isInstanceOf looks if there is a corresponding entry in the inheritance chain. The chain of A with T includes A, B and T, so a.isInstanceOf[B] must be true. edit: Actually the generated byte code calls javas instanceof, so it would be a instanceof B in java. A little more complex call like a.isInstanceOf[A with T] … Read more
Because in Scala (as in any Turing complete language) there is no guarantee that a Function is total. val f = {x : Int => 1 / x} That function is not defined at 0. A PartialFunction is just a Function that promises to tell you where it’s not defined. Still, Scala makes it easy … Read more
You’re confusing impredicative types with existential types. Impredicative types allow you to put polymorphic values in a data structure, not arbitrary concrete ones. In other words [forall a. Num a => a] means that you have a list where each element works as any numeric type, so you can’t put e.g. Int and Double in … Read more
This might be related to what files you have open in the saved solution state. I ran into this problem in VS2010 and found that if I close the solution while an .xml file was open in the editor, then on the subsequent re-open of the solution, the project containing that .xml file would get … Read more