[fix]: Removed unnecessary indiretion to strings for proc-macro.

macros/src/lib.rs

@@ -156,12 +156,12 @@ pub fn validity_predicate(
 // TODO: use this crate for errors: https://crates.io/crates/proc-macro-error
 pub fn derive_storage_keys(item: TokenStream) -> TokenStream {
     let struct_def = parse_macro_input!(item as ItemStruct);
-    create_storage_keys(struct_def).parse().unwrap()
+    create_storage_keys(struct_def).into()
 }
 
 #[inline]
 // TODO: emit allow_deadcode in ALL and VALUES
-fn create_storage_keys(struct_def: ItemStruct) -> String {
+fn create_storage_keys(struct_def: ItemStruct) -> TokenStream2 {
     // type check the struct - all fields must be of type `&'static str`
     let fields = match &struct_def.fields {
         syn::Fields::Named(fields) => &fields.named,
@@ -225,7 +225,6 @@ fn create_storage_keys(struct_def: ItemStruct) -> String {
             };
         }
     }
-    .to_string()
 }
 
 #[inline]
@@ -277,7 +276,7 @@ mod test_proc_macros {
         "#;
         let struct_def = syn::parse_str(TEST).unwrap();
         let result = create_storage_keys(struct_def);
-        let result: ItemImpl = syn::parse_str(&result).unwrap();
+        let result: ItemImpl = syn::parse2(result).unwrap();
         let expected = syn::parse_str(EXPECT).unwrap();
         assert_eq!(result, expected);
     }