array of elements of various sybtypes

[spir]

On 01/26/2011 07:29 PM, Jesse Phillips wrote:
> spir Wrote:
>
>> Hello,
>>
>> This fails:
>>
>> class T0 {}
>> class T1 : T0 {}
>> class T2 : T0 {}
>>
>> unittest {
>>       auto t1 = new T1();
>>       auto t2 = new T2();
>>       T0[] ts = [t1, t2];
>> }
>>
>> Error: cannot implicitly convert expression (t1) of type __trials__.T0 to
>> __trials__.T2
>> Error: cannot implicitly convert expression ([(__error),t2]) of type T2[] to T0[]
>
> D takes the type of the last element. I guess it has been decided to take the common type but hasn't been implemented. Anyway your two reasonable options are:
>
> auto ts = to!(T0[])([...]);
>
> auto ts = [new T1(), to!(T0)(new T2())]
>
> I recommend using std.conv.to instead of a cast because it is safer. Though cast is a no-op and isn't any less safe in this case.

Right, casting a /single/ element works:
     auto x = [cast(T0)(t1), t2];
     auto y = [t1, cast(T0)(t2)];

But to! fails:
     auto x = [to!(T0)(t1), t2];
     auto y = [t1, to!(T0)(t2)];
/usr/include/d/dmd/phobos/std/conv.d(99): Error: template std.conv.toImpl(T,S) 
if (!implicitlyConverts!(S,T) && isSomeString!(T) && isInputRange!(Unqual!(S)) 
&& isSomeChar!(ElementType!(S))) toImpl(T,S) if (!implicitlyConverts!(S,T) && 
isSomeString!(T) && isInputRange!(Unqual!(S)) && isSomeChar!(ElementType!(S))) 
matches more than one template declaration, 
/usr/include/d/dmd/phobos/std/conv.d(559):toImpl(Target,Source) if 
(implicitlyConverts!(Source,Target)) and 
/usr/include/d/dmd/phobos/std/conv.d(626):toImpl(T,S) if (is(S : Object) && 
is(T : Object))

Already had this endless error message once ;-)
Looks like another bug of non mutually exclusive template constraints?

Denis
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