[PATCH] D37474: [PCH] Allow VFS to be used for tests that generate PCH files

[Cameron via Phabricator via cfe-commits]

cameron314 added a comment.

I suppose we could do the overlay manually in all the tests that need it; I guess it depends on what the goal of the VFS support is. To my mind, it doesn't make sense that a file is placed in the RealFS in the first place if a VFS is used, but this is quite entrenched in the current design and difficult to change. In which case, I would argue that parsing a file with a preamble and a VFS should not give a cryptic error without an explicit overlay, but rather "just work". But I agree my current patch is a little crude in that it allows access to the entire RealFS via the VFS.

I could change the automatic overlay to *only* support access to the generated PCH file, similar to how the `FilteredFileSystem` you've pointed out works, but for a single file only. Would that be acceptable?


https://reviews.llvm.org/D37474