P2447R6 Constructing `span<const T>` From `initializer_list<T>`

[StephanTLavavej]

WG21-P2447R6 Constructing span<const T> From initializer_list<T>
LWG-4293 span::subspan/first/last chooses wrong constructor when T is const-qualified bool

Feature-test macro:

#define __cpp_lib_span_initializer_list 202311L

This ctor should participate in STL Hardening (#5090) like the other span ctors.

Note: We are not yet accepting PRs for C++26 features.

[lamarrr]

@StephanTLavavej I'd like to take on this if it's still available

[frederick-vs-ja]

Reverted by WG21-P4144R1, although LWG-4293 isn't reverted. Mainly "Nothing To Do" now, and LWG-4293 is now non-functional change.

[StephanTLavavej]

Thanks, retroactively marking this as a non-feature. I've split out #6239 for LWG-4293.