Deprecate `mypy_extensions.TypedDict`? about mypy_extensions

[JelleZijlstra]

Agree, there's no need for mypy_extensions.TypedDict any more. As an implementation strategy, we can:

• Raise a runtime DeprecationWarning when a new mypy_extensions.TypedDict class is created
• Have mypy show a warning whenever mypy_extensions.TypedDict is used

[AlexWaygood]

I'm taking a look at the runtime side of things. One issue: it seems we'd really need stacklevel=3 if you're constructing a TypedDict class like this:

Foo = TypedDict('Foo', {'x': int})

...But you'd need stacklevel=2 if you're constructing a TypedDict like this:

class Bar(TypedDict):
    x: int

I'm not sure if there's a way to distinguish between the two, if we emit the DeprecationWarning in _TypedDictMeta.__new__

[AlexWaygood]

I'm not sure if there's a way to distinguish between the two, if we emit the DeprecationWarning in _TypedDictMeta.__new__

Hmm, I think I have a solution