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NamedWildcardsNotInMonotype.hs:5:1: error:
• Could not deduce (Eq w0)
from the context: (Show a, Eq w, Eq a)
bound by the inferred type for ‘foo’:
forall {a} {w}. (Show a, Eq w, Eq a) => a -> a -> String
at NamedWildcardsNotInMonotype.hs:5:1-33
The type variable ‘w0’ is ambiguous
Potentially matching instances:
instance Eq Ordering -- Defined in ‘GHC.Classes’
instance Eq () -- Defined in ‘GHC.Classes’
...plus 22 others
...plus four instances involving out-of-scope types
(use -fprint-potential-instances to see them all)
• In the ambiguity check for the inferred type for ‘foo’
To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
When checking the inferred type
foo :: forall {a} {w}. (Show a, Eq w, Eq a) => a -> a -> String
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