<https://pl.kotl.in/zXrGRcejU> seems like a weird ...

# announcements

[kevinmost]

https://pl.kotl.in/zXrGRcejU seems like a weird bug with nullable generics. Try running it, then remove reified from the function header and run again

[Ruckus]

How so? With reified, it fails as expected. Without reified, it show warnings for unchecked casts.

[kevinmost]

I guess I would still think that val f: String = functionThatReturnsNull() would fail at runtime. If that function were a Java function returning String!, there'd be a KotlinNullPointerException here.

[Ruckus]

Hm, good point. I wonder why a null check intrinsic isn't generated...

[kevinmost]

I guess that intrinsic isn't generally "needed" unless using platform types, or for functions visible to external Java?

[Casey Brooks]

You need <T : Any>. Just T is interpreted as “any type, including a null type”. And since nullability is not a property of the JVM, it does not fail at runtime unless the compiler knows it’s not a nullable generic type

[Ruckus]

@kevinmost Maybe, I guess I've never bothered to learn when intrinsics are generated. I just kind of assumed they'd magically always be there when needed.

[kevinmost]

I thought about this a little bit more, and it seems to me like, if you're calling the method foo<String> (so T is String, which is a non-nullable type, of course), when you do result as T in the method, since the Kotlin compiler knows that T is non-nullable, it should generate an intrinsic non-null check for result right before the cast.