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Add stdexec::spawn
This diff adds `stdexec::spawn` and its tests.
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+499
-21
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6 files changed

+499
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‎include/stdexec/__detail/__spawn.hpp‎

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/*
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* Copyright (c) 2025 Ian Petersen
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* Copyright (c) 2025 NVIDIA Corporation
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*
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* Licensed under the Apache License Version 2.0 with LLVM Exceptions
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* https://llvm.org/LICENSE.txt
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include "__execution_fwd.hpp"
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#include "__concepts.hpp"
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#include "__env.hpp"
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#include "__queries.hpp"
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#include "__receivers.hpp"
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#include "__scope_concepts.hpp"
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#include "__senders_core.hpp"
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#include "__type_traits.hpp"
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#include "__write_env.hpp"
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#include <memory>
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#include <type_traits>
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#include <utility>
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namespace stdexec {
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/////////////////////////////////////////////////////////////////////////////
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// [exec.spawn]
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namespace __spawn {
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struct __spawn_state_base {
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__spawn_state_base() = default;
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__spawn_state_base(__spawn_state_base&&) = delete;
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virtual void __complete() noexcept = 0;
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protected:
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~__spawn_state_base() = default;
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};
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struct __spawn_receiver {
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using receiver_concept = receiver_t;
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__spawn_state_base* __state_;
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void set_value() && noexcept {
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__state_->__complete();
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}
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void set_stopped() && noexcept {
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__state_->__complete();
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}
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};
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template <class _Alloc, scope_token _Token, sender _Sender>
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struct __spawn_state final : __spawn_state_base {
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using __op_t = connect_result_t<_Sender, __spawn_receiver>;
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__spawn_state(_Alloc __alloc, _Sender&& __sndr, _Token __token)
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: __alloc_(std::move(__alloc))
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, __op_(connect(std::move(__sndr), __spawn_receiver(this)))
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, __assoc_(__token.try_associate()) {
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}
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void __complete() noexcept override {
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[[maybe_unused]]
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auto assoc = std::move(__assoc_);
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{
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using traits = std::allocator_traits<_Alloc>::template rebind_traits<__spawn_state>;
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typename traits::allocator_type alloc(__alloc_);
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traits::destroy(alloc, this);
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traits::deallocate(alloc, this, 1);
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}
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}
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void __run() noexcept {
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if (__assoc_) {
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start(__op_);
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} else {
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__complete();
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}
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}
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private:
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using __assoc_t = std::remove_cvref_t<decltype(__declval<_Token&>().try_associate())>;
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_Alloc __alloc_;
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__op_t __op_;
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__assoc_t __assoc_;
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};
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struct __choose_alloc_fn {
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template <class _Env, class _SenderEnv>
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requires __callable<get_allocator_t, _Env>
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auto operator()(const _Env& __env, const _SenderEnv&) const {
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return get_allocator(__env);
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}
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template <class _Env, class _SenderEnv>
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requires(!__callable<get_allocator_t, const _Env&>)
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&& __callable<get_allocator_t, const _SenderEnv&>
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auto operator()(const _Env&, const _SenderEnv& __env) const {
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return get_allocator(__env);
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}
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template <class _Env, class _SenderEnv>
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requires(!__callable<get_allocator_t, const _Env&>)
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&& (!__callable<get_allocator_t, const _SenderEnv&>)
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std::allocator<void> operator()(const _Env&, const _SenderEnv&) const {
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return std::allocator<void>();
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}
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};
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inline constexpr __choose_alloc_fn __choose_alloc{};
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struct __choose_senv_fn {
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template <class _Env, class _SenderEnv>
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requires __callable<get_allocator_t, const _Env&>
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const _Env& operator()(const _Env& __env, const _SenderEnv&) const {
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return __env;
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}
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template <class _Env, class _SenderEnv>
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requires(!__callable<get_allocator_t, const _Env&>)
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&& __callable<get_allocator_t, const _SenderEnv&>
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auto operator()(const _Env& __env, const _SenderEnv& __sndrEnv) const {
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return __env::__join(prop(get_allocator, get_allocator(__sndrEnv)), __env);
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}
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template <class _Env, class _SenderEnv>
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requires(!__callable<get_allocator_t, const _Env&>)
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&& (!__callable<get_allocator_t, const _SenderEnv&>)
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const _Env& operator()(const _Env& __env, const _SenderEnv&) const {
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return __env;
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}
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};
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inline constexpr __choose_senv_fn __choose_senv{};
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struct spawn_t {
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template <sender _Sender, scope_token _Token>
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void operator()(_Sender&& __sndr, _Token&& __tkn) const {
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return (*this)(static_cast<_Sender&&>(__sndr), static_cast<_Token&&>(__tkn), env<>{});
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}
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template <sender _Sender, scope_token _Token, class _Env>
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void operator()(_Sender&& __sndr, _Token&& __tkn, _Env&& __env) const {
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auto wrappedSender = __tkn.wrap(static_cast<_Sender&&>(__sndr));
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auto sndrEnv = get_env(wrappedSender);
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using raw_alloc = decltype(__choose_alloc(__env, sndrEnv));
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auto senderWithEnv = write_env(std::move(wrappedSender), __choose_senv(__env, sndrEnv));
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using spawn_state_t =
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__spawn_state<raw_alloc, std::remove_cvref_t<_Token>, decltype(senderWithEnv)>;
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using traits = std::allocator_traits<raw_alloc>::template rebind_traits<spawn_state_t>;
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typename traits::allocator_type alloc(__choose_alloc(__env, sndrEnv));
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auto* op = traits::allocate(alloc, 1);
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try {
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traits::construct(
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alloc, op, alloc, std::move(senderWithEnv), static_cast<_Token&&>(__tkn));
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} catch (...) {
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traits::deallocate(alloc, op, 1);
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throw;
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}
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op->__run();
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}
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};
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} // namespace __spawn
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using __spawn::spawn_t;
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inline constexpr spawn_t spawn{};
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} // namespace stdexec

