P1739 Type erasure for forwarding ranges in combination with "subrange-y" view adaptors

[wg21bot]

P1739R0 Type erasure for forwarding ranges in combination with "subrange-y" view adaptors (Hannes Hauswedell)

[wg21bot]

Depends on P1391 Range constructor for std::string_view #184.

[tituswinters]

Discussed in Cologne: http://wiki.edg.com/bin/view/Wg21cologne2019/P1739

Forward to LWG including the presented check for iterator-sentinels and empty_view for C++20.
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The presentation, which is linked from the wiki, included preference-ordered Concept checks for iterator-sentinels in order to reduce template instantiations, and support for this form of erasure (that's the wrong term) for empty_view.

Forwarding to LWG. This would be a breaking change to adopt after C++20, so it's reasonably high priority.

[wg21bot]

P1739R2 Avoid template bloat for forwarding ranges in combination with 'subrange-y' view adaptors. (Hannes Hauswedell (h2 AT fsfe.org))

[mclow]

This was not adopted for C++20. Removing the "C++20" label.