Revert "[SwiftLexicalLookup] New unqualified lookup implementation validation"

[bnbarham]

Reverts #77140 as it causes nightly toolchain failures for Debian 12/Fedora 39/Ubuntu 24.04.

[bnbarham]

@MAJKFL I believe the issue here is that there's now a cycle from swiftAST -> swiftASTGen -> swiftAST. It passed on PR testing as it uses Ubuntu 20.04 and ends up using lld rather than gold, which appears to handle the cycle.

[bnbarham]

@swift-ci please smoke test

[MAJKFL]

Ah, I see there’s a cycle. Thank you for caching that! It does seem to be a bit tricky to fix. I don’t think it would be possible to move the validation outside of ASTGen as it uses it to e.g. access cached if config configured regions, or the parsed source file itself.

Would it make sense to move the logic somewhere outside of swiftAST, or to possibly inject LoggingASTScopeDeclConsumer at all unqualified lookup entry points? If it’s not a viable option, do you perhaps have any suggestions for an alternative approach? @bnbarham @DougGregor

I think it's a good idea to revert it for now and I'll look into fixing it in a subsequent PR.

[bnbarham]

Would it make sense to move the logic somewhere outside of swiftAST, or to possibly inject LoggingASTScopeDeclConsumer at all unqualified lookup entry points

I think the easiest thing here would probably be to have a new Swift module, ie. move LexicalLookup out of ASTGen.

EDIT: I just noticed you said:

I don’t think it would be possible to move the validation outside of ASTGen as it uses it to e.g. access cached if config configured regions, or the parsed source file itself.

I'd need to look into that more, it does seem like it should be possible to split them 🤔. We probably need to split out more of ASTGen though - CC @rintaro

[hjyamauchi]

I think the original PR introduces the new dll _CompilerSwiftLexicalLookup.dll and it needed to be added to the installer manifest around here https://github.com/swiftlang/swift-installer-scripts/blob/6cecc7c46d1170a3bc3e1ff8838181418e037397/platforms/Windows/bld/bld.wxs#L418 ?

[bnbarham]

Thanks @hjyamauchi, will indeed need to add to swift-installer-scripts too.

[rintaro]

I will see if we can extract ExportedSourceFile related code out of ASTGen, so ASTGen and the lexical lookup module depend on it.