checkedint call removal

[Ary Borenszweig via Digitalmars-d]

On 7/30/14, 12:19 PM, Daniel Murphy wrote:
> "Ary Borenszweig"  wrote in message news:lrb21p$30lf$1 at digitalmars.com...
>
>> > He's asking for assert to mean 'check this condition' and assume to
>> mean
>> > 'optimize as if this is a mathematical identity'.
>>
>> And how is that different if instead of:
>>
>> if (x != 3) assert(0);
>>
>> you write:
>>
>> assume(x != 3);
>
> Because if assert only means 'check this condition' then the optimizer
> can't optimize based on the assumption that it's true.

Assert means: check this condition and terminate the program if it 
doesn't hold.

So why can't the compiler optimize based on this?