core::assert!

macro_rules! assert {
    ($cond:expr) => { ... };
    ($cond:expr, $($arg:tt)+) => { ... };
}

Ensure that a boolean expression is true at runtime.

This will invoke the panic! macro if the provided expression cannot be evaluated to true at runtime.

This macro has a second version, where a custom panic message can be provided.

Examples

fn main() { // the panic message for these assertions is the stringified value of the // expression given. assert!(true); fn some_computation() -> bool { true } // a very simple function assert!(some_computation()); // assert with a custom message let x = true; assert!(x, "x wasn't true!"); let a = 3; let b = 27; assert!(a + b == 30, "a = {}, b = {}", a, b); }

// the panic message for these assertions is the stringified value of the
// expression given.
assert!(true);

fn some_computation() -> bool { true } // a very simple function

assert!(some_computation());

// assert with a custom message
let x = true;
assert!(x, "x wasn't true!");

let a = 3; let b = 27;
assert!(a + b == 30, "a = {}, b = {}", a, b);