Svelte 5 Generic component with JSDoc

[falco467]

Describe the problem

Hi,
we are working i a strictly typed JS + JSDoc environment. It is great that we can write type-safe props with @type and have full type-checking everywhere. We can also use generic functions and types with JSDoc @template {...} T
But it seems that using a generic Svelte component generics="T extends" is only possible with TypeScript.

We have a generic table component and it would be great if we could automatic type-safety in our snippets for the columns if we define the component with a generic row type, which would then be inferred by the passed array-type.

If I declare Props dynamic with JSDoc @template T ... I will always get type-errors when using the component, since the component will be instantiated as the concrete type Comp<Prop<T>> and not as a generic Type for which types can be inferred.

The workaround which I found is to explicitly type cast the component to the correct concrete type:

import Select from './Select.svelte'
const SelectNumber = /** @type {import('svelte').Component<import('./Select.svelte').Props<number>,{},"value">} */ (Select)

This works, but is quite cumbersome, since I have to create this cast anytime I want to use the component without errors.

It would be great if Svelte could support type inference by use, like normal generic types and functions do.

Here is a Playground sample with the working work around:
https://svelte.dev/playground/48be5dc1b4c040a8a98f5af6fa1291aa?version=5.2.7

Describe the proposed solution

First Solution would be to extend the generics=""... attribute to also support JavaScript & JSDoc instead of only Typescript.

Second Solution would be to automatically generate Components with generic Props as a generic Function with the same Type parameters - so the type-system could automatically infer the used types.

Third Solution would be to provide a way to explicitly provide Type-Parameters to components like <MyComponent[string, number] or maybe <MyComponent @types={...} or similar

Importance

would make my life easier

[dummdidumm]

The most straightforward solution is to support generics for JSDoc components.

[falco467]

The most straightforward solution is to support generics for JSDoc components.

It shouldn't even be that hard to implement. Basically the compiler just has to create a Matching JSDoc comment in the output when compiling language type JS with a generics tag.