literally
macro_rules! hmap { (@single $($x:tt)*) => { ... }; (@count $($rest:expr),*) => { ... }; ($($key:expr => $value:expr),* $(,)?) => { ... }; }
Literally just a HashMap literal with keys and values into'd.
let m: HashMap<String, String> = hmap!{ "key" => "value" }; assert_eq!(m.get("key"), Some(&"value".to_string()))