python 3.7 RecursionError when using recursive typing definition and get_type_hints

[reinhrst]

The following code gives a RecursionError in python 3.7.0 (runs fine in 3.6.4, giving the answer {'return': typing.Sequence[typing.Union[str, typing.Sequence[typing.Union[str, _ForwardRef('Foo')]]]]})

import typing

Foo = typing.Sequence[typing.Union[str, "Foo"]]

def a() -> Foo:
   ...

typing.get_type_hints(a)

[ilevkivskyi]

Thanks for reporting! I think this may be related to recent fixes to interaction between get_type_hints and from __future__ import annotations. The fix for this regression may be non-trivial, so I would prefer to wait for @ambv opinion here.

[srittau]

As the typing module is not part of Python, please file a bug report at bugs.python.org if this is still an issue.