Method insert

crates/core/src/ns.rs:10–16

(&mut self, name: &str)

impl Ns {
    pub fn insert(&mut self, name: &str) -> Result<(), String> {
        if self.defined.insert(name.to_string()) {
            Ok(())
        } else {
            Err(format!("name `{name}` already defined"))
        }
    }

    pub fn tmp(&mut self, name: &str) -> String {
        let mut ret = name.to_string();