> If your codebase is not usable anymore because your language evolved. That's a failure. Only if it claimed to be eternally BW compatible. Some languages neve

> If your codebase is not usable anymore because your language evolved. That's a failure. Only if it claimed to be eternally BW compatible. Some languages never made that claim. To me a language is a dependency like any API, just with a much bigger surface touching my code. I'd say it's the hardest API to replace in any code. "BW compatibility" is just as much a feature as "breaking BW compatibility", I just like languages (or any API really) to be upfront about it's policy toward BW compatibility. And I've observed a lot of langs change their attitude towards it over time. Especially considering pre-1.0 times, I find a lot of langs happily break BW compatibility in their early days.