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Move associate's opstate into the get_state function #1831

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Move associate's opstate into the get_state function #1831

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105 changes: 50 additions & 55 deletions include/stdexec/__detail/__associate.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -147,59 +147,6 @@ namespace STDEXEC {
}
};

// NOTE: the spec declares this class template inside the get_state function
// but I couldn't get that to build with Clang 21 so I moved it out to
// this namespace-scoped template and __uglified all the symbols
template <class _Sender, class _Receiver>
struct __op_state {
using __associate_data_t = std::remove_cvref_t<__data_of<_Sender>>;
using __assoc_t = __associate_data_t::__assoc_t;
using __sender_ref_t = __associate_data_t::__sender_ref;

using __op_t = connect_result_t<typename __sender_ref_t::element_type, _Receiver>;

__assoc_t __assoc_;
union {
_Receiver __rcvr_;
__op_t __op_;
};

explicit __op_state(std::pair<__assoc_t, __sender_ref_t> __parts, _Receiver&& __rcvr)
: __assoc_(std::move(__parts.first)) {
if (__assoc_) {
::new ((void*) std::addressof(__op_))
__op_t(connect(std::move(*__parts.second), std::move(__rcvr)));
} else {
std::construct_at(std::addressof(__rcvr_), std::move(__rcvr));
}
}

explicit __op_state(__associate_data_t&& __ad, _Receiver&& __rcvr)
: __op_state(std::move(__ad).release(), std::move(__rcvr)) {
}

explicit __op_state(const __associate_data_t& __ad, _Receiver&& __rcvr)
requires __std::copy_constructible<__associate_data_t>
: __op_state(__associate_data_t(__ad).release(), std::move(__rcvr)) {
}

~__op_state() {
if (__assoc_) {
std::destroy_at(std::addressof(__op_));
} else {
std::destroy_at(std::addressof(__rcvr_));
}
}

void __run() noexcept {
if (__assoc_) {
STDEXEC::start(__op_);
} else {
STDEXEC::set_stopped(std::move(__rcvr_));
}
}
};

struct __associate_impl : __sexpr_defaults {
#if 0 // TODO: I don't know how to implement this correctly
static constexpr auto get_attrs = []<class _Child>(__ignore, const _Child& __child) noexcept {
Expand Down Expand Up @@ -231,8 +178,56 @@ namespace STDEXEC {
>) {
auto& [__tag, __data] = __self;

using op_state_t = __op_state<std::remove_cvref_t<_Self>, _Receiver>;
return op_state_t{__forward_like<_Self>(__data), std::move(__rcvr)};
using __associate_data_t = std::remove_cvref_t<decltype(__data)>;
using __assoc_t = __associate_data_t::__assoc_t;
using __sender_ref_t = __associate_data_t::__sender_ref;

using __op_t = connect_result_t<typename __sender_ref_t::element_type, _Receiver>;

struct __op_state {
__assoc_t __assoc_;
union {
_Receiver* __rcvr_;
__op_t __op_;
};

explicit __op_state(std::pair<__assoc_t, __sender_ref_t> __parts, _Receiver& __rcvr)
: __assoc_(std::move(__parts.first)) {
if (__assoc_) {
::new ((void*) std::addressof(__op_))
__op_t(STDEXEC::connect(std::move(*__parts.second), std::move(__rcvr)));
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@ispeters ispeters Feb 11, 2026

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The spec doesn't fully-qualify this call to connect; it's required in stdexec to avoid an ambiguity with (I think) a member connect that's in scope here. I'm wondering if basic-sender has the same ambiguity as __sexpr_defaults.

} else {
__rcvr_ = std::addressof(__rcvr);
}
}

explicit __op_state(__associate_data_t&& __ad, _Receiver& __rcvr)
: __op_state(std::move(__ad).release(), __rcvr) {
}

explicit __op_state(const __associate_data_t& __ad, _Receiver& __rcvr)
requires __std::copy_constructible<__associate_data_t>
: __op_state(__associate_data_t(__ad).release(), __rcvr) {
}

__op_state(__op_state&&) = delete;

~__op_state() {
if (__assoc_) {
std::destroy_at(std::addressof(__op_));
}
}

void __run() noexcept {
if (__assoc_) {
STDEXEC::start(__op_);
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@ispeters ispeters Feb 11, 2026

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This call to start has the same problem as the above call to connect.

} else {
set_stopped(std::move(*__rcvr_));
}
}
};

return __op_state{__forward_like<_Self>(__data), __rcvr};
};

static constexpr auto start = [](auto& __state) noexcept -> void {
Expand Down