1# `unboxed_closures`23The tracking issue for this feature is [#29625]45See Also: [`fn_traits`](../library-features/fn-traits.md)67[#29625]: https://github.com/rust-lang/rust/issues/2962589----1011The `unboxed_closures` feature allows you to write functions using the `"rust-call"` ABI,12required for implementing the [`Fn*`] family of traits. `"rust-call"` functions must have13exactly one (non self) argument, a tuple representing the argument list.1415[`Fn*`]: ../../std/ops/trait.Fn.html1617```rust18#![feature(unboxed_closures)]1920extern "rust-call" fn add_args(args: (u32, u32)) -> u32 {21    args.0 + args.122}2324fn main() {}25```