Unable to get clone method in generic type to compile

clone_generic.pony

actor Main
  new create(env: Env) => None


trait MyTrait
  new create()
  fun test(): MyTrait


class Foo is MyTrait
  new create() => None
  fun test(): Foo => Foo


class GenericTest[T: MyTrait ref]
  var value: Array[T] = Array[T]

  new create() => None

  fun test() =>
    let a = Array[T]
    a.push(T.test())

actor Main
  new create(env: Env) =>
    let f = FooTest


trait MyTrait[T]
  new create()
  fun test(): MyTrait[T]


class Foo
  new create() => None
  fun test(): Foo => Foo


class FooTest
  fun test() =>
    let a = Array[Foo]
    a.push(Foo.create().test())

actor Main
  new create(env: Env) =>
    let f = GenericTest[Foo] // A `Foo` version of `GenericTest`


trait MyTrait[T]
  new create()
  fun test(): T


class Foo is MyTrait[Foo]
  new create() => None
  fun test(): Foo => Foo


class GenericTest[T: MyTrait[T] ref]
  fun test() =>
    let a = Array[T]
    a.push(T.create().test())