auto merge of #18440 : japaric/rust/hash, r=alexcrichton

- The signature of the `*_equiv` methods of `HashMap` and similar structures have changed, and now require one less level of indirection. Change your code from:

``` rust
hashmap.find_equiv(&"Hello");
hashmap.find_equiv(&&[0u8, 1, 2]);
```

to:

``` rust
hashmap.find_equiv("Hello");
hashmap.find_equiv(&[0u8, 1, 2]);
```

- The generic parameter `T` of the `Hasher::hash<T>` method have become `Sized?`. Downstream code must add `Sized?` to that method in their implementations. For example:

``` rust
impl Hasher<FnvState> for FnvHasher {
    fn hash<T: Hash<FnvState>>(&self, t: &T) -> u64 { /* .. */ }
}
```

must be changed to:

``` rust
impl Hasher<FnvState> for FnvHasher {
    fn hash<Sized? T: Hash<FnvState>>(&self, t: &T) -> u64 { /* .. */ }
    //      ^^^^^^
}
```

[breaking-change]

---

After review I'll squash the commits and update the commit message with the above paragraph.

r? @aturon 
cc #16918

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index ed2455d0a30..105118ff76a 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -75,7 +75,7 @@ impl<T: Eq + Hash + Clone + 'static> Interner<T> {
         (*vect).len()
     }
 
-    pub fn find_equiv<Q:Hash + Equiv<T>>(&self, val: &Q) -> Option<Name> {
+    pub fn find_equiv<Sized? Q: Hash + Equiv<T>>(&self, val: &Q) -> Option<Name> {
         let map = self.map.borrow();
         match (*map).find_equiv(val) {
             Some(v) => Some(*v),
@@ -149,7 +149,7 @@ impl StrInterner {
 
     pub fn intern(&self, val: &str) -> Name {
         let mut map = self.map.borrow_mut();
-        match map.find_equiv(&val) {
+        match map.find_equiv(val) {
             Some(&idx) => return idx,
             None => (),
         }
@@ -195,7 +195,7 @@ impl StrInterner {
         self.vect.borrow().len()
     }
 
-    pub fn find_equiv<Q:Hash + Equiv<RcStr>>(&self, val: &Q) -> Option<Name> {
+    pub fn find_equiv<Sized? Q:Hash + Equiv<RcStr>>(&self, val: &Q) -> Option<Name> {
         match (*self.map.borrow()).find_equiv(val) {
             Some(v) => Some(*v),
             None => None,