interface Options<TParams, TDone, TMapped> {
    fetch: (params: TParams, foo: number) => TDone,
    map: (data: TDone) => TMapped
}

function example<TParams, TDone, TMapped>(options: Options<TParams, TDone, TMapped>) {
    return (params: TParams) => {
        const data = options.fetch(params, 123)
        return options.map(data)
    }
}

interface Params {
    one: number
    two: string
}

example({
    // WORKS
    fetch: (params: Params) => 123,
    map: (number) => String(number)
})

example({
    // WORKS
    fetch: (params: Params, foo: number) => 123,
    map: (number) => String(number)
})

example({
    // INFERS "unknown"
    fetch: (params: Params, foo) => 123,
    map: (number) => String(number)
})