Any way to reproduce Dart style constructors?

[Nicholas Wilson via Digitalmars-d-learn]

On Thursday, 25 May 2017 at 08:34:54 UTC, JN wrote:
> One of my favourite language features of Dart (other one being 
> factory constructors) are auto-assign constructors, for example 
> (writing it in pseudo-D):
>
> class Person
> {
>   string name;
>   int age;
>   this(this.age, this.name);
> }
>
> would translate to
>
> class Person
> {
>   string name;
>   int age;
>   this(int age, string name)
>   {
>     this.age = age;
>     this.name = name;
>   }
> }
>
>
> It saves a lot of typing in the long run when doing lots of 
> OOP, is there a way to reproduce such behaviour using mixins? I 
> was thinking of some interface like:
>
> class Person
> {
>   string name;
>   int age;
>   mixin(AutoConstructor!(age, name));
> }
>
> but I don't know if that's even doable using mixins. Even 
> cooler might be something like an annotation (feels a bit 
> Lombok-like from Java):
>
> @AutoConstructor
> class Person
> {
>   string name;
>   int age;
> }
>
> but I don't think it's doable in D right now.
>
> I am not looking for code, I can try that myself, just asking 
> if such things are possible?

Not sure about classes (I don't use them much) but structs have 
an automatically defined constructor. It is most definitely 
possible to do that with a mixin template (I remember someone 
recently showing autogenerating properties for readonly private 
members, sorry don't have a link).

The UDA approach won't work because they are there for 
reflection. You can generate code based on the presence (or 
absence) of a UDA but you can't synthesise new methods with that 
without forwarding from a wrapper.