SOURCE_FILE
  FN
    ATTR
      POUND "#"
      L_BRACK "["
      META
        PATH
          PATH_SEGMENT
            NAME_REF
              IDENT "foo"
        TOKEN_TREE
          L_PAREN "("
          IDENT "a"
          COMMA ","
          R_PAREN ")"
      R_BRACK "]"
    WHITESPACE "\n"
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "foo"
    PARAM_LIST
      L_PAREN "("
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n"