feat: builtins env (WIP)

src/env.rs

@@ -8,7 +8,7 @@ use crate::{ir::Ir, ty::internal::Value};
 pub struct Env<K: Hash + Eq, V> {
     let_: Rc<LetEnv<V>>,
     with: Rc<With<K, V>>,
-    args: Vec<V>,
+    args: Rc<Vec<V>>,
     last: Option<Rc<Env<K, V>>>,
 }
 
@@ -42,11 +42,11 @@ impl<K: Hash + Eq + Clone, V: Clone> Env<K, V> {
     pub fn new(map: Vec<V>) -> Rc<Self> {
         Rc::new(Self {
             let_: LetEnv::new(map),
-            with: Rc::new(With {
+            with: With {
                 map: None,
                 last: None,
-            }),
-            args: Vec::new(),
+            }.into(),
+            args: Vec::new().into(),
             last: None,
         })
     }
@@ -70,7 +70,7 @@ impl<K: Hash + Eq + Clone, V: Clone> Env<K, V> {
     #[must_use]
     pub fn enter_arg(self: Rc<Self>, val: V) -> Rc<Self> {
         let mut args = self.args.clone();
-        args.push(val);
+        Rc::make_mut(&mut args).push(val);
         Rc::new(Self {
             let_: self.let_.clone(),
             with: self.with.clone(),