#1948: panic compiling associated type synonims
----------------------+-----------------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.1
Severity: normal | Keywords: typefunction panic
Testcase: | Architecture: Unknown
Os: Unknown |
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Trying to compile this:
{{{
{-# OPTIONS -fglasgow-exts #-}
data Cons a b
data Nil
data Foo a = Foo
class (Appendt l0 l1 ~ l2) => Append l0 l1 l2 where
type Appendt l0 l1 :: *
append :: Foo l0 -> Foo l1 -> Foo l2
instance (Appendt b l1 ~ l2) => Append (Cons a b) l1 (Cons c l2) where
type Appendt (Cons a b) l1 = Cons a (Appendt b l1)
}}}
gives this error:
{{{
ghc-6.8.1: panic! (the 'impossible' happened)
(GHC version 6.8.1 for i386-unknown-linux):
Coercion.splitCoercionKindOf
base:GHC.Prim.trans{(w) tc 34y}
(base:GHC.Prim.sym{(w) tc 34v}
((main:Main.:CoF:R1Appendt{tc roB})
a{tv aph} [sk] b{tv ape} [sk] l1{tv apf} [sk]))
t_apM{tv} [tau]
<pred>(main:Main.:R1Appendt{tc ros})
a{tv aph} [sk] b{tv ape} [sk] l1{tv apf} [sk]
~
t_apM{tv} [tau]
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
i've tried to reduce the code to the minimum that will trigger the panic.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1948>
GHC <http://www.haskell.org/ghc/>
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