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ConorWilliamsConor
ConorWilliams
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Conor
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[V4] Lift meta-functions (#112)
* lift * lift optimization * overload * decay fn to lifted * lifted pass 1 test * doc * await resume * fix semantics * todo * no separate .fn in pkg * assert non-null --------- Co-authored-by: Conor <conor@myrtle.com>
1 parent b2a4543 commit 4204e59

6 files changed

Lines changed: 456 additions & 43 deletions

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‎CMakeLists.txt‎

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@@ -91,6 +91,7 @@ target_sources(libfork_libfork
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src/core/promise.cxx
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src/core/stop.cxx
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src/core/projected.cxx
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src/core/lift.cxx
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# libfork.batteries
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src/batteries/batteries.cxx
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src/batteries/deque.cxx

‎src/core/core.cxx‎

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@@ -23,3 +23,4 @@ export import :exception;
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export import :final_suspend;
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export import :awaitables;
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export import :projected;
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export import :lift;

‎src/core/lift.cxx‎

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@@ -0,0 +1,90 @@
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module;
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#include "libfork/__impl/assume.hpp"
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#include "libfork/__impl/exception.hpp"
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#include "libfork/__impl/utils.hpp"
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export module libfork.core:lift;
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import libfork.utils;
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import :task;
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import :ops;
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import :final_suspend;
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import :awaitables;
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namespace lf {
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template <typename T>
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using lift_store_t = std::conditional_t<std::is_lvalue_reference_v<T>, T, std::remove_cvref_t<T>>;
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struct lift_impl {
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private:
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template <typename Fn, typename Context, typename... Args>
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using task_t = task<std::invoke_result_t<Fn, Args...>, Context>;
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template <typename Fn, typename Context, typename... Args>
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static auto impl(lift_store_t<Fn> fn, lift_store_t<Args>... args) -> task_t<Fn, Context, Args...> {
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co_return std::invoke(static_cast<Fn>(fn), static_cast<Args>(args)...);
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}
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public:
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template <typename Fn, typename Context, typename... Args>
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requires std::invocable<Fn &&, Args &&...>
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static auto operator()(env<Context>, Fn &&fn, Args &&...args) -> task_t<Fn &&, Context, Args &&...> {
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return impl<Fn &&, Context, Args &&...>(LF_FWD(fn), LF_FWD(args)...);
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}
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};
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// TODO: merge fn in ops to args
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/**
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* @brief Lifts a synchronous function into an asynchronous task.
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*
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* Forked lifted tasks capture rvalues by value.
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* Called lifted tasks have an optimized path that avoids creating a new task.
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*
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* Both invocations respect cancellation and push exceptions to the parent scope.
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*/
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export inline constexpr lift_impl lift{};
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/**
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* @brief An optimization for non-forked lifted functions.
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*/
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template <worker_context Context, bool StopToken, typename R, typename Fn, typename... Args>
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struct lifted_awaitable : std::suspend_never {
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[[no_unique_address]]
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pkg<category::call, StopToken, Context, R, Fn, Args...> pkg;
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frame_t<Context> *parent;
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constexpr void await_resume() noexcept {
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// Noop if stop has been requested.
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if constexpr (StopToken) {
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if (pkg.stop_token.stop_requested()) {
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return;
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}
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} else {
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if (parent->stop_requested()) {
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return;
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}
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}
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LF_TRY {
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if constexpr (std::is_void_v<R>) {
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std::move(pkg.args).apply([](lift_impl, auto &&fn, auto &&...args) -> void {
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std::invoke(LF_FWD(fn), LF_FWD(args)...);
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});
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} else {
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std::move(pkg.args).apply([addr = pkg.return_addr](lift_impl, auto &&fn, auto &&...args) -> void {
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LF_ASSUME(addr);
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*addr = std::invoke(LF_FWD(fn), LF_FWD(args)...);
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});
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}
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} LF_CATCH(...) {
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stash_current_exception(parent);
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}
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}
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};
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} // namespace lf

