SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "f"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        WHITESPACE "\n    "
        LET_STMT
          LET_KW "let"
          WHITESPACE " "
          WILDCARD_PAT
            UNDERSCORE "_"
          WHITESPACE " "
          EQ "="
          WHITESPACE " "
          BIN_EXPR
            BLOCK_EXPR
              STMT_LIST
                L_CURLY "{"
                LITERAL
                  INT_NUMBER "1"
                R_CURLY "}"
            WHITESPACE " "
            AMP "&"
            WHITESPACE " "
            LITERAL
              INT_NUMBER "2"
          SEMICOLON ";"
        WHITESPACE "\n    "
        EXPR_STMT
          BLOCK_EXPR
            STMT_LIST
              L_CURLY "{"
              LITERAL
                INT_NUMBER "1"
              R_CURLY "}"
        WHITESPACE " "
        EXPR_STMT
          REF_EXPR
            AMP "&"
            LITERAL
              INT_NUMBER "2"
          SEMICOLON ";"
        WHITESPACE "\n"
        R_CURLY "}"
  WHITESPACE "\n"
