odd panic with [()] >>> ()

While messing around with arrows in GHCi, I was surprised to see the following (ill-typed) code cause a panic:

   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Prelude> :m Control.Arrow
Prelude Control.Arrow> [1, 2] >>> pure (+1)
ghc-6.6: panic! (the 'impossible' happened)
  (GHC version 6.6 for i386-unknown-linux):
        nameModule it{v aIS}

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

Further experimentation revealed that

[] >>> ()

is a type-error as expected, whereas

[()] >>> ()

causes a panic.

Trac metadata

Trac field	Value
Version	6.6
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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