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make almost everything constexpr that can be #1772

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make almost everything constexpr that can be #1772

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fb43b35
refactor `continues_on` and `let_value` to be more constexpr-friendly
ericniebler Jan 22, 2026
0b8305b
add missing `constexpr` in `__variant`
ericniebler Jan 22, 2026
31a22d6
stdexec::just, ::just_error, & ::just_stopped: constexpr
RobertLeahy Jan 20, 2026
cfccd3d
make everything constexpr that can be
ericniebler Jan 20, 2026
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4 changes: 2 additions & 2 deletions include/asioexec/completion_token.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -358,7 +358,7 @@ namespace asioexec {
template <typename T, typename... Us>
requires std::constructible_from<Initiation, T>
&& std::constructible_from<args_type_, Us...>
explicit constexpr sender(T&& t, Us&&... us) noexcept(
constexpr explicit sender(T&& t, Us&&... us) noexcept(
std::is_nothrow_constructible_v<Initiation, T>
&& std::is_nothrow_constructible_v<args_type_, Us...>)
: init_(static_cast<T&&>(t))
Expand Down Expand Up @@ -429,7 +429,7 @@ namespace asioexec {
};
}
public:
explicit constexpr executor(
constexpr explicit executor(
operation_state_base<Signatures, Receiver>& self,
const Executor& ex) noexcept
: self_(self)
Expand Down
79 changes: 42 additions & 37 deletions include/exec/async_scope.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,7 @@ namespace exec {
struct __t : __task {
using __id = __when_empty_op;

explicit __t(const __impl* __scope, _Constrained&& __sndr, _Receiver __rcvr)
constexpr explicit __t(const __impl* __scope, _Constrained&& __sndr, _Receiver __rcvr)
: __task{{}, __scope, __notify_waiter}
, __op_(
STDEXEC::connect(
Expand Down Expand Up @@ -101,7 +101,7 @@ namespace exec {
}

private:
static void __notify_waiter(__task* __self) noexcept {
static constexpr void __notify_waiter(__task* __self) noexcept {
STDEXEC::start(static_cast<__t*>(__self)->__op_);
}

Expand Down Expand Up @@ -206,7 +206,7 @@ namespace exec {
__complete(__scope);
}

void set_stopped() noexcept
constexpr void set_stopped() noexcept
requires __callable<set_stopped_t, _Receiver>
{
auto __scope = __op_->__scope_;
Expand All @@ -216,7 +216,7 @@ namespace exec {
__complete(__scope);
}

auto get_env() const noexcept -> __env_t<env_of_t<_Receiver>> {
constexpr auto get_env() const noexcept -> __env_t<env_of_t<_Receiver>> {
return make_env(
STDEXEC::get_env(__op_->__rcvr_),
STDEXEC::prop{get_stop_token, __op_->__scope_->__stop_source_.get_token()});
Expand All @@ -236,12 +236,12 @@ namespace exec {
connect_result_t<_Constrained, __nest_rcvr_t> __op_;

template <__decays_to<_Constrained> _Sender, __decays_to<_Receiver> _Rcvr>
explicit __t(const __impl* __scope, _Sender&& __c, _Rcvr&& __rcvr)
constexpr explicit __t(const __impl* __scope, _Sender&& __c, _Rcvr&& __rcvr)
: __nest_op_base<_ReceiverId>{{}, __scope, static_cast<_Rcvr&&>(__rcvr)}
, __op_(STDEXEC::connect(static_cast<_Sender&&>(__c), __nest_rcvr_t{this})) {
}

void start() & noexcept {
constexpr void start() & noexcept {
STDEXEC_ASSERT(this->__scope_);
auto& __active = this->__scope_->__active_;
__active.fetch_add(1, __std::memory_order_relaxed);
Expand Down Expand Up @@ -313,7 +313,7 @@ namespace exec {
struct __subscription : __immovable {
void (*__complete_)(__subscription*) noexcept = nullptr;

void __complete() noexcept {
constexpr void __complete() noexcept {
__complete_(this);
}

