feat(gc): WIP

src/env.rs

@@ -11,6 +11,7 @@ pub struct Env<'gc, K: Hash + Eq + Collect<'gc>, V: Collect<'gc>> {
     let_: Gc<'gc, LetEnv<'gc, V>>,
     with: Gc<'gc, With<'gc, K, V>>,
     args: Vec<V>,
+    gc_alloced: Vec<Gc<'gc, V>>,
     last: Option<Gc<'gc, Env<'gc, K, V>>>,
 }
 
@@ -59,16 +60,17 @@ impl<'gc, K: Hash + Eq + Clone + Collect<'gc>, V: Clone + Collect<'gc>> Env<'gc,
                     },
                 ),
                 args: Vec::new(),
+                gc_alloced: Vec::new(),
                 last: None,
             },
         )
     }
 
-    pub fn lookup_arg(&self, level: usize) -> V {
-        self.args[self.args.len() - level - 1].clone()
+    pub fn lookup_arg(&self, level: usize) -> &V {
+        &self.args[self.args.len() - level - 1]
     }
 
-    pub fn lookup_let(&self, level: usize, idx: usize) -> V {
+    pub fn lookup_let(&self, level: usize, idx: usize) -> &V {
         self.let_.lookup(level, idx)
     }
 
@@ -90,6 +92,7 @@ impl<'gc, K: Hash + Eq + Clone + Collect<'gc>, V: Clone + Collect<'gc>> Env<'gc,
                 let_: self.let_,
                 with: self.with,
                 last: Some(self),
+                gc_alloced: Vec::new(),
                 args
             },
         )
@@ -107,6 +110,7 @@ impl<'gc, K: Hash + Eq + Clone + Collect<'gc>, V: Clone + Collect<'gc>> Env<'gc,
                 let_: self.let_.enter_let(map, mc),
                 with: self.with,
                 args: self.args.clone(),
+                gc_alloced: Vec::new(),
                 last: Some(self),
             },
         )
@@ -124,11 +128,19 @@ impl<'gc, K: Hash + Eq + Clone + Collect<'gc>, V: Clone + Collect<'gc>> Env<'gc,
                 let_: self.let_,
                 with: self.with.enter(map, mc),
                 args: self.args.clone(),
+                gc_alloced: Vec::new(),
                 last: Some(self),
             },
         )
     }
 
+    #[inline]
+    pub fn alloc_gc(&mut self, val: V, mc: &Mutation<'gc>) -> &'gc V {
+        let gc = Gc::new(mc, val);
+        self.gc_alloced.push(gc);
+        gc.as_ref()
+    }
+
     pub fn leave(&self) -> Gc<'gc, Self> {
         self.last.unwrap()
     }
@@ -145,13 +157,13 @@ impl<'gc, V: Clone + Collect<'gc>> LetEnv<'gc, V> {
         )
     }
 
-    pub fn lookup(&self, level: usize, idx: usize) -> V {
+    pub fn lookup(&self, level: usize, idx: usize) -> &V {
         let mut cur = self;
         for _ in 0..level {
             let last = cur.last.unwrap();
             cur = last.as_ref();
         }
-        cur.map[idx].clone()
+        &cur.map[idx]
     }
 
     pub fn enter_let(