Squash some warnings

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/compile/name.rs

@@ -142,7 +142,7 @@ impl Visit for CollectNames<'_, '_> {
                 self.visit_expr(&i.expr);
                 self.visit_expr(&i.index);
             }
-            Expr::Fun(f) => { /* no-op */ }
+            Expr::Fun(_) => { /* no-op */ }
             Expr::Base(b) => self.visit_base_expr(b),
         }
     }