Merge bd626e9a95 into 85f4c3f095

This reverts commit 738cff69fe.

A user in the rust-lang forum noted that a BorrowedNPC in the Unborrowed
state could be exposed if a panic occurs.

src/game/npc/list.rs

@@ -36,50 +36,25 @@ pub enum BorrowedNPC<'a> {
         cell: &'a NPCCell,
         token: &'a mut NPCAccessToken,
     },
-    /// SAFETY: Constructing the `Unborrowed` variant is **inherently unsafe**.
-    /// Rust doesn't support marking enum variants as unsafe, but if it did, this
-    /// one would be.
-    /// 
-    /// A `BorrowedNPC` in the `Unborrowed` state must **never** be dereferenced.
-    /// Doing so will invoke `unreachable_unchecked`, leading to immediate Undefined
-    /// Behavior.
-    /// 
-    /// Never expose a `BorrowedNPC` in the `Unborrowed` state outside this module.
     Unborrowed,
 }
 
-impl BorrowedNPC<'_> {
-    unsafe fn new_unborrowed() -> Self {
-        Self::Unborrowed
-    }
-}
-
 impl Deref for BorrowedNPC<'_> {
     type Target = NPC;
 
-    #[inline]
     fn deref(&self) -> &Self::Target {
         match self {
             BorrowedNPC::Borrowed { ref_mut, .. } => &*ref_mut,
-            // `unreachable_unchecked` tells the compiler to assume this branch
+            _ => unreachable!()
-            // will never be reached, skipping any checks.
-            // Verified via Godbolt: This significantly improves codegen when
-            // accessing `BorrowedNPC` fields.
-            _ => unsafe { core::hint::unreachable_unchecked() }
         }
     }
 }
 
 impl DerefMut for BorrowedNPC<'_> {
-    #[inline]
     fn deref_mut(&mut self) -> &mut Self::Target {
         match self {
             BorrowedNPC::Borrowed { ref_mut, .. } => &mut *ref_mut,
-            // `unreachable_unchecked` tells the compiler to assume this branch
+            _ => unreachable!()
-            // will never be reached, skipping any checks.
-            // Verified via Godbolt: This significantly improves codegen when
-            // accessing `BorrowedNPC` fields.
-            _ => unsafe { core::hint::unreachable_unchecked() }
         }
     }
 }
@@ -91,10 +66,10 @@ impl TokenProvider for BorrowedNPC<'_> {
     {
         match self {
             BorrowedNPC::Borrowed { .. } => {
-                let old = std::mem::replace(self, unsafe { BorrowedNPC::new_unborrowed() });
+                let old = std::mem::replace(self, BorrowedNPC::Unborrowed);
                 let (old_ref_mut, token, cell) = match old {
                     BorrowedNPC::Borrowed { ref_mut, token, cell } => (ref_mut, token, cell),
-                    _ => unsafe { core::hint::unreachable_unchecked() }
+                    _ => unreachable!()
                 };
 
                 drop(old_ref_mut);
@@ -105,7 +80,7 @@ impl TokenProvider for BorrowedNPC<'_> {
 
                 result
             }
-            _ => unsafe { core::hint::unreachable_unchecked() }
+            _ => unreachable!()
         }
     }
 }