While it's not necessary to qualify calls to `declval` it makes error messages very crypric if the declaration isn't reachable anymore
For example:
```
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:53:66: error: no type named 'type' in 'std::common_type<long, long>'
typedef chrono::duration<typename common_type<_Rep1, _Rep2>::type,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__type_traits/common_type.h:107:14: note: in instantiation of template class 'std::common_type<std::chrono::duration<long, std::ratio<3600, 1>>, std::chrono::duration<long, std::ratio<3600, 1>>>' requested here
: public common_type<_Tp, _Tp> {};
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:279:58: note: in instantiation of template class 'std::common_type<std::chrono::duration<long, std::ratio<3600, 1>>>' requested here
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator+() const {return typename common_type<duration>::type(*this);}
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:308:54: note: in instantiation of template class 'std::chrono::duration<long, std::ratio<3600, 1>>' requested here
typedef duration< int, ratio_multiply<ratio<24>, hours::period>> days;
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:280:81: error: no type named 'type' in 'std::common_type<std::chrono::duration<long, std::ratio<3600, 1>>>'
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator-() const {return typename common_type<duration>::type(-__rep_);}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:308:54: note: in instantiation of template class 'std::chrono::duration<long, std::ratio<3600, 1>>' requested here
typedef duration< int, ratio_multiply<ratio<24>, hours::period>> days;
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:53:66: error: no type named 'type' in 'std::common_type<int, int>'
typedef chrono::duration<typename common_type<_Rep1, _Rep2>::type,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__type_traits/common_type.h:107:14: note: in instantiation of template class 'std::common_type<std::chrono::duration<int, std::ratio<86400, 1>>, std::chrono::duration<int, std::ratio<86400, 1>>>' requested here
: public common_type<_Tp, _Tp> {};
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:279:58: note: in instantiation of template class 'std::common_type<std::chrono::duration<int, std::ratio<86400, 1>>>' requested here
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator+() const {return typename common_type<duration>::type(*this);}
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__chrono/duration.h:309:55: note: in instantiation of template class 'std::chrono::duration<int, std::ratio<86400, 1>>' requested here
typedef duration< int, ratio_multiply<ratio<7>, days::period>> weeks;
^
19 similar errors omitted
```
changes with qualification added to:
```
While building module 'std' imported from /home/nikolask/llvm-projects/libcxx/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/common_type.pass.cpp:13:
In file included from <module-includes>:17:
In file included from /home/nikolask/llvm-projects/libcxx/build/include/c++/v1/math.h:309:
In file included from /home/nikolask/llvm-projects/libcxx/build/include/c++/v1/limits:107:
In file included from /home/nikolask/llvm-projects/libcxx/build/include/c++/v1/type_traits:432:
In file included from /home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__type_traits/common_reference.h:13:
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__type_traits/common_type.h:28:43: error: declaration of 'declval' must be imported from module 'std.utility.__utility.declval' before it is required
using __cond_type = decltype(false ? std::declval<_Tp>() : std::declval<_Up>());
^
/home/nikolask/llvm-projects/libcxx/build/include/c++/v1/__utility/declval.h:30:34: note: declaration here is not visible
decltype(std::__declval<_Tp>(0)) declval() _NOEXCEPT;
^
/home/nikolask/llvm-projects/libcxx/libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/common_type.pass.cpp:13:10: fatal error: could not build module 'std'
#include <functional>
~~~~~~~~^
2 errors generated.
```
Reviewed By: ldionne, Mordante, #libc
Spies: libcxx-commits
Differential Revision: https://reviews.llvm.org/D130854
126 lines
3.3 KiB
C++
126 lines
3.3 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___MEMORY_RANGES_CONSTRUCT_AT_H
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#define _LIBCPP___MEMORY_RANGES_CONSTRUCT_AT_H
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#include <__concepts/destructible.h>
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#include <__config>
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#include <__iterator/incrementable_traits.h>
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#include <__iterator/readable_traits.h>
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#include <__memory/concepts.h>
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#include <__memory/construct_at.h>
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#include <__ranges/access.h>
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#include <__ranges/concepts.h>
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#include <__ranges/dangling.h>
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#include <__utility/declval.h>
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#include <__utility/forward.h>
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#include <__utility/move.h>
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#include <new>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 17
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namespace ranges {
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// construct_at
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namespace __construct_at {
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struct __fn {
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template<class _Tp, class... _Args, class = decltype(
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::new (std::declval<void*>()) _Tp(std::declval<_Args>()...)
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)>
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_LIBCPP_HIDE_FROM_ABI
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constexpr _Tp* operator()(_Tp* __location, _Args&& ...__args) const {
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return _VSTD::construct_at(__location, _VSTD::forward<_Args>(__args)...);
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}
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};
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} // namespace __construct_at
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inline namespace __cpo {
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inline constexpr auto construct_at = __construct_at::__fn{};
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} // namespace __cpo
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// destroy_at
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namespace __destroy_at {
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struct __fn {
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template <destructible _Tp>
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_LIBCPP_HIDE_FROM_ABI
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constexpr void operator()(_Tp* __location) const noexcept {
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_VSTD::destroy_at(__location);
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}
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};
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} // namespace __destroy_at
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inline namespace __cpo {
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inline constexpr auto destroy_at = __destroy_at::__fn{};
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} // namespace __cpo
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// destroy
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namespace __destroy {
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struct __fn {
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template <__nothrow_input_iterator _InputIterator, __nothrow_sentinel_for<_InputIterator> _Sentinel>
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requires destructible<iter_value_t<_InputIterator>>
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_LIBCPP_HIDE_FROM_ABI
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constexpr _InputIterator operator()(_InputIterator __first, _Sentinel __last) const noexcept {
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return _VSTD::__destroy(_VSTD::move(__first), _VSTD::move(__last));
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}
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template <__nothrow_input_range _InputRange>
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requires destructible<range_value_t<_InputRange>>
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_LIBCPP_HIDE_FROM_ABI
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constexpr borrowed_iterator_t<_InputRange> operator()(_InputRange&& __range) const noexcept {
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return (*this)(ranges::begin(__range), ranges::end(__range));
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}
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};
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} // namespace __destroy
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inline namespace __cpo {
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inline constexpr auto destroy = __destroy::__fn{};
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} // namespace __cpo
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// destroy_n
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namespace __destroy_n {
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struct __fn {
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template <__nothrow_input_iterator _InputIterator>
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requires destructible<iter_value_t<_InputIterator>>
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_LIBCPP_HIDE_FROM_ABI
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constexpr _InputIterator operator()(_InputIterator __first, iter_difference_t<_InputIterator> __n) const noexcept {
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return _VSTD::destroy_n(_VSTD::move(__first), __n);
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}
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};
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} // namespace __destroy_n
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inline namespace __cpo {
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inline constexpr auto destroy_n = __destroy_n::__fn{};
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} // namespace __cpo
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} // namespace ranges
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#endif // _LIBCPP_STD_VER > 17
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___MEMORY_RANGES_CONSTRUCT_AT_H
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