Jon Pretty

Here's a Scala 3 feature suggestion: I'd like to write for-comprehensions which know their generator type, like so: for[List] { x <- xs y <- ys } yield ... It would make it much easier to work out whether `xs` or `ys` is the wrong type.

What happens now: val xs: Option[Int] = … val ys: List[Int] = … for { x <- xs y <- ys } yield x + y error: type mismatch; found : List[Int] required: Option[?] y <- ys The error's misleading because the real mistake is in x <- xs, and it's the wrong way round.