> In other words, shouldn't the "rewrite it in Rust" folks have to prove that the cost of their proposed rewrite will be justified?

Agreed, they do. But that it hasn't been proven to make things better doesn't mean it will make things worse. It just means that we don't know enough to say. The right way to answer the "would this software have fewer bugs if it were rewritten in Rust?" question requires a detailed look at what bugs the software has empirically encountered.

A rewrite automatically makes things worse because you start with no code.

I figure it's one of the signs of programmer maturity, that you start to look askance at rewrites. So tempting, yet so rarely even finished let alone better.

In the case of Rust I don't believe this is 100% true given C ABI compatibility. You could start rewriting in such a way that it is integrated with the existing code and slowly, but surely tease the C out of the system.

It would for the longest time be a C program with a metastasizing wart of Rust hung off the side, impossible to get into, impossible to work with, debugging hell, compilation hell. The distros would weep.

Programs written in multiple languages are not exactly a new thing. Every iOS and Mac app is one, just to name one example.

And Firefox has a good chance to become exactly what you describe with the weird cancer analogy--in fact, the nightly builds already are.

Sure, the primary burden of proof is on those proposing a change. However, any time you stand up and make an argument, the burden is on you to make sure it actually makes sense, and that goes for both sides.

This is getting a bit meta, but I disagree. It would be trivial to abuse in discussions.

    A: Bash would be way better for SQLite, really!
    B: But Bash is a terrible choice because X, Y, Z, ...
    A: If you make those arguments, you have to prove them.

"Bash would be terrible because using it would cause a fire"

Yes, arguments have a burden to make sense, and provide evidence...

I'm not sure I take your point. If X, Y, and Z are cogent enough to be worth a rational response, B has done their job under my principle above. A is precisely the one I would want to yell at for using specious arguments.

Anything that is stated without proof can be refuted without proof. Why you think your opinion should be regarded at a higher standard than anybody else's?

...I don't. That's sort of my point. Both sides of a debate have the same responsibility to be reasonable, whatever that level of responsibility may be, whether it's a formal debate or just tossing ideas around.

I like to swing it the other way, you have to prove me that the newly proposed solution is not worth it. You can check out Amazon's policy about driving change. The "will not work" camp has to do the work to prove that something is not going to work. I think this approach yields to better results in practice.