[Bug c++/61975] New: default template arguments do not work with out-of-class class declaration

[Bug c++/61975] New: default template arguments do not work with out-of-class class declaration

[vanyacpp at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61975

            Bug ID: 61975
           Summary: default template arguments do not work with
                    out-of-class class declaration
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vanyacpp at gmail dot com

GCC shows error on this code:

template <typename T>
struct x
{
    template <typename U>
    struct y;
};


template <>
template <typename U = int>
struct x<int>::y
{
    typedef U type;
};

x<int>::y<>::type a;

2.cpp:17:11: error: wrong number of template arguments (0, should be 1)
 x<int>::y<>::type a;
           ^
2.cpp:5:12: error: provided for ‘template<class U> struct x<int>::y<U>’
     struct y;
            ^
2.cpp:17:19: error: expected initializer before ‘a’
 x<int>::y<>::type a;
                   ^

I think this code is correct because default argument for parameter U is
specified. Clang compiles this code correctly.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ida393

--- Comment #6 from Martin Jambor <jamborm at gcc dot gnu.org> ---
(In reply to Martin Jambor from comment #1)
> However, I do not really know what the semantics of that flag mean so
> at least for now I am not going to propose this (I am also not quite
> sure this is the best place for the copy).  What properties of a
> function should be maintained in order to keep it flagged as a tm
> clone?

No answer, so I have actually proposed a variant of the patch in the
comment #1 to the mailing list:

https://gcc.gnu.org/ml/gcc-patches/2014-07/msg02105.html

[Bug c++/61975] default template arguments do not work with out-of-class class declaration

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61975

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-07-31
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
EDG accepts it too

[Bug c++/61975] default template arguments do not work with out-of-class class declaration

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61975

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Related to c++/53856

[Bug c++/61975] default template arguments do not work with out-of-class class declaration

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61975

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2014-07-31 00:00:00         |2021-8-4
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=53856

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
clang ICEs (at c++20) but accepts it at C++17 and before.
ICC acepts the code
MSVC rejects it with an error message close to GCC.