#fixed code
                                public void restrictNumType(Compare compare, Scope s1, Scope s2) {
        List<Node> ops = compare.ops;

        if (ops.size() > 0 && ops.get(0) instanceof Op) {
            Op op = ((Op) ops.get(0));
            String opname = op.name;
            if (op.isNumberComparisonOp()) {

                Node left = compare.left;
                Node right = compare.comparators.get(0);
                if (!left.isName()) {
                    Node tmp = right;
                    right = left;
                    left = tmp;
                    opname = Op.invert(opname);
                }

                if (left.isName()) {
                    Name leftName = left.asName();
                    Type leftType = left.resolve(s1);
                    Type rightType = right.resolve(s1);
                    NumType trueType = Analyzer.self.builtins.BaseNum;
                    NumType falseType = Analyzer.self.builtins.BaseNum;

                    if (opname.equals("<") || opname.equals("<=")) {
                        if (leftType.isNumType() && rightType.isNumType()) {
                            NumType newUpper = rightType.asNumType();
                            trueType = new NumType(leftType.asNumType());
                            trueType.setUpper(newUpper.getUpper());
                            falseType = new NumType(leftType.asNumType());
                            falseType.setLower(newUpper.getUpper());
                        } else {
                            Analyzer.self.putProblem(test, "comparing non-numbers: " + leftType + " and " + rightType);
                        }
                    } else if (opname.equals(">") || opname.equals(">=")) {
                        if (leftType.isNumType() && rightType.isNumType()) {
                            NumType newLower = rightType.asNumType();
                            trueType = new NumType(leftType.asNumType());
                            trueType.setLower(newLower.getLower());
                            falseType = new NumType(leftType.asNumType());
                            falseType.setUpper(newLower.getLower());
                        } else {
                            Analyzer.self.putProblem(test, "comparing non-numbers: " + leftType + " and " + rightType);
                        }
                    }

                    Node loc;
                    List<Binding> bs = s1.lookup(leftName.id);
                    if (bs != null && bs.size() > 0) {
                        loc = bs.get(0).getNode();
                    } else {
                        loc = leftName;
                    }

                    s1.update(leftName.id, new Binding(leftName.id, loc, trueType, Binding.Kind.SCOPE));
                    s2.update(leftName.id, new Binding(leftName.id, loc, falseType, Binding.Kind.SCOPE));
                }
            }
        }
    }
#vulnerable code 
                                public void restrictNumType(Compare compare, Scope s1, Scope s2) {
        List<Node> ops = compare.ops;

        if (ops.size() > 0 && ops.get(0) instanceof Op) {
            String opname = ((Op) ops.get(0)).name;
            Node left = compare.left;
            Node right = compare.comparators.get(0);
            if (!left.isName()) {
                Node tmp = right;
                right = left;
                left = tmp;
                opname = Op.invert(opname);
            }

            if (left.isName()) {
                Name leftName = left.asName();
                Type leftType = left.resolve(s1);
                Type rightType = right.resolve(s1);
                NumType trueType = Analyzer.self.builtins.BaseNum;
                NumType falseType = Analyzer.self.builtins.BaseNum;

                if (opname.equals("<") || opname.equals("<=")) {
                    if (leftType.isNumType() && rightType.isNumType()) {
                        NumType newUpper = rightType.asNumType();
                        trueType = new NumType(leftType.asNumType());
                        trueType.setUpper(newUpper.getUpper());
                        falseType = new NumType(leftType.asNumType());
                        falseType.setLower(newUpper.getUpper());
                    } else {
                        Analyzer.self.putProblem(test, "comparing non-numbers: " + leftType + " and " + rightType);
                    }
                } else if (opname.equals(">") || opname.equals(">=")) {
                    if (leftType.isNumType() && rightType.isNumType()) {
                        NumType newLower = rightType.asNumType();
                        trueType = new NumType(leftType.asNumType());
                        trueType.setLower(newLower.getLower());
                        falseType = new NumType(leftType.asNumType());
                        falseType.setUpper(newLower.getLower());
                    } else {
                        Analyzer.self.putProblem(test, "comparing non-numbers: " + leftType + " and " + rightType);
                    }
                } else {
                    trueType = leftType.asNumType();
                }

                Binding b = s1.lookup(leftName.id).get(0);
                s1.update(leftName.id, new Binding(leftName.id, b.getNode(), trueType, Binding.Kind.SCOPE));
                s2.update(leftName.id, new Binding(leftName.id, b.getNode(), falseType, Binding.Kind.SCOPE));
            }
        }
    } 
                            #location 46 
                            #vulnerability type NULL_DEREFERENCE