EDIT – apologies, I only just noticed your first error. There is no way of instantiating a T at runtime because the type information is lost when your program is compiled (via type erasure) You will have to pass in some factory to achieve the construction: class BalanceActor[T <: Actor](val fac: () => T) extends … Read more
To add to my previous answer on Abstract type vs. parameters, you have also the JESSE EICHAR’s recent blog post (2010, May 3rd) highlighting some key differences: trait C1[A] { def get : A def doit(a:A):A } trait C2 { type A def get : A def doit(a:A):A } In C2 case, the parameter is … Read more
The problem is that a single type could implement Bar<P> for multiple values of P. If you had a struct Baz that implemented Bar<i32> and Bar<String>, which type should Foo::new use for P? The only solution is to ensure that a single type cannot implement Bar more than once (if that’s not what you want, … Read more
If getClass() returns Class<? extends X>, nothing really bad can happen; actually it’ll help a lot of use cases. The only problem is, it is not theoretically correct. if an object is an ArrayList<String>, its class cannot be Class<ArrayList<String>> – there is no such class, there is only a Class<ArrayList>. This is actually not related … Read more
No. Given a parametrized Token type as: type Token[T any] struct { TokenType string Literal T } each instantiation with a different type argument produces a different (named) type. In other words, Token[string] is not assignable to Token[int]. Nor is it assignable to Token[any] as any here is used as a static type to instantiate … Read more
They expose different interfaces and contract for the method. The first declaration should return a collection whose elements type is the same of the argument class. The compiler infers the type of N (if not specified). So the following two statements are valid when using the first declaration: Collection<Integer> c1 = getThatCollection(Integer.class); Collection<Double> c2 = … Read more