On point 1, this issue is the one to watch. https://github.com/sveltejs/svelte/issues/4518 Language server support will work for both JavaScript and TypeScript and error/type checking and editor support should be pretty comprehensive when it's ready. Svelte 3 was written with TypeScript in mind, so the idioms are fairly compatible with type checking. (a nice pit of success for design!)
This should also fix reassigning to a const mentioned in point 2.
On point 1, this issue is the one to watch. https://github.com/sveltejs/svelte/issues/4518 Language server support will work for both JavaScript and TypeScript and error/type checking and editor support should be pretty comprehensive when it's ready. Svelte 3 was written with TypeScript in mind, so the idioms are fairly compatible with type checking. (a nice pit of success for design!)
This should also fix reassigning to a const mentioned in point 2.