1use crate::add_helpers::{struct_exprs, tuple_exprs};
2use crate::utils::{add_extra_ty_param_bound_op, named_to_vec, unnamed_to_vec};
3use proc_macro2::TokenStream;
4use quote::{format_ident, quote};
5use syn::{Data, DeriveInput, Fields};
6
7pub fn expand(input: &DeriveInput, trait_name: &str) -> TokenStream {
8 let trait_ident = format_ident!("{trait_name}");
9 let method_name = trait_name.trim_end_matches("Assign").to_lowercase();
10 let method_ident = format_ident!("{method_name}_assign");
11 let input_type = &input.ident;
12
13 let generics = add_extra_ty_param_bound_op(&input.generics, &trait_ident);
14 let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
15
16 let exprs = match input.data {
17 Data::Struct(ref data_struct) => match data_struct.fields {
18 Fields::Unnamed(ref fields) => {
19 tuple_exprs(&unnamed_to_vec(fields), &method_ident)
20 }
21 Fields::Named(ref fields) => {
22 struct_exprs(&named_to_vec(fields), &method_ident)
23 }
24 _ => panic!("Unit structs cannot use derive({trait_name})"),
25 },
26
27 _ => panic!("Only structs can use derive({trait_name})"),
28 };
29
30 quote! {
31 #[automatically_derived]
32 impl #impl_generics derive_more::core::ops::#trait_ident
33 for #input_type #ty_generics #where_clause {
34 #[inline]
35 #[track_caller]
36 fn #method_ident(&mut self, rhs: #input_type #ty_generics) {
37 #( #exprs; )*
38 }
39 }
40 }
41}
42