T12151.hs:9:13: error:
    • The default type signature for put: forall t. t
      does not match its corresponding non-default type signature
    • When checking the class method: put :: forall a. Put a => a
      In the class declaration for ‘Put’

T12151.hs:9:13: error:
    • Could not deduce (Put a0)
      from the context: Put a
        bound by the type signature for:
                   put :: forall a t. Put a => t
        at T12151.hs:9:13-15
      The type variable ‘a0’ is ambiguous
    • In the ambiguity check for ‘put’
      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
      When checking the class method: put :: forall a. Put a => a
      In the class declaration for ‘Put’