/in/foo.cc:17:19: error: 'Vector2' does not name a type; did you mean 'Vector3'?
   17 |     Vector3(const Vector2& vc)
      |                   ^~~~~~~
      |                   Vector3
/in/foo.cc: In constructor 'Vector3::Vector3(const int&)':
/in/foo.cc:19:17: error: request for member '_x' in 'vc', which is of non-class type 'const int'
   19 |         _x = vc._x;
      |                 ^~
/in/foo.cc:20:17: error: request for member '_y' in 'vc', which is of non-class type 'const int'
   20 |         _y = vc._y;
      |                 ^~
/in/foo.cc:21:17: error: request for member '_z' in 'vc', which is of non-class type 'const int'
   21 |         _z = vc._z;
      |                 ^~
/in/foo.cc: In member function 'Matrix3 Matrix3::operator*(const Matrix3&)':
/in/foo.cc:193:13: warning: unused variable 'matrix' [-Wunused-variable]
  193 |         int matrix[9];
      |             ^~~~~~