Crash in TcEnv.lhs line 461

The attached program makes GHC panic:

$ ghc-7.3.20110828 -fforce-recomp Bug.hs
[1 of 1] Compiling Main             ( Bug.hs, Bug.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.3.20110828 for x86_64-unknown-linux):
	ASSERT failed! file compiler/typecheck/TcEnv.lhs line 461
register{v amY} [lid]
forall n{tv amZ} [tv].
main:Main.HDropClass{tc r18} n{tv amZ} [tv] rs{tv amV} [ssk] =>
ghc-prim:GHC.Types.Bool{(w) tc 3c}
-> main:Main.Peano{tc ru} n{tv amZ} [tv]
-> main:Main.WaitOps{tc ro}
     (main:Main.HDrop{tc r17} n{tv amZ} [tv] rs{tv amV} [ssk])
-> ghc-prim:GHC.Types.IO{tc 32I} ghc-prim:GHC.Types.Bool{(w) tc 3c}

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

Trac metadata

Trac field	Value
Version	7.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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