1 files changed, 34 insertions, 0 deletions
diff --git a/src/macros/enum_count.rs b/src/macros/enum_count.rs
new file mode 100644
index 0000000..b9e6aaa
--- /dev/null
+++ b/src/macros/enum_count.rs
@@ -0,0 +1,34 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{Data, DeriveInput};
+
+use crate::helpers::variant_props::HasStrumVariantProperties;
+use crate::helpers::{non_enum_error, HasTypeProperties};
+
+pub(crate) fn enum_count_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
+    let n = match &ast.data {
+        Data::Enum(v) => v.variants.iter().try_fold(0usize, |acc, v| {
+            if v.get_variant_properties()?.disabled.is_none() {
+                Ok::<usize, syn::Error>(acc + 1usize)
+            } else {
+                Ok::<usize, syn::Error>(acc)
+            }
+        })?,
+        _ => return Err(non_enum_error()),
+    };
+    let type_properties = ast.get_type_properties()?;
+    let strum_module_path = type_properties.crate_module_path();
+
+    // Used in the quasi-quotation below as `#name`
+    let name = &ast.ident;
+
+    // Helper is provided for handling complex generic types correctly and effortlessly
+    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
+
+    Ok(quote! {
+        // Implementation
+        impl #impl_generics #strum_module_path::EnumCount for #name #ty_generics #where_clause {
+            const COUNT: usize = #n;
+        }
+    })
+}