Resources in Closures

Resources can not be captured in closures, as that could potentially result in duplications.

resource R {}

// Invalid: Declare a function which returns a closure which refers to
// the resource parameter `resource`. Each call to the returned function
// would return the resource, which should not be possible.
//
fun makeCloner(resource: @R): ((): @R) {
    return fun (): @R {
        return <-resource
    }
}

let test = makeCloner(resource: <-create R())