Concepts like c++20 with specialized overload resolution.

[vushu]

On Saturday, 27 May 2023 at 16:38:43 UTC, Steven Schveighoffer 
wrote:
> On 5/27/23 9:50 AM, vushu wrote:
>> On Saturday, 27 May 2023 at 13:42:29 UTC, Basile B. wrote:
>>> [...]
>> 
>> Yes I know there is template constraint, but not with 
>> specialized overloading right?
>> 
>> so you need to use static if for checking if it hasmagma.
>
> What is missing is an "else" thing.
>
> So you have to repeat the constraint (as a negation) 
> unfortunately.
>
> e.g.:
>
> ```d
> struct LavaMan {
>   void magma() { writeln(" LavaMan is throwing LAVA"); }
> }
>
> struct FakeVulcano {
>   void try_making_lava() { writeln(" Making fake lava"); }
> };
>
> void make_lava(T)(ref T lava) if (hasMagma!T) {
>     lava.magma();
> }
>
> void make_lava(T)(ref T lava_thing) if (!hasMagma!T){
>     lava_thing.try_making_lava();
> }
> ```
>
> -Steve


I see thanks for the example :), I think this probably the 
closest equivalent i dlang.