Implicit string lit conversion to wstring/dstring

[Timon Gehr]

On 03/14/2012 08:34 PM, H. S. Teoh wrote:
> On Wed, Mar 14, 2012 at 02:07:04PM -0500, Andrei Alexandrescu wrote:
>> On 3/14/12 2:01 PM, H. S. Teoh wrote:
>>> However, this change broke this code:
>>>
>>> 	AssociativeArray!(wstring,int) aa;
>>> 	aa["abc"] = 123;	// error: compiler deduces K as string,
>>> 				// so isCompatWithKey!K fails: string
>>> 				// can't implicitly convert to wstring
>>>
>>> Whereas before, when opIndexAssign looked like this:
>>>
>>> 		void opIndexAssign(in Value v, in Key key)
>>> 		{
>>> 			...
>>> 		}
>>>
>>> everything worked, because the compiler deduces the type of "abc" as
>>> wstring since Key==wstring.
>>
>> Aha! This is one of those cases in which built-in magic smells of
>> putrid beef soup.
>
> +1.
>
>
>> I think it's possible to still make this work by beefing up the
>> template constraints such that the working signature is selected for
>> strings.
> [...]
>
> I tried the following, but it still doesn't work properly:
>
> 	void opIndexAssign()(in Value v, in Key key)
> 	{
> 		__opIndexAssignImpl(v, key);
> 	}
>
> 	void opIndexAssign(K)(in Value v, in K key)
> 		if (!is(K==Key)&&  isCompatWithKey!K)
> 	{
> 		__opIndexAssignImpl(v, key);
> 	}
>
> This causes this case to fail:
>
> 	AssociativeArray!(wstring,int) aa;
> 	wchar[] key = "abc"w.dup;
> 	aa[key] = 123;	// Error: template newAA.AA!(immutable(wchar)[],int).AssociativeArray.opIndexAssign() cannot deduce template function from argument types !()(int,wchar[])
>
> I don't understand what's happening here.  The condition "!is(K==Key)"
> is necessary because otherwise the compiler complains that more than one
> template matches the given call, but for some weird reason both
> templates vanish from consideration when the condition is put in.
>
>
> T
>

Use this for now:
void opIndexAssign(K)(in int v, scope K key)
         if (!is(K==Key) && isCompatWithKey!K)
{...}

'in K key'/const(K) key will only IFTI-match a const type. I don't think 
that is sensible at all, you may want to file a bug report.