collections: Enable IndexMut for some collections

This commit enables implementations of IndexMut for a number of collections,
including Vec, RingBuf, SmallIntMap, TrieMap, TreeMap, and HashMap. At the same
time this deprecates the `get_mut` methods on vectors in favor of using the
indexing notation.

cc #18424

src/libregex/compile.rs

@@ -157,7 +157,7 @@ impl<'r> Compiler<'r> {
                 if cap >= len {
                     self.names.grow(10 + cap - len, None)
                 }
-                *self.names.get_mut(cap) = name;
+                self.names[cap] = name;
 
                 self.push(Save(2 * cap));
                 self.compile(*x);
@@ -243,7 +243,7 @@ impl<'r> Compiler<'r> {
     /// `panic!` is called.
     #[inline]
     fn set_split(&mut self, i: InstIdx, pc1: InstIdx, pc2: InstIdx) {
-        let split = self.insts.get_mut(i);
+        let split = &mut self.insts[i];
         match *split {
             Split(_, _) => *split = Split(pc1, pc2),
             _ => panic!("BUG: Invalid split index."),
@@ -263,7 +263,7 @@ impl<'r> Compiler<'r> {
     /// `panic!` is called.
     #[inline]
     fn set_jump(&mut self, i: InstIdx, pc: InstIdx) {
-        let jmp = self.insts.get_mut(i);
+        let jmp = &mut self.insts[i];
         match *jmp {
             Jump(_) => *jmp = Jump(pc),
             _ => panic!("BUG: Invalid jump index."),

src/libregex/parse.rs

@@ -978,7 +978,7 @@ fn combine_ranges(unordered: Vec<(char, char)>) -> Vec<(char, char)> {
         }
         match which {
             None => ordered.push((us, ue)),
-            Some(i) => *ordered.get_mut(i) = (us, ue),
+            Some(i) => ordered[i] = (us, ue),
         }
     }
     ordered.sort();

src/libregex/vm.rs

@@ -461,13 +461,13 @@ impl Threads {
     }
 
     fn add(&mut self, pc: uint, groups: &[Option<uint>], empty: bool) {
-        let t = self.queue.get_mut(self.size);
+        let t = &mut self.queue[self.size];
         t.pc = pc;
         match (empty, self.which) {
             (_, Exists) | (true, _) => {},
             (false, Location) => {
-                *t.groups.get_mut(0) = groups[0];
-                *t.groups.get_mut(1) = groups[1];
+                t.groups[0] = groups[0];
+                t.groups[1] = groups[1];
             }
             (false, Submatches) => {
                 for (slot, val) in t.groups.iter_mut().zip(groups.iter()) {
@@ -475,7 +475,7 @@ impl Threads {
                 }
             }
         }
-        *self.sparse.get_mut(pc) = self.size;
+        self.sparse[pc] = self.size;
         self.size += 1;
     }
 
@@ -497,7 +497,7 @@ impl Threads {
 
     #[inline]
     fn groups<'r>(&'r mut self, i: uint) -> &'r mut [Option<uint>] {
-        self.queue.get_mut(i).groups.as_mut_slice()
+        self.queue[i].groups.as_mut_slice()
     }
 }