happy-2.0.2 regresses language-python-0.5.8

[bgamari]

dist/build/Language/Python/Version2/Parser/Parser.hs:7426:4: error: [GHC-83865]
    • Couldn't match type ‘Happy_GHC_Exts.Int32#’
                     with ‘Happy_GHC_Exts.Int#’
      Expected: Happy_Int
        Actual: Happy_GHC_Exts.Int32#
    • In the expression: Happy_GHC_Exts.indexInt32OffAddr# arr off
      In an equation for ‘happyIndexOffAddr’:
          happyIndexOffAddr (HappyA# arr) off
            = (Happy_GHC_Exts.indexInt32OffAddr# arr off)
     |
7426 |   (Happy_GHC_Exts.indexInt32OffAddr# arr off)
     |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Using GHC 9.6.5.

[Ericson2314]

Huh that looks like an older bug that happened when the GHC unboxed number one was changing. I didn't think anything happened relative this since the last 1.x release.

[bgamari]

I can confirm that the same project builds with happy-1.20.1.1.

[Ericson2314]

@bgamari Can you diff the generated parsers?

[bgamari]

@Ericson2314 see https://gist.github.com/bgamari/87c10deca02c86460f0935f511cae768.

[sgraf812]

Very strange. It must be this line from the template:

happy/lib/data/HappyTemplate.hs

Line 127 in 1f92300

(Happy_GHC_Exts.indexInt32OffAddr# arr off)

But we test this code path quite extensively on GHC 9.6 and lower. Is there anything special about the architecture? 32 bit?

(The diff appears to be incomplete, btw. Not that it matters.)

[Bodigrim]

That's because of https://github.com/bjpop/language-python/blob/8e0a43ddfd1b9e22d104ece01333706d0fe71e04/language-python/src/Language/Python/Version2/Parser/Parser.y#L4-L5

#undef __GLASGOW_HASKELL__
#define __GLASGOW_HASKELL__ 709

[Bodigrim]

I've seen this ugly hack used in the wild more than once to work around #109. For this particular instance see discussion at bjpop/language-python#41.

Instead of #if __GLASGOW_HASKELL__ >= 901 we can check #if MIN_VERSION_base(4,15,0), which is equivalent, but immune to #undef __GLASGOW_HASKELL__.

[bgamari]

Oof, that is awful. Good catch, @Bodigrim .

[Ericson2314]

OK whew, I am glad this wasn't a crazy bug in happy itself :)