Enable maxBound checks for OverloadedLists (Fixes #18172)

Consider the Literal [256] :: [Data.Word.Word8]

When the OverloadedLists extension is not active, then the ol_ext field in the OverLitTc record that is passed to the function getIntegralLit contains the type Word8. This is a simple type, and we can use its type constructor immediately for the warnAboutOverflowedLiterals function.

When the OverloadedLists extension is active, then the ol_ext field contains the type family Item [Word8]. The function nomaliseType is used to convert it to the needed type Word8.

Thanks offering this MR. But what ticket is it solving (ticket = problem, MR = solution)? Is there a user-visible bug? Or is this a perf enhancement? Or what?

Thanks

@simonpj: Thanks for you comment. In the MR title I wrote (Fixes #18172 (closed)). So following the DRY principle, I didn't repeat it in the text. And yes, this is a user visible bug.

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@RyanGlScott Thanks for your code review. I'll switch this MR to WIP. I'll investigate an other solution path: As with the case for [Maybe Word8] we shouldn't see the Item constructor in the [Word8] case.

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• 0f9818e4 - Enable maxBound checks for OverloadedLists (Fixes #18172 (closed))

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• 7c3c1c49 - Enable maxBound checks for OverloadedLists (Fixes #18172 (closed))

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• 1d437314 - Enable maxBound checks for OverloadedLists (Fixes #18172 (closed))

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