checkedint call removal

[John Colvin via Digitalmars-d]

On Sunday, 27 July 2014 at 20:20:54 UTC, Walter Bright wrote:
> On 7/27/2014 6:52 AM, bearophile wrote:
>> A possible piece of the solution is the recently suggested 
>> __trait(valueRange,
>> exp), but alone that's not enough.
>
> Instead of adding more language features, purpose existing ones:
>
>     assert(exp >= min && exp <= max);

To what extent can a compiler use assertions? Can it work 
backwards from an assert to affect previous code?

void foo(int a)
{
     enforce(a & 1);
     assert(a & 1);
}

void bar()
{
     assert(a & 1);
     enforce(a & 1);
}

Which, if either, of those calls to enforce can be removed?