diff options
Diffstat (limited to 'lib/util.h')
| -rw-r--r-- | lib/util.h | 28 |
1 files changed, 19 insertions, 9 deletions
@@ -56,6 +56,7 @@ class Omittable : public std::optional<T> { "You cannot make an Omittable<> with a reference type"); public: + using base_type = std::optional<T>; using value_type = std::decay_t<T>; static_assert(std::is_default_constructible_v<value_type>, "Omittable<> requires a default-constructible type"); @@ -64,13 +65,22 @@ public: // Overload emplace() to allow passing braced-init-lists (the standard // emplace() does direct-initialisation but not direct-list-initialisation). - using std::optional<T>::emplace; - T& emplace(const T& val) { return std::optional<T>::emplace(val); } - T& emplace(T&& val) { return std::optional<T>::emplace(std::move(val)); } - + using base_type::emplace; + T& emplace(const T& val) { return base_type::emplace(val); } + T& emplace(T&& val) { return base_type::emplace(std::move(val)); } + + // use value_or() or check (with operator! or has_value) before accessing + // with operator-> or operator* + // The technical reason is that Xcode 10 has incomplete std::optional + // that has no value(); but using value() may also mean that you rely + // on the optional throwing an exception (which is not assumed practice + // throughout Quotient) or that you spend unnecessary CPU cycles on + // an extraneous has_value() check. + value_type& value() = delete; + const value_type& value() const = delete; value_type& edit() { - return this->has_value() ? this->value() : this->emplace(); + return this->has_value() ? base_type::operator*() : this->emplace(); } /// Merge the value from another Omittable @@ -92,10 +102,10 @@ public: // a bit too surprising: value() & doesn't lazy-create an object; // and it's too easy to inadvertently change the underlying value. - const value_type* operator->() const& { return &this->value(); } - value_type* operator->() && { return &this->value(); } - const value_type& operator*() const& { return this->value(); } - value_type& operator*() && { return this->value(); } + const value_type* operator->() const& { return base_type::operator->(); } + value_type* operator->() && { return base_type::operator->(); } + const value_type& operator*() const& { return base_type::operator*(); } + value_type& operator*() && { return base_type::operator*(); } }; namespace _impl { |