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let_value, let_error, & let_stopped: Dependent set_error_t(std::excep… #2224

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Merged
ericniebler merged 1 commit into from
Aug 23, 2026
+28 −0
Merged

let_value, let_error, & let_stopped: Dependent set_error_t(std::excep… #2224

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18 changes: 18 additions & 0 deletions include/stdexec/__detail/__let.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -565,6 +565,24 @@ namespace STDEXEC
using __what_t = __bad_result_sender_t<__sndr2_t, _LetTag, __env2_t<_Child, _Env>...>;
return STDEXEC::__throw_compile_time_error(__what_t());
}
else if constexpr (__nothrow_decay_copyable<_Args...>
&& __nothrow_invocable<_Fun, __decay_t<_Args>&...>
&& sizeof...(_Env) == 0)
{
auto __completions =
STDEXEC::get_completion_signatures<__sndr2_t, __env2_t<_Child, _Env>...>();
STDEXEC_IF_OK(__completions)
{
if constexpr (__completions.template __contains<__eptr_sig_t>())
{
return __completions;
}
else
{
return STDEXEC::__throw_dependent_sender_error<__sndr2_t>();
}
}
}
else if constexpr (__nothrow_decay_copyable<_Args...>
&& __nothrow_invocable<_Fun, __decay_t<_Args>&...>
&& (__nothrow_connectable<__sndr2_t, __rcvr2_t<_Child, _Env>>
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10 changes: 10 additions & 0 deletions test/stdexec/algos/adaptors/test_let_error.cpp
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Expand Up @@ -100,6 +100,16 @@ namespace
STDEXEC::sync_wait(std::move(snd));
}

TEST_CASE("let_error can be followed by upon_error", "[adaptors][let_error]")
{
auto snd = ex::just_error(2)
| ex::let_error([](int n) noexcept { return ex::just_error(n * 10); })
| ex::upon_error([](int n) noexcept { return n + 3; });
auto opt = ex::sync_wait(std::move(snd));
REQUIRE(opt.has_value());
CHECK(std::get<0>(*opt) == 23);
}

#if !STDEXEC_NO_STDCPP_EXCEPTIONS()
TEST_CASE("let_error can be used to produce values (error to value)", "[adaptors][let_error]")
{
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