setter syntax should probably be restricted to always return undefined

[emilio]

What is the issue with the Web IDL Standard?

See w3c/css-houdini-drafts#1142 for an example where return values are used, but probably shouldn't be.

I don't think there's any reasonable behavior if you were to specify a setter to return anything that wasn't the right hand side of the input. Right now implementations all ignore the return value.

Is there any reason something other than undefined is allowed in a setter operation?

[emilio]

cc @janvarga @saschanaz @EdgarChen

[annevk]

I wonder if @dontcallmedom has a hidden setting for https://dontcallmedom.github.io/webidlpedia/ so we can find other problematic specifications.

This also goes for deleters.

I suppose in theory if you called the method but not the setter it could return something, but that still seems wrong so forbidding it altogether would be best I think.

[saschanaz]

Is there any reason something other than undefined is allowed in a setter operation?

SpecialOperation probably made more sense when there were more things that actually returned something, but given it's only the getter returning something now, time to break down this syntax.