#5287: The 'impossible' happened. solveDerivEqns: probable loop
--------------------------+-------------------------------------------------
Reporter: agocorona | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.0.3 | Keywords: solveDerivEqns
Testcase: | Blockedby:
Os: Windows | Blocking:
Architecture: x86 | Failure: Compile-time crash
--------------------------+-------------------------------------------------
This code:
--------- begin of code------
{-# LANGUAGE FlexibleInstances, UndecidableInstances
, MultiParamTypeClasses
#-}
class Serializable a b
class IResource a --The rest of the instance definitions does not
matter for the error
instance Serializable a b => IResource a
data DBRef a= DBRef String a
instance (IResource a) => Read (DBRef a)
data Votation a= Votation{
content :: DBRef a
} deriving (Read)
------------------------------- end of code ---
gives the following error at compilation time:
tests>runghc impossiblelloop.hs
ghc: panic! (the 'impossible' happened)
(GHC version 7.0.3 for i386-unknown-mingw32):
solveDerivEqns: probable loop
(impossiblelloop.hs:20:13-16 main:Main.$fReadVotation{v rhI} [a{tv
abB} [tv]
] base:GHC.Read.Read{tc 2d} [main:Main.Votation{tc rbo}
a{tv abB} [tv]] = [base:GHC.Read.Read{tc
2d}
(main:Main.DBRef{tc
rbu}
a{tv abB} [tv])])
[[main:Main.Serializable{tc rbA} a{tv abB} [tv] b{tv ajE} [tcs]]]
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5287>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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