HashMap.clear() leads to VacantEntry.set() asserting

[frankmcsherry]

The following code causes a panic in set(i) ('assertion failed: probe.index() != idx_end'). The current belief is that clear() causes the underlying array to shrink below tested levels (being fixed independently), at which point a corner case may show up in insertion.

use std::collections::HashMap;
use std::collections::hash_map::Vacant;

fn main()
{
    let mut m = HashMap::with_capacity(4); 

    m.clear(); 

    for i in range(0u, 4) 
    { 
        match m.entry(i) 
        { 
            Vacant(x) => { x.set(i); }, 
            _ => {}, 
        } 
    }
}

[cgaebel]

I'm working on this right now.

[frankmcsherry]

This example now seems to work great with recently landed changes. Thanks!