On Tue, Sep 8, 2015 at 9:18 AM, Manuel Klimek <kli...@google.com> wrote: > On Tue, Sep 8, 2015 at 2:23 PM Aaron Ballman <aa...@aaronballman.com> wrote: >> >> On Tue, Sep 8, 2015 at 5:40 AM, Manuel Klimek <kli...@google.com> wrote: >> > Yea, we had that discussion a few times, and I can never remember why we >> > ended up in the state we're in. >> > We definitely had a time where we switched to just using the exact same >> > name >> > as the node's class name for the matchers. >> > I *think* we didn't do it for cxxRecordDecl, because Richard said that's >> > a >> > relic we should get rid of anyway, but I'm not sure. >> >> FWIW, I think the state we're in is the worst of all worlds. It's not >> intuitive that recordDecl() doesn't match a struct in C mode, and as >> it stands, there is no way to match a struct or union declaration in C >> at all. > > > Agreed. Best intentions. Worst possible outcome. That's software development > :) > >> > >> > On Fri, Sep 4, 2015 at 8:32 PM Aaron Ballman <aa...@aaronballman.com> >> > wrote: >> >> >> >> It turns out that the recordDecl() AST matcher doesn't match >> >> RecordDecl objects; instead, it matches CXXRecordDecl objects. This >> >> is... unfortunate... as it makes writing AST matchers more complicated >> >> because of having to translate between recordDecl()/CXXRecordDecl. It >> >> also makes it impossible to match a struct or union declaration in C >> >> or ObjC. However, given how prevalent recordDecl()'s use is in the >> >> wild (I'm guessing), changing it at this point would be a Bad Thing. >> >> >> >> For people trying to write AST matchers for languages like C or ObjC, >> >> I would like to propose adding: >> >> >> >> structDecl() >> >> unionDecl() >> >> tagDecl() >> >> >> >> These will match nicely with the existing enumDecl() AST matcher. >> >> >> >> Additionally, I would like to add cxxRecordDecl() to match >> >> CXXRecordDecl objects. While it duplicates the functionality exposed >> >> by recordDecl(), it more clearly matches the intention of which AST >> >> node it corresponds to. >> >> >> >> Finally, I would like to undocument recordDecl() and change our >> >> existing documentation and AST matcher uses to use >> >> cxxRecordDecl/structDecl() instead. Maybe someday we can deprecate >> >> recordDecl() more officially. >> >> >> >> I'm open to other ideas if there are better ways to move forward. If >> >> you think changing the meaning of recordDecl() is acceptable, I can >> >> also go that route (though I would still propose adding unionDecl() >> >> and cxxRecordDecl() in that case). >> > >> > >> > I think changing recordDecl is acceptable. I believe very few tools will >> > actually start doing wrong things because of it. I'd like more opinions >> > first, though :) >> >> I was giving this more thought over the long weekend, and I think you >> may be right. I think changing recordDecl() to mean RecordDecl will >> fix more code than it breaks, so long as we take a holistic approach >> to the change and see which narrowing and traversal matchers we need >> to fix up at the same time. When I tried to think of AST matchers that >> mean CXXRecordDecl but *not* RecordDecl, they were horribly contrived >> because you usually are matching on additional selection criteria that >> is specific to C++ (such as hasMethod() or isDerivedFrom()) which >> would cause the match to continue to fail, as expected. Code that uses >> recordDecl() to mean RecordDecl will suddenly start to match in more >> cases, but that's likely to be a bug fix more than a breaking change. >> To the best of my understanding, the only breaking cases would be >> where you wrote recordDecl(), meant CXXRecordDecl, had no further >> narrowing or traversal matchers, and were compiling in C mode; with >> the result being additional unexpected matches. > > > Ah, there's one thing that can break: the compile can break: > recordDecl(hasMethod(...)) will *not* compile (it'll work in the dynamic > matchers and fail as you suggest, but the in-C++ DSL does more static type > checking). > I don't think that's super bad though. > >> >> So perhaps it would make sense to: >> >> 1) Make recordDecl() mean RecordDecl >> 2) Do a comprehensive review of matchers that take a CXXRecordDecl and >> see if they should instead take a RecordDecl >> 3) Add unionDecl() as a node matcher (or should we add isUnion() and >> isStruct() as narrowing matchers?) >> 4) Add tagDecl() as a node matcher, but not add cxxRecordDecl() > > > Why not add cxxRecordDecl()? I think we need it if we want narrowing > matchers on CXXRecordDecl?
If Richard thinks CXXRecordDecl is an anachronism, I figured we didn't want to expose it. Instead, we could make hasMethod (et al) accept a RecordDecl and do the type checking for the caller. Then recordDecl(hasMethod(...)) continues to compile and work, and when hasMethod is given a RecordDecl instead of a CXXRecordDecl, it simply matches nothing. But you bring up a good point about the C++ DSL being a problem still, I hadn't considered that. ~Aaron > >> >> >> ~Aaron >> >> > >> >> >> >> >> >> Thanks! >> >> >> >> ~Aaron _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
