[fix] ltorch.to to return a copy, when copy=True

thunder/tests/test_core.py

@@ -1865,6 +1865,20 @@ def torch_to(a, memory_format):
         assert_close(torch_result, thunder_result, check_stride=True)
 
 
+def test_torch_tensor_to_return_type():
+    a = torch.randn(2, 4, 5, 3)
+
+    def torch_to(a):
+        return a.to(copy=True)
+
+    jfoo = thunder.jit(torch_to)
+    thunder_result = jfoo(a)
+    torch_result = torch_to(a)
+
+    assert thunder_result is not a
+    assert_close(torch_result, thunder_result)
+
+
 # TODO See issue "Add contiguous and clang.stride_order OpInfos that check stride
 # consistency with PyTorch"
 @instantiate(

thunder/torch/__init__.py

@@ -472,6 +472,13 @@ def to(
     copy: bool = False,
     memory_format: None | torch.memory_format = None,
 ) -> TensorLike:
+
+    input_device = a.device
+    input_dtype = a.dtype
+    if copy and not _will_to_return_self(input_device, input_dtype, device, dtype, memory_format, copy):
+        b = prims.empty(a.shape, device=input_device, dtype=input_dtype)
+        return _copy_(b, a)
+
     device, dtype = _parse_to_device_and_dtype(
         tensor_dtype_or_device, optional_positional_dtype, device=device, dtype=dtype
     )