Comment by jillesvangurp

Kotlin's smart cast is nice in this context.

One example is with nullable types. if you have val foo: Whatever? // might be null and Whatever and Whatever? are two separate types. foo.someMethod()// compilation error because foo is not of type Whatever

if(foo != null) { foo.someMethod() // works because foo was smart cast to Whatever after the null check }

In the same way doing a switch on a type smart casts the variable to that type. Smart casting of nullable types also gets rid of a lot of clumsy things like Optional, Maybe, etc. you'd need in other languages where you'd have to call a method to extract the value, assign it to a new variable, etc.