[PATCH] D149650: Give NullabilityKind a printing operator<<

Wed May 3 10:34:38 PDT 2023

aaron.ballman added a comment.

In D149650#4315211 <https://reviews.llvm.org/D149650#4315211>, @sammccall wrote:

> In D149650#4312389 <https://reviews.llvm.org/D149650#4312389>, @aaron.ballman wrote:
>
>> I guess I'm not seeing much motivation for this change. We already have `clang::getNullabilitySpelling()` and `const StreamingDiagnostic &clang::operator<<(const StreamingDiagnostic &DB, DiagNullabilityKind nullability)` and now we're adding a third way to get this information. If this is just for debug/testing purposes, can we use existing debug formatters to convert the enumeration value into the enumerator name instead?
>
> We're using NullabilityKind in our dataflow-based null-safety clang-tidy check <https://github.com/google/crubit/tree/main/nullability> that we hope to upstream when it works.

Ah, good to know! I think it would be reasonable to add this functionality once there's some agreement on adding the clang-tidy check.

> (The idea is to use `_Nullable` and `_Nonnull` annotations on API boundaries to gradually type pointers, and to provide a verification clang-tidy check and libraries to infer annotations for existing code. The actual clang-tidy check wrapper isn't in that repo yet, but it's trivial).
>
> It would be convenient if e.g. EXPECT_THAT(someVectorOfNK, ElementsAre(Nullable, Unspecified)) <https://github.com/google/crubit/blob/main/nullability/type_nullability_test.cc> printed something useful when it fails, if we could write OS << NK and get Unspecified rather than OS << getSpelling(NK) and get _Unspecified_Nullability, etc.
> This doesn't concern clang core (ha, there are no unit tests...) but there's no reasonable way to do this downstream without using a different type.

Hmmm, but does this need to be added to `Specifiers.h` instead of being kept packaged up with clang-tidy? For things like AST matchers, we usually ask that the matcher remain local to the clang-tidy check unless the same matcher is needed in multiple checks. This feels somewhat similar, despite it not being related to AST matching -- if the only need for this functionality exists out of the clang tree, can we keep it out of the clang tree until we find more needs?

>> `StreamingDiagnostic &clang::operator<<`
>
> This actually wants the user-visible spelling, so I think it can just use getSpelling... if I make that change we're back to just two implementations :-)

Oh, I really like those changes! Feel free to land that as an NFC change if you'd like (the addition of quotes is a bug fix, but not really a functional change).

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