Feature. That kind of magical backpropagation is rare in LV but a few nodes have implemented it. There's a lot of internal debate about how good an idea it is. Myself, I would rather the type terminal be a required input.
I don't know why people are hacking around on the poor old unsigned integers. They're a positive lot and never have anything ngative to say about anyone.
Having a closer look at the "scan varian from string" I noticed that the strings atre threated as in the picture attached. I think a possible solution to solve my problem is to remove the "scan from string" and put the Input string directly to the variant output.
But I am sure the generality of the vi in this case would be compromised.