From 834e125895c5ca297d7a62d11b34e7566d96762e Mon Sep 17 00:00:00 2001
From: Shen Yi Hong <shen_yi_hong@outlook.com>
Date: Sat, 29 Mar 2025 18:08:22 +0800
Subject: [PATCH 1/3] feat: check if `@property` overrides parent class
 variable

---
 mypy/checker.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mypy/checker.py b/mypy/checker.py
index 12afa4d3edf5..67af0f816fb6 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -2280,6 +2280,17 @@ def check_method_override_for_base_with_name(
             if inner is not None:
                 typ = inner
                 typ = get_property_type(typ)
+
+                if (
+                    isinstance(original_node, Var)
+                    and original_node.is_classvar
+                    and defn.name == original_node.name
+                    and isinstance(defn, Decorator)
+                ):
+                    self.fail(
+                        message_registry.CANNOT_OVERRIDE_CLASS_VAR.format(base.name), defn.func
+                    )
+
                 if (
                     isinstance(original_node, Var)
                     and not original_node.is_final

From 00603342581dfac42762f8767d427a7a94a5803e Mon Sep 17 00:00:00 2001
From: Shen Yi Hong <shen_yi_hong@outlook.com>
Date: Sat, 29 Mar 2025 18:09:27 +0800
Subject: [PATCH 2/3] test: add `testOverrideWithPropertyDecorator` unit test

---
 test-data/unit/check-classvar.test | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/test-data/unit/check-classvar.test b/test-data/unit/check-classvar.test
index 918926627bfd..276e4aada47d 100644
--- a/test-data/unit/check-classvar.test
+++ b/test-data/unit/check-classvar.test
@@ -269,6 +269,19 @@ class A(metaclass=ABCMeta):
 class B(A):
     x = 0  # type: ClassVar[int]
 
+[case testOverrideWithPropertyDecorator]
+from typing import ClassVar
+
+class A:
+    x: ClassVar[int]
+class B(A):
+    @property
+    def x(self) -> int: ...
+[builtins fixtures/property.pyi]
+[out]
+main:7: error: Cannot override class variable (previously declared on base class "A") with instance variable
+main:7: error: Cannot override writeable attribute with read-only property
+
 [case testAcrossModules]
 import m
 reveal_type(m.A().x)

From f2f8a98e10e5b6d794d338aaf8edce01e3206a4f Mon Sep 17 00:00:00 2001
From: Shen Yi Hong <shen_yi_hong@outlook.com>
Date: Sun, 30 Mar 2025 00:43:52 +0800
Subject: [PATCH 3/3] fix: prevent override when there exists a `setter`

---
 mypy/checker.py                    | 16 ++++++++++++----
 test-data/unit/check-classvar.test |  4 +++-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index 67af0f816fb6..0183a78ed05d 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -2285,11 +2285,19 @@ def check_method_override_for_base_with_name(
                     isinstance(original_node, Var)
                     and original_node.is_classvar
                     and defn.name == original_node.name
-                    and isinstance(defn, Decorator)
+                    and (isinstance(defn, (Decorator, OverloadedFuncDef)))
                 ):
-                    self.fail(
-                        message_registry.CANNOT_OVERRIDE_CLASS_VAR.format(base.name), defn.func
-                    )
+                    decorator_func = None
+                    if isinstance(defn, Decorator):
+                        decorator_func = defn.func
+                    elif isinstance(defn.items[0], Decorator):
+                        decorator_func = defn.items[0].func
+
+                    if decorator_func:
+                        self.fail(
+                            message_registry.CANNOT_OVERRIDE_CLASS_VAR.format(base.name),
+                            decorator_func,
+                        )
 
                 if (
                     isinstance(original_node, Var)
diff --git a/test-data/unit/check-classvar.test b/test-data/unit/check-classvar.test
index 276e4aada47d..1b7998786baf 100644
--- a/test-data/unit/check-classvar.test
+++ b/test-data/unit/check-classvar.test
@@ -277,10 +277,12 @@ class A:
 class B(A):
     @property
     def x(self) -> int: ...
+
+    @x.setter
+    def x(self, value: int) -> None: ...
 [builtins fixtures/property.pyi]
 [out]
 main:7: error: Cannot override class variable (previously declared on base class "A") with instance variable
-main:7: error: Cannot override writeable attribute with read-only property
 
 [case testAcrossModules]
 import m