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import language.higherKinds
object Test {
trait Monad[M[_]] {
def foo[A](ma: M[A])(f: M[A] => Any) = f(ma)
}
implicit def function1Covariant[T]: Monad[({type l[a] = (T => a)})#l] =
new Monad[({type l[a] = (T => a)})#l] {}
def main(args: Array[String]) {
// inference of T = (=> Any) here was outlawed by SI-7899 / 8ed7099
// but this pattern is used in Scalaz in just a few places and caused
// a regression.
//
// Inference of a by-name type doesn't *always* lead to a ClassCastException,
// it only gets there if a method in generic code accepts a parameter of
// that type.
//
// We need to introduce the stricter inference rules gradually, probably
// with a warning.
val m = implicitly[Monad[({type f[+x] = (=> Any) => x})#f]]
assert(m.foo[Int]((x => 0))(f => f(???)) == 0)
}
}
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