[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
Tue Apr 9 11:57:48 UTC 2024
Hi Tom,
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
but that looks ugly, and it feels strange.
Thanks for replying
Op di 9 apr 2024 om 12:38 schreef Tom Ellis <
tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk>:
> Hello Han,
>
> 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
>
> Tom
>
>
>
> 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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