Expand All @@ -330,7 +330,7 @@ namespace exec {
using __forward_consumer =
stop_token_of_t<env_of_t<_Receiver>>::template callback_type<__forward_stopped>;

void __complete_() noexcept {
constexpr void __complete_() noexcept {
STDEXEC_TRY {
__forward_consumer_.reset();
auto __state = std::move(__state_);
Expand Down Expand Up @@ -379,7 +379,7 @@ namespace exec {
public:
using __id = __future_op;

~__t() noexcept {
constexpr ~__t() noexcept {
if (__state_ != nullptr) {
auto __raw_state = __state_.get();
std::unique_lock __guard{__raw_state->__mutex_};
Expand All @@ -395,7 +395,9 @@ namespace exec {
}

template <class _Receiver2>
explicit __t(_Receiver2&& __rcvr, std::unique_ptr<__future_state<_Sender, _Env>> __state)
constexpr explicit __t(
_Receiver2&& __rcvr,
std::unique_ptr<__future_state<_Sender, _Env>> __state)
: __subscription{
{},
[](__subscription* __self) noexcept -> void {
Expand All @@ -409,7 +411,7 @@ namespace exec {
__forward_stopped{&__state_->__stop_source_}) {
}

void start() & noexcept {
constexpr void start() & noexcept {
STDEXEC_TRY {
if (!!__state_) {
std::unique_lock __guard{__state_->__mutex_};
Expand Down Expand Up @@ -442,7 +444,7 @@ namespace exec {
#else

template <class _Tag, class... _Ts>
auto __completion_as_tuple_(_Tag (*)(_Ts...)) -> std::tuple<_Tag, _Ts...>;
constexpr auto __completion_as_tuple_(_Tag (*)(_Ts...)) -> std::tuple<_Tag, _Ts...>;

template <class _Fn>
using __completion_as_tuple_t = decltype(__scope::__completion_as_tuple_(
Expand Down Expand Up @@ -472,7 +474,7 @@ namespace exec {

template <class _Ty>
struct __dynamic_delete {
__dynamic_delete()
constexpr __dynamic_delete()
: __delete_([](_Ty* __p) { delete __p; }) {
}

Expand All @@ -489,7 +491,7 @@ namespace exec {
return *this;
}

void operator()(_Ty* __p) {
constexpr void operator()(_Ty* __p) {
__delete_(__p);
}

Expand All @@ -498,7 +500,7 @@ namespace exec {

template <class _Completions, class _Env>
struct __future_state_base {
__future_state_base(_Env __env, const __impl* __scope)
constexpr __future_state_base(_Env __env, const __impl* __scope)
: __forward_scope_{
std::in_place,
__scope->__stop_source_.get_token(),
Expand All @@ -519,7 +521,7 @@ namespace exec {
}
}

void __step_from_to_(
constexpr void __step_from_to_(
std::unique_lock<std::mutex>& __guard,
__future_step __from,
__future_step __to) {
Expand Down Expand Up @@ -548,7 +550,7 @@ namespace exec {
__future_state_base<_Completions, _Env>* __state_;
const __impl* __scope_;

void __dispatch_result_(std::unique_lock<std::mutex>& __guard) noexcept {
constexpr void __dispatch_result_(std::unique_lock<std::mutex>& __guard) noexcept {
auto& __state = *__state_;
auto __local_subscribers = std::move(__state.__subscribers_);
__state.__forward_scope_.reset();
Expand All @@ -568,7 +570,7 @@ namespace exec {
}

template <class _Tag, class... _As>
void __save_completion(_Tag, _As&&... __as) noexcept {
constexpr void __save_completion(_Tag, _As&&... __as) noexcept {
auto& __state = *__state_;
STDEXEC_TRY {
using _Tuple = __decayed_std_tuple<_Tag, _As...>;
Expand All @@ -581,29 +583,29 @@ namespace exec {
}

template <__movable_value... _As>
void set_value(_As&&... __as) noexcept {
constexpr void set_value(_As&&... __as) noexcept {
auto& __state = *__state_;
std::unique_lock __guard{__state.__mutex_};
__save_completion(set_value_t(), static_cast<_As&&>(__as)...);
__dispatch_result_(__guard);
}

