Make List constructor give better error messages for non-int arguments

sdk/lib/collection/list.dart

 // Copyright (c) 2013, 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.
 
 part of dart.collection;
 
 /**
  * Abstract implementation of a list.
  *
  * `ListBase` can be used as a base class for implementing the `List` interface.
@@ skipping 226 matching lines @@
     }
     return result;
   }
 
   // Collection interface.
   void add(E element) {
     this[this.length++] = element;
   }
 
   void addAll(Iterable<E> iterable) {
+    int i = this.length;
     for (E element in iterable) {
-      this[this.length++] = element;
+      assert(this.length == i || (throw new ConcurrentModificationError(this)));

[srdjan, 2015/08/14 18:00:55]

What is the rule with COncurrentModificationErrors: should they be thrown only
in checked mode or always?

[Lasse Reichstein Nielsen, 2015/08/14 22:11:01]

There is no rule as such.
We have made them checked-mode-only in some cases (mainly on lists) because it
allows dart2js to generate better code.

+      this.length = i + 1;
+      this[i] = element;
+      i++;
     }
   }
 
   bool remove(Object element) {
     for (int i = 0; i < this.length; i++) {
       if (this[i] == element) {
         this.setRange(i, this.length - 1, this, i + 1);
         this.length -= 1;
         return true;
       }
@@ skipping 242 matching lines @@
       for (E element in iterable) {
         this[index++] = element;
       }
     }
   }
 
   Iterable<E> get reversed => new ReversedListIterable<E>(this);
 
   String toString() => IterableBase.iterableToFullString(this, '[', ']');
 }