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