# Freezing

When data is immutably borrowed, it also freezes. Frozen data can't be modified via the original object until all references to it go out of scope:

    fn main() {
        let mut _mutable_integer = 7i32;

        {
            // Borrow `_mutable_integer`
            let _large_integer = &_mutable_integer;

            // Error! `_mutable_integer` is frozen in this scope
            _mutable_integer = 50;
            // FIXME ^ Comment out this line

            // `_large_integer` goes out of scope
        }

        // Ok! `_mutable_integer` is not frozen in this scope
        _mutable_integer = 3;
    }