Typing fixes to eliminate casts/dcalls

test/generated_sdk/lib/collection/set.dart

 // Copyright (c) 2014, 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.
 
 /**
  * Base implementations of [Set].
  */
 part of dart.collection;
 
 /**
@@ skipping 107 matching lines @@
     int i = 0;
     for (E element in this) result[i++] = element;
     return result;
   }
 
   Iterable map(f(E element)) =>
       new EfficientLengthMappedIterable<E, dynamic>(this, f);
 
   E get single {
     if (length > 1) throw IterableElementError.tooMany();
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) throw IterableElementError.noElement();
     E result = it.current;
     return result;
   }
 
   String toString() => IterableBase.iterableToFullString(this, '{', '}');
 
   // Copied from IterableMixin.
   // Should be inherited if we had multi-level mixins.
 
@@ skipping 67 matching lines @@
 
   Iterable<E> skip(int n) {
     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;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
     return it.current;
   }
 
   E get last {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
     E result;
     do {
       result = it.current;
     } while(it.moveNext());
     return result;
   }
 
@@ skipping 67 matching lines @@
 abstract class SetBase<E> extends SetMixin<E> {
   /**
    * Convert a `Set` to a string as `{each, element, as, string}`.
    *
    * Handles circular references where converting one of the elements
    * to a string ends up converting [set] to a string again.
    */
   static String setToString(Set set) =>
       IterableBase.iterableToFullString(set, '{', '}');
 }