Small @nogc experience report

[Shachar Shemesh]

I've got plenty to say, but here is the long and the short of it: Use Mecca.

On 07/09/18 19:44, Peter Alexander wrote:
> 3. It was really frustrating that I had to make the compiler happy 
> before I was able to run anything again. Due to point #1 I had to move 
> code around to restructure things and wanted to make sure everything 
> continued working before all GC allocations were removed.

mecca.lib.reflection has "as".
https://weka-io.github.io/mecca/docs/mecca/lib/reflection/as.html

Here is how you use it:
void fun() @nogc {
   as!"@nogc"( some code that is not @nogc );
}

> 
> 4. I used std.algorithm.topNCopy, which is not @nogc. The error just 
> says "cannot call non- at nogc function [...]". I know there are efforts to 
> make Phobos more @nogc friendly, but seeing this error is like hitting a 
> brick wall. I wouldn't expect topNCopy to use GC, but as a user, what do 
> I do with the error? Having to dig into Phobos source is unpleasant. 
> Should I file a bug? What if it is intentionally not @nogc for some 
> subtle reason? Do I rewrite topNCopy?
> 
> 5. Sometimes I wanted to add writeln to my code to debug things, but 
> writeln is not @nogc, so I could not. I could have used printf in 
> hindsight, but was too frustrated to continue.

mecca.log has logging facilities that are @nogc.

Now, to be fair, they are not actually @nogc, as by default it uses 
writeln. It is, however, annotated with @nogc, for precisely the reasons 
you encountered.

Shachar