Macro bug_on 

macro_rules! bug_on {
    ($cond:expr) => { ... };
    ($cond:expr, $fmt:literal $(, $arg:expr)* $(,)?) => { ... };
}

This is a macro that is used to panic when a condition is true. It is similar to the BUG_ON() macro in the Linux kernel. Link: https://www.kernel.org/