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use crate::add_helpers::{struct_exprs, tuple_exprs};
use crate::utils::{add_extra_ty_param_bound_op, named_to_vec, unnamed_to_vec};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use syn::{Data, DeriveInput, Fields};
pub fn expand(input: &DeriveInput, trait_name: &str) -> TokenStream {
let trait_ident = format_ident!("{trait_name}");
let method_name = trait_name.trim_end_matches("Assign").to_lowercase();
let method_ident = format_ident!("{method_name}_assign");
let input_type = &input.ident;
let generics = add_extra_ty_param_bound_op(&input.generics, &trait_ident);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let exprs = match input.data {
Data::Struct(ref data_struct) => match data_struct.fields {
Fields::Unnamed(ref fields) => {
tuple_exprs(&unnamed_to_vec(fields), &method_ident)
}
Fields::Named(ref fields) => {
struct_exprs(&named_to_vec(fields), &method_ident)
}
_ => panic!("Unit structs cannot use derive({trait_name})"),
},
_ => panic!("Only structs can use derive({trait_name})"),
};
quote! {
#[automatically_derived]
impl #impl_generics ::core::ops::#trait_ident for #input_type #ty_generics #where_clause {
#[inline]
fn #method_ident(&mut self, rhs: #input_type #ty_generics) {
#( #exprs; )*
}
}
}
}
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