// very contrived code to demonstrate the issue

// this conditional type trips type inference
type Action<P> = P extends void
    ? { type: string }
    : { type: string, payload: P }

interface Dispatch {
    // this conditional type seems to have no negative impact on type inference
    <P>(action: Action<P>): P extends void ? undefined : P
}

declare const dispatch: Dispatch

const numberAction: Action<number> = {
        type: 'dummy',
        payload: 0,
    }
    // infered result type is {}, expected one is number
    , numberResult: number = dispatch(numberAction)

const voidAction: Action<void> = {
        type: 'dummy',
    }
    // seems infered P is {}, so it is not allowed to pass voidAction to dispatch
    , voidResult: undefined = dispatch(voidAction)