class tree walk can be idiomized with find_map and transpose

src/runner/instance.rs

@@ -256,15 +256,9 @@ impl mlua::UserData for Instance{
 						database:db,
 						descriptor:Some(class),
 					};
-					Ok(loop{
-						match iter.next(){
-							Some(class)=>match cf.get_or_create_class_function(lua,&class.name,index_str)?{
-								Some(function)=>break Some(function),
-								None=>(),
-							},
-							None=>break None,
-						}
-					})
+					iter.find_map(|class|
+						cf.get_or_create_class_function(lua,&class.name,index_str).transpose()
+					).transpose()
 				})?{
 					return function.into_lua(lua);
 				}