I think you missed the point I was trying to make. C/C++ currently: 1.) "variable" -> something that is subject to change 2.) "const variable" -> an unchanging thing that is subject to change (I guess you could say it only changes once).

This thing and Rust: "constant" -> something unable to change "mutable constant" -> a changeable constant...what? Even "mutable variable" -> a changeable thing that is a thing that is subject change doesn't make much more sense.

It is fine for "things" to be immutable by default, and in fact I think they should be. I just think "mutable" is keyword smell similar to "decltype" because type wasn't keyworded from the start.