3794. std::filesystem::path::iterator::reference should be allowed to be std::filesystem::path

Section: 31.12.6.6 [fs.path.itr] Status: New Submitter: Jiang An Opened: 2022-10-17 Last modified: 2022-11-01

Priority: 3

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Discussion:

Currently, 31.12.6.6 [fs.path.itr]/2 effectively requires std::filesystem::path::iterator::reference to be a reference type, due to the requirements for (legacy) bidirectional iterators. However, it's reasonable for the operator* to return path by value, which can make the iterator model std::bidirectional_iterator, be compatible with std::reverse_iterator, and avoid complicated data structures (e.g. those in libstdc++) for achieving such purpose.

libc++ is already doing so. I think we should make such a strategy conforming.

[2022-11-01; Reflector poll]

Set priority to 3 after reflector poll.

Proposed resolution:

This wording is relative to N4917.

1. Modify 31.12.6.6 [fs.path.itr] as indicated:

   -2- A path::iterator is a constant iterator meeting all the requirements of a bidirectional iterator (24.3.5.6 [bidirectional.iterators]) except that, for dereferenceable iterators a and b of type path::iterator with a == b, there is no requirement that *a and *b are bound to the same object, and its reference may be path. Its value_type is path.