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import language.higherKinds
trait Foo[A <: AnyRef] {
type Repr
def f(a: A): Repr
def g(a: A): Option[Repr]
type M[X]
def m(a: A): M[a.type]
type Id[X] = X
def n(a: A): Id[(Repr, M[a.type])]
}
object Foo {
type Aux[A <: AnyRef, B] = Foo[A] { type Repr = B; type M[X] = Int }
}
object Main extends App {
def mapWithFoo[A <: AnyRef, B](as: List[A])(implicit foo: Foo.Aux[A, B]) = {
// Should be Eta expandable because the result type of `f` is not
// dependent on the value, it is just `B`.
as map foo.f
as map foo.g
as map foo.m
as map foo.n
}
}
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