#Swift Bug or feature:

EDIT: This is what `ReferenceWritableKeyPath` is for. Thanks, @calicoding!

struct GenericWrapper<Item: AnyObject, Value> {
let property: WritableKeyPath<Item, Value>
let object: Item

func commit(newValue: Value) {
object[keyPath: property] = newValue // error: `let` mimimi
var stfu = object
stfu[keyPath: property] = newValue // properly works because `Item` is a reference type after all, and the compiler knows, but pretends not to?!
}