add checks needed for covariant generics, and List<E>

tool/input_sdk/patch/core_patch.dart

 // Copyright (c) 2012, 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.
 
 // Patch file for dart:core classes.
 import "dart:_internal" as _symbol_dev;
 import 'dart:_interceptors';
 import 'dart:_js_helper' show patch,
                               checkInt,
                               getRuntimeType,
@@ skipping 225 matching lines @@
 
 class _ListConstructorSentinel {
   const _ListConstructorSentinel();
 }
 
 // Patch for List implementation.
 @patch
 class List<E> {
   @patch
   factory List([int length]) {
+    dynamic list;
     if (length == null) {
-      return JS('', '[]');
+      list = JS('', '[]');
+    } else {
+      // Explicit type test is necessary to guard against JavaScript conversions
+      // in unchecked mode.
+      if ((length is !int) || (length < 0)) {
+        throw new ArgumentError("Length must be a non-negative integer: $length");
+      }
+      list = JS('', 'new Array(#)', length);
+      // TODO(jmesserly): consider a fixed array subclass instead.
+      JS('void', r'#.fixed$length = Array', list);
     }
-    // Explicit type test is necessary to guard against JavaScript conversions
-    // in unchecked mode.
-    if ((length is !int) || (length < 0)) {
-      throw new ArgumentError("Length must be a non-negative integer: $length");
-    }
-    var list = JS('', 'new Array(#)', length);
-    // TODO(jmesserly): consider a fixed array subclass instead.
-    JS('void', r'#.fixed$length = Array', list);
+    // TODO(jmesserly): skip this when E is dynamic and Object.
+    JS('void', 'dart.setType(#, List\$(#))', list, E);
+    // TODO(jmesserly): compiler creates a bogus type check here.
     return list;
   }
 
   @patch
   factory List.filled(int length, E fill) {
-    List result = new JSArray<E>.fixed(length);
+    List result = new List<E>(length);
     if (length != 0 && fill != null) {
       for (int i = 0; i < result.length; i++) {
         result[i] = fill;
       }
     }
     return result;
   }
 
   @patch
   factory List.from(Iterable elements, { bool growable: true }) {
@@ skipping 184 matching lines @@
   @patch
   static bool get _isWindows => false;
 
   @patch
   static Uri get base {
     String uri = Primitives.currentUri();
     if (uri != null) return Uri.parse(uri);
     throw new UnsupportedError("'Uri.base' is not supported");
   }
 }