警告 C26812：枚举类型“utils::TwilightTypes”未限定范围。 更喜欢“枚举类”而不是“枚举”（Enum.3）

Question

I'm developing a library using Visual Studio 2019 and C++ on Windows 10.

I have the header file "Utils.h" with this declaration:

namespace utils {

    enum TwilightTypes
    {
        Civil,
        Nautical,
        Astronomical
    };

And in the header file "TheSun.h" this class that uses the enum:

#pragma once
#include "Utils.h"

class TheSun
{
private:

public:

    // 50. Twilight
    utils::RiseSetTime Twilight(
        utils::TwilightTypes type,
        utils::dateTime date,
        double longitude,
        char longOrientation,
        double latitude,
        char latOrientation);
};

But, in the implementation of that method, in file "TheSun.cpp" I get the following warning:

warning C26812: The enum type 'utils::TwilightTypes' is unscoped. Prefer 'enum class' over 'enum' (Enum.3).

I have changed the declaration of the enum to:

namespace utils {

    enum class TwilightTypes
    {
        Civil,
        Nautical,
        Astronomical
    };

But I get the same warning.

How can I remove this warning?

I have also move the enum declaration to the header file "TheSun.h", and I get the same warning.

I have only one enum in this solution.

I always clean and rebuild the entire solution.

From Microsoft documentation, here is the explanation of the warning:

Reason

To minimize surprises: traditional enums convert to int too readily.

Enforcement

(Simple) Warn on any non-class enum definition.