SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "a"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE " "
        FN
          FN_KW "fn"
          WHITESPACE " "
          NAME
            IDENT "b"
          PARAM_LIST
            L_PAREN "("
            R_PAREN ")"
          WHITESPACE " "
          BLOCK_EXPR
            STMT_LIST
              L_CURLY "{"
              R_CURLY "}"
        WHITESPACE " "
        R_CURLY "}"
  WHITESPACE "\n"
