Warn on unused imports?

[Olivier FAURE]

On Wednesday, 26 September 2018 at 09:25:11 UTC, Jonathan M Davis 
wrote:
> It's just a message. You can use a compiler flag to make the 
> message go away or to turn it into an error (though in general, 
> I'd advise against it, since then your code breaks as soon as 
> something gets deprecated), but by default, they're just 
> messages.

That's precisely what warnings are: messages that can be silenced 
or turned into errors. When people talk about warnings, that's 
usually what they mean.

Personally speaking, I like to treat warnings as problems that 
don't stop your code from compiling during development (eg I 
don't want to worry about my extranous return statements when I'm 
doing quick experiments), but can't be accepted upstream, and 
have to trigger errors in CI.

But with a robust warning system, other approaches are possible.

> Unfortunately, if your build spits out a bunch of status stuff 
> instead of just printing out actual problems, deprecation 
> messages do sometimes get missed

Warnings often catch real problems, even categories of warnings 
with high amounts of false positives like unused variables.

But yeah, I get your point. Warning lose their interest when they 
start to pile up in your codebase to the point it's impossible to 
notice new ones, and it's impossible to turn them into errors 
because there's already too many.

That said, that's a problem with D compilers, not with the 
concept of warnings. You mention that deprecations warnings are 
nice because they can be turned off; ideally, all categories of 
warnings should be like that.

What DMD and GDC lack (I think) is GCC's level of granularity, 
with flags like

     -Wnonnull
     -Werror=missing-attributes
     -Wno-error=misleading-indentation

But that doesn't mean the concept of compiler warnings needs to 
be thrown away.