From 3059fcd06773a687656587bb94d1aaa985434ac5 Mon Sep 17 00:00:00 2001
From: daleselaji-dev <265319989+daleselaji-dev@users.noreply.github.com>
Date: Tue, 1 Sep 2026 10:50:09 +0800
Subject: [PATCH] fix(dataclasses): skip non-Var ClassVars

---
 mypy/plugins/dataclasses.py           |  6 +++++-
 test-data/unit/check-dataclasses.test | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
index a511e714ac6b4..37a2f5d8f7d62 100644
--- a/mypy/plugins/dataclasses.py
+++ b/mypy/plugins/dataclasses.py
@@ -600,7 +600,11 @@ def collect_attributes(self) -> list[DataclassAttribute] | None:
                 # We will issue an error later.
                 continue
 
-            assert isinstance(node, Var), node
+            # A ClassVar assigned a class definition, such as a TypedDict,
+            # can be represented by a TypeInfo rather than a Var. Dataclasses
+            # ignore ClassVars, so there is no attribute to collect here.
+            if not isinstance(node, Var):
+                continue
 
             # x: ClassVar[int] is ignored by dataclasses.
             if node.is_classvar:
diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
index f43ac255373e6..0c6e8f9d36e29 100644
--- a/test-data/unit/check-dataclasses.test
+++ b/test-data/unit/check-dataclasses.test
@@ -1,3 +1,17 @@
+[case testClassVarTypedDict]
+import dataclasses
+from typing import ClassVar, TypedDict
+
+@dataclasses.dataclass
+class X:
+    value: int
+    TD: ClassVar = TypedDict("TD", {"value": int})
+
+X.TD
+
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-medium.pyi]
+
 [case testDataclassesBasic]
 from dataclasses import dataclass