Open Radar

 
Summary:
NSComparisonResult is defined as (^NSComparator)(id obj1, id obj2), but it is within an NS_ASSUME_NONNULL_BEGIN block, so its parameters are autocompleted as non-null, but they should be nullable.

Steps to Reproduce:
1. Desire to write a sort descriptor with a custom comparator that does something special with nil values (sorts them to the end of an ascending sort, for example).
2. Type “[NSSortDescriptor sortDescriptor” and look at the autocomplete options.
3. Allow Xcode to autocomplete the method +sortDescriptorWithKey:ascending:comparator:, including the comparator block parameters.

Expected Results:
The comparator block interface completes as ^NSComparisonResult(id  _Nullable obj1, id  _Nullable obj2) {

Actual Results:
The comparator block interface completes as ^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {

Regression:
Prior to nullability annotations being available, this was not an issue, because obj1 and obj2 could implicitly be nil or not according to Objective-C conventions.

Notes:
The issue is not that the autocomplete is wrong. It’s that I think the default parameter annotations of _Nonnull are wrong, and that they should be _Nullable instead.