|Think about Loose Coupling|
Doing this by hand would be a complete PITA
No. Doing this would be
In addition, you now have a maintenance nightmare. Let's say that I'm your maintenance programmer. I go in and realize I need to now modify Foo somewhere. I have 24 hours to get this bug fixed. I don't know about your assertions thing. All I know is that I can fix the bug by hacking at your pretty object. Boom! Your entire assertions framework fails.
Using Hook::LexWrap (and similar techniques) is vastly preferable to adding assertions by hand, for just these reasons.
* Error rates gleaned from Code Complete on p. 610. Steve McConnell says that delivered code generally has 15-50 defects per 1000 lines. He also says that the Apps Division at MS has 10-20/1000 during in-house testing and 0.5/1000 in released code. That's a 30-1 ratio between development and release for a stringent regime. A lax regime will probably have a 10-1 ratio. Thus, a standard programmer during development will probably have 350-500 defects per 1000 lines of code. A really good one will be at 50/1000, or 1/20 lines of code.
Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.
Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.