A modern programming language that makes developers happier.

kotlinlang

if you want the resulting type to be `Map&lt;String, List&lt;String&gt;&gt;` you’re probably going to have to do some casting

smart casting fails for the `is String` case - the compiler says
```
Smart cast to 'String' is impossible, because 'it.value' is a property that has open or custom getter
```

it works if you use `{ (key, value) -&gt; `

ah, interesting that it doesn’t complain when you destructure, but ¯\_(ツ)_/¯

it makes sense, you are creating immutable copies, essentially `val key =` etc, so they can no longer change.