Unused variables, better as error or warning?

[Leandro Lucarella]

dsimcha, el 20 de agosto a las 13:42 me escribiste:
> == Quote from bearophile (bearophileHUGS at lycos.com)'s article
> > A small Reddit thread regarding if unused variables and imports are better as
> errors or warnings:
> > http://www.reddit.com/r/programming/comments/d3emo
> > In my opinion in this case errors are too much, warning are enough.
> > Few situations for those warnings:
> > - warning for unused variables (as GC, C# and other compilers do);
> > - warning when a variable get used in some ways, and then its last assignment
> gets unused (done by a kind of C compiler);
> > - unused imports (useful to keep code clean and remove unnecessary module
> dependences);
> > - unused functions (but this is harder to do in a clean way in a language that
> has templates, so this may be omitted).
> > Among those four warnings the most useful are the first two ones. In C once the
> unused variable warning of GCC has found at compile time a bug in my code (I did
> forget to increment that variable in the loop). So I have loved this warning ever
> since.
> > Bye,
> > bearophile
> 
> If we make unused imports an error, how is anyone supposed to do import
> someSmallLibrary.all?  If you make unused imports an error, the collective cost of
> extra import declaration boilerplate will probably be larger than the GDP of some
> African countries.

I never understood this argument against flagging errors/warnings on
unused imports.

lib/a.d:
void f() {}

lib/all.d:
public:
import lib.a;
import lib.b;
import lib.c;

unused.d:
void g() {}

user.d:
import lib.all;
import unused;
f();

import lib.all should never flag an error/warning, because at least one
symbol in lib.all is used. Public imports are treated as if they were
declared in the module that imports them. import unused should flag an
error/warning, since no symbol in unused is used by user.d.

Do you see any problem with that?

-- 
Leandro Lucarella (AKA luca)                     http://llucax.com.ar/
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