[SR-15010] Settings Nil as Dictionary Value Produces Inconsistent Behavior

[swift-ci]

Previous ID	SR-15010
Radar	None
Original Reporter	VaslD (JIRA User)
Type	Bug
Status	Closed
Resolution	Duplicate

Attachment: Download

Environment

Xcode Version 12.5.1 (12E507)

macOS Version 11.5.1 (20G80)

Empty iOS Playground

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Bug
Assignee	None
Priority	Medium

md5: bf30fdd90bad10c8d136fc94ab01c86d

duplicates:

• SR-3286 Dictionary element not removed in case of the value nil assignment

Issue Description:

According to Documentation:

If you assign nil as the value for the given key, the dictionary removes that key and its associated value.

In the following example, the key-value pair for the key "Aquamarine" is removed from the dictionary by assigning nil to the key-based subscript.

This works pretty well as long as I follow the example by using a nil literal to remove key-values, or by using a non-Optional Dictionary. If I have an Optional-valued Dictionary and use any other forms of nil, the removal is not guaranteed. It is confusing even, especially the short-hand case (.none) and fully-qualified case (X?.none) produce different results.

See the attached image for code sample.

P.S.: Also it may be debatable whether the nil-removal syntax should apply to Optional-valued Dictionaries at all. Because the point of using a Optional-valued Dictionary is to store Optionals. And an empty collection (no keys) vs. a collection of nils (keys present) are not the same thing.

[swift-ci]

Comment by Yi Ding (JIRA)

Found answered issue after tweaking my search, duh...