Binding rvalues to ref parameters redux

[bitwise]

On Thursday, 4 April 2019 at 13:43:32 UTC, Atila Neves wrote:
> +1. I *want* `in` to be `scope const`. Any code that breaks as 
> a result of DIP1000 that uses `in` deserves to break anyway.

Do you have any preference on whether or not 'in' is required for 
an rvalue to bind to ref?