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use quote::{format_ident, quote};
pub fn render(input: &syn::DeriveInput, data: &syn::DataEnum) -> proc_macro2::TokenStream {
let name = &input.ident;
let variants = data
.variants
.iter()
.map(|variant| {
let variant_ident = &variant.ident;
let (is_empty, variant_fields_inner, variant_fields_outer) = match &variant.fields {
syn::Fields::Unit => (true, quote!(), quote!()),
syn::Fields::Named(fields) => {
let inner = fields
.named
.iter()
.map(|field| {
let field_ident = &field.ident;
quote!(#field_ident)
})
.collect::<Vec<_>>();
(
inner.is_empty(),
quote!(#(#inner = #inner, )*),
quote!({ #(#inner, )* }),
)
}
syn::Fields::Unnamed(fields) => {
let inner = fields
.unnamed
.iter()
.enumerate()
.map(|(i, _)| {
let field_ident = format_ident!("p{}", i);
quote!(#field_ident)
})
.collect::<Vec<_>>();
(
inner.is_empty(),
quote!(#(#inner, )*),
quote!((#(#inner, )*)),
)
}
};
if is_empty {
return quote! {
Self::#variant_ident #variant_fields_outer => {
write!(f, "{}", stringify!(#variant_ident))
}
};
}
quote! {
Self::#variant_ident #variant_fields_outer => {
write!(f, "{}", #variant_fields_inner)
}
}
})
.collect::<Vec<_>>();
return quote! {
impl std::fmt::Display for #name {
fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
return match self {
#(#variants,)*
};
}
}
};
}