Interesting bug with std.random.uniform and dchar

[monarch_dodra via Digitalmars-d-learn]

On Sunday, 8 June 2014 at 13:55:48 UTC, H. S. Teoh via 
Digitalmars-d-learn wrote:
> On Sun, Jun 08, 2014 at 11:17:41AM +0200, Joseph Rushton 
> Wakeling via Digitalmars-d-learn wrote:
>> On 08/06/14 11:02, monarch_dodra via Digitalmars-d-learn wrote:
>> >Why would we ban uniform!T from accepting dchar? I see no 
>> >reason for that.
>> >
>> >Let's just fix the bug by tweaking the internal check.
>> 
>> Yea, I came to the same conclusion while working on it. :-)
>> 
>> The solution I have is (i) in uniform!"[]" check that 
>> !is(ResultType
>> == dchar) before checking the condition for calling
>> uniform!ResultType, and (ii) inside uniform!T, place
>> 
>>     static if (is(T == dchar))
>>     {
>>         return uniform!"[]"(T.min, T.max, rng);
>>     }
>
> Doesn't wchar need to have a similar specialization too? Aren't 
> some
> values of wchar invalid as well?
>
>
> T

Arguably, the issue is the difference between "invalid" and 
downright "illegal" values. The thing about dchar is that while 
it *can* have values higher than dchar max, it's (AFAIK) illegal 
to have them, and the compiler (if it can) will flag you for it:

dchar c1 = 0x0000_D800; //Invalid, but fine.
dchar c2 = 0xFFFF_0000; //Illegal, nope.