Can Elements Be Moved Out of a `std::initializer_list`?

initializer_list and Move Semantics

The initializer_list type in C is often used to initialize containers with brace-enclosed lists of values. However, unlike regular containers, initializer_list does not follow value semantics. As a result, a common question arises:

Can elements be moved out of a std::initializer_list?

The answer to this question is no. Attempting to do so will result in copies, even if the element being moved is of a move-only type. This is because the begin() and end() functions of initializer_list return pointers to const values. When std::move is applied to a const value, the result is an immutable rvalue reference, which cannot be meaningfully moved from. Instead, it will bind to a function parameter of type const T&, resulting in copy semantics.

This behavior may seem unexpected, given that initializer_list is intended to store a list of temporary objects. However, it is believed that making the type const or mutable at the compiler's discretion would allow for more efficient static initialization of the list.

Update: A Proposal for initializer_list Support of Move-Only Types

In response to feedback, an ISO proposal has been drafted to provide support for move-only types in initializer_list. This proposal is still under review, but it offers a potential solution to the current limitations of initializer_list when working with move-only types.

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