RustConf 2016 - RFC: In Order to Form a More Perfect `union` by Josh Triplet Users of Rust for systems programming rely heavily on its exceptional support for FFI. Many systems APIs involve unions, and macros and transmute produced unmaintainable solutions. 16 months, 3 RFCs, and a half-dozen possible syntaxes later, RFC1444 added union to the Rust language, ready for implementation. This talk will present unions as a case study of the Rust RFC process, show the kinds of iterative refinements that take place, review corner cases and interactions that arise when attempting to extend Rust, and discuss the next steps forward for union implementation.