py: Replace mp_const_stop_iteration object with MP_OBJ_NULL.

py/vm.c

@@ -430,8 +430,8 @@ unwind_jump:
 
                     case MP_BC_FOR_ITER:
                         DECODE_ULABEL; // the jump offset if iteration finishes; for labels are always forward
-                        obj1 = rt_iternext(TOP());
-                        if (obj1 == mp_const_stop_iteration) {
+                        obj1 = rt_iternext_allow_raise(TOP());
+                        if (obj1 == MP_OBJ_NULL) {
                             --sp; // pop the exhausted iterator
                             ip += unum; // jump to after for-block
                         } else {

tests/basics/iter1.py

+# test user defined iterators
+
+class MyStopIteration(StopIteration):
+    pass
+
+class myiter:
+    def __init__(self, i):
+        self.i = i
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self.i <= 0:
+            # stop in the usual way
+            raise StopIteration
+        elif self.i == 10:
+            # stop with an argument
+            raise StopIteration(42)
+        elif self.i == 20:
+            # raise a non-stop exception
+            raise TypeError
+        elif self.i == 30:
+            # raise a user-defined stop iteration
+            print('raising MyStopIteration')
+            raise MyStopIteration
+        else:
+            # return the next value
+            self.i -= 1
+            return self.i
+
+for i in myiter(5):
+    print(i)
+
+for i in myiter(12):
+    print(i)
+
+try:
+    for i in myiter(22):
+        print(i)
+except TypeError:
+    print('raised TypeError')
+
+try:
+    for i in myiter(5):
+        print(i)
+        raise StopIteration
+except StopIteration:
+    print('raised StopIteration')
+
+for i in myiter(32):
+    print(i)

tests/basics/iter2.py

+# user defined iterator used in something other than a for loop
+
+class MyStopIteration(StopIteration):
+    pass
+
+class myiter:
+    def __init__(self, i):
+        self.i = i
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self.i == 0:
+            raise StopIteration
+        elif self.i == 1:
+            raise StopIteration(1)
+        elif self.i == 2:
+            raise MyStopIteration
+
+print(list(myiter(0)))
+print(list(myiter(1)))
+print(list(myiter(2)))