@simpadjo Great idea! One comment on how to do it without the new class, then good to merge!

I'm inclined to think with the version specific files this is more complexity and maintenance burden at this point. What if we just do something like?

@implicitNotFound("Pattern guards are only supported when the error type is a supertype of NoSuchElementException. However, your effect has ${E} for the error type.")
sealed trait CanFilter[+E] {
  def apply(t: NoSuchElementException): E
}

object CanFilter {
  implicit def canFilter[E >: NoSuchElementException]: CanFilter[E] =
    new CanFilter[E] {
      def apply(t: NoSuchElementException): E = t
    }
}

@adamgfraser @jdegoes Let's agree on something or flip a coin )

@simpadjo I'm on board with @adamgfraser's suggestion! 🍀

Applied suggestions by @adamgfraser . Looks much cleaner now!
Also lots of confusion comes from using type annotations and tuple deconstruction.
Would be great to warn about it specifically, but don't know how to formulate it shortly and w/o dissing the compiler too much.
Js build is failing due to unrelated problems on master.

@adamgfraser I rebased it. Let's merge it then?