Rust code that won't compile

gistfile1.rs

// This code works fine
fn get(f: ~fn() -> int) -> ~fn() -> int {
    || {
        f()
    }
}
fn main() {
    get(|| {8})();
}

// This code fails to compile with "error: moving out of captured outer variable in a heap closure"
// on "call(f)"
// I was thinking that the closure constructed by get() would get ownership of the closure f. I thought that it
// would then give up ownership of f when it invoked call(). However, my best guess is that the closure is unable to
// give up ownership for values its closing over? Is that correct or is something else going on here?
fn call(g: ~fn() -> int) -> int {
    g()
}
fn get(f: ~fn() -> int) -> ~fn() -> int {
    || {
        call(f)
    }
}
fn main() {
    get(|| {8})();
}

// I tried to rewrite call() to take a borrewed closure. This code compiles, but when run, it results in:
//
// exchange heap not empty on exit
// 1 dangling allocations
// Aborted (core dumped)
//
fn call(f: &fn() -> int) -> int {
    f()
}
fn get(f: ~fn() -> int) -> ~fn() -> int {
    || {
        call(f)
    }
}
fn main() {
    get(|| {8})();
}