Swift optional chaining doesn't work in closure

Question

My code looks like this. My class has an optional var

var currentBottle : BottleLayer?

BottleLayer has a method jiggle().

Answer 1

Letting the closure type be inferred seems to work as well.

let clos2 = { currentBottle?.jiggle() }
clos2() // does a jiggle

But I'm pretty sure this is just the compiler assigning a type of () -> ()?