rollup merge of rust-lang#19770: csouth3/iterator-wrapperstructs

Using a type alias for iterator implementations is fragile since this exposes the implementation to users of the iterator, and any changes could break existing code.

This PR changes the iterators of `BTreeMap`, `BTreeSet`, `HashMap`, and `HashSet` to use proper new types, rather than type aliases.  However, since it is fair-game to treat a type-alias as the aliased type, this is a:

[breaking-change].

Author: brson

src/libcollections/btree/map.rs

@@ -29,6 +29,7 @@ use std::hash::{Writer, Hash};
 use core::default::Default;
 use core::{iter, fmt, mem};
 use core::fmt::Show;
+use core::iter::Map;
 
 use ring_buf::RingBuf;
 
@@ -110,12 +111,14 @@ pub struct MoveEntries<K, V> {
 }
 
 /// An iterator over a BTreeMap's keys.
-pub type Keys<'a, K, V> =
-    iter::Map<(&'a K, &'a V), &'a K, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>;
+pub struct Keys<'a, K: 'a, V: 'a> {
+    inner: Map<(&'a K, &'a V), &'a K, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
+}
 
 /// An iterator over a BTreeMap's values.
-pub type Values<'a, K, V> =
-    iter::Map<(&'a K, &'a V), &'a V, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>;
+pub struct Values<'a, K: 'a, V: 'a> {
+    inner: Map<(&'a K, &'a V), &'a V, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
+}
 
 /// A view into a single entry in a map, which may either be vacant or occupied.
 pub enum Entry<'a, K:'a, V:'a> {
@@ -1054,6 +1057,25 @@ impl<K, V> DoubleEndedIterator<(K, V)> for MoveEntries<K, V> {
 impl<K, V> ExactSizeIterator<(K, V)> for MoveEntries<K, V> {}
 
 
+impl<'a, K, V> Iterator<&'a K> for Keys<'a, K, V> {
+    fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
+    fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+}
+impl<'a, K, V> DoubleEndedIterator<&'a K> for Keys<'a, K, V> {
+    fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
+}
+impl<'a, K, V> ExactSizeIterator<&'a K> for Keys<'a, K, V> {}
+
+
+impl<'a, K, V> Iterator<&'a V> for Values<'a, K, V> {
+    fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
+    fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+}
+impl<'a, K, V> DoubleEndedIterator<&'a V> for Values<'a, K, V> {
+    fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
+}
+impl<'a, K, V> ExactSizeIterator<&'a V> for Values<'a, K, V> {}
+
 
 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
     /// Sets the value of the entry with the VacantEntry's key,
@@ -1204,7 +1226,7 @@ impl<K, V> BTreeMap<K, V> {
     pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
 
-        self.iter().map(first)
+        Keys { inner: self.iter().map(first) }
     }
 
     /// Gets an iterator over the values of the map.
@@ -1225,7 +1247,7 @@ impl<K, V> BTreeMap<K, V> {
     pub fn values<'a>(&'a self) -> Values<'a, K, V> {
         fn second<A, B>((_, b): (A, B)) -> B { b }
 
-        self.iter().map(second)
+        Values { inner: self.iter().map(second) }
     }
 
     /// Return the number of elements in the map.

src/libcollections/btree/set.rs

@@ -17,8 +17,8 @@ use btree_map::{BTreeMap, Keys, MoveEntries};
 use std::hash::Hash;
 use core::borrow::BorrowFrom;
 use core::default::Default;
-use core::{iter, fmt};
-use core::iter::Peekable;
+use core::fmt;
+use core::iter::{Peekable, Map};
 use core::fmt::Show;
 
 // FIXME(conventions): implement bounded iterators
@@ -33,11 +33,14 @@ pub struct BTreeSet<T>{
 }
 
 /// An iterator over a BTreeSet's items.
-pub type Items<'a, T> = Keys<'a, T, ()>;
+pub struct Items<'a, T: 'a> {
+    iter: Keys<'a, T, ()>
+}
 
 /// An owning iterator over a BTreeSet's items.
-pub type MoveItems<T> =
-    iter::Map<(T, ()), T, MoveEntries<T, ()>, fn((T, ())) -> T>;
+pub struct MoveItems<T> {
+    iter: Map<(T, ()), T, MoveEntries<T, ()>, fn((T, ())) -> T>
+}
 
 /// A lazy iterator producing elements in the set difference (in-order).
 pub struct DifferenceItems<'a, T:'a> {
@@ -105,7 +108,7 @@ impl<T> BTreeSet<T> {
     /// ```
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn iter<'a>(&'a self) -> Items<'a, T> {
-        self.map.keys()
+        Items { iter: self.map.keys() }
     }
 
     /// Gets an iterator for moving out the BtreeSet's contents.
@@ -124,7 +127,7 @@ impl<T> BTreeSet<T> {
     pub fn into_iter(self) -> MoveItems<T> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
 
-        self.map.into_iter().map(first)
+        MoveItems { iter: self.map.into_iter().map(first) }
     }
 }
 
