Do you imply variance can and should be checked right away? That would be just great (but may cause a lot of frustration among developers unless there's a proper error message).
2009/6/18 Vladimir Reshetnikov
<v.reshetnikov@...>
Hi,
Consider the following code:
////////////////////////////////////////
class A[-S](y : S) {
val f = new { val x = y }
}
////////////////////////////////////////
It compiles without any errors. But now we can write:
scala> val a = new A(1)
a: A[Int] = A@43e3ac
scala> val b = a : A[Nothing]
b: A[Nothing] = A@43e3ac
scala> b.f.x
java.lang.ClassCastException: java.lang.Integer cannot be cast to
scala.runtime.Nothing$
at .<init>(<console>:8)
at .<clinit>(<console>)
at RequestResult$.<init>(<console>:4)
at RequestResult$.<clinit>(<console>)
at RequestResult$result(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorIm...
Looks like unsoundness.
Thanks,
Vladimir
--
Thanks,
-Vlad
