cpp/utility/expected/emplace

Constructs an expected value in-place. After the call, returns true.

@1@ Destroys the contained value, then initializes the expected value contained in as if by direct-initializing an object of type  from the arguments. .

@2@ Destroys the contained value, then initializes the expected value contained in as if by direct-initializing an object of type  from the arguments. .

@3@ If contains an unexpected value, destroys that value.

Return value
A reference to the new contained value.