fix fallout

31 files changed, 118 insertions, 43 deletions

diff --git a/src/doc/trpl/unsafe.md b/src/doc/trpl/unsafe.md
index 3acd1eefe89..2bd86fa987f 100644
--- a/src/doc/trpl/unsafe.md
+++ b/src/doc/trpl/unsafe.md
@@ -576,6 +576,10 @@ extern fn panic_fmt(args: &core::fmt::Arguments,
 #[lang = "eh_personality"] extern fn eh_personality() {}
 # #[start] fn start(argc: isize, argv: *const *const u8) -> isize { 0 }
 # fn main() {}
+# mod std {  // for-loops
+#     pub use core::iter;
+#     pub use core::option;
+# }
 ```
 
 Note that there is one extra lang item here which differs from the examples
diff --git a/src/libcollections/bit.rs b/src/libcollections/bit.rs
index d676cfca929..99172dcdef3 100644
--- a/src/libcollections/bit.rs
+++ b/src/libcollections/bit.rs
@@ -104,7 +104,9 @@ type MatchWords<'a> = Chain<Enumerate<Blocks<'a>>, Skip<Take<Enumerate<Repeat<u3
 
 fn reverse_bits(byte: u8) -> u8 {
     let mut result = 0;
-    for i in 0..u8::BITS {
+    // FIXME(#21245) use a for loop
+    let mut iter = 0..u8::BITS;
+    while let Some(i) = iter.next() {
         result |= ((byte >> i) & 1) << (u8::BITS - 1 - i);
     }
     result
diff --git a/src/libcollections/btree/node.rs b/src/libcollections/btree/node.rs
index ea167348a64..8d6f06b25c5 100644
--- a/src/libcollections/btree/node.rs
+++ b/src/libcollections/btree/node.rs
@@ -271,7 +271,7 @@ impl<T> DoubleEndedIterator for RawItems<T> {
 #[unsafe_destructor]
 impl<T> Drop for RawItems<T> {
     fn drop(&mut self) {
-        for _ in *self {}
+        for _ in self.by_ref() {}
     }
 }
 
@@ -1374,9 +1374,9 @@ impl<K, V> Drop for MoveTraversalImpl<K, V> {
     fn drop(&mut self) {
         // We need to cleanup the stored values manually, as the RawItems destructor would run
         // after our deallocation.
-        for _ in self.keys {}
-        for _ in self.vals {}
-        for _ in self.edges {}
+        for _ in self.keys.by_ref() {}
+        for _ in self.vals.by_ref() {}
+        for _ in self.edges.by_ref() {}
 
         let (alignment, size) =
                 calculate_allocation_generic::<K, V>(self.capacity, self.is_leaf);
diff --git a/src/libcollections/lib.rs b/src/libcollections/lib.rs
index 82b92d26d28..f28262dc0fe 100644
--- a/src/libcollections/lib.rs
+++ b/src/libcollections/lib.rs
@@ -34,6 +34,8 @@
 #![feature(unicode)]
 #![feature(hash)]
 #![cfg_attr(test, feature(test))]
+// NOTE(stage0): remove after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 #[macro_use]
 extern crate core;
@@ -114,6 +116,8 @@ mod std {
     pub use core::marker;   // derive(Copy)
     pub use core::hash;     // derive(Hash)
     pub use core::ops;      // RangeFull
+    // for-loops
+    pub use core::iter;
 }
 
 #[cfg(test)]
diff --git a/src/libcollections/ring_buf.rs b/src/libcollections/ring_buf.rs
index 5b5e3be12e3..a9b31da8250 100644
--- a/src/libcollections/ring_buf.rs
+++ b/src/libcollections/ring_buf.rs
@@ -1510,7 +1510,7 @@ pub struct Drain<'a, T: 'a> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T: 'a> Drop for Drain<'a, T> {
     fn drop(&mut self) {
-        for _ in *self {}
+        for _ in self.by_ref() {}
         self.inner.head = 0;
         self.inner.tail = 0;
     }
@@ -1793,7 +1793,9 @@ mod tests {
