Rationalize coercions

test/dart_codegen/expect/async/stream_pipe.dart

 part of dart.async;
  _runUserCode(userCode(), onSuccess(value), onError(error, StackTrace stackTrace)) {
   try {
     onSuccess(userCode());
     }
    catch (e, s) {
     AsyncError replacement = Zone.current.errorCallback(e, s);
      if (replacement == null) {
       onError(e, s);
       }
@@ skipping 84 matching lines @@
 }
  void _handleError(error, StackTrace stackTrace) {
 _stream._handleError(error, stackTrace, this);
 }
  void _handleDone() {
 _stream._handleDone(this);
 }
 }
  typedef bool _Predicate<T>(T value);
  void _addErrorWithReplacement(_EventSink sink, error, stackTrace) {
-AsyncError replacement = Zone.current.errorCallback(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "CastGeneral", """line 191, column 62 of dart:async/stream_pipe.dart: """, stackTrace is StackTrace, true));
+AsyncError replacement = Zone.current.errorCallback(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "DynamicCast", """line 191, column 62 of dart:async/stream_pipe.dart: """, stackTrace is StackTrace, true));
  if (replacement != null) {
 error = _nonNullError(replacement.error);
  stackTrace = replacement.stackTrace;
 }
- sink._addError(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "CastGeneral", """line 196, column 25 of dart:async/stream_pipe.dart: """, stackTrace is StackTrace, true));
+ sink._addError(error, DEVC$RT.cast(stackTrace, dynamic, StackTrace, "DynamicCast", """line 196, column 25 of dart:async/stream_pipe.dart: """, stackTrace is StackTrace, true));
 }
  class _WhereStream<T> extends _ForwardingStream<T, T> {final _Predicate<T> _test;
  _WhereStream(Stream<T> source, bool test(T value)) : _test = test, super(source);
  void _handleData(T inputEvent, _EventSink<T> sink) {
 bool satisfies;
  try {
 satisfies = _test(inputEvent);
 }
  catch (e, s) {
 _addErrorWithReplacement(sink, e, s);
  return;}
  if (satisfies) {
 sink._add(inputEvent);
 }
 }
 }
  typedef T _Transformation<S, T>(S value);
  class _MapStream<S, T> extends _ForwardingStream<S, T> {final _Transformation _transform;
  _MapStream(Stream<S> source, T transform(S event)) : this._transform = transform, super(source);
  void _handleData(S inputEvent, _EventSink<T> sink) {
 T outputEvent;
  try {
-outputEvent = ((__x104) => DEVC$RT.cast(__x104, dynamic, T, "CastGeneral", """line 235, column 21 of dart:async/stream_pipe.dart: """, __x104 is T, false))(_transform(inputEvent));
+outputEvent = ((__x104) => DEVC$RT.cast(__x104, dynamic, T, "CompositeCast", """line 235, column 21 of dart:async/stream_pipe.dart: """, __x104 is T, false))(_transform(inputEvent));
 }
  catch (e, s) {
 _addErrorWithReplacement(sink, e, s);
  return;}
  sink._add(outputEvent);
 }
 }
  class _ExpandStream<S, T> extends _ForwardingStream<S, T> {final _Transformation<S, Iterable<T>> _expand;
  _ExpandStream(Stream<S> source, Iterable<T> expand(S event)) : this._expand = expand, super(source);
  void _handleData(S inputEvent, _EventSink<T> sink) {
@@ skipping 114 matching lines @@
 _previous = inputEvent;
  return sink._add(inputEvent);
 }
  else {
 bool isEqual;
  try {
 if (_equals == null) {
 isEqual = (_previous == inputEvent);
 }
  else {
-isEqual = _equals(DEVC$RT.cast(_previous, Object, T, "CastGeneral", """line 426, column 29 of dart:async/stream_pipe.dart: """, _previous is T, false), inputEvent);
+isEqual = _equals(DEVC$RT.cast(_previous, Object, T, "CompositeCast", """line 426, column 29 of dart:async/stream_pipe.dart: """, _previous is T, false), inputEvent);
 }
 }
  catch (e, s) {
 _addErrorWithReplacement(sink, e, s);
  return null;
 }
  if (!isEqual) {
 sink._add(inputEvent);
  _previous = inputEvent;
 }
 }
 }
 }