`no-unused-expressions` has no way to warn on `void foo`

What version are you using? latest

What did you do? enabled no-unused-expressions, and expected void String; to be an error.

What happened? It was not an error.

What did you expect to happen? An error.

Looking at the exceptions in the docs, new C makes sense because constructors can have side effects (as could any function invocation or property access); delete a.b makes sense because delete has an effect; assignment makes sense. However, while some people might want void a to be used, that statement has no actual effect, and I’d like to be able to warn against it.

Could we add an option?

[taion]

BTW, this came up in the context of my wanting to find a way to mark variables as intentionally unused to avoid having to enable ignoreRestSiblings for no-unused. My intended pattern was:

const { foo, bar, ...rest } = whatever;
void bar;

But actually this is an ugly pattern and I’m not going to use it.

[not-an-aardvark]

You’re right, it seems like this was intentional – it was introduced in https://github.com/eslint/eslint/commit/928b6aeb1d499628212b44b486cca3557e53bc35 as a fix for https://github.com/eslint/eslint/issues/431.

I don’t really agree with the reasoning in that issue – it seems like void is being used to work around the no-new rule, but a disable comment would probably be a better way to do that because the use of void doesn’t really make sense here. However, if we do fix this by default it would be a breaking change.