     fn bench_push_back_100(b: &mut test::Bencher) {
         let mut deq = RingBuf::with_capacity(101);
         b.iter(|| {
-            for i in 0i..100 {
+            // FIXME(#21245) use a for loop
+            let mut iter = 0i..100;
+            while let Some(i) = iter.next() {
                 deq.push_back(i);
             }
             deq.head = 0;
@@ -1805,7 +1807,9 @@ mod tests {
     fn bench_push_front_100(b: &mut test::Bencher) {
         let mut deq = RingBuf::with_capacity(101);
         b.iter(|| {
-            for i in 0i..100 {
+            // FIXME(#21245) use a for loop
+            let mut iter = 0i..100;
+            while let Some(i) = iter.next() {
                 deq.push_front(i);
             }
             deq.head = 0;
diff --git a/src/libcollections/slice.rs b/src/libcollections/slice.rs
index 56d969b8946..57ee4704a9e 100644
--- a/src/libcollections/slice.rs
+++ b/src/libcollections/slice.rs
@@ -1958,7 +1958,7 @@ mod tests {
             let mut amt = 0;
             let mut it = v.permutations();
             let (min_size, max_opt) = it.size_hint();
-            for _perm in it {
+            for _perm in it.by_ref() {
                 amt += 1;
             }
             assert_eq!(amt, it.swaps.swaps_made);
diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index 35591a5e9ef..bbed943fc70 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -279,7 +279,7 @@ impl<'a> Iterator for Recompositions<'a> {
         loop {
             match self.state {
                 Composing => {
-                    for ch in self.iter {
+                    for ch in self.iter.by_ref() {
                         let ch_class = unicode::char::canonical_combining_class(ch);
                         if self.composee.is_none() {
                             if ch_class != 0 {
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index ac6d7936f28..4ea8267135f 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -1567,7 +1567,9 @@ impl<T> Drop for Vec<T> {
         // zeroed (when moving out, because of #[unsafe_no_drop_flag]).
         if self.cap != 0 {
             unsafe {
-                for x in self.iter() {
+                // FIXME(#21245) use a for loop
+                let mut iter = self.iter();
+                while let Some(x) = iter.next() {
                     ptr::read(x);
                 }
                 dealloc(*self.ptr, self.cap)
@@ -1648,7 +1650,7 @@ impl<T> IntoIter<T> {
     #[unstable(feature = "collections")]
     pub fn into_inner(mut self) -> Vec<T> {
         unsafe {
-            for _x in self { }
+            for _x in self.by_ref() { }
             let IntoIter { allocation, cap, ptr: _ptr, end: _end } = self;
             mem::forget(self);
             Vec { ptr: NonZero::new(allocation), cap: cap, len: 0 }
@@ -1726,7 +1728,7 @@ impl<T> Drop for IntoIter<T> {
     fn drop(&mut self) {
         // destroy the remaining elements
         if self.cap != 0 {
-            for _x in *self {}
+            for _x in self.by_ref() {}
             unsafe {
                 dealloc(self.allocation, self.cap);
             }
@@ -1816,7 +1818,7 @@ impl<'a, T> Drop for Drain<'a, T> {
         // so we can use #[unsafe_no_drop_flag].
