Function overflows 

pub fn overflows<'a, R>(
    columns: &[Column<'a>],
    rows: &[R],
    sizing: &Sizing<'_>,
    style: &TableStyle,
    width: u16,
) -> bool
where
    R: AsRef<[Cell<'a>]>,

Whether a table drawn at width would leave anything overflowing.

True only when the essential columns alone do not fit, since that is the one case narrowing cannot answer. A caller that would rather show fewer rows than truncate a cell can ask this and draw something else.