layer: usize -> u8

fix-ir/src/lib.rs

@@ -73,7 +73,7 @@ pub enum MaybeThunk {
     Str(StringId),
     Path(StringId),
     Thunk(ThunkId),
-    Arg { layer: usize },
+    Arg { layer: u8 },
     Builtin(BuiltinId),
     Builtins,
     ReplBinding(StringId),
@@ -172,7 +172,7 @@ pub enum Ir<'ir, Ref> {
         thunks: Vec<'ir, (ThunkId, Ref)>,
     },
     Arg {
-        layer: usize,
+        layer: u8,
     },
     Call {
         func: Ref,