T14172.hs:7:46: error: • Found type wildcard ‘_’ standing for ‘a'’ Where: ‘a'’ is a rigid type variable bound by the inferred type of traverseCompose :: (a -> f b) -> g a -> f (h a') at T14172.hs:8:1-46 To use the inferred type, enable PartialTypeSignatures • In the first argument of ‘h’, namely ‘_’ In the first argument of ‘f’, namely ‘(h _)’ In the type ‘(a -> f b) -> g a -> f (h _)’ T14172.hs:8:19: error: • Couldn't match type ‘a’ with ‘g'1 a'0’ Expected: (f'0 a -> f (f'0 b)) -> g a -> f (h a') Actual: (Unwrapped (Compose f'0 g'1 a'0) -> f (Unwrapped (h a'))) -> Compose f'0 g'1 a'0 -> f (h a') ‘a’ is a rigid type variable bound by the inferred type of traverseCompose :: (a -> f b) -> g a -> f (h a') at T14172.hs:7:1-47 • In the first argument of ‘(.)’, namely ‘_Wrapping Compose’ In the expression: _Wrapping Compose . traverse In an equation for ‘traverseCompose’: traverseCompose = _Wrapping Compose . traverse • Relevant bindings include traverseCompose :: (a -> f b) -> g a -> f (h a') (bound at T14172.hs:8:1)