(Program
  (ExpressionStatements
    (Function
      (Identifier)
      (Params)
      (Other "variable_declaration"
        (VarAssignment
          (Identifier)
          (NumberLiteral)))
      (ExpressionStatements
        (Yield
        { (MathOperator
            (Identifier)
            (Other "++"))
        ->(Identifier) })))))