using this instead of typeof(this)

[Maxim Fomin]

On Tuesday, 26 February 2013 at 16:28:59 UTC, Ivan Kazmenko wrote:
> Hi!
>
> I have recently experimented with ways to express the exact 
> instantiated type of a generic struct, and found that I can in 
> some cases use "this" as that type.
>

1) D allows omitting parameter names in function definitions 
which are replaced by implicitly created _param_XXX.

2) This as a type in parameter list replaces type of this.

What you observe is consequence of combination of this rules. The 
most unintuitive is that applying attribute to postblit 
declaration makes it a regular constructor which takes argument 
of that struct type.

>
> And so I wonder:
>
> (1) Should I refrain from using this as a type, is it a bug?

Better to avoid such usage.

> (2) A matter of style: what is the idiomatic way to take the 
> exact type of a templated struct? For example, which method 
> signature to return a typeof(this) value is "better" in which 
> way if all have the same effect:
> -----
> struct S (A, B, C)
> {
> ...
> 	auto method () {...}
> 	S method () {...}
> 	S !(theA, theB, theC) method () {...}
> 	typeof (this) method () {...}
> }
> -----
> Note that S, theA, theB and theC can get lengthy.

You can use template this parameter in templates and avoid in 
non-templates.

> (3) Is the usage of unnamed parameters and _param_### a 
> language feature or an implementation-specific detail I should 
> not ever use?
>
> -----
> Ivan Kazmenko.

It is implementation-specific detail.