Function module_segment 

pub fn module_segment(segment: &str) -> String

The Rust module-segment spelling of one typl package name segment: mod becomes r#mod, crate becomes crate_, and an ordinary segment is returned unchanged.

This exists so that the module tree ridlc writes for --emit rust and the paths [type_path] emits cannot drift apart. Both spell a package segment through [ident], which is the only definition of that spelling. A tree that writes a segment raw emits pub mod mod;, which does not parse, and a tree that escapes a keyword differently from the reference emits a module the reference cannot name.