NA Compat

pandas/core/indexes/interval.py

@@ -980,16 +980,20 @@ def delete(self, loc):
 
     def insert(self, loc, item):
         if isinstance(item, Interval):
-            if not item.closed == self.closed:
+            if item.closed != self.closed:
                 raise ValueError('inserted item must be closed on the same '
                                  'side as the index')
             left_insert = item.left
             right_insert = item.right
         elif is_scalar(item) and isna(item):
             # GH 18295
+            if item is not self.left._na_value:
+                raise TypeError('cannot insert with incompatible NA value: '
+                                'got {item}, expected {na}'
+                                .format(item=item, na=self.left._na_value))
             left_insert = right_insert = item
         else:
-            raise ValueError('can only insert Interval objects and NaN into '
+            raise ValueError('can only insert Interval objects and NA into '
                              'an IntervalIndex')
 
         new_left = self.left.insert(loc, left_insert)

pandas/tests/indexes/test_interval.py

@@ -255,11 +255,30 @@ def test_insert(self):
         pytest.raises(ValueError, self.index.insert, 0,
                       Interval(2, 3, closed='left'))
 
+    @pytest.mark.parametrize('data', [
+        interval_range(0, periods=10),
+        interval_range(1.7, periods=8, freq=2.5),
+        interval_range(Timestamp('20170101'), periods=12),
+        interval_range(Timedelta('1 day'), periods=6),
+        IntervalIndex.from_tuples([('a', 'd'), ('e', 'j'), ('w', 'z')]),
+        IntervalIndex.from_tuples([(1, 2), ('a', 'z'), (3.14, 6.28)])])
+    def test_insert_na(self, data):
         # GH 18295
-        expected = self.index_with_nan
-        result = self.index.insert(1, np.nan)
+        valid_na, invalid_na = np.nan, pd.NaT
+        if data.left._na_value is pd.NaT:
+            valid_na, invalid_na = invalid_na, valid_na
+
+        # valid insertion
+        expected = IntervalIndex([data[0], np.nan]).append(data[1:])
+        result = data.insert(1, valid_na)
         tm.assert_index_equal(result, expected)
 
+        # invalid insertion
+        msg = ('cannot insert with incompatible NA value: got {invalid}, '
+               'expected {valid}').format(invalid=invalid_na, valid=valid_na)
+        with tm.assert_raises_regex(TypeError, msg):
+            data.insert(1, invalid_na)
+
     def test_take(self):
         actual = self.index.take([0, 1])
         assert self.index.equals(actual)