 
         // destroy the remaining elements
-        for _x in *self {}
+        for _x in self.by_ref() {}
     }
 }
 
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index f9c6e0758e6..7847ed13ca9 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -195,7 +195,7 @@ pub trait IteratorExt: Iterator + Sized {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
-        for x in *self {
+        for x in self.by_ref() {
             if n == 0 { return Some(x) }
             n -= 1;
         }
@@ -492,7 +492,7 @@ pub trait IteratorExt: Iterator + Sized {
     /// fn process<U: Iterator<Item=isize>>(it: U) -> isize {
     ///     let mut it = it.fuse();
     ///     let mut sum = 0;
-    ///     for x in it {
+    ///     for x in it.by_ref() {
     ///         if x > 5 {
     ///             break;
     ///         }
@@ -660,7 +660,7 @@ pub trait IteratorExt: Iterator + Sized {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn any<F>(&mut self, mut f: F) -> bool where F: FnMut(Self::Item) -> bool {
-        for x in *self { if f(x) { return true; } }
+        for x in self.by_ref() { if f(x) { return true; } }
         false
     }
 
@@ -680,7 +680,7 @@ pub trait IteratorExt: Iterator + Sized {
     fn find<P>(&mut self, mut predicate: P) -> Option<Self::Item> where
         P: FnMut(&Self::Item) -> bool,
     {
-        for x in *self {
+        for x in self.by_ref() {
             if predicate(&x) { return Some(x) }
         }
         None
@@ -703,7 +703,7 @@ pub trait IteratorExt: Iterator + Sized {
         P: FnMut(Self::Item) -> bool,
     {
         let mut i = 0;
-        for x in *self {
+        for x in self.by_ref() {
             if predicate(x) {
                 return Some(i);
             }
@@ -1664,7 +1664,7 @@ impl<A, I, P> Iterator for Filter<A, I, P> where I: Iterator<Item=A>, P: FnMut(&
 
     #[inline]
     fn next(&mut self) -> Option<A> {
-        for x in self.iter {
+        for x in self.iter.by_ref() {
             if (self.predicate)(&x) {
                 return Some(x);
             } else {
@@ -1728,7 +1728,7 @@ impl<A, B, I, F> Iterator for FilterMap<A, B, I, F> where
 
     #[inline]
     fn next(&mut self) -> Option<B> {
-        for x in self.iter {
+        for x in self.iter.by_ref() {
             match (self.f)(x) {
                 Some(y) => return Some(y),
                 None => ()
@@ -1914,7 +1914,7 @@ impl<A, I, P> Iterator for SkipWhile<A, I, P> where I: Iterator<Item=A>, P: FnMu
 
     #[inline]
     fn next(&mut self) -> Option<A> {
-        for x in self.iter {
+        for x in self.iter.by_ref() {
             if self.flag || !(self.predicate)(&x) {
                 self.flag = true;
                 return Some(x);
@@ -2207,7 +2207,7 @@ impl<A, B, I, U, F> Iterator for FlatMap<A, B, I, U, F> where
     fn next(&mut self) -> Option<B> {
         loop {
             for inner in self.frontiter.iter_mut() {
-                for x in *inner {
+                for x in inner.by_ref() {
                     return Some(x)
                 }
             }
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 1032c56fa22..353d4252dfb 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -65,6 +65,8 @@
 #![allow(unknown_features)] #![feature(int_uint)]
 #![feature(on_unimplemented)]
 #![deny(missing_docs)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 #[macro_use]
 mod macros;
@@ -158,4 +160,6 @@ mod std {
     pub use marker;
     pub use ops;
     pub use option;
+    // for-loops
+    pub use iter;
 }
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index dd9cc553c7c..1be7a0fb066 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1524,7 +1524,7 @@ macro_rules! from_str_radix_float_impl {
                 let mut exp_info = None::<(char, uint)>;
 
                 // Parse the integer part of the significand
-                for (i, c) in cs {
+                for (i, c) in cs.by_ref() {
                     match c.to_digit(radix) {
                         Some(digit) => {
                             // shift significand one digit left
@@ -1572,7 +1572,7 @@ macro_rules! from_str_radix_float_impl {
                 // part of the significand
                 if exp_info.is_none() {
                     let mut power = 1.0;
-                    for (i, c) in cs {
+                    for (i, c) in cs.by_ref() {
                         match c.to_digit(radix) {
                             Some(digit) => {
                                 // Decrease power one order of magnitude
diff --git a/src/librand/lib.rs b/src/librand/lib.rs
index 76258151850..8c50550a6e8 100644
--- a/src/librand/lib.rs
+++ b/src/librand/lib.rs
