• Piotr Szturmaj (3/3) Mar 29 2011 I see this is common practice in Phobos. I though static asserts should
• Jonathan M Davis (22/25) Mar 29 2011 If a static assert is in a unit test block it's to verify that something...
• bearophile (4/11) Mar 29 2011 Right. Some static asserts may cause/need the instantiation of a templat...
• Piotr Szturmaj (1/1) Mar 29 2011 Now it's clear. Thanks to both of you :)

Piotr Szturmaj <bncrbme jadamspam.pl> writes:

I see this is common practice in Phobos. I though static asserts should 
be checked at each compilation, not only when compiling with unittest. 
Or is it supposed to shorten compile time for already tested modules? :)

Jonathan M Davis <jmdavisProg gmx.com> writes:

On 2011-03-29 10:08, Piotr Szturmaj wrote:
 I see this is common practice in Phobos. I though static asserts should
 be checked at each compilation, not only when compiling with unittest.
 Or is it supposed to shorten compile time for already tested modules? :)

If a static assert is in a unit test block it's to verify that something 
works. You don't necessarily want it in normal code. For instance, what if the 
static assert is verifying something about a templated type or function? 
Having that static assert in the normal code would mean that that particular 
instantiation of the function would always be in the code, whereas putting the 
static assert in the unit test would only result in that instantiation during 
unit tests (unless you actually instantiated it in your code).

Whether static assert is used in normal code or a unit test depends entirely 
on what's being tested. A common place to use it in normal code would be with 
version blocks. e.g.

version(Posix)
{
}
else version(Windows)
{
}
else
	static assert(0, "Unknown OS version.");

static assert is a tool like any other and the best way to use it depends on 
what you're trying to do and what the situation is.

- Jonathan M Davis

bearophile <bearophileHUGS lycos.com> writes:

Jonathan M Davis:

 If a static assert is in a unit test block it's to verify that something 
 works. You don't necessarily want it in normal code. For instance, what if the 
 static assert is verifying something about a templated type or function? 
 Having that static assert in the normal code would mean that that particular 
 instantiation of the function would always be in the code, whereas putting the 
 static assert in the unit test would only result in that instantiation during 
 unit tests (unless you actually instantiated it in your code).

Right. Some static asserts may cause/need the instantiation of a template, that
burns both compile time and sometimes some space in the not so well stripped
binary. So putting those static asserts just inside the unittests is good.

Bye,
bearophile

Piotr Szturmaj <bncrbme jadamspam.pl> writes:

Now it's clear. Thanks to both of you :)