fix: precise_diff inconsistent with pendulum.DateTime subclasses

The  Rust helper used  for dt1
but  for dt2. Since
is a subclass of ,  returns False for it,
causing dt2's time components to be left at zero. This led to incorrect
interval calculations when using native  objects (which get
converted to  in ).

Fixes #906

Author: osc-bot

rust/src/python/helpers.rs

@@ -184,7 +184,7 @@ pub fn precise_diff<'py>(
         total_seconds: 0,
         tz: dt2_tz.as_str(),
         offset: get_offset(dt2)?,
-        is_datetime: PyDateTime::is_exact_type_of(dt2),
+        is_datetime: PyDateTime::is_type_of(dt2),
     };
     let in_same_tz: bool = dtinfo1.tz == dtinfo2.tz && !dtinfo1.tz.is_empty();
     let mut total_days = helpers::day_number(dtinfo2.year, dtinfo2.month as u8, dtinfo2.day as u8)

tests/interval/test_construct.py

@@ -18,6 +18,29 @@ def test_with_datetimes():
     assert_datetime(p.end, 2000, 1, 31)
 
 
+def test_native_datetime_interval_consistency():
+    """Native datetime inputs should produce the same results as pendulum datetimes.
+
+    Regression test for https://github.com/python-pendulum/pendulum/issues/906
+    """
+    # With pendulum datetimes
+    start_p = pendulum.datetime(2025, 7, 25, 19, 26, 34)
+    end_p = pendulum.datetime(2025, 7, 29, 19, 26, 34)
+    interval_p = pendulum.interval(start_p, end_p)
+
+    # With native datetimes
+    start_n = datetime(2025, 7, 25, 19, 26, 34)
+    end_n = datetime(2025, 7, 29, 19, 26, 34)
+    interval_n = pendulum.interval(start_n, end_n)
+
+    # Both should produce identical results
+    assert interval_p.in_words() == interval_n.in_words()
+    assert interval_p.in_words() == "4 days"
+    assert interval_p.days == interval_n.days == 4
+    assert interval_p.hours == interval_n.hours == 0
+    assert interval_p.minutes == interval_n.minutes == 0
+
+
 def test_with_pendulum():
     dt1 = pendulum.DateTime(2000, 1, 1)
     dt2 = pendulum.DateTime(2000, 1, 31)