SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "main"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE "\n    "
        EXPR_STMT
          CLOSURE_EXPR
            PARAM_LIST
              PIPE "|"
              PIPE "|"
            WHITESPACE " "
            RET_TYPE
              THIN_ARROW "->"
              WHITESPACE " "
              TUPLE_TYPE
                L_PAREN "("
                R_PAREN ")"
        WHITESPACE " "
        EXPR_STMT
          BLOCK_EXPR
            UNSAFE_KW "unsafe"
            WHITESPACE " "
            STMT_LIST
              L_CURLY "{"
              WHITESPACE " "
              TUPLE_EXPR
                L_PAREN "("
                R_PAREN ")"
              WHITESPACE " "
              R_CURLY "}"
          SEMICOLON ";"
        WHITESPACE "\n"
        R_CURLY "}"
  WHITESPACE "\n"
error 24: expected a block
error 24: expected SEMICOLON