style: Use `iter` for IntoIterator parameter names

This commit standardizes the codebase on `iter` for parameters with
IntoIterator bounds.

Previously about 40% of IntoIterator parameters were named `iterable`,
with most of the rest being named `iter`. There was a single place where
it was named `iterator`.

src/libcollections/binary_heap.rs

@@ -980,13 +980,13 @@ impl<'a, T> IntoIterator for &'a BinaryHeap<T> where T: Ord {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Ord> Extend<T> for BinaryHeap<T> {
-    fn extend<I: IntoIterator<Item = T>>(&mut self, iterable: I) {
-        let iter = iterable.into_iter();
-        let (lower, _) = iter.size_hint();
+    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
+        let iterator = iter.into_iter();
+        let (lower, _) = iterator.size_hint();
 
         self.reserve(lower);
 
-        for elem in iter {
+        for elem in iterator {
             self.push(elem);
         }
     }

src/libcollections/string.rs

@@ -1388,35 +1388,35 @@ impl Clone for String {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl FromIterator<char> for String {
-    fn from_iter<I: IntoIterator<Item = char>>(iterable: I) -> String {
+    fn from_iter<I: IntoIterator<Item = char>>(iter: I) -> String {
         let mut buf = String::new();
-        buf.extend(iterable);
+        buf.extend(iter);
         buf
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> FromIterator<&'a str> for String {
-    fn from_iter<I: IntoIterator<Item = &'a str>>(iterable: I) -> String {
+    fn from_iter<I: IntoIterator<Item = &'a str>>(iter: I) -> String {
         let mut buf = String::new();
-        buf.extend(iterable);
+        buf.extend(iter);
         buf
     }
 }
 
 #[stable(feature = "extend_string", since = "1.4.0")]
 impl FromIterator<String> for String {
-    fn from_iter<I: IntoIterator<Item = String>>(iterable: I) -> String {
+    fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
         let mut buf = String::new();
-        buf.extend(iterable);
+        buf.extend(iter);
         buf
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Extend<char> for String {
-    fn extend<I: IntoIterator<Item = char>>(&mut self, iterable: I) {
-        let iterator = iterable.into_iter();
+    fn extend<I: IntoIterator<Item = char>>(&mut self, iter: I) {
+        let iterator = iter.into_iter();
         let (lower_bound, _) = iterator.size_hint();
         self.reserve(lower_bound);
         for ch in iterator {
@@ -1427,15 +1427,15 @@ impl Extend<char> for String {
 
 #[stable(feature = "extend_ref", since = "1.2.0")]
 impl<'a> Extend<&'a char> for String {
-    fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iterable: I) {
-        self.extend(iterable.into_iter().cloned());
+    fn extend<I: IntoIterator<Item = &'a char>>(&mut self, iter: I) {
+        self.extend(iter.into_iter().cloned());
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a> Extend<&'a str> for String {
-    fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iterable: I) {
-        for s in iterable {
+    fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
+        for s in iter {
             self.push_str(s)
         }
     }
@@ -1443,8 +1443,8 @@ impl<'a> Extend<&'a str> for String {
 
 #[stable(feature = "extend_string", since = "1.4.0")]
 impl Extend<String> for String {
-    fn extend<I: IntoIterator<Item = String>>(&mut self, iterable: I) {
-        for s in iterable {
+    fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
+        for s in iter {
             self.push_str(&s)
         }
     }

src/libcollections/vec.rs

@@ -1302,13 +1302,13 @@ impl<T> ops::DerefMut for Vec<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
-    fn from_iter<I: IntoIterator<Item = T>>(iterable: I) -> Vec<T> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Vec<T> {
         // Unroll the first iteration, as the vector is going to be
         // expanded on this iteration in every case when the iterable is not
         // empty, but the loop in extend_desugared() is not going to see the
         // vector being full in the few subsequent loop iterations.
         // So we get better branch prediction.
-        let mut iterator = iterable.into_iter();
+        let mut iterator = iter.into_iter();
         let mut vector = match iterator.next() {
             None => return Vec::new(),
             Some(element) => {
@@ -1389,8 +1389,8 @@ impl<'a, T> IntoIterator for &'a mut Vec<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Extend<T> for Vec<T> {
     #[inline]
-    fn extend<I: IntoIterator<Item = T>>(&mut self, iterable: I) {
-        self.extend_desugared(iterable.into_iter())
+    fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
+        self.extend_desugared(iter.into_iter())
     }
 }
 

src/libcollections/vec_deque.rs

@@ -2057,8 +2057,8 @@ impl<A> IndexMut<usize> for VecDeque<A> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A> FromIterator<A> for VecDeque<A> {
-    fn from_iter<T: IntoIterator<Item = A>>(iterable: T) -> VecDeque<A> {
-        let iterator = iterable.into_iter();
+    fn from_iter<T: IntoIterator<Item = A>>(iter: T) -> VecDeque<A> {
+        let iterator = iter.into_iter();
         let (lower, _) = iterator.size_hint();
         let mut deq = VecDeque::with_capacity(lower);
         deq.extend(iterator);

src/libcore/iter.rs

@@ -2458,10 +2458,10 @@ impl<'a, I: Iterator + ?Sized> Iterator for &'a mut I {
 ///
 /// // and we'll implement FromIterator
 /// impl FromIterator<i32> for MyCollection {
-///     fn from_iter<I: IntoIterator<Item=i32>>(iterator: I) -> Self {
+///     fn from_iter<I: IntoIterator<Item=i32>>(iter: I) -> Self {
 ///         let mut c = MyCollection::new();
 ///
-///         for i in iterator {
+///         for i in iter {
 ///             c.add(i);
 ///         }
 ///
@@ -2508,7 +2508,7 @@ pub trait FromIterator<A>: Sized {
     /// assert_eq!(v, vec![5, 5, 5, 5, 5]);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    fn from_iter<T: IntoIterator<Item=A>>(iterator: T) -> Self;
+    fn from_iter<T: IntoIterator<Item=A>>(iter: T) -> Self;
 }
 
