BUG: Fix failed itemsetting in fromiter

Seems we never had a test for this simple path...

Author: seberg

numpy/core/src/multiarray/ctors.c

@@ -3968,7 +3968,7 @@ PyArray_FromIter(PyObject *obj, PyArray_Descr *dtype, npy_intp count)
             }
         }
 
-        if (PyArray_Pack(dtype, item, value) < -1) {
+        if (PyArray_Pack(dtype, item, value) < 0) {
             Py_DECREF(value);
             goto done;
         }

numpy/core/tests/test_numeric.py

@@ -1256,6 +1256,14 @@ def test_too_few_items(self):
         with pytest.raises(ValueError, match=msg):
             np.fromiter([1, 2, 3], count=10, dtype=int)
 
+    def test_failed_itemsetting(self):
+        with pytest.raises(TypeError):
+            np.fromiter([1, None, 3], dtype=int)
+
+        # The following manages to hit somewhat trickier code paths:
+        iterable = ((2, 3, 4) for i in range(5))
+        with pytest.raises(ValueError):
+            np.fromiter(iterable, dtype=np.dtype((int, 2)))
 
 class TestNonzero:
     def test_nonzero_trivial(self):