[Haskell-cafe] Ambiguous occurence error, despite use of DuplicateRecordFields (worked with ghc 8.10.7, not with 9.6.4)
Han Joosten
han.joosten.han at gmail.com
Wed Apr 10 06:43:08 UTC 2024
I figured out to go for the easy way, not to figure out all the (fancy?)
language pragma's. I will just rewrite the broken bits. Not hard to do,
mostly annoying and less concise.
I use stack to build. That way I know exactly the versions that will be
used for each and every dependency.
Thanks for helping out!
Han.
Op di 9 apr 2024 om 15:01 schreef Tom Ellis <
tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk>:
> By the way, how are you compiling this? I tried
>
> $ cabal build -w ghc-9.6
>
> on branch upgrade-ghc but I get a cabal resolver error.
>
> Tom
>
>
> On Tue, Apr 09, 2024 at 01:17:47PM +0100, Tom Ellis wrote:
> > I see, thanks. So it does look like my wild guess was correct. GHC
> > will no longer disambiguate ambiguous field selectors. Perhaps you're
> > supposed to use OverloadedRecordDot for this (I'm not sure, I don't
> > use it myself).
> >
> > On Tue, Apr 09, 2024 at 01:57:48PM +0200, Han Joosten wrote:
> > > The code can be found here:
> > >
> https://github.com/AmpersandTarski/Ampersand/blob/upgrade-ghc/src/Ampersand/Core/ParseTree.hs
> > >
> > > The idea is that I have several data definitions each with a field
> named
> > > `pos`. I have a class that conveniently gets that field from whatever
> > > instance. This used to work, but now is broken:
> > >
> > > data Foo = Foo
> > > { pos :: !Origin,
> > > ... other fields
> > > }
> > > data Bar = Bar
> > > { pos :: !Origin,
> > > ... other fields
> > > }
> > >
> > > class Traced a where
> > > origin :: a -> Origin
> > >
> > > instance Traced Foo where
> > > origin = pos
> > >
> > > instance Traced Bar where
> > > origin = pos
> > >
> > > Of course I could rewrite the instance definitions something like
> > >
> > > instance Traced Foo where
> > > origin (Foo{pos = p} = p
> > >
> > > Op di 9 apr 2024 om 12:38 schreef Tom Ellis <
> > > tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk>:
> > > > Would it be possible to produce a minimal example that demonstrates
> > > > the problem? Or at the very least share the code? It's very hard to
> > > > know where to start diagnosing. (Although perhaps someone else knows
> > > > without having to see code.)
> > > >
> > > > At a wild guess, have you been hit by this?
> > > >
> > > > > As of GHC 9.4.1, selector names have to be entirely unambiguous
> > > > > (under the usual name resolution rules), while for record updates,
> > > > > there must be at most one datatype that has all the field names
> > > > > being updated.
> > > >
> > > >
> https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/duplicate_record_fields.html#extension-DuplicateRecordFields
> > > >
> > > > On Tue, Apr 09, 2024 at 12:18:14PM +0200, Han Joosten wrote:
> > > > > Hi all,
> > > > >
> > > > > I am currently migrating a Haskell project that uses ghc 8.10.7 to
> ghc
> > > > > 9.6.4.
> > > > >
> > > > > Using the new version, I get errors like
> > > > >
> > > > > ~~~.haskell
> > > > > Ambiguous occurrence ‘pos’
> > > > > It could refer to
> > > > > either the field ‘pos’ of record ‘PClassify’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:1265:5
> > > > > or the field ‘pos’ of record ‘PPurpose’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:1186:5
> > > > > or the field ‘pos’ of record ‘P_ViewSegment’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:1129:5
> > > > > or the field ‘pos’ of record ‘P_ViewD’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:1080:5
> > > > > or the field ‘pos’ of record ‘P_IdentDf’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:1024:5
> > > > > or the field ‘pos’ of record ‘P_BoxItem’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:981:9
> > > > > or the field ‘pos’ of record ‘TemplateKeyValue’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:959:5
> > > > > or the field ‘pos’ of record ‘BoxHeader’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:947:5
> > > > > or the field ‘pos’ of record ‘P_SubIfc’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:934:9
> > > > > or the field ‘pos’ of record ‘P_Interface’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:899:5
> > > > > or the field ‘pos’ of record ‘P_Population’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:870:9
> > > > > or the field ‘pos’ of record ‘P_Rule’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:806:5
> > > > > or the field ‘pos’ of record ‘PairViewSegment’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:740:9
> > > > > or the field ‘pos’ of record ‘P_NamedRel’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:591:5
> > > > > or the field ‘pos’ of record ‘PAtomPair’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:467:5
> > > > > or the field ‘pos’ of record ‘Pragma’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:415:5
> > > > > or the field ‘pos’ of record ‘P_Relation’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:408:5
> > > > > or the field ‘pos’ of record ‘Representation’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:339:5
> > > > > or the field ‘pos’ of record ‘PConceptDef’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:268:5
> > > > > or the field ‘pos’ of record ‘P_Pattern’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:209:5
> > > > > or the field ‘pos’ of record ‘Role’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:185:5
> > > > > or the field ‘pos’ of record ‘P_RoleRule’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:172:5
> > > > > or the field ‘pos’ of record ‘P_Enforce’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:152:5
> > > > > or the field ‘pos’ of record ‘MetaData’,
> > > > > defined at
> > > > >
> /workspaces/AmpersandNamespace/src/Ampersand/Core/ParseTree.hs:136:5
> > > > >
> > > > > Previously, it was totally fine to have different data types each
> have a
> > > > > field with the same name, as long as you used
> `DuplicateRecordFields`
> > > > >
> > > > > I have searched the migration documentation but I couldn't find
> any clue
> > > > on
> > > > > why this has been changed or how to deal with it. I probably
> missed it.
> > > > > Any help is mostly appreciated!
> > > > >
> > > > > Thanks for reading
> > > > > Cheers,
> > > > > Han Joosten
> > > >
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