Macro ensure

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

Util macro for generating error when condition check failed.

Case 1: Expression only.

ensure!(a < 0);

This will generate following error:

anyhow!("a < 0").into()

Case 2: Error message only.

ensure!(a < 0, "a should not be negative!");

This will generate following error:

anyhow!("a should not be negative!").into();

Case 3: Error message with argument.

ensure!(a < 0, "a should not be negative, value: {}", 1);

This will generate following error:

anyhow!("a should not be negative, value: 1").into();

Case 4: Error code.

ensure!(a < 0, ErrorCode::MemoryError { layout });

This will generate following error:

ErrorCode::MemoryError { layout }.into();