Improper Locking (ARCH9039)

Key swift.async.improper-locking · Severity warning · Category async

Flags NSLock / os_unfair_lock use where lock() has no matching unlock() on every path (no defer), and objc_sync_enter(self).

Incorrect

lock.lock()
guard ok else { return }
lock.unlock()

Correct

lock.lock(); defer { lock.unlock() }

Fix

Pair lock() with defer { unlock() }, or use withLock { }.