Inlined match statements should not fail on unreachable cases

[letalvoj]

Minimized code

inline def aToB[T,A,B](t:T,b:B): T|B = t match {
  case _:A => b
  case _:T => t
}

@main def main() = aToB[Int, Double, String](1,"x")

Output

❌ this case is unreachable since type Int is not a subclass of class Double

Expectation

A warning? User of the inlined method would be hardly able to do anything about it if it came from a library.

Moreover, is a dead branch of match statement really worth a compile error? Non-exhaustive matches, which seem more serious to me, are just warnings now.

[letalvoj]

I've just encountered it again. I want to check wheteher V is of SSHMsg and this feature prevents me from doing that.

    inline given productWriter[V:ClassTag](using m: Mirror.ProductOf[V]) as SSHWriter[V] = (ls:V, os:OutputStream) => {
        ls match {
            case msg:SSHMsg[_] => os.write(msg.magic)
            case _ =>
        }
        writeProduct[m.MirroredElemTypes](ls.asInstanceOf)(os)(0)
    }

Rewriting using if-statement as a workaround

        if (ls.isInstanceOf[SSHMsg[_]])
            os.write(ls.asInstanceOf[SSHMsg[_]].magic)