> There are genuine use cases where returning both a value and an error makes complete sense. I don't feel anyone is saying that the addition of sum types woul

> There are genuine use cases where returning both a value and an error makes complete sense. I don't feel anyone is saying that the addition of sum types would have to replace the existing (Result, error) pattern. Its just a tool in the toolbox. In fact, I think having both is really interesting from a function signature communication perspective; if a function returns (Result, error) in a post-sum-type world, that hints to me that the Result might still be useful even if an error is returned. > I would absolutely hate to see Go go through the same unholy mess as Python: "old-style" vs "new-style" classes, Anytime someone brings up how horrible the Py2 to Py3 transition was, I will remind them that Python is the most popular programming language in the world. Clearly; the transition wasn't actually bad enough to negatively impact its popularity; yet its the token example of "don't break existing programs, you don't want to be like Python". That take is just counter-intuitively wrong. Its like the SDLC paradigm of "releasing often reduces bugs"; it feels wrong, but its actually right. I'm sure saying "we'll never break existing programs" imparts a nice warm feeling in your heart, "we're mature, unlike those other dumb languages". But there is extremely little evidence that backward-incompatible language changes hurt the adoption of programming languages. Actually; there's substantially more evidence that languages which can't adapt and evolve to change will eventually die. I'm not asserting that will happen to Go; I think they're good about bringing forward enhancements to the language in ways that don't break existing programs (like generics). But I also strongly believe they need to rethink their "we won't break existing programs" rule. I am begging the Go team to break my programs. Its not a big deal. I just can't imagine still writing Go programs in 2050 like we are today; it leaves so much value on the table, and we can do better.