[cfe-commits] [Patch] Fix parser diagnostic on class specifiers following c++11 attributes

[Richard Smith]

On Thu, Nov 15, 2012 at 10:33 AM, Michael Han <fragmentshaders at gmail.com> wrote:
> Hi,
>
> Consider this code
> class [[foo]] c [[foo]];
>
> Clang generates diagnostic like this:
> error: an attribute list cannot appear here
> class [[foo]] c [[foo]];
>       ^~~~
>
> I think the first attribute is conforming, and it's the second attribute
> that should be diagnosed.

Yes, I agree that it would be better to point the diagnostic at the
second attribute-specifier-seq (and ideally to say that it's in the
wrong place, and offer a fixit...).

> Attached the patch that fixes this.

I don't think your approach here is going to work. This is valid:

  class c {};
  class c [[ ]] x;

I believe your patch would treat 'class c' as a declaration in the
second line, which it is not.

In order to correctly handle this, I suggest you parse attributes
after the class name as well as before it, before trying to classify
the reference. If you then find that it's a TUK_Reference, return the
attributes you found after the class name to the caller, for them to
handle appropriately. Otherwise, produce a diagnostic indicating that
they were written in the wrong place (offering a fixit would be
awesome...). For a class definition, you should probably look for
attributes both before and after the optional 'final'.

Thanks for looking into this!