俱舍論疏 11.88

11.88

論「世施設中至見不圓滿」，准此似月下日高，此發影覆其自面故。

The treatise says: "In the Lokaprajñapti [...] seen as not complete." According to this, it seems that the moon is below and the sun is above, so that it casts a shadow that covers its own face.