"About a year ago, in Rust 1.13, we introduced the ? operator" And that includes a link to the 1.13 announcement with a detailed explanation. https://blog.rust

"About a year ago, in Rust 1.13, we introduced the ? operator" And that includes a link to the 1.13 announcement with a detailed explanation. https://blog.rust-lang.org/2016/11/10/Rust-1.13.html https://blog.rust-lang.org/2016/11/10/Rust-1.13.html