derive_more_impl/
sum_like.rs

1use crate::utils::{
2    add_extra_ty_param_bound, add_extra_where_clauses, MultiFieldData, State,
3};
4use proc_macro2::TokenStream;
5use quote::{format_ident, quote};
6use syn::{DeriveInput, Result};
7
8pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
9    let state = State::new(input, trait_name, trait_name.to_lowercase())?;
10    let multi_field_data = state.enabled_fields_data();
11    let MultiFieldData {
12        input_type,
13        field_types,
14        trait_path,
15        method_ident,
16        ..
17    } = multi_field_data.clone();
18
19    let op_trait_name = if trait_name == "Sum" { "Add" } else { "Mul" };
20    let op_trait_ident = format_ident!("{op_trait_name}");
21    let op_path = quote! { derive_more::core::ops::#op_trait_ident };
22    let op_method_ident = format_ident!("{}", op_trait_name.to_lowercase());
23    let has_type_params = input.generics.type_params().next().is_none();
24    let generics = if has_type_params {
25        input.generics.clone()
26    } else {
27        let (_, ty_generics, _) = input.generics.split_for_impl();
28        let generics = add_extra_ty_param_bound(&input.generics, trait_path);
29        let operator_where_clause = quote! {
30            where #input_type #ty_generics: #op_path<Output=#input_type #ty_generics>
31        };
32        add_extra_where_clauses(&generics, operator_where_clause)
33    };
34    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
35
36    let initializers: Vec<_> = field_types
37        .iter()
38        .map(|field_type| {
39            quote! { #trait_path::#method_ident(derive_more::core::iter::empty::<#field_type>()) }
40        })
41        .collect();
42    let identity = multi_field_data.initializer(&initializers);
43
44    Ok(quote! {
45        #[automatically_derived]
46        impl #impl_generics #trait_path for #input_type #ty_generics #where_clause {
47            #[inline]
48            fn #method_ident<I: derive_more::core::iter::Iterator<Item = Self>>(iter: I) -> Self {
49                iter.fold(#identity, #op_path::#op_method_ident)
50            }
51        }
52    })
53}
derive_more_impl/sum_like.rs

derive_more_impl/
sum_like.rs
