Questions on `scan` Intrinsic Implementation (For Fortran 2023 `split` procedure)

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Hi all,

I'm currently working on implementing the `split` procedure, which was 
added in Fortran 2023. Given its similar functionality to the `scan` 
intrinsic, I've been learning the implementation of `scan` to better 
understand its mechanics. During my investigation of the source code, 
I've come across a couple of questions that I'm hoping you could help me 
out:

* Function Resolution

I noticed that `scan` resolves to `gfc_get_string("__scan_%d", 
string->ts.kind)`. However, based on my examination of `libgfortran` and 
`trans-intrinsic.cc`, it appears this ultimately forwards to the 
`string_scan` function. Could you please explain the significance of 
this resolution step? Is it critical to the current implementation, or 
is it perhaps a remnant of historical design?

* Argument Passing

According to the Fortran specification, the `scan` intrinsic accepts 
arguments for `string`, `set`, `back`, and `kind`. Yet, the intrinsic 
implemented in `libgfortran` seems to take `charlen` and the actual 
pointers for both `string` and `set`. I've tried searching, but I 
haven't been able to pinpoint where this transformation from the 
specified arguments to the `libgfortran` expected arguments occurs. Any 
guidance on this would be greatly appreciated.

Thanks,
Yuao