notworking.rs

use std::collections::HashMap;

struct Module;
struct Data {
    modules: HashMap<String, Module>,
}

impl Data {
    fn module<S: AsRef<str>>(&mut self, name: S) -> &mut Module {
        if let Some(m) = self.modules.get_mut(name.as_ref()) {
            return m;
        }
        // shouldn't the borrow of mut self end here because the object
        // did not found in the map, hence the following statements should work
        self.modules.insert(name.as_ref().into(), Module);
        self.modules.get_mut(name.as_ref()).unwrap()
    }
}
fn main() {}