Marking Uuid::uuid5() as pure: same input leads to same output, and no I/O under normal operational constraints

src/Uuid.php

@@ -538,6 +538,9 @@ class Uuid implements UuidInterface
      *
      * @return UuidInterface A UuidInterface instance that represents a
      *     version 5 UUID
+     *
+     * @psalm-pure note: changing the internal factory is an edge case not covered by purity invariants,
+     *             but under constant factory setups, this method operates in functionally pure manners
      */
     public static function uuid5($ns, string $name): UuidInterface
     {

tests/static-analysis/UuidIsImmutable.php

@@ -89,4 +89,13 @@ final class UuidIsImmutable
             Uuid::isValid('ff6f8cb0-c57d-11e1-9b21-0800200c9a66'),
         ];
     }
+
+    /** @psalm-pure */
+    public static function uuid5IsPure(): UuidInterface
+    {
+        return Uuid::uuid5(
+            Uuid::fromString('ff6f8cb0-c57d-11e1-9b21-0800200c9a66'),
+            'Look ma! I am a pure function!'
+        );
+    }
 }