[Bug c++/66260] New: [C++14] Failure to compile variable template with recursively defined partial specialization

[Bug c++/66260] New: [C++14] Failure to compile variable template with recursively defined partial specialization

[Casey at Carter dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

            Bug ID: 66260
           Summary: [C++14] Failure to compile variable template with
                    recursively defined partial specialization
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Casey at Carter dot net
  Target Milestone: ---

Created attachment 35604
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35604&action=edit
testcase.cpp

Both GCC 5.1.0 and 6.0 fail to compile this program:

template <class>
constexpr bool foo = false;
template <>
constexpr bool foo<int> = true;
template <class T, int N>
constexpr bool foo<T[N]> = foo<T>;

static_assert(foo<int>, "");
static_assert(!foo<double>, "");
static_assert(foo<int[3]>, "");
static_assert(!foo<double[3]>, "");
static_assert(foo<int[2][5][3]>, "");
static_assert(!foo<double[2][5][3]>, "");

int main() {}

5.1.0 doesn't seem to recognize that foo is a template-name in the definition
of the foo<T[N]> partial specialization:

prog.cc:6:33: error: expected primary-expression before '>' token
 constexpr bool foo<T[N]> = foo<T>;
                                 ^
prog.cc:6:34: error: expected primary-expression before ';' token
 constexpr bool foo<T[N]> = foo<T>;
                                  ^
prog.cc:6: confused by earlier errors, bailing out

6.0 20150522 at least tries to compile the recursion, but fails nonetheless:

prog.cc: In instantiation of 'constexpr const bool foo':
prog.cc:6:16:   recursively required from 'constexpr const bool foo'
prog.cc:6:16:   required from 'constexpr const bool foo'
prog.cc:10:15:   required from here
prog.cc:6:16: fatal error: template instantiation depth exceeds maximum of 900
(use -ftemplate-depth= to increase the maximum)
 constexpr bool foo<T[N]> = foo<T>;
                ^
compilation terminated.

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2015-08-05
                 CC|                            |jason at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed on trunk.

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Jason Merrill from comment #1)
> Fixed on trunk.

Oops, haven't checked in the fix yet.

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Wed Aug  5 17:56:14 2015
New Revision: 226642

URL: https://gcc.gnu.org/viewcvs?rev=226642&root=gcc&view=rev
Log:
        PR c++/66260
        PR c++/66596
        PR c++/66649
        PR c++/66923
        * pt.c (lookup_template_variable): Use NULL_TREE for type.
        (instantiate_template_1): Also set DECL_TI_ARGS based on
        the immediate parent.
        (tsubst_copy_and_build) [TEMPLATE_ID_EXPR]: Handle variable templates.
        (finish_template_variable): Add complain parm.
        * cp-tree.h: Adjust.

Added:
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ36.C
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ38.C
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ39.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ32.C
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ35.C

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Aug  6 04:10:01 2015
New Revision: 226657

URL: https://gcc.gnu.org/viewcvs?rev=226657&root=gcc&view=rev
Log:
        PR c++/66260
        PR c++/66596
        PR c++/66649
        PR c++/66923
        * pt.c (lookup_template_variable): Use NULL_TREE for type.
        (instantiate_template_1): Also set DECL_TI_ARGS based on
        the immediate parent.
        (tsubst_copy_and_build) [TEMPLATE_ID_EXPR]: Handle variable templates.
        (finish_template_variable): Add complain parm.
        * cp-tree.h: Adjust.

Added:
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ32.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ35.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ36.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ38.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ39.C
Modified:
    branches/gcc-5-branch/gcc/cp/ChangeLog
    branches/gcc-5-branch/gcc/cp/cp-tree.h
    branches/gcc-5-branch/gcc/cp/pt.c

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |5.3

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 5.3/6.

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Aug  6 14:26:18 2015
New Revision: 226676

URL: https://gcc.gnu.org/viewcvs?rev=226676&root=gcc&view=rev
Log:
        PR c++/67130
        PR c++/67131
        PR c++/66260
        * mangle.c (write_expression) [TEMPLATE_ID_EXPR]: Handle variable
        templates.
        * pt.c (tsubst_copy_and_build): Check for argument substitution
        failure.

Added:
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ42.C
    trunk/gcc/testsuite/g++.dg/cpp1y/var-templ43.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/mangle.c
    trunk/gcc/cp/pt.c

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Aug  6 14:28:26 2015
New Revision: 226677

URL: https://gcc.gnu.org/viewcvs?rev=226677&root=gcc&view=rev
Log:
        PR c++/67130
        PR c++/67131
        PR c++/66260
        * mangle.c (write_expression) [TEMPLATE_ID_EXPR]: Handle variable
        templates.
        * pt.c (tsubst_copy_and_build): Check for argument substitution
        failure.

Added:
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ42.C
    branches/gcc-5-branch/gcc/testsuite/g++.dg/cpp1y/var-templ43.C
Modified:
    branches/gcc-5-branch/gcc/cp/ChangeLog
    branches/gcc-5-branch/gcc/cp/mangle.c
    branches/gcc-5-branch/gcc/cp/pt.c

[Bug c++/66260] [C++14] Failure to compile variable template with recursively defined partial specialization

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66260

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Aug  6 18:45:05 2015
New Revision: 226696

URL: https://gcc.gnu.org/viewcvs?rev=226696&root=gcc&view=rev
Log:
        PR c++/67130
        PR c++/67131
        PR c++/66260
        * mangle.c (write_expression) [TEMPLATE_ID_EXPR]: Handle variable
        templates.
        * pt.c (tsubst_copy_and_build): Check for argument substitution
        failure.

Added:
    branches/c++-concepts/gcc/testsuite/g++.dg/cpp1y/var-templ42.C
    branches/c++-concepts/gcc/testsuite/g++.dg/cpp1y/var-templ43.C
Modified:
    branches/c++-concepts/gcc/cp/mangle.c
    branches/c++-concepts/gcc/cp/pt.c