It's not yet ready for production, so there are some bugs and cases where we should reject a program but don't do that yet. Having said that, it's quite safe,

It's not yet ready for production, so there are some bugs and cases where we should reject a program but don't do that yet. Having said that, it's quite safe, but won't be undetectable. Code using eval could detect injected identifiers, we don't currently aim at preserving function names, and the method bodies you get with toString() are altered. That should be roughly it.