Function field_set_window 

pub fn field_set_window(
    h: u64,
    slot: FieldSlot,
    win: Window,
    val: &[u64],
) -> bool

Writes the leaf win of property slot of the live object h as the known value val, leaving the rest of the property alone; like field_set it is a no-op returning false for a dead handle or bad slot, and it wakes waiters when the property changed.