stdlib: Use if/alt expressions in std::map

Author: brson

src/lib/map.rs

@@ -166,19 +166,17 @@ fn mk_hashmap[K, V](&hashfn[K] hasher, &eqfn[K] eqer) -> hashmap[K, V] {
             }
 
             fn contains_key(&K key) -> bool {
-                alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
-                    case (option::some[V](_)) { ret true; }
-                    case (_) { ret false; }
-                }
-                fail;   // FIXME: remove me when exhaustiveness checking works
+                ret alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
+                    case (option::some[V](_)) { true }
+                    case (_) { false }
+                };
             }
 
             fn get(&K key) -> V {
-                alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
-                    case (option::some[V](?val)) { ret val; }
-                    case (_) { fail; }
-                }
-                fail;   // FIXME: remove me when exhaustiveness checking works
+                ret alt (find_common[K, V](hasher, eqer, bkts, nbkts, key)) {
+                    case (option::some[V](?val)) { val }
+                    case (_) { fail }
+                };
             }
 
             fn find(&K key) -> option::t[V] {