197. Advance a State Machine with mem::replace — Move the Enum Out, No Clone

Fri, 12 Jun 2026 09:00:00 +0100

Transitioning an enum state behind &mut self looks impossible: you can’t move the old variant’s owned data into the new one without the borrow checker stopping you — so people reach for .clone(). mem::replace lets you move the whole state out, leaving a cheap placeholder behind.

Mem-Replace on rustbites

197. Advance a State Machine with mem::replace — Move the Enum Out, No Clone