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T7148.hs:27:40:
Could not coerce from ‛SameType b1 b’ to ‛SameType b1 (Tagged a b)’
because the second type argument of ‛SameType’ has role Nominal,
but the arguments ‛b’ and ‛Tagged a b’ differ
arising from the coercion of the method ‛iso2’ from type
‛forall b. SameType b () -> SameType b b’ to type
‛forall b. SameType b () -> SameType b (Tagged a b)’
Possible fix:
use a standalone 'deriving instance' declaration,
so you can specify the instance context yourself
When deriving the instance for (IsoUnit (Tagged a b))
T7148.hs:27:40:
Could not coerce from ‛SameType b b1’ to ‛SameType (Tagged a b) b1’
because the first type argument of ‛SameType’ has role Nominal,
but the arguments ‛b’ and ‛Tagged a b’ differ
arising from the coercion of the method ‛iso1’ from type
‛forall b. SameType () b -> SameType b b’ to type
‛forall b. SameType () b -> SameType (Tagged a b) b’
Possible fix:
use a standalone 'deriving instance' declaration,
so you can specify the instance context yourself
When deriving the instance for (IsoUnit (Tagged a b))
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