[ghc-steering-committee] Language Extension Policy – Round 2

[Richard Eisenberg]

> On May 1, 2023, at 8:59 AM, Adam Gundry <adam at well-typed.com> wrote:
> 
> 
> * recommended (part of the language, fairly stable);
> 
> * experimental (not yet resolved one way or the other); or
> 
> * discouraged (supported primarily for backwards compatibility).

Yes! And also Simon's addition of "language variation".

My stance is (I claim) it is hard for users to navigate the current extension maze (e.g. it's pretty hard for someone to know that scary-sounding UndecidableInstances is safe to use in practice but that TypeFamilies may break their type inference, even if they never write a type family). We should strive to simplify this maze so that it's easier for our users to write effective Haskell.

One way to phrase this is "stable and liberal".

Richard
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