Implicit type conversion for function calls?

[Simen Kjaeraas]

On Sun, 10 Jul 2011 21:39:54 +0200, Jonathan M Davis <jmdavisProg at gmx.com>  
wrote:

> On Sunday 10 July 2011 20:47:04 David Nadlinger wrote:
>> On 7/10/11 3:29 PM, Simen Kjaeraas wrote:
>> > I'm trying to have this sort of code compile:
>> >
>> > ////////////////
>> > struct Foo {
>> > int data;
>> > this(int n) {
>> > data = n;
>> > }
>> > }
>> >
>> > void bar(Foo f) {}
>> >
>> > bar(3);
>> > ////////////////
>> >
>> > Is this even possible?
>>
>> If I remember correctly, Walter said that this is a deliberate
>> limitation the last time I asked (when implementing my units of
>> measurement library). I think the intention is to avoid confusion about
>> what is actually going on behind the scenes, like it is possible in C++
>> with implicitly called constructors.
>
> Yes. In C++, the compiler will do up to 3 conversions for you, so you  
> can end
> up calling a very different function than you might have intended to.  
> It's
> usually not a problem, but it can definitely lead to issues and can  
> effectively
> be a form of function hijacking. So, D forces you to do the conversion
> yourself by constructing a temporary of the appropriate type or doing a  
> cast
> or whatnot. I expect that if there is anything that allows you to get  
> away
> with it (such as what Bearophile did), it's a bug.
>
> The only exceptions to this are things which would allow for an implicit  
> cast
> (such as alias this). There has been talk from time to time of adding an
> opImplicitCast, which would allow you to define when this sort of thing  
> coudl
> happen (at least when you've defined the type being passed in), but it's  
> never
> been added to the language, and I think that alias this is pretty much
> supposed to solve that problem, so I don't expect that it ever will.

So then the idea of creating typedef as has been described before (and as
was part of the argument for removing the feature) as a template is
impossible.

-- 
   Simen