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extern crate proc_macro;
use proc_macro2::TokenStream;
use quote::{quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{
parse_macro_input, parse_quote, Data, DeriveInput, Fields, GenericParam, Generics, Index,
};
#[proc_macro_derive(DeepSizeOf)]
pub fn derive_deep_size(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let name = input.ident;
let generics = add_trait_bounds(input.generics);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let sum = deepsize_sum(&input.data);
let expanded = quote! {
impl #impl_generics ::deepsize::DeepSizeOf for #name #ty_generics #where_clause {
fn deep_size_of_children(&self, context: &mut ::deepsize::Context) -> usize {
#sum
}
}
};
proc_macro::TokenStream::from(expanded)
}
fn add_trait_bounds(mut generics: Generics) -> Generics {
for param in &mut generics.params {
if let GenericParam::Type(ref mut type_param) = *param {
type_param.bounds.push(parse_quote!(::deepsize::DeepSizeOf));
}
}
generics
}
fn deepsize_sum(data: &Data) -> TokenStream {
match *data {
Data::Struct(ref data) => {
match data.fields {
Fields::Named(ref fields) => {
let recurse = fields.named.iter().map(|f| {
let name = &f.ident;
quote_spanned! {f.span()=>
::deepsize::DeepSizeOf::deep_size_of_children(&self.#name, context)
}
});
quote! {
0 #(+ #recurse)*
}
}
Fields::Unnamed(ref fields) => {
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let index = Index::from(i);
quote_spanned! {f.span()=>
::deepsize::DeepSizeOf::deep_size_of_children(&self.#index, context)
}
});
quote! {
0 #(+ #recurse)*
}
}
Fields::Unit => {
quote!(0)
}
}
}
Data::Enum(_) | Data::Union(_) => unimplemented!(),
}
}