Can iterators not be variables?

[emre]

Why does this fail?
    
    
    var input = "ABCDEFGABF".items
    for c in input:
     echo c
    
    Run

> Error: undeclared field: 'items' for type system.string

whereas this passes?
    
    
    var input = "ABCDEFGABF"
    for c in input.items:
     echo c
    
    Run