First Draft: Implicit Conversion of Template Instantiations

[Walter Bright]

On 3/17/2024 6:32 PM, Timon Gehr wrote:
> Another example of a similar kind of issue:
> 
> ```d
> struct S(T){
>      T x;
> }
> void main(){
>      S!int[] a = [S!int(1),S!int(2),S!int(3)];
>      S!(const(int))[] b = a; // error
> }
> ```
> 
> I think this one may be just an oversight in the prototype implementation.

That should work.