`in` no longer same as `const ref`

[Nordlöw via Digitalmars-d]

On Monday, 30 January 2017 at 11:32:11 UTC, Walter Bright wrote:
> I'd rather do one thing at a time.

+1

And it won't be too difficult to search-and-replace `const scope` 
with `in` once things has stabilized and all the corner cases 
have been sorted out.

Thanks for making D more safe, Walter. D really needs it in the 
competition with Rust.

Once things have stabilized we really need to announce this work 
and highlight its developer productivity compared to Rust.