Typesafety when defining handlers outside of router?

[luap2703]

The question seems to be too simple but how do we get the full type of the route resolver (the function inside the query, mutation, etc.) type OUTSIDE of the router? How do we infer it?

Let's say:

 export const supplyChainRouter = router({
    createSupplyChainLayouts: publicProcedure
        .input(...)
        .mutation(createSupplyChainLayouts),
})

and then use it like

    const createSupplyChainLayouts: CreateHandlerType <--- HOW?
    = ({input, ctx}) => {
        const user = ctx.user
...
    };

How do I get the exact type that is required to fulfill the routers/procedures need?

I had a hard time finding anything in the docs or issues/discussions but seems to be so obvious...