Class template argument deduction from constructor call

[div0]

On 27/10/2010 21:02, "Jérôme M. Berger" wrote:
> div0 wrote:
>> On 27/10/2010 20:36, sergk wrote:
>>> class Foo(T) {
>>>       this(T t) {
>>>           bar = t;
>>>       }
>>>       T bar;
>>> }
>>>
>>> void main() {
>>>       auto a = new Foo(123); // doesn't work
>>>       auto b = new Foo!(int)(123); // work, but redundant
>>> }
>>>
>>> Is there any technical limitations preventing this, or its just a
>>> compiler bug?
>>
>> It's not a bug.
>>
>> I guess it could be a short cut, but it can only ever work when the
>> class has exactly one constructor, which seems a bit of a pointless
>> short cut and adds an unneccassiry corner case to the language spec.
>>
> 	Why would it only be able to work when there is exactly one
> constructor? Doesn't function overloading work with templates?
>
> 	This works here:
>
> void foo(T) (T x) {
> }
>
> void foo(T, U) (T x, U y) {
> }
>
> void main()
> {
>      foo (3);
>      foo (3, "azerty");
> }
>
> 		Jerome

class Foo(T) {
        this(T t) {
            bar = t;
        }

	this(string x) {
	}

	this(int x) {
	}

        T bar;
}

auto	f0 = new Foo("wtf?");
auto	f1 = new Foo(42);

What's T in any of the above?

There's no obvious answer for the first 2 and anything anybody says will 
be a source of endless arguments and bike shedding.

-- 
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk