Merchants of super-expensive products sell an implicitpromise of "the keys to the kingdom."
生意人卖的产品超级贵,似乎暗示是“通向王国的钥匙”。
2
But if ln were aliased with li, then it would break the type-safety promiseimplicit in the definition of li — that it is a list of integers, which is why generic types cannot be covariant.