Add test t11649

Author: liufengyun

tests/patmat/t11649.scala

@@ -0,0 +1,7 @@
+sealed trait Command { type Err }
+final case class Kick() extends Command { type Err = String }
+final case class Box() extends Command { type Err = Int }
+def handle[E](cmd: Command {type Err = E}): Either[E, Unit] = cmd match {
+  case Kick() => ???
+  case Box() => ???
+}