tcfail131.hs:7:9:
Couldn't match expected type ‘b’ with actual type ‘Integer’
‘b’ is a rigid type variable bound by
the type signature for: g :: Num b => b -> b at tcfail131.hs:6:8
Relevant bindings include
x :: b (bound at tcfail131.hs:7:5)
g :: b -> b (bound at tcfail131.hs:7:3)
In the expression: f x x
In an equation for ‘g’: g x = f x x