So I have another idea. Not sure if this should hold up PEP 613 or be a separate one or if it's just silly. In mypy (not sure about pyre), if you write T = TypeVar('T') A = List[T] then A becomes a *parametrized* type and must itself be instantiated as A[some_type], e.g. A[int] will mean List[T]. (Plain A means List[Any], unfortunately, for historic reasons.) It's easy to forget this behavior and accidentally end up with an unintentional List[All]. Perhaps we could reinforce it by requiring A: TypeAlias[T] = List[T] and otherwise reject type vars in the RHS? -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>