auto merge of #6223 : alexcrichton/rust/issue-6183, r=pcwalton

Closes #6183.

The first commit changes the compiler's method of treating a `for` loop, and all the remaining commits are just dealing with the fallout.

The biggest fallout was the `IterBytes` trait, although it's really a whole lot nicer now because all of the `iter_bytes_XX` methods are just and-ed together. Sadly there was a huge amount of stuff that's `cfg(stage0)` gated, but whoever lands the next snapshot is going to have a lot of fun deleting all this code!

src/test/compile-fail/bad-for-loop.rs

@@ -11,4 +11,5 @@
 fn main() {
     fn baz(_x: &fn(y: int) -> int) {}
     for baz |_e| { } //~ ERROR A `for` loop iterator should expect a closure that returns `bool`
+                     //~^ ERROR expected `for` closure to return `bool`
 }

src/test/compile-fail/borrowck-lend-flow-loop.rs

@@ -17,7 +17,7 @@
 fn borrow(_v: &int) {}
 fn borrow_mut(_v: &mut int) {}
 fn cond() -> bool { fail!() }
-fn for_func(_f: &fn() -> bool) { fail!() }
+fn for_func(_f: &fn() -> bool) -> bool { fail!() }
 fn produce<T>() -> T { fail!(); }
 
 fn inc(v: &mut ~int) {

src/test/compile-fail/issue-2817-2.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn not_bool(f: &fn(int) -> ~str) {}
+fn not_bool(f: &fn(int) -> ~str) -> bool {}
 
 fn main() {
     for uint::range(0, 100000) |_i| { //~ ERROR A for-loop body must return (), but

src/test/compile-fail/issue-2817.rs

@@ -16,10 +16,10 @@ fn uuid_random() -> uint { fail!(); }
 
 fn main() {
     do uint::range(0, 100000) |_i| { //~ ERROR Do-block body must return bool, but
-    }
+    };
     // should get a more general message if the callback
     // doesn't return nil
     do uint::range(0, 100000) |_i| { //~ ERROR mismatched types
         ~"str"
-    }
+    };
 }

src/test/compile-fail/issue-3651-2.rs

@@ -9,5 +9,5 @@
 // except according to those terms.
 
 fn main() {
-    do 5.times {} //~ ERROR Do-block body must return bool, but returns () here. Perhaps
+    do 5.times {}; //~ ERROR Do-block body must return bool, but returns () here. Perhaps
 }

src/test/compile-fail/issue-3651.rs

@@ -10,4 +10,5 @@
 
 fn main() {
     for task::spawn { return true; } //~ ERROR A `for` loop iterator should expect a closure that
+                                     //~^ ERROR expected `for` closure to return `bool`
 }

src/test/compile-fail/private-method.rs

@@ -18,7 +18,7 @@ mod kitties {
     }
 
     pub impl cat {
-        priv fn nap(&self) { uint::range(1u, 10000u, |_i| false)}
+        priv fn nap(&self) { uint::range(1u, 10000u, |_i| false); }
     }
 
     pub fn cat(in_x : uint, in_y : int) -> cat {