Disable implicit conversion

[spir]

On 03/07/2011 05:40 PM, Jesse Phillips wrote:
> KennyTM~ Wrote:
>
>> On Mar 7, 11 18:33, Eugene wrote:
>>> Hi!
>>>
>>> What I want to do is pretty simple.  I need to subtract a ubyte from a
>>> ubyte and store the result in a ubyte.  The problem is that DMD
>>> implicitly wants to convert the ubytes into an integer, so it fails
>>> when attempting to store the result into a ubyte.  (Int cannot be
>>> converted to ubyte?)
>>> The error message I get:
>>>
>>> src\test.d(26): Error: cannot implicitly convert expression
>>> (cast(int)u2 - cast(int)u1) of type int to ubyte
>>
>> ubyte u3 = (u2 - u1)&  0xff;
>> //                ^^^^^^
>> //                   make sure the result fall in ubyte's value range
>
> I recommend against this for a number of reasons.
>
> For one this removes an explicit cast which makes it harder to find for review (one of the reasons for cast() instead of ().
>
> Not only that but the operation isn't any safer than a cast, if overflow didn't matter and you just need it to fit then this would be good.
>
> Lastly overflow does matter and if it happens the code will continue to silently work. I recommend using std.conv.to because it will throw an exception if an overflow were to happen.

I agree. Then, why do we still have cast?

Denis
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