[SAoC 2021] Replace druntime Hooks with Templates: Milestone 4, Week 1

[max haughton]

On Friday, 24 December 2021 at 18:59:07 UTC, Teodor Dutu wrote:
> Hi,
>
> This milestone I am planning to finish replacing the hooks to 
> `_d_arrayappend{T,cTX}` with templates. This week I almost 
> finished this task.
> There is still a bug when inlining a function such as:
> ```d
> int[] arr;
> void foo()
> {
> 	(arr ~= 2) ~= 1;
> }
> ```
> The first concatenation causes an `ArrayIndexError` because the 
> location of the array length is incorrectly referred in the 
> resulting executable. I am yet to find the source of this 
> error. I dissected inline.d, and the oddresulting statement 
> looks alright.
>
> After this, I plan to convert `_d_newThrowable` and 
> `_d_newitem{U,iT,T}` to templates. I started working on 
> `_d_newThrowable`, but I'm having trouble recreating [these 
> `assert`s](https://github.com/dlang/druntime/blob/fd9a45448244fb9dd4326520ad8526c540895eb0/src/rt/ehalloc.d#L35-L36) as the template doesn't store those flags.
>
> Merry Christmas!
>
> Thanks,
> Teodor

The frontend inliner leads to such strange issues that I think we 
should delete it and use something in the backend instead. As far 
as I'm aware Walter has one in DMC, but it doesn't have a 
heuristic so it's only if you ask for inlining explicitly.