Swift 5.1.5 and 5.2 break observation of properties of type Any?

[lilyball]

In Swift 5.1.5, the logic we use to detect whether the property is of type Any? breaks when using a recent deployment target. This wasn't detected because it produces the correct results with a deployment target of 10.9 (which the development xcodeproj has).

In Swift 5.2, this logic broke for all deployment targets, and additionally it gained an incorrect compiler warning.

Oddly enough, both compiler versions work correctly under optimization, it's just debug where it's broken.

Upstream bug filed as SR-12486.