Operator implicit conversion difference

[Ali Çehreli via Digitalmars-d-learn]

On 11/06/2015 04:56 PM, BBaz wrote:
> On Thursday, 5 November 2015 at 13:20:26 UTC, ixid wrote:
>> This may have been overlooked in my other thread so I wanted to ask
>> again:
>>
>> This seems very inconsistent, does a += b not lower to a = a + b? I
>> guess not based on the below:
>>
>>     ushort a = ushort.max, b = ushort.max;
>>
>>
>>     a += b; // Compiles fine
>>     a = a + b; // Error: cannot implicitly convert expression
>> (cast(int)a + cast(int)b) of type int to ushort
>
> What's inconsistent is the integral promotion of the add expression
> result that stops from 4 bytes int:
>
> ---
> int a, b;
> a += b;
> a = a + b;
> ---
>
> is compiled but according to the specs, a + b result should be widened
> to long:
>
> http://dlang.org/expression.html#AddExpression
>
> (ubyte, byte) until (uint int) should be widened and (long , ulong)
> wrapped. This behavior would match the specs better.

You say 'long' but according to integer promotions, a and b should both 
be promoted to 'int' and the result of 'a + b' is int:

   http://dlang.org/type.html#integer-promotions

Ali