remove the non-trivial BoxVar constructor

src/core/types.h

@@ -566,10 +566,10 @@ extern "C" PyObject* PystonType_GenericAlloc(BoxedClass* cls, Py_ssize_t nitems)
 // CPython C API compatibility class:
 class BoxVar : public Box {
 public:
+    // This field gets initialized in operator new.
     Py_ssize_t ob_size;
 
     BoxVar() {}
-    BoxVar(Py_ssize_t ob_size) : ob_size(ob_size) {}
 
     void* operator new(size_t size, BoxedClass* cls, size_t nitems) __attribute__((visibility("default")));
 };

src/runtime/objmodel.cpp

@@ -312,7 +312,7 @@ void BoxedClass::freeze() {
 
 BoxedClass::BoxedClass(BoxedClass* base, gcvisit_func gc_visit, int attrs_offset, int weaklist_offset,
                        int instance_size, bool is_user_defined)
-    : BoxVar(0), gc_visit(gc_visit), simple_destructor(NULL), attrs_offset(attrs_offset), is_constant(false),
+    : gc_visit(gc_visit), simple_destructor(NULL), attrs_offset(attrs_offset), is_constant(false),
       is_user_defined(is_user_defined), is_pyston_class(true) {
 
     // Zero out the CPython tp_* slots: