<div dir="ltr"><div>"Only exceptionally would we fix a design flaw in a way that breaks programs compiled with existing language editions." <a href="https://github.com/ghc-proposals/ghc-proposals/blob/wip/general-rules/principles.rst#34exceptions-gr2">https://github.com/ghc-proposals/ghc-proposals/blob/wip/general-rules/principles.rst#34exceptions-gr2</a></div><div><br></div><div>This is not exceptional is it? It's just a regular design flaw :) If we must fix it, let's do it in a way that complies with the stability principle.<br></div><div><br></div><div>Cheers</div><div>Simon<br></div><div></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, 29 Jan 2024 at 11:15, Joachim Breitner <<a href="mailto:mail@joachim-breitner.de">mail@joachim-breitner.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
Am Montag, dem 29.01.2024 um 11:03 +0000 schrieb Simon Marlow:<br>
> I might be a bit confused, but doesn't this proposal change the meaning of an existing<br>
> extension (PatternSignatures)?<br>
<br>
a long-ago deprecated one:<br>
<br>
~ $ ghci<br>
GHCi, version 9.4.8: <a href="https://www.haskell.org/ghc/" rel="noreferrer" target="_blank">https://www.haskell.org/ghc/</a>  :? for help<br>
ghci> :set -XPatternSignatures<br>
<br>
<no location info>: warning: [-Wdeprecated-flags]<br>
    -XPatternSignatures is deprecated: use -XScopedTypeVariables or pragma {-# LANGUAGE ScopedTypeVariables #-} instead<br>
<br>
Hopefully our stability principles does not require us to heed programs<br>
that ignored deprecation flags for a while?<br>
<br>
My understanding of<br>
<a href="https://github.com/ghc-proposals/ghc-proposals/blob/wip/general-rules/principles.rst#3ghc-stability-principles" rel="noreferrer" target="_blank">https://github.com/ghc-proposals/ghc-proposals/blob/wip/general-rules/principles.rst#3ghc-stability-principles</a><br>
is that, despite “stable package” not saying “does not use features<br>
deprecated long ago”, it’s still ok to break such programs, as this is<br>
our mechanism GR3?<br>
<br>
<br>
Of course we could side-step this procedural question about repurposing<br>
an old extension and introduce `SimplePatternSignatures` instead. Not<br>
in favor, simply because as a user I more than once intuitively reached<br>
for `PatternSignatures` to get the proposed behavior.<br>
<br>
Cheers,<br>
Joachim<br>
<br>
<br>
-- <br>
Joachim Breitner<br>
  <a href="mailto:mail@joachim-breitner.de" target="_blank">mail@joachim-breitner.de</a><br>
  <a href="http://www.joachim-breitner.de/" rel="noreferrer" target="_blank">http://www.joachim-breitner.de/</a><br>
<br>
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</blockquote></div>