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    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          IDENT_PAT
            REF_KW "ref"
            WHITESPACE " "
            ERROR
              BOX_KW "box"
        WHITESPACE " "
        EXPR_STMT
          BIN_EXPR
            PATH_EXPR
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "i"
            WHITESPACE " "
            EQ "="
            WHITESPACE " "
            TUPLE_EXPR
              L_PAREN "("
              R_PAREN ")"
          SEMICOLON ";"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          IDENT_PAT
            MUT_KW "mut"
            WHITESPACE " "
            ERROR
              BOX_KW "box"
        WHITESPACE " "
        EXPR_STMT
          BIN_EXPR
            PATH_EXPR
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "i"
            WHITESPACE " "
            EQ "="
            WHITESPACE " "
            TUPLE_EXPR
              L_PAREN "("
              R_PAREN ")"
          SEMICOLON ";"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          IDENT_PAT
            REF_KW "ref"
            WHITESPACE " "
            MUT_KW "mut"
            WHITESPACE " "
            ERROR
              BOX_KW "box"
        WHITESPACE " "
        EXPR_STMT
          BIN_EXPR
            PATH_EXPR
              PATH
                PATH_SEGMENT
                  NAME_REF
                    IDENT "i"
            WHITESPACE " "
            EQ "="
            WHITESPACE " "
            TUPLE_EXPR
              L_PAREN "("
              R_PAREN ")"
          SEMICOLON ";"
        WHITESPACE "\n"
        R_CURLY "}"
  WHITESPACE "\n\n"
error 24: expected a name
error 27: expected SEMICOLON
error 48: expected a name
error 51: expected SEMICOLON
error 76: expected a name
error 79: expected SEMICOLON