A hack-ish way to fix dataclasses & get_type_hints()

fix_dataclass_introspection.diff

diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 28e9f75127..ad3dc46b67 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -868,7 +868,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
         # Include InitVars and regular fields (so, not ClassVars).
         flds = [f for f in fields.values()
                 if f._field_type in (_FIELD, _FIELD_INITVAR)]
-        _set_new_attribute(cls, '__init__',
+        had_own_init = _set_new_attribute(cls, '__init__',
                            _init_fn(flds,
                                     frozen,
                                     has_post_init,
@@ -878,6 +878,9 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
                                     '__dataclass_self__' if 'self' in fields
                                             else 'self',
                           ))
+        if not had_own_init:
+            cls.__init__.__module__ = cls.__module__
+            cls.__init__.__generated__ = True

     # Get the fields as a list, and include only real fields.  This is
     # used in all of the following methods.
diff --git a/Lib/typing.py b/Lib/typing.py
index 445a42492b..3f6a916b6c 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -978,7 +978,10 @@ def get_type_hints(obj, globalns=None, localns=None):
         if isinstance(obj, types.ModuleType):
             globalns = obj.__dict__
         else:
-            globalns = getattr(obj, '__globals__', {})
+            if hasattr(obj, '__generated__'):
+                globalns = sys.modules[obj.__module__].__dict__
+            else:
+                globalns = getattr(obj, '__globals__', {})
         if localns is None:
             localns = globalns
     elif localns is None:

Another way to fix this:

• Fix exec() to accept arbitrary Mappings for globals;
• Fix dataclasses to set __globals__ attribute on functions it generates to a ModuleProxy mapping like the following:

class ModuleProxy(collections.abc.Mapping):

    def __init__(self, modname):
        self.__modname = modname

    @property
    def _mod(self):
        return sys.modules[self.__modname].__dict__

    def __getitem__(self, key):
        return self._mod[key]

    def __len__(self):
        return len(self._mod)

    def __contains__(self, x):
        return x in self._mod

    def __iter__(self):
        return iter(self._mod)