add nonpoison::mutex implementation

Adds the equivalent `nonpoison` types to the `poison::mutex` module.
These types and implementations are gated under the `nonpoison_mutex`
feature gate.

Also blesses the ui tests that now have a name conflicts (because these
types no longer have unique names). The full path distinguishes the
different types.

Co-authored-by: Aandreba <aandreba@gmail.com>
Co-authored-by: Trevor Gross <tmgross@umich.edu>

Author: 3 people

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;
 

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;