[SR-15176] Fixit for `override func` that should be `override var`

[CodaFi]

Previous ID	SR-15176
Radar	rdar://28337871
Original Reporter	@CodaFi
Type	Improvement

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Improvement, DiagnosticsQoI, StarterBug
Assignee	jiaren wang (JIRA)
Priority	Medium

md5: b17661d61829d04b65f822d78b07388a

Issue Description:

Consider

class C {
  var canBecomeFirstResponder: Bool

  init() {}
}

class D: C {
    override func canBecomeFirstResponder() -> Bool {
    }
}

We should add a special case to diagnoseGeneralOverrideFailure that tries to see if it can correct no-args FuncDecls to VarDecls and vice-versa.

[swift-ci]

Comment by jiaren wang (JIRA)

I would like give a shot on this. Could I get some hint?

[LucianoPAlmeida]

If I understand it correctly, the idea it here https://github.com/apple/swift/blob/a3c7d6c13984d884ccce80df88b950f0723a3af0/lib/Sema/TypeCheckDeclOverride.cpp#L540 somehow try to detect cases where you have a property trying to override a no-args function on base class or vice versa and try to provide a fix-it to provide a fix it for making one into another. For example, the fix-it offered will make the func in the example be

class D: C {
   - override func canBecomeFirstResponder() -> Bool {
   - }
   + override var canBecomeFirstResponder: Bool {
   + }
}

Since the override attempt have the same name and the same is a no-args function that produce the same result as the base class property (Bool).

[danielfalbo]

Swift Mentorship program mentee here, trying to contribute for the first time. Will dive deeper and work on this 😁

[RAJAGOPALAN-GANGADHARAN]

Hello @AnthonyLatsis - is this issue still open, can I give it a shot? Thanks!

[AnthonyLatsis]

You’re welcome to! Make sure it still reproduces though. Want we to assign you?

[danielfalbo]

I got busier and did not complete it yet, but I did make progress on this and was planning on opening the PR soon.

https://github.com/danielfalbo/swift/tree/fixit-override-func-that-should-be-override-var

[danielfalbo]

Update: I don’t think I’ll keep working on this anytime soon, I’m unassigning myself

[Rajveer100]

Let's try this!

[Rajveer100]

Hey @LucianoPAlmeida @AnthonyLatsis , I managed to find the error call site:
File --> /lib/Sema/TypeCheckDeclPrimary.cpp

(Case 1: When the method is overridden instead of the property)

FD->diagnose(diag::method_does_not_override, isClassContext)
                .highlight(OA->getLocation());

(Case 2: When the property is overridden instead of the method)

VD->diagnose(diag::property_does_not_override, isClassContext)
                .highlight(OA->getLocation());

So I think fixing the actual issue remains. I will try to do it!