[PATCH] D57058: Implement LWG3101 - span's Container constructors need another constraint

[Louis Dionne via Phabricator]

ldionne added a comment.

This LGTM but I'd like to understand the situation I commented on with the rvalue before we commit this.



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Comment at: test/std/containers/views/span.cons/container.fail.cpp:72
     {
     std::span<int>    s1{IsAContainer<int>()};          // expected-error {{no matching constructor for initialization of 'std::span<int>'}}
     std::span<int>    s3{NotAContainerNoData<int>()};   // expected-error {{no matching constructor for initialization of 'std::span<int>'}}
----------------
mclow.lists wrote:
> ldionne wrote:
> > Why does this fail? Shouldn't this use `std::span<int, std::dynamic_extent>::span(Container const&)`?
> Because it's an rvalue?  Dunno; but if so, that makes all the other tests useless. I will investigate.
> 
I think it should compile because the `Container const&` will bind to a rvalue (and then the `std::span` contains a dangling reference).


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