A modern programming language that makes developers happier.

kotlinlang

Is it possible to make sure a type parameter is not `Nothing` at compile time?

I don’t think you can, since `Nothing` denotes the ‘empty-set’ which is a sub-set of all other possible sets. This means that `Nothing` is assignable to every possible type.

It is ugly, but you could force a function or a class-constructor to take an input-parameter of type `T`. If `T` is provided a `Nothing`, you code won’t compile.

`fun &lt;T&gt; someFunction(dummy: T)` ,
then calling `someFunction&lt;Nothing&gt;(…)` will never work, whatever you put in the spot of `…`, because `dummy` cannot be provided a value, since `Nothing` has no values in its set.

`fun ƒ(x: Nothing?) { requireNonNull(x) }` hehehe

<@U9TRSCYSF> That wouldn't work, as people would most likely pass null in it anyway and I like people to know something is wrong at compile time.

You can’t pass in `null` to a `Nothing` value.

Ah… your comment was in answer to Richard’s answer… sorry..

You're basically saying that you never have any meaningful type other than null. Totally valid.

No, you can’t.
You can pass `null` to a `Nothing?` , not to a `Nothing`.

But that's what my signature uses. :wink:

I added _hehehe_ because there is the null loophole so it's not fully up to what you want.

Yup, but the original question was about the non-nullable `Nothing` :slightly_smiling_face:

However, nothing can ever be nothing because it is nothing.

Well, you basically know that nothing is ever nothing already without any check. :wink:

The place it would be used is on a operator`-=`. If I could just return the type I could at least mark the rest of the function as never executed. But `-=` has to return `Unit`

I don't fully understand but you can just return unit: `fun ƒ() = Unit`