#3965: 'deriving Data' compilation regression 6.10.1 -> 6.12.1
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Reporter: ronwalf | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.12.1
Keywords: | Difficulty:
Os: MacOS X | Testcase:
Architecture: x86 | Failure: GHC rejects valid program
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Comment(by ronwalf):
baddata2.hs gives a different, possibly more informative error:
{{{
baddata2.hs:34:0:
No instances for (Data Const, Data Var)
arising from a use of `k' at baddata2.hs:34:0-28
Possible fix:
add an instance declaration for (Data Const, Data Var)
In the expression: k (z Domain)
In the definition of `gunfold': gunfold k z _ = k (z Domain)
When typechecking a standalone-derived method for `Data Domain':
gunfold k z _ = k (z Domain)
In the instance declaration for `Data Domain'
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3965#comment:2>
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