[PATCH] D40562: [Sema] Ignore decls in namespaces when global decls are not wanted.

[Ilya Biryukov via Phabricator via cfe-commits]

ilya-biryukov added a comment.

In https://reviews.llvm.org/D40562#941570, @arphaman wrote:

> I'm not actually 100% sure, but I would imagine that this one of the reasons, yes. It would be nice to improve the cache to have things like namespace-level `Decl`, although how will lookup work in that case? Btw, do you think the cache can be reused in clangd as well?


As Eric mentioned, we are planning to have project-global completion for namespace-level Decls (to have completion items not #included in the current file and add the #include directive properly).  So the cache is probably not that useful to clangd long-term.
For proper lookup in the cache that include all namespace-level Decls I'd go with tweaking `LookupVisibleDecls` so that it does not deserialize everything from the preamble, but rather provides a list of scopes that we need to get completion items from. Though sounds simple, it may be a non-trivial change and we shouldn't probably pursue it as part of this change.
(We'll probably need it for clangd too).

In https://reviews.llvm.org/D40562#941735, @ioeric wrote:

> I took a quick look at the completion cache and lookup code. I think the completion cache also assumes that top-level decls are only TU-level decls, and this assumption seems to be also built into the lookup code. At this point, I am inclined to add a separate completion option for what I want (`IgnoreDeclsInTUOrNamespaces`?). Regarding cache in clangd, I think it might be useful short-term, when we still use Sema's global code completion, but long term, we would use symbols from clangd's indexes, so the cache would not be useful anymore.


+1 for having a separate flag. Maybe call it `IncludeNamespaceLevelDecls` instead? (I'd say TU is also a (global) namespace from completion's point of view).


https://reviews.llvm.org/D40562