[Bug libstdc++/84118] New: filesystem::path concat does not accept value_type

[ethan at ethanhs dot me]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84118

            Bug ID: 84118
           Summary: filesystem::path concat does not accept value_type
           Product: gcc
           Version: 7.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ethan at ethanhs dot me
  Target Milestone: ---

As I have read the filesystem TS, I believe concat on path items should have an
overload following:

path& operator+=(value_type x);

However, on trying to use 7.2.0 this overload seems not to work correctly.

https://wandbox.org/permlink/S4DZ3witD15xz0lT

TL;DR it would allow for constructs such as
.concat(fs::path::preferred_separator)