[list] Add list.__mul__ and list.__imul__ (#156271)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/156271
Approved by: https://github.com/zou3519
ghstack dependencies: #153969, #156148, #156242, #156270

test/dynamo/test_list.py

@@ -59,6 +59,20 @@ class TupleTests(torch._dynamo.test_case.TestCase):
         # Wrong number of arguments
         self.assertRaises(TypeError, p.index)
 
+    @make_dynamo_test
+    def test_binop_imul(self):
+        p = self.thetype([1, 2, 3])
+        r = p.__mul__(2)
+        self.assertIsInstance(r, self.thetype)
+        self.assertEqual(r, self.thetype([1, 2, 3, 1, 2, 3]))
+        self.assertEqual(p, self.thetype([1, 2, 3]))
+
+        # Wrong number of arguments
+        self.assertRaises(TypeError, p.__mul__)
+
+        # can only multiply list by an integer
+        self.assertRaises(TypeError, p.__mul__, 2.2)
+
     @make_dynamo_test
     def test_binop_add(self):
         p, q = map(self.thetype, ["abc", "bcd"])
@@ -276,6 +290,39 @@ class ListTests(TupleTests):
         self.assertIsNone(p.sort())
         self.assertEqual(p, self.thetype("abcd"))
 
+    @make_dynamo_test
+    def test_binop_imul(self):
+        p = self.thetype([1, 2, 3])
+        r = p.__imul__(2)
+        self.assertIsInstance(r, self.thetype)
+        self.assertEqual(r, self.thetype([1, 2, 3, 1, 2, 3]))
+        self.assertEqual(p, self.thetype([1, 2, 3, 1, 2, 3]))
+
+        p = self.thetype("ab")
+        p *= 2
+        self.assertEqual(p, self.thetype("abab"))
+
+        # Wrong number of arguments
+        self.assertRaises(TypeError, p.__imul__)
+
+        # can only multiply list by an integer
+        self.assertRaises(TypeError, p.__imul__, 2.2)
+
+    def test_binop_imul_global_list(self):
+        global lst
+        lst = self.thetype(["a", "b"])
+
+        @torch.compile(backend="eager", fullgraph=True)
+        def fn(x):
+            global lst
+            lst *= 2
+            lst.__imul__(3)
+            return x.sin()
+
+        x = torch.tensor(1.0)
+        self.assertEqual(fn(x), x.sin())
+        self.assertEqual(lst, ["a", "b"] * 6)
+
     @make_dynamo_test
     def test_binop_iadd(self):
         p, q = map(self.thetype, ["abc", "bcd"])

torch/_dynamo/variables/lists.py

@@ -206,6 +206,23 @@ class BaseListVariable(VariableTracker):
             else:
                 self.items += args[0].items
                 return self
+        elif name in ("__mul__", "__imul__"):
+            if kwargs or len(args) != 1:
+                raise_args_mismatch(tx, name)
+
+            if not (args[0].is_python_constant() and args[0].python_type() is int):
+                msg = ConstantVariable.create(
+                    f"can't multiply sequence by non-int type of '{args[0].python_type_name()}'"
+                )
+                raise_observed_exception(TypeError, tx, args=[msg])
+
+            val = args[0].as_python_constant()
+
+            if name == "__mul__":
+                return type(self)(self.items * val, source=self.source)
+            else:
+                self.items *= val
+                return self
         elif name in cmp_name_to_op_mapping:
             if len(args) != 1:
                 raise_args_mismatch(tx, name)