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use proc_macro2::{Span, TokenStream};
use quote::{format_ident, quote};
use syn::{Data, DeriveInput, Fields, LitInt};
pub fn expand(input: DeriveInput) -> TokenStream {
let ty = input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut result_token = quote!();
match &input.data {
Data::Struct(data) => match &data.fields {
syn::Fields::Named(named) => {
let mut let_token = quote!();
let mut inner_token = quote!();
for field in named.named.iter() {
let field_ident = &field.ident;
let_token = quote! {
#let_token
let #field_ident = self.#field_ident.get_token_stream();
};
inner_token = quote! {
#inner_token
#field_ident: ##field_ident,
};
}
result_token = quote! {
#let_token
quote!(#ty {
#inner_token
})
};
}
syn::Fields::Unnamed(unamed) => {
let mut let_token = quote!();
let mut inner_token = quote!();
for (index, _field) in unamed.unnamed.iter().enumerate() {
let field_ident = format_ident!("field_{}", index);
let index = LitInt::new(&index.to_string(), Span::call_site());
let value_token = quote!(self. #index.get_token_stream());
let_token = quote! {
#let_token
let #field_ident = #value_token;
};
inner_token = quote! {
#inner_token
##field_ident,
};
}
result_token = quote! {
#let_token
quote!(#ty (
#inner_token
))
};
}
syn::Fields::Unit => {
result_token = quote! {
quote!(#ty)
};
}
},
Data::Enum(enumer) => {
for variant in &enumer.variants {
let variant_token;
let variant_ident = &variant.ident;
let mut pat = quote!();
match &variant.fields {
Fields::Named(named) => {
let mut let_token = quote!();
let mut inner_token = quote!();
for field in named.named.iter() {
let field_ident = &field.ident;
pat = quote! {#pat #field_ident,};
let_token = quote! {
#let_token
let #field_ident = #field_ident.get_token_stream();
};
inner_token = quote! {
#inner_token
#field_ident: ##field_ident,
};
}
pat = quote! {{#pat}};
variant_token = quote! {
#let_token
quote!(#ty :: #variant_ident {
#inner_token
})
};
}
Fields::Unnamed(unamed) => {
let mut let_token = quote!();
let mut inner_token = quote!();
for (index, _field) in unamed.unnamed.iter().enumerate() {
let field_ident = format_ident!("field_{}", index);
pat = quote! {#pat #field_ident,};
let value_token = quote!(#field_ident.get_token_stream());
let_token = quote! {
#let_token
let #field_ident = #value_token;
};
inner_token = quote! {
#inner_token
##field_ident,
};
}
pat = quote! {(#pat)};
variant_token = quote! {
#let_token
quote!(#ty :: #variant_ident (
#inner_token
))
};
}
Fields::Unit => {
pat = quote!();
variant_token = quote! {
quote!(#ty :: #variant_ident)
};
}
}
result_token = quote! {
#result_token
#ty ::#variant_ident #pat => {
#variant_token
}
}
}
result_token = quote! {
match self {
#result_token
}
};
}
Data::Union(_) => unimplemented!(),
}
quote! {
impl #impl_generics GetTokenStream for #ty #ty_generics #where_clause {
fn get_token_stream(self) -> TokenStream {
#result_token
}
fn get_self_ty() -> TokenStream {
quote!(#ty)
}
}
}
}