mypy.types.TypeType

For types like Type[User]. This annotates variables that are class objects, constrained by the type argument. See PEP 484 for more details. We may encounter expressions whose values are specific classes; those are represented as callables (possibly overloaded) corresponding to the class's constructor's signature and returning an instance of that class. The difference with Type[C] is that those callables always represent the exact class given as the return type; Type[C] represents any class that's a subclass of C, and C may also be a type variable or a union (or Any). Many questions around subtype relationships between Type[C1] and def(...) -> C2 are answered by looking at the subtype relationships between C1 and C2, since Type[] is considered covariant. There's an unsolved problem with constructor signatures (also unsolved in PEP 484): calling a variable whose type is Type[C] assumes the constructor signature for C, even though a subclass of C might completely change the constructor signature. For now we just assume that users of Type[C] are careful not to do that (in the future we might detect when they are violating that assumption).