1 use proc_macro2::TokenStream;
2 use quote::quote;
3 use syn::{Data, DeriveInput};
4
5 use crate::helpers::variant_props::HasStrumVariantProperties;
6 use crate::helpers::{non_enum_error, HasTypeProperties};
7
enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream>8 pub(crate) fn enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
9 let n = match &ast.data {
10 Data::Enum(v) => v.variants.iter().try_fold(0usize, |acc, v| {
11 if v.get_variant_properties()?.disabled.is_none() {
12 Ok::<usize, syn::Error>(acc + 1usize)
13 } else {
14 Ok::<usize, syn::Error>(acc)
15 }
16 })?,
17 _ => return Err(non_enum_error()),
18 };
19 let type_properties = ast.get_type_properties()?;
20 let strum_module_path = type_properties.crate_module_path();
21
22 // Used in the quasi-quotation below as `#name`
23 let name = &ast.ident;
24
25 // Helper is provided for handling complex generic types correctly and effortlessly
26 let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
27
28 Ok(quote! {
29 // Implementation
30 impl #impl_generics #strum_module_path::EnumCount for #name #ty_generics #where_clause {
31 const COUNT: usize = #n;
32 }
33 })
34 }
35