@@ -498,6 +498,8 @@ mod std {
     pub use core::{option, fmt}; // panic!()
     pub use core::clone; // derive Clone
     pub use core::marker;
+    // for-loops
+    pub use core::iter;
 }
 
 #[cfg(test)]
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 580e55f78a9..e99b203cce7 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -41,6 +41,9 @@
 #![feature(unicode)]
 #![feature(hash)]
 #![cfg_attr(test, feature(test))]
+#![allow(unstable)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 extern crate arena;
 extern crate flate;
diff --git a/src/librustc/middle/dataflow.rs b/src/librustc/middle/dataflow.rs
index 01d42523f35..d5ee0e57b79 100644
--- a/src/librustc/middle/dataflow.rs
+++ b/src/librustc/middle/dataflow.rs
@@ -352,7 +352,9 @@ impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> {
         for (word_index, &word) in words.iter().enumerate() {
             if word != 0 {
                 let base_index = word_index * uint::BITS;
-                for offset in 0u..uint::BITS {
+                // FIXME(#21245) use a for loop
+                let mut iter = 0u..uint::BITS;
+                while let Some(offset) = iter.next() {
                     let bit = 1 << offset;
                     if (word & bit) != 0 {
                         // NB: we round up the total number of bits
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index bb026e237df..5a2ff926669 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -41,6 +41,9 @@
 #![feature(std_misc)]
 #![feature(unicode)]
 #![feature(hash)]
+#![allow(unstable)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 extern crate arena;
 extern crate flate;
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 31c9f996126..4772fac8bd4 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -84,6 +84,9 @@ This API is completely unstable and subject to change.
 #![feature(core)]
 #![feature(rustc_private)]
 #![feature(std_misc)]
+#![allow(unstable)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index f8ba2dc2a74..974d8b96d32 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -32,6 +32,9 @@
 #![feature(test)]
 #![feature(unicode)]
 #![feature(hash)]
+#![allow(unstable)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 extern crate arena;
 extern crate getopts;
diff --git a/src/libserialize/collection_impls.rs b/src/libserialize/collection_impls.rs
index 8b39d91ffae..77308d0a66f 100644
--- a/src/libserialize/collection_impls.rs
+++ b/src/libserialize/collection_impls.rs
@@ -148,7 +148,9 @@ impl<
     fn decode<D: Decoder>(d: &mut D) -> Result<EnumSet<T>, D::Error> {
         let bits = try!(d.read_uint());
         let mut set = EnumSet::new();
-        for bit in 0..uint::BITS {
+        // FIXME(#21245) use a for loop
+        let mut iter = 0..uint::BITS;
+        while let Some(bit) = iter.next() {
             if bits & (1 << bit) != 0 {
                 set.insert(CLike::from_uint(1 << bit));
             }
diff --git a/src/libstd/ascii.rs b/src/libstd/ascii.rs
index 9aa38e711e7..ffc4c5c6bac 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -232,7 +232,10 @@ pub fn escape_default<F>(c: u8, mut f: F) where
         _ => {
             f(b'\\');
             f(b'x');
-            for &offset in [4u, 0u].iter() {
+            // FIXME(#21245) use a for loop
+            let arr = [4u, 0u];
+            let mut iter = arr.iter();
+            while let ::option::Option::Some(&offset) = ::iter::Iterator::next(&mut iter) {
                 match ((c as i32) >> offset) & 0xf {
                     i @ 0 ... 9 => f(b'0' + (i as u8)),
                     i => f(b'a' + (i as u8 - 10)),
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index 9e6a45d8bf0..141c51d8363 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -15,7 +15,7 @@ use self::BucketState::*;
 use clone::Clone;
 use cmp;
 use hash::{Hash, Hasher};
-use iter::{Iterator, ExactSizeIterator, count};
+use iter::{Iterator, IteratorExt, ExactSizeIterator, count};
 use marker::{Copy, Sized, self};
 use mem::{min_align_of, size_of};
 use mem;
@@ -921,7 +921,7 @@ impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
 #[unsafe_destructor]
 impl<'a, K: 'a, V: 'a> Drop for Drain<'a, K, V> {
     fn drop(&mut self) {
-        for _ in *self {}
+        for _ in self.by_ref() {}
     }
 }
 
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index a016ba8fb0c..534ece52ff5 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -123,6 +123,9 @@
 #![feature(rand)]
 #![feature(hash)]
 #![cfg_attr(test, feature(test))]
+#![allow(unstable)]
+// NOTE(stage0): remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 // Don't link to std. We are std.
