1use jrsonnet_interner::IStr;2use rustc_hash::FxHashMap;3use std::rc::Rc;45#[derive(Default, Debug)]6struct LayeredHashMapInternals<V> {7 parent: Option<LayeredHashMap<V>>,8 current: FxHashMap<IStr, V>,9}1011#[derive(Debug)]12pub struct LayeredHashMap<V>(Rc<LayeredHashMapInternals<V>>);1314impl<V> LayeredHashMap<V> {15 pub fn extend(self, new_layer: FxHashMap<IStr, V>) -> Self {16 match Rc::try_unwrap(self.0) {17 Ok(mut map) => {18 map.current.extend(new_layer);19 Self(Rc::new(map))20 }21 Err(this) => Self(Rc::new(LayeredHashMapInternals {22 parent: Some(Self(this)),23 current: new_layer,24 })),25 }26 }2728 pub fn get(&self, key: &IStr) -> Option<&V> {29 (self.0)30 .current31 .get(key)32 .or_else(|| self.0.parent.as_ref().and_then(|p| p.get(key)))33 }34}3536impl<V> Clone for LayeredHashMap<V> {37 fn clone(&self) -> Self {38 Self(self.0.clone())39 }40}4142impl<V> Default for LayeredHashMap<V> {43 fn default() -> Self {44 Self(Rc::new(LayeredHashMapInternals {45 parent: None,46 current: FxHashMap::default(),47 }))48 }49}