Merge branch 'master' into fix-issue-10244

1 files changed, 23 insertions, 0 deletions

diff --git a/numpy/lib/tests/test_polynomial.py b/numpy/lib/tests/test_polynomial.py
index cd0b90dc4..6c3e4fa02 100644
--- a/numpy/lib/tests/test_polynomial.py
+++ b/numpy/lib/tests/test_polynomial.py
@@ -227,6 +227,20 @@ class TestPolynomial:
         v = np.arange(1, 21)
         assert_almost_equal(np.poly(v), np.poly(np.diag(v)))
 
+    def test_zero_poly_dtype(self):
+        """
+        Regression test for gh-16354.
+        """
+        z = np.array([0, 0, 0])
+        p = np.poly1d(z.astype(np.int64))
+        assert_equal(p.coeffs.dtype, np.int64)
+
+        p = np.poly1d(z.astype(np.float32))
+        assert_equal(p.coeffs.dtype, np.float32)
+
+        p = np.poly1d(z.astype(np.complex64))
+        assert_equal(p.coeffs.dtype, np.complex64)
+
     def test_poly_eq(self):
         p = np.poly1d([1, 2, 3])
         p2 = np.poly1d([1, 2, 4])
@@ -243,6 +257,15 @@ class TestPolynomial:
         assert_equal(q.coeffs.dtype, np.complex128)
         assert_equal(r.coeffs.dtype, np.complex128)
         assert_equal(q*a + r, b)
+        
+        c = [1, 2, 3]
+        d = np.poly1d([1, 2, 3])
+        s, t = np.polydiv(c, d)
+        assert isinstance(s, np.poly1d)
+        assert isinstance(t, np.poly1d)
+        u, v = np.polydiv(d, c)
+        assert isinstance(u, np.poly1d)
+        assert isinstance(v, np.poly1d)
 
     def test_poly_coeffs_mutable(self):
         """ Coefficients should be modifiable """