A pair of Rust macros to assert if a value matches a simple enum (no ADT support).

assert_is_enum.rs

// I was really annoyed that I couldn't easily assert that a
// straightforward enum was being matched.  I'm sure there's a better
// way to do this but, hey, this is my first Rust macro.

macro_rules! assert_is_enum {
    ($left:expr, $right:path) => ({
        match &$left {
            left_val =>
                if let $right = *left_val { }
            else {
                panic!(r#"assertion failed: `(left == right)`
  left: `{:?}`,
 right: `{:?}`"#, $left, $right)
            }
        }
    });
    ($left:expr, $right:path, $($arg:tt)+) => ({
        match &$left {
            left_val =>
                if let $right = *left_val { }
            else {
                panic!(r#"assertion failed: `(left == right)`
  left: `{:?}`,
 right: `{:?}`: {}"#, $left, $right,
                       format_args!($($arg)+))
            }
        }
    });
}


macro_rules! assert_is_not_enum {
    ($left:expr, $right:path) => ({
        match &$left {
            left_val =>
                if let $right = *left_val {
                    panic!(r#"assertion failed: `(left == right)`
  left: `{:?}`,
 right: `{:?}`"#, $left, $right)
                }
            else { }
        }
    });
    ($left:expr, $right:path, $($arg:tt)+) => ({
        match &$left {
            left_val =>
                if let $right = *left_val {
                    panic!(r#"assertion failed: `(left == right)`
  left: `{:?}`,
 right: `{:?}`: {}"#, $left, $right,
                           format_args!($($arg)+))
                }
            else { }
        }
    });
}

#[cfg(test)]
mod tests {

    #[derive(Debug)]
    pub enum Demo {
        This,
        Test
    }

    use self::Demo::*;

    #[test]
    pub fn test() {
        let x: Demo = This;
        assert_is_enum!(x, This);
        assert_is_not_enum!(x, Test);
    }
}