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use proc_macro2::{Ident, Span, TokenStream};
use quote::{quote, ToTokens};
use syn;
use darling::{ast, FromVariant, FromDeriveInput};
#[derive(Debug, FromDeriveInput)]
#[darling(attributes(wrap), supports(enum_any))]
struct EnumReceiver {
ident: Ident,
data: ast::Data<VariantReceiver, ()>,
c_enum: String,
}
impl ToTokens for EnumReceiver {
fn to_tokens(&self, tokens: &mut TokenStream) {
let EnumReceiver {
ref ident,
ref data,
ref c_enum,
} = *self;
let join_c_name_and_variant = |name: &str, variant: &str| {
Ident::new(&format!("{}_{}", &name, variant), Span::call_site())
};
let c_name = Ident::new(c_enum, Span::call_site());
let rust_name = ident;
let variants = data
.as_ref()
.take_enum()
.expect("should never be a struct");
let as_arms = variants
.iter()
.map(|v| {
let c_joined = join_c_name_and_variant(&c_name.to_string(), &v.c_variant);
let v_ident = &v.ident;
quote! {
#rust_name::#v_ident => #c_joined,
}
})
.collect::<Vec<_>>();
let try_from_arms = variants
.into_iter()
.map(|v| {
let c_joined = join_c_name_and_variant(&c_name.to_string(), &v.c_variant);
let v_ident = &v.ident;
quote! {
#c_joined => Ok(#rust_name::#v_ident),
}
})
.collect::<Vec<_>>();
tokens.extend(quote! {
impl #rust_name {
pub fn as_c(&self) -> #c_name {
match *self {
#(#as_arms)*
}
}
}
impl ::std::convert::TryFrom<#c_name> for #rust_name {
type Error = NvmlError;
fn try_from(data: #c_name) -> Result<Self, Self::Error> {
match data {
#(#try_from_arms)*
_ => Err(NvmlError::UnexpectedVariant(data)),
}
}
}
});
}
}
#[derive(Debug, FromVariant)]
#[darling(attributes(wrap))]
struct VariantReceiver {
ident: Ident,
c_variant: String
}
#[proc_macro_derive(EnumWrapper, attributes(wrap))]
pub fn wrapcenum_derive(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let ast = syn::parse(input).unwrap();
let receiver = EnumReceiver::from_derive_input(&ast).unwrap();
quote!(#receiver).into()
}