Troubles with types, iterators and collections

iter_stuff.rs

fn main() {

    // Match parsed group lengths with expected - test data
    let group_lengths: ~[(&int, &int)] = ~[(&8, &8), (&4, &4), (&4, &4), (&4, &4), (&8, &12)];

    // ~~~
    // ~~~ Problem 1: all vs take_while and unpacking tuple
    // ~~~

    // This works
    let glm = group_lengths.iter().all(|&(&a, &b)| a == b);

    // But this doesn't
//    let glm = group_lengths.iter().take_while(|&(&a, &b)| a == b);
    // error: mismatched types: expected `&(&uint,&uint)` but found tuple (types differ)

    // Had to change to this
    let glm = group_lengths.iter().take_while(|&v| v.first() != v.second());

    // Question: why can Rust unpack the tuple for all() but not take_while() ?

    // ~~~
    // ~~~ Problem 2: collect and types
    // ~~~

    // So we have a valid iterator, we just want to collect into a vector.
    // The type of the vector is known as it should match group_lengths
    // since take_while() has to return elements from group_lengths.

    // Just add collect? No, this fails:
    let glm = group_lengths.iter().take_while(|&v| v.first() != v.second()).collect();
    // error: cannot determine a type for this bounded type parameter: unconstrained type

    // Ok so we add a type, same as group_lengths
    let glm: ~[(&int, &int)] = group_lengths.iter().take_while(|&v| v.first() != v.second()).collect();
    // error: expected std::iterator::FromIterator<&(&int,&int),std::iterator::TakeWhile<,&(&int,&int),std::vec::VecIterator<,(&int,&int)>>>,
    //     but found std::iterator::FromIterator<(&int,&int),<V2943>> (expected &-ptr but found tuple)
    // error: cannot determine a type for this bounded type parameter: unconstrained type

    // Try all sorts of crazy combinations and end up with this still not working...
    let glm: ~[(&int, &int)] = group_lengths.iter().take_while(|&v| v.first() != v.second()).collect::<~[&(&int, &int)]>();
    // error: mismatched types: expected `~[(&int,&int)]` but found `~[&(&int,&int)]` (expected tuple but found &-ptr)

    // Question: how can we collect the results from an iterator with the type vector of tuples?
}