How to make a slow compile

[Andrey Zherikov]

On Sunday, 24 August 2025 at 18:21:50 UTC, monkyyy wrote:
> On Sunday, 24 August 2025 at 13:59:46 UTC, Andrey Zherikov 
> wrote:
>> On Wednesday, 20 August 2025 at 15:33:45 UTC, monkyyy wrote:
>>> once again dconf contains people who talk about compile speed 
>>> as if it can be slow
>>>
>>> What are they doing? Even my worse compile time abstraction 
>>> was O(n^2) or maybe some awful string concatenation of an 
>>> entire file; still effectively instant
>>>
>>> Wheres a 1000 line file that does something meta 
>>> programmingly useful that takes 5 minutes?
>>>
>>> Do they lose track of what the compiler is even doing? Do 
>>> they turn off the template recursion depth limit?
>>
>> My recent experience: removing usage of SumType and replacing 
>> it with my own solution reduced dmd memory usage from 6GB to 
>> 1.7GB and improved compilation speed.
>
> What sort of difference did you do? Did the memory usage matter 
> for speed at all?

I was speaking about [this 
change](https://github.com/andrey-zherikov/argparse/pull/214) 
where I replaced `std.SumType` with my own implementation using 
`union`.
So I got lower memory usage and faster compilation.