How about Go's... error on unused imports?

[Clay Smith]

Bill Baxter wrote:
> On Fri, Nov 13, 2009 at 10:23 AM, Clay Smith <clay.smith.r at gmail.com> wrote:
>> Clay Smith wrote:
>>> Bill Baxter wrote:
>>>> On Fri, Nov 13, 2009 at 9:51 AM, Clay Smith <clay.smith.r at gmail.com>
>>>> wrote:
>>>>> Leandro Lucarella wrote:
>>>>>> I'm sorry to bring up another "How about Go's ..." topic, but I think
>>>>>> this
>>>>>> feature is very in sync with D and it should be really easy to
>>>>>> implement.
>>>>>>
>>>>>> Go issues an error if you have an import that's never used, to avoid
>>>>>> unnecessary dependencies.
>>>>>>
>>>>>> Do you see any reasons not to do that? I think it happens very often to
>>>>>> stop using some import and never notice it.
>>>>>>
>>>>> No, this is a job to be left to the IDE, not compiler.
>>>> Well, just a small argument for the contrary, but you may be importing
>>>> some module precisely for the purpose of getting its module
>>>> constructors to run.  For instance the module constructor may have a
>>>> call like RegisterComponent(thisModule) in it.  Think of a set of
>>>> image format loaders that register themselves with the main
>>>> ImageLoader module.  Then you call ImageLoader.load(filename).
>>>> Nowhere in your code do you care if it is a PNG or not.  You only need
>>>> to use the ImageLoader's API.
>>>>
>>>> Also there's public imports.  And all.d type modules with nothing but
>>>> pubilic imports.
>>>>
>>>> There's no way an IDE can know about those intents.  So that argues
>>>> that there should be a way in the language to indicate "i know it
>>>> doesn't look like I'm using this, but I am".   And if that's in the
>>>> language then the compiler might as well do the checking, too.
>>>>
>>>> Ok, not a super strong argument... unless D changed to compile things
>>>> the way Go does, rolling in all deps.
>>>>
>>>> How about that one from Go?  Including all deps in an obj.  Could D
>>>> use the same trick to speed up compilation further?
>>>>
>>>> --bb
>>> I'm not really understanding what you are saying,
> 
> 
> It's not that complicated.  Maybe try reading it again.  And forget
> about the example of why you might want to import something without
> using it, just trust that there are legit cases where you might want
> to.

ok

> 
>>> but I see no need for
>>> the compiler to error on unused import. If anything, the compiler can just
>>> ignore it, or have a flag to find unused imports. I would like my all.d
>>> files to not give errors :o
> 
> Actually, I agree that the compiler should not error unused *public*
> imports.  That really would not make any sense.

True


> 
>> Plus copy/paste imports from other modules, without compile error :o
> 
> Why do you want to paste in a bunch of unused imports?   Wouldn't you
> like to know which ones you use and which you don't, and trim the fat?
> 
> --bb

If I want to save time, and I'm developing a module similar to an 
existing one, copying/pasting imports is 90% accurate and saves me time, 
which is invaluable.