SOURCE_FILE
  FN
    FN_KW "fn"
    WHITESPACE " "
    NAME
      IDENT "foo"
    PARAM_LIST
      L_PAREN "("
      PARAM
        DOT3 "..."
      COMMA ","
      WHITESPACE " "
      PARAM
        TUPLE_PAT
          L_PAREN "("
          IDENT_PAT
            NAME
              IDENT "x"
          COMMA ","
          WHITESPACE " "
          IDENT_PAT
            NAME
              IDENT "y"
          R_PAREN ")"
        COLON ":"
        WHITESPACE " "
        TUPLE_TYPE
          L_PAREN "("
          PATH_TYPE
            PATH
              PATH_SEGMENT
                NAME_REF
                  IDENT "i32"
          COMMA ","
          WHITESPACE " "
          PATH_TYPE
            PATH
              PATH_SEGMENT
                NAME_REF
                  IDENT "i32"
          R_PAREN ")"
      R_PAREN ")"
    WHITESPACE " "
    BLOCK_EXPR
      STMT_LIST
        L_CURLY "{"
        R_CURLY "}"
  WHITESPACE "\n"
