holes2.hs:3:5: warning: [-Wdeferred-type-errors (in -Wdefault)]
• Ambiguous type variable ‘a0’ arising from a use of ‘show’
prevents the constraint ‘(Show a0)’ from being solved.
Probable fix: use a type annotation to specify what ‘a0’ should be.
These potential instances exist:
instance (Show a, Show b) => Show (Either a b)
-- Defined in ‘Data.Either’
instance Show Ordering -- Defined in ‘GHC.Show’
instance Show Integer -- Defined in ‘GHC.Show’
...plus 23 others
...plus 70 instances involving out-of-scope types
(use -fprint-potential-instances to see them all)
• In the expression: show _
In an equation for ‘f’: f = show _
holes2.hs:3:10: warning: [-Wtyped-holes (in -Wdefault)]
• Found hole: _ :: a0
Where: ‘a0’ is an ambiguous type variable
• In the first argument of ‘show’, namely ‘_’
In the expression: show _
In an equation for ‘f’: f = show _
• Relevant bindings include f :: String (bound at holes2.hs:3:1)
Valid hole fits include
f :: String
otherwise :: Bool
False :: Bool
True :: Bool
LT :: Ordering
EQ :: Ordering
GT :: Ordering
() :: ()
pi :: forall a. Floating a => a