How to cast Any to Array[T] maintaining Scala's invariance for arrays -

i tried implement following function maintaining scala's invariant view on jvm arrays:

def cast[t](a: any): option[array[t]] = ??? 

that is, given:

class foo class bar extends foo 

i want following examples return some:

val arr1: = array(new bar) cast[bar](arr1) // ok  val arr2: = array(1, 2, 3) cast[int](arr2) // ok  val arr3: = array("a", "b", "c") cast[string](arr3) // ok 

for following one, instead, want return none:

val arr: = array(new bar) cast[foo](arr1) // want none  val arr2: = array(list(new bar)) cast[list[foo]](arr2) // must none too! 

i tried through reflection using classtag/typetag no luck, since i'm no reflection expert missing something.

p.s.: know having any there, bad practice but, please, try see question academically. know, find out if there's way , how to.

update: solution provided below still not work array(list(new bar)) because of type erasure.

i think after:

import scala.reflect.classtag  def cast[t](a: any)(implicit ct: classtag[array[t]]): option[array[t]] = ct.unapply(a) 

in repl:

scala> val x: = array(1, 2, 3) x: = array(1, 2, 3)  scala> val y = cast[int](x) y: option[array[int]] = some([i@7a8f55c)  scala> val z = cast[string](x) z: option[array[string]] = none 

the solution above doesn't keep invariance; best way found far this:

def cast[t](in: any)(implicit ct: classtag[array[t]]): option[array[t]] =    if (ct.runtimeclass == in.getclass) ct.unapply(in) else none 

not sure how nice works:

scala> :paste // entering paste mode (ctrl-d finish)  class foo class bar extends foo  val x: = array(new bar)  val y = cast[foo](x) val z = cast[bar](x)  // exiting paste mode, interpreting.  defined class foo defined class bar x: = array(bar@6109a8cc) y: option[array[foo]] = none z: option[array[bar]] = some([lbar;@7ccebaae)