status of D optimizers benefiting from contracts ?

[eles via Digitalmars-d-learn]

On Sunday, 9 November 2014 at 16:31:46 UTC, bearophile wrote:
> H. S. Teoh:
>
>> It's only a bad idea because people abuse assert() where it's 
>> not appropriate.
>
> It's a bad idea because Walter seems unable to understand the 
> difference between verifying and proving.

I fail to see the difference between assert() and a hypothetical 
assume().