[bazoom42]

> superset of objects can only have the same or fewer properties

This is potentially misleading. A superset will include more objects and therefore may include more individual properties. But type checking is about what can be safely assumed about all members of a set, so more different objects in the set will constrain the type more.

Object is a superset of Date because the set of objects includes alle Dates but also things which are not dates and have different properties. But in the context of type checking, object is more constrained because there are fewer properties which all members of the set are guaranteed to have.

Typescript is a superset of Javascript because all Javascript programs are also Typescript programs. There is no contradiction.

[hbrn]

> object is more constrained because there are fewer properties which all members of the set are guaranteed to have.

In my mind it's the opposite: object is less constrained, because there are fewer requirements you need to fulfill to be considered an object. Object type is very permissive.

The more constrained type is, the fewer objects it's set will contain. The more constrained the type is, the more rules it enforces. Seems intuitive, isn't it?