finding errors with templates without instantiating them

[bearophile]

Tudor Andrei Cristian Alexandrescu:

> I'm not against it, but I find it a very small improvement. Its 
> user base is exactly people who want to write and deploy a 
> template without ever testing it at all, ever. I have a hard 
> time catering to that hypothetical crowd.

This is an interesting discussion topic.

Mistakes and bugs are mechanically caught at several different 
moments, sometimes even before compile-time, thanks to squiggly 
red lines shown by the IDEs where there's a syntax error. Then 
bugs are found during compilations, by contracts and unittests at 
run-time, etc.

If you have a significant amount of template code already 
written, with unittests, etc, then the small amount of bugs 
spotted by this enhancement request is not much significant, 
because at that stage of the development of the code you are 
supposed to catch the remaining bugs using a high coverage ratio 
of unittests, etc. So in this case I agree with you this feature 
is not much useful, or it could even be harmful if programmers 
trust it too much.

But there is a another situation, when you don't have much new 
code written. You have just written 5-15 lines of templated code, 
and you have not yet written unittests on it (I write lot of 
unittests, but usually after writing the code), at this early 
stage I think it's useful to have a D compiler that performs 
simple analysis of the template code, to catch the simple 
mistakes very quickly. This helps me focus on the less obvious 
errors, and then I can write the unittests to catch the semantic 
mistakes of the code.

So I think this feature is not useful the seasoned code you seem 
to refer to; it's useful to catch as soon as possible silly 
mistakes inside just written templated code, that allows the 
programmer to focus on the less obvious bugs and on writing the 
unittests with high coverage.

Bye,
bearophile