You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parse_struct_attr.rs
    path of file: ./repos/irisia-gui/irisia-macros/src/derive_props/attrs
    
    the code of the file until where you have to start completion: use std::collections::HashSet;

use proc_macro2::{Ident, Span, TokenStream};
use quote::format_ident;
use syn::{
    meta::ParseNestedMeta,
    parse::{ParseStream, Parser},
    parse_quote,
    punctuated::Punctuated,
    token::Paren,
    Error, LitStr, Result, Token, Visibility,
};

use c
    
fn parse_watch(nested: ParseNestedMeta, fields: &[HandledField]) -> Result<DefaultWatch> {
    let mut default_watch = DefaultWatch {
        group_name: format_ident!("unchanged"),
        exclude: HashSet::new(),
    };

    if !nested.input.peek(Paren) {
        return Ok(default_watch);
    }

    nested.parse_nested_meta(|nested2| {
        let ident = nested2
            .path
            .get_ident()
            .ok_or_else(|| Error::new_spanned(&nested2.path, "expected identifier"))?;

        match ident.to_string().as_str() {
            "group" => default_watch.group_name = nested2.value()?.parse::<LitStr>()?.parse()?,
            "exclude" => insert_exclude(&mut default_watch.exclude, nested2.value()?)?,
            other => {
                return Err(Error::new_spanned(
                    ident,
                    format!("unrecognized option `{other}`"),
                ))
            }
        }
        Ok(())
    })?;

    for ex in default_watch.exclude.iter() {
        if !fields.iter().any(|field| field.ident == ex) {
            return Err(Error::new_spanned(
                ex,
                format!("cannot excluding unexisting field `{ex}`"),
            ));
        }
    }

    Ok(default_watch)
}