Revert "AutoSafe now implies IntoAutoSafe"

This reverts commit f6cd0c4.

src/guard/auto_safety.rs

@@ -39,7 +39,7 @@ impl<'a, S: ThreadSafety> __<'a, S> {
 }
 
 /// Static thread safety smuggling through `impl AutoSafe` returns for [`Guard`] instances.
-pub trait AutoSafe: Sealed + Sized + IntoAutoSafe {
+pub trait AutoSafe: Sealed + Sized {
 	/// When specified in consumer code (in the `impl` return type), use the bound variant here.
 	type BoundOrActual;
 
@@ -127,15 +127,17 @@ pub trait IntoAutoSafe {
 	/// Implemented as identity for types that are already [`AutoSafe`].
 	fn into_auto_safe(self) -> Self::AutoSafe;
 }
-
-#[allow(deprecated)]
-impl<S: ThreadSafety> IntoAutoSafe for __<'_, S> {
+impl<T> IntoAutoSafe for T
+where
+	T: AutoSafe,
+{
 	type AutoSafe = Self;
 
 	fn into_auto_safe(self) -> Self::AutoSafe {
 		self
 	}
 }
+
 impl<'a, S: ThreadSafety> IntoAutoSafe for Guard<'a, S> {
 	#[allow(deprecated)]
 	type AutoSafe = __<'a, S>;
@@ -145,16 +147,3 @@ impl<'a, S: ThreadSafety> IntoAutoSafe for Guard<'a, S> {
 		__::new(self)
 	}
 }
-
-/// Panics unconditionally. (Just here to satisfy constraints.)
-impl<'a, T> IntoAutoSafe for &'a mut T
-where
-	T: Send + Sync + AutoSafe,
-{
-	#[allow(deprecated)]
-	type AutoSafe = __<'a, ThreadBound>;
-
-	fn into_auto_safe(self) -> Self::AutoSafe {
-		panic!("Called `IntoAutoSafe::into_auto_safe` on a reference.")
-	}
-}