Add testDeprecateFunctionAlreadyDecorated.

test-data/unit/fine-grained.test

@@ -10836,3 +10836,36 @@ b.py:1: note: function a.f is deprecated: use f1 instead
 main:1: note: function a.f is deprecated: use f1 instead
 main:4: note: function a.f is deprecated: use f1 instead
 ==
+
+[case testDeprecateFunctionAlreadyDecorated]
+from b import f
+x: str = f()
+import b
+y: str = b.f()
+
+[file b.py]
+from a import f
+
+[file a.py]
+from typing import Callable
+
+def d(t: Callable[[], str]) -> Callable[[], str]: ...
+
+@d
+def f() -> str: ...
+
+[file a.py.2]
+from typing import Callable
+from typing_extensions import deprecated
+
+def d(t: Callable[[], str]) -> Callable[[], str]: ...
+
+@deprecated("deprecated decorated function")
+@d
+def f() -> str: ...
+
+[builtins fixtures/tuple.pyi]
+[out]
+==
+main:2: note: deprecated decorated function
+main:4: note: deprecated decorated function