For example, `Object.assign` overrides all property with same name. Sometimes you use it to construct a new object, so it is a safe usage. But what about using it to override the buildin object's property? It is definitely going to explode the whole program. However there isn't really a mechanism for typescript to differ the usage is safe or not. So in order to maintain compatibility, typescript just allow both of them.

And typescript in my opinion don't really isolate very much complexity. But it does document what the 'complexity' is. So you can offload your memory tax to it. Put it away, do something else, and resume later by looking at what definition you write before. In this way. It can make managing a big project much easier if you make proper use of it.