Undo Revert "remove dead code in arrays/interval.py"

This reverts commit 84b119f.

Author: Dr-Irv

pandas/core/arrays/interval.py

@@ -1664,8 +1664,12 @@ def _from_combined(self, combined: np.ndarray) -> IntervalArray:
         nc = combined.view("i8").reshape(-1, 2)
 
         dtype = self._left.dtype
-        new_left = nc[:, 0].view(dtype)
-        new_right = nc[:, 1].view(dtype)
+        if needs_i8_conversion(dtype):
+            new_left = type(self._left)._from_sequence(nc[:, 0], dtype=dtype)
+            new_right = type(self._right)._from_sequence(nc[:, 1], dtype=dtype)
+        else:
+            new_left = nc[:, 0].view(dtype)
+            new_right = nc[:, 1].view(dtype)
         return self._shallow_copy(left=new_left, right=new_right)
 
     def unique(self) -> IntervalArray: