Tony Morris

Fun Scala typechecker fail: scala> def foo[A](xs: List[A]) = for { (a,b) <- xs } yield a foo: [A](xs: List[A])List[Any]

@pchiusano It's a fail in d same way dis is: scala> def foo[A](xs: List[A]) = xs.map { case (x: Int) => x } foo: [A](xs: List[A])List[Int]

@missingfaktor Yes. Even w/ subtyping, no reason for typechecker to allow a pattern of type Int, when Int not known to be subtype of A

@pchiusano (A <: Any >: Nothing), unless you specify otherwise. It could very well be Int at runtime.

@pchiusano Add a constraint that guarantees Int won't be there, and you get a compiler error - https://gist.github.com/missingfaktor/0fdcd0052eb2267b9300 ….

@missingfaktor a) that does not scale, esp when writing polymorphic code, and b) default is still opposite of what I want