fix tween custom easing property

cocos/tween/export-api.ts

@@ -1,3 +1,4 @@
+/* eslint-disable @typescript-eslint/ban-types */
 /*
  Copyright (c) 2020 Xiamen Yaji Software Co., Ltd.
 
@@ -35,7 +36,7 @@
   * 内置缓动函数的字符串值定义。
   */
 export type TweenEasing =
-'linear'    | 'smooth'     | 'fade'         |
+'linear'    | 'smooth'     | 'fade'         | 'constant'     |
 'quadIn'    | 'quadOut'    | 'quadInOut'    | 'quadOutIn'    |
 'cubicIn'   | 'cubicOut'   | 'cubicInOut'   | 'cubicOutIn'   |
 'quartIn'   | 'quartOut'   | 'quartInOut'   | 'quartOutIn'   |

cocos/tween/set-action.ts

@@ -36,6 +36,7 @@ export class SetAction extends ActionInstant {
     constructor (props?: any) {
         super();
         this._props = {};
+        // eslint-disable-next-line @typescript-eslint/no-unused-expressions
         props !== undefined && this.init(props);
     }
 

cocos/tween/tween-action.ts

@@ -139,21 +139,21 @@ export class TweenAction extends ActionInterval {
             let value = props[name];
             if (value == null || typeof value === 'string' || typeof value === 'function') continue;
             // property may have custom easing or progress function
-            let easing: any; let progress: any;
+            let customEasing: any; let progress: any;
             if (value.value !== undefined && (value.easing || value.progress)) {
                 if (typeof value.easing === 'string') {
-                    easing = easing[value.easing];
-                    if (!easing) warnID(1031, value.easing);
+                    customEasing = easing[value.easing];
+                    if (!customEasing) warnID(1031, value.easing);
                 } else {
-                    easing = value.easing;
+                    customEasing = value.easing;
                 }
                 progress = value.progress;
                 value = value.value;
             }
 
             const prop = Object.create(null);
             prop.value = value;
-            prop.easing = easing;
+            prop.easing = customEasing;
             prop.progress = progress;
             this._props[name] = prop;
         }