Make iter::order functions into methods on Iterator

This does cause some breakage due to deficiencies in resolve -
`path::Components` is both an `Iterator` and implements `Eq`, `Ord`,
etc. If one calls e.g. `partial_cmp` on a `Components` and passes a
`&Components` intending to target the `PartialOrd` impl, the compiler
will select the `partial_cmp` from `Iterator` and then error out. I
doubt anyone will run into breakage from `Components` specifically, but
we should see if there are third party types that will run into issues.

`iter::order::equals` wasn't moved to `Iterator` since it's exactly the
same as `iter::order::eq` but with an `Eq` instead of `PartialEq` bound,
which doensn't seem very useful.

I also updated `le`, `gt`, etc to use `partial_cmp` which lets us drop
the extra `PartialEq` bound.

cc #27737

src/libcollections/btree/map.rs

@@ -22,7 +22,7 @@ use core::fmt::Debug;
 use core::hash::{Hash, Hasher};
 use core::iter::{Map, FromIterator};
 use core::ops::Index;
-use core::{iter, fmt, mem, usize};
+use core::{fmt, mem, usize};
 use Bound::{self, Included, Excluded, Unbounded};
 
 use borrow::Borrow;
@@ -915,15 +915,15 @@ impl<K: Eq, V: Eq> Eq for BTreeMap<K, V> {}
 impl<K: PartialOrd, V: PartialOrd> PartialOrd for BTreeMap<K, V> {
     #[inline]
     fn partial_cmp(&self, other: &BTreeMap<K, V>) -> Option<Ordering> {
-        iter::order::partial_cmp(self.iter(), other.iter())
+        self.iter().partial_cmp(other.iter())
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<K: Ord, V: Ord> Ord for BTreeMap<K, V> {
     #[inline]
     fn cmp(&self, other: &BTreeMap<K, V>) -> Ordering {
-        iter::order::cmp(self.iter(), other.iter())
+        self.iter().cmp(other.iter())
     }
 }
 

src/libcollections/linked_list.rs

@@ -25,7 +25,7 @@ use alloc::boxed::Box;
 use core::cmp::Ordering;
 use core::fmt;
 use core::hash::{Hasher, Hash};
-use core::iter::{self, FromIterator};
+use core::iter::FromIterator;
 use core::mem;
 use core::ptr;
 
@@ -917,12 +917,12 @@ impl<'a, T: 'a + Copy> Extend<&'a T> for LinkedList<T> {
 impl<A: PartialEq> PartialEq for LinkedList<A> {
     fn eq(&self, other: &LinkedList<A>) -> bool {
         self.len() == other.len() &&
-            iter::order::eq(self.iter(), other.iter())
+            self.iter().eq(other.iter())
     }
 
     fn ne(&self, other: &LinkedList<A>) -> bool {
         self.len() != other.len() ||
-            iter::order::ne(self.iter(), other.iter())
+            self.iter().ne(other.iter())
     }
 }
 
@@ -932,15 +932,15 @@ impl<A: Eq> Eq for LinkedList<A> {}
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: PartialOrd> PartialOrd for LinkedList<A> {
     fn partial_cmp(&self, other: &LinkedList<A>) -> Option<Ordering> {
-        iter::order::partial_cmp(self.iter(), other.iter())
+        self.iter().partial_cmp(other.iter())
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: Ord> Ord for LinkedList<A> {
     #[inline]
     fn cmp(&self, other: &LinkedList<A>) -> Ordering {
-        iter::order::cmp(self.iter(), other.iter())
+        self.iter().cmp(other.iter())
     }
 }
 

src/libcollections/vec_deque.rs

@@ -20,7 +20,7 @@
 
 use core::cmp::Ordering;
 use core::fmt;
-use core::iter::{self, repeat, FromIterator};
+use core::iter::{repeat, FromIterator};
 use core::ops::{Index, IndexMut};
 use core::ptr;
 use core::slice;
@@ -1676,15 +1676,15 @@ impl<A: Eq> Eq for VecDeque<A> {}
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: PartialOrd> PartialOrd for VecDeque<A> {
     fn partial_cmp(&self, other: &VecDeque<A>) -> Option<Ordering> {
-        iter::order::partial_cmp(self.iter(), other.iter())
+        self.iter().partial_cmp(other.iter())
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: Ord> Ord for VecDeque<A> {
     #[inline]
     fn cmp(&self, other: &VecDeque<A>) -> Ordering {
-        iter::order::cmp(self.iter(), other.iter())
+        self.iter().cmp(other.iter())
     }
 }