[fx] Make the lift_fresh_copy -> clone special form use kwargs. (#3045)

At some point, this op became kwarg-only instead of arg/kwarg.
Discovered when upgrading to PyTorch 2.3.

Also adds a test as this was untested in-tree (was caught out of tree).

python/torch_mlir/extras/fx_importer.py

@@ -1276,10 +1276,16 @@ class GraphNodeImporter:
         # replace lift_fresh_copy with clone op
         if target == torch.ops.aten.lift_fresh_copy.default:
             node.target = target = torch.ops.aten.clone.default
-            node.args = (node.args[0], None)
+            node.args = (node.args[0],)
+            node.kwargs = {"memory_format": None}
         elif target == torch.ops.aten.lift_fresh_copy.out:
+            # TODO: It seems not possible to hit this case from user code.
+            # Retaining in case if it is triggered internally somehow, but
+            # it can most likely be removed once assuming full
+            # functionalization in all cases.
             node.target = target = torch.ops.aten.clone.out
-            node.args = (node.args[0], None, node.args[1])
+            node.args = (node.args[0],)
+            node.kwargs = {"memory_format": None, "out": node.args[1]}
         # TODO: generalize empty.memory_format in the future
         # Currently, the aten.baddbmm.default op for Unet includes multiplying an
         # empty.memory_format input with a constant, which creates NaN values
@@ -1664,7 +1670,8 @@ class TypeSubclassMap:
 
 # Opaque value to indicate something is empty. Used in cases where 'None'
 # may have a different meaning.
-class EmptyType: ...
+class EmptyType:
+    ...
 
 
 Empty = EmptyType()

test/python/fx_importer/special_forms_test.py

@@ -0,0 +1,36 @@
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+# Also available under a BSD-style license. See LICENSE.
+
+# RUN: %PYTHON %s | FileCheck %s
+# This file contains tests of various op special forms that the fx_importer
+# handles.
+
+from typing import Optional
+
+import torch
+import torch.export
+import torch.nn as nn
+
+from torch_mlir import fx
+
+
+def run(f):
+    print(f"{f.__name__}")
+    print("-" * len(f.__name__))
+    f()
+    print()
+
+
+@run
+# CHECK-LABEL: test_lift_fresh_copy
+def test_lift_fresh_copy():
+    #
+    class Basic(nn.Module):
+        def forward(self, x):
+            # CHECK: torch.aten.clone %arg0, %none
+            return torch.ops.aten.lift_fresh_copy.default(x)
+
+    m = fx.export_and_import(Basic(), torch.randn(3, 4))
+    print(m)