Rationalize coercions

test/dart_codegen/expect/collection/linked_list.dart

 part of dart.collection;
  class LinkedList<E extends LinkedListEntry<E>> extends IterableBase<E> implements _LinkedListLink {int _modificationCount = 0;
  int _length = 0;
  _LinkedListLink _next;
  _LinkedListLink _previous;
  LinkedList() {
   _next = _previous = this;
   }
  void addFirst(E entry) {
   _insertAfter(this, entry);
   }
  void add(E entry) {
   _insertAfter(_previous, entry);
   }
  void addAll(Iterable<E> entries) {
   entries.forEach(((__x10) => DEVC$RT.wrap((void f(dynamic __u5)) {
     void c(dynamic x0) => f(x0);
      return f == null ? null : c;
     }
   , __x10, __t8, DEVC$RT.type((__t6<E> _) {
     }
-  ), "WrapLiteral", """line 65, column 21 of dart:collection/linked_list.dart: """, __x10 is __t6<E>))((entry) => _insertAfter(_previous, DEVC$RT.cast(entry, dynamic, E, "CastGeneral", """line 65, column 56 of dart:collection/linked_list.dart: """, entry is E, false))));
+  ), "WrapLiteral", """line 65, column 21 of dart:collection/linked_list.dart: """, __x10 is __t6<E>))((entry) => _insertAfter(_previous, DEVC$RT.cast(entry, dynamic, E, "CompositeCast", """line 65, column 56 of dart:collection/linked_list.dart: """, entry is E, false))));
   }
  bool remove(E entry) {
   if (entry._list != this) return false;
    _unlink(entry);
    return true;
   }
  Iterator<E> get iterator => new _LinkedListIterator<E>(this);
  int get length => _length;
  void clear() {
   _modificationCount++;
    _LinkedListLink next = _next;
    while (!identical(next, this)) {
-    E entry = DEVC$RT.cast(next, _LinkedListLink, E, "CastGeneral", """line 93, column 17 of dart:collection/linked_list.dart: """, next is E, false);
+    E entry = DEVC$RT.cast(next, _LinkedListLink, E, "CompositeCast", """line 93, column 17 of dart:collection/linked_list.dart: """, next is E, false);
      next = entry._next;
      entry._next = entry._previous = entry._list = null;
     }
    _next = _previous = this;
    _length = 0;
   }
  E get first {
   if (identical(_next, this)) {
     throw new StateError('No such element');
     }
-   return DEVC$RT.cast(_next, _LinkedListLink, E, "CastGeneral", """line 105, column 12 of dart:collection/linked_list.dart: """, _next is E, false);
+   return DEVC$RT.cast(_next, _LinkedListLink, E, "CompositeCast", """line 105, column 12 of dart:collection/linked_list.dart: """, _next is E, false);
   }
  E get last {
   if (identical(_previous, this)) {
     throw new StateError('No such element');
     }
-   return DEVC$RT.cast(_previous, _LinkedListLink, E, "CastGeneral", """line 112, column 12 of dart:collection/linked_list.dart: """, _previous is E, false);
+   return DEVC$RT.cast(_previous, _LinkedListLink, E, "CompositeCast", """line 112, column 12 of dart:collection/linked_list.dart: """, _previous is E, false);
   }
  E get single {
   if (identical(_previous, this)) {
     throw new StateError('No such element');
     }
    if (!identical(_previous, _next)) {
     throw new StateError('Too many elements');
     }
-   return DEVC$RT.cast(_next, _LinkedListLink, E, "CastGeneral", """line 122, column 12 of dart:collection/linked_list.dart: """, _next is E, false);
+   return DEVC$RT.cast(_next, _LinkedListLink, E, "CompositeCast", """line 122, column 12 of dart:collection/linked_list.dart: """, _next is E, false);
   }
  void forEach(void action(E entry)) {
   int modificationCount = _modificationCount;
    _LinkedListLink current = _next;
    while (!identical(current, this)) {
-    action(DEVC$RT.cast(current, _LinkedListLink, E, "CastGeneral", """line 134, column 14 of dart:collection/linked_list.dart: """, current is E, false));
+    action(DEVC$RT.cast(current, _LinkedListLink, E, "CompositeCast", """line 134, column 14 of dart:collection/linked_list.dart: """, current is E, false));
      if (modificationCount != _modificationCount) {
       throw new ConcurrentModificationError(this);
       }
      current = current._next;
     }
   }
  bool get isEmpty => _length == 0;
  void _insertAfter(_LinkedListLink entry, E newEntry) {
   if (newEntry.list != null) {
     throw new StateError('LinkedListEntry is already in a LinkedList');
@@ skipping 23 matching lines @@
  _LinkedListIterator(LinkedList<E> list) : _list = list, _modificationCount = list._modificationCount, _next = list._next;
  E get current => _current;
  bool moveNext() {
 if (identical(_next, _list)) {
   _current = null;
    return false;
   }
  if (_modificationCount != _list._modificationCount) {
   throw new ConcurrentModificationError(this);
   }
- _current = DEVC$RT.cast(_next, _LinkedListLink, E, "CastGeneral", """line 192, column 16 of dart:collection/linked_list.dart: """, _next is E, false);
+ _current = DEVC$RT.cast(_next, _LinkedListLink, E, "CompositeCast", """line 192, column 16 of dart:collection/linked_list.dart: """, _next is E, false);
  _next = _next._next;
  return true;
 }
 }
  class _LinkedListLink {_LinkedListLink _next;
  _LinkedListLink _previous;
 }
  abstract class LinkedListEntry<E extends LinkedListEntry<E>> implements _LinkedListLink {LinkedList<E> _list;
  _LinkedListLink _next;
  _LinkedListLink _previous;
  LinkedList<E> get list => _list;
  void unlink() {
 _list._unlink(this);
 }
  E get next {
 if (identical(_next, _list)) return null;
- E result = DEVC$RT.cast(_next, _LinkedListLink, E, "CastGeneral", """line 249, column 16 of dart:collection/linked_list.dart: """, _next is E, false);
+ E result = DEVC$RT.cast(_next, _LinkedListLink, E, "CompositeCast", """line 249, column 16 of dart:collection/linked_list.dart: """, _next is E, false);
  return result;
 }
  E get previous {
 if (identical(_previous, _list)) return null;
  return DEVC$RT.cast(_previous, _LinkedListLink, E, "CastUser", """line 261, column 12 of dart:collection/linked_list.dart: """, _previous is E, false);
 }
  void insertAfter(E entry) {
 _list._insertAfter(this, entry);
 }
  void insertBefore(E entry) {
 _list._insertAfter(_previous, entry);
 }
 }
  typedef void __t6<E>(E __u7);
  typedef void __t8(dynamic __u9);