If I define a variable inside an outer function that generates a closure, this variable gets boxed inside the closer. Does this affect performance and if yes, how do I best avoid it?

Here is a simple MWE:

```
julia> function Adder(a)
ncalled = 0
function f(b)
ncalled += 1
@info "calling this adder for the $ncalled time"
return a + b
end
return f
end
julia> plus1 = Adder(1)
(::var"#adder#1"{Int64}) (generic function with 1 method)
julia> plus1.a
1
julia> plus1.ncalled
Core.Box(0)
```