Rationalize coercions

test/dart_codegen/expect/collection/iterable.dart

 part of dart.collection;
  abstract class IterableMixin<E> implements Iterable<E> {Iterable map(f(E element)) => new MappedIterable<E, dynamic>(this, f);
  Iterable<E> where(bool f(E element)) => new WhereIterable<E>(this, f);
  Iterable expand(Iterable f(E element)) => new ExpandIterable<E, dynamic>(this, f);
  bool contains(Object element) {
   for (E e in this) {
     if (e == element) return true;
     }
    return false;
   }
@@ skipping 70 matching lines @@
   return new SkipIterable<E>(this, n);
   }
  Iterable<E> skipWhile(bool test(E value)) {
   return new SkipWhileIterable<E>(this, test);
   }
  E get first {
   Iterator it = iterator;
    if (!it.moveNext()) {
     throw IterableElementError.noElement();
     }
-   return DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 127, column 12 of dart:collection/iterable.dart: """, it.current is E, false);
+   return DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 127, column 12 of dart:collection/iterable.dart: """, it.current is E, false);
   }
  E get last {
   Iterator it = iterator;
    if (!it.moveNext()) {
     throw IterableElementError.noElement();
     }
    E result;
    do {
-    result = DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 137, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
+    result = DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 137, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
     }
    while (it.moveNext()); return result;
   }
  E get single {
   Iterator it = iterator;
    if (!it.moveNext()) throw IterableElementError.noElement();
-   E result = DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 145, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
+   E result = DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 145, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
    if (it.moveNext()) throw IterableElementError.tooMany();
    return result;
   }
  E firstWhere(bool test(E value), {
   E orElse()}
 ) {
   for (E element in this) {
     if (test(element)) return element;
     }
    if (orElse != null) return orElse();
@@ skipping 124 matching lines @@
 return new SkipIterable<E>(this, n);
 }
  Iterable<E> skipWhile(bool test(E value)) {
 return new SkipWhileIterable<E>(this, test);
 }
  E get first {
 Iterator it = iterator;
  if (!it.moveNext()) {
   throw IterableElementError.noElement();
   }
- return DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 323, column 12 of dart:collection/iterable.dart: """, it.current is E, false);
+ return DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 323, column 12 of dart:collection/iterable.dart: """, it.current is E, false);
 }
  E get last {
 Iterator it = iterator;
  if (!it.moveNext()) {
   throw IterableElementError.noElement();
   }
  E result;
  do {
-  result = DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 333, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
+  result = DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 333, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
   }
  while (it.moveNext()); return result;
 }
  E get single {
 Iterator it = iterator;
  if (!it.moveNext()) throw IterableElementError.noElement();
- E result = DEVC$RT.cast(it.current, dynamic, E, "CastGeneral", """line 341, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
+ E result = DEVC$RT.cast(it.current, dynamic, E, "CompositeCast", """line 341, column 16 of dart:collection/iterable.dart: """, it.current is E, false);
  if (it.moveNext()) throw IterableElementError.tooMany();
  return result;
 }
  E firstWhere(bool test(E value), {
 E orElse()}
 ) {
 for (E element in this) {
   if (test(element)) return element;
   }
  if (orElse != null) return orElse();
@@ skipping 93 matching lines @@
   if (!it.moveNext()) return; String next = "${it.current}";
    parts.add(next);
    length += next.length + OVERHEAD;
    count++;
   }
  String penultimateString;
  String ultimateString;
  var penultimate = null;
  var ultimate = null;
  if (!it.moveNext()) {
-  if (count <= HEAD_COUNT + TAIL_COUNT) return; ultimateString = ((__x0) => DEVC$RT.cast(__x0, dynamic, String, "CastGeneral", """line 530, column 24 of dart:collection/iterable.dart: """, __x0 is String, true))(parts.removeLast());
-   penultimateString = ((__x1) => DEVC$RT.cast(__x1, dynamic, String, "CastGeneral", """line 531, column 27 of dart:collection/iterable.dart: """, __x1 is String, true))(parts.removeLast());
+  if (count <= HEAD_COUNT + TAIL_COUNT) return; ultimateString = ((__x0) => DEVC$RT.cast(__x0, dynamic, String, "DynamicCast", """line 530, column 24 of dart:collection/iterable.dart: """, __x0 is String, true))(parts.removeLast());
+   penultimateString = ((__x1) => DEVC$RT.cast(__x1, dynamic, String, "DynamicCast", """line 531, column 27 of dart:collection/iterable.dart: """, __x1 is String, true))(parts.removeLast());
   }
  else {
   penultimate = it.current;
    count++;
    if (!it.moveNext()) {
     if (count <= HEAD_COUNT + 1) {
       parts.add("$penultimate");
        return;}
      ultimateString = "$penultimate";
-     penultimateString = ((__x2) => DEVC$RT.cast(__x2, dynamic, String, "CastGeneral", """line 541, column 29 of dart:collection/iterable.dart: """, __x2 is String, true))(parts.removeLast());
+     penultimateString = ((__x2) => DEVC$RT.cast(__x2, dynamic, String, "DynamicCast", """line 541, column 29 of dart:collection/iterable.dart: """, __x2 is String, true))(parts.removeLast());
      length += ultimateString.length + OVERHEAD;
     }
    else {
     ultimate = it.current;
      count++;
      assert (count < MAX_COUNT); while (it.moveNext()) {
       penultimate = ultimate;
        ultimate = it.current;
        count++;
        if (count > MAX_COUNT) {
         while (length > LENGTH_LIMIT - ELLIPSIS_SIZE - OVERHEAD && count > HEAD_COUNT) {
-          length -= ((__x3) => DEVC$RT.cast(__x3, dynamic, int, "CastGeneral", """line 562, column 25 of dart:collection/iterable.dart: """, __x3 is int, true))(parts.removeLast().length + OVERHEAD);
+          length -= ((__x3) => DEVC$RT.cast(__x3, dynamic, int, "DynamicCast", """line 562, column 25 of dart:collection/iterable.dart: """, __x3 is int, true))(parts.removeLast().length + OVERHEAD);
            count--;
           }
          parts.add("...");
          return;}
       }
      penultimateString = "$penultimate";
      ultimateString = "$ultimate";
      length += ultimateString.length + penultimateString.length + 2 * OVERHEAD;
     }
   }
  String elision = null;
  if (count > parts.length + TAIL_COUNT) {
   elision = "...";
    length += ELLIPSIS_SIZE + OVERHEAD;
   }
  while (length > LENGTH_LIMIT && parts.length > HEAD_COUNT) {
-  length -= ((__x4) => DEVC$RT.cast(__x4, dynamic, int, "CastGeneral", """line 588, column 17 of dart:collection/iterable.dart: """, __x4 is int, true))(parts.removeLast().length + OVERHEAD);
+  length -= ((__x4) => DEVC$RT.cast(__x4, dynamic, int, "DynamicCast", """line 588, column 17 of dart:collection/iterable.dart: """, __x4 is int, true))(parts.removeLast().length + OVERHEAD);
    if (elision == null) {
     elision = "...";
      length += ELLIPSIS_SIZE + OVERHEAD;
     }
   }
  if (elision != null) {
   parts.add(elision);
   }
  parts.add(penultimateString);
  parts.add(ultimateString);
 }
 }