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Put constraints on or_else overloads #149

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Merged
steve-downey merged 1 commit into from
Dec 6, 2025
Merged

Put constraints on or_else overloads #149

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22 changes: 16 additions & 6 deletions include/beman/optional/optional.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -727,7 +727,8 @@ class optional {
* @return optional
*/
template <class F>
constexpr optional or_else(F&& f) const&;
constexpr optional or_else(F&& f) const&
requires (std::invocable<F> && std::copy_constructible<T>);

/**
* @brief Returns an optional containing the contained value if it has one, or
Expand All @@ -738,7 +739,8 @@ class optional {
* @return auto
*/
template <class F>
constexpr optional or_else(F&& f) &&;
constexpr optional or_else(F&& f) &&
requires (std::invocable<F> && std::move_constructible<T>);

// \ref{optional.mod}, modifiers
/**
Expand Down Expand Up @@ -1231,7 +1233,9 @@ constexpr auto optional<T>::transform(F&& f) const&& {
*/
template <class T>
template <class F>
constexpr optional<T> optional<T>::or_else(F&& f) const& {
constexpr optional<T> optional<T>::or_else(F&& f) const&
requires (std::invocable<F> && std::copy_constructible<T>)
{
static_assert(std::is_same_v<std::remove_cvref_t<std::invoke_result_t<F>>, optional>);
if (has_value())
return value_;
Expand All @@ -1250,7 +1254,9 @@ constexpr optional<T> optional<T>::or_else(F&& f) const& {
*/
template <class T>
template <class F>
constexpr optional<T> optional<T>::or_else(F&& f) && {
constexpr optional<T> optional<T>::or_else(F&& f) &&
requires (std::invocable<F> && std::move_constructible<T>)
{
static_assert(std::is_same_v<std::remove_cvref_t<std::invoke_result_t<F>>, optional>);
if (has_value())
return std::move(value_);
Expand Down Expand Up @@ -1870,7 +1876,8 @@ class optional<T&> {
* return an optional type.
*/
template <class F>
constexpr optional or_else(F&& f) const;
constexpr optional or_else(F&& f) const
requires (std::invocable<F>);

// \ref{optional.mod}, modifiers
/**
Expand Down Expand Up @@ -2078,7 +2085,10 @@ constexpr optional<std::invoke_result_t<F, T&>> optional<T&>::transform(F&& f) c
*/
template <class T>
template <class F>
constexpr optional<T&> optional<T&>::or_else(F&& f) const {
constexpr optional<T&> optional<T&>::or_else(F&& f) const

requires (std::invocable<F>)
{
using U = std::invoke_result_t<F>;
static_assert(std::is_same_v<std::remove_cvref_t<U>, optional>, "Result must be an optional");
if (has_value()) {
Expand Down