Fix FP for no-member: function attributes from decorator (#9308)

doc/whatsnew/fragments/9246.false_positive

@@ -0,0 +1,4 @@
+Avoid false positives for ``no-member`` involving function
+attributes supplied by decorators.
+
+Closes #9246

pylint/checkers/typecheck.py

@@ -1060,7 +1060,7 @@ def visit_assignattr(self, node: nodes.AssignAttr) -> None:
     def visit_delattr(self, node: nodes.DelAttr) -> None:
         self.visit_attribute(node)
 
-    # pylint: disable = too-many-branches
+    # pylint: disable = too-many-branches, too-many-statements
     @only_required_for_messages("no-member", "c-extension-no-member")
     def visit_attribute(
         self, node: nodes.Attribute | nodes.AssignAttr | nodes.DelAttr
@@ -1128,6 +1128,12 @@ def visit_attribute(
             except astroid.DuplicateBasesError:
                 continue
             except astroid.NotFoundError:
+                # Avoid false positive in case a decorator supplies member.
+                if (
+                    isinstance(owner, (astroid.FunctionDef, astroid.BoundMethod))
+                    and owner.decorators
+                ):
+                    continue
                 # This can't be moved before the actual .getattr call,
                 # because there can be more values inferred and we are
                 # stopping after the first one which has the attribute in question.

tests/functional/n/no/no_member_decorator.py

@@ -0,0 +1,16 @@
+"""Attributes supplied by a decorator."""
+
+from functools import lru_cache
+
+
+class SomeClass:  # pylint: disable=too-few-public-methods
+    """https://github.com/pylint-dev/pylint/issues/9246"""
+    @classmethod
+    @lru_cache
+    def __cached_fun(cls, arg: int) -> str:
+        return str(arg)
+
+    @classmethod
+    def cache_clear(cls):
+        """__cached_fun()'s @cache decorator supplies cache_clear()."""
+        cls.__cached_fun.cache_clear()