constexpr_const_char.cpp

#include <cstdint>
#include <print>
#include <string_view>

class A {
public:
    static constexpr const char* Key1 = "Key1";
    static inline const char* Key2 = "Key2";
    static inline const char* const Key3 = "Key3";
};

consteval bool IsValidKey(std::string_view key)
{
    return (key == "Key1") || (key == "Key2") || (key == "Key3");
}

template <typename T>
void tmp()
{
    if constexpr (IsValidKey(A::Key1) == false) {
        static_assert(false);
    }
    // if constexpr (IsValidKey(A::Key2) == false) {
    //     static_assert(false);
    // }
    if constexpr (IsValidKey(A::Key3) == false) { // cl compilable, but clang & gcc eror
        static_assert(false);
    }
}

auto main() -> int32_t
{
    std::println("Key1: {}, Key2: {}, Key3: {}", A::Key1, A::Key2, A::Key3);

    // A::Key1 = "NewKey1"; // Error: cannot modify a constexpr variable
    A::Key2 = "NewKey2"; // Allowed: Key2 is a static inline variabl
    // A::Key3 = "NewKey3"; // Error: cannot modify a const variable

    constexpr auto key1_valid = IsValidKey(A::Key1);
    // constexpr auto key2_valid = IsValidKey(A::Key2);
    constexpr auto key3_valid = IsValidKey(A::Key3); // cl compilable, but lint & gcc eror

    std::println("{} is a valid key: {}", "Key1", IsValidKey(A::Key1));
    // std::println("{} is a valid key: {}", "Key1", IsValidKey(A::Key2));
    std::println("{} is a valid key: {}", "Key1", IsValidKey(A::Key3)); // cl compilable, but lint & gcc eror

    std::println("Key1: {}, Key2: {}, Key3: {}", A::Key1, A::Key2, A::Key3);

    tmp<int32_t>();
}