On Thu, 11 Jan 2024 at 00:26, Patrick Palka <ppa...@redhat.com> wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
OK. Nice to see explicit object functions landing in the library so soon!
>
> -- >8 --
>
> This simplifies the operator() of the _Pipe and _Partial range adaptor
> closure objects using C++23 deducing this, allowing us to condense
> multiple operator() overloads into one.
>
> The new __like_t alias template is similar to the expositional one from
> P0847R6, except it's implemented in terms of forward_like instead of vice
> versa, and thus ours always yields a reference, so e.g. __like_t<A, char>
> is char&&. This shouldn't make a difference in practice, I think..
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/move.h (__like_t): Define.
> * include/std/ranges (views::__adaptor::Partial::operator()):
> Implement using C++23 deducing this when available.
> (views::__adaptor::_Pipe::operator()): Likewise.
> * testsuite/std/ranges/adaptors/100577.cc: Adjust testcase to
> accept "no match for call" errors issued in C++23 mode instead
> of "use of deleted function".
> * testsuite/std/ranges/adaptors/lazy_split_neg.cc: Likewise.
> ---
> libstdc++-v3/include/bits/move.h | 3 ++
> libstdc++-v3/include/std/ranges | 37 ++++++++++++++++++-
> .../testsuite/std/ranges/adaptors/100577.cc | 18 ++++-----
> .../std/ranges/adaptors/lazy_split_neg.cc | 2 +-
> 4 files changed, 48 insertions(+), 12 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/move.h
> b/libstdc++-v3/include/bits/move.h
> index 4e741bcdeb0..bb200c95964 100644
> --- a/libstdc++-v3/include/bits/move.h
> +++ b/libstdc++-v3/include/bits/move.h
> @@ -110,6 +110,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return static_cast<_Up&>(__x);
> }
> }
> +
> + template<typename _Tp, typename _Up>
> + using __like_t = decltype(std::forward_like<_Tp>(std::declval<_Up>()));
> #endif
>
> /**
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index 0734daa42bf..8d2649cf5b9 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -1016,7 +1016,19 @@ namespace views::__adaptor
>
> // Invoke _Adaptor with arguments __r, _M_args... according to the
> // value category of this _Partial object.
> - // TODO: use explicit object functions ("deducing this").
> +#if __cpp_explicit_this_parameter
> + template<typename _Self, typename _Range>
> + requires __adaptor_invocable<_Adaptor, _Range, __like_t<_Self,
> _Args>...>
> + constexpr auto
> + operator()(this _Self&& __self, _Range&& __r)
> + {
> + auto __forwarder = [&__r] (auto&&... __args) {
> + return _Adaptor{}(std::forward<_Range>(__r),
> + std::forward<decltype(__args)>(__args)...);
> + };
> + return std::apply(__forwarder, std::forward<_Self>(__self)._M_args);
> + }
> +#else
> template<typename _Range>
> requires __adaptor_invocable<_Adaptor, _Range, const _Args&...>
> constexpr auto
> @@ -1042,6 +1054,7 @@ namespace views::__adaptor
> template<typename _Range>
> constexpr auto
> operator()(_Range&& __r) const && = delete;
> +#endif
> };
>
> // A lightweight specialization of the above primary template for
> @@ -1058,6 +1071,14 @@ namespace views::__adaptor
> : _M_arg(std::forward<_Tp>(__arg))
> { }
>
> +#if __cpp_explicit_this_parameter
> + template<typename _Self, typename _Range>
> + requires __adaptor_invocable<_Adaptor, _Range, __like_t<_Self, _Arg>>
> + constexpr auto
> + operator()(this _Self&& __self, _Range&& __r)
> + { return _Adaptor{}(std::forward<_Range>(__r),
> + std::forward<_Self>(__self)._M_arg); }
> +#else
> template<typename _Range>
> requires __adaptor_invocable<_Adaptor, _Range, const _Arg&>
> constexpr auto
> @@ -1073,6 +1094,7 @@ namespace views::__adaptor
> template<typename _Range>
> constexpr auto
> operator()(_Range&& __r) const && = delete;
> +#endif
> };
>
> // Partial specialization of the primary template for the case where the
> extra
> @@ -1154,7 +1176,17 @@ namespace views::__adaptor
>
> // Invoke _M_rhs(_M_lhs(__r)) according to the value category of this
> // range adaptor closure object.
