+        rx.recv().unwrap();
+        let &(ref lock, ref cvar) = &*packet2.0;
+
+        // Set the data to `true` and wake up our parent.
+        let mut guard = lock.lock().unwrap();
+        *guard = true;
+        cvar.notify_one();
+    });
+
+    let &(ref lock, ref cvar) = &*packet.0;
+    let mut guard = lock.lock().unwrap();
+    // Wake up our child.
+    tx.send(()).unwrap();
+
+    // Wait until our child has set the data to `true`.
+    assert!(!*guard);
+    while !*guard {
+        guard = cvar.wait(guard).unwrap();
+    }
 }
 
+nonpoison_and_poison_unwrap_test!(
+    name: test_mutex_arc_nested,
+    test_body: {
+        use locks::Mutex;
+
+        // Tests nested mutexes and access
+        // to underlying data.
+        let arc = Arc::new(Mutex::new(1));
+        let arc2 = Arc::new(Mutex::new(arc));
+        let (tx, rx) = channel();
+        let _t = thread::spawn(move || {
+            let lock = maybe_unwrap(arc2.lock());
+            let lock2 = maybe_unwrap(lock.lock());
+            assert_eq!(*lock2, 1);
+            tx.send(()).unwrap();
+        });
+        rx.recv().unwrap();
+    }
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: test_mutex_unsized,
+    test_body: {
+        use locks::Mutex;
+
+        let mutex: &Mutex<[i32]> = &Mutex::new([1, 2, 3]);
+        {
+            let b = &mut *maybe_unwrap(mutex.lock());
+            b[0] = 4;
+            b[2] = 5;
+        }
+        let comp: &[i32] = &[4, 2, 5];
+        assert_eq!(&*maybe_unwrap(mutex.lock()), comp);
+    }
+);
+
+nonpoison_and_poison_unwrap_test!(
+    name: test_mapping_mapped_guard,
+    test_body: {
+        use locks::{Mutex, MutexGuard, MappedMutexGuard};
+
+        let arr = [0; 4];
+        let lock = Mutex::new(arr);
+        let guard = maybe_unwrap(lock.lock());
+        let guard = MutexGuard::map(guard, |arr| &mut arr[..2]);
+        let mut guard = MappedMutexGuard::map(guard, |slice| &mut slice[1..]);
+        assert_eq!(guard.len(), 1);
+        guard[0] = 42;
+        drop(guard);
+        assert_eq!(*maybe_unwrap(lock.lock()), [0, 42, 0, 0]);
+    }
+);
+
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
+nonpoison_and_poison_unwrap_test!(
+    name: test_panics,
+    test_body: {
+        use locks::Mutex;
+
+        let mutex = Mutex::new(42);
+
+        let catch_unwind_result1 = panic::catch_unwind(AssertUnwindSafe(|| {
+            let _guard1 = maybe_unwrap(mutex.lock());
+
+            panic!("test panic with mutex once");
+        }));
+        assert!(catch_unwind_result1.is_err());
+
+        let catch_unwind_result2 = panic::catch_unwind(AssertUnwindSafe(|| {
+            let _guard2 = maybe_unwrap(mutex.lock());
+
+            panic!("test panic with mutex twice");
+        }));
+        assert!(catch_unwind_result2.is_err());
+
+        let catch_unwind_result3 = panic::catch_unwind(AssertUnwindSafe(|| {
+            let _guard3 = maybe_unwrap(mutex.lock());
+
+            panic!("test panic with mutex thrice");
+        }));
+        assert!(catch_unwind_result3.is_err());
+    }
+);
+
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
+nonpoison_and_poison_unwrap_test!(
+    name: test_mutex_arc_access_in_unwind,
+    test_body: {
+        use locks::Mutex;
+
+        let arc = Arc::new(Mutex::new(1));
+        let arc2 = arc.clone();
+        let _ = thread::spawn(move || -> () {
+            struct Unwinder {
+                i: Arc<Mutex<i32>>,
+            }
+            impl Drop for Unwinder {
+                fn drop(&mut self) {
+                    *maybe_unwrap(self.i.lock()) += 1;
+                }
+            }
+            let _u = Unwinder { i: arc2 };
+            panic!();
+        })
+        .join();
+        let lock = maybe_unwrap(arc.lock());
+        assert_eq!(*lock, 2);
+    }
+);
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Poison Tests
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Creates a mutex that is immediately poisoned.
 fn new_poisoned_mutex<T>(value: T) -> Mutex<T> {
     let mutex = Mutex::new(value);
 
@@ -94,30 +378,6 @@ fn new_poisoned_mutex<T>(value: T) -> Mutex<T> {
 }
 
 #[test]
-fn test_into_inner() {
-    let m = Mutex::new(NonCopy(10));
-    assert_eq!(m.into_inner().unwrap(), NonCopy(10));
-}
-
-#[test]
-fn test_into_inner_drop() {
-    struct Foo(Arc<AtomicUsize>);
-    impl Drop for Foo {
-        fn drop(&mut self) {
-            self.0.fetch_add(1, Ordering::SeqCst);
-        }
-    }
-    let num_drops = Arc::new(AtomicUsize::new(0));
-    let m = Mutex::new(Foo(num_drops.clone()));
-    assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    {
-        let _inner = m.into_inner().unwrap();
-        assert_eq!(num_drops.load(Ordering::SeqCst), 0);
-    }
-    assert_eq!(num_drops.load(Ordering::SeqCst), 1);
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_into_inner_poison() {
     let m = new_poisoned_mutex(NonCopy(10));
@@ -129,15 +389,11 @@ fn test_into_inner_poison() {
 }
 
