Each instance of ListStore and ListModel works on a concrete and fixed item type. Currently this is handled by checking and passing around a glib Type value. In Rust this can be expressed more elegantly by a type parameter. The big advantage is that there is no more fallible casting when using the different methods on these instances and Rust’s type system can be leveraged for e.g. type inference.

Before

struct ListStore;

fn new(item_type: glib::types::Type) -> Self;
fn append<P: IsA<glib::Object>>(&self, item: &P);
…

After

struct ListStore<T: IsA<Object>>;

fn new() -> Self;
fn append<P: IsA<T>>(&self, item: &P);
…