Joachim,
My understand if the cost and drawbacks section[1], is that existing code
breaks even without explicitly enabling the extension. If this is indeed
not the case it should be called our explicitly in the section that
breakage requires the extension to be enabled. Also an explanation why the
patsyn test cases fail. Do we automatically enable that extension in the
testsuite? Where does the regression come from?
Maybe I’m misreading that section and it just needs to be clarified that
there is _no breakage without **explixitly** enabling the extension_ to
existing code.
Cheers,
Moritz
[1]:
https://github.com/ghc-proposals/ghc-proposals/blob/eb4b67c29282520b2c5c6a49...
On Sun, 10 Sep 2023 at 12:04 PM, Joachim Breitner
Hi,
since this is guarded by an extension that doesn't even exist yet, no code is broken, is there?
I also don't expect this to be enabled in the future without coinciding with an intentional action by the developers - enabling this extension or switching to a future language edition that has this enabled by default (should that ever exist). Is it not sufficient if they are _then_ bothered with this change?
(That said, we could say that a unparenthized type annotation on a pattern synonym is simply confusing, and thus use a warning to nudge the developers to add the parentheses now.)
So not opposed to an early warning, I just don't think it's strictly necessary for this change.
Cheers, Joachim
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