Return same type as the original index for .loc operations (#15717)

Fixes: #15716 

This PR makes changes to `.loc` by preserving the original type at the end of the operation.

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

Approvers:
  - Matthew Roeschke (https://github.com/mroeschke)

URL: #15717

python/cudf/cudf/core/dataframe.py

@@ -357,6 +357,11 @@ def _getitem_tuple_arg(self, arg):
                     # as join is not assigning any names to index,
                     # update it over here
                     df.index.name = columns_df.index.name
+                    if not isinstance(
+                        df.index, MultiIndex
+                    ) and is_numeric_dtype(df.index.dtype):
+                        # Preserve the original index type.
+                        df.index = df.index.astype(self._frame.index.dtype)
                     df = df.sort_values(by=[tmp_col_name, cantor_name])
                     df.drop(columns=[tmp_col_name, cantor_name], inplace=True)
                     # There were no indices found

python/cudf/cudf/tests/test_dataframe.py

@@ -11010,3 +11010,21 @@ def test_dataframe_init_with_nans():
     assert gdf["a"].dtype == np.dtype("float64")
     pdf = pd.DataFrame({"a": [1, 2, 3, np.nan]})
     assert_eq(pdf, gdf)
+
+
+@pytest.mark.parametrize("dtype1", ["int16", "float32"])
+@pytest.mark.parametrize("dtype2", ["int16", "float32"])
+def test_dataframe_loc_int_float(dtype1, dtype2):
+    df = cudf.DataFrame(
+        {"a": [10, 11, 12, 13, 14]},
+        index=cudf.Index([1, 2, 3, 4, 5], dtype=dtype1),
+    )
+    pdf = df.to_pandas()
+
+    gidx = cudf.Index([2, 3, 4], dtype=dtype2)
+    pidx = gidx.to_pandas()
+
+    actual = df.loc[gidx]
+    expected = pdf.loc[pidx]
+
+    assert_eq(actual, expected, check_index_type=True, check_dtype=True)