You have to explicitly opt in to unstable features. Provided you don't do that, Rust is stable. There are bits of the standard library marked unstable, yes. Th

You have to explicitly opt in to unstable features. Provided you don't do that, Rust is stable. There are bits of the standard library marked unstable, yes. This is true in almost any language/compiler -- there's always some new/experimental or otherwise nonstandard stuff that the compiler will let you do if you opt into it. Clang has its own nonstandard bits. So does GCC. The fact that almost all crates in the Rust ecosystem work on stable is an indication that enough of the stdlib is stable for it to be useful. The Rust stdlib will never be "finished"; there will always be new things being added. This is true for every language. Allowing folks to experiment with unstable features is not a bad thing.