Fixed extend leaking through nested parent selector. less#2586

lib/less/tree/ruleset.js

@@ -605,7 +605,7 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
         if (addPath.length > 0) {
             // /deep/ is a combinator that is valid without anything in front of it
             // so if the & does not have a combinator that is "" or " " then
-            // and there is a combinator on the parent, then grab that.
+            // and there is a combinator o  n the parent, then grab that.
             // this also allows + a { & .b { .a & { ... though not sure why you would want to do that
             var combinator = replacedElement.combinator, parentEl = addPath[0].elements[0];
             if (combinator.emptyOrWhitespace && !parentEl.combinator.emptyOrWhitespace) {
@@ -623,7 +623,11 @@ Ruleset.prototype.joinSelector = function (paths, context, selector) {
 
         //put together the parent selectors after the join (e.g. the rest of the parent)
         if (addPath.length > 1) {
-            newSelectorPath = newSelectorPath.concat(addPath.slice(1));
+            var restOfPath = addPath.slice(1);
+            restOfPath = restOfPath.map(function (selector) {
+                return selector.createDerived(selector.elements, []);
+            });
+            newSelectorPath = newSelectorPath.concat(restOfPath);
         }
         return newSelectorPath;
     }

test/css/extend-selector.css

@@ -78,3 +78,10 @@ div.ext7,
 .footer .footer-nav:before {
   background: blue;
 }
+.issue-2586-bordered,
+.issue-2586-somepage .content {
+  border: solid 1px black;
+}
+.issue-2586-somepage .content > span {
+  margin-bottom: 10px;
+}

test/less/extend-selector.less

@@ -96,4 +96,15 @@ div.ext5,
   .footer-nav {
     &:extend( .header .header-nav all );
   }
-}
+}
+
+.issue-2586-bordered {
+    border: solid 1px black;
+}
+.issue-2586-somepage {
+    .content:extend(.issue-2586-bordered) {
+        &>span {
+            margin-bottom: 10px;
+        }
+    }
+}