T4921.hs:10:9: error:
• Ambiguous type variables ‘a0’, ‘b1’ arising from a use of ‘f’
prevents the constraint ‘(C a0 b1)’ from being solved.
Relevant bindings include x :: a0 (bound at T4921.hs:10:1)
Probable fix: use a type annotation to specify what ‘a0’, ‘b1’ should be.
These potential instance exist:
instance C Int Char -- Defined at T4921.hs:7:10
• In the first argument of ‘fst’, namely ‘f’
In the expression: fst f
In an equation for ‘x’: x = fst f
T4921.hs:12:9: error:
• Ambiguous type variable ‘b0’ arising from a use of ‘f’
prevents the constraint ‘(C Int b0)’ from being solved.
Probable fix: use a type annotation to specify what ‘b0’ should be.
These potential instance exist:
instance C Int Char -- Defined at T4921.hs:7:10
• In the first argument of ‘fst’, namely ‘f’
In the expression: fst f :: Int
In an equation for ‘y’: y = fst f :: Int