tcfail133.hs:2:61: warning:
-XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
tcfail133.hs:68:7: error:
Ambiguous type variable ‘r0’ arising from a use of ‘show’
prevents the constraint ‘(Show r0)’ from being solved.
Probable fix: use a type annotation to specify what ‘r0’ should be.
These potential instances exist:
instance Show Module -- Defined in ‘GHC.Show’
instance Show Ordering -- Defined in ‘GHC.Show’
instance Show TrName -- Defined in ‘GHC.Show’
...plus 28 others
(use -fprint-potential-instances to see them all)
In the expression: show
In the expression: show $ add (One :@ Zero) (One :@ One)
In an equation for ‘foo’:
foo = show $ add (One :@ Zero) (One :@ One)
tcfail133.hs:68:14: error:
No instance for (AddDigit (Zero :@ (One :@ One)) One r0)
arising from a use of ‘add’
In the second argument of ‘($)’, namely
‘add (One :@ Zero) (One :@ One)’
In the expression: show $ add (One :@ Zero) (One :@ One)
In an equation for ‘foo’:
foo = show $ add (One :@ Zero) (One :@ One)