Stabilize step_by for 1.2.0

step_by is generally useful (it was used in multiple places in the
standard library). When it landed in mid-March, it was marked unstable
because it was a "recent addition" to the API. It's been two months, and
there seems to be no controversy about its inclusion in Rust. Therefore,
I propose that we stabilize step_by.

Author: krzysz00

src/doc/trpl/iterators.md

@@ -285,7 +285,6 @@ has no side effect on the original iterator. Let's try it out with our infinite
 iterator from before:
 
 ```rust
-# #![feature(step_by)]
 for i in (1..).step_by(5).take(5) {
     println!("{}", i);
 }

src/libcollections/bit.rs

@@ -38,7 +38,7 @@
 //! [sieve]: http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
 //!
 //! ```
-//! # #![feature(collections, core, step_by)]
+//! # #![feature(collections, core)]
 //! use std::collections::{BitSet, BitVec};
 //! use std::iter;
 //!

src/libcollections/lib.rs

@@ -35,7 +35,6 @@
 #![feature(unicode)]
 #![feature(unique)]
 #![feature(unsafe_no_drop_flag, filling_drop)]
-#![feature(step_by)]
 #![feature(str_char)]
 #![feature(str_words)]
 #![feature(slice_patterns)]

src/libcollectionstest/lib.rs

@@ -21,7 +21,6 @@
 #![feature(unboxed_closures)]
 #![feature(unicode)]
 #![feature(into_cow)]
-#![feature(step_by)]
 #![cfg_attr(test, feature(str_char))]
 #![cfg_attr(test, feature(vec_deque_retain))]
 

src/libcore/iter.rs

@@ -2692,7 +2692,7 @@ step_impl_no_between!(u64 i64);
 /// parameter is the type being iterated over, while `R` is the range
 /// type (usually one of `std::ops::{Range, RangeFrom}`.
 #[derive(Clone)]
-#[unstable(feature = "step_by", reason = "recent addition")]
+#[stable(feature = "step_by", since = "1.2.0")]
 pub struct StepBy<A, R> {
     step_by: A,
     range: R,
@@ -2711,7 +2711,7 @@ impl<A: Step> RangeFrom<A> {
     /// ```
     ///
     /// This prints all even `u8` values.
-    #[unstable(feature = "step_by", reason = "recent addition")]
+    #[stable(feature = "step_by", since = "1.2.0")]
     pub fn step_by(self, by: A) -> StepBy<A, Self> {
         StepBy {
             step_by: by,
@@ -2730,7 +2730,7 @@ impl<A: Step> ops::Range<A> {
     /// # Examples
     ///
     /// ```
-    /// # #![feature(step_by, core)]
+    /// # #![feature(core)]
     /// for i in (0..10).step_by(2) {
     ///     println!("{}", i);
     /// }
@@ -2745,7 +2745,7 @@ impl<A: Step> ops::Range<A> {
     /// 6
     /// 8
     /// ```
-    #[unstable(feature = "step_by", reason = "recent addition")]
+    #[stable(feature = "step_by", since = "1.2.0")]
     pub fn step_by(self, by: A) -> StepBy<A, Self> {
         StepBy {
             step_by: by,

src/libcoretest/lib.rs

@@ -21,7 +21,6 @@
 #![feature(libc)]
 #![feature(hash)]
 #![feature(unique)]
-#![feature(step_by)]
 #![feature(slice_patterns)]
 #![feature(float_from_str_radix)]
 

src/librand/lib.rs

@@ -31,7 +31,6 @@
 #![feature(core)]
 #![feature(no_std)]
 #![feature(staged_api)]
-#![feature(step_by)]
 
 #![cfg_attr(test, feature(test, rand, rustc_private))]
 

src/librustc_back/lib.rs

@@ -39,7 +39,6 @@
 #![feature(staged_api)]
 #![feature(rand)]
 #![feature(path_ext)]
-#![feature(step_by)]
 #![feature(libc)]
 #![feature(fs_canonicalize)]
 #![cfg_attr(test, feature(test, rand))]

src/test/bench/shootout-binarytrees.rs

@@ -38,7 +38,7 @@
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 // OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#![feature(rustc_private, core, step_by)]
+#![feature(rustc_private, core)]
 
 extern crate arena;
 

src/test/bench/shootout-fannkuch-redux.rs

@@ -38,8 +38,6 @@
 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 // OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#![feature(step_by)]
-
 use std::{cmp, mem};
 use std::thread;