From 8cee6dc457ea567923a752efe8c4e9a4b97c812b Mon Sep 17 00:00:00 2001
From: Nikita Sobolev <mail@sobolevn.me>
Date: Thu, 18 Nov 2021 06:18:12 +0300
Subject: [PATCH] Now we can override attributes with methods, refs #10134
 (#11561)

Now we can override attributes with methods.

Closes #10134
Closes #11556

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
---
 mypy/checker.py                   | 10 +++++++++
 test-data/unit/check-classes.test | 37 +++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/mypy/checker.py b/mypy/checker.py
index 36751bbc9b15..7189b3d96faf 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1536,6 +1536,16 @@ def check_method_override_for_base_with_name(
                     original_type = self.function_type(original_node)
                 elif isinstance(original_node, Decorator):
                     original_type = self.function_type(original_node.func)
+                elif isinstance(original_node, Var):
+                    # Super type can define method as an attribute.
+                    # See https://github.com/python/mypy/issues/10134
+
+                    # We also check that sometimes `original_node.type` is None.
+                    # This is the case when we use something like `__hash__ = None`.
+                    if original_node.type is not None:
+                        original_type = get_proper_type(original_node.type)
+                    else:
+                        original_type = NoneType()
                 else:
                     assert False, str(base_attr.node)
             if isinstance(original_node, (FuncDef, OverloadedFuncDef)):
diff --git a/test-data/unit/check-classes.test b/test-data/unit/check-classes.test
index 21dae9201c01..b15f9f77f3c7 100644
--- a/test-data/unit/check-classes.test
+++ b/test-data/unit/check-classes.test
@@ -114,6 +114,43 @@ class A:
 A().f = None # E: Cannot assign to a method
 
 
+[case testOverrideAttributeWithMethod]
+# This was crashing:
+# https://github.com/python/mypy/issues/10134
+from typing import Protocol
+
+class Base:
+    __hash__ = None
+
+class Derived(Base):
+    def __hash__(self) -> int:  # E: Signature of "__hash__" incompatible with supertype "Base"
+        pass
+
+# Correct:
+
+class CallableProtocol(Protocol):
+    def __call__(self, arg: int) -> int:
+        pass
+
+class CorrectBase:
+    attr: CallableProtocol
+
+class CorrectDerived(CorrectBase):
+    def attr(self, arg: int) -> int:
+        pass
+
+[case testOverrideMethodWithAttribute]
+# The reverse should not crash as well:
+from typing import Callable
+
+class Base:
+    def __hash__(self) -> int:
+        pass
+
+class Derived(Base):
+    __hash__ = 1  # E: Incompatible types in assignment (expression has type "int", base class "Base" defined the type as "Callable[[Base], int]")
+
+
 -- Attributes
 -- ----------