Accessing shadowed swift var in extension: what should work? -

i have bunch of protocols designed let me mock out uikit stuff testing, among which:

public protocol haspresentedvctype {     var presentedviewcontroller: haspresentedvctype? { } } 

i cannot give uiviewcontroller empty conformance protocol, because presentedviewcontroller of type uiviewcontroller?:

extension uiviewcontroller: haspresentedvctype {} // error:(32, 1) type 'uiviewcontroller' not conform protocol 'haspresentedvctype' // note:(18, 9) protocol requires property 'presentedviewcontroller' type 'haspresentedvctype?' 

the following extension attempt shadow uiviewcontroller's presentedviewcontroller var , let type inference choose whichever of 2 need:

extension uiviewcontroller: haspresentedvctype {     public var presentedviewcontroller: haspresentedvctype? {         let presented: uiviewcontroller? = self.presentedviewcontroller         return presented     } } 

this works if extension not in same target original protocol, fails if protocol , extension in same target:

// error:(33, 16) 'presentedviewcontroller' used within own type 

i can make work within same target introducing second protocol , putting implementation in constrained extension:

public protocol _haspresentedvctype {     var presentedviewcontroller: uiviewcontroller? { } } extension uiviewcontroller: haspresentedvctype, _haspresentedvctype {} extension haspresentedvctype self: _haspresentedvctype {     public var presentedviewcontroller: haspresentedvctype? {         let presented: uiviewcontroller? = self.presentedviewcontroller         return presented     } } 

so question: supposed work @ all, , if under circumstances?

(xcode 7.3, swift 2.2.)

and if (as rather suspect) it's not supposed work, there relatively tidy way similar effect?