Extend W0236 checker to detect return type mismatches in overridden methods

doc/whatsnew/fragments/10351.false_negative

@@ -0,0 +1,5 @@
+Enhanced `invalid-overridden-method` checker to detect return type mismatches when overriding methods.
+The checker now properly identifies when subclass methods have incompatible return types compared to their parent methods,
+including support for covariant return types and proper `typing.Any` handling.
+
+Closes #10351

pylint/checkers/classes/class_checker.py

@@ -33,6 +33,7 @@
     is_iterable,
     is_property_setter,
     is_property_setter_or_deleter,
+    is_subclass_of,
     node_frame_class,
     only_required_for_messages,
     safe_infer,
@@ -1510,6 +1511,38 @@ def _check_invalid_overridden_method(
                 node=function_node,
             )
 
+        # Check for return type mismatches
+        parent_returns = parent_function_node.returns
+        current_returns = function_node.returns
+
+        # Only check if both methods have return type annotations
+        if parent_returns is not None and current_returns is not None:
+            parent_return_type = safe_infer(parent_returns)
+            current_return_type = safe_infer(current_returns)
+
+            if (
+                parent_return_type
+                and current_return_type
+                and isinstance(parent_return_type, nodes.ClassDef)
+                and isinstance(current_return_type, nodes.ClassDef)
+            ):
+                # Check for compatibility
+                compatible = self._are_return_types_compatible(
+                    current_return_type, parent_return_type
+                )
+
+                # Emit error if not compatible
+                if not compatible:
+                    self.add_message(
+                        "invalid-overridden-method",
+                        args=(
+                            function_node.name,
+                            f"return type '{parent_return_type.name}'",
+                            f"return type '{current_return_type.name}'",
+                        ),
+                        node=function_node,
+                    )
+
     def _check_functools_or_not(self, decorator: nodes.Attribute) -> bool:
         if decorator.attrname != "cached_property":
             return False
@@ -2056,6 +2089,7 @@ def _check_accessed_members(
                 node.local_attr(attr)
                 # yes, stop here
                 continue
+
             except astroid.NotFoundError:
                 pass
             # is it an instance attribute of a parent class ?
@@ -2393,6 +2427,34 @@ def _check_signature(
                 "signature-differs", args=(class_type, method1.name), node=method1
             )
 
+    def _are_return_types_compatible(
+        self, current_type: nodes.ClassDef, parent_type: nodes.ClassDef
+    ) -> bool:
+        """Check if current_type is compatible with parent_type for return type
+        checking.
+
+        Compatible means:
+        1. Same type (qname match)
+        2. current_type is a subclass of parent_type (covariance)
+        3. parent_type is typing.Any (any type is compatible with Any)
+        """
+        # Same type check
+        if current_type.qname() == parent_type.qname():
+            return True
+
+        # Special case: Any type accepts anything
+        if parent_type.qname() == "typing.Any":
+            return True
+
+        # Covariant check - current is subclass of parent
+        if is_subclass_of(current_type, parent_type):
+            return True
+
+        # For built-in types, also check by qualified name in ancestors
+        parent_qname = parent_type.qname()
+        current_ancestors = {ancestor.qname() for ancestor in current_type.ancestors()}
+        return parent_qname in current_ancestors
+
     def _uses_mandatory_method_param(
         self, node: nodes.Attribute | nodes.Assign | nodes.AssignAttr
     ) -> bool:

tests/functional/i/invalid/invalid_overridden_method.py

@@ -1,5 +1,6 @@
 # pylint: disable=missing-docstring,too-few-public-methods,disallowed-name,invalid-name,unused-argument
 import abc
+from io import TextIOWrapper, BytesIO
 
 
 class SuperClass(metaclass=abc.ABCMeta):
@@ -125,3 +126,25 @@ def bar(self):  # [invalid-overridden-method]
     @multiple_returns
     def bar2(self):  # [invalid-overridden-method]
         return False
+
+
+# https://github.com/pylint-dev/pylint/issues/10351
+# Test case for return type mismatch
+class ReturnType(TextIOWrapper):
+    pass
+
+class BaseClass(abc.ABC):
+    @abc.abstractmethod
+    def read_file(self, path: str) -> TextIOWrapper:
+        """Abstract method that should return a TextIOWrapper."""
+        raise NotImplementedError("Method must be implemented by subclass")
+
+class ChildClass1(BaseClass):
+    def read_file(self, path: str) -> BytesIO:  # [invalid-overridden-method]
+        """Implementation returns BytesIO instead of TextIOWrapper."""
+        return BytesIO(b"content")
+
+class ChildClass2(BaseClass):
+    def read_file(self, path: str) -> ReturnType:
+        """Implementation returns BytesIO instead of TextIOWrapper."""
+        return ReturnType(BytesIO(b"content"))

tests/functional/i/invalid/invalid_overridden_method.txt

@@ -1,6 +1,7 @@
-invalid-overridden-method:38:4:38:12:InvalidDerived.prop:Method 'prop' was expected to be 'property', found it instead as 'method':UNDEFINED
-invalid-overridden-method:41:4:41:20:InvalidDerived.async_method:Method 'async_method' was expected to be 'async', found it instead as 'non-async':UNDEFINED
-invalid-overridden-method:45:4:45:16:InvalidDerived.method_a:Method 'method_a' was expected to be 'method', found it instead as 'property':UNDEFINED
-invalid-overridden-method:48:4:48:22:InvalidDerived.method_b:Method 'method_b' was expected to be 'non-async', found it instead as 'async':UNDEFINED
-invalid-overridden-method:122:4:122:11:B.bar:Method 'bar' was expected to be 'property', found it instead as 'method':UNDEFINED
-invalid-overridden-method:126:4:126:12:B.bar2:Method 'bar2' was expected to be 'property', found it instead as 'method':UNDEFINED
+invalid-overridden-method:39:4:39:12:InvalidDerived.prop:Method 'prop' was expected to be 'property', found it instead as 'method':UNDEFINED
+invalid-overridden-method:42:4:42:20:InvalidDerived.async_method:Method 'async_method' was expected to be 'async', found it instead as 'non-async':UNDEFINED
+invalid-overridden-method:46:4:46:16:InvalidDerived.method_a:Method 'method_a' was expected to be 'method', found it instead as 'property':UNDEFINED
+invalid-overridden-method:49:4:49:22:InvalidDerived.method_b:Method 'method_b' was expected to be 'non-async', found it instead as 'async':UNDEFINED
+invalid-overridden-method:123:4:123:11:B.bar:Method 'bar' was expected to be 'property', found it instead as 'method':UNDEFINED
+invalid-overridden-method:127:4:127:12:B.bar2:Method 'bar2' was expected to be 'property', found it instead as 'method':UNDEFINED
+invalid-overridden-method:143:4:143:17:ChildClass1.read_file:Method 'read_file' was expected to be "return type 'TextIOWrapper'", found it instead as "return type 'BytesIO'":UNDEFINED