String view literals in header file

Question

I've got a class that has a bunch of constant strings, in the form of:

using namespace std::string_view_literals;
class T {
  static const constexpr std::string_view something1 = "Alice"sv;
  static const constexpr std::string_view something2 = "Bob"sv;
  static const constexpr std::string_view something3 = "Charlie"sv;

  ...
};

I'm currently using the string_view_literals namespace, but this isn't good practice in a header file, and generates warnings:

Using namespace directive in global context in header [-Wheader-hygiene] (clang)

literal operator suffixes not preceded by '_' are reserved for future standardization [-Wliteral-suffix] (gcc7)

I'd like to look at other options.

1. Ignore the warnings

2. Directly import the one literal I'm using, instead of the whole namespace

   using std::string_view_literals::operator""sv

3. Since this is a constexpr constant, perhaps I should just call the constructor directly, knowing it has no runtime memory or CPU overhead:

   static const constexpr something1 = std::string_view("Alice");

4. Something else?

Answer 1

This is pretty short and doesn't pollute anything:

class T {
    using sv = std::string_view;
    static constexpr auto something1 = sv("Alice");
    static constexpr auto something2 = sv("Bob");
    static constexpr auto something3 = sv("Charlie");
};

If you really want to use the literal, you could wrap your class in another not-intended-to-be-named namespace and then bring it back into the outer namespace:

namespace _private {
    using namespace std::string_view_literals;

    class T {
        static constexpr auto something1 = "Alice"sv;
        static constexpr auto something2 = "Bob"sv;
        static constexpr auto something3 = "Charlie"sv;
    };
}

using _private::T;

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Note that writing static constexpr const is redundant. constexpr variables are implicitly const.