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use crate::utils::{
add_extra_ty_param_bound, add_extra_where_clauses, MultiFieldData, State,
};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use syn::{DeriveInput, Result};
pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
let state = State::new(input, trait_name, trait_name.to_lowercase())?;
let multi_field_data = state.enabled_fields_data();
let MultiFieldData {
input_type,
field_types,
trait_path,
method_ident,
..
} = multi_field_data.clone();
let op_trait_name = if trait_name == "Sum" { "Add" } else { "Mul" };
let op_trait_ident = format_ident!("{op_trait_name}");
let op_path = quote! { ::core::ops::#op_trait_ident };
let op_method_ident = format_ident!("{}", op_trait_name.to_lowercase());
let has_type_params = input.generics.type_params().next().is_none();
let generics = if has_type_params {
input.generics.clone()
} else {
let (_, ty_generics, _) = input.generics.split_for_impl();
let generics = add_extra_ty_param_bound(&input.generics, trait_path);
let operator_where_clause = quote! {
where #input_type #ty_generics: #op_path<Output=#input_type #ty_generics>
};
add_extra_where_clauses(&generics, operator_where_clause)
};
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let initializers: Vec<_> = field_types
.iter()
.map(|field_type| {
quote! { #trait_path::#method_ident(::core::iter::empty::<#field_type>()) }
})
.collect();
let identity = multi_field_data.initializer(&initializers);
Ok(quote! {
#[automatically_derived]
impl #impl_generics #trait_path for #input_type #ty_generics #where_clause {
#[inline]
fn #method_ident<I: ::core::iter::Iterator<Item = Self>>(iter: I) -> Self {
iter.fold(#identity, #op_path::#op_method_ident)
}
}
})
}
|
