[CSDiagnostics] Improving the fix-it for defining computed properties

[theblixguy]

This PR offers an improvement when the user is trying to define a computed property that is initialised with a closure. For example:

class Foo {
  var something: Int = { return 0 }
}

We currently emit an error diagnostic for the above, with a fix-it to add ():

Function produces expected type 'Int'; did you mean to call it with '()'?

In case of extensions, we emit:

Extensions must not contain stored properties

With this change, we will offer another fix-it to convert it into a computed property, by removing the = and if the property is immutable, then also changing the let to a var.

Resolves SR-9267.

[theblixguy]

cc @xedin

[xedin]

LGTM! I only wonder though if problems like this are actually diagnosed via fixes or are they still failing through to CSDiag?

[theblixguy]

@xedin For this specific case, it does go through the fix, but there are other cases where it doesn't go through the fix. I was running the tests and got a couple of failures, so I need to figure out a way to create a fix for all the cases, or leave the code in CSDiag so it can catch those other cases.

[xedin]

@theblixguy I think it would be great to factor this logic into a separate diagnostic which could be used from both places if possible...

[theblixguy]

@xedin I have extracted the fix-it code into a separate method in ContextualFailure. Is that what you meant?

[xedin]

@swift-ci please smoke test

[theblixguy]

Build failure on OSX looks unrelated to me.

20:48:07 Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.keyNotFound(CodingKeys(stringValue: "kind", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: "kind", intValue: nil) ("kind").", underlyingError: nil)): file /Users/buildnode/jenkins/workspace/swift-PR-osx-smoke-test/branch-master/swiftpm/Sources/SPMLLBuild/llbuild.swift, line 186

[xedin]

@swift-ci please smoke test macOS platform

[theblixguy]

Same error in SwiftPM. @aciidb0mb3r could you take a look? SPMLLBuild is crashing due to a force-unwrap here: https://github.com/apple/swift-package-manager/blob/master/Sources/SPMLLBuild/llbuild.swift#L186

20:48:07 Fatal error: 'try!' expression unexpectedly raised an error: Swift.DecodingError.keyNotFound(CodingKeys(stringValue: "kind", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: "kind", intValue: nil) ("kind").", underlyingError: nil)): file /Users/buildnode/jenkins/workspace/swift-PR-osx-smoke-test/branch-master/swiftpm/Sources/SPMLLBuild/llbuild.swift, line 186

[aciidgh]

Should be fixed now, try rerunning the CI

[theblixguy]

I don't have the permission to run the CI, could you run the smoke test on macOS? It was the one that failed.

[aciidgh]

@swift-ci please smoke test macOS platform

[aciidgh]

@swift-ci please smoke test macOS platform

[theblixguy]

Thanks, all tests are passing now 🎉

[theblixguy]

@xedin Can I cherry pick this to the 5.1 branch?

[xedin]

@theblixguy please do!