Fix unknown type cast crash

[augusto2112]

This PR fixes the crash reported here. In addition, it improves the error message when type reconstruction fails in the SwiftASTContext class.

[augusto2112]

Hi @vedantk, could you take a look at this, if/when you have the time? Related to this post you helped me with

[vedantk]

Hey @augusto2112, thanks for doing this, this seems like the right approach. I noticed that there are quite a few formatting diffs in the file unrelated to your change: perhaps these got pulled in by clang-format? Please update the diff to remove those unrelated changes if possible. It should be good to land afterwards.

[augusto2112]

Hi @vedantk, I was thinking in doing a small change:

expose a public SwiftASTContext::ReconstructType(ConstString) (no error), and do the whole "if error, add diagnostic" here. That way we don't need AddErrorStatusAsGenericDiagnostic in SwiftASTContext's public API and we remove the "if error" logic that is duplicated in three places.

What do you think?

I noticed that there are quite a few formatting diffs in the file unrelated to your change: perhaps these got pulled in by clang-format?

Yeah, I think it was because of clang-format. I'll update that.

[vedantk]

It may be convenient in the future to have AddErrorStatusAsGenericDiagnostic as part of SwiftASTContext's public interface. I think it'd be fine to add the helper, though.

[augusto2112]

@vedantk OK, I pushed the changes.

[vedantk]

@swift-ci test

[vedantk]

@augusto2112 could you open a PR submitting this change to apple:swift/master-next as well? Otherwise, the change will disappear after the next rebase (we do not auto merge lldb changes from swift/master to swift/master-next). If you don't have the bandwidth for that, just lmk, and I'll handle it. Thanks.

[vedantk]

(Incidentally if you've done other lldb work on swift/master, this will need to be cherry-picked to swift/master-next as well.)

[augusto2112]

@vedantk Ok, will do!

(Incidentally if you've done other lldb work on swift/master, this will need to be cherry-picked to swift/master-next as well.)

I've done a couple, I usually wait to see if the tests pass before cherry-picking so I don't have to re-do the master-next in case I have to change something.