Use fold.

src/func/hashing.rs

@@ -124,10 +124,7 @@ pub fn calc_fn_hash(fn_name: &str, num: usize) -> u64 {
 pub fn calc_fn_params_hash(params: impl Iterator<Item = TypeId>) -> u64 {
     let s = &mut get_hasher();
     let mut len = 0;
-    params.for_each(|t| {
-        len += 1;
-        t.hash(s);
-    });
+    params.inspect(|_| len += 1).for_each(|t| t.hash(s));
     len.hash(s);
     s.finish()
 }