1 use proc_macro2::TokenStream; 2 use quote::quote; 3 use syn::{Data, DeriveInput}; 4 5 use crate::helpers::{non_enum_error, HasTypeProperties}; 6 enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream>7pub(crate) fn enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream> { 8 let n = match &ast.data { 9 Data::Enum(v) => v.variants.len(), 10 _ => return Err(non_enum_error()), 11 }; 12 let type_properties = ast.get_type_properties()?; 13 let strum_module_path = type_properties.crate_module_path(); 14 15 // Used in the quasi-quotation below as `#name` 16 let name = &ast.ident; 17 18 // Helper is provided for handling complex generic types correctly and effortlessly 19 let (impl_generics, ty_generics, where_clause) = 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