[Haskell-cafe] Debugging a test suite freeze

[David Feuer]

Thank you so much for figuring this out. I've filed a bug at

https://gitlab.haskell.org/ghc/ghc/-/issues/22549

In the mean time, I'll adjust the upper bounds on Hackage and release a version
of logict-sequence that hopefully won't have this issue.

On Thu, Dec 1, 2022 at 7:14 PM Li-yao Xia <lysxia at gmail.com> wrote:
>
> GHC 9.4.3 with -O2 is miscompiling the derived Show and Eq instances for SeqT in logict-sequence.
>
>     main :: IO ()
>     main = print (pure 0 :: Seq Int)
>     -- -O0, -O1: prints the Seq
>     -- -O2: <<loop>>
>
> On top of that, both hedgehog and hspec fail to catch `<<loop>>`.
>
>     main :: IO ()
>     main = defaultMain
>       [ check $ property $ do
>           let x = x :: Int  -- obvious loop compiles to a thrown exception <<loop>>
>           if x == x then pure () else pure ()  ]
>     -- "thread blocked indefinitely in an STM transaction"
>     -- meaning some thread is not getting cleaned up properly
>
>     main :: IO ()
>     main = hspec $ do
>       describe "work" $ do
>         it "works" $ do
>           let x = x :: Int  -- obvious loop compiles to a thrown exception <<loop>>
>           if x == x then pure () else pure () :: IO ()
>     --- hangs
>
> Cheers,
> Li-yao
>
>
> On 2022-11-30 10:33 PM, David Feuer wrote:
>
> The logict-sequence test suite consistently freezes up on the last
> test when compiled with GHC 9.4.3. logict-sequence and its test suite
> don't do anything special with that GHC/base version as far as I can
> see, or anything particularly strange in general, so I'm pretty
> confident the problem lies elsewhere. My best guesses are hedgehog,
> tasty, and tasty-hedgehog. Has anyone else run into weird issues with
> any/all of these on GHC 9.4.3?
>
> David
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