Fix issue with column and scalar re-assignment (#10377)

Fixes: #10305  This PR fixes issues where the `scalar` that is being assigned was being type-casted to the column's type. Added test coverage for the same.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Bradley Dice (https://github.com/bdice)

URL: #10377

python/cudf/cudf/core/dataframe.py

@@ -1161,7 +1161,9 @@ def __setitem__(self, arg, value):
                             allow_non_unique=True,
                         )
                     if is_scalar(value):
-                        self._data[arg][:] = value
+                        self._data[arg] = utils.scalar_broadcast_to(
+                            value, len(self)
+                        )
                     else:
                         value = as_column(value)
                         self._data[arg] = value

python/cudf/cudf/tests/test_setitem.py

@@ -33,9 +33,14 @@ def test_dataframe_setitem_scaler_bool():
     assert_eq(df, gdf)
 
 
-@pytest.mark.parametrize("df", [pd.DataFrame({"a": [1, 2, 3]})])
+@pytest.mark.parametrize(
+    "df",
+    [pd.DataFrame({"a": [1, 2, 3]}), pd.DataFrame({"a": ["x", "y", "z"]})],
+)
 @pytest.mark.parametrize("arg", [["a"], "a", "b"])
-@pytest.mark.parametrize("value", [-10, pd.DataFrame({"a": [-1, -2, -3]})])
+@pytest.mark.parametrize(
+    "value", [-10, pd.DataFrame({"a": [-1, -2, -3]}), "abc"]
+)
 def test_dataframe_setitem_columns(df, arg, value):
     gdf = cudf.from_pandas(df)
     cudf_replace_value = value