The first path segment is unexpectedly interpreted as an authority after normalization

• scheme:/..///bar has scheme="scheme", authority=None, path=/..///bar.
  However, after normalization, it has scheme="scheme", authority="bar".
• Consider t1 as an IRI ..///bar resolved against scheme:.
  t1 should have scheme="scheme" and authority=None (since ..///bar does not contain authority).
  However, resulting string is scheme://bar, it has authority=bar.

And some more examples:

$ python
Python 3.9.9 (main, Jan 10 2022, 18:52:39)
[GCC 11.2.1 20211127] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from rfc3986 import uri_reference
>>> b = uri_reference('scheme:')
>>> r1 = uri_reference('..///bar')
>>> t1 = r1.resolve_with(b)
>>> t1
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> t1.unsplit()
'scheme://bar'
>>> r2 = uri_reference('/..///bar')
>>> r2.resolve_with(b)
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> uri_reference('scheme:/..///bar').normalize()
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> uri_reference('scheme:/..///bar').normalize().unsplit()
'scheme://bar'

I'm not sure how this should handled.
Collapsing the // at the beginning is not explicitly allowed by RFC 3986, so I think the normalization and the resolution cannot produce valid output and should fail in this case.
(But RFC 3986 does not seem to state that they can fail!)

This can caused by normalization during resolution, so #84 may also be affected by this issue.

uri_reference() エントリーポイントから開始し、issue の例と、そこで参照されている RFC 3986 の規則を使って normalize()、resolve_with()、unsplit() を追跡します。authority が存在しない場合に先頭の二重スラッシュをどのように扱うべきかを、issue #84 で指摘されている相互作用も含めて特定します。意図した動作が仕様として定義され、例が最初のパスセグメントを authority として再解釈しなくなれば完了です。