urk! lookup local fingerprint with -O and TemplateHaskell

[ganesh]

An interesting feature of this bug is that it goes away when TemplateHaskell is removed (it's cut down from a much larger test case which actually used that)

-O is also necessary.

ghc -c -O Foo.hs

ghc: panic! (the 'impossible' happened)

(GHC version 6.10.0.20081007 for i386-unknown-mingw32):

urk! lookup local fingerprint main:Foo.:CoActionT{tc rj4}

[ganesh]

Improved version of test case

[simonmar]

Duplicate of #2685, which should be fixed in recent snapshots. Thanks for the report!