On Mon, 24 Feb 2020, Patrick Palka wrote:
> libstdc++-v3/ChangeLog:
>
> LWG 3301 transform_view::_Iterator has incorrect iterator_category
> * include/std/ranges (transform_view::_Iterator::_S_iter_cat): Adjust
> determination of iterator_category as per LWG 3301.
> * testsuite/std/ranges/adaptors/transform.cc: Augment test.
> ---
> libstdc++-v3/include/std/ranges | 16 +++++++++----
> .../std/ranges/adaptors/transform.cc | 24 +++++++++++++++++++
> 2 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index ab8fbaca38f..aed90e9710e 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -1570,12 +1570,18 @@ namespace views
> static constexpr auto
> _S_iter_cat()
> {
> - using _Cat
> - = typename iterator_traits<_Base_iter>::iterator_category;
> - if constexpr (derived_from<_Cat, contiguous_iterator_tag>)
> - return random_access_iterator_tag{};
> + using _Res = invoke_result_t<_Fp&, range_reference_t<_Base>>;
Consider this line fixed to use 'typename'.
> + if constexpr (is_lvalue_reference_v<_Res>)
> + {
> + using _Cat
> + = typename iterator_traits<_Base_iter>::iterator_category;
> + if constexpr (derived_from<_Cat, contiguous_iterator_tag>)
> + return random_access_iterator_tag{};
> + else
> + return _Cat{};
> + }
> else
> - return _Cat{};
> + return input_iterator_tag{};
> }
>
> static constexpr decltype(auto)
> diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> index ad51fffb43d..0845febe2cf 100644
> --- a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc
> @@ -77,10 +77,34 @@ test03()
> VERIFY( ranges::equal(v, (int[]){1,2,3,4,5}) );
> }
>
> +void
> +test04()
> +{
> + // LWG 3302
Consider this comment fixed to say 3301.
