A generics question, if this is the right channel....

# announcements

[Damien]

A generics question, if this is the right channel. I think I have a legitimate use of an out parameter, but the compiler is complaining.

Error: Type parameter T is declared as 'out' but occurs in 'in' position in type (T) -> C<T>

Generics_Variance.cpp

[ephemient]

assuming B : A,

val c = C<B>()
c.foo { value: A -> C<A>(value) }

should not be allowed, but would be if your function were accepted and val c: C<A> = C<B>() which is allowed by <out T>

[ephemient]

if you were to define it as a non-member function,

fun <T> C<T>.foo(f: (T) -> C<T>): C<T>

it would be accepted, as you can't cause any issues with that

[ephemient]

also

class C<out T>(val member: T) {
    fun foo(f: (value: T) -> C<@UnsafeVariance T>): C<T>
}

is accepted, but as the annotation name indicates…