I'm afraid Svelte with typescript will loose some of its charm. Typescript is a little more verbose and explicit, also it cannot be directly executed by the browser (so you need to compile it, yet it is intermingled with HTML at times — there's JSX for that but Svelte kinda wants to NOT go the JSX/ShadowDOM route)
Internally Svelte uses TS though, the author claims to love TS also! It just does not mix very well with Svelte.
Stencil.js and lit-element are better picks in this regard IIRC.
Pretty much as you can see. A lot of people want it. It's not done yet.
Obviously Svelte is a JS to JS transformative compiler - you need to make a TS to JS transformative compiler.
I'm hacking on my next app using TypeScript on the backend (particularly around the data layer) and JS/Svelte on the frontend. I would like TS on Svelte, but the rest of Svelte is compelling enough I'd still use it over older tech like React.
Internally Svelte uses TS though, the author claims to love TS also! It just does not mix very well with Svelte.
Stencil.js and lit-element are better picks in this regard IIRC.