String keys in HashMap are practically impossible

[Aatch]

type StringMap<T> = HashMap<~str, T>; //Fairly common

fn foo(map:&mut StringMap<uint>) {
  map.insert("Test".to_str(), 1); // This works fine, copying the string isn't unexpected
  map.find("Test"); //Nope. its a &'static str, not a ~str, so the types don't match, the only work around is copying the string
}

Copying the string in order to do a lookup is plain ridiculous. It adds significant overhead where it isn't needed. Now, I'm not sure how to fix it, but this is a common enough case that it should be dealt with.

Related to #3284 - probably.

[thestinger]

You can use the find_equiv method to do a lookup with &str in a HashMap with ~str keys. This same issue exists in C++ with the standard containers, but there's no workaround like find_equiv.