auto_enums

auto_enums solves a common Rust pain point: when different branches of a function return different concrete types implementing the same trait. Annotate with #[auto_enum(Iterator)] and it generates a hidden enum that delegates the trait, avoiding Box<dyn Iterator>.

Companion crates iter-enum and io-enum extend this to specific trait families. For full enum-based trait dispatch, see enum-dispatch and ambassador. See rust-enum-crates for the full landscape.