operator == method
override
    This is equal only to an error result with equal error and stackTrace.
Implementation
bool operator ==(Object other) =>
    other is ErrorResult &&
    error == other.error &&
    stackTrace == other.stackTrace;
    This is equal only to an error result with equal error and stackTrace.
bool operator ==(Object other) =>
    other is ErrorResult &&
    error == other.error &&
    stackTrace == other.stackTrace;