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libstdc++: LWG 3325 Constrain return type of transformation function for transform_view

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libstdc++-v3/ChangeLog:

	LWG 3325 Constrain return type of transformation function for
	transform_view
	* include/std/ranges (transform_view): Constrain the return type of the
	transformation function as per LWG 3325.
	* testsuite/std/ranges/adaptors/lwg3325_neg.cc: New test.
This commit is contained in:
Patrick Palka 2020-02-24 16:21:55 -05:00
parent 55c4b3f486
commit ec15da7c33
3 changed files with 43 additions and 0 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,5 +1,11 @@
2020-02-25 Patrick Palka <ppalka@redhat.com>
LWG 3325 Constrain return type of transformation function for
transform_view
* include/std/ranges (transform_view): Constrain the return type of the
transformation function as per LWG 3325.
* testsuite/std/ranges/adaptors/lwg3325_neg.cc: New test.
LWG 3313 join_view::_Iterator::operator-- is incorrectly constrained
* include/std/ranges (join_view::_Iterator::operator--): Require that
range_reference_t<_Base> models common_range.

2
libstdc++-v3/include/std/ranges
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@ -1540,6 +1540,8 @@ namespace views
template<input_range _Vp, copy_constructible _Fp>
requires view<_Vp> && is_object_v<_Fp>
&& regular_invocable<_Fp&, range_reference_t<_Vp>>
&& std::__detail::__can_reference<invoke_result_t<_Fp&,
range_reference_t<_Vp>>>
class transform_view : public view_interface<transform_view<_Vp, _Fp>>
{
private:

35
libstdc++-v3/testsuite/std/ranges/adaptors/lwg3325_neg.cc Normal file
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@ -0,0 +1,35 @@
// Copyright (C) 2020 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/>.
// { dg-options "-std=gnu++2a" }
// { dg-do compile { target c++2a } }
#include <ranges>
namespace ranges = std::ranges;
namespace views = std::views;
void
test01()
{
auto f = [] (int x) { };
int x[] = {1};
auto v = ranges::transform_view{x, f}; // { dg-error "deduction failed|no match" }
}
// { dg-prune-output "constraint failure" }
// { dg-prune-output "in requirements" }