range - Warning: Cannot prove that 't' is initialized.

[opqx]

Hi.

Why do I receive a warning? I can not use positive numbers? 
    
    
    var t: range[5..10]  # Warning: Cannot prove that 't' is initialized. This 
will become a compile time error in the future. [ProveInit]
    var t: range[0..10]  # no warning
    var t: range[-1..10]  # no warning
    var t: range[-5..10]  # no warning