Construction from generator may iterate a second time

[yha]

For example, this:

expensive_function(k) = (println(k); k > 2 && error("too large!"))
b = OrderedDict(k => expensive_function(k) for k in 1:3)

prints

1       
2
3
1
2
3
ERROR: too large!

(stack trace omitted)

The constructor shouldn't call my expensive_function again on previous elements.
This seems also to affect some (all?) other structures in DataStructures.jl.