src/lib.rs


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use proc_macro::TokenStream;
use quote::quote;
use syn::{parse, ItemStruct};

#[proc_macro_derive(Serialize)]
pub fn derive_serialize(item: TokenStream) -> TokenStream {
    let ast: ItemStruct = parse(item).unwrap();
    let name = ast.ident;

    let serializers = ast.fields.iter().map(|field| {
        let field_name = field.ident.as_ref().expect("should be a names struct");

        quote!(
            self.#field_name.serialize(w)?;
        )
    });

    quote!(
        impl Serialize for #name {
            fn serialize<W: std::io::Write>(&self, w: &mut W) -> Result<()> {
                #(#serializers) *

                Ok(())
            }
        }
    )
    .into()
}