[SR-4464] Assigning a property to itself fails in 3.1

[iby]

Previous ID	SR-4464
Radar	None
Original Reporter	@iby
Type	Bug
Status	In Progress
Resolution

Attachment: Download

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 3.1Regression, DiagnosticsQoI, StarterBug
Assignee	None
Priority	Medium

md5: 702671bd69d19bebf1a102eb3ec92355

Issue Description:

Prior 3.1 we could assign property to itself if needed with self.name = (self.name), now it fails. Also, see this for details – http://stackoverflow.com/a/31931318/458356.

Just discovered by luck, apparently the supported syntax now is (self.name = self.name), is this official?

[belkadan]

I think the original syntax is probably still what we'd want to support in the rare cases where you actually want to do this.

[belkadan]

The fix would be to change TypeChecker::diagnoseSelfAssignment to ignore cases where the source of the assignment (the right-hand side) is a ParenExpr.

[swift-ci]

Comment by Adam Newton (JIRA)

I no longer have enough spare time to dedicate to this, so I'm going to unassign it. I have work-in-progress PR here with great feedback from the swift team which should help someone else get started. #10390

[swift-ci]

Comment by Jessy Catterwaul (JIRA)

Swift 5.3: Only parentheses solve this for instances. But for static properties, a `Self.` on either side of the assignment operator works. See the attached package.

Capturing [self] also subverts the error. I didn't demonstrate that in the package.