Macro error 

macro_rules! error {
    ($value: expr) => { ... };
    ($kind: ident, $value: expr) => { ... };
    ($value: literal, $($arg:tt)+) => { ... };
    ($kind: ident, $value: literal, $($arg:tt)+) => { ... };
    (as $kind: ident) => { ... };
    () => { ... };
}

! A Utility crate for creating std::io::Error structs. create a std::io::Error

Syntax

error!("some value");

error!(Other, "some value");

error!(as Other);

error!();