Add equals and hasCode to Tween (#37793)

packages/flutter/lib/src/animation/tween.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:ui' show Color, Size, Rect;
+import 'dart:ui' show Color, Rect, Size, hashValues;
 
 import 'package:flutter/foundation.dart';
 
@@ -260,6 +260,21 @@ class Tween<T extends dynamic> extends Animatable<T> {
     return lerp(t);
   }
 
+  @override
+  int get hashCode {
+    return hashValues(begin, end);
+  }
+
+  @override
+  bool operator ==(dynamic other) {
+    if (identical(this, other))
+      return true;
+    if (other.runtimeType != runtimeType)
+      return false;
+    final Tween<T> typedOther = other;
+    return typedOther.begin == begin && typedOther.end == end;
+  }
+
   @override
   String toString() => '$runtimeType($begin \u2192 $end)';
 }

packages/flutter/test/animation/tween_test.dart

@@ -93,4 +93,18 @@ void main() {
     expect(tween.lerp(0.5), 100.0);
     expect(tween.lerp(1.0), 100.0);
   });
+
+  test('Tween equals', () {
+    final Tween<double> doubleTween1 = Tween<double>(begin: 10, end: 22);
+    final Tween<double> doubleTween2 = Tween<double>(begin: 10, end: 22);
+    final Tween<double> doubleTween3 = Tween<double>(begin: 33, end: 44);
+    final Tween<int> intTween = Tween<int>(begin: 33, end: 44);
+    final Tween<double> constantTween = ConstantTween<double>(10);
+
+    expect(doubleTween1 == doubleTween1, isTrue);
+    expect(doubleTween1 == doubleTween2, isTrue);
+    expect(doubleTween2 == doubleTween3, isFalse);
+    expect(doubleTween2 == intTween, isFalse);
+    expect(doubleTween1 == constantTween, isFalse);
+  });
 }