Make shared static this() encoding table compilable

[Patrick Schluter]

On Monday, 14 March 2022 at 09:40:00 UTC, zhad3 wrote:
> Hey everyone, I am in need of some help. I have written this 
> Windows CP949 encoding table 
> https://github.com/zhad3/zencoding/blob/main/windows949/source/zencoding/windows949/table.d which is used to convert CP949 to UTF-16.
>
> After some research about how to initialize immutable 
> associative arrays people suggested using `shared static 
> this()`. So far this worked for me, but I recently discovered 
> that DMD cannot compile this in release mode with optimizations.
>
> `dub build --build=release`  or `dmd` with `-release -O` fails:
>
> ```
> code      windows949
> function  
> zencoding.windows949.fromWindows949!(immutable(ubyte)[]).fromWindows949
> code      table
> function  zencoding.windows949.table._sharedStaticCtor_L29_C1
> dmd failed with exit code -11.
> ```
>
> I usually compile my projects using LDC where this works fine, 
> but I don't want to force others to use LDC because of this one 
> problem.
>
> Hence I'd like to ask on how to change the code so that it 
> compiles on DMD in release mode (with optimizations). I thought 
> about having a computational algorithm instead of an encoding 
> table but sadly I could not find any references in that regard. 
> Apparently encoding tables seem to be the standard.

Why not use a simple static array (not an associative array). 
Where the values are indexed on `key - min(keys)`. Even with the 
holes in the keys (i.e. keys that do not have corresponding 
values) it will be smaller that the constructed associative 
array? The lookup is also faster.