[Python-Dev] Postponed annotations break inspection of dataclasses

[Yury Selivanov]

On Sat, Sep 22, 2018 at 3:11 PM Guido van Rossum <guido at python.org> wrote:
[..]
> Still, I wonder if there's a tweak possible of the globals and locals used when exec()'ing the function definitions in dataclasses.py, so that get_type_hints() gets the right globals for this use case.
>
> It's really tough to be at the intersection of three PEPs...

If it's possible to fix exec() to accept any Mapping (not just dicts),
then we can create a proxy mapping for "Dataclass.__init__.__module__"
module and everything would work as expected.

Here's a very hack-ish fix we can use in meanwhile (even in 3.7.1?):
https://gist.github.com/1st1/37fdd3cc84cd65b9af3471b935b722df

Yury