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std::expected<T,E>::value_or

template< class U > constexpr T value_or( U&& default_value ) const&;	(1)	(since C++23)
template< class U > constexpr T value_or( U&& default_value ) &&;	(2)	(since C++23)

Returns the contained value if *this contains an expected value, otherwise returns default_value.

1) Returns bool(*this) ? **this : static_cast<T>(std::forward<U>(default_value))

2) Returns bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(default_value))

default_value	-	the value to use in case `*this` does not contain an expected value
Type requirements
-`T` must meet the requirements of CopyConstructible in order to use overload (1).
-`T` must meet the requirements of MoveConstructible in order to use overload (2).
-`U&&` must be convertible to `T`

The currently contained value if *this contains an expected value, or default_value otherwise.

Any exception thrown by the selected constructor of the return value T.

If T is (possibly cv-qualified) void, this member is not declared.