1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::{Data, DeriveInput};
4
5use crate::helpers::{non_enum_error, HasTypeProperties};
6
7pub(crate) fn enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
8 let n: usize = match &ast.data {
9 Data::Enum(v: &DataEnum) => v.variants.len(),
10 _ => return Err(non_enum_error()),
11 };
12 let type_properties: StrumTypeProperties = ast.get_type_properties()?;
13 let strum_module_path: Path = type_properties.crate_module_path();
14
15 // Used in the quasi-quotation below as `#name`
16 let name: &Ident = &ast.ident;
17
18 // Helper is provided for handling complex generic types correctly and effortlessly
19 let (impl_generics: ImplGenerics<'_>, ty_generics: TypeGenerics<'_>, where_clause: Option<&WhereClause>) = ast.generics.split_for_impl();
20
21 Ok(quote! {
22 // Implementation
23 impl #impl_generics #strum_module_path::EnumCount for #name #ty_generics #where_clause {
24 const COUNT: usize = #n;
25 }
26 })
27}
28