Unverified Commit 2513b790 authored by Joe Loser's avatar Joe Loser
Browse files

[libc++] Implement LWG3549: view_interface need not inherit from view_base

Implement LWG3549 by making `view_interface` not inherit from `view_base`. Types
are still views if they have a public and unambiguous derivation from
`view_interface`, so adjust the `enable_view` machinery as such to account for
that.

Differential Revision: https://reviews.llvm.org/D117714
parent 37d1d022
......@@ -91,7 +91,7 @@
`3544 <https://wg21.link/LWG3544>`__,"``format-arg-store::args`` is unintentionally not exposition-only","June 2021","","","|format|"
`3546 <https://wg21.link/LWG3546>`__,"``common_iterator``'s postfix-proxy is not quite right","June 2021","","","|ranges|"
`3548 <https://wg21.link/LWG3548>`__,"``shared_ptr`` construction from ``unique_ptr`` should move (not copy) the deleter","June 2021","",""
`3549 <https://wg21.link/LWG3549>`__,"``view_interface`` is overspecified to derive from ``view_base``","June 2021","","","|ranges|"
`3549 <https://wg21.link/LWG3549>`__,"``view_interface`` is overspecified to derive from ``view_base``","June 2021","|Complete|","14.0","|ranges|"
`3551 <https://wg21.link/LWG3551>`__,"``borrowed_{iterator,subrange}_t`` are overspecified","June 2021","","","|ranges|"
`3552 <https://wg21.link/LWG3552>`__,"Parallel specialized memory algorithms should require forward iterators","June 2021","",""
`3553 <https://wg21.link/LWG3553>`__,"Useless constraint in ``split_view::outer-iterator::value_type::begin()``","June 2021","","","|ranges|"
......
......@@ -12,6 +12,7 @@
#include <__config>
#include <concepts>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
......@@ -25,8 +26,17 @@ namespace ranges {
struct view_base { };
template<class _Derived>
requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
class view_interface;
template<class _Op, class _Yp>
requires is_convertible_v<_Op*, view_interface<_Yp>*>
void __is_derived_from_view_interface(const _Op*, const view_interface<_Yp>*);
template <class _Tp>
inline constexpr bool enable_view = derived_from<_Tp, view_base>;
inline constexpr bool enable_view = derived_from<_Tp, view_base> ||
requires { ranges::__is_derived_from_view_interface((_Tp*)nullptr, (_Tp*)nullptr); };
} // end namespace ranges
......
......@@ -18,7 +18,6 @@
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/empty.h>
#include <__ranges/enable_view.h>
#include <concepts>
#include <type_traits>
......@@ -40,7 +39,7 @@ void __implicitly_convert_to(type_identity_t<_Tp>) noexcept;
template<class _Derived>
requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
class view_interface : public view_base {
class view_interface {
_LIBCPP_HIDE_FROM_ABI
constexpr _Derived& __derived() noexcept {
static_assert(sizeof(_Derived) && derived_from<_Derived, view_interface> && view<_Derived>);
......
......@@ -79,6 +79,11 @@ struct MoveOnlyForwardRange : std::ranges::view_interface<MoveOnlyForwardRange>
};
static_assert(std::ranges::view<MoveOnlyForwardRange>);
struct MI : std::ranges::view_interface<InputRange>,
std::ranges::view_interface<MoveOnlyForwardRange> {
};
static_assert(!std::ranges::view<MI>);
struct EmptyIsTrue : std::ranges::view_interface<EmptyIsTrue> {
int buff[8] = {0, 1, 2, 3, 4, 5, 6, 7};
constexpr ForwardIter begin() const { return ForwardIter(const_cast<int*>(buff)); }
......@@ -300,6 +305,10 @@ constexpr bool testFrontBack() {
return true;
}
struct V1 : std::ranges::view_interface<V1> { };
struct V2 : std::ranges::view_interface<V2> { V1 base_; };
static_assert(sizeof(V2) == sizeof(V1));
int main(int, char**) {
testEmpty();
static_assert(testEmpty());
......
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