[PATCH] D81552: [ASTMatchers] Added hasDirectBase and hasClass Matchers

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang/include/clang/ASTMatchers/ASTMatchers.h:3553
+/// \endcode
+AST_MATCHER_P(CXXBaseSpecifier, hasClass, internal::Matcher<CXXRecordDecl>,
+              InnerMatcher) {
----------------
sammccall wrote:
> aaron.ballman wrote:
> > jkorous wrote:
> > > aaron.ballman wrote:
> > > > njames93 wrote:
> > > > > jkorous wrote:
> > > > > > aaron.ballman wrote:
> > > > > > > jkorous wrote:
> > > > > > > > Nit: while "[base specifier] `hasType`" sounds natural to me for some reason `hasClass` doesn't. English is not my first language though.
> > > > > > > I agree that `hasClass` seems unnatural here. Out of curiosity, could we modify the `hasName` matcher to work on base specifiers so you can write: `cxxRecordDecl(hasAnyBase(hasName("Base")))` as shorthand for the more wordy version `cxxRecordDecl(hasAnyBase(hasType(cxxRecordDecl(hasName("Base")))))`?
> > > > > > Wouldn't it be strange to treat `hasName` differently than all the other narrowing matchers? Honest question - I feel that `hasName` might be the most commonly used, just don't know if that's enough to justify this.
> > > > > > https://clang.llvm.org/docs/LibASTMatchersReference.html#narrowing-matchers
> > > > > Repurposing `hasName` would be a pain especially considering 99% of its use cases wont be for base class matching.
> > > > > Wouldn't it be strange to treat hasName differently than all the other narrowing matchers? Honest question - I feel that hasName might be the most commonly used, just don't know if that's enough to justify this. https://clang.llvm.org/docs/LibASTMatchersReference.html#narrowing-matchers
> > > > 
> > > > Different how? I'm suggesting to overload `hasName` to work on a `CXXBaseSpecifier` since those have a name.
> > > > 
> > > > > Repurposing hasName would be a pain especially considering 99% of its use cases wont be for base class matching.
> > > > 
> > > > I'm asking what the right API is for users, though, which is a bit different. Base specifiers have names (there are no unnamed base specifiers), so to me, it makes more sense for `hasName` to work with them directly since that is the thing that does name matching.
> > > > 
> > > > I think you can accomplish this by using a `PolymorphicMatcherWithParam1` like we do for `hasOverloadedOperatorName` which can narrow to either a `CXXOperatorCallExpr` or a `FunctionDecl`.
> > > >> Wouldn't it be strange to treat hasName differently than all the other narrowing matchers? Honest question - I feel that hasName might be the most commonly used, just don't know if that's enough to justify this. https://clang.llvm.org/docs/LibASTMatchersReference.html#narrowing-matchers
> > > 
> > > > Different how? I'm suggesting to overload hasName to work on a CXXBaseSpecifier since those have a name.
> > > 
> > > What I meant is that technically we can overload any `Matcher<CXXRecordDecl>` matcher in the same fashion so having the overloaded version of `hasName` only makes it somewhat special (and someone might argue that it'd impact consistency of matchers composability). Anyway, I'm fine with your suggestion!
> > Ah, I see what you mean -- thanks for explaining. I'm on the fence about this. One the one hand, base specifiers *in the AST* do not have names, so it seems defensible to say that `hasName` should not handle a base specifier. On the other hand, base specifiers *in the language* are identifiers that always have a name, so it seems defensible to say that `hashName` should handle a base specifier.
> > 
> > Pulling in some more folks to see if a wider audience brings consensus.
> I think I agree that it's reasonable/consistent to do this, but I'm not sure it's a good idea.
> Base specifier -> type -> class -> name seems like the most *regular* traversal that reflects the shape/concepts of the AST, shortcutting steps makes the model (IMO) more complicated to make it more terse.
> Is matching a base specifier with a hardcoded name really common enough in absolute terms that people should keep this special case in their heads?
> 
> I think `hasType(cxxRecordDecl(hasName("Base")))` a bit better, but i think of *expressions* having types, and would prefer `specifiesType` or just `specifies` at the outside.
> But just my 2c and I'm not deeply familiar with the conventions here - I can live with any of the options.
> Is matching a base specifier with a hardcoded name really common enough in absolute terms that people should keep this special case in their heads?

Thanks for the perspective. I don't think base specifiers will be matched all that often, but I'm also not certain it's a special case because base specifiers are conceptually things with names even if they're not exposed as such via our AST. However, you bring up a good point about modelling the shape of the AST and that does suggest base specifier -> type -> class -> name as the right way to go.

> I think hasType(cxxRecordDecl(hasName("Base"))) a bit better, but i think of *expressions* having types, and would prefer specifiesType or just specifies at the outside.

If `hasType` only worked on expressions, I would be okay with adding `specifies` or `specifiesType` for this functionality, but since `hasType` works on expressions and declarations, I think it's more natural to reuse `hasType` for the specifier than to introduce `specifiesType` (or `hasClass`) for base specifiers (which name a class type).


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  https://reviews.llvm.org/D81552/new/

https://reviews.llvm.org/D81552