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<p class="MsoNormal"><span style="font-size:12.0pt">if it is, please can someone add a new regression example to #12088. You can never have too many.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> ghc-devs <ghc-devs-bounces@haskell.org>
<b>On Behalf Of </b>Richard Eisenberg<br>
<b>Sent:</b> 13 April 2018 02:39<br>
<b>To:</b> Iavor Diatchki <iavor.diatchki@gmail.com><br>
<b>Cc:</b> ghc-devs@haskell.org<br>
<b>Subject:</b> Re: Question about TypeInType<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I think this is #12088. The problem is that open type family instances aren't used in kind checking in the same region of a module. The workaround is to put a top-level Template Haskell splice<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">> $(return [])<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">between the two type instances. This is far from optimal, but fixing it is a Major Project. See <a href="https://ghc.haskell.org/trac/ghc/ticket/12088#comment:15">https://ghc.haskell.org/trac/ghc/ticket/12088#comment:15</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Richard<o:p></o:p></p>
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<p class="MsoNormal">On Apr 12, 2018, at 7:47 PM, Iavor Diatchki <<a href="mailto:iavor.diatchki@gmail.com">iavor.diatchki@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I was experimenting with TypeInType and run into a problem, that can be reduced to the following example. Does anyone have any insight on what causes the error, in particular why is `IxKind` not being reduced?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-Iavor<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">{-# Language TypeInType, TypeFamilies #-}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">module Help where<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">import Data.Kind<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">type family IxKind (m :: Type) :: Type<o:p></o:p></p>
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<p class="MsoNormal">type family Value (m :: Type) :: IxKind m -> Type<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">data T (k :: Type) (f :: k -> Type)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">type instance IxKind (T k f) = k<o:p></o:p></p>
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<p class="MsoNormal">type instance Value (T k f) = f<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">{-<o:p></o:p></p>
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<p class="MsoNormal">[1 of 1] Compiling Help ( Desktop/Help.hs, interpreted )<o:p></o:p></p>
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<p class="MsoNormal">Desktop/Help.hs:13:31: error:<o:p></o:p></p>
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<p class="MsoNormal"> • Expected kind ‘IxKind (T k f) -> *’, but ‘f’ has kind ‘k -> *’<o:p></o:p></p>
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<p class="MsoNormal"> • In the type ‘f’<o:p></o:p></p>
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<p class="MsoNormal"> In the type instance declaration for ‘Value’<o:p></o:p></p>
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<p class="MsoNormal"> |<o:p></o:p></p>
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<p class="MsoNormal">13 | type instance Value (T k f) = f<o:p></o:p></p>
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<p class="MsoNormal"> | ^<o:p></o:p></p>
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<p class="MsoNormal">Failed, no modules loaded.<o:p></o:p></p>
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<p class="MsoNormal">-}<o:p></o:p></p>
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<p class="MsoNormal">_______________________________________________<br>
ghc-devs mailing list<br>
<a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a><br>
<a href="http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs">http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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