Problem with @safe

[Atila Neves]

I just spent a lot of time trying to debug my code and it seems 
to have to do with @safe. I have some template functions in a 
class, and one of them, marked as @safe, ended up making a call 
to an abstract function with no attribute. My unit test started 
failing and I tried writeln-debugging but now my function never 
seemed to get called.

I tried gdb but the code jumped around weirdly (even though it 
was a debug build) and some stack frame information was off so I 
didn't trust it.

But stepping through the code gave me the idea to put writelns 
earlier in the call stack, and as I did so I ran into a compiler 
error I hadn't gotten before: @safe functions can't call writeln. 
"Fair enough", I said, and ended up with a chain of functions 
that had to be changed.

And then my code worked again. So I removed the writelns, changed 
everything to @trusted, and... the code worked again. I narrowed 
the fix down to this:

https://github.com/atilaneves/cerealed/commit/09d278638394185339a6115e7093b8aab2fac480

So, because an abstract function wasn't @safe, the compiler 
emitted code to... I'm not quite sure to do what. All I know is 
it didn't call the right function.

Is there something about @safe, @trusted, etc. that causes the 
compiler to disregard template functions from instantiation??

The worst part of all this is the compiler said not one thing. 
And it took a while to track down. I nearly wish I hadn't 
bothered with @safe and friends!

Atila