bpo-37976: Prevent shadowing of TypeError in zip() (GH-15592)

Author: sir-sigurd

Lib/test/test_builtin.py

@@ -1477,6 +1477,18 @@ def test_zip_pickle(self):
             z1 = zip(a, b)
             self.check_iter_pickle(z1, t, proto)
 
+    def test_zip_bad_iterable(self):
+        exception = TypeError()
+
+        class BadIterable:
+            def __iter__(self):
+                raise exception
+
+        with self.assertRaises(TypeError) as cm:
+            zip(BadIterable())
+
+        self.assertIs(cm.exception, exception)
+
     def test_format(self):
         # Test the basic machinery of the format() builtin.  Don't test
         #  the specifics of the various formatters

Lib/test/test_itertools.py

@@ -971,6 +971,18 @@ def test_zip_longest_pickling(self):
             self.pickletest(proto, zip_longest("abc", "defgh", fillvalue=1))
             self.pickletest(proto, zip_longest("", "defgh"))
 
+    def test_zip_longest_bad_iterable(self):
+        exception = TypeError()
+
+        class BadIterable:
+            def __iter__(self):
+                raise exception
+
+        with self.assertRaises(TypeError) as cm:
+            zip_longest(BadIterable())
+
+        self.assertIs(cm.exception, exception)
+
     def test_bug_7244(self):
 
         class Repeater:

Modules/itertoolsmodule.c

@@ -4442,10 +4442,6 @@ zip_longest_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         PyObject *item = PyTuple_GET_ITEM(args, i);
         PyObject *it = PyObject_GetIter(item);
         if (it == NULL) {
-            if (PyErr_ExceptionMatches(PyExc_TypeError))
-                PyErr_Format(PyExc_TypeError,
-                    "zip_longest argument #%zd must support iteration",
-                    i+1);
             Py_DECREF(ittuple);
             return NULL;
         }

Python/bltinmodule.c

@@ -2548,10 +2548,6 @@ zip_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         PyObject *item = PyTuple_GET_ITEM(args, i);
         PyObject *it = PyObject_GetIter(item);
         if (it == NULL) {
-            if (PyErr_ExceptionMatches(PyExc_TypeError))
-                PyErr_Format(PyExc_TypeError,
-                    "zip argument #%zd must support iteration",
-                    i+1);
             Py_DECREF(ittuple);
             return NULL;
         }