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use std::convert::From;

#[derive(Debug)]
pub struct MyError {
    pub file: &'static str,
    pub line: u32,
    pub statement: String,
    pub description: String,
    pub cause: Option<Box<std::error::Error>>,
}

#[allow(unused_must_use)]
impl std::fmt::Display for MyError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        if let Some(ref x ) = self.cause {
            write!(f, "{}\n", &**x);
        }
        write!(f, "{}:{} `{}`", self.file, self.line, self.statement)
    }
}

impl std::error::Error for MyError {
    fn description(&self) -> &str {
        return &*self.description;
    }
    fn cause(&self) -> Option<&std::error::Error> {
        if let Some(ref x) = self.cause {
            Some(&**x)
        } else {
            None
        }
    }
}

impl <'a>From<&'a str> for MyError {
    fn from(x: &str) -> MyError {
        MyError {
            file: "", line: 0,
            statement: x.to_string(),
            description: x.to_string(),
            cause: None,
        }
    }
}

#[macro_export]
macro_rules! tryx {
    ($e:expr) =>
        (match $e {
            Ok(x) => x ,
            Err(err) => {
                let l = line!();
                let f = file!();
                return Err(MyError {
                    file: f, line: l,
                    statement: stringify!($e).to_string(),
                    description: format!("{}:{} `{}` {}", f, l, stringify!($e), err.description()),
                    cause: Some(Box::new(err)),
                })
            }
        })
}

#[macro_export]
macro_rules! myerr {
    ($caption:expr) => (
        {
                let l = line!();
                let f = file!();
                MyError {
                    file: f, line: l,
                    statement: $caption,
                    description: format!("{}:{} {}", f, l, $caption),
                    cause: None,
                }
        })
}