Re: C++ PATCH for c++/85976, ICE with USING_DECL in cp_tree_equal

[Jason Merrill <jason at redhat dot com>]

On Mon, Jun 4, 2018 at 11:44 AM, Marek Polacek <polacek@redhat.com> wrote:
> I've had no luck in reducing the testcase in this PR, creduce won't get even
> past the initial passes, and reducing by hand didn't get me very far, either.
>
> But the problem seems to be merely that we're not handling USING_DECLs in
> cp_tree_equal, and we can get there via comp_template_arguments.  In this case
> we have two USING_DECLs with different full names.
>
> So this patch just adds the USING_DECL case, similarly to e.g.
> https://gcc.gnu.org/ml/gcc-patches/2012-10/msg00799.html
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk/8?  I verified manually
> that this fixes the testcase from the PR.

Hmm, do these USING_DECLs have DECL_DEPENDENT_P set?  What do they
represent?  In the case of dependent USING_DECL I'd think we want to
compare the scope and name rather than just return false.

I think we do want a reduced testcase.  Maybe add the needs-reduction
tag if you're having trouble reducing it yourself?

Jason