(int << ulong) == int ?

[Don]

Jonathan M Davis wrote:
> On Monday 08 August 2011 00:33:31 Dmitry Olshansky wrote:
>> Just lost the best part of an hour figuring the cause of this small
>> problem, consider:
>>
>> void main()
>> {
>>          uint j = 42;
>>          ulong k = 1<<cast(ulong)j;
>>          ulong m = 1UL<<j;
>>          assert(k == 1024);//both asserts do pass
>>          assert(m == (1UL<<42));
>> }
>>
>> I though left operand should be promoted to the largest integer in shift
>> expression, isn't it?
> 
> I would not expect that type of integer being used to give the number of bits 
> to shift to affect thet type of integer being shifted. It doesn't generally 
> make much sense to shift more than the size of the integer type being shifted, 
> and that can always fit in a byte. So, why would the type of the integer being 
> used to give the number of bits to shift matter? It's like an index. The index 
> doesn't affect the type of what's being indexed. It just gives you an index.
> 
> You have to deal with integer promotions and all that when doing arithmetic, 
> because arithmetic needs to be done with a like number of bits on both sides 
> of the operation. But with shifting, all your doing is asking it to shift some 
> number of bits. The type which holds the number of bits shouldn't really 
> matter. I wouldn't expect _any_ integer promotions to occur in a shift 
> expression. If you want to affect what's being shifted, then cast what's being 
> shifted.

Your intuition is wrong!

expression.html explicitly states the operands to shifts undergo 
integral promotions. But they don't get arithmetic conversions.

I think this is terrible.

short x = -1;
x >>>= 1;

Guess what x is...