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use std::fmt::{self, Display}; use std::borrow::Cow; use Fail; pub fn error_msg<S: Into<Cow<'static, str>>>(msg: S) -> ErrorMessage { ErrorMessage { msg: msg.into() } } #[derive(Debug)] pub struct ErrorMessage { msg: Cow<'static, str>, } impl Fail for ErrorMessage { fn fail(&self, f: &mut fmt::Formatter) -> fmt::Result { Display::fmt(&self.msg, f) } } #[macro_export] macro_rules! format_err { ($($arg:tt)*) => { $crate::error_msg(format!($($arg)*)) } }