[PATCH] libstdc++: Implement P3137R3 views::to_input for C++26

[Jonathan Wakely]

On 11/03/25 12:54 -0400, Patrick Palka wrote:
>Hmm good point -- while the to_input_view iterator is always move-only,
>it's not always single pass, the latter property is inherited from the
>underlying range.
>
>Here's an updated patch that uses std::same_as in the testcase, and
>slightly extends the testcase to verify views::to_input is idempotent.
>I also added a missing forward in the views::all branch of to_input.

I definitely prefer the std::same_as test rather than redefining the
'type' alias.

OK for trunk, thanks.