fix[rust]: keep logical type in deep-clone unstable series (#4520)

polars/polars-core/src/series/unstable.rs

@@ -1,4 +1,3 @@
-use std::convert::TryFrom;
 use std::marker::PhantomData;
 use std::ptr::NonNull;
 
@@ -56,9 +55,13 @@ impl<'a> UnstableSeries<'a> {
     }
 
     pub fn deep_clone(&self) -> Series {
-        let array_ref = unsafe { (*self.container).chunks() }[0].clone();
-        let name = unsafe { (*self.container).name() };
-        Series::try_from((name, array_ref)).unwrap()
+        unsafe {
+            let s = &(*self.container);
+            debug_assert_eq!(s.chunks().len(), 1);
+            let array_ref = s.chunks().get_unchecked(0).clone();
+            let name = s.name();
+            Series::from_chunks_and_dtype_unchecked(name, vec![array_ref], s.dtype())
+        }
     }
 
     #[inline]

py-polars/tests/test_datelike.py

@@ -1303,3 +1303,19 @@ def test_date_parse_omit_day() -> None:
     assert df.select(pl.col("month").str.strptime(pl.Datetime, fmt="%Y-%m"))[
         0, 0
     ] == datetime(2022, 1, 1)
+
+
+def test_shift_and_fill_group_logicals() -> None:
+    df = pl.from_records(
+        [
+            (date(2001, 1, 2), "A"),
+            (date(2001, 1, 3), "A"),
+            (date(2001, 1, 4), "A"),
+            (date(2001, 1, 3), "B"),
+            (date(2001, 1, 4), "B"),
+        ],
+        columns=["d", "s"],
+    )
+    assert df.select(
+        pl.col("d").shift_and_fill(-1, pl.col("d").max()).over("s")
+    ).dtypes == [pl.Date]