Add todo note

schala-lang/language/src/reduced_ast.rs

@@ -455,7 +455,7 @@ impl PrefixOp {
         let f = Box::new(Expr::Func(Func::BuiltIn(op)));
         Expr::Call { f, args: vec![arg.node().reduce(symbol_table)]}
       },
-      None => {
+      None => { //TODO need this for custom prefix ops
         Expr::UnimplementedSigilValue
       }
     }