Implement type checking of list literals (issue 220).

runtime/lib/growable_array.dart

Index: runtime/lib/growable_array.dart
===================================================================
--- runtime/lib/growable_array.dart	(revision 1805)
+++ runtime/lib/growable_array.dart	(working copy)
@@ -47,7 +47,7 @@
     if (start < 0 || start > this.length) {
       throw new IndexOutOfRangeException(start);
     }
-    if (this.length + length >= backingArray.length) {
+    if (this.length + length > backingArray.length) {
       grow(backingArray.length + length);
     }
     Arrays.copy(backingArray,
@@ -72,8 +72,10 @@
     return list;
   }
 
-  // The length of this growable array. It is always less than the
-  // length of the backing array.
+  // The length of this growable array. It is always less than or equal to the
+  // length of the backing array, which itself is always greater than 0, so that
+  // grow() does not have to check for a zero length backing array before
+  // doubling its size.
   int _length;
 
   GrowableObjectArray()
@@ -87,14 +89,6 @@
     backingArray = new ObjectArray<T>(capacity);
   }
 
-  GrowableObjectArray._usingArray(List<T> array) {
-    backingArray = array;
-    _length = array.length;
-    if (_length == 0) {
-      grow(4);
-    }
-  }
-
   factory GrowableObjectArray<T>.from(Collection<T> other) {
     List<T> result = new GrowableObjectArray<T>();
     result.addAll(other);
@@ -106,7 +100,7 @@
   }
 
   void set length(int new_length) {
-    if (new_length >= backingArray.length) {
+    if (new_length > backingArray.length) {
       grow(new_length);
     } else {
       for (int i = new_length; i < _length; i++) {