[PATCH] D135557: Add needsImplicitDefaultConstructor and friends

Thu Oct 20 10:45:00 PDT 2022

aaron.ballman added a comment.

In D135557#3871716 <https://reviews.llvm.org/D135557#3871716>, @dblaikie wrote:

> (I'm still sort of curious how the AST matchers deal with all this - I guess they must have Sema available, because I'd assume they make all sorts of queries like "is this constructible from that" - since they're often trying to generate new code and want to know what constructs will be valid, which is different from the indexing use case, admittedly)

Nope, AST matchers don't have Sema available, so they don't have a way to query "is this constructible from that". You've got the AST itself (and the `ASTContext`) and not a whole lot else beyond that.

> Maybe the answer is the C API isn't for this sort of thing/it's too nuanced to expose there?
>
> But if you reckon the inconsistency isn't so bad, I won't be up in arms if you decide to go with having the indexing C API instantiate all the implicit special members all the time. I can see the value/it's only restricted to the indexing API. Does seem a bit unfortunate in tetrms of consistency.

Yeah, I think you convinced me that the consistency issue is something we should be wary of. I don't think we want to get into a situation where C index/AST matching is fundamentally a different AST than the rest of the compiler.

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https://reviews.llvm.org/D135557