‎src/core/ops.cxx‎

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Original file line numberDiff line numberDiff line change
@@ -41,31 +41,11 @@ template <category Cat, bool StopToken, typename Context, typename R, typename F
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struct [[nodiscard("You should immediately co_await this!")]] pkg {
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[[no_unique_address]] std::conditional_t<StopToken, stop_source::stop_token, no_stop_t> stop_token;
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[[no_unique_address]] std::conditional_t<std::is_void_v<R>, no_ret_t, R *> return_addr;
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[[no_unique_address]] Fn fn;
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[[no_unique_address]] tuple<Args...> args;
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[[no_unique_address]] tuple<Fn, Args...> args;
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};
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// clang-format on
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/**
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* @brief Forward the function member of a pkg correctly.
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*
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* Handles three cases:
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* - rvalue reference Fn: move it.
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* - lvalue reference Fn: return by reference.
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* - value type Fn (small trivially-copyable stored directly): return by value.
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*/
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template <typename Fn>
59-
constexpr auto fwd_fn(auto &&fn) noexcept -> Fn {
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if constexpr (std::is_rvalue_reference_v<Fn>) {
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return std::move(fn);
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} else if constexpr (std::is_lvalue_reference_v<Fn> || small_trivially_copyable<Fn>) {
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return fn;
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} else {
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static_assert(false, "Invalid Fn type in fwd_fn");
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}
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}
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// =============== Join =============== //
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struct join_type {};
@@ -107,30 +87,30 @@ struct scope_ops : scope_base {
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template <typename R, typename... Args, async_invocable_to<R, Context, Args...> Fn>
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static constexpr auto fork(R *ret, Fn &&fn, Args &&...args) noexcept -> fork_pkg<R, Fn, Args...> {
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return {.return_addr = ret, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.return_addr = ret, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable<Context, Args...> Fn>
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static constexpr auto fork_drop(Fn &&fn, Args &&...args) noexcept -> fork_pkg<void, Fn, Args...> {
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return {.return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable_to<void, Context, Args...> Fn>
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static constexpr auto fork(Fn &&fn, Args &&...args) noexcept -> fork_pkg<void, Fn, Args...> {
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return {.return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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// === Call === //
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template <typename R, typename... Args, async_invocable_to<R, Context, Args...> Fn>
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static constexpr auto call(R *ret, Fn &&fn, Args &&...args) noexcept -> call_pkg<R, Fn, Args...> {
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return {.return_addr = ret, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.return_addr = ret, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable<Context, Args...> Fn>
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static constexpr auto call_drop(Fn &&fn, Args &&...args) noexcept -> call_pkg<void, Fn, Args...> {
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return {.return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
109+
return {.return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable_to<void, Context, Args...> Fn>
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static constexpr auto call(Fn &&fn, Args &&...args) noexcept -> call_pkg<void, Fn, Args...> {
133-
return {.return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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};
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@@ -179,30 +159,30 @@ struct child_scope_ops : scope_base, stop_source {
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template <typename R, typename... Args, async_invocable_to<R, Context, Args...> Fn>
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constexpr auto fork(R *ret, Fn &&fn, Args &&...args) noexcept -> fork_pkg<R, Fn, Args...> {
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return {.stop_token = token(), .return_addr = ret, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
162+
return {.stop_token = token(), .return_addr = ret, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable<Context, Args...> Fn>
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constexpr auto fork_drop(Fn &&fn, Args &&...args) noexcept -> fork_pkg<void, Fn, Args...> {
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return {.stop_token = token(), .return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
166+
return {.stop_token = token(), .return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable_to<void, Context, Args...> Fn>
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constexpr auto fork(Fn &&fn, Args &&...args) noexcept -> fork_pkg<void, Fn, Args...> {
190-
return {.stop_token = token(), .return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.stop_token = token(), .return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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193173
// === Call (binds this scope's stop source as child stop source) === //
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195175
template <typename R, typename... Args, async_invocable_to<R, Context, Args...> Fn>
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constexpr auto call(R *ret, Fn &&fn, Args &&...args) noexcept -> call_pkg<R, Fn, Args...> {
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return {.stop_token = token(), .return_addr = ret, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
177+
return {.stop_token = token(), .return_addr = ret, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable<Context, Args...> Fn>
200180
constexpr auto call_drop(Fn &&fn, Args &&...args) noexcept -> call_pkg<void, Fn, Args...> {
201-
return {.stop_token = token(), .return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
181+
return {.stop_token = token(), .return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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template <typename... Args, async_invocable_to<void, Context, Args...> Fn>
204184
constexpr auto call(Fn &&fn, Args &&...args) noexcept -> call_pkg<void, Fn, Args...> {
205-
return {.stop_token = token(), .return_addr = {}, .fn = LF_FWD(fn), .args = {LF_FWD(args)...}};
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return {.stop_token = token(), .return_addr = {}, .args = {LF_FWD(fn), LF_FWD(args)...}};
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}
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};
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‎src/core/promise.cxx‎

