Associated type not defaultable to generic with `Self` as parameter

IDE: Visual Studio X/Fire
Version: (develop)
Target (If relevant): OSX
Within a protocol P, Self should implicitly conform to P, even for the purpose of instantiating a generic for a default for an associated type.

Expected Behavior:
Actual Behavior:
See below.

struct S<T: P> {}

protocol P {
  associatedtype A = S<Self> // E210 Generic parameter doesn't fulfill constraint "P<A>" for "T"

Thanks, logged as bugs://82794