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T5934.hs:12:7: error:
• Cannot instantiate unification variable ‘a0’
with a type involving foralls: (forall s. GenST s) -> Int
GHC doesn't yet support impredicative polymorphism
• In the expression: 0
In an equation for ‘run’: run = 0
T5934.hs:12:7: error:
• Ambiguous type variable ‘a0’ arising from the literal ‘0’
prevents the constraint ‘(Num a0)’ from being solved.
Probable fix: use a type annotation to specify what ‘a0’ should be.
These potential instances exist:
instance Num Integer -- Defined in ‘GHC.Num’
instance Num Double -- Defined in ‘GHC.Float’
instance Num Float -- Defined in ‘GHC.Float’
...plus two others
(use -fprint-potential-instances to see them all)
• In the expression: 0
In an equation for ‘run’: run = 0
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