It's common sense what I said. It applies across the industry regardless of the programming languages used. On the contrary, where's the evidence suggesting that the Rust is what made Gecko rewrite succeed? Has there been any rewrite from scratch with some other programming language?
There were two previous attempts at parallelizing CSS layout in Firefox. Both were in C++. Both were abandoned after being unsuccessful. The Servo folks credited Rust's safety guarantees as the reason why they were able to be successful on the third attempt.
I mean, the Rust version was also put into the existing codebase, so it's not clear to me what distinction you're making.
But this presentation was made seven years ago, and the attempts it's talking about are even older, and I wasn't involved with them. So I don't know the answer to your question.
The distinction is whether or not you're rewriting something from scratch carrying no baggage from the thwarts of the existing system or you keep organically growing existing code to meet the new requirements. The latter is usually much much harder. I hope it's clear now.
No, I don't think there's any concrete evidence either way. I'm not trying to argue that it was Rust that made it succeed - I'm sure in reality it was some mixture of both, as well as other factors.
Having to work and learn through the codebase to make some substantial improvements often requires substantial effort and even rewiring the code architecture itself. That's enough of the evidence for me.
