📝 Track optional discriminants under the union-property task

backlog.tasks

@@ -63,6 +63,7 @@ Matcher:
 ☐ when using a union type as a property, the current behavior of tagged union matcher is
     to pass never to handler parameters
     → new matcher function needed or can be fixed in tagged union matcher
+    ☐ optional discriminant (`{ type?: "x" }`) is the same hole: the boolean/nullish change now admits the `undefined` tag, so the factory accepts the key, but `Extract<T, Record<K, V>>` still passes `never` to both the `x` and `undefined` handlers
 
 Bugs:
 ✔ TS 7 LSP server logs `context canceled` on stderr at shutdown @done