range-v3 port: Workaround range-v3's Writable concept requiring operator= to return non-void.
range-v3 port: Workaround range-v3's Writable concept requiring operator= to return non-void.

https://github.com/tahonermann/text_view-range-v3/issues/4

tahonermann/text_view-range-v3,tahonermann/text_view-range-v3