feat: partial func (WIP)

src/env.rs

@@ -4,7 +4,7 @@ use std::rc::{Rc, Weak};
 use ecow::EcoString;
 use hashbrown::HashMap;
 
-use crate::error::{Error, Result};
+use crate::error::Result;
 use crate::stack::Stack;
 use crate::ty::internal::Value;
 
@@ -48,15 +48,14 @@ impl Env {
         }
     }
 
-    pub fn enter_cache_level<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
+    pub fn enter_cache_level<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> (T, HashMap<usize, Value>) {
         self.cache.push(HashMap::new());
         let ret = f(self);
-        self.cache.pop();
-        ret
+        (ret, self.cache.pop().unwrap())
     }
 
-    pub fn pop_cache_level(&mut self) {
-        self.cache.pop();
+    pub fn pop_cache_level(&mut self) -> HashMap<usize, Value> {
+        self.cache.pop().unwrap()
     }
 
     pub fn insert_cache(&mut self, idx: usize, val: Value) {