 #![no_std]
@@ -310,4 +313,6 @@ mod std {
     pub use slice;
 
     pub use boxed; // used for vec![]
+    // for-loops
+    pub use iter;
 }
diff --git a/src/libstd/path/windows.rs b/src/libstd/path/windows.rs
index 88db27013ac..98e0320cd14 100644
--- a/src/libstd/path/windows.rs
+++ b/src/libstd/path/windows.rs
@@ -557,7 +557,7 @@ impl GenericPath for Path {
                     }
                     (Some(a), Some(_)) => {
                         comps.push("..");
-                        for _ in itb {
+                        for _ in itb.by_ref() {
                             comps.push("..");
                         }
                         comps.push(a);
diff --git a/src/libstd/rand/os.rs b/src/libstd/rand/os.rs
index 992afb2d10f..05677e1379d 100644
--- a/src/libstd/rand/os.rs
+++ b/src/libstd/rand/os.rs
@@ -404,7 +404,9 @@ mod test {
         }
 
         // start all the tasks
-        for tx in txs.iter() {
+        // FIXME(#21245) use a for loop
+        let mut iter = txs.iter();
+        while let Some(tx) = iter.next() {
             tx.send(()).unwrap();
         }
     }
diff --git a/src/libstd/sync/mpsc/mod.rs b/src/libstd/sync/mpsc/mod.rs
index 6a43eccbaba..b503b92b00f 100644
--- a/src/libstd/sync/mpsc/mod.rs
+++ b/src/libstd/sync/mpsc/mod.rs
@@ -1476,7 +1476,9 @@ mod test {
 
         let _t = Thread::spawn(move|| {
             let mut count = 0;
-            for x in rx.iter() {
+            // FIXME(#21245) use a for loop
+            let mut iter = rx.iter();
+            while let Some(x) = iter.next() {
                 if count >= 3 {
                     break;
                 } else {
@@ -1940,7 +1942,9 @@ mod sync_tests {
 
         let _t = Thread::spawn(move|| {
             let mut count = 0;
-            for x in rx.iter() {
+            // FIXME(#21245) use a for loop
+            let mut iter = rx.iter();
+            while let Some(x) = iter.next() {
                 if count >= 3 {
                     break;
                 } else {
diff --git a/src/libstd/sync/mpsc/mpsc_queue.rs b/src/libstd/sync/mpsc/mpsc_queue.rs
index 53eba131674..cc09cfd665c 100644
--- a/src/libstd/sync/mpsc/mpsc_queue.rs
+++ b/src/libstd/sync/mpsc/mpsc_queue.rs
@@ -185,7 +185,9 @@ mod tests {
             let tx = tx.clone();
             let q = q.clone();
             Thread::spawn(move|| {
-                for i in 0..nmsgs {
+                // FIXME(#21245) use a for loop
+                let mut iter = 0..nmsgs;
+                while let Some(i) = iter.next() {
                     q.push(i);
                 }
                 tx.send(()).unwrap();
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index a1362f5382c..d739e5fe6a0 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -37,10 +37,14 @@ pub trait MoveMap<T> {
 
 impl<T> MoveMap<T> for Vec<T> {
     fn move_map<F>(mut self, mut f: F) -> Vec<T> where F: FnMut(T) -> T {
-        for p in self.iter_mut() {
-            unsafe {
-                // FIXME(#5016) this shouldn't need to zero to be safe.
-                ptr::write(p, f(ptr::read_and_zero(p)));
+        // FIXME(#21245) use a for loop
+        {
+            let mut iter = self.iter_mut();
+            while let Some(p) = iter.next() {
+                unsafe {
+                    // FIXME(#5016) this shouldn't need to zero to be safe.
