[cxx-interop][IRGen] Walk initializer decls when walking constructor decls

[bulbazord]

This addresses SR-15272.

When you have a function (e.g. 'foo') which is used in a constructor
initializer (e.g. constructor of some class 'Bar'), and you use the
constructor from swift code without directly using the function (e.g.
Bar's ctor is used from swift but foo isn't, foo is used from Bar's ctor),
you will get a link error. My fix is as follows:

When walking the clangAST to be imported, make sure you look at each
CXXCtorInitializer for each CXXConstructorDecl you see.

[plotfi]

Nice work @bulbazord.

@hyp @zoecarver

[bulbazord]

For more context, see: #39551

[zoecarver]

I was under the impression that #35056 fixed this. This test fails on main?

[bulbazord]

I was under the impression that #35056 fixed this. This test fails on main?

The test added in this PR fails on main (at least on my machine). I believe the key difference here is that that patch visits CXXConstructExprs and not CXXConstructDecls. My understanding is that in the test I have written, there are no CXXConstructExprs to be walked in the clangAST, but there is definitely a CXXConstructDecl.

[zoecarver]

Tested locally. Looks like this is actually an issue.

It's odd that the decl finder doesn't visit the inits already. Anyway, this looks great. Thank you for fixing it.

[zoecarver]

My understanding is that in the test I have written, there are no CXXConstructExprs to be walked in the clangAST, but there is definitely a CXXConstructDecl.

Hmm I suppose that makes sense. This was probably something the Google folks overlooked in their patch, as I suspect they meant to test this case. Thank you for explaining :)

[zoecarver]

I'll trigger the bots once that test is fixed.

Sorry if this is a big ask, but it looks like a lot of similar things are already tested in class/inline-function-codegen/constructor-calls-whatever.swift. Can you factor your tests into those tests, I really want to keep the tests as organized as possible. Especially as more people start contributing.

[bulbazord]

@zoecarver I went ahead and merged what I had with the tests in class/inline-function-codegen/constructor-calls-XXX.swift tests. Let me know if there's anything else you'd like to see changed.

[zoecarver]

Beautiful. Thank you!

[zoecarver]

@swift-ci please test.

[bulbazord]

Modified the tests to fix the windows failure. Hopefully things are good now. Could you retrigger the tests @zoecarver?

[zoecarver]

@swift-ci please test.

[drodriguez]

@swift-ci please smoke test

[bulbazord]

I believe I've fixed the windows test (2 characters were swapped in the mangled name, whoops!).
I hope it works and can go in soon!

[drodriguez]

@swift-ci please smoke test

[drodriguez]

@swift-ci please test Linux platform