Lint/UnusedMethodArgument overriding reassignment and zsuper

[akhramov]

Per #4823 (comment) @mvz discovered an interesting case when overriding reassignment appears with zero-arity super call.

In this case, the value of a variable is unused, so cop suggests to rename the variable. But since super call is zsuper, it captures the reassigned variable:

def foo(a)
  a = 43

  super
end

The problem has been resolved by using non-zero arity super:

def foo(_a)
  super 43
end

That being said, reassignment is capured by zsuper, but original variable's value is not used.

What should we do in such situation? Suggest using super instead of zsuper? Add a configuration option to ignore this case? Both?

Update: binding call should have a similar problem.

[Drenmi]

I think we could augment the "unused argument" logic to tell if there's a call to super. In that case we consider it used. 🙂

[akhramov]

@Drenmi, i thought of that solution. My concern is that argument's value is unused. Is it a big deal?

[Drenmi]

@akhramov: Perhaps that is a new cop entirely? Lint/ShadowedArgument?

Something like:

Argument `a` was shadowed by a local variable before it was used.

WDYT?

[akhramov]

@Drenmi, agreed.

Should the cop have config options for disabling zsuper / binding cases? Like IgnoreBinding and IgnoreZeroAritySuper?

[mvz]

I solved my case by changing the zsuper to super with arguments. If that's the preferred syntax (and I tend to agree that it is), then the cops basically work and the only issue is documentation.