feat: less clone, avoid evaluating not depended thunk

src/ir/ctx.rs

@@ -9,7 +9,7 @@ use crate::{
 
 use super::{Dep, Func, Ir, LoadFunc, MaybeThunk, SccAnalyzer, SccNode, Thunk};
 
-#[derive(Clone, Copy, Unwrap)]
+#[derive(Clone, Copy, Unwrap, Debug)]
 pub enum Index {
     Thunk(usize),
     Func(usize),
@@ -169,9 +169,11 @@ impl DowngradeContext {
     }
 
     pub fn new_dep(&mut self, this: Index, dep: Dep) -> Result<()> {
+        #[cfg(debug_assertions)]
+        println!("{this:?} => {dep:?}");
         match this {
             Index::Thunk(idx) => {
-                if dep == Dep::Thunk(idx) {
+                if dep == Dep::Thunk(idx) && !matches!(self.thunks[idx].0, Ir::List(_)) {
                     return Err(Error::DowngradeError(
                         "infinite recursion encountered".into(),
                     ));