refactor: Modify this pointer so that it is not empty. (#3719)

* refactor: Modify this pointer so that it is not empty.

* fix: Supplementary test cases.

Author: lumburr

packages/less/src/less/functions/number.js

@@ -51,19 +51,19 @@ const minMax = function (isMin, args) {
     if (order.length == 1) {
         return order[0];
     }
-    args = order.map(function (a) { return a.toCSS(this.context); }).join(this.context.compress ? ',' : ', ');
+    args = order.map(a => { return a.toCSS(this.context); }).join(this.context.compress ? ',' : ', ');
     return new Anonymous(`${isMin ? 'min' : 'max'}(${args})`);
 };
 
 export default {
     min: function(...args) {
         try {
-            return minMax(true, args);
+            return minMax.call(this, true, args);
         } catch (e) {}
     },
     max: function(...args) {
         try {
-            return minMax(false, args);
+            return minMax.call(this, false, args);
         } catch (e) {}
     },
     convert: function (val, unit) {

packages/test-data/css/_main/functions.css

@@ -109,8 +109,10 @@
   min: 5;
   min: 1pt;
   min: 3mm;
+  min: min(1, 4ex, 2pt);
   max: 3;
   max: 5em;
+  max: max(5m, 3em);
   max-native: max(10vw, 100px);
   percentage: 20%;
   color-quoted-digit: #dda0dd;

packages/test-data/less/_main/functions.less

@@ -116,8 +116,10 @@
   min: min(6, 5);
   min: min(1pt, 3pt);
   min: min(1cm, 3mm);
+  min: min(6em, 5, 4ex, 3, 2pt, 1);
   max: max(1, 3);
   max: max(3em, 1em, 2em, 5em);
+  max: max(1px, 2, 3em, 4, 5m, 6);
   max-native: max(10vw, 100px);
   percentage: percentage((10px / 50));
   color-quoted-digit: color("#dda0dd");
@@ -135,11 +137,11 @@
 
   fade-out: fadeout(red, 5%); // support fadeOut and fadeout
   fade-in: fadein(fadeout(red, 10%), 5%);
-  fade-out-relative: fadeout(red, 5%,relative); 
+  fade-out-relative: fadeout(red, 5%,relative);
   fade-in-relative: fadein(fadeout(red, 10%, relative), 5%, relative);
-  fade-out2:  fadeout(fadeout(red, 50%), 50%); 
+  fade-out2:  fadeout(fadeout(red, 50%), 50%);
   fade-out2-relative: fadeout(fadeout(red, 50%, relative), 50%, relative);
-  
+
   hsv: hsv(5, 50%, 30%);
   hsva: hsva(3, 50%, 30%, 0.2);
 
@@ -269,7 +271,7 @@ html {
   // see: https://github.com/less/less.js/issues/3371
   @some: foo;
   l: if((iscolor(@some)), darken(@some, 10%), black);
-  
+
 
   if((false), {g: 7}); /* results in void */