T3330a.hs:17:34:
Occurs check: cannot construct the infinite type:
s = (->) (s ix -> ix)
Expected type: r ix -> Writer [AnyF s1] (r ix)
Actual type: ix2
In the first argument of `hmapM', namely `p'
In the first argument of `execWriter', namely `(hmapM p collect x)'
In the expression: execWriter (hmapM p collect x)
T3330a.hs:17:44:
Couldn't match type `ix2' with `r ix1 -> Writer [AnyF s] (r ix1)'
`ix2' is a rigid type variable bound by
the type signature for `children' at T3330a.hs:16:15
Expected type: PF s1 r (r ix1 -> Writer [AnyF s] (r ix1))
Actual type: PF s1 r ix2
In the third argument of `hmapM', namely `x'
In the first argument of `execWriter', namely `(hmapM p collect x)'
In the expression: execWriter (hmapM p collect x)