Fix false positive for inherit-non-class for generic Protocols (#9108) (#9111)

(cherry picked from commit cd4b292)

Co-authored-by: Daniël van Noord <[email protected]>

Author: github-actions[bot]

doc/whatsnew/fragments/9106.false_positive

@@ -0,0 +1,3 @@
+Fixed false positive for ``inherit-non-class`` for generic Protocols.
+
+Closes #9106

pylint/checkers/classes/class_checker.py

@@ -957,8 +957,9 @@ def _check_proper_bases(self, node: nodes.ClassDef) -> None:
             ancestor = safe_infer(base)
             if not ancestor:
                 continue
-            if isinstance(ancestor, astroid.Instance) and ancestor.is_subtype_of(
-                "builtins.type"
+            if isinstance(ancestor, astroid.Instance) and (
+                ancestor.is_subtype_of("builtins.type")
+                or ancestor.is_subtype_of(".Protocol")
             ):
                 continue
 

tests/functional/i/inherit_non_class.py

@@ -4,6 +4,7 @@
 # pylint: disable=import-error, invalid-name, using-constant-test
 # pylint: disable=missing-docstring, too-few-public-methods, useless-object-inheritance
 
+from typing import Protocol, TypeVar
 from missing import Missing
 
 if 1:
@@ -101,3 +102,18 @@ class Child2(ParentBad[int]):  # [inherit-non-class]
 # Classes that don't implement '__class_getitem__' are marked as unsubscriptable
 class Child3(Empty[int]):  # [unsubscriptable-object]
     pass
+
+
+T = TypeVar("T")
+
+
+class Channel(Protocol[T]):
+    """A generic Protocol."""
+
+    async def get(self) -> T:
+        """A get method using the generic."""
+
+
+class DirectChannel(Channel[T]):
+    async def get(self) -> T:
+        """An implementation of the generic."""

tests/functional/i/inherit_non_class.txt

@@ -1,11 +1,11 @@
-inherit-non-class:21:0:21:9:Bad:Inheriting '1', which is not a class.:UNDEFINED
-inherit-non-class:24:0:24:10:Bad1:"Inheriting 'lambda abc: 42', which is not a class.":UNDEFINED
-inherit-non-class:27:0:27:10:Bad2:Inheriting 'object()', which is not a class.:UNDEFINED
-inherit-non-class:30:0:30:10:Bad3:Inheriting 'return_class', which is not a class.:UNDEFINED
-inherit-non-class:33:0:33:10:Bad4:Inheriting 'Empty()', which is not a class.:UNDEFINED
-inherit-non-class:68:0:68:24:NotInheritableBool:Inheriting 'bool', which is not a class.:UNDEFINED
-inherit-non-class:72:0:72:25:NotInheritableRange:Inheriting 'range', which is not a class.:UNDEFINED
-inherit-non-class:76:0:76:25:NotInheritableSlice:Inheriting 'slice', which is not a class.:UNDEFINED
-inherit-non-class:80:0:80:30:NotInheritableMemoryView:Inheriting 'memoryview', which is not a class.:UNDEFINED
-inherit-non-class:98:0:98:12:Child2:Inheriting 'ParentBad[int]', which is not a class.:UNDEFINED
-unsubscriptable-object:102:13:102:18:Child3:Value 'Empty' is unsubscriptable:UNDEFINED
+inherit-non-class:22:0:22:9:Bad:Inheriting '1', which is not a class.:UNDEFINED
+inherit-non-class:25:0:25:10:Bad1:"Inheriting 'lambda abc: 42', which is not a class.":UNDEFINED
+inherit-non-class:28:0:28:10:Bad2:Inheriting 'object()', which is not a class.:UNDEFINED
+inherit-non-class:31:0:31:10:Bad3:Inheriting 'return_class', which is not a class.:UNDEFINED
+inherit-non-class:34:0:34:10:Bad4:Inheriting 'Empty()', which is not a class.:UNDEFINED
+inherit-non-class:69:0:69:24:NotInheritableBool:Inheriting 'bool', which is not a class.:UNDEFINED
+inherit-non-class:73:0:73:25:NotInheritableRange:Inheriting 'range', which is not a class.:UNDEFINED
+inherit-non-class:77:0:77:25:NotInheritableSlice:Inheriting 'slice', which is not a class.:UNDEFINED
+inherit-non-class:81:0:81:30:NotInheritableMemoryView:Inheriting 'memoryview', which is not a class.:UNDEFINED
+inherit-non-class:99:0:99:12:Child2:Inheriting 'ParentBad[int]', which is not a class.:UNDEFINED
+unsubscriptable-object:103:13:103:18:Child3:Value 'Empty' is unsubscriptable:UNDEFINED