Get some internal iterator logic working

src/core/types.h

@@ -541,7 +541,16 @@ public:
     BoxIteratorImpl* impl;
 
     BoxIterator(BoxIteratorImpl* impl) : impl(impl) {}
-    ~BoxIterator() = default;
+    BoxIterator(const BoxIterator& rhs) = default;
+    BoxIterator(BoxIterator&& rhs) {
+        impl = rhs.impl;
+        rhs.impl = NULL;
+    }
+
+    ~BoxIterator() {
+        if (impl)
+            impl->~BoxIteratorImpl();
+    }
 
     static llvm::iterator_range<BoxIterator> getRange(Box* container);
     bool operator==(BoxIterator const& rhs) const { return impl->isSame(rhs.impl); }

src/runtime/inline/xrange.cpp

@@ -135,7 +135,10 @@ public:
 
     static void dealloc(Box* b) noexcept {
         BoxedXrangeIterator* self = static_cast<BoxedXrangeIterator*>(b);
+        _PyObject_GC_UNTRACK(self);
         Py_DECREF(self->xrange);
+
+        self->cls->tp_free(self);
     }
     static int traverse(Box* s, visitproc visit, void *arg) noexcept {
         BoxedXrangeIterator* self = static_cast<BoxedXrangeIterator*>(s);

src/runtime/iterators.cpp

@@ -38,14 +38,21 @@ public:
         }
     }
 
+    ~BoxIteratorGeneric() {
+        assert(!value);
+        Py_XDECREF(iterator);
+    }
+
     void next() override {
         STAT_TIMER(t0, "us_timer_iteratorgeneric_next", 0);
+        assert(!value);
 
         Box* next = PyIter_Next(iterator);
         if (next) {
             value = next;
         } else {
             checkAndThrowCAPIException();
+            Py_CLEAR(iterator);
             *this = *end();
         }
     }

src/runtime/list.cpp

@@ -809,7 +809,7 @@ Box* listIAdd(BoxedList* self, Box* _rhs) {
     RELEASE_ASSERT(_rhs != self, "unsupported");
 
     for (auto* b : _rhs->pyElements())
-        listAppendInternal(self, b);
+        listAppendInternalStolen(self, b);
 
     Py_INCREF(self);
     return self;