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