How to fool the divergence checker in ghc 9

Michael Sperber sperber at deinprogramm.de
Fri Jan 20 10:17:49 UTC 2023


On Fri, Jan 20 2023, David Feuer <david.feuer at gmail.com> wrote:

> I don't know what all that means exactly (especially since GHC's demand
> signatures have changed recently in a way I don't understand at all). But
> for hiding divergence, one option is to use a module with demand analysis
> disabled. Try {-# options_ghc -fno-strictness #-}. You'll likely need to
> put oops in its own module to avoid interfering with desired optimizations.

THanks for the suggestion!

So I did this:

{-# options_ghc -fno-strictness #-}
module ConCat.Oops(oops) where

import GHC.Stack (errorWithStackTrace)  -- for oops

-- | Pseudo function to fool GHC's divergence checker.
oops :: String -> b
oops str = errorWithStackTrace ("Oops: "++str)
{-# NOINLINE oops #-}

... but am getting the same result from the divergence checker, sadly ...

-- 
Regards,
Mike


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