[Bug c++/22136] [4.1/4.2 regression] Rejects old-style using declaration

["mmitchel at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #13 from mmitchel at gcc dot gnu dot org  2006-01-15 23:57 -------
The problem is that we originally encounter the nested name specifier I<T>::B
during a call from cp_parser_constructor_declarator_p.  That function sets
check_dependency_p to false, because we do have to resolve dependency names
when parsing declarators.  The result of the nested name specifier lookup is
cached at that point, with the result that when we re-encounter it, we use the
value we got before, even though that is no longer correct.

Because the caching should not be required for correctness (although it does
eliminate duplicate error messages in some cases), we could probably disable
the caching.  

Another approach would be not to look for the nested name specifier in class
scope, since there it is not valid to declare a constructor in-class as "C::C",
although we have long accepted that, with a warning.  Preliminary testing shows
that will fix the bug, although it will break 
  struct S { S::S(); };
which is current accepted with -fpermissive.  I will attach that patch for
reference.

Because of the problem with -fpermissive, I think it's better to try
conditionalizing the caching in cp_parser_nested_name_specifier_opt on
check_dependency.  That also fixes the bug; I'm testing that patch now.

For the original submitter: ARM-style access declarations (e.g.,
"I<T>::B::foo;") are deprecated in current C++.  The preferred way to write the
code is now "using I<T>::B::foo;", and that additional contextual information
avoids the bug in G++ as well.  So, the best immediate workaround is to insert
the "using" keyword.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|nathan at gcc dot gnu dot   |mark at codesourcery dot com
                   |org                         |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22136