[Haskell-cafe] an idea for modifiyng data/newtype syntax: use `::=` instead of `=`

[Hilco Wijbenga]

On 8 August 2015 at 14:03, Brandon Allbery <allbery.b at gmail.com> wrote:
> 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.)