lib/less/js/lib/less/tree/dimension.js in less-2.5.1 vs lib/less/js/lib/less/tree/dimension.js in less-2.6.0

@@ -87,30 +87,40 @@
         return new(tree.Dimension)(value, unit);
     },
 
     compare: function (other) {
         if (other instanceof tree.Dimension) {
-            var a = this.unify(), b = other.unify(),
-                aValue = a.value, bValue = b.value;
+            var a, b,
+                aValue, bValue;
+            
+            if (this.unit.isEmpty() || other.unit.isEmpty()) {
+                a = this;
+                b = other;
+            } else {
+                a = this.unify();
+                b = other.unify();
+                if (a.unit.compare(b.unit) !== 0) {
+                    return -1;
+                }                
+            }
+            aValue = a.value;
+            bValue = b.value;
 
             if (bValue > aValue) {
                 return -1;
             } else if (bValue < aValue) {
                 return 1;
             } else {
-                if (!b.unit.isEmpty() && a.unit.compare(b.unit) !== 0) {
-                    return -1;
-                }
                 return 0;
             }
         } else {
             return -1;
         }
     },
 
     unify: function () {
-        return this.convertTo({ length: 'm', duration: 's', angle: 'rad' });
+        return this.convertTo({ length: 'px', duration: 's', angle: 'rad' });
     },
 
     convertTo: function (conversions) {
         var value = this.value, unit = this.unit.clone(),
             i, groupName, group, targetUnit, derivedConversions = {}, applyUnit;
@@ -159,9 +169,10 @@
     length: {
          'm': 1,
         'cm': 0.01,
         'mm': 0.001,
         'in': 0.0254,
+        'px': 0.0254 / 96,
         'pt': 0.0254 / 72,
         'pc': 0.0254 / 72 * 12
     },
     duration: {
         's': 1,