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Using {-# OPTIONS_GHC -XArrows -fno-monomorphism-restriction #-}, and Yampa Starting from line 32, my program contains:

fireworkSF :: Point2 GL.GLdouble -> Point2 GL.GLdouble -> Object
fireworkSF p0 pFinal = proc _ -> do
  rec
    position <- (p0 .+^) ^<< integral -< v0
    let shouldExplode = position == pFinal
    let killReq = if shouldExplode then Event () else noEvent
    let spawnReq = if shouldExplode
                     then Event (Explode pFinal)
                     else noEvent
  returnA -< ObjectOutput {oState = FireworkState position
                          ,oKillReq = killReq
                          ,oSpawnReq = spawnReq}
  where
    v0 = (pFinal ^-^ p0) ^/ 2

The type error reports:

Firework.hs:32:0:
    Couldn't match expected type `Point2 GL.GLdouble'
           against inferred type `Vector2 GL.GLdouble'
    When using functional dependencies to combine
      AffineSpace (Point2 a) (Vector2 a) a,
        arising from the instance declaration at <no location info>
      AffineSpace (Point2 GL.GLdouble) (Point2 GL.GLdouble) a,
        arising from a use of `.+^' at Firework.hs:34:16-23
    When generalising the type(s) for `fireworkSF'

Indicating that the bug is something to do with line 34. The actual bug is that the last line of the paste should read:

    v0 = (pFinal .-. p0) ^/ 2