Issue Description:

The following code probably shouldn't create an error. But it does.

enum E {
    case begin
    case end
}
struct Z {
    var e: E
    static func create(_ e: E, f: (inout Z) -> ()) -> Z {
        return Z(e: e)
    }
}
let z: Z = .create(.begin) { $0.e = .end }

Playground execution failed: error: MyPlayground.playground:5:21: error: enum element 'begin' cannot be referenced as an instance member
let z: Z = .create(.begin) { $0.e = .end }
^

Tested with Xcode 8.3.2 both with the built-in toolchain as well as with the Swift 4.0 snapshot 2017-05-24. Fully qualifying the function name works as a workaround:

let z = Z.create(.begin) { $0.e = .end }