[Haskell-cafe] Safe Haskell?

[Richard Eisenberg]

Hi café,

Do you use Safe Haskell? Do you know someone who does? If you do, which of Safe Haskell's guarantees do you rely on?

Here, a user of Safe Haskell is someone who relies on any guarantees that Safe Haskell provides, not someone who makes sure to have the right pragmas, etc., in your library so that users can import it Safely.

Context: Safe Haskell is not lightweight to support within GHC and the ecosystem. Despite being a formidable research project with a (in my opinion) quite worthwhile goal, it's unclear which of Safe Haskell's purported guarantees are actually guaranteed by GHC. (The lack of unsafeCoerce is not actually guaranteed: https://gitlab.haskell.org/ghc/ghc/-/issues/9562 <https://gitlab.haskell.org/ghc/ghc/-/issues/9562>.) Recent design questions about what should be Safe and what shouldn't be (somehow cannot find the discussion after a few minutes of searching; perhaps fill this in) have been answered only by stabs in the dark. The status quo is causing pain: https://gitlab.haskell.org/ghc/ghc/-/issues/19590 <https://gitlab.haskell.org/ghc/ghc/-/issues/19590>. There are hundreds (maybe thousands) of lines of delicate logic within GHC to support Safe Haskell. These parts of GHC have to be read, understood, and maintained by people with limited time.

I thus wonder about deprecating and eventually removing Safe Haskell. I don't have a concrete plan for how to do this yet, but I'm confident we could come up with a migration strategy.

The set of people who would win by removing Safe Haskell is easy enough to discover. But this email is intended to discover who would be harmed by doing so. If you know, speak up. Otherwise, I expect I will write up a GHC proposal to remove the feature.

Thanks,
Richard
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