[SR-7300] nil converted to NSNull when returned from a nonnull Objective-C method

[swift-ci]

Previous ID	SR-7300
Radar	None
Original Reporter	benpious (JIRA User)
Type	Bug

Attachment: Download

Environment

Xcode Version 9.2 (9C40b).

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug
Assignee	None
Priority	Medium

md5: 76a08820f5a43a2ab494244c11a754e2

relates to:

• SR-8622 Nonnull Objective-C property that falsely returns nil causes inconsistent Swift behavior

Issue Description:

If Swift code receives nil from a function declared in Objective-C which is marked as returning nonull, and the return value of that function is passed into an Objective-C function, that function will receive an instance of NSNull instead of nil, regardless of whether that function's parameter is annotated nonnull or nullable. In other words:

{{ let liar = Liar() // Implemented in Objective-C}}
{{ let obj = liar.totallyNotNull() // returns nil}}
{{ liar.takeNonNull(obj) // receives NSNull}}
{{ liar.takeNull(obj) // receives NSNull}}

[belkadan]

I'm not sure we have any better options. @jckarter, any additional thoughts?