Incorrect loan error when local borrowed variable is updated to new loan

[lifthrasiir]

The following code...

fn main() {
    let s: ~str = ~"foobar";
    let mut t: &str = s;
    t = t.slice(0, 3); // for master: str::view(t, 0, 3) maybe
}

...results in the following error:

t.rs:4:4: 4:5 error: assigning to mutable local variable prohibited due to outstanding loan
t.rs:4     t = t.slice(0, 3);
           ^
t.rs:4:8: 4:9 note: loan of mutable local variable granted here
t.rs:4     t = t.slice(0, 3);
               ^

Both t and t.slice(0, 3) are loans of s, so it should be safe to update t to new loan of s as updating t doesn't cause s to be freed.

[catamorphism]

This works now; I'll check in the test case.

[catamorphism]

Test case checked in in 9a06ff0. Closing