The name is "self" not "this". "this" is a keyword indicating it's the explicit object parameter, it's not even actually a type.

C++ seems to be trying to maximise confusion these days.

  struct foo
  {
    void bar(int a, int b) {
      auto lambda = [&] (auto this self) { 
        this->compute();
      };
    }

    void compute();
  };

if the variable name was "auto this" you wouldn't be able to refer to "compute" through the "this" of the parent class here