[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

swift/lib/Sema/TypeCheckDeclOverride.cpp

Line 540 in a3c7d6c

diags.diagnose(decl, diag::override_multiple_decls_base,

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).