 #[test]
-fn test_get_cloned() {
-    let m = Mutex::new(Cloneable(10));
-
-    assert_eq!(m.get_cloned().unwrap(), Cloneable(10));
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_get_cloned_poison() {
+    #[derive(Clone, Eq, PartialEq, Debug)]
+    struct Cloneable(i32);
+
     let m = new_poisoned_mutex(Cloneable(10));
 
     match m.get_cloned() {
@@ -147,13 +403,6 @@ fn test_get_cloned_poison() {
 }
 
 #[test]
-fn test_get_mut() {
-    let mut m = Mutex::new(NonCopy(10));
-    *m.get_mut().unwrap() = NonCopy(20);
-    assert_eq!(m.into_inner().unwrap(), NonCopy(20));
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_get_mut_poison() {
     let mut m = new_poisoned_mutex(NonCopy(10));
@@ -165,23 +414,6 @@ fn test_get_mut_poison() {
 }
 
 #[test]
-fn test_set() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = Mutex::new(init());
-
-        assert_eq!(*m.lock().unwrap(), init());
-        m.set(value()).unwrap();
-        assert_eq!(*m.lock().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_set_poison() {
     fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
@@ -204,23 +436,6 @@ fn test_set_poison() {
 }
 
 #[test]
-fn test_replace() {
-    fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
-    where
-        T: Debug + Eq,
-    {
-        let m = Mutex::new(init());
-
-        assert_eq!(*m.lock().unwrap(), init());
-        assert_eq!(m.replace(value()).unwrap(), init());
-        assert_eq!(*m.lock().unwrap(), value());
-    }
-
-    inner(|| NonCopy(10), || NonCopy(20));
-    inner(|| NonCopyNeedsDrop(10), || NonCopyNeedsDrop(20));
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_replace_poison() {
     fn inner<T>(mut init: impl FnMut() -> T, mut value: impl FnMut() -> T)
@@ -243,31 +458,10 @@ fn test_replace_poison() {
 }
 
 #[test]
-fn test_mutex_arc_condvar() {
-    let packet = Packet(Arc::new((Mutex::new(false), Condvar::new())));
-    let packet2 = Packet(packet.0.clone());
-    let (tx, rx) = channel();
-    let _t = thread::spawn(move || {
-        // wait until parent gets in
-        rx.recv().unwrap();
-        let &(ref lock, ref cvar) = &*packet2.0;
-        let mut lock = lock.lock().unwrap();
-        *lock = true;
-        cvar.notify_one();
-    });
-
-    let &(ref lock, ref cvar) = &*packet.0;
-    let mut lock = lock.lock().unwrap();
-    tx.send(()).unwrap();
-    assert!(!*lock);
-    while !*lock {
-        lock = cvar.wait(lock).unwrap();
-    }
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn test_arc_condvar_poison() {
+    struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
+
     let packet = Packet(Arc::new((Mutex::new(1), Condvar::new())));
     let packet2 = Packet(packet.0.clone());
     let (tx, rx) = channel();
@@ -327,69 +521,6 @@ fn test_mutex_arc_poison_mapped() {
 }
 
 #[test]
-fn test_mutex_arc_nested() {
-    // Tests nested mutexes and access
-    // to underlying data.
-    let arc = Arc::new(Mutex::new(1));
-    let arc2 = Arc::new(Mutex::new(arc));
-    let (tx, rx) = channel();
-    let _t = thread::spawn(move || {
-        let lock = arc2.lock().unwrap();
-        let lock2 = lock.lock().unwrap();
-        assert_eq!(*lock2, 1);
-        tx.send(()).unwrap();
-    });
-    rx.recv().unwrap();
-}
-
-#[test]
-#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
-fn test_mutex_arc_access_in_unwind() {
-    let arc = Arc::new(Mutex::new(1));
-    let arc2 = arc.clone();
-    let _ = thread::spawn(move || -> () {
-        struct Unwinder {
-            i: Arc<Mutex<i32>>,
-        }
-        impl Drop for Unwinder {
-            fn drop(&mut self) {
-                *self.i.lock().unwrap() += 1;
-            }
-        }
-        let _u = Unwinder { i: arc2 };
-        panic!();
-    })
-    .join();
-    let lock = arc.lock().unwrap();
-    assert_eq!(*lock, 2);
-}
-
-#[test]
-fn test_mutex_unsized() {
-    let mutex: &Mutex<[i32]> = &Mutex::new([1, 2, 3]);
-    {
-        let b = &mut *mutex.lock().unwrap();
-        b[0] = 4;
-        b[2] = 5;
-    }
-    let comp: &[i32] = &[4, 2, 5];
-    assert_eq!(&*mutex.lock().unwrap(), comp);
-}
-
-#[test]
-fn test_mapping_mapped_guard() {
-    let arr = [0; 4];
-    let mut lock = Mutex::new(arr);
-    let guard = lock.lock().unwrap();
-    let guard = MutexGuard::map(guard, |arr| &mut arr[..2]);
-    let mut guard = MappedMutexGuard::map(guard, |slice| &mut slice[1..]);
-    assert_eq!(guard.len(), 1);
-    guard[0] = 42;
-    drop(guard);
-    assert_eq!(*lock.get_mut().unwrap(), [0, 42, 0, 0]);
-}
-
-#[test]
 #[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn panic_while_mapping_unlocked_poison() {
     let lock = Mutex::new(());