My sense of sentiment in the project right now is that people want to keep the invariant that assignment (to an ordinary memory location) is always just a memcpy and never calls arbitrary user-defined code, because if that code does something unexpected, debugging (at least if a human's doing it) is likely to be hampered by the syntactic invisibility of the call site. This is why the most obvious ergonomic-reference-counting proposal (have a trait that lets types opt into implicit clones) ran aground, and they're now experimenting with (conceptually clunkier, in my opinion) alternatives that aim to make reference counting ergonomic but still syntactically visible.

So if Rust ever gains move constructors, you'll probably have to call them explicitly, the way you have to explicitly call .clone(). (There's actually already a third-party library that does something like this (https://docs.rs/moveit), and I think Crubit is using a similar API to let Rust code call C++ move constructors.)