klimek added a reviewer: rsmith.
klimek added inline comments.
================
Comment at: clangd/XRefs.cpp:559
+ //- auto& i = 1;
+ bool VisitDeclaratorDecl(DeclaratorDecl *D) {
+ if (!D->getTypeSourceInfo() ||
----------------
malaperle wrote:
> klimek wrote:
> > sammccall wrote:
> > > malaperle wrote:
> > > > sammccall wrote:
> > > > > out of curiosity, why not implement `VisitTypeLoc` and handle all the
> > > > > cases where it turns out to be `auto` etc?
> > > > > Even for `auto&` I'd expect the inner `auto` to have a `TypeLoc` you
> > > > > could visit, saving the trouble of unwrapping.
> > > > >
> > > > > (I'm probably wrong about all this, I don't know the AST well. But
> > > > > I'd like to learn!)
> > > > From what I saw, there are actually two different AutoType* for each
> > > > textual "auto". The AutoType* containing the deduced type does not get
> > > > visited via a typeloc. It's not entirely clear to me why since I don't
> > > > know the AST well either. I was thinking maybe the first is created
> > > > when the type is not deduced yet and later on, then the rest of the
> > > > function or expression is parsed, a second one with the actual type
> > > > deduced is created. If I look at the code paths where they are created,
> > > > it seems like this is roughly what's happening. The first one is
> > > > created when the declarator is parsed (no deduced type yet) and the
> > > > second is created when the expression of the initializer (or return
> > > > statement) is evaluated and the type is then deduced. The visitor only
> > > > visits the first one's typeloc. I don't think I'm knowledgeable enough
> > > > to say whether or not that's a bug but it seems on purpose that it is
> > > > modelled this way. Although it would be much nicer to only have to
> > > > visit typelocs...
> > > > The AutoType* containing the deduced type does not get visited via a
> > > > typeloc
> > > Ah, OK.
> > > Could you add a high level comment (maybe on the class) saying this is
> > > the reason for the implementation? Otherwise as a reader I'll think "this
> > > seems unneccesarily complicated" but not understand why.
> > >
> > > @klimek Can you shed any light on this?
> > Can't you go from AutoTypeLoc -> AutoType -> getDeducedType()?
> The visitor doesn't visit the AutoTypeLoc that has the deduced type. In fact,
> there are two AutoType* instances. I'm not sure that's is a bug that there
> are two AutoType*, or if not visiting both AutoTypeLoc is a bug...or neither.
+Richard Smith:
This is weird. If I just create a minimal example:
int f() {
auto i = f();
return i;
}
I only get the undeduced auto type - Richard, in which cases are auto-typed
being deduced? The AST dump doens't give an indication that there was an auto
involved at all. Is this the famous syntactic vs. smenatic form problem? Do we
have a backlink between the AutoTypeLoc and the deduced type somewhere?
Repository:
rCTE Clang Tools Extra
https://reviews.llvm.org/D48159
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