Why should type annotation be enforced at run time? In statically typed languages there is no type checking at run time, your type system already proved the type of variable.
They can (as in - there's API for that, the rest is up to a community effort) improve performance of a final program, if type-annotated code is passed through Cython with ``annotation_typing=True`` flag:
http://docs.cython.org/en/latest/src/tutorial/pure.html#stat...
https://github.com/cython/cython/issues/1672#issuecomment-29...