[dynamo] Fix source for lru_cache method (pytorch#157292)

Fixes - pytorch#157273

Pull Request resolved: pytorch#157292
Approved by: https://github.com/zou3519, https://github.com/malfet, https://github.com/jansel

Author: anijain2305

test/dynamo/test_functions.py

@@ -4132,6 +4132,21 @@ def fn(x):
         opt_fn = torch.compile(fn, backend="eager", fullgraph=True)
         self.assertEqual(fn(x), opt_fn(x))
 
+    def test_functools_cache_guard(self):
+        class Foo:
+            @functools.lru_cache  # noqa: B019
+            def run(self, val, c=1.0):
+                return val * c * 2
+
+        f = Foo()
+
+        def fn(x):
+            return f.run(x)
+
+        x = torch.randn(2)
+        opt_fn = torch.compile(fn, backend="eager", fullgraph=True)
+        self.assertEqual(fn(x), opt_fn(x))
+
 
 def udf_mul(x, y):
     return x * y

torch/_dynamo/variables/user_defined.py

@@ -1266,7 +1266,7 @@ def var_getattr(self, tx: "InstructionTranslator", name):
             # extract the underlying method from the wrapped function. To handle
             # it, manually create a wrapped user method vt.
             return variables.WrapperUserMethodVariable(
-                subobj, "__wrapped__", self, source=self.source
+                subobj, "__wrapped__", self, source=source
             )
         elif inspect.getattr_static(
             type(subobj), "__get__", NO_SUCH_SUBOBJ