D compiles fast, right? Right??

[Seb]

On Friday, 30 March 2018 at 20:40:16 UTC, Stefan Koch wrote:
> On Friday, 30 March 2018 at 20:17:39 UTC, Andrei Alexandrescu 
> wrote:
>> On 3/30/18 12:12 PM, Atila Neves wrote:
>>> Fast code fast, they said. It'll be fun, they said. Here's a 
>>> D file:
>>> 
>>>      import std.path;
>>> 
>>> 
>>> Yep, that's all there is to it. Let's compile it on my laptop:
>>> 
>>>      /tmp % time dmd -c  foo.d
>>>      dmd -c foo.d  0.12s user 0.02s system 98% cpu 0.139 total
>>
>> Could be faster.
>>
>>> That... doesn't seem too fast to me. But wait, there's more:
>>> 
>>>      /tmp % time dmd -c -unittest foo.d
>>>      dmd -c -unittest foo.d  0.46s user 0.06s system 99% cpu 
>>> 0.525 total
>>
>> Not fast. We need to make -unittest only affect the built 
>> module. Even though it breaks certain uses of 
>> __traits(getUnittests). No two ways about it. Who can work on 
>> that?
>>
>> Andrei
>
> unittests by nature usually have a short list of dependencies 
> and therefore their compilation can be parallelized.
> There are many performance leaks we can fix, before we need to 
> think about breaking useful features!

No one wants to run the std.regex's testsuite when they pass 
-unittest or instantiate and run all tests for all Tuple 
combinations present.
If you can make dmd so fast that this happens unnoticed, that 
would be amazing, otherwise I suggest we don't run Phobos's 
templated unittests in user-code.