extern mod extra;
use std::task::spawn_with;
use extra::comm::{SyncPort, SyncChan, rendezvous};
use std::iter::count;

fn generate(ch: SyncChan<int>) {
    for i in count(2, 1) {
        if !ch.try_send(i) {
            break;
        }
    }
}

fn filter(in_ch: SyncPort<int>, out_ch: SyncChan<int>, prime: int) {
    loop {
        let i = in_ch.recv();
        if i % prime != 0 {
            out_ch.send(i);
        }
    }
}

fn main() {
    let (port, chan) = rendezvous();

    let mut prev_port = port;

    do spawn_with(chan) |chan| {
        generate(chan);
    }

    loop {
        let prime = prev_port.recv();
        println!("{}", prime);

        let (new_port, new_chan) = rendezvous();

        do spawn_with((prev_port, new_chan)) |(prev_port, new_chan)| {
            filter(prev_port, new_chan, prime);
        }
        prev_port = new_port;
    }
}

extern mod extra;
use std::task::spawn;
use std::comm::{stream,Chan,Port};
use std::cell::Cell;

fn generate(ch: &Chan<int>) {
    let mut i = 2;
    loop {
        ch.send(i);
        i = i + 1;
    }
}

fn filter(in_ch: &Port<int>, out_ch: &Chan<int>, prime: int) {
    loop {
        let i = in_ch.recv();
        if i % prime != 0 {
            out_ch.send(i);
        }
    }
}

fn main() {
    let (port, chan) = stream();

    let mut prev_port = port;

    do spawn {
        generate(&chan);
    }

    loop {
        let prime = prev_port.recv();
        println!("{}", prime);

        let (new_port, new_chan) = stream();
        let prev_port_cell = Cell::new(prev_port);

        do spawn {
            filter(&prev_port_cell.take(), &new_chan, prime);
        }
        prev_port = new_port;
    }
}

--- 
+++ 
@@ -1,17 +1,17 @@
 extern mod extra;
-use std::task::spawn_with;
-use extra::comm::{SyncPort, SyncChan, rendezvous};
-use std::iter::count;
+use std::task::spawn;
+use std::comm::{stream,Chan,Port};
+use std::cell::Cell;
 
-fn generate(ch: SyncChan<int>) {
-    for i in count(2, 1) {
-        if !ch.try_send(i) {
-            break;
-        }
+fn generate(ch: &Chan<int>) {
+    let mut i = 2;
+    loop {
+        ch.send(i);
+        i = i + 1;
     }
 }
 
-fn filter(in_ch: SyncPort<int>, out_ch: SyncChan<int>, prime: int) {
+fn filter(in_ch: &Port<int>, out_ch: &Chan<int>, prime: int) {
     loop {
         let i = in_ch.recv();
         if i % prime != 0 {
@@ -21,22 +21,23 @@
 }
 
 fn main() {
-    let (port, chan) = rendezvous();
+    let (port, chan) = stream();
 
     let mut prev_port = port;
 
-    do spawn_with(chan) |chan| {
-        generate(chan);
+    do spawn {
+        generate(&chan);
     }
 
     loop {
         let prime = prev_port.recv();
         println!("{}", prime);
 
-        let (new_port, new_chan) = rendezvous();
+        let (new_port, new_chan) = stream();
+        let prev_port_cell = Cell::new(prev_port);
 
-        do spawn_with((prev_port, new_chan)) |(prev_port, new_chan)| {
-            filter(prev_port, new_chan, prime);
+        do spawn {
+            filter(&prev_port_cell.take(), &new_chan, prime);
         }
         prev_port = new_port;
     }
Implement most of the fixes from @tikue
