Poor indication of type error location
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