Open Radar

 
Summary:
Given a generic class that takes a type T constrained to base class A. If T is set to a subclass B of A, creating an instance of T incorrectly creates an instance of A. The compiler thinks it has an instance of B. Chaos ensues.

Steps to Reproduce:

class A { init() {} }
class B : A { var prop = “prop” }

class G<T: A> {
    func t() -> T {
        return T() // incorrectly returns an instance of A even when T == B
    }
}

let g = G<B>()
let t = g.t()        // The compiler thinks it has an instance of B but it really has an instance of A
println t.prop    // Causes an error

Expected Results:
Prints “prop”

Actual Results:
BAD_ACCESS error