Replacing deprecated <:< Manifest type witness in Scala 2.10

Question

Can someone point me at what I should be doing under scala 2.10 in place of this deprecated type witness on Manifest?

reflect.ClassManifest.singleType(foo) <:< barManifest

Honestly, my goal here is just to replace it with something that doesn't raise a deprecation warning. I'm happy to use the new reflection API.

Here's the code in question in context, if that's important:

https://github.com/azavea/geotrellis/blob/master/src/main/scala/geotrellis/feature/op/geometry/geometry.scala#L45

Answer 1

If you want a fairly literal translation from manifests to type tags, you'll need to get the appropriate mirror, use it to reflect your instance, and then use the <:< on Type. For example:

import scala.reflect.runtime.currentMirror
import scala.reflect.runtime.universe._

sealed trait X
case class Y(i: Int) extends X
case class Z(j: String) extends X

def filterX[A <: X: TypeTag](xs: List[X]) = xs.filter(
  x => currentMirror.reflect(x).symbol.toType <:< typeOf[A]
)

And now:

scala> filterX[Z](List(Y(1), Y(2), Z("test")))
res1: List[X] = List(Z(test))

scala> filterX[Y](List(Y(1), Y(2), Z("test")))
res2: List[X] = List(Y(1), Y(2))

There may be ways you could take advantage of the new Reflection API more fully in your application, but this should work and will take care of the deprecation warnings.