From ded44ec228b3eaceed820585882414831eb196c0 Mon Sep 17 00:00:00 2001
From: Mica White <botahamec@outlook.com>
Date: Fri, 8 Mar 2024 15:47:40 -0500
Subject: Extra lifetime shenanigans

---
 src/mutex.rs | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

(limited to 'src/mutex.rs')

diff --git a/src/mutex.rs b/src/mutex.rs
index f395055..9298b0c 100644
--- a/src/mutex.rs
+++ b/src/mutex.rs
@@ -1,4 +1,5 @@
 use std::cell::UnsafeCell;
+use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
 
 use lock_api::RawMutex;
@@ -71,12 +72,15 @@ impl<'a, T: ?Sized + 'a, R: RawMutex> DerefMut for MutexRef<'a, T, R> {
 ///
 /// [`lock`]: `Mutex::lock`
 /// [`try_lock`]: `Mutex::try_lock`
-pub struct MutexGuard<'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> {
+pub struct MutexGuard<'a, 'key: 'a, T: ?Sized + 'a, Key: Keyable + 'key, R: RawMutex> {
 	mutex: MutexRef<'a, T, R>,
-	_thread_key: Key,
+	thread_key: Key,
+	_phantom: PhantomData<&'key ()>,
 }
 
-impl<'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> Deref for MutexGuard<'a, T, Key, R> {
+impl<'a, 'key: 'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> Deref
+	for MutexGuard<'a, 'key, T, Key, R>
+{
 	type Target = T;
 
 	fn deref(&self) -> &Self::Target {
@@ -84,19 +88,22 @@ impl<'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> Deref for MutexGuard<'a, T,
 	}
 }
 
-impl<'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> DerefMut for MutexGuard<'a, T, Key, R> {
+impl<'a, 'key: 'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> DerefMut
+	for MutexGuard<'a, 'key, T, Key, R>
+{
 	fn deref_mut(&mut self) -> &mut Self::Target {
 		&mut self.mutex
 	}
 }
 
-impl<'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> MutexGuard<'a, T, Key, R> {
+impl<'a, 'key: 'a, T: ?Sized + 'a, Key: Keyable, R: RawMutex> MutexGuard<'a, 'key, T, Key, R> {
 	/// Create a guard to the given mutex. Undefined if multiple guards to the
 	/// same mutex exist at once.
 	const unsafe fn new(mutex: &'a Mutex<T, R>, thread_key: Key) -> Self {
 		Self {
 			mutex: MutexRef(mutex),
-			_thread_key: thread_key,
+			thread_key,
+			_phantom: PhantomData,
 		}
 	}
 }
@@ -143,7 +150,10 @@ impl<T: ?Sized, R: RawMutex> Mutex<T, R> {
 	/// let key = ThreadKey::lock().unwrap();
 	/// assert_eq!(*mutex.lock(key), 10);
 	/// ```
-	pub fn lock<'s, 'a: 's, Key: Keyable>(&'s self, key: Key) -> MutexGuard<'_, T, Key, R> {
+	pub fn lock<'s, 'a: 's, 'k: 'a, Key: Keyable>(
+		&'s self,
+		key: Key,
+	) -> MutexGuard<'_, 'k, T, Key, R> {
 		self.raw.lock();
 
 		// safety: we just locked the mutex
@@ -187,10 +197,10 @@ impl<T: ?Sized, R: RawMutex> Mutex<T, R> {
 	/// let key = ThreadKey::lock().unwrap();
 	/// assert_eq!(*mutex.lock(key), 10);
 	/// ```
-	pub fn try_lock<'s, 'a: 's, Key: Keyable>(
+	pub fn try_lock<'s, 'a: 's, 'k: 'a, Key: Keyable>(
 		&'s self,
 		key: Key,
-	) -> Option<MutexGuard<'_, T, Key, R>> {
+	) -> Option<MutexGuard<'_, 'k, T, Key, R>> {
 		if self.raw.try_lock() {
 			// safety: we just locked the mutex
 			Some(unsafe { MutexGuard::new(self, key) })
@@ -231,8 +241,11 @@ impl<T: ?Sized, R: RawMutex> Mutex<T, R> {
 	/// let key = Mutex::unlock(guard);
 	/// ```
 	#[allow(clippy::missing_const_for_fn)]
-	pub fn unlock(guard: MutexGuard<'_, T, impl Keyable, R>) {
-		drop(guard);
+	pub fn unlock<'a, 'k: 'a, Key: Keyable + 'k>(guard: MutexGuard<'a, 'k, T, Key, R>) -> Key {
+		unsafe {
+			guard.mutex.0.force_unlock();
+		}
+		guard.thread_key
 	}
 }
 
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