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Remove unneccesary move in emplace

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Fixes #122
This commit is contained in:
Sy Brand
2022-11-24 12:01:40 +00:00
parent d901f362cc
commit f5d8f5c462
2 changed files with 28 additions and 3 deletions
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7
include/tl/expected.hpp
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@@ -1680,19 +1680,20 @@ public:
T, Args &&...>::value> * = nullptr>
void emplace(Args &&... args) {
if (has_value()) {
val() = T(std::forward<Args>(args)...);
val().~T();
} else {
err().~unexpected<E>();
::new (valptr()) T(std::forward<Args>(args)...);
this->m_has_val = true;
}
::new (valptr()) T(std::forward<Args>(args)...);
}
template <class... Args, detail::enable_if_t<!std::is_nothrow_constructible<
T, Args &&...>::value> * = nullptr>
void emplace(Args &&... args) {
if (has_value()) {
val() = T(std::forward<Args>(args)...);
val().~T();
::new (valptr()) T(std::forward<Args>(args)...);
} else {
auto tmp = std::move(err());
err().~unexpected<E>();

24
tests/issues.cpp
View File

@@ -136,3 +136,27 @@ tl::expected<int, std::unique_ptr<std::string>> func()
TEST_CASE("Issue 61", "[issues.61]") {
REQUIRE(func().value() == 1);
}
struct move_tracker {
int moved = 0;
constexpr move_tracker() = default;
constexpr move_tracker(move_tracker const &other) noexcept = default;
constexpr move_tracker(move_tracker &&orig) noexcept
: moved(orig.moved + 1) {}
constexpr move_tracker &
operator=(move_tracker const &other) noexcept = default;
constexpr move_tracker &operator=(move_tracker &&orig) noexcept {
moved = orig.moved + 1;
return *this;
}
};
TEST_CASE("Issue 122", "[issues.122]") {
tl::expected<move_tracker, int> res;
res.emplace(); // why moved?
REQUIRE(res.value().moved == 0);
}