#5768: GHC Panic compiling type family with -XPolyKinds
--------------------------------+-------------------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.1-rc1 | Keywords: PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Compile-time crash | Testcase:
Blockedby: | Blocking:
Related: |
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I received the following error message:
{{{
ghc: panic! (the 'impossible' happened)
(GHC version 7.4.0.20111219 for x86_64-unknown-linux):
tyConKind ghc-prim:GHC.Prim.BOX{(w) tc 347}
}}}
I was compiling the following code:
{{{
{-# LANGUAGE TypeFamilies,
PolyKinds,
ScopedTypeVariables
#-}
convert :: a -> b
convert = undefined
type family Foo a
bar :: forall a b. b -> (Foo a)
bar f = (convert f :: (Foo a))
}}}
Interestingly, the output is different when changing the order in the
forall (forall b a produces a different error). The same result happened
on Linux/x86_64 and MacOS 10.7.2/x86_64-apple-darwin,
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5768>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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