derive_more_impl/
add_assign_like.rs

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}
derive_more_impl/add_assign_like.rs

derive_more_impl/
add_assign_like.rs
