Back

When implementing generic code that relies on decltype, you can run into a problem.

If a type cannot be default constructed, we won't be able to spell an instantiation of that type within an expression.

Using std::declval, we can obtain an lvalue reference without creating a value.

Note that std::declval can only be used in unevaluated contexts (e.g. decltype).

Compiler Explorer link: https://compiler-explorer.com/z/KK8frnf51