template <__movable_value _Error>
void set_error(_Error&& __err) noexcept {
constexpr void set_error(_Error&& __err) noexcept {
auto& __state = *__state_;
std::unique_lock __guard{__state.__mutex_};
__save_completion(set_error_t(), static_cast<_Error&&>(__err));
__dispatch_result_(__guard);
}

void set_stopped() noexcept {
constexpr void set_stopped() noexcept {
auto& __state = *__state_;
std::unique_lock __guard{__state.__mutex_};
__save_completion(set_stopped_t());
__dispatch_result_(__guard);
}

auto get_env() const noexcept -> const __env_t<_Env>& {
constexpr auto get_env() const noexcept -> const __env_t<_Env>& {
return __state_->__env_;
}
};
Expand All @@ -617,12 +619,12 @@ namespace exec {
struct __future_state : __future_state_base<__future_completions_t<_Sender, _Env>, _Env> {
using _Completions = __future_completions_t<_Sender, _Env>;

__future_state(connect_t, _Sender&& __sndr, _Env __env, const __impl* __scope)
constexpr __future_state(connect_t, _Sender&& __sndr, _Env __env, const __impl* __scope)
: __future_state_base<_Completions, _Env>(static_cast<_Env&&>(__env), __scope)
, __op_(static_cast<_Sender&&>(__sndr), __future_receiver_t<_Sender, _Env>{this, __scope}) {
}

__future_state(_Sender __sndr, _Env __env, const __impl* __scope)
constexpr __future_state(_Sender __sndr, _Env __env, const __impl* __scope)
: __future_state(
STDEXEC::connect,
static_cast<_Sender&&>(__sndr),
Expand Down Expand Up @@ -691,7 +693,7 @@ namespace exec {
private:
friend struct async_scope;

explicit __t(std::unique_ptr<__future_state<_Sender, _Env>> __state) noexcept
constexpr explicit __t(std::unique_ptr<__future_state<_Sender, _Env>> __state) noexcept
: __state_(std::move(__state)) {
std::unique_lock __guard{__state_->__mutex_};
__state_->__step_from_to_(__guard, __future_step::__created, __future_step::__future);
Expand All @@ -713,12 +715,12 @@ namespace exec {
inplace_stop_token __token_;

[[nodiscard]]
auto query(get_stop_token_t) const noexcept -> inplace_stop_token {
constexpr auto query(get_stop_token_t) const noexcept -> inplace_stop_token {
return __token_;
}

[[nodiscard]]
auto query(get_scheduler_t) const noexcept -> STDEXEC::inline_scheduler {
constexpr auto query(get_scheduler_t) const noexcept -> STDEXEC::inline_scheduler {
return {};
}
};
Expand All @@ -742,7 +744,7 @@ namespace exec {
using receiver_concept = STDEXEC::receiver_t;
__spawn_op_base<_EnvId>* __op_;

void set_value() noexcept {
constexpr void set_value() noexcept {
__op_->__delete_(__op_);
}

Expand All @@ -752,11 +754,11 @@ namespace exec {
std::rethrow_exception(std::move(__eptr));
}

void set_stopped() noexcept {
constexpr void set_stopped() noexcept {
__op_->__delete_(__op_);
}

auto get_env() const noexcept -> const __spawn_env_t<_Env>& {
constexpr auto get_env() const noexcept -> const __spawn_env_t<_Env>& {
return __op_->__env_;
}
};
Expand All @@ -771,7 +773,7 @@ namespace exec {
using _Sender = STDEXEC::__t<_SenderId>;

struct __t : __spawn_op_base<_EnvId> {
__t(connect_t, _Sender&& __sndr, _Env __env, const __impl* __scope)
constexpr __t(connect_t, _Sender&& __sndr, _Env __env, const __impl* __scope)
: __spawn_op_base<_EnvId>{
__env::__join(
static_cast<_Env&&>(__env),
Expand All @@ -780,7 +782,7 @@ namespace exec {
, __data_(static_cast<_Sender&&>(__sndr), __spawn_receiver_t<_Env>{this}) {
}

