On Friday, 12 February 2016 at 15:12:19 UTC, Steven Schveighoffer wrote:
> but I'm unaware of such an optimization, and it definitely isn't triggered specifically by 'in'. 'in' is literally replaced with 'scope const' when it is a storage class.
>
> -Steve

I'd imagine GCC or LLVM may be able to make use of such (type) information for optimizations — moreso probably LLVM due to all the functional languages that use it nowadays.