1 use proc_macro2::{Span, TokenStream};
2 use quote::quote;
3 use syn::parse_macro_input;
4
run( attr: proc_macro::TokenStream, item: proc_macro::TokenStream, ) -> proc_macro::TokenStream5 pub fn run(
6 attr: proc_macro::TokenStream,
7 item: proc_macro::TokenStream,
8 ) -> proc_macro::TokenStream {
9 expand_variants(
10 &parse_macro_input!(attr as syn::LitInt),
11 parse_macro_input!(item as syn::ItemEnum),
12 )
13 .unwrap_or_else(syn::Error::into_compile_error)
14 .into()
15 }
16
expand_variants(count: &syn::LitInt, mut ty: syn::ItemEnum) -> syn::Result<TokenStream>17 fn expand_variants(count: &syn::LitInt, mut ty: syn::ItemEnum) -> syn::Result<TokenStream> {
18 let count = count
19 .base10_digits()
20 .parse::<usize>()
21 .map_err(|_| syn::Error::new(count.span(), "expected unsigned integer"))?;
22
23 ty.variants = (0..count)
24 .map(|index| syn::Variant {
25 attrs: Vec::new(),
26 ident: syn::Ident::new(&format!("V{index}"), Span::call_site()),
27 fields: syn::Fields::Unit,
28 discriminant: None,
29 })
30 .collect();
31
32 Ok(quote!(#ty))
33 }
34