gistfile1.hs

module Main(main) where

foo :: [()] -> ()
foo x = bar x where
    bar x = {-# SCC "my" #-} head x

main = print $ foo []

{-
*** Exception (reporting due to +RTS -xc): (THUNK_2_0), stack trace: 
  GHC.List.CAF
  --> evaluated by: Main.my,
  called from Main.foo.bar,
  called from Main.foo,
  called from Main.main,
  called from Main.CAF
  --> evaluated by: Main.main,
  called from Main.CAF
Main: Prelude.head: empty list
-}