Not for incremental compilation when a single file changed, without optimization, it's not - depending on the type of change, of course, and how heavy the C++ code in question is, and I guess on whether you're using a broken IDE/build system (my standard is the command line, using make for small projects and ninja for larger ones). And incremental compilation can scale up to much larger projects without increasing the time much, whereas in Rust that would require splitting up into crates and even then would frequently require a full rebuild due to the coarse dependency tracking of "anything in this crate changed -> rebuild all dependents".

That said, I expect incremental compilation built into rustc to greatly improve the situation - if done right, it should easily beat C++, although I don't know the details of the plan - so I'm happy someone is working on it. (In the past I wanted to work on it myself, but I was in a big generally unproductive slump..)