Unexpected optic generation where ambiguity is expected

[jppellet]

Given this context:

sealed trait T
case class A(s: String) extends T
case class B(s: String) extends T

this expression lens[T].s yields a Prism[T, String] that handles A values and ignores B. A GitHub discussion suggested the generation should have failed due to ambiguity instead.

Other idea: that this expression yields a Lens[T, String] that can handle both A and B values :-)

[joroKr21]

I think instead of ambiguity it would be better if this generates a Lens[T, String]

[milessabin]

I honestly think it would be better to retire shapeless lenses in favour of Monocle.

[joroKr21]

I honestly think it would be better to retire shapeless lenses in favour of Monocle.

Fair point although I'm not sure if Monocle offers the same convenience (e.g. Dynamic)