#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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Description changed by igloo:
Old description:
> Compiling the attached file in GHC 6.12.1 gives the following error, when
> GHC 6.10.1 compiles it fine:
> [1 of 1] Compiling Main ( baddata.hs, baddata.o )
>
> 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))
New description:
Compiling the attached file in GHC 6.12.1 gives the following error, when
GHC 6.10.1 compiles it fine:
{{{
[1 of 1] Compiling Main ( baddata.hs, baddata.o )
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))
}}}
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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3965#comment:1>
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