+                    ptr::write(p, f(ptr::read_and_zero(p)));
+                }
             }
         }
         self
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index ff4c7b565cb..456c6f73ce1 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -39,6 +39,9 @@
 #![feature(rustc_private)]
 #![feature(std_misc)]
 #![feature(unicode)]
+#![allow(unstable)]
+// NOTE(stage0) remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 extern crate arena;
 extern crate fmt_macros;
diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
index 8fea6bb539f..af8d5b86f4b 100644
--- a/src/libtest/lib.rs
+++ b/src/libtest/lib.rs
@@ -44,6 +44,9 @@
 #![feature(rustc_private)]
 #![feature(std_misc)]
 #![feature(hash)]
+#![allow(unstable)]
+// NOTE(stage0): remove cfg_attr after a snapshot
+#![cfg_attr(not(stage0), allow(unused_mut))]
 
 extern crate getopts;
 extern crate serialize;
diff --git a/src/libunicode/lib.rs b/src/libunicode/lib.rs
index 02f738c9d29..659d57b7292 100644
--- a/src/libunicode/lib.rs
+++ b/src/libunicode/lib.rs
@@ -84,4 +84,7 @@ mod std {
     pub use core::cmp;
     pub use core::fmt;
     pub use core::marker;
+    // for-loops
+    pub use core::iter;
+    pub use core::option;
 }
diff --git a/src/test/bench/shootout-mandelbrot.rs b/src/test/bench/shootout-mandelbrot.rs
index 4a9c5a91dcf..e84e6ac5699 100644
--- a/src/test/bench/shootout-mandelbrot.rs
+++ b/src/test/bench/shootout-mandelbrot.rs
@@ -133,7 +133,9 @@ fn mandelbrot<W: old_io::Writer>(w: uint, mut out: W) -> old_io::IoResult<()> {
                 (i + 1) * chunk_size
             };
 
-            for &init_i in vec_init_i[start..end].iter() {
+            // FIXME(#21245) use a for loop
+            let mut iter = vec_init_i[start..end].iter();
+            while let Some(&init_i) = iter.next() {
                 write_line(init_i, init_r_slice, &mut res);
             }
 
@@ -142,7 +144,9 @@ fn mandelbrot<W: old_io::Writer>(w: uint, mut out: W) -> old_io::IoResult<()> {
     }).collect::<Vec<_>>();
 
     try!(writeln!(&mut out as &mut Writer, "P4\n{} {}", w, h));
-    for res in data.into_iter() {
+    // FIXME(#21245) use a for loop
+    let mut iter = data.into_iter();
+    while let Some(res) = iter.next() {
         try!(out.write(res.join().ok().unwrap().as_slice()));
     }
     out.flush()
diff --git a/src/test/bench/shootout-meteor.rs b/src/test/bench/shootout-meteor.rs
index e6ef58cba35..209cc985383 100644
--- a/src/test/bench/shootout-meteor.rs
+++ b/src/test/bench/shootout-meteor.rs
@@ -180,7 +180,9 @@ fn make_masks() -> Vec<Vec<Vec<u64> > > {
 // all unused piece can be placed on the board.
 fn is_board_unfeasible(board: u64, masks: &Vec<Vec<Vec<u64>>>) -> bool {
     let mut coverable = board;
-    for (i, masks_at) in masks.iter().enumerate() {
+    // FIXME(#21245) use a for loop
+    let mut iter = masks.iter().enumerate();
+    while let Some((i, masks_at)) = iter.next() {
         if board & 1 << i != 0 { continue; }
         for (cur_id, pos_masks) in masks_at.iter().enumerate() {
             if board & 1 << (50 + cur_id) != 0 { continue; }
@@ -222,7 +224,9 @@ fn to_vec(raw_sol: &List<u64>) -> Vec<u8> {
     let mut sol = repeat('.' as u8).take(50).collect::<Vec<_>>();
     for &m in raw_sol.iter() {
         let id = '0' as u8 + get_id(m);
-        for i in 0u..50 {
+        // FIXME(#21245) use a for loop
+        let mut iter = 0u..50;
+        while let Some(i) = iter.next() {
             if m & 1 << i != 0 {
                 sol[i] = id;
             }