[ghc-steering-committee] #571: -Wsevere, Shepherd: Adam (rec: accept)

[Adam Gundry]

On 18/09/2023 20:28, Richard Eisenberg wrote:
>
> Bottom line for me: I think we should implement and then experiment. 
> Given the potentially delicate nature of this, I might even advocate for 
> implementing this in a release branch, so that as much of Hackage as 
> possible actually has a hope of compiling. Then test to see where the 
> breakage occurs. If were happy with the result, rebase the 
> implementation on master. But I don't want us to get into a state where 
> we accept, implement, observe moderate breakage, and then blast ahead 
> because the committee approved the idea.

The breakage concern is worth thinking about, I agree, but fortunately 
in this instance we don't need to wait for an implementation to run an 
experiment. The change can be relatively effectively simulated by 
compiling with -Werror=missing-methods -Werror=missing-fields, and 
indeed Oleg has done so already for clc-stackage as he reports here:

https://github.com/ghc-proposals/ghc-proposals/issues/544#issue-1410125536

https://github.com/ghc-proposals/ghc-proposals/issues/544#issuecomment-1279948737

Out of nearly 3000 packages, he found 22 were broken by 
-Werror=missing-methods and 9 by -Werror=missing-fields.

Adam


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Adam Gundry, Haskell Consultant
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