__t(_Sender __sndr, _Env __env, const __impl* __scope)
constexpr __t(_Sender __sndr, _Env __env, const __impl* __scope)
: __t(
STDEXEC::connect,
static_cast<_Sender&&>(__sndr),
Expand All @@ -807,12 +809,12 @@ namespace exec {

template <sender _Constrained>
[[nodiscard]]
auto when_empty(_Constrained&& __c) const -> __when_empty_sender_t<_Constrained> {
constexpr auto when_empty(_Constrained&& __c) const -> __when_empty_sender_t<_Constrained> {
return __when_empty_sender_t<_Constrained>{&__impl_, static_cast<_Constrained&&>(__c)};
}

[[nodiscard]]
auto on_empty() const {
constexpr auto on_empty() const {
return when_empty(just());
}

Expand All @@ -821,7 +823,7 @@ namespace exec {

template <sender _Constrained>
[[nodiscard]]
auto nest(_Constrained&& __c) -> nest_result_t<_Constrained> {
constexpr auto nest(_Constrained&& __c) -> nest_result_t<_Constrained> {
return nest_result_t<_Constrained>{&__impl_, static_cast<_Constrained&&>(__c)};
}

Expand All @@ -837,18 +839,21 @@ namespace exec {
}

template <__movable_value _Env = env<>, sender_in<__env_t<_Env>> _Sender>
[[nodiscard]]
auto spawn_future(_Sender&& __sndr, _Env __env = {}) -> __future_t<_Sender, _Env> {
using __state_t = __future_state<nest_result_t<_Sender>, _Env>;
auto __state = std::make_unique<__state_t>(
nest(static_cast<_Sender&&>(__sndr)), static_cast<_Env&&>(__env), &__impl_);
return __future_t<_Sender, _Env>{std::move(__state)};
}

auto get_stop_source() noexcept -> inplace_stop_source& {
[[nodiscard]]
constexpr auto get_stop_source() noexcept -> inplace_stop_source& {
return __impl_.__stop_source_;
}

auto get_stop_token() const noexcept -> inplace_stop_token {
[[nodiscard]]
constexpr auto get_stop_token() const noexcept -> inplace_stop_token {
return __impl_.__stop_source_.get_token();
}

Expand Down
6 changes: 3 additions & 3 deletions include/exec/completion_signatures.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,14 +25,14 @@ namespace exec {
// make_completion_signatures
namespace detail {
template <class Tag, class... As>
auto normalize_impl(As&&...) -> Tag (*)(As...);
constexpr auto normalize_impl(As&&...) -> Tag (*)(As...);

template <class Tag, class... As>
auto normalize(Tag (*)(As...))
constexpr auto normalize(Tag (*)(As...))
-> decltype(detail::normalize_impl<Tag>(STDEXEC::__declval<As>()...));

template <class... Sigs>
auto make_unique(Sigs*...)
constexpr auto make_unique(Sigs*...)
-> STDEXEC::__mapply_q<STDEXEC::completion_signatures, STDEXEC::__mmake_set<Sigs...>>;

template <class... Sigs>
Expand Down
4 changes: 2 additions & 2 deletions include/exec/finally.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ namespace exec {
void set_value() noexcept {
STDEXEC_TRY {
auto& __result = __op_->__result_.__get();
__result.visit(__visitor{}, static_cast<_ResultType&&>(__result), __op_);
STDEXEC::__visit(__visitor{}, static_cast<_ResultType&&>(__result), __op_);
}
STDEXEC_CATCH_ALL {
if constexpr (!__mapply_q<__nothrow_decay_copyable_t, _ResultType>::value) {
Expand Down Expand Up @@ -185,7 +185,7 @@ namespace exec {
.template emplace<__decayed_tuple<_Args...>>(static_cast<_Args&&>(__args)...);
STDEXEC_ASSERT(__op_.index() == 0);
auto __final = static_cast<_FinalSender&&>(__op_.template get<0>().__sndr_);
__final_op_t& __final_op = __op_.template emplace_from_at<1>(
__final_op_t& __final_op = __op_.template __emplace_from<1>(
STDEXEC::connect, static_cast<_FinalSender&&>(__final), __final_receiver_t{this});
STDEXEC::start(__final_op);
}
Expand Down
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