Abstract Rust is a non-Garbage Collected (GCed) language, but the lack of GC makes expressing data-structures that require shared ownership awkward, inefficient, or both. In this paper we explore a new design for, and implementation of, GC in Rust, called Alloy. Unlike previous approaches to GC in Rust, Alloy allows existing Rust destructors to be automatically used as GC finalizers: this makes Alloy integrate better with existing Rust code than previous solutions but introduces surprising sound...