Unfound typo on main resulting in collect2 error [duplicate]

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• What is an undefined reference/unresolved external symbol error and how do I fix it? 27 answers

I have a C++ project hosted here that throws that error : Dans la fonction « main » : main.cpp:(.text+0x58) : référence indéfinie vers « Jeu::Jeu(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, int) » collect2: error: ld returned 1 exit status

I really would like to know why. Other related error on collect2 send back to a typo error ; either I can not a spot a typo in a 7-line file either there is something trickier, what is it ?