Macro debug_expr

macro_rules! debug_expr {
    () => { ... };
    ($val:expr $(,)?) => { ... };
    ($($val:expr),+ $(,)?) => { ... };
}

Prints out the expression and its location, then returns it.

let foo: u8 = debug_expr!(0xff);
// Prints [main.rs:2] 0xff = 255

Taken straight from Rust std::dbg.