Local Classes

Generally speaking it’s always good advice to keep your variables as local as possible. (Unless you have evidence against it for a particular use case). The same can be said for classes. If you have a class that is either not going to be instantiated outside a particular function / lambda or you want to disallow it’s use elsewhere, make it local to that function or lambda.

auto CreateSymbol(int type, int size)
{
    struct Symbol {
        int Type;
        int Size;
    };

    return Symbol{type, size};
}

int GetSymbolSpec()
{
    // Either auto or a template argument is a must
    auto sym = CreateSymbol(6, 8);

    // It's members are still accessible
    return sym.Type + sym.Size;
}

This can be useful in cases such as creating abstract factories, types that are internal to classes, or even just adding a cheap & hidden abstraction.