Returns true if this outcome is successful or its error or exception does not compare equal to the error in the failure type sugar. Comparison is done using operator!= on error_type and A and on exception_type and B.

Requires: operator!= must be a valid expression between error_type and A, or A is void; operator!= must be a valid expression between exception_type and B, or B is void. If error_type is void, then so must be A; if exception_type is void, then so must be B.

Complexity: Whatever the underlying operator!= has. Constexpr and noexcept of underlying operations is propagated.

Guarantees: None.