fix extra in dataclasses with bases

pydantic/dataclasses.py

@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any, Callable, Dict, Optional, Type, TypeVar, Union, overload
+from typing import TYPE_CHECKING, Any, Callable, Dict, Optional, Type, TypeVar, Union, get_type_hints, overload
 
 from .class_validators import gather_all_validators
 from .error_wrappers import ValidationError
@@ -163,7 +163,9 @@ def _pydantic_post_init(self: 'Dataclass', *initvars: Any) -> None:
 
     if getattr(config, 'extra', Extra.forbid) is not Extra.forbid:
         def allow_extra_init(self, *args, **kwargs):
-            self.__original_init__(*args, **{k: v for k, v in kwargs.items() if k in self.__annotations__})
+            self.__original_init__(*args, **{
+                k: v for k, v in kwargs.items() if k in get_type_hints(type(self))
+            })
 
         cls.__original_init__ = cls.__init__
         cls.__init__ = allow_extra_init

tests/test_dataclasses.py

@@ -845,3 +845,18 @@ class Foo:
         b: str
 
     Foo(**{"a": "bar", "b": "foo", "c": 1})
+
+
+def test_allow_extra_subclass():
+    class C:
+        extra = Extra.ignore
+
+    @pydantic.dataclasses.dataclass(config=C)
+    class Foo:
+        a: str
+
+    @pydantic.dataclasses.dataclass(config=C)
+    class Bar(Foo):
+        b: str
+
+    Bar(**{"a": "bar", "b": "foo", "c": 1})