[Bug c++/85973] [[nodiscard]] on class shall emit a warning for unused anonymous variable

[leonid.satanovsky at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85973

--- Comment #6 from Leonid Satanovsky <leonid.satanovsky at gmail dot com> ---
As you are marking other bugs as duplicates of the current bug, please don't
forget to transfer the useful test cases not mentioned in current bug (e.g.
GccFailedNoDiscard2 case seen below):

struct [[nodiscard]] GccFailedNoDiscard1 {};
struct GccFailedNoDiscard2 { [[nodiscard]] GccFailedNoDiscard2() = default;};
template<class T> struct [[nodiscard]] GccFailedNoDiscard3 {};

struct GccOKNoDiscard1 { [[nodiscard]] GccOKNoDiscard1() {}};
template<class T> struct GccOKNoDiscard2 {
    [[nodiscard]] GccOKNoDiscard2() {}};

int main() {
    GccFailedNoDiscard1 {};
    GccFailedNoDiscard2 {};
    GccFailedNoDiscard3<void> {};
    GccOKNoDiscard1 {};
    GccOKNoDiscard2<void> {};
}