[v3 PATCH] PR libstdc++/66338

[Ville Voutilainen <ville dot voutilainen at gmail dot com>]

Tested on Linux-PPC64. The idea here is to get the constructor templates
to step out of the way if what they are dealing with will be handled by
a special member function, like the copy constructor. Doing so properly
fixes the bug at hand and likely other similar cases, too. The problem
in getting the templates out of the way is that none of their is_constructible
or is_convertible checks should be evaluated at all, but since we have
these handy pseudo-concepts in place, doing that is merely a matter
of adjusting the shortcut alias for one of those pseudo-concepts.

2016-05-24  Ville Voutilainen  <ville.voutilainen@gmail.com>

    PR libstdc++/66338
    * include/std/tuple (_TMC): Add a check for _NotSameTuple.
    * include/std/tuple (tuple(_UElements&&...)): Remove the separate
    check for _NotSameTuple.
    * testsuite/20_util/tuple/cons/66338.cc: New.

Attachment: 66338.diff
Description: Text document