In Rust 1.22.1, this code compiles:

use std::ascii::AsciiExt; fn main() { "a".eq_ignore_ascii_case("a"); }

In Rust 1.23.0.beta.1, it issues a warning:

warning: unused import: `std::ascii::AsciiExt` --> src/main.rs:1:5 | 1 | use std::ascii::AsciiExt; | ^^^^^^^^^^^^^^^^^^^^ | = note: #[warn(unused_imports)] on by default 

My tidiness kicks in and I remove the trait — no one wants warnings, right?

However, if I remove this trait, my crates will no longer compile on older versions of Rust. I've actually been bitten by this twice now, and one of those times has been released to crates.io. 😞