When I compile the attached file on Linux with 4.08.1:
/home/ger/ghc-4.08.1-binary/bin/ghc -c Instances.hs -fglasgow-exts
-fallow-overlapping-instances -fallow-undecidable-instances
I get the message:
Instances.hs:1:
Duplicate or overlapping instance declarations
for `HasConfig (arcTypeConfig value) (arcTypeParms value)'
defined at Instances.hs:19 and defined at Instances.hs:11
This is not fair, because while the instances for HasConfig have the
potential to conflict in the future, they will only do so should the classes
NodeTypeConfigParms and ArcTypeConfigParms overlap.
Instances.hs
