Trait or builtin that returns arguments passed to current function (if any)

[Basile B.]

On Thursday, 9 September 2021 at 08:39:05 UTC, bauss wrote:
> [...]
> Here is a working example:
>
> ```d
> string __ARGUMENTS__(string fn = __FUNCTION__)()
> {
>     import std.traits : ParameterIdentifierTuple;
>     import std.array : join;
>
>     mixin("enum parameterNames = [ParameterIdentifierTuple!(" ~ 
> fn ~ ")];");
>
>     return "auto __arguments = [" ~ parameterNames.join(",") ~ 
> "];";
> }
>
> void test(int x, int y)
> {
>     import std.stdio;
>
>     mixin(__ARGUMENTS__);
>
>     auto c = __arguments[0];
>     auto d = __arguments[1];
>
>     writefln("%d %d", c, d);
> }
>
> void main()
> {
>     test(1,2);
> }
> ```
> Output:
> 1 2

Nice.

> But yeah it would be nice if we could have it built-in, which I 
> don't think has been done.

That's a contemporary D question that often comes in 
conversations: should "feature x" be a builtin or should "feature 
x" be made using metaprog...

Is this used often ? is the metaprog version slow ?