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Original file line numberDiff line numberDiff line change
@@ -21,6 +21,7 @@ import :ops;
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import :handles;
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import :final_suspend;
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import :awaitables;
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import :lift;
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2526
// TODO: vet constexpr usage in the library
2627

@@ -68,14 +69,25 @@ struct mixin_frame {
6869

6970
// Fork/call
7071
template <category Cat, bool StopToken, typename R, typename Fn, typename... Args>
71-
constexpr auto await_transform(this auto &self, pkg<Cat, StopToken, Context, R, Fn, Args...> &&pkg) noexcept
72-
-> async_awaitable<Cat, Context> {
72+
constexpr auto
73+
await_transform(this auto &self, pkg<Cat, StopToken, Context, R, Fn, Args...> &&pkg) noexcept {
7374
LF_TRY {
7475
return self.await_transform_pkg(std::move(pkg));
7576
} LF_CATCH_ALL {
7677
stash_current_exception(&self.frame);
7778
}
78-
return {.child = nullptr};
79+
return async_awaitable<Cat, Context>{.child = nullptr};
80+
}
81+
82+
// Specialization for lifted functions
83+
template <bool StopToken, typename R, typename Fn, typename... Args>
84+
requires std::same_as<std::remove_cvref_t<Fn>, lift_impl>
85+
constexpr auto
86+
await_transform(this auto &self, pkg<category::call, StopToken, Context, R, Fn, Args...> &&pkg) noexcept {
87+
return lifted_awaitable<Context, StopToken, R, Fn, Args...>{
88+
.pkg = std::move(pkg),
89+
.parent = &self.frame,
90+
};
7991
}
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8193
// Custom awaitable
@@ -113,15 +125,10 @@ struct mixin_frame {
113125
constexpr auto
114126
await_transform_pkg(this auto const &self, pkg<Cat, StopToken, Context, R, Fn, Args...> &&pkg) noexcept(
115127
async_nothrow_invocable<Fn, Context, Args...>) -> async_awaitable<Cat, Context> {
116-
using U = async_result_t<Fn, Context, Args...>;
117-
118-
// clang-format off
119128

120-
promise_type<U, Context> *child_promise = get(key(), std::move(pkg.args).apply(
121-
[&](auto &&...args) LF_HOF(ctx_invoke_t<Context>{}(fwd_fn<Fn>(pkg.fn), LF_FWD(args)...))
122-
));
129+
using U = async_result_t<Fn, Context, Args...>;
123130

124-
// clang-format on
131+
promise_type<U, Context> *child_promise = get(key(), std::move(pkg.args).apply(ctx_invoke_t<Context>{}));
125132

126133
LF_ASSUME(child_promise);
127134

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