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| author | redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4> | 2017-07-14 19:13:49 +0000 |
|---|---|---|
| committer | redi <redi@138bc75d-0d04-0410-961f-82ee72b054a4> | 2017-07-14 19:13:49 +0000 |
| commit | c33389c59b1e0f0805f63e44425849ae2e8c99fe (patch) | |
| tree | 98d5298be92e1ed9201dbc5347653e1c5836120b | |
| parent | 1e84d0ef89e03be49e4c364c109a9aa160f93a9b (diff) | |
| download | gcc-c33389c59b1e0f0805f63e44425849ae2e8c99fe.tar.gz | |
Constrain std::variant constructor for class template argument deduction
2017-07-14 Jason Merrill <jason@redhat.com>
Jonathan Wakely <jwakely@redhat.com>
* include/std/variant (variant::variant(_Tp&&)): Constrain to remove
the constructor for empty variants from the candidate functions
during class template argument deduction.
* testsuite/20_util/variant/deduction.cc: New.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@250213 138bc75d-0d04-0410-961f-82ee72b054a4
| -rw-r--r-- | libstdc++-v3/ChangeLog | 8 | ||||
| -rw-r--r-- | libstdc++-v3/include/std/variant | 1 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/20_util/variant/deduction.cc | 39 |
3 files changed, 48 insertions, 0 deletions
diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog index 04a1c7f7aee..70d1944490e 100644 --- a/libstdc++-v3/ChangeLog +++ b/libstdc++-v3/ChangeLog @@ -1,3 +1,11 @@ +2017-07-14 Jason Merrill <jason@redhat.com> + Jonathan Wakely <jwakely@redhat.com> + + * include/std/variant (variant::variant(_Tp&&)): Constrain to remove + the constructor for empty variants from the candidate functions + during class template argument deduction. + * testsuite/20_util/variant/deduction.cc: New. + 2017-07-11 Jonathan Wakely <jwakely@redhat.com> * doc/xml/faq.xml: Update several old entries. Improve diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant index 06646f6b798..23db6d27529 100644 --- a/libstdc++-v3/include/std/variant +++ b/libstdc++-v3/include/std/variant @@ -1101,6 +1101,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Tp, typename = enable_if_t<!is_same_v<decay_t<_Tp>, variant>>, + typename = enable_if_t<(sizeof...(_Types)>0)>, typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>> && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>>> constexpr diff --git a/libstdc++-v3/testsuite/20_util/variant/deduction.cc b/libstdc++-v3/testsuite/20_util/variant/deduction.cc new file mode 100644 index 00000000000..33bc9d2a40e --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/variant/deduction.cc @@ -0,0 +1,39 @@ +// { dg-options "-std=gnu++17" } +// { dg-do compile { target c++1z } } + +// Copyright (C) 2017 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +#include <variant> + +template<typename T, typename U> struct require_same; +template<typename T> struct require_same<T, T> { using type = void; }; + +template<typename T, typename U> + typename require_same<T, U>::type + check_type(U&) { } + +void +test01() +{ + std::variant<int, double> x(3); + + std::variant copy = x; + check_type<decltype(x)>(copy); + std::variant move = std::move(x); + check_type<decltype(x)>(move); +} |