fix enum discriminants not being included in the hash

hash2_derive/src/lib.rs

@@ -35,6 +35,11 @@ pub fn derive_hash2(input: TokenStream) -> TokenStream {
             }
         }
         Data::Enum(data) => {
+            // Hash the discriminant first to ensure different variants hash differently
+            let discriminant_hash = quote! {
+                core::mem::discriminant(self).hash(state);
+            };
+            
             let variants = data.variants.iter().map(|variant| {
                 let variant_name = &variant.ident;
                 match &variant.fields {
@@ -69,8 +74,9 @@ pub fn derive_hash2(input: TokenStream) -> TokenStream {
                     }
                 }
             });
-            
+           
             quote! {
+                #discriminant_hash
                 match self {
                     #(#variants)*
                 }