DIP33: A standard exception hierarchy

[Walter Bright]

On 4/2/2013 1:00 PM, Lars T. Kyllingstad wrote:
> I definitely don't think we need an IllegalArgumentException. IMO, passing
> illegal arguments is 1) a simple programming error, in which case it should be
> an Error, or 2) something the programmer can not avoid, in which case it
> requires a better description of why things went wrong than just "illegal
> argument".  "File not found", for example.
>
> I didn't really consider contracts when I wrote the DIP, and of course there
> will always be the problem of "should this be a contract or a normal input
> check?"  The problem with contracts, though, is that they go away in release
> mode, which is certainly not safe if that is your error handling mechanism.

A bit of philosophy here:

Contracts are not there to validate user input. They are only there to check for 
logic bugs in the program itself.

It's a very clear distinction, and should not be a problem.

To reiterate, if a contract fails, that is a BUG in the program, and the program 
is then considered to be in an undefined state and is not recoverable.

CONTRACTS ARE NOT AN ERROR HANDLING MECHANISM.