fix(Tree): add calc to tree variable

Author: youluna

src/tree/main.scss

@@ -160,7 +160,7 @@
         border-bottom: $tree-line;
 
         #{$tree-prefix}-right-angle {
-            bottom: -$tree-line-width;
+            bottom: calc(0px - #{$tree-line-width});
         }
     }
 
@@ -187,9 +187,9 @@
     &-right-angle {
         position: absolute;
         bottom: calc((#{$tree-switch-size} - #{$tree-switch-border-width} * 2 - #{$tree-line-width}) / 2);
-        left: calc(0px - (#{$tree-child-indent-right} + #{$tree-line-width} + #{$tree-switch-border-width}));
+        left: $tree-child-right-angle-left;
         display: block;
-        width: calc(#{$tree-child-indent-right} + #{$tree-line-width});
+        width: $tree-child-right-angle-width;
         height: calc(#{$tree-node-title-height} + #{$tree-node-padding} - #{$tree-line-width} * 2);
         border-left: $tree-line;
         border-bottom: $tree-line;

src/tree/rtl.scss

@@ -10,7 +10,7 @@
         }
         &-right-angle {
             left: auto;
-            right: calc(0px - (#{$tree-child-indent-right} + #{$tree-line-width} + #{$tree-switch-border-width}));
+            right: $tree-child-right-angle-left;
             border-left: none;
             border-right: $tree-line;
         }

src/tree/scss/variable.scss

@@ -147,8 +147,12 @@ $tree-node-disabled-background: $color-white !default;
 
 $tree-child-indent: $s-6 !default;
 $tree-node-title-height: $s-5 !default;
-$tree-child-indent-left: (#{$tree-switch-size} - #{$tree-line-width}) / 2;
-$tree-child-indent-right: #{$tree-child-indent} - #{$tree-line-width} - #{$tree-child-indent-left};
+$tree-child-indent-left: calc((#{$tree-switch-size} - #{$tree-line-width}) / 2);
+$tree-child-indent-right: calc(#{$tree-child-indent} - #{$tree-line-width} - (#{$tree-switch-size} - #{$tree-line-width}) / 2);
+$tree-child-right-angle-left: calc(0px - (#{$tree-child-indent} - (#{$tree-switch-size} - #{$tree-line-width}) / 2 + #{$tree-switch-border-width}));
+$tree-child-right-angle-width: calc(#{$tree-child-indent} - (#{$tree-switch-size} - #{$tree-line-width}) / 2);
+
+
 $tree-line: $tree-line-width $tree-line-style $tree-line-color;