[Bug c++/50080] New: error: 'template' (as a disambiguator) is only allowed within templates

[Bug c++/50080] New: error: 'template' (as a disambiguator) is only allowed within templates

[solodon at mail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

             Bug #: 50080
           Summary: error: 'template' (as a disambiguator) is only allowed
                    within templates
    Classification: Unclassified
           Product: gcc
           Version: 4.5.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: solodon@mail.com


Hi,

Consider the following code snippet compiled as:

g++ -std=c++0x test.cpp

In particular the two instantiations of B: one in the template context and the
other one in non-dependent scope.

template <typename T>
struct A
{
    template <typename U>
    struct B {};
};

template <typename T>
void test()
{
    typename A<T>::template B<int> b;
}

int main()
{
    typename A<double>::template B<int> b;
}

My GCC complains about the second instantiation saying: 

error: 'template' (as a disambiguator) is only allowed within templates

and surely enough removing template there fixes the problem. The keyword
typename used for a similar purpose of disambiguating a type in a non-template
context is accepted even though redundant. Allowing typename seems to be in
line with the relaxed rule of C++0x. I think, however, that the template
keyword should similarly be allowed in non-dependent context accordingly to the
C++0x standard (and not allowed accordingly to C++03).

Here is a snippet from C++0x standard draft (FDIS n3291, section 14.2[5]) I
could get a hold of:

``A name prefixed by the keyword template shall be a template-id or the name
shall refer to a class template.
[ Note: The keyword template may not be applied to non-template members of
class templates. -end
note ] [ Note: As is the case with the typename prefix, the template prefix is
allowed in cases where it is
not strictly necessary; i.e., when the nested-name-specifier or the expression
on the left of the -> or . is not
dependent on a template-parameter, or the use does not appear in the scope of a
template. -end note ]''

I think that the second note implies that template keyword should have been
allowed in the example above in much the same way the typename is, please
correct me if I'm wrong.

The practical reason I need this behavior for is that I have a code snippet
that is generated by a macro. With template being allowed in non-dependent
context I can have a single macro that can be used in dependent and
non-dependent contexts, while without this behavior (as well as in C++03) I
will need to have 2 separate (largely duplicated) macros for each of the uses.

Thanks,
Yuriy

[Bug c++/50080] [C++0x] error: 'template' (as a disambiguator) is only allowed within templates

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-08-15 08:51:44 UTC ---
You're right, but g++ doesn't claim to support everything in C++11 yet,
especially not in the 4.5 release series which is nearly a year and half old,
the C++0x draft changed a lot in that time.

[Bug c++/50080] [C++0x] error: 'template' (as a disambiguator) is only allowed within templates

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-01-28 05:46:23 UTC ---
Note typename was PR 22154.

[Bug c++/50080] [DR 468] error: 'template' (as a disambiguator) is only allowed within templates

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-01-28
            Summary|[C++0x] error: 'template'   |[DR 468] error: 'template'
                   |(as a disambiguator) is     |(as a disambiguator) is
                   |only allowed within         |only allowed within
                   |templates                   |templates
     Ever Confirmed|0                           |1

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-01-28 05:50:18 UTC ---
Confirmed.
http://www.open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#468 was the defect
report against the C++ standard.

Since we support other CD1 with -std=c++98, I am removing the C++0x marker.

[Bug c++/50080] [DR 468] error: 'template' (as a disambiguator) is only allowed within templates

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |paolo.carlini at oracle dot
                   |gnu.org                     |com

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-05 16:15:22 UTC ---
Looking at cp_parser_optional_template_keyword, this seems very easy to fix.

[Bug c++/50080] [DR 468] error: 'template' (as a disambiguator) is only allowed within templates

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

--- Comment #5 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-10-15 16:48:01 UTC ---
Author: paolo
Date: Mon Oct 15 16:47:52 2012
New Revision: 192465

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=192465
Log:
/cp
2012-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/50080
    * parser.c (cp_parser_optional_template_keyword): Implement
    Core/468, allow outside template.

/testsuite
2012-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/50080
    * g++.dg/parse/tmpl-outside2.C: New.
    * g++.dg/parse/tmpl-outside1.C: Adjust.
    * g++.dg/template/qualttp18.C: Likewise.
    * g++.old-deja/g++.pt/memtemp87.C: Likewise.
    * g++.old-deja/g++.pt/overload13.C: Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/parse/tmpl-outside2.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/parser.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/parse/tmpl-outside1.C
    trunk/gcc/testsuite/g++.dg/template/qualttp18.C
    trunk/gcc/testsuite/g++.old-deja/g++.pt/memtemp87.C
    trunk/gcc/testsuite/g++.old-deja/g++.pt/overload13.C

[Bug c++/50080] [DR 468] error: 'template' (as a disambiguator) is only allowed within templates

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.8.0

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-15 16:49:26 UTC ---
Done.

[Bug c++/50080] [DR 468] error: 'template' (as a disambiguator) is only allowed within templates

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50080

--- Comment #7 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-10-15 19:13:45 UTC ---
Author: paolo
Date: Mon Oct 15 19:13:41 2012
New Revision: 192470

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=192470
Log:
/cp
2012-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/50080 (again)
    * parser.c (cp_parser_optional_template_keyword): When -pedantic
    and C++98 mode restore pre-Core/468 behavior.

/testsuite
2012-10-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/50080 (again)
    * g++.dg/parse/tmpl-outside2.C: Tweak, error in C++98.
    * g++.dg/parse/tmpl-outside1.C: Likewise.
    * g++.dg/template/qualttp18.C: Likewise.
    * g++.old-deja/g++.pt/memtemp87.C: Likewise.
    * g++.old-deja/g++.pt/overload13.C: Likewise.

Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/parser.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/parse/tmpl-outside1.C
    trunk/gcc/testsuite/g++.dg/parse/tmpl-outside2.C
    trunk/gcc/testsuite/g++.dg/template/qualttp18.C
    trunk/gcc/testsuite/g++.old-deja/g++.pt/memtemp87.C
    trunk/gcc/testsuite/g++.old-deja/g++.pt/overload13.C