T8987.hs:1:1: error:
    Exception when trying to run compile-time code:
      Prelude.undefined
CallStack (from HasCallStack):
  error, called at libraries/base/GHC/Err.hs:79:14 in base:GHC.Err
  undefined, called at T8987.hs:6:23 in main:T8987
    Code: (reportWarning ['1', undefined] >> return [])