[Haskell-cafe] Ambiguous occurence error, despite use of DuplicateRecordFields (worked with ghc 8.10.7, not with 9.6.4)
Tom Ellis
tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk
Wed Apr 10 06:52:49 UTC 2024
Perhaps this trick may help you?
https://discourse.haskell.org/t/how-to-do-user-facing-records-in-2024/9176/23
On Wed, Apr 10, 2024 at 08:43:08AM +0200, Han Joosten wrote:
> 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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