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std::expected<T,E>::~expected - cppreference.com

From cppreference.com

(since C++23)

Main template destructor

Destroys the contained value:

  • If has_value() is true, destroys the expected value.
  • Otherwise, destroys the unexpected value.

This destructor is trivial if std::is_trivially_destructible_v<T> and std::is_trivially_destructible_v<E> are both true.

void partial specialization destructor

If has_value() is false, destroys the unexpected value.

This destructor is trivial if std::is_trivially_destructible_v<E> is true.

Example

#include <expected>
#include <iostream>
#include <source_location>

inline
void name(int x, std::source_location sloc = std::source_location::current())
{
    std::cout << sloc.function_name() << " : " << x << '\n';
}

struct Value
{
    int m{};
    ~Value() { name(m); }
};

struct Error
{
    int e{};
    ~Error() { name(e); }
};

int main()
{
    std::expected<Value, Error> e1 {42};
    std::expected<Value, Error> e2 {std::unexpect, 13};
    std::expected<void, Error>  e3 {std::unexpect, 37};
}

Possible output: 

Error::~Error : 37
Error::~Error : 13
Value::~Value : 42