‎include/stdexec/execution.hpp‎

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#include "__detail/__scope_concepts.hpp" // IWYU pragma: export
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#include "__detail/__senders.hpp" // IWYU pragma: export
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#include "__detail/__sender_adaptor_closure.hpp" // IWYU pragma: export
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#include "__detail/__spawn.hpp" // IWYU pragma: export
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#include "__detail/__split.hpp" // IWYU pragma: export
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#include "__detail/__start_detached.hpp" // IWYU pragma: export
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#include "__detail/__starts_on.hpp" // IWYU pragma: export

‎test/CMakeLists.txt‎

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stdexec/algos/adaptors/test_stop_when.cpp
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stdexec/algos/consumers/test_start_detached.cpp
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stdexec/algos/consumers/test_sync_wait.cpp
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stdexec/algos/consumers/test_spawn.cpp
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stdexec/algos/other/test_execute.cpp
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stdexec/detail/test_completion_signatures.cpp
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stdexec/detail/test_utility.cpp

‎test/stdexec/algos/adaptors/test_associate.cpp‎

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#include <catch2/catch.hpp>
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#include <stdexec/execution.hpp>
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#include <test_common/receivers.hpp>
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#include <test_common/scope_tokens.hpp>
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#include <concepts>
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#include <memory>
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namespace ex = stdexec;
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namespace {
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struct null_token {
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struct assoc {
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constexpr operator bool() const noexcept {
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return true;
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}
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constexpr assoc try_associate() const noexcept {
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return {};
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}
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};
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template <ex::sender Sender>
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constexpr Sender&& wrap(Sender&& sndr) const noexcept {
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return std::forward<Sender>(sndr);
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}
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constexpr assoc try_associate() const noexcept {
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return {};
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}
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};
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TEST_CASE("associate returns a sender", "[adaptors][associate]") {
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using snd_t = decltype(ex::associate(ex::just(), null_token{}));
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