TH quasi-quoting bug - fails on quoting where clause in let decl context

In ghc 6.2 and 6.3 (CVS as of early March) evaluating the following in
ghci gives an "impossible happened" error.

do {d <- runQ $ [| let foo = bar where bar = 3 in foo |];  print d}

The bit that causes the problem is the where in the declaration context
introduced by the let.

ghci-6.2 says:

ghc-6.2: panic! (the `impossible' happened, GHC version 6.2):
        nameModule bar_d1yu

and ghci-6.3 says something similar

ghc-6.3: panic! (the `impossible' happened, GHC version 6.3):
        nameModule bar{v} {- v aFI -}

Duncan