example1_basic_usage.cpp

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#include <iostream>
#include <type_traits>
#include <utility>

class NonDefaultConstructible {
public:
    NonDefaultConstructible(int) {}
    int getValue() const { return 42; }
};

int main() {
    using T = decltype(std::declval<NonDefaultConstructible>().getValue());
    std::cout << "The return type of getValue() is " 
              << (std::is_same<T, int>::value ? "int" : "not int") << std::endl;
    return 0;
}