On 8 August 2015 at 14:03, Brandon Allbery
This is quite important, folks. Don't tell us how tools will mitigate this. Go look at Python 3's adoption rate --- and it does have the tools --- and tell me again how well that path works for an established language. (Hint: every Python package I use has no intention of moving to Python 3.)
That seems like a red herring to me. Python does not have a type system to speak of so even simple refactoring is painful. Let alone making changes to the language itself...
Haskell may be new to you personally. That does not mean that it's okay to break what, more than 15 years worth of code?
So when is it okay? :-) Still, if proper tooling automates it, why not? (I'm not advocating making language changes willy-nilly but the argument "it breaks existing code" [in and of itself] implies we are stuck with all mistakes made in the past. Language designers are human too. We need a way forward.)