Swift: Provide transparent bridging for types with NSValue extensions

Originator:zwaldowski
Number:rdar://20807093 Date Originated:04-May-2015 05:43 PM
Status:Open Resolved:false
Product:Developer Tools Product Version:Xcode 6.3.1 (6D1002)
Classification:Enhancement Reproducible:Sometimes
 
Summary:
The Apple frameworks define a number of boxing and unboxing extensions on `NSValue`. The types in question (such as `CGRect`, `CMTime`, etc.) should, in the near-term, conform to `_ObjectiveCBridgeable` and be unconditionally convertible to and conditionally convertible from an `NSArray` of an appropriate `nSValue`.

Steps to Reproduce:
1. Attempt to use `AVAssetImageGenerator.generateCGImagesAsynchronouslyForTimes(_:completionHandler:)` with a `Swift.Array` of `CMTime`, or any such Objective-C method that expects an `NSArray` of an `NSValue` of a certain kind.

Expected Results:
The method accepts an array literal of `CMTime` instances.

Actual Results:
A compiler error is raised; one must manually map to `NSValue`.

Version:
Mac OS 10.10.4 (14E11f), Xcode 6.3.1 (6D1002), Swift 1.2 (swiftlang-602.0.49.6)

Notes:
An ideal longer-term solution might involve hiding the Objective-C version of the method(s) and introducing versions in an overlay library that accept instances of `SequenceType` or `CollectionType`.

More conformances to `_ObjectiveCBridgeable` might have negative implications on performance or mask the meaning of `NSValue` to new Cocoa-on-Swift developers.

Configuration:
Occurs when boxing complex structs.

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