BUG: fix broadcast_to for reference types

numpy/lib/stride_tricks.py

@@ -60,9 +60,9 @@ def _broadcast_to(array, shape, subok, readonly):
     if any(size < 0 for size in shape):
         raise ValueError('all elements of broadcast shape must be non-'
                          'negative')
-    broadcast = np.nditer((array,), flags=['multi_index', 'zerosize_ok'],
-                          op_flags=['readonly'], itershape=shape, order='C'
-                          ).itviews[0]
+    broadcast = np.nditer(
+        (array,), flags=['multi_index', 'refs_ok', 'zerosize_ok'],
+        op_flags=['readonly'], itershape=shape, order='C').itviews[0]
     result = _maybe_view_as_subclass(array, broadcast)
     if not readonly and array.flags.writeable:
         result.flags.writeable = True

numpy/lib/tests/test_stride_tricks.py

@@ -364,5 +364,15 @@ def test_writeable():
     assert_equal(result.flags.writeable, False)
 
 
+def test_reference_types():
+    input_array = np.array('a', dtype=object)
+    expected = np.array(['a'] * 3, dtype=object)
+    actual = broadcast_to(input_array, (3,))
+    assert_array_equal(expected, actual)
+
+    actual, _ = broadcast_arrays(input_array, np.ones(3))
+    assert_array_equal(expected, actual)
+
+
 if __name__ == "__main__":
     run_module_suite()