I have an F-bounded type Sys
:
trait Sys[S <: Sys[S]]
And some trait which take it as type parameter:
trait Foo[S <: Sys[S]]
Suppose I have a method to be invoked with a Foo
:
def invoke[S <: Sys[S]](foo: Foo[S]) = ()
Suppose I have a model update type, and a sub-type which carries a Foo
:
sealed trait Update
case class Opened[S <: Sys[S]](foo: Foo[S]) extends Update
A helper function to register a model observer:
def observe(pf: PartialFunction[Update, Unit]) = ()
Now the following fails:
observe {
case Opened(foo) => invoke(foo)
}
with
<console>:16: error: inferred type arguments [Any] do not conform to method invoke's
type parameter bounds [S <: Sys[S]]
case Opened(foo) => invoke(foo)
^
How can I fix the partial function, if Sys
, Foo
, invoke
, Update
, Opened
and observe
are given. It is allowed to add a value or type member to Foo
.
A possible solution is casting:
Obviously this is horrible and not the preferred solution, so I am waiting for other answers.