diff --git a/lang/src/son.rs b/lang/src/son.rs
index a55328d..a52d380 100644
--- a/lang/src/son.rs
+++ b/lang/src/son.rs
@@ -19,7 +19,6 @@ use {
     },
     alloc::{string::String, vec::Vec},
     core::{
-        any::Any,
         assert_matches::debug_assert_matches,
         cell::{Cell, RefCell},
         fmt::{self, Debug, Display, Write},
@@ -1878,7 +1877,21 @@ impl Nodes {
                 false
             }
             Kind::Join => false,
-            Kind::Stre => self[user].inputs[3] != val,
+            Kind::Stre => {
+                debug_assert_eq!(
+                    self[user].inputs[4..]
+                        .iter()
+                        .filter(|&&v| self[v].kind != Kind::Load)
+                        .copied()
+                        .collect::<Vec<_>>(),
+                    vec![]
+                );
+                debug_assert_matches!(
+                    self[self[user].inputs[3]].kind,
+                    Kind::Stre | Kind::Mem | Kind::Phi
+                );
+                self[user].inputs.iter().position(|&v| v == val).is_some_and(|v| v < 3)
+            }
             Kind::Load => self[user].inputs[2] != val,
             _ => self[user].inputs[0] != val || self[user].inputs[1..].contains(&val),
         }
@@ -4422,8 +4435,8 @@ impl<'a> Codegen<'a> {
 
     fn compute_signature(&mut self, func: &mut ty::Func, pos: Pos, args: &[Expr]) -> Option<Sig> {
         let Func { file, expr, sig, .. } = self.tys.ins.funcs[*func];
-        let fast = self.files[file.index()].clone();
-        let &Expr::Closure { args: cargs, ret, .. } = expr.get(&fast) else {
+        let fast = &self.files[file.index()];
+        let &Expr::Closure { args: cargs, ret, .. } = expr.get(fast) else {
             unreachable!();
         };