Error using Bound()

[Lan238692]

I think I can't use the Bound function as mentioned in the guide below.

let bound = Bound([U, V]);
bound(x);

The following error message is shown.

Couldn't match type (Qubit => Unit is Adj + Ctl) with type ('m => Unit).
Expected: ('m => Unit)[]
Actual: (Qubit => Unit is Adj + Ctl)[]