Hello :wave:, Is there a way to limit access of a block of code to only within a scope? For example,...

# announcements

[aerb]

Hello 👋, Is there a way to limit access of a block of code to only within a scope? For example, could I somehow have a lambda where assignments outside of scope are not allowed?

[karelpeeters]

You want something like fun foo(block: (Int) -> Int) where block isn't allowed to access stuff from the scope where it was defined? I don't think that's possible.

[aerb]

Yes!

[aerb]

I think this is loosely similar to @DslMarker

[aerb]

Could be a very useful feature for limiting side effects

[aerb]

Worth bringing up in #C0B9K7EP2 ?

[karelpeeters]

Maybe, although it's difficult to determine what a side effect is. You wouldn't be able to call any functions at all, or use any libraries.

[aerb]

I'm not really interested in a pure FP side effect free guarantee. More a simple check where if you assign a variable outside of the lambda scope you'll get a compiler error.

[Pavlo Liapota]

I guess you want to force lambda to be non-capturing, right?

[aerb]

Not necessarily non capturing. But you are not allowed to assign outside of your scope. I think if it is being executed on a different thread this could be a useful protective feature.