Revert "Fix warnings and hints in the SDK"

sdk/lib/async/stream_impl.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.async;
 
 /** Abstract and private interface for a place to put events. */
 abstract class _EventSink<T> {
   void _add(T data);
   void _addError(Object error, StackTrace stackTrace);
@@ skipping 980 matching lines @@
       return new _Future<bool>.immediate(false);
     }
     if (_state == _STATE_MOVING) {
       throw new StateError("Already waiting for next.");
     }
     if (_state == _STATE_FOUND) {
       _state = _STATE_MOVING;
       _current = null;
       _futureOrPrefetch = new _Future<bool>();
       return _futureOrPrefetch;
-    }
-    assert(_state >= _STATE_EXTRA_DATA);
-    switch (_state) {
-      case _STATE_EXTRA_DATA:
-        _state = _STATE_FOUND;
-        _current = _futureOrPrefetch;
-        _futureOrPrefetch = null;
-        _subscription.resume();
-        return new _Future<bool>.immediate(true);
-      case _STATE_EXTRA_ERROR:
-        AsyncError prefetch = _futureOrPrefetch;
-        _clear();
-        return new _Future<bool>.immediateError(prefetch.error,
-                                                prefetch.stackTrace);
-      case _STATE_EXTRA_DONE:
-        _clear();
-        return new _Future<bool>.immediate(false);
-      default:
-        throw "Unreachable";
+    } else {
+      assert(_state >= _STATE_EXTRA_DATA);
+      switch (_state) {
+        case _STATE_EXTRA_DATA:
+          _state = _STATE_FOUND;
+          _current = _futureOrPrefetch;
+          _futureOrPrefetch = null;
+          _subscription.resume();
+          return new _Future<bool>.immediate(true);
+        case _STATE_EXTRA_ERROR:
+          AsyncError prefetch = _futureOrPrefetch;
+          _clear();
+          return new _Future<bool>.immediateError(prefetch.error,
+                                                  prefetch.stackTrace);
+        case _STATE_EXTRA_DONE:
+          _clear();
+          return new _Future<bool>.immediate(false);
+      }
     }
   }
 
   /** Clears up the internal state when the iterator ends. */
   void _clear() {
     _subscription = null;
     _futureOrPrefetch = null;
     _current = null;
     _state = _STATE_DONE;
   }
@@ skipping 45 matching lines @@
       _Future<bool> hasNext = _futureOrPrefetch;
       _clear();
       hasNext._complete(false);
       return;
     }
     _subscription.pause();
     _futureOrPrefetch = null;
     _state = _STATE_EXTRA_DONE;
   }
 }