[swift-evolution] [Pitch] Importing Objective-C 'id' as Swift 'Any'

[Joe Groff]

Hi everyone. After implementing SE-0072, disabling the implicit bridging conversions from Swift value types to classes (https://github.com/apple/swift-evolution/blob/master/proposals/0072-eliminate-implicit-bridging-conversions.md), we immediately observed a severe negative impact on Cocoa interop as our users at Apple adapted to the change, forcing us to roll it back. `id`-based interfaces are still all over the place in the Cocoa SDKs, but it's our goal that Swift programmers should be able to use the value type versions of things without being constantly confronted with marshalling in and out of their `NS` versions, and this change failed that test for Cocoa users. Furthermore, the Foundation corelibs team is interested in continuing to adopt more value types and improving the experience of using Foundation from Swift without being hamstrung by the limitations of ObjC interop. We can address the problem of value-type-to-id interfacing in a different way—instead of making it a special case in the type system, we can handle it in the Objective-C bridge instead, by bridging Objective-C's `id` type to `Any` instead of `AnyObject`. This is a big change, but I think it leads to an overall Swiftier and more flexible model. I'm working on a proposal to this effect and would like to start getting feedback on it. Thanks for taking a look!

https://github.com/jckarter/swift-evolution/blob/1316004246e45296f81582477d70c22f95ec106c/proposals/XXXX-id-as-any.md

-Joe