panic: updInertSet

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.

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	highest
Resolution	Unresolved
Component	Compiler
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