[GSoC 2025] Templated Hooks - Weekly Update #3

[AlbertG]

This week I've worked on 
[`_d_interface_cast`](https://github.com/dlang/dmd/pull/21473). I 
had to deal with some situations when implicit casts where made, 
but they were not lowered correctly. I narrowed down the issue to 
some code in `expressionsem.d` that created a new `CastExp` but 
did not perform the expression semantic analysis on it (where the 
lowering happens). There are still some failing tests I need to 
figure out, but it should be mostly done.

Apart from that, I have also run some benchmarks on the already 
templated casting hooks. Not surprisingly, the results show 
mostly on-par performance with the old versions, but in some 
cases the templated versions perform worse. I described more 
about this in a separate [forum 
post](https://forum.dlang.org/post/ddoglzglkylgnjgnwtvd@forum.dlang.org).