Why is `lateinit var` not allowed for inline classes that wrap types that otherwise can be `lateini...

# announcements

[sandjelkovic]

Why is lateinit var not allowed for inline classes that wrap types that otherwise can be lateinit-ed?
For example:

inline class Id(val value: String)

can’t be used as

private lateinit var id: Id

and is there a workaround that is not a nullable field or a data class?

[StavFX]

I can’t think of a reason this would not be allowed, maybe it’s a bug / future feature.
Anyway, you might want to use typealias instead for this purpose.
If your inline class has other properties/methods, you can replace them with extension methods.
So

inline class Foo(i: Int) {
  fun bar() = ...
}

Turns into

typealias Foo = Int
fun Foo.bar() = ...

[StavFX]

It’s not a perfect stand-in, but pretty close.
With the typealias solution, you’ll be able to call bar() on any Int, which wouldn’t be possible with inline class, but again, pretty close.

[sandjelkovic]

Thanks, but the typealias has one very significant drawback - comparing them or passing as method parameters would act the same as the aliased class and you won’t get typesafety.
For sample:

typealias Foo = Int
typealias Bar = Int

foo > bar
// passes, even though they are supposed to be 2 different types

Essentially, typealias doesn’t create a new type

[StavFX]

Yup, agreed. That’s what I meant by you'll be able to call bar() on any Int. If that’s a deal-breaker for you, you might have to settle on a nullable property, or wait till this is fixed 😛
It’s probably worth opening a youtrack ticket for.