> On Mar 15, 2016, at 5:01 PM, Brent Royal-Gordon <br...@architechies.com>
> wrote:
>
> extension Foo {
> static var readableProperties: [String: (inout Foo) -> inout
> Any] = [
> "readWriteProperty": { $0.readWriteProperty },
> "readWriteNonmutatingProperty": { ... },
> "readOnlyProperty": { ... },
> "readOnlyMutatingProperty": { ... }
> ]
> static var writableProperties: [String: (inout Foo) -> inout
> Any] = [
> "readWriteProperty": {
> get { return $0.readWriteProperty }
> set { $0.readWriteProperty = newValue as! Int }
> },
> "readWriteNonmutatingProperty": { ... }
> ]
> }
A mutable return has to be invariant. It'd be more sound to model that as
"exists T. (inout Foo) -> inout T", if our type system becomes powerful enough
to represent that, than to erase the return type, since you could then
conceivably still recover the T by opening the existential.
-Joe
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