At present, the #nserde(skip) attribute on a struct with a derive(DeRon) annotation would cause build warnings. You can see this by running cargo test in the project.

rning: this function depends on never type fallback being `()`
   --> tests/ron.rs:138:14
    |
138 |     #[derive(DeRon, SerRon, PartialEq, Debug)]
    |              ^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
    = help: specify the types explicitly
note: in edition 2024, the requirement `!: DeRon` will fail

From looking at the expanded macros, I think this is because in the generated code, type inference relies on the assignment of the local value to its corresponding struct field to know what the value of the type binding is. Because skip() skips this and replaces the value with Default:;default(), the resulting option type is initialized to the "lowest" possible type, Option<!>.

I think that makes the DeSer::de_ron() call to initialize the field values fall back to the DeSer impl for (), which triggers the compiler warning. Not 100% sure about that but either way, adding type annotations makes the warning go away!