Would it be possible to optionally ignore uses of fields in derive macros when computing unused lints?
Real world scenario:
I have a few thousands lines of code with multiple structs that have #[derive(Debug)] slapped on them.
Sometimes I need to add a new field, so I go ahead and add it. I get missing field errors in constructors (or not if they are only constructed via #[derive(Deserialize)]!) but if I forget to also read those fields (which actually happened to me a few times) I have a bug that the compiler doesn't warn me about although it could.
Minimal example:
#[derive(Debug)]
struct Foo {
a: &'static str,
}
fn main() {
let foo = Foo {
a: "hello",
};
println!("{:?}", foo);
}
playground - see that the compiler doesn't warn about this
Edit: forgot to say that I'm also writing another crate where forgetting to read a field could cause vulnerabilities.
I wonder how hard would it be to get some crate-level attribute to turn this into a warning. Something like warn(field_only_read_in_derived_code) and probably also warn(field_only_read_in_derived_code(Debug)) to turn this on only for certain derives, Debug probably being the most common in practice.
Did something similar happen to you? Do you have a better idea what to do about it? I'd love to know!