Revert 12494.

lib/core/date.dart

 // Copyright (c) 2011, 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.
 
 // Dart core library.
 
 /**
  * Date is the public interface to a point in time.
  *
  * It can represent time values that are at a distance of at most
  * 8,640,000,000,000,000ms (100,000,000 days) from epoch (1970-01-01 UTC). In
  * other words: [:millisecondsSinceEpoch.abs() <= 8640000000000000:].
  *
  * Also see [Stopwatch] for means to measure time-spans.
  */
-abstract class Date implements Comparable, Hashable {
+interface Date extends Comparable, Hashable default DateImplementation {
   // Weekday constants that are returned by [weekday] method:
   static const int MON = 1;
   static const int TUE = 2;
   static const int WED = 3;
   static const int THU = 4;
   static const int FRI = 5;
   static const int SAT = 6;
   static const int SUN = 7;
   static const int DAYS_IN_WEEK = 7;
 
@@ skipping 11 matching lines @@
   static const int NOV = 11;
   static const int DEC = 12;
 
   /**
    * Constructs a [Date] instance based on the individual parts. The date is
    * in the local time zone if [isUtc] is false.
    *
    * [month] and [day] are one-based. For example
    * [:new Date(1938, 1, 10)] represents the 10th of January 1938.
    */
-  factory Date(int year,
-               [int month = 1,
-                int day = 1,
-                int hour = 0,
-                int minute = 0,
-                int second = 0,
-                int millisecond = 0,
-                bool isUtc = false]) {
-    return new DateImplementation(year, month, day,
-                                  hour, minute, second,
-                                  millisecond, isUtc);
-  }
+  // TODO(floitsch): the spec allows default values in interfaces, but our
+  // tools don't yet. Eventually we want to have default values here.
+  Date(int year,
+       [int month,
+        int day,
+        int hour,
+        int minute,
+        int second,
+        int millisecond,
+        bool isUtc]);
 
   /**
    * Constructs a new [Date] instance with current date time value in the
    * local time zone.
    */
-  factory Date.now() => new DateImplementation.now();
+  Date.now();
 
   /**
    * Constructs a new [Date] instance based on [formattedString].
    */
-  factory Date.fromString(String formattedString)
-      => new DateImplementation.fromString(formattedString);
+  Date.fromString(String formattedString);
 
   /**
    * Constructs a new [Date] instance with the given [millisecondsSinceEpoch].
    * If [isUtc] is false then the date is in the local time zone.
    *
    * The constructed [Date] represents
    * 1970-01-01T00:00:00Z + [millisecondsSinceEpoch]ms in the given
    * time zone (local or UTC).
    */
   // TODO(floitsch): the spec allows default values in interfaces, but our
   // tools don't yet. Eventually we want to have default values here.
-  // TODO(lrn): Have two constructors instead of taking an optional bool.
-  factory Date.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch,
-                                          [bool isUtc = false]) {
-    return new DateImplementation.fromMillisecondsSinceEpoch(
-        millisecondsSinceEpoch, isUtc);
-  }
+  Date.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch, [bool isUtc]);
 
   /**
    * Returns true if [this] occurs at the same time as [other]. The
    * comparison is independent of whether the time is utc or in the local
    * time zone.
    */
   bool operator ==(Date other);
   /**
    * Returns true if [this] occurs before [other]. The comparison is independent
    * of whether the time is utc or in the local time zone.
@@ skipping 117 matching lines @@
   /**
    * Returns a new [Date] with the [duration] subtracted from this instance.
    */
   Date subtract(Duration duration);
 
   /**
    * Returns a [Duration] with the difference of [:this:] and [other].
    */
   Duration difference(Date other);
 }