[cwzwarich]

The default mode in Rust is value semantics, similar to C++'s default. Rust does have the advantage of move-by-default on uses and checking the validity of moves, but if you want unique_ptr behavior then you need Box. C++ has the advantage (if you would call it that) of allowing arbitrary code in move constructors.

[phaylon]

I think he was more talking about the unique ownership part, especially that values themselves follow the same rules.

Which I find fitting, since in Rust, the Box is (at least to me) more about indirection. The single-owner semantics just come in because Box follows the same rules as anything else, while for unique_ptr they are part of the pointer concept.