id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5668	panic: updInertSet	simonmar	dimitris	"Building `parsec-3.1.2` with HEAD panics with a complaint about `updInertSet`.

{{{
Building parsec-3.1.2...
[ 1 of 25] Compiling Text.Parsec.Pos  ( Text/Parsec/Pos.hs, dist/build/Text/Parsec/Pos.o )
[ 2 of 25] Compiling Text.Parsec.Error ( Text/Parsec/Error.hs, dist/build/Text/Parsec/Error.o )
[ 3 of 25] Compiling Text.ParserCombinators.Parsec.Error ( Text/ParserCombinators/Parsec/Error.hs, dist/build/Text/ParserCombinators/Parsec/Error.o )
[ 4 of 25] Compiling Text.ParserCombinators.Parsec.Pos ( Text/ParserCombinators/Parsec/Pos.hs, dist/build/Text/ParserCombinators/Parsec/Pos.o )
[ 5 of 25] Compiling Text.Parsec.Prim ( Text/Parsec/Prim.hs, dist/build/Text/Parsec/Prim.o )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.3.20111129 for x86_64-unknown-linux):
        updInertSet
    Multiple inert equalities:
    Old (already inert): ([W]{0} ( cobox{v a5FZ} [lid] :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                               -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                          ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) ) :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                                                                               -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                                                                                                                          ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                                                                                                                -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) (CTyEqCan),
                          ( cobox{v a5FZ} [lid] :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                        -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                   ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                         -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) ))
    Trying to insert   : ([W]{0} ( cobox{v a5FZ} [lid] :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                               -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                          ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) ) :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                                                                               -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                                                                                                                          ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                                                                                                                                -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) (CTyEqCan),
                          ( cobox{v a5FZ} [lid] :: ( m_ta4{tv} [tau] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                        -> ghc-prim:GHC.Prim.*{(w) tc 34d} )
                                                   ghc-prim:GHC.Types.~{(w) tc 31Q} ( m{tv a5Fj} [sk] :: ghc-prim:GHC.Prim.*{(w) tc 34d}
                                                                                                         -> ghc-prim:GHC.Prim.*{(w) tc 34d} ) ))

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
}}}


To repeat:

{{{
$ cabal install --with-ghc=$ghcval parsec
}}}

where `$ghcval` is your GHC.  In this case it was a GHC I had just built with `validate`, I wanted to install `parsec` so I could test something else.
"	bug	closed	highest	7.4.1	Compiler	7.2.1	fixed		dimitris@…	Unknown/Multiple	Unknown/Multiple	Compile-time crash	Unknown