> - // TODO: use explicit object functions ("deducing this").
> +#if __cpp_explicit_this_parameter
> + template<typename _Self, typename _Range>
> + requires __pipe_invocable<__like_t<_Self, _Lhs>, __like_t<_Self,
> _Rhs>, _Range>
> + constexpr auto
> + operator()(this _Self&& __self, _Range&& __r)
> + {
> + return (std::forward<_Self>(__self)._M_rhs
> + (std::forward<_Self>(__self)._M_lhs
> + (std::forward<_Range>(__r))));
> + }
> +#else
> template<typename _Range>
> requires __pipe_invocable<const _Lhs&, const _Rhs&, _Range>
> constexpr auto
> @@ -1170,6 +1202,7 @@ namespace views::__adaptor
> template<typename _Range>
> constexpr auto
> operator()(_Range&& __r) const && = delete;
> +#endif
> };
>
> // A partial specialization of the above primary template for the case
> where
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> index 69072d69fec..3a52f5b4ce0 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/100577.cc
> @@ -98,28 +98,28 @@ test02()
> (views::take_while(badarg) | views::all)(x); // { dg-error "no match" }
> (views::drop_while(badarg) | views::all)(x); // { dg-error "no match" }
>
> - // In practice, range adaptor closures with non-simple operator() are
> + // In C++20 mode, range adaptor closures with non-simple operator() are
> // implemented using a fallback deleted overload, so when a call is
> // ill-formed overload resolution succeeds but selects the deleted overload
> // (but only when the closure is invoked as an rvalue).
> - views::lazy_split(badarg)(x); // { dg-error "deleted function" }
> - (views::lazy_split(badarg) | views::all)(x); // { dg-error "deleted
> function" }
> + views::lazy_split(badarg)(x); // { dg-error "deleted function|no match" }
> + (views::lazy_split(badarg) | views::all)(x); // { dg-error "deleted
> function|no match" }
> auto a0 = views::lazy_split(badarg);
> a0(x); // { dg-error "no match" };
> auto a1 = a0 | views::all;
> a1(x); // { dg-error "no match" }
>
> - views::split(badarg)(x); // { dg-error "deleted function" }
> - (views::split(badarg) | views::all)(x); // { dg-error "deleted function" }
> + views::split(badarg)(x); // { dg-error "deleted function|no match" }
> + (views::split(badarg) | views::all)(x); // { dg-error "deleted function|no
> match" }
> auto a0a = views::split(badarg);
> a0a(x); // { dg-error "no match" };
> auto a1a = a0a | views::all;
> a1a(x); // { dg-error "no match" }
>
> - views::take(badarg)(x); // { dg-error "deleted" }
> - views::drop(badarg)(x); // { dg-error "deleted" }
> - (views::take(badarg) | views::all)(x); // { dg-error "deleted" }
> - (views::drop(badarg) | views::all)(x); // { dg-error "deleted" }
> + views::take(badarg)(x); // { dg-error "deleted|no match" }
> + views::drop(badarg)(x); // { dg-error "deleted|no match" }
> + (views::take(badarg) | views::all)(x); // { dg-error "deleted|no match" }
> + (views::drop(badarg) | views::all)(x); // { dg-error "deleted|no match" }
> }
>
> void
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split_neg.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split_neg.cc
> index 683ea76da07..85632759fcc 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split_neg.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/lazy_split_neg.cc
> @@ -38,7 +38,7 @@ test02()
> {
> using namespace std::literals;
> auto x = "the quick brown fox"sv;
> - auto v1 = views::lazy_split(std::initializer_list<char>{' ', ' '})(x); //
> { dg-error "deleted" }
> + auto v1 = views::lazy_split(std::initializer_list<char>{' ', ' '})(x); //
> { dg-error "deleted|no match" }
> auto v2 = x | views::lazy_split(std::initializer_list<char>{' ', ' '}); //
> { dg-error "no match" }
> }
>
> --
> 2.43.0.283.ga54a84b333
>
