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#![warn(missing_docs, rust_2018_idioms, broken_intra_doc_links)]
#[allow(unused_extern_crates)]
extern crate proc_macro;
use proc_macro2::{Ident, TokenStream};
use quote::{format_ident, quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{
parse_macro_input, parse_quote, Data, DeriveInput, Fields, GenericParam, Generics, Index,
};
#[proc_macro_derive(ShallowCopy)]
pub fn derive_shallow_copy(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 copy = fields(&input.data, &name);
proc_macro::TokenStream::from(quote! {
impl #impl_generics evmap::shallow_copy::ShallowCopy for #name #ty_generics #where_clause {
unsafe fn shallow_copy(&self) -> std::mem::ManuallyDrop<Self> {
#copy
}
}
})
}
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!(evmap::shallow_copy::ShallowCopy));
}
}
generics
}
fn fields(data: &Data, type_name: &Ident) -> TokenStream {
match data {
Data::Struct(data) => match &data.fields {
Fields::Named(fields) => {
let recurse = fields.named.iter().map(|f| {
let name = &f.ident;
quote_spanned! {f.span()=>
#name: std::mem::ManuallyDrop::into_inner(
evmap::shallow_copy::ShallowCopy::shallow_copy(&self.#name)
)
}
});
quote! {
std::mem::ManuallyDrop::new(Self { #(#recurse,)* })
}
}
Fields::Unnamed(fields) => {
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let index = Index::from(i);
quote_spanned! {f.span()=>
std::mem::ManuallyDrop::into_inner(
evmap::shallow_copy::ShallowCopy::shallow_copy(&self.#index)
)
}
});
quote! {
std::mem::ManuallyDrop::new(#type_name(#(#recurse,)*))
}
}
Fields::Unit => quote!(std::mem::ManuallyDrop::new(#type_name)),
},
Data::Enum(data) => {
let recurse = data.variants.iter().map(|f| {
let (names, fields) = match &f.fields {
Fields::Named(fields) => {
let field_names = f.fields.iter().map(|field| {
let ident = field.ident.as_ref().unwrap();
quote_spanned! {
field.span()=> #ident
}
});
let recurse = fields.named.iter().map(|f| {
let name = f.ident.as_ref().unwrap();
quote_spanned! {f.span()=>
#name: std::mem::ManuallyDrop::into_inner(
evmap::shallow_copy::ShallowCopy::shallow_copy(#name)
)
}
});
(quote! { {#(#field_names,)*} }, quote! { { #(#recurse,)* } })
}
Fields::Unnamed(fields) => {
let field_names = f.fields.iter().enumerate().map(|(i, field)| {
let ident = format_ident!("x{}", i);
quote_spanned! {
field.span()=> #ident
}
});
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let ident = format_ident!("x{}", i);
quote_spanned! {f.span()=>
std::mem::ManuallyDrop::into_inner(
evmap::shallow_copy::ShallowCopy::shallow_copy(#ident)
)
}
});
(quote! { (#(#field_names,)*) }, quote! { (#(#recurse,)*) })
}
Fields::Unit => (quote!(), quote!()),
};
let name = &f.ident;
quote_spanned! {f.span()=>
#type_name::#name#names => std::mem::ManuallyDrop::new(#type_name::#name#fields)
}
});
quote! {
match self {
#(#recurse,)*
}
}
}
Data::Union(_) => unimplemented!("Unions are not supported"),
}
}