#2775: Type Family panic
-----------------------+----------------------------------------------------
Reporter: camio | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.10.1 | Severity: blocker
Keywords: | Testcase:
Architecture: x86 | Os: Windows
-----------------------+----------------------------------------------------
The following code produces the ghc panic below.
{{{
{-# LANGUAGE RankNTypes, TypeFamilies #-}
import Data.VectorSpace
data I = I { integral :: (VectorSpace v, Scalar v ~ Double) => v
}
-- This works
-- integral :: (VectorSpace v, Scalar v ~ Double) => v
-- integral = undefined
-- type BallAnim = Input -> Behavior Ball
followMouse i = integral undefined undefined
}}}
{{{
ff>ghci GhcBug.hs
GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main ( GhcBug.hs, interpreted )
: panic! (the 'impossible' happened)
(GHC version 6.10.1 for i386-unknown-mingw32):
applyTypeToArgs
ipv{v B4} [lid]
@ (a{tv arL} [sk] -> t_arM{tv} [sk])
$dVectorSpace{v arP} [lid]
(base:GHC.Err.undefined{v rdH} [gid] @ a{tv arL} [sk])
(vector-space-0.5:Data.VectorSpace.Scalar{tc rgl}
(a{tv arL} [sk] -> t_arM{tv} [sk])
~
ghc-prim:GHC.Types.Double{(w) tc 3u}) =>
a{tv arL} [sk] -> t_arM{tv} [sk]
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2775>
GHC <http://www.haskell.org/ghc/>
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