panic when using function in 'deriving' data declaration

[shapeshifter]

Hello. I haven't found any matching bugs for this. To reproduce:

1) Start up ghci

2) Enter something like the following, which contains a typo 'show' instead of 'Show'.

data Test = Yes | No deriving (show, Eq)

3) ghci will panic saying:

Prelude> data Test = Yes | No deriving (show, Eq)
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.2 for i386-unknown-linux):
	nameModule show{tv aa0}

Notes:

• The 'show' can be substituted with any other function name
• It also happens on x86_64.
• It also happens when putting such a line into a .hs file and trying to compile it

[guest]

It is already fixed in HEAD, bug #5961.