To quote the Kotlin reference on Generics: > Fo...

# getting-started

[okkero]

To quote the Kotlin reference on Generics:

For Foo<in T>, where T is a contravariant type parameter, Foo<*> is equivalent to Foo<in Nothing>. It means there is nothing you can write to Foo<*> in a safe way when T is unknown.

And Function1 defines its type parameters as <in T, out R>