Cannot use `self.` with parameter packs

[keith]

This code compiles:

class Store<State> {
    var currentState: State { fatalError() }
}

class CompositeStore<CompositeState, each State, OriginalState>: Store<CompositeState> {
    let store: (repeat Store<each State>)
    let combine: ((repeat (each State)) -> CompositeState)

    override var currentState: CompositeState {
        return self.combine(repeat (each store).currentState)
    }

    init(store1: (repeat Store<each State>),
         combine: @escaping (repeat (each State)) -> CompositeState)
    {
        self.store = store1
        self.combine = combine
   }
}

But if I use self.store instead:

        return self.combine(repeat (each self.store).currentState)

I get this diagnostic:

/tmp/foo.swift:10:42: error: expected ',' separator
        return self.combine(repeat (each self.store).currentState)
                                         ^
                                        ,
/tmp/foo.swift:10:37: error: cannot find 'each' in scope
        return self.combine(repeat (each self.store).currentState)
                                    ^~~~
/tmp/foo.swift:10:29: error: value pack expansion must contain at least one pack reference
        return self.combine(repeat (each self.store).currentState)
                            ^
/tmp/foo.swift:10:54: error: value of tuple type '(_, (repeat Store<each State>))' has no member 'currentState'
        return self.combine(repeat (each self.store).currentState)
                                   ~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~
error: fatalError

Steps to reproduce

xcrun --toolchain org.swift.59202306051a swiftc /tmp/foo.swift -Xfrontend -disable-availability-checking

Environment

• 6/5/23 main snapshot