Yes that would be problematic too. For these cases, solidjs provides the createMemo function that can be used to create a derived signal that keeps reactivity.
You can theoretically do hat in ReScript too. The difference is that in ReScript, the problem is much less obvious, since the source code looks completely normal, and you wouldn’t get an error. The component would simply never update. So it’s much harder to spot the problem. But once you understand it, there are multiple solutions available that all work well in ReScript.