T13526.hs:21:8: warning: [-Wsimplifiable-class-constraints (in -Wdefault)]
    • The constraint ‘C (Maybe a)’ matches
        instance C a => C (Maybe a) -- Defined at T13526.hs:14:10
      This makes type inference for inner bindings fragile;
        either use MonoLocalBinds, or simplify it using the instance
    • In the type signature: bar :: C (Maybe a) => a -> Maybe a