A couple of minor improvements to AsyncContextFrame::StorageKey

* Reset the tracing storage key in IoContext when the context is
  destroyed.
* Do not store a key if the key has already been reset
* Compare pointers and not hash in operator=

src/workerd/jsg/async-context.c++

@@ -34,6 +34,10 @@ AsyncContextFrame::AsyncContextFrame(Lock& js, StorageEntry storageEntry)
     }
   }
 
+  // This case is extremely unlikely to happen but let's handle it anyway
+  // just out of an excess of caution.
+  if (storageEntry.key->isDead()) return;
+
   storage.upsert(kj::mv(storageEntry), [](StorageEntry& existing, StorageEntry&& row) mutable {
     existing.value = kj::mv(row.value);
   });

src/workerd/jsg/async-context.h

@@ -66,10 +66,11 @@ class AsyncContextFrame final: public Wrappable {
     // An opaque key that identifies an async-local storage cell within the frame.
   public:
     StorageKey() : hash(kj::hashCode(this)) {}
+    KJ_DISALLOW_COPY_AND_MOVE(StorageKey);
 
     void reset() { dead = true; }
     // The owner of the key should reset it when it goes away.
-    // The StorageKey is typically owned by an instance of AsyncLocalstorage (see
+    // The StorageKey is typically owned by an instance of AsyncLocalStorage (see
     // the api/node/async-hooks.h). When the ALS instance is garbage collected, it
     // must call reset to signal that this StorageKey is "dead" and can never be
     // looked up again. Subsequent accesses to a frame will remove dead keys from
@@ -83,7 +84,7 @@ class AsyncContextFrame final: public Wrappable {
     bool isDead() const { return dead; }
     inline uint hashCode() const { return hash; }
     inline bool operator==(const StorageKey& other) const {
-      return hash == other.hash;
+      return this == &other;
     }
 
   private:
@@ -181,7 +182,7 @@ class AsyncContextFrame final: public Wrappable {
     }
 
     bool matches(const StorageEntry& entry, StorageKey& key) const {
-      return entry.key->hashCode() == key.hashCode();
+      return entry.key.get() == &key;
     }
 
     uint hashCode(StorageKey& key) const {