Fix missing generic parameters in member type

[sidepelican]

There was a problem where member types that held generic parameters would lose them.

• base code

func bar<T: Body>() -> Swift.Result<T, any Error>

• expected

    var barHandler: (() -> Any)?
    func bar<T: Body>() -> Swift.Result<T, any Error> {
        barCallCount += 1
        if let barHandler = barHandler {
            return barHandler() as! Swift.Result<T, any Error>
        }
        fatalError("barHandler returns can't have a default value thus its handler must be set")
    }

• actual

    var barHandler: (() -> Swift.Result)?
    func bar<T: Body>() -> Swift.Result {
        barCallCount += 1
        if let barHandler = barHandler {
            return barHandler()
        }
        fatalError("barHandler returns can't have a default value thus its handler must be set")
    }

Thanks to @slightair !

[uhooi]

LGTM!!