GAT is a language feature known in Rust, allowing associated types to have generic parameters.
See (Huey 2022, 2021; Huey and Matsakis 2022; Withoutboats 2016).
Reference
Huey, Jack. 2021. “The Push for Gats Stabilization.” August 3, 2021. https://blog.rust-lang.org/2021/08/03/GATs-stabilization-push/.
———. 2022. “Generic Associated Types to Be Stable in Rust 1.65.” October 28, 2022. https://blog.rust-lang.org/2022/10/28/gats-stabilization/.
Huey, Jack, and Niko Matsakis. 2022. “Generic Associated Types Initiative.” 2022. https://rust-lang.github.io/generic-associated-types-initiative/index.html.
Withoutboats. 2016. “Rfc1598: Generic Associated Types.” April 29, 2016. https://rust-lang.github.io/rfcs/1598-generic_associated_types.html.