Keep defaulted destructors inline

[DanielaE]

applies to exception classes in case of msvc only

[vitaut]

Thanks for the PR but could you elaborate why do this change?

[DanielaE]

Otherwise I see this

fmt-m-pp.lib(fmt-m-pp.obj) : error LNK2005: "public: virtual __cdecl fmt::v7::format_error::~format_error(void)" (??1format_error@v7@fmt@@UEAA@XZ::<!fmt>) already defined in check.obj
check-m-pp.exe : fatal error LNK1169: one or more multiply defined symbols found

in my module compile check as soon as I add an example with a local custom formatter like this:

enum class check_color {red, green, blue};

namespace fmt {
template<> struct formatter<check_color> : formatter<string_view> {
// parse is inherited
    template <typename FormatContext>
    auto format(check_color c, FormatContext& ctx) {
        string_view name = "?";
        switch (c) {
            case check_color::red:   name = "red"; break;
            case check_color::green: name = "green"; break;
            case check_color::blue:  name = "blue"; break;
        }
        return formatter<string_view>::format(name, ctx);
    }
};    
}
result = fmt::format("{}", check_color::blue);

This is probably a defect in msvc, but the change looks beneficial to me for msvc also in the non-modular case. I can see no reason, not to do it. There are no related warnings emitted if I crank the warning level up to maximum and/or enable DLL export. But I can't tell for sure in every usecase, therefor the WIP status.

[vitaut]

I suggest moving this into a separate macro FMT_MSC_DEFAULT that expands to = default if FMT_MSC_VER is set.

[DanielaE]

Yeah, just my thought. I wasn't sure if a single occurence warrants another macro. But now that it's blessed I will change it as suggested tomorrow.