 /// Conversion into an `Iterator`.
@@ -2683,11 +2683,11 @@ impl<I: Iterator> IntoIterator for I {
 ///     // This is a bit simpler with the concrete type signature: we can call
 ///     // extend on anything which can be turned into an Iterator which gives
 ///     // us i32s. Because we need i32s to put into MyCollection.
-///     fn extend<T: IntoIterator<Item=i32>>(&mut self, iterable: T) {
+///     fn extend<T: IntoIterator<Item=i32>>(&mut self, iter: T) {
 ///
 ///         // The implementation is very straightforward: loop through the
 ///         // iterator, and add() each element to ourselves.
-///         for elem in iterable {
+///         for elem in iter {
 ///             self.add(elem);
 ///         }
 ///     }
@@ -2727,7 +2727,7 @@ pub trait Extend<A> {
     /// assert_eq!("abcdef", &message);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    fn extend<T: IntoIterator<Item=A>>(&mut self, iterable: T);
+    fn extend<T: IntoIterator<Item=A>>(&mut self, iter: T);
 }
 
 /// An iterator able to yield elements from both ends.

src/librustc_unicode/char.rs

@@ -748,7 +748,7 @@ pub struct DecodeUtf16<I>
     buf: Option<u16>,
 }
 
-/// Create an iterator over the UTF-16 encoded code points in `iterable`,
+/// Create an iterator over the UTF-16 encoded code points in `iter`,
 /// returning unpaired surrogates as `Err`s.
 ///
 /// # Examples
@@ -796,9 +796,9 @@ pub struct DecodeUtf16<I>
 /// ```
 #[unstable(feature = "decode_utf16", reason = "recently exposed", issue = "27830")]
 #[inline]
-pub fn decode_utf16<I: IntoIterator<Item = u16>>(iterable: I) -> DecodeUtf16<I::IntoIter> {
+pub fn decode_utf16<I: IntoIterator<Item = u16>>(iter: I) -> DecodeUtf16<I::IntoIter> {
     DecodeUtf16 {
-        iter: iterable.into_iter(),
+        iter: iter.into_iter(),
         buf: None,
     }
 }

src/libstd/collections/hash/map.rs

@@ -1580,11 +1580,11 @@ impl<'a, K: 'a, V: 'a> VacantEntry<'a, K, V> {
 impl<K, V, S> FromIterator<(K, V)> for HashMap<K, V, S>
     where K: Eq + Hash, S: BuildHasher + Default
 {
-    fn from_iter<T: IntoIterator<Item=(K, V)>>(iterable: T) -> HashMap<K, V, S> {
-        let iter = iterable.into_iter();
-        let lower = iter.size_hint().0;
+    fn from_iter<T: IntoIterator<Item=(K, V)>>(iter: T) -> HashMap<K, V, S> {
+        let iterator = iter.into_iter();
+        let lower = iterator.size_hint().0;
         let mut map = HashMap::with_capacity_and_hasher(lower, Default::default());
-        map.extend(iter);
+        map.extend(iterator);
         map
     }
 }

src/libstd/collections/hash/set.rs

@@ -633,11 +633,11 @@ impl<T, S> FromIterator<T> for HashSet<T, S>
     where T: Eq + Hash,
           S: BuildHasher + Default,
 {
-    fn from_iter<I: IntoIterator<Item=T>>(iterable: I) -> HashSet<T, S> {
-        let iter = iterable.into_iter();
-        let lower = iter.size_hint().0;
+    fn from_iter<I: IntoIterator<Item=T>>(iter: I) -> HashSet<T, S> {
+        let iterator = iter.into_iter();
+        let lower = iterator.size_hint().0;
         let mut set = HashSet::with_capacity_and_hasher(lower, Default::default());
-        set.extend(iter);
+        set.extend(iterator);
         set
     }
 }

src/libstd/sys/common/wtf8.rs

@@ -356,8 +356,8 @@ impl FromIterator<CodePoint> for Wtf8Buf {
 /// This replaces surrogate code point pairs with supplementary code points,
 /// like concatenating ill-formed UTF-16 strings effectively would.
 impl Extend<CodePoint> for Wtf8Buf {
-    fn extend<T: IntoIterator<Item=CodePoint>>(&mut self, iterable: T) {
-        let iterator = iterable.into_iter();
+    fn extend<T: IntoIterator<Item=CodePoint>>(&mut self, iter: T) {
+        let iterator = iter.into_iter();
         let (low, _high) = iterator.size_hint();
         // Lower bound of one byte per code point (ASCII only)
         self.bytes.reserve(low);