I've attached the simplest example of my code that used to compile in
GHC 6.10 now gives the error in GHC 6.12.1:
baddata.hs:33:14:
No instances for (Data Const, Data Var)
arising from the 'deriving' clause of a data type declaration
at baddata.hs:33:14-17
Possible fix:
add an instance declaration for (Data Const, Data Var)
or use a standalone 'deriving instance' declaration instead,
so you can specify the instance context yourself
When deriving the instance for (Data (Domain e g))If I replace: > data Domain e g = Domain > (Expr (Const :+: Var)) > deriving (Data, Typeable) with: > data Domain e g = Domain > (Expr (Const)) > deriving (Data, Typeable) then everything compiles. If nothing else, the error message is misleading. -Ron
baddata.hs
Description: Binary data
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