Error quality of life: Forgetting to assign a ?? expression leads to a suprising error?

[joshring]

Not sure about this one, but I'll see what you think:

module faults;
fault
    EXAMPLE,
    DOG_ATE_MY_HOMEWORK,
    MY_TEXTBOOK_CAUGHT_FIRE,
    DISTRACTED_BY_CAT_PICTURES;


module testing_v0_7;
import faults;
import std::io;

fn int main(String[] args)
{

	int? foo = faults::EXAMPLE?;

	if (catch foo)
	{
		// Error: An optional value may not be discarded, you can ignore it with a void cast '(void)', rethrow on optional with '!' or panic '!!' to avoid this error.
		foo ?? faults::DISTRACTED_BY_CAT_PICTURES?;
		io::printfn("foo = %s", foo)!!;
	}

	return 0;
}

[lerno]

No this is correct. This is most surely a bug.

[lerno]

It's also not clear what the user intended:

foo = foo ?? faults::FOO?;
// or
foo ?? faults::FOO?!;

[joshring]

It's also not clear what the user intended:

foo = foo ?? faults::FOO?;
// or
foo ?? faults::FOO?!;

I think this is the perfect error message

[lerno]

This is a general check on discards though, how would you detect and make a reasonable error message?

[joshring]

Check if the optional was not assigned to a value or rethrown or panic. In that instance would adjust the error to mention:

"Error: An optional value was discarded, you can assign it to a variable, ignore it with a void cast '(void)', rethrow on optional with '!' or panic '!!' to avoid this error."

[lerno]

I've updated it now, see if it's better.

[joshring]

Looks great, gives a nice nudge to the solution 👍