main

HHui Xie[libc++] fix views::all hard error on lvalue move only views instead of SFINAE

20869c5b创建于 2022年6月22日历史提交

文件	最后提交记录	最后更新时间
range.owning.view	[libc++] Replace _LIBCPP_HAS_NO_CONCEPTS with _LIBCPP_STD_VER > 17. NFCI. All supported compilers that support C++20 now support concepts. So, remove _LIB_LIBCPP_HAS_NO_CONCEPTS in favor of _LIBCPP_STD_VER > 17. Similarly in the tests, remove // UNSUPPORTED: libcpp-no-concepts. Differential Revision: https://reviews.llvm.org/D121528	4 年前
range.ref.view	[libc++] Replace _LIBCPP_HAS_NO_CONCEPTS with _LIBCPP_STD_VER > 17. NFCI. All supported compilers that support C++20 now support concepts. So, remove _LIB_LIBCPP_HAS_NO_CONCEPTS in favor of _LIBCPP_STD_VER > 17. Similarly in the tests, remove // UNSUPPORTED: libcpp-no-concepts. Differential Revision: https://reviews.llvm.org/D121528	4 年前
all.pass.cpp	[libc++] fix views::all hard error on lvalue move only views instead of SFINAE For an lvalue reference to a move only view x, views::all(x) gives hard error because the expression inside noexcept is not well formed and it is not SFINAE friendly. Given a move only view type V, and a concept template <class R> concept can_all = requires { std::views::all(std::declval<R>()); }; The expression can_all<V&> returns libstdc++: false msvc stl : false libc++ : error: static_cast from 'V' to 'typename decay<decltype((std::forward<V &>(__t)))>::type' (aka 'V') uses deleted function noexcept(noexcept(_LIBCPP_AUTO_CAST(std::forward<_Tp>(__t)))) The standard spec has its own problem, the spec says it is expression equivalent to decay-copy(E) but the spec of decay-copy does not have any constraint, which means the expression decay-copy(declval<V&>()) is well-formed and the concept can_all<V&> should return true and should error when instantiating the function body of decay-copy. This is clearly wrong behaviour in the spec and we will probably create an LWG issue. But the libc++'s behaviour is clearly not correct. The noexcept is an "extension" in libc++ which is not in the spec, but the expression inside noexpect triggers hard error, which is not right. Reviewed By: #libc, ldionne, var-const Differential Revision: https://reviews.llvm.org/D128281	3 年前
all_t.compile.pass.cpp	[libc++] Replace _LIBCPP_HAS_NO_CONCEPTS with _LIBCPP_STD_VER > 17. NFCI. All supported compilers that support C++20 now support concepts. So, remove _LIB_LIBCPP_HAS_NO_CONCEPTS in favor of _LIBCPP_STD_VER > 17. Similarly in the tests, remove // UNSUPPORTED: libcpp-no-concepts. Differential Revision: https://reviews.llvm.org/D121528	4 年前