Macro amethyst_nphysics::fail_cond

macro_rules! fail_cond {
    ($x:expr) => { ... };
    ($x:expr, $y:expr) => { ... };
}

These macros are used to assert the validity of some data, but instead to panics they stop the functions processing print a message on the console.

You can use the macro fail_cond(expression, return) if you need to return a value in case of fail.