message: refactor: tree use css var
diff: @import '../../core-css/index.scss';
  $tree: 'hi-tree' !default;
  -$fontColor: #383e47 !default;
  .#{$tree}__menu {
  - background: #fff;
  + background: use-color('white');
  width: 120px;
  box-shadow: 0 2px 8px 0 rgba(0, 0, 0, 0.1);
  border-radius: 2px;
  padding: 4px 0;
  margin: 0 0 0 4px;
  - font-size: 14px;
  + font-size: $font-size-normal;
  li.menu-item {
  list-style: none;
  @@ -30,7 +29,7 @@ $fontColor: #383e47 !default;
  }
  .#{$tree} {
  - color: $fontColor;
  + color: use-color('gray-80');
  &__searcher {
  position: relative;
  @@ -40,7 +39,7 @@ $fontColor: #383e47 !default;
  left: 24px;
  top: 34px;
  font-size: 12px;
  - color: #999;
  + color: use-color('gray-70');
  }
  }
  @@ -79,7 +78,7 @@ $fontColor: #383e47 !default;
  position: absolute;
  width: 50%;
  height: 1px;
  - background-color: #999;
  + background-color: use-color('gray-70');
  left: calc(50% - 4px);
  top: 50%;
  }
  @@ -94,7 +93,7 @@ $fontColor: #383e47 !default;
  position: absolute;
  width: 1px;
  height: calc(100% + 4px);
  - background-color: #999;
  + background-color: use-color('gray-70');
  left: 8px;
  }
  @@ -119,15 +118,15 @@ $fontColor: #383e47 !default;
  border-radius: 1px;
  .title__text {
  - height: 24px;
  - line-height: 24px;
  - font-size: 14px;
  + height: $line-height-size-large;
  + line-height: $line-height-size-large;
  + font-size: $font-size-normal;
  padding: 0 4px;
  cursor: pointer;
  &:hover {
  background: use-color('primary-20');
  - color: #383e47;
  + color: use-color('gray-80');
  }
  &--selected {
  @@ -156,23 +155,23 @@ $fontColor: #383e47 !default;
  &--disabled {
  cursor: not-allowed;
  - color: #ccc;
  + color: use-color('gray-50');
  .title__text {
  cursor: not-allowed;
  &:hover {
  - background: #fff;
  - color: #ccc;
  + background: use-color('white');
  + color: use-color('gray-50');
  }
  &--selected {
  - background: #fff;
  - color: #ccc;
  + background: use-color('white');
  + color: use-color('gray-50');
  &:hover {
  - background: #fff;
  - color: #ccc;
  + background: use-color('white');
  + color: use-color('gray-50');
  }
  }
  }
  @@ -184,7 +183,7 @@ $fontColor: #383e47 !default;
  &--in {
  background: use-color('primary');
  - color: #fff;
  + color: use-color('white');
  }
  &--down {
  