[Bug libstdc++/110970] New: clang / c++23 missing 'typename' prior to dependent type name 'iterator_traits<_It>::iterator_category'

[gcc-bugzilla at zulan dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110970

Bug ID: 110970
   Summary: clang / c++23 missing 'typename' prior to dependent
type name 'iterator_traits<_It>::iterator_category'
   Product: gcc
   Version: 13.2.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: gcc-bugzilla at zulan dot net
  Target Milestone: ---

Using clang with the current libstdc++ and c++23 (2b) fails:

echo "#include " | clang++ -std=c++2b -stdlib=libstdc++ -c -x c++ -
In file included from :1:
In file included from
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/13.2.1/../../../../include/c++/13.2.1/algorithm:60:
In file included from
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/13.2.1/../../../../include/c++/13.2.1/bits/stl_algobase.h:67:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/13.2.1/../../../../include/c++/13.2.1/bits/stl_iterator.h:2618:35:
error: missing 'typename' prior to dependent type name
'iterator_traits<_It>::iterator_category'
  { using iterator_category = iterator_traits<_It>::iterator_category; };


The line is unchanged in the current git, so I presume this is not fixed yet.

Simply adding `typename` to the line does fix the issue with clang.

This is similar to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100900. I won't
try to language lawyer what is technically correct here. In the other issue it
was decided to be nice and support other implementations even though it is a
(very low cost) workaround.

[Bug libstdc++/110970] clang / c++23 missing 'typename' prior to dependent type name 'iterator_traits<_It>::iterator_category'

[gcc-bugzilla at zulan dot net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110970

--- Comment #2 from gcc-bugzilla at zulan dot net ---
Yes, apologies for the missing information

clang version 15.0.7
g++ (GCC) 13.2.1 20230801
(Arch)

According to https://clang.llvm.org/cxx_status.html
P0634R3 / "Down with typename!" is implemented since Clang 16 (released in
March). So maybe this is actually not a problem for much longer. Might only
affect the combination of a very recent GCC with slightly outdated Clang.