bluss_smart_assert.rs

// Crazy macro by bluss

// Split a stream of tt's into before and after `==`
macro_rules! split_eq {
    ($sep: tt ($m: ident $($args:tt)*) [$($stack:tt)*] $x: tt) => {
        $m ! ($($args)* $($stack)* $x $sep)
    };
    ($sep: tt ($m: ident $($args:tt)*) [$($stack:tt)*] $x: tt == $($rest: tt)*) => {
        $m ! ($($args)* $($stack)* $x $sep $($rest)*)
    };
    ($sep: tt ($m:ident $($args:tt)*) [$($stack:tt)*] $x: tt $($rest: tt)*) => {
        split_eq!($sep ($m $($args)*) [$($stack)* $x] $($rest)*);
    };
}

macro_rules! assert_impl {
    ($one:expr =>) => ( assert!($one) );
    ($a:expr => $b:expr) => (
    {
        let _a = &$a;
        let _b = &$b;
        assert!(_a == _b,
                "Failed assertion {:?} == {:?} (`{}`):\n    expected:\n        {:?} (`{}`)\n    but found:\n        {:?} (`{}`)",
                _a,
                _b,
                stringify!($a == $b),
                _a,
                stringify!($a),
                _b,
                stringify!($b),
        );
        assert!(_b == _a, "Failed assertion {:?} == {:?} (`{}`)", _b, _a, stringify!($b == $a));
    }
    );
}

macro_rules! cleverassert {
    ($($t:tt)+) => (
        split_eq!(=> (assert_impl) [] $($t)+)
    );
}


fn main() {
    cleverassert!(true);
    cleverassert!(2 == 2);
    cleverassert!("hi" == "he".to_string());
}