Fix TypedKey equals/hashCode symmetry with Key

paper-api/src/main/java/io/papermc/paper/registry/TypedKeyImpl.java

@@ -7,6 +7,27 @@
 @NullMarked
 record TypedKeyImpl<T>(Key key, RegistryKey<T> registryKey) implements TypedKey<T> {
     // Wrap key methods to make this easier to use
+    @Override
+    public boolean equals(final Object other) {
+        if (this == other) {
+            return true;
+        }
+        if (other instanceof final TypedKey<?> otherTyped) {
+            return this.key.equals(otherTyped.key()) && this.registryKey.equals(otherTyped.registryKey());
+        }
+        // A TypedKey is a Key, so it must compare equal to a plain Key with the same
+        // namespace and value (adventure's Key equality) to keep equals symmetric.
+        return other instanceof final Key otherKey
+            && this.key.namespace().equals(otherKey.namespace())
+            && this.key.value().equals(otherKey.value());
+    }
+
+    @Override
+    public int hashCode() {
+        // Match KeyImpl#hashCode so a TypedKey and an equal plain Key share a hash code.
+        return this.key.hashCode();
+    }
+
     @KeyPattern.Namespace
     @Override
     public String namespace() {

paper-api/src/test/java/io/papermc/paper/registry/TypedKeyEqualityTest.java

@@ -0,0 +1,36 @@
+package io.papermc.paper.registry;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import net.kyori.adventure.key.Key;
+import org.bukkit.inventory.ItemType;
+import org.junit.jupiter.api.Test;
+
+class TypedKeyEqualityTest {
+
+    @Test
+    void typedKeyIsSymmetricWithPlainKey() {
+        final Key key = Key.key("minecraft:stone");
+        final TypedKey<ItemType> typedKey = TypedKey.create(RegistryKey.ITEM, key);
+
+        // equals must be symmetric across the Key hierarchy
+        assertTrue(key.equals(typedKey), "plain Key should equal an equal TypedKey");
+        assertTrue(typedKey.equals(key), "TypedKey should equal an equal plain Key");
+        assertEquals(key.equals(typedKey), typedKey.equals(key), "equals must be symmetric");
+
+        // equal keys must share a hash code
+        assertEquals(key.hashCode(), typedKey.hashCode());
+    }
+
+    @Test
+    void typedKeysDifferByRegistry() {
+        final Key key = Key.key("minecraft:stone");
+        final TypedKey<ItemType> itemKey = TypedKey.create(RegistryKey.ITEM, key);
+        final TypedKey<?> blockKey = TypedKey.create(RegistryKey.BLOCK, key);
+
+        // same underlying key but different registries are not equal
+        assertNotEquals(itemKey, blockKey);
+    }
+}