mod content_hash; extern crate proc_macro; use quote::quote;use syn::DeriveInput;use syn::parse_macro_input; /// Derive macro generating an impl of the trait `ContentHash`.////// Derives the `ContentHash` trait for a struct by calling `ContentHash::hash`/// on each of the struct members in the order that they're declared. All/// members of the struct must implement the `ContentHash` trait.#[proc_macro_derive(ContentHash)]pub fn derive_content_hash(input: proc_macro::TokenStream) -> proc_macro::TokenStream {    let input = parse_macro_input!(input as DeriveInput);     // The name of the struct.    let name = &input.ident;     // Generate an expression to hash each of the fields in the struct.    let hash_impl = content_hash::generate_hash_impl(&input.data);     // Handle structs and enums with generics.    let generics = content_hash::add_trait_bounds(input.generics);    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();     let expanded = quote! {        #[automatically_derived]        impl #impl_generics ::jj_lib::content_hash::ContentHash for #name #ty_generics        #where_clause {            fn hash(&self, state: &mut impl digest::Update) {                #hash_impl            }        }    };    expanded.into()}