Comment by PartiallyTyped

> I mean, what if the expectation from the data that an value is a prime number? -- How are they going to encode this in their type systems? And this is just a trivial example.

In TypeScript we can define

    type Prime = number

    function isPrime(value: number) value is Prime {
        // run sieve
    }

From here, you may have e.g.

    function foo(value: Prime, ...) {

    }

And it will be typed checked.

    function fooOrFail(v: number) {
        if (isPrime(v))
            foo(v)
        else 
            throw new TypeError()
    }