Access to old variable via Template Haskell blows up ghci

[guest]

When you try to access a replaced variable name via Template Haskell in GHCi, GHCi panics:

  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.4.2, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base-1.0 ... linking ... done.
Prelude> :set -fth
Prelude> :m +Language.Haskell.TH
Prelude Language.Haskell.TH> let f n = n * 2 :: Int
Prelude Language.Haskell.TH> fName <- runQ [| f |]
Loading package haskell98-1.0 ... linking ... done.
Loading package template-haskell-1.0 ... linking ... done.
Prelude Language.Haskell.TH> $(return $ AppE fName (LitE (IntegerL 7)))
14
Prelude Language.Haskell.TH> let f n = n * 3 :: Int
Prelude Language.Haskell.TH> fName2 <- runQ [| f |]
Prelude Language.Haskell.TH> $(return $ AppE fName2 (LitE (IntegerL 7)))
21
Prelude Language.Haskell.TH> $(return $ AppE fName (LitE (IntegerL 7)))
ghc-6.4.2: panic! (the `impossible' happened, GHC version 6.4.2):
	nameModule f{v a1WB}

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

Prelude Language.Haskell.TH> 

[Lyle Kopnicky]

It was me who posted the bug. lyle AT qseep DOTT net

[igloo]

This still happens with the HEAD. I've added :set -fth to the reproduction instructions.

[simonpj]

Good point. Fixed in the HEAD.

Ian: pls push to 6.6.1 branch.

Simon