Access to old variable via Template Haskell blows up ghci
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>