Svelte component .d.ts not generated in this use case

[bledeabogdan]

There is a strange situation that I really do not understand regarding some type definition involving the following use case. I've created a SB and a GitHub repository for it, maybe someone could help me understand why.

There is an utility method which return a possible prop for the component which is basically a svelte writable store. The template T passed to the writable it's being generated when using type, but it's not generating the .d.ts file at all or generating that specific prop with any as type when using interface.

Anybody got any idea why that might be happening?

SB: https://stackblitz.com/edit/node-syvwi8
GitHub Repo (i've also included the dist folder): https://github.com/bledeabogdan/svelte-ts-writable-type-interface