Simpler(-ish) GHC bug reproducer

repro.hs

module Main where

import Control.Monad
import Data.AffineSpace
import Data.Thyme.Clock
import Data.Thyme.Time

filterTimes
  :: [UTCTime]
  -> UTCTime
  -> NominalDiffTime
  -> [UTCTime]
filterTimes ts u d =
  let x t = abs (t .-. u) - realToFrac d < 0
  in mfilter x ts

main :: IO ()
main = do
  let t = mkUTCTime (fromGregorian 2017 03 29) 21700
      entries = [t]
      aBitLater = mkUTCTime (fromGregorian 2017 03 29) 21750
      diff = 150
  print $ filterTimes entries aBitLater diff

runrepro.sh

#!/usr/bin/env bash

function echoAndRun {
  echo "$1"
  $1
}

echoAndRun "rm *.o *.hi"
echoAndRun "ghc -Wall --make -O0 repro.hs"
echoAndRun "./repro"
echoAndRun "rm *.o *.hi"
echoAndRun "ghc -Wall --make -O repro.hs"
echoAndRun "./repro"