Proposal: throw error when unused parameter is present

[CyberReaper00]

this would be a really useful feature unlike unused variables which dont cause much damage to the codebase, but if there is an unused parameter then it has happened multiple times that i just created the function placed some stuff in there and tried to run the thing with some test data which worked fine and when i wanted to run with the actual data it didnt do what i wanted and i later realized that i forgot to replace my test data within the function with the function parameter

this is something that would actually be useful since a function should never be able to work without all of parameters being provided and also it would show that if the function is doing things that doesnt require those parameters anymore then i know that i need to remove them from the signature now and use the function differently

such as this

fn void f(int a)
{
    io::printn("this shouldnt be allowed");
}
fn int main()
{
    f(12);
    return 0;
}

[lerno]

It can be valid sometimes, consider for example a sorting function:

alias SortFn = fn int(void* a, void* b, void* context);

fn int sort_int(void* a, void* b, void* context)
{
  int av = *(int*)a;
  int bv = *(int*)b;
  if (a > b) return 1;
  return a < b ? -1 : 0;
}

In this case the unused parameter is quite normal.

[CyberReaper00]

i would argue that even though there is a situation where that may be necessary or give some convenience, there can be a simple workaround for the error by doing this (if it were implemented)

fn void f(int a, int b)
{
	(void)b;
	io::printfn("%s", a);
}

fn int main()
{
	f(12, 0);
	return 0;
}

for the functions where there is no need to use something, you can just get rid of it and circumvent the error for those specific functions while the safety net is kept for all other functions in the program

[lerno]

As an error I think this is unnecessary friction. As a warning, sure. An error would mean the compiler would be being an asshole when you're in mid development and I don't think that's very polite.

[CyberReaper00]

i see what you mean and i am perfectly happy with a warning

i have used a few languages over the past few years like go, odin etc and now that i think about it none of them have any warnings at all, i truly have not seen any warning in years from any compiler, it didnt even occur to me that this could just throw a warning instead of an error

as long as the compiler can tell me im missing something, im perfectly fine with that, i just want more information about my program

[lerno]

I added --warn-unusedlocal and --warn-unusedparam now. Note that to properly use this a @unused or @maybeunused attribute needs to be added as well.

[lerno]

Try it out.

[CyberReaper00]

im confused, i pulled in the latest code from the master branch and rebuilt the compiler but when i build a program it tells me that --warn-unusedparam is an unknown command, same with --warn-unusedlocal

also where am i supposed to use @unused in my program, is it supposed to be placed after the imports or in every single function declaration??

[lerno]

You're doing --warn-unusedlocal=yes? As I said @unused doesn't exist yet.

[CyberReaper00]

You're doing --warn-unusedlocal=yes?

nope i was just doing this, --warn-unusedlocal, it seemed intuitive to me that this would just be a simple boolean flag that would be false by default and i can just turn it on by just mentioning it, dont know why there was a need to provide a yes, it could just be interpreted as yes if it is mentioned

I added --warn-unusedlocal and --warn-unusedparam now. Note that to properly use this a @unused or @maybeunused attribute needs to be added as well.

i thought this meant that @unused needs to be added on my side in my program, not that you are telling me that this isnt added yet and I (lerno) will add this later 😂

also

• why is there a need for @unused when the flag is there?
• will these unused options be added to the project.json as well or will they remain flags?

[CyberReaper00]

i see why @unused is needed, but can you confirm @lerno
is it used so that the compiler doesnt go into every single import and check for unused items in there as well

so i can place the unused attribute as such
module main::space @unused
and then only that file will be checked for unused items and all other imports and files will be ignored