[Bug c++/67844] New: Cannot make tuple of class with template constructor

[Bug c++/67844] New: Cannot make tuple of class with template constructor

[rbock at eudoxos dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

            Bug ID: 67844
           Summary: Cannot make tuple of class with template constructor
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rbock at eudoxos dot de
  Target Milestone: ---

Created attachment 36443
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36443&action=edit
struct with template constructor, instantiate, try to make_tuple from the
instance

If the constructor of a class is a template (see attached code), trying to call
make_tuple on an instance of this class fails to compile with g++-6.0.0.

The first error in the output is 

include/c++/6.0.0/type_traits:138:12: error: invalid use of incomplete type
‘struct std::is_convertible<const std::tuple<A>&, A>’

g++-4.9 as well as clang-3.[456] compile the code just fine.
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Subject: [Bug libstdc++/67843] experimental/filesystem/iterators/directory_iterator.cc fails on armv5t
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg843

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm unable to build an armv7 toolchain, it keeps failing with an ICE, so I'll
need more information to do anything about this.

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-10-04
                 CC|                            |ville at gcc dot gnu.org
   Target Milestone|---                         |6.0
            Summary|Cannot make tuple of class  |[6 Regression] Cannot make
                   |with template constructor   |tuple of class with
                   |                            |template constructor
     Ever confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Ville, I haven't looked into what's happening here yet, do you see anything
obvious?

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |ville.voutilainen at gmail dot com
           Assignee|unassigned at gcc dot gnu.org      |ville.voutilainen at gmail dot com

--- Comment #2 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
To the extent anything in this area is obvious, yes. :) The check for
non-nested tuple ends up in infinite meta-recursion because A is constructible
from the tuple itself. I think that can be tackled by adding an is_same
check to _TNTC so that the converting templates that take a tuple 
outright reject tuples that are the same as the tuple itself. Fixing...

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

--- Comment #3 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Patch available https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00358.html

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[rbock at eudoxos dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

--- Comment #4 from Roland B <rbock at eudoxos dot de> ---
(In reply to Ville Voutilainen from comment #3)
> Patch available https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00358.html

Works for me (sqlpp11, develop branch).

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[ville at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

--- Comment #5 from ville at gcc dot gnu.org ---
Author: ville
Date: Mon Oct  5 09:57:20 2015
New Revision: 228468

URL: https://gcc.gnu.org/viewcvs?rev=228468&root=gcc&view=rev
Log:
2015-10-05  Ville Voutilainen  <ville.voutilainen@gmail.com>

        PR 67844.
        * include/std/tuple (_TC::_NonNestedTuple): Eagerly reject
        conversions from tuple types same as the target tuple.
        * testsuite/20_util/tuple/67844.cc: New.
        * testsuite/20_util/tuple/cons/nested_tuple_construct.cc: Add
        a missing copyright header.

Added:
    trunk/libstdc++-v3/testsuite/20_util/tuple/67844.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/std/tuple
    trunk/libstdc++-v3/testsuite/20_util/tuple/cons/nested_tuple_construct.cc

[Bug c++/67844] [6 Regression] Cannot make tuple of class with template constructor

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67844

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
Fixed on trunk.