[SR-13503] InsertExplicitCall fix not created for callable values

[theblixguy]

Previous ID	SR-13503
Radar	rdar://problem/68376691
Original Reporter	@theblixguy
Type	Bug

Environment

Swift version 5.3-dev (LLVM 19447e2, Swift e41a0976e0bdb09)
Target: x86_64-apple-darwin19.5.0

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, TypeChecker
Assignee	None
Priority	Medium

md5: cf7afdf3fd38fee6a0ef870bb5bd3d36

Issue Description:

struct S {
  func callAsFunction() -> Int { 0 }
}

let s = S()

func doIt(arg: Int) { print(arg) }
doIt(arg: s) // error: cannot convert value of type 'S' to expected argument type 'Int'

In the above scenario, it is possible to call s (by adding ()) to produce the expected value of type Int. So, we should create the InsertExplicitCall fix (or create a fix tailored for callable values) in order to emit a better diagnostic.

[theblixguy]

cc @xedin @hborla

[typesanitizer]

@swift-ci create

[xedin]

It looks like we need to detect that it's possible to call `s` in this example and produce a tailored fix. Do you want to take a look luciano (JIRA User)?

[LucianoPAlmeida]

Sure @xedin, I'll take a look 🙂

[LucianoPAlmeida]

Here is a PR https://github.com/apple/swift/pull/34006