#include <iostream>
 
    struct TestStructure;
 
    void TestFunction(TestStructure* /*unused*/) {
        std::cout << "Free TestFunction\n";
    }
 
    struct TestStructure {
        int i;
        void TestFunction(TestStructure* /*unused*/) {
            std::cout << "TestStructure TestFunction\n";
        }
        void foo() {
            std::cout << "From foo\n";
            TestFunction(this);
        }
    };
 
    int main() {
        std::cout << "From main:\n";
        TestFunction(nullptr);
 
        TestStructure t;
        t.foo();
    }
 

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