Function take_function_args 

pub fn take_function_args<const N: usize, T>(
    function_name: &str,
    args: impl IntoIterator<Item = T>,
) -> Result<[T; N]>

Converts a collection of function arguments into a fixed-size array of length N producing a reasonable error message in case of unexpected number of arguments.

Example

fn my_function(args: &[ScalarValue]) -> Result<()> {
    // function expects 2 args, so create a 2-element array
    let [arg1, arg2] = take_function_args("my_function", args)?;
    // ... do stuff..
    Ok(())
}

// Calling the function with 1 argument produces an error:
let args = vec![ScalarValue::Int32(Some(10))];
let err = my_function(&args).unwrap_err();
assert_eq!(
    err.to_string(),
    "Execution error: my_function function requires 2 arguments, got 1"
);
// Calling the function with 2 arguments works great
let args = vec![ScalarValue::Int32(Some(10)), ScalarValue::Int32(Some(20))];
my_function(&args).unwrap();