Macro ensure 

macro_rules! ensure {
    ( $condition:expr ) => { ... };
    ( $condition:expr , $( $args:tt )* ) => { ... };
}

Ensure that a condition holds true, or else early exit from the current function with an error.

ensure!(condition, ...) is equivalent to the following:

if !condition {
    return Err(format_err!(...));
}

Like anyhow::ensure! but for wasmtime::Error.

Example

use wasmtime::{ensure, Result};

fn checked_div(a: u32, b: u32) -> Result<u32> {
    ensure!(b != 0, "cannot divide by zero: {a} / {b}");
    Ok(a / b)
}

let x = checked_div(6, 2).unwrap();
assert_eq!(x, 3);

let error = checked_div(9, 0).unwrap_err();
assert_eq!(
    error.to_string(),
    "cannot divide by zero: 9 / 0",
);