66ae31eb30
The 23_containers/span/deduction.cc test was already passing, but only because I had previously implemented the original proposed resolution of 3255. As pointed out in 3255 that original P/R was incorrect because it broke construction from array xvalues. This reverts the incorrect part of 3255 (and adds tests for the case it broke), and implements the resolution of 3369 instead. * include/std/span (span(T (&)[N])): Use non-deduced context to prevent first parameter from interfering with class template argument deduction (LWG 3369). * testsuite/23_containers/span/deduction.cc: Add missing 'const'. * testsuite/23_containers/span/lwg3255.cc: Check for construction from rvalues.
85 lines
2.2 KiB
C++
85 lines
2.2 KiB
C++
// Copyright (C) 2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-options "-std=gnu++2a" }
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// { dg-do compile { target c++2a } }
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#include <span>
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template<typename T, int N, typename U>
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constexpr bool is_static_span(const U&)
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{
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return std::is_same_v<std::span<T, N>, U> && N != std::dynamic_extent;
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}
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template<typename T, typename U>
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constexpr bool is_dynamic_span(const U&)
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{
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return std::is_same_v<std::span<T>, U>;
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}
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struct Range
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{
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float* begin() const;
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float* end() const;
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};
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void
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test01()
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{
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const char c[] = "";
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int i[2]{};
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std::array<long, 3> a;
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Range r;
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std::span s1(c);
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static_assert( is_static_span<const char, 1>(s1) );
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std::span s2(i);
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static_assert( is_static_span<int, 2>(s2) );
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std::span s3(a);
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static_assert( is_static_span<long, 3>(s3) );
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std::span s4(const_cast<const std::array<long, 3>&>(a));
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static_assert( is_static_span<const long, 3>(s4) );
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std::span s5(std::begin(i), std::end(i));
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static_assert( is_dynamic_span<int>(s5) );
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std::span s6(std::cbegin(i), std::cend(i));
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static_assert( is_dynamic_span<const int>(s6) );
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std::span s7(r);
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static_assert( is_dynamic_span<float>(s7) );
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std::span s8(s1);
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static_assert( is_static_span<const char, 1>(s8) );
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std::span s9(s2);
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static_assert( is_static_span<int, 2>(s9) );
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std::span s10(const_cast<const std::span<int, 2>&>(s2));
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static_assert( is_static_span<int, 2>(s10) );
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std::span s11(s5);
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static_assert( is_dynamic_span<int>(s11) );
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std::span s12(const_cast<const std::span<int>&>(s5));
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static_assert( is_dynamic_span<int>(s12) );
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}
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