[magurotuna]

Pass a page's URL pattern to useParams() to type its params.

const { id } = useParams('/users/:id'); // id: string
useParams('/users/:id').idd;            // Type error
useParams('/userz/:id');                // Type error: no such page

• Works in all four adapters. useParams() and useParams<T>() are unchanged, and no config flag is needed.
• Only page patterns are accepted, not HTTP routes.
• useParams(pattern) throws if the current page has no value for one of the pattern's params, instead of returning undefined typed as string.
• void/routes exports PagePathMap, PagePath and PageParams<P>. Both the generated .void/routes.d.ts and the package declare them.

[yangshun]

Note that this PR adds runtime checks to useParams, so it can now bring down a page (might not be a bad thing, but it's new behavior) if the param shapes don't match.

I'm not sure if we want to do runtime checks within useParams. No other frameworks except TanStack Start do runtime checks within useParams.

If we're ok with just typechecking, consider this instead:

useParams<'/posts/:id'>();

or use your newly-added PageParams util:

useParams<PageParams<'/posts/:id'>>();

Since PageParams<'/posts/:id'> returns an object, useParams doesn't even require any changes.

[cpojer]

I also prefer doing typechecking only and not failing during runtime for this.

[magurotuna]

That makes sense, thanks for the insight! I'll make this static-check only