From 20f0ef48188dc787e8207f12d2406b1043a9eca2 Mon Sep 17 00:00:00 2001
From: Yurii Karabas <1998uriyyo@gmail.com>
Date: Mon, 2 Aug 2021 16:22:49 +0300
Subject: [PATCH] bpo-44799: Fix InitVar resolving using get_type_hints

---
 Lib/dataclasses.py                                 |  3 +++
 Lib/test/test_dataclasses.py                       | 14 ++++++++++++++
 .../2021-08-02-16-21-59.bpo-44799.hXfxPO.rst       |  2 ++
 3 files changed, 19 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2021-08-02-16-21-59.bpo-44799.hXfxPO.rst

diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 95ff39287bed61..5247d229acc240 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -228,6 +228,9 @@ class InitVar:
     def __init__(self, type):
         self.type = type
 
+    def __call__(self, *args, **kwargs):  # required by typing.get_type_hints, see bpo-44799
+        raise TypeError("InitVar object is not callable")
+
     def __repr__(self):
         if isinstance(self.type, type):
             type_name = self.type.__name__
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 8e645aeb4a7503..68caacada1ebd8 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -3831,5 +3831,19 @@ class A:
                 c: int = 1
                 d: int
 
+    def test_lazy_init_var_get_type_hints(self):
+        @dataclass
+        class Foo:
+            a: "InitVar[int]"
+
+        hints = get_type_hints(Foo)
+
+        self.assertIsInstance(hints.get("a"), InitVar)
+        self.assertEqual(hints.get("a").type, int)
+
+    def test_init_var_is_not_callable(self):
+        with self.assertRaisesRegex(TypeError, r"InitVar object is not callable"):
+            InitVar[int]()
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2021-08-02-16-21-59.bpo-44799.hXfxPO.rst b/Misc/NEWS.d/next/Library/2021-08-02-16-21-59.bpo-44799.hXfxPO.rst
new file mode 100644
index 00000000000000..67971226acedef
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-08-02-16-21-59.bpo-44799.hXfxPO.rst
@@ -0,0 +1,2 @@
+Fix issue when ``dataclass.InitVar`` can not be evaluated using
+``typing.get_type_hints``. Patch provided by Yurii Karabas.