More accurate spans, season 2

[sanxiyn]

No description provided.

[sanxiyn]

Given

use core::comm;
fn f(_x: &[int]) {}
fn main() {
    f(~[0]);
}

Before:

x.rs:1 use core::comm;
       ^~~~~~~~~~~~~~~
x.rs:4     f(~[0]);
             ^~~~~

After:

x.rs:1 use core::comm;
           ^~~~~~~~~~
x.rs:4     f(~[0]);
             ^~~~