bad_instance.m:012: In instance declaration for `foo(bar(T), U)':
bad_instance.m:012:   error: the second instance type `U' is a type variable;
bad_instance.m:012:   it should be a type constructor applied to zero or more
bad_instance.m:012:   type variables.
bad_instance.m:016: In instance declaration for `foo(bar(T), T)':
bad_instance.m:016:   error: the second instance type `T' is a type variable;
bad_instance.m:016:   it should be a type constructor applied to zero or more
bad_instance.m:016:   type variables.