Tightening the generic requirements or changing the as cast did not work around the crasher. Replacing the cast with a call to `_bridgeToObjectiveC() ` did.

Usual disclaimer: pretty much anything you do with an underscored type or function is subject to change, and crashes aren't out of the question if it turns out there's some secret limitation on how it's supposed to be used.

@swift-ci create

Any reason you can't remove the 'T: _ObjectiveCBridgeable' constraint? Everything bridges to AnyObject already.

In all three contexts where this crash is occurring, it's needed for disambiguation. One is a set of tiebreakers for string interpolation and the other two are bridging helpers for NSCoding (extension RawRepresentable a la _SwiftNewtypeWrapper and some helpers on NSCoding itself, Obviously to be replaced with Codable as soon as we get the chance…)

Re: underscored stuff, we as a team have accepted the boneheaded risks as a tradeoff to gain bug fixes from type safety (U+1F643).