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Merge pull request #34 from denizevrenci/fix_emplace_on_ref

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Fix implementation of optional<T&>::emplace()
This commit is contained in:
Simon Brand
2019-07-08 13:28:30 +01:00
committed by GitHub
parent 5c4876059c ce266d5280
commit 83a0b49e5e
2 changed files with 26 additions and 18 deletions
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33
include/tl/optional.hpp
View File

@@ -1939,12 +1939,12 @@ public:
template <class U = T,
detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
* = nullptr>
constexpr optional(U &&u) : m_value(std::addressof(u)) {
constexpr optional(U &&u) noexcept : m_value(std::addressof(u)) {
static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue");
}
template <class U>
constexpr explicit optional(const optional<U> &rhs) : optional(*rhs) {}
constexpr explicit optional(const optional<U> &rhs) noexcept : optional(*rhs) {}
/// No-op
~optional() = default;
@@ -1977,33 +1977,30 @@ public:
///
/// Rebinds this optional to the referee of `rhs` if there is one. Otherwise
/// resets the stored value in `*this`.
template <class U> optional &operator=(const optional<U> &rhs) {
template <class U> optional &operator=(const optional<U> &rhs) noexcept {
m_value = std::addressof(rhs.value());
return *this;
}
/// Constructs the value in-place, destroying the current one if there is
/// one.
template <class... Args> T &emplace(Args &&... args) noexcept {
static_assert(std::is_constructible<T, Args &&...>::value,
"T must be constructible with Args");
*this = nullopt;
this->construct(std::forward<Args>(args)...);
return value();
/// Rebinds this optional to `u`.
template <class U = T,
detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
* = nullptr>
optional &emplace(U &&u) noexcept {
return *this = std::forward<U>(u);
}
void swap(optional &rhs) noexcept { std::swap(m_value, rhs.m_value); }
/// Returns a pointer to the stored value
constexpr const T *operator->() const { return m_value; }
constexpr const T *operator->() const noexcept { return m_value; }
TL_OPTIONAL_11_CONSTEXPR T *operator->() { return m_value; }
TL_OPTIONAL_11_CONSTEXPR T *operator->() noexcept { return m_value; }
/// Returns the stored value
TL_OPTIONAL_11_CONSTEXPR T &operator*() { return *m_value; }
TL_OPTIONAL_11_CONSTEXPR T &operator*() noexcept { return *m_value; }
constexpr const T &operator*() const { return *m_value; }
constexpr const T &operator*() const noexcept { return *m_value; }
constexpr bool has_value() const noexcept { return m_value != nullptr; }
@@ -2024,7 +2021,7 @@ public:
}
/// Returns the stored value if there is one, otherwise returns `u`
template <class U> constexpr T value_or(U &&u) const & {
template <class U> constexpr T value_or(U &&u) const & noexcept {
static_assert(std::is_copy_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be copy constructible and convertible from U");
@@ -2032,7 +2029,7 @@ public:
}
/// \group value_or
template <class U> TL_OPTIONAL_11_CONSTEXPR T value_or(U &&u) && {
template <class U> TL_OPTIONAL_11_CONSTEXPR T value_or(U &&u) && noexcept {
static_assert(std::is_move_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be move constructible and convertible from U");

11
tests/issues.cpp
View File

@@ -31,4 +31,15 @@ TEST_CASE("issue 15") {
o = o;
REQUIRE(o->value == 42);
}
TEST_CASE("issue 33") {
int i = 0;
int j = 0;
tl::optional<int&> a = i;
a.emplace(j);
*a = 42;
REQUIRE(j == 42);
REQUIRE(*a == 42);
REQUIRE(a.has_value());
}