Strange combination of unused $state and $derived causes missing rerender

[kuechlerm]

Describe the bug

I have a super strange bug in my project and I was able to reduce it down to the provided REPL.
If you click the buttons A and B multiple times, the content of the #if block does not get changed anymore.
If you remove one of the lines that I describe in comments, the bug is gone.
The most easy fix is - of course - not having any unused variables. But that was not easy to spot in a big refactoring and maybe this points to a underlying problem.

Update 1

This is not so edge-casy as I thought. I have the same issue even with no unused state variables in a more complex setup. Much harder to reproduce unfortunately. I will give it another try...

Update 2

The problem is definitely related to the filter function in the $derived prop.
This workaround works: REPL without $derived

Reproduction

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAE5VT0Y6bMBD8lS13UkAK0FbXFxIikf5C3y734MCScw9sZC_pXS3-vbYxyUWt1FZ58Swzu-PJ2kQt71BHxaOJBOsxKqJqGKJ1RG-DA_qMHaHFWo6qdpWtrhUfaHcQALwfpCIwQM9cnDRM0CrZwyrLv_lCNstXm4OwP8pzUNjLMzq-BiYae0A4jiew8CQFOlaHBKMYNTZQwr0mRhh_TGyLbX4ZbUHDz-5AXztev0Dlu-2BEXTINMEDEO9RO1VgXiUH2h5HIilAitrJSxMnUO7CNTJiRzt6Va0m2FXbfOb-j3LvlPt3yj-YMHe8vZGV88h5zIEqTyqw0xhq--DgQ5r-LUdI0-DX3CGrn5dBHbfRMA2csL9MMg5lQoaCyZ3CA5Pzdrpxr-mtQ9_altYQwjBLq1YKSjX_iQU8fBle3f9OvsGss3vUy4a3HJuoIDXitL6s3c3GXBfwu36_fHXHtIaZOk-dEw9rYvNLwq41jNj1w6MRsoBP0xr84fP05Hnk87CsBhU_YxO7PDP7IghVnCytFrxc89_W2Fpzzay_zQwV0qiE12TO3RKOS1rgq39JtRTWUHhNJQj8ES4bJ5vfw3uafgFrBsHYvwMAAA==

Logs

No response

System Info

REPL

Severity

annoyance

[trueadm]

This is likely because when you remove the $state, it becomes non-runes mode. In non-runes mode we don't use === equality on state and derived, but we do in runes mode. I'm going to take a hunch it has something to do with that, however, I can dig into it more tomorrow.