67 lines
2.1 KiB
Rust
67 lines
2.1 KiB
Rust
use proc_macro::TokenStream;
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use proc_macro2 as pm2;
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use quote::ToTokens;
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use syn::spanned::Spanned;
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use crate::common::{add_trait_bounds, destructure, pos_field_name};
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pub fn derive(input: TokenStream) -> TokenStream {
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// Parse the input tokens into a syntax tree
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let input = parse_macro_input!(input as syn::DeriveInput);
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let e_generics = add_trait_bounds(input.generics, parse_quote!(orchid_api_traits::Decode));
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let (e_impl_generics, e_ty_generics, e_where_clause) = e_generics.split_for_impl();
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let name = input.ident;
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let encode = encode_body(&input.data);
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let expanded = quote! {
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impl #e_impl_generics orchid_api_traits::Encode for #name #e_ty_generics #e_where_clause {
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fn encode<W: std::io::Write + ?Sized>(&self, write: &mut W) { #encode }
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}
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};
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TokenStream::from(expanded)
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}
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fn encode_body(data: &syn::Data) -> Option<pm2::TokenStream> {
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match data {
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syn::Data::Union(_) => panic!("Unions can't be deserialized"),
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syn::Data::Struct(str) => {
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let dest = destructure(&str.fields)?;
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let body = encode_items(&str.fields);
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Some(quote! {
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let Self #dest = &self;
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#body
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})
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},
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syn::Data::Enum(en) => {
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let options = en.variants.iter().enumerate().map(|(i, v @ syn::Variant { ident, .. })| {
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let dest = destructure(&v.fields).unwrap_or_default();
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let body = encode_items(&v.fields);
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quote! {
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Self::#ident #dest => {
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(#i as u64).encode(write);
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#body
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}
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}
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});
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Some(quote! {
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match self {
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#(#options)*
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_ => unreachable!("Autogenerated encode impl for all possible variants"),
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}
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})
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},
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}
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}
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fn encode_names<T: ToTokens>(names: impl Iterator<Item = T>) -> pm2::TokenStream {
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quote! { #( #names .encode(write); )* }
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}
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fn encode_items(fields: &syn::Fields) -> Option<pm2::TokenStream> {
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match fields {
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syn::Fields::Unit => None,
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syn::Fields::Named(_) => Some(encode_names(fields.iter().map(|f| f.ident.as_ref().unwrap()))),
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syn::Fields::Unnamed(un) =>
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Some(encode_names((0..fields.len()).map(|i| pos_field_name(i, un.span())))),
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}
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}
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