@@ -635,6 +638,25 @@ impl<T: Show> Show for BTreeSet<T> {
     }
 }
 
+impl<'a, T> Iterator<&'a T> for Items<'a, T> {
+    fn next(&mut self) -> Option<&'a T> { self.iter.next() }
+    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+}
+impl<'a, T> DoubleEndedIterator<&'a T> for Items<'a, T> {
+    fn next_back(&mut self) -> Option<&'a T> { self.iter.next_back() }
+}
+impl<'a, T> ExactSizeIterator<&'a T> for Items<'a, T> {}
+
+
+impl<T> Iterator<T> for MoveItems<T> {
+    fn next(&mut self) -> Option<T> { self.iter.next() }
+    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
+}
+impl<T> DoubleEndedIterator<T> for MoveItems<T> {
+    fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
+}
+impl<T> ExactSizeIterator<T> for MoveItems<T> {}
+
 /// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
 fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>,
                         short: Ordering, long: Ordering) -> Ordering {

src/libstd/collections/hash/map.rs

@@ -20,7 +20,7 @@ use cmp::{max, Eq, Equiv, PartialEq};
 use default::Default;
 use fmt::{mod, Show};
 use hash::{Hash, Hasher, RandomSipHasher};
-use iter::{mod, Iterator, IteratorExt, FromIterator, Extend};
+use iter::{mod, Iterator, IteratorExt, FromIterator, Extend, Map};
 use kinds::Sized;
 use mem::{mod, replace};
 use num::{Int, UnsignedInt};
@@ -859,7 +859,7 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
     pub fn keys(&self) -> Keys<K, V> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
 
-        self.iter().map(first)
+        Keys { inner: self.iter().map(first) }
     }
 
     /// An iterator visiting all values in arbitrary order.
@@ -883,7 +883,7 @@ impl<K: Eq + Hash<S>, V, S, H: Hasher<S>> HashMap<K, V, H> {
     pub fn values(&self) -> Values<K, V> {
         fn second<A, B>((_, b): (A, B)) -> B { b }
 
-        self.iter().map(second)
+        Values { inner: self.iter().map(second) }
     }
 
     /// An iterator visiting all key-value pairs in arbitrary order.
@@ -1335,6 +1335,16 @@ pub struct MoveEntries<K, V> {
     >
 }
 
+/// HashMap keys iterator
+pub struct Keys<'a, K: 'a, V: 'a> {
+    inner: Map<(&'a K, &'a V), &'a K, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>
+}
+
+/// HashMap values iterator
+pub struct Values<'a, K: 'a, V: 'a> {
+    inner: Map<(&'a K, &'a V), &'a V, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>
+}
+
 /// A view into a single occupied location in a HashMap
 pub struct OccupiedEntry<'a, K:'a, V:'a> {
     elem: FullBucket<K, V, &'a mut RawTable<K, V>>,
@@ -1365,36 +1375,28 @@ enum VacantEntryState<K, V, M> {
 }
 
 impl<'a, K, V> Iterator<(&'a K, &'a V)> for Entries<'a, K, V> {
-    #[inline]
-    fn next(&mut self) -> Option<(&'a K, &'a V)> {
-        self.inner.next()
-    }
-    #[inline]
-    fn size_hint(&self) -> (uint, Option<uint>) {
-        self.inner.size_hint()
-    }
+    #[inline] fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 
 impl<'a, K, V> Iterator<(&'a K, &'a mut V)> for MutEntries<'a, K, V> {
-    #[inline]
-    fn next(&mut self) -> Option<(&'a K, &'a mut V)> {
-        self.inner.next()
-    }
-    #[inline]
-    fn size_hint(&self) -> (uint, Option<uint>) {
-        self.inner.size_hint()
-    }
+    #[inline] fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 
 impl<K, V> Iterator<(K, V)> for MoveEntries<K, V> {
-    #[inline]
-    fn next(&mut self) -> Option<(K, V)> {
-        self.inner.next()
-    }
-    #[inline]
-    fn size_hint(&self) -> (uint, Option<uint>) {
-        self.inner.size_hint()
-    }
+    #[inline] fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+}
+
+impl<'a, K, V> Iterator<&'a K> for Keys<'a, K, V> {
+    #[inline] fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
+}
+
+impl<'a, K, V> Iterator<&'a V> for Values<'a, K, V> {
+    #[inline] fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
+    #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 
 impl<'a, K, V> OccupiedEntry<'a, K, V> {
@@ -1448,14 +1450,6 @@ impl<'a, K, V> VacantEntry<'a, K, V> {
     }
 }
 
-/// HashMap keys iterator
-pub type Keys<'a, K, V> =
-    iter::Map<(&'a K, &'a V), &'a K, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a K>;
-
-/// HashMap values iterator
-pub type Values<'a, K, V> =
-    iter::Map<(&'a K, &'a V), &'a V, Entries<'a, K, V>, fn((&'a K, &'a V)) -> &'a V>;
-
 impl<K: Eq + Hash<S>, V, S, H: Hasher<S> + Default> FromIterator<(K, V)> for HashMap<K, V, H> {
     fn from_iter<T: Iterator<(K, V)>>(iter: T) -> HashMap<K, V, H> {
         let (lower, _) = iter.size_hint();