Open Radar

 
Summary:

Frameworks often expose methods that will verifiably never return nil. As some system frameworks do, it should be possible to annotate Objective-C methods and properties to indicate this, such that Swift will import them as regular types, not optionals.

As a great extra benefit, this could mean that (once a good portion of people’s frameworks are annotated), non-annotated methods/properties could be imported as regular optionals, not assumed variables (which decreases safety, as per rdar://18119727).

Steps to Reproduce:

1. Observe that some system Objective-C frameworks expose non-optional methods to Swift.
2. Attempt to use __attribute__((returns_nonnull)) to do the same.
2. Look in the headers and the Clang web pages to see how they do it, since that didn’t work.

Expected Results:

Expect to see some simple attribute or macro used to annotation the method.

Actual Results:

Observe that magical pixie dust is used to achieve the desired outcome.

Notes:

Magical pixie dust does not seem to be available on developer.apple.com