You could consider actually implementing From when you define a from method:

impl From<(i32, u32)> for Fixed {
    fn from((integer, decimal): (i32, u32)) -> Fixed {
        Fixed {
            integer,
            decimal,
        }
    }
}

I think it's more clear (otherwise use 'new'), but what is more, you can have "overloading", e.g.

impl From<f64> for A {
    fn from(val: f64) -> A {
        Fixed {
            integer: val.round() as i32,
            decimal: (val * (std::u32::MAX as f64)).round() as u32,
        }
    }
}

fn main() {
    let a1 = Fixed::from((1, 0));
    let a2 = Fixed::from(1.0);
}