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T8142.hs:6:18: error:
Couldn't match type ‘Nu g0’ with ‘Nu g’
NB: ‘Nu’ is a type function, and may not be injective
The type variable ‘g0’ is ambiguous
Expected type: Nu ((,) t) -> Nu g
Actual type: Nu ((,) t0) -> Nu g0
In the ambiguity check for the inferred type for ‘h’
To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
When checking the inferred type
h :: forall t (g :: * -> *). Nu ((,) t) -> Nu g
In an equation for ‘tracer’:
tracer
= h
where
h = (\ (_, b) -> ((outI . fmap h) b)) . out
T8142.hs:6:57: error:
Couldn't match type ‘Nu ((,) t)’ with ‘g (Nu ((,) t))’
Expected type: Nu ((,) t) -> (t, g (Nu ((,) t)))
Actual type: Nu ((,) t) -> (t, Nu ((,) t))
In the second argument of ‘(.)’, namely ‘out’
In the expression: (\ (_, b) -> ((outI . fmap h) b)) . out
Relevant bindings include
h :: Nu ((,) t) -> Nu g (bound at T8142.hs:6:18)
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