Partial return type specification

[Pelle]

On 10/11/2010 10:56 PM, bearophile wrote:
> Pelle:
>
>> string assertReturnsRangeOf(T)() {
>>       return "static assert (is(Unqual!(ForeachType!(typeof(return))) == "
>>           ~ T.stringof ~ "));";
>> }
>>
>> auto foo() {
>>       return map!q{a*a}([1,2,3,4,5]);
>>       mixin (assertReturnsRangeOf!int);
>> }
>>
>> You were probably looking for a more general and, well, good, solution.
>> This does however convey some intent, and kind of works.
>
> Ideally the partial specification syntax for ranges may work at the calling point too:
>
> void main() {
>      Range!int results = foo();
> }
>
> Here results is of its specific type, it's not a "Range!int", so Range!int works as "auto". The difference is that the compiler makes sure that's an iterable of ints, and not an iterable of floats or a not iterable, etc.
>
> Bye,
> bearophile

This I would very much like. Also, being able to specify that you return 
a Range!int or ForwardRange!int would be very useful. Without losing the 
value types, of course. :-)