extra_positional_arguments triggers only once

[FMorschel]

Repro:

void f() {}

void main() {
  f(1); // extra_positional_arguments
  f(1, 2); // extra_positional_arguments, nothing
}

I'd say that 2 should also trigger this diagnostic.

CC @bwilkerson

[bwilkerson]

My first reaction was that the message is fairly clear about there being one or more extra positional arguments and that it wouldn't add any value to the user to have two diagnostics.

However, as I thought about it I realized that the current diagnostic doesn't work as well if there are named arguments between positional arguments. It might well be better to change the diagnostic to be singular and to report each unmatched argument separately.

The biggest remaining reason that I can think of to not do this is that it would be more work for the user to apply the "convert positional arguments to named arguments" fix. If they're separate diagnostics then we'd need the fix to fix a single argument. This isn't a heavily used fix, so it's possible that this wouldn't inconvenience too many users, but it would impact some users. Maybe they could offer some insight.