Rationalize coercions

test/dart_codegen/expect/async/future.dart

 part of dart.async;
  abstract class Future<T> {static final _Future _nullFuture = ((__x10) => DEVC$RT.cast(__x10, DEVC$RT.type((Future<dynamic> _) {
   }
 ), DEVC$RT.type((_Future<dynamic> _) {
   }
-), "CastExact", """line 98, column 38 of dart:async/future.dart: """, __x10 is _Future<dynamic>, true))(new Future.value(null));
+), "InferableAllocation", """line 98, column 38 of dart:async/future.dart: """, __x10 is _Future<dynamic>, true))(new Future.value(null));
  factory Future(computation()) {
   _Future result = new _Future<T>();
    Timer.run(() {
     try {
       result._complete(computation());
       }
      catch (e, s) {
       _completeWithErrorCallback(result, e, s);
       }
     }
   );
    return DEVC$RT.cast(result, DEVC$RT.type((_Future<dynamic> _) {
     }
   ), DEVC$RT.type((Future<T> _) {
     }
-  ), "CastDynamic", """line 123, column 12 of dart:async/future.dart: """, result is Future<T>, false);
+  ), "CompositeCast", """line 123, column 12 of dart:async/future.dart: """, result is Future<T>, false);
   }
  factory Future.microtask(computation()) {
   _Future result = new _Future<T>();
    scheduleMicrotask(() {
     try {
       result._complete(computation());
       }
      catch (e, s) {
       _completeWithErrorCallback(result, e, s);
       }
     }
   );
    return DEVC$RT.cast(result, DEVC$RT.type((_Future<dynamic> _) {
     }
   ), DEVC$RT.type((Future<T> _) {
     }
-  ), "CastDynamic", """line 149, column 12 of dart:async/future.dart: """, result is Future<T>, false);
+  ), "CompositeCast", """line 149, column 12 of dart:async/future.dart: """, result is Future<T>, false);
   }
  factory Future.sync(computation()) {
   try {
     var result = computation();
      return new Future<T>.value(result);
     }
    catch (error, stackTrace) {
     return new Future<T>.error(error, stackTrace);
     }
   }
@@ skipping 19 matching lines @@
       }
      catch (e, s) {
       _completeWithErrorCallback(result, e, s);
       }
     }
   );
    return DEVC$RT.cast(result, DEVC$RT.type((_Future<dynamic> _) {
     }
   ), DEVC$RT.type((Future<T> _) {
     }
-  ), "CastDynamic", """line 233, column 12 of dart:async/future.dart: """, result is Future<T>, false);
+  ), "CompositeCast", """line 233, column 12 of dart:async/future.dart: """, result is Future<T>, false);
   }
  static Future<List> wait(Iterable<Future> futures, {
   bool eagerError : false, void cleanUp(successValue)}
 ) {
   final _Future<List> result = new _Future<List>();
    List values;
    int remaining = 0;
    var error;
    StackTrace stackTrace;
    void handleError(theError, theStackTrace) {
     remaining--;
      if (values != null) {
       if (cleanUp != null) {
         for (var value in values) {
           if (value != null) {
             new Future.sync(() {
               cleanUp(value);
               }
             );
             }
           }
         }
        values = null;
        if (remaining == 0 || eagerError) {
-        result._completeError(theError, DEVC$RT.cast(theStackTrace, dynamic, StackTrace, "CastGeneral", """line 280, column 43 of dart:async/future.dart: """, theStackTrace is StackTrace, true));
+        result._completeError(theError, DEVC$RT.cast(theStackTrace, dynamic, StackTrace, "DynamicCast", """line 280, column 43 of dart:async/future.dart: """, theStackTrace is StackTrace, true));
         }
        else {
         error = theError;
-         stackTrace = DEVC$RT.cast(theStackTrace, dynamic, StackTrace, "CastGeneral", """line 283, column 24 of dart:async/future.dart: """, theStackTrace is StackTrace, true);
+         stackTrace = DEVC$RT.cast(theStackTrace, dynamic, StackTrace, "DynamicCast", """line 283, column 24 of dart:async/future.dart: """, theStackTrace is StackTrace, true);
         }
       }
      else if (remaining == 0 && !eagerError) {
       result._completeError(error, stackTrace);
       }
     }
    for (Future future in futures) {
     int pos = remaining++;
      future.then((Object value) {
       remaining--;
@@ skipping 15 matching lines @@
           }
         }
       }
     , onError: handleError);
     }
    if (remaining == 0) {
     return ((__x11) => DEVC$RT.cast(__x11, DEVC$RT.type((Future<dynamic> _) {
       }
     ), DEVC$RT.type((Future<List<dynamic>> _) {
       }
-    ), "CastExact", """line 313, column 14 of dart:async/future.dart: """, __x11 is Future<List<dynamic>>, false))(new Future.value(const []));
+    ), "InferableAllocation", """line 313, column 14 of dart:async/future.dart: """, __x11 is Future<List<dynamic>>, false))(new Future.value(const []));
     }
    values = new List(remaining);
    return result;
   }
  static Future forEach(Iterable input, f(element)) {
   Iterator iterator = input.iterator;
    return doWhile(() {
     if (!iterator.moveNext()) return false;
      return new Future.sync(() => f(iterator.current)).then((_) => true);
     }
   );
   }
  static Future doWhile(f()) {
   _Future doneSignal = new _Future();
    var nextIteration;
    nextIteration = Zone.current.bindUnaryCallback((bool keepGoing) {
     if (keepGoing) {
-      new Future.sync(f).then(DEVC$RT.cast(nextIteration, dynamic, __t12, "CastGeneral", """line 361, column 33 of dart:async/future.dart: """, nextIteration is __t12, true), onError: doneSignal._completeError);
+      new Future.sync(f).then(DEVC$RT.cast(nextIteration, dynamic, __t12, "DynamicCast", """line 361, column 33 of dart:async/future.dart: """, nextIteration is __t12, true), onError: doneSignal._completeError);
       }
      else {
       doneSignal._complete(null);
       }
     }
   , runGuarded: true);
    nextIteration(true);
    return doneSignal;
   }
  Future then(onValue(T value), {
@@ skipping 19 matching lines @@
 }
 }
  abstract class Completer<T> {factory Completer() => new _AsyncCompleter<T>();
  factory Completer.sync() => new _SyncCompleter<T>();
  Future<T> get future;
  void complete([value]);
  void completeError(Object error, [StackTrace stackTrace]);
  bool get isCompleted;
 }
  void _completeWithErrorCallback(_Future result, error, stackTrace) {
-AsyncError replacement = Zone.current.errorCallback(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "CastGeneral", """line 719, column 62 of dart:async/future.dart: """, stackTrace is StackTrace, true));
+AsyncError replacement = Zone.current.errorCallback(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "DynamicCast", """line 719, column 62 of dart:async/future.dart: """, stackTrace is StackTrace, true));
  if (replacement != null) {
 error = _nonNullError(replacement.error);
  stackTrace = replacement.stackTrace;
 }
- result._completeError(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "CastGeneral", """line 724, column 32 of dart:async/future.dart: """, stackTrace is StackTrace, true));
+ result._completeError(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "DynamicCast", """line 724, column 32 of dart:async/future.dart: """, stackTrace is StackTrace, true));
 }
  Object _nonNullError(Object error) => (error != null) ? error : new NullThrownError();
  typedef dynamic __t12(dynamic __u13);