The bits of Rust that feel "bolted on" were known to Rust's developers prior to the v1.0 freeze. You can go back through the mailing lists and find talk about t

The bits of Rust that feel "bolted on" were known to Rust's developers prior to the v1.0 freeze. You can go back through the mailing lists and find talk about things like higher-kinded types and guaranteed tail call optimization and all sorts of other things. ...the problem is that doing this sort of stuff in an eagerly evaluated native-compiled imperative language with no GC and an emphasis on C interop is an area of active research. Rust is literally pushing the envelope with things like its take on async/await.