#3850: EmptyDataDecls and type context
---------------------------------+------------------------------------------
Reporter: Paczesiowa | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.12.1 | Keywords: emptydatadecls
Os: Unknown/Multiple | Testcase:
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
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the following code fails to parse correctly or typecheck under 6.12.1
{{{
{-# LANGUAGE EmptyDataDecls #-}
data Show a => Foo a
}}}
error:
{{{
No context is allowed on a GADT-style data declaration
(You can put a context on each contructor, though.)
}}}
it works with 6.10.
this is the reason of HList failure on 6.12.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3850>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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