It is an issue. Unlike Svelte or Vue, SolidJS is vanilla JS[X], syntax-wise, yet it’s compiled and uses a Babel plugin. Rescript compiles both regular code and JSX by itself, so instead of Babel plugin ideally it would need a ppx, which of course the framework authors won’t provide, so it would have to come from the ReScript community. (The types are going to have to come from the community too.)
There was also talks about letting Rescript emit JSX as is (meaning it could be further transformed by Babel), and there’s work on generic JSX transform. Not sure if the latter is enough to let Solid compiler track reactive context etc.