feat: lookup at downgrade time

works, but leaks memory

src/ty/internal/func.rs

@@ -2,15 +2,13 @@ use std::cell::Cell;
 
 use gc_arena::lock::{GcRefLock, RefLock};
 use gc_arena::{Collect, Gc, Mutation};
-use hashbrown::HashMap;
-use itertools::Itertools;
 
 use crate::bytecode::Func as BFunc;
 use crate::env::VmEnv;
 use crate::error::Result;
 use crate::ir;
 use crate::jit::JITFunc;
-use crate::ty::internal::{Thunk, Value};
+use crate::ty::internal::Value;
 use crate::vm::VM;
 
 #[derive(Debug, Clone, Collect)]
@@ -75,45 +73,7 @@ impl<'gc> Func<'gc> {
         vm: &'gc VM<'gc>,
         mc: &Mutation<'gc>,
     ) -> Result<Value<'gc>> {
-        use Param::*;
-
-        let mut env = self.env;
-        env = match self.func.param.clone() {
-            Ident(ident) => env.enter_arg(ident, arg, mc),
-            Formals {
-                formals,
-                ellipsis,
-                alias,
-            } => {
-                let arg = arg.unwrap_attr_set();
-                let mut new = HashMap::with_capacity(formals.len() + alias.iter().len());
-                if !ellipsis
-                    && arg
-                        .as_inner()
-                        .iter()
-                        .map(|(k, _)| k)
-                        .sorted()
-                        .ne(formals.iter().map(|(k, _)| k).sorted())
-                {
-                    todo!()
-                }
-                for (formal, default) in formals {
-                    let arg = arg
-                        .select(formal)
-                        .or_else(|| {
-                            default
-                                .map(|idx| Value::Thunk(Thunk::new(vm.get_thunk(idx), mc)))
-                        })
-                        .unwrap();
-                    new.insert(formal, arg);
-                }
-                if let Some(alias) = alias {
-                    new.insert(alias, Value::AttrSet(arg));
-                }
-                env.enter_let(Gc::new(mc, new), mc)
-            }
-        };
-
+        let env = self.env.enter_arg(arg, mc);
         let compiled = self
             .compiled
             .borrow_mut(mc)