[PATCH] D133468: [clang] Implement divergence for TypedefType and UsingType

[Sam McCall via Phabricator via cfe-commits]

sammccall added a comment.

The descriptions here are pretty general and opaque nad it's hard to follow what this means in practice.
It sounds like the motivating cases are to do with template instantiation - can we see them? e.g. code + proposed diagnostics before/after, or some other description of how this will be used?
The ternary-expression stuff doesn't seem compelling enough to justify the complexity here without more context. (Probably others have this context, but future readers of this code won't).

My intuition is that if a type desugars to something other than what the UsingDecl points to, then UsingType isn't the right model - it seems we're trying to shim some extra indirection that doesn't have much to do with `using`. Maybe we can isolate the complexity better in a new sugar typenode, rather than weakening the semantics of Using/TypedefType?
But I can easily imagine I'm missing the point and concrete examples might clear it up.


Repository:
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  https://reviews.llvm.org/D133468/new/

